KWAME NKRUMAH UNIVERSITY OF SCIENCE AND
TECHNOLOGY
COLLEGE OF AGRICULTURE AND NATURAL RESOURCES
DEPARTMENT OF FISHERIES AN...
ABSTRACT
The Korle Lagoon in Accra, Ghana, has become one of the most polluted water bodies on
earth. Different aquatic or...
ACKNOWLEDGMENT
I thank the most high God for the strength and calm through the perplexing times during my
study.
I wish to...
TABLE OF CONTENT
CONTENT PAGE
ABSTRACT.......................................................................................
3.1. Description of the study area ......................................................................................2...
LIST OF TABLES
TABLE PAGE
Table 4.1 Heavy metal concentration (μg/g ww) concentration in the sediment
from the Korle lagoo...
LISTS OF PLATES
PLATES PAGE
Plate 1 Pteroscion peli ……………………………………………………………..
29
Plate 2 Seriola dumerili …………………………………………...
Plate 11 Sediment being air dried ………………………………………………… 34
Plate 12 some containers containing digested sample …………………………......
CHAPTER ONE
1.0. INTRODUCTION
The coastline of Ghana is abundantly endowed with many lagoonal resources and is of
major si...
of the lagoon with heavy metal is the local and crude methods of recycling electronic
waste (e-waste) to retrieve its meta...
The Korle Lagoon in Accra, Ghana, has become one of the most polluted water bodies on
earth. It is the principal outlet th...
surfaces (Begum, et al., 2009). Bio magnification can result in fish at the top of food chain
containing hundreds more hea...
Based on the above reasons the objectives of this study were:
• To assess the concentration of zinc, lead, copper and cadm...
CHAPTER 2
2.0. LITERATURE REVIEW
2.1. Global Water Pollution
Every day, 2 million tons of sewage, industrial and agricultu...
development including rapid urbanization and industrial growth, many unplanned
interventions have been made in water bodie...
2.1.1. Environmental Aquatic Pollution
The pressure of increasing population, growth of industries, urbanization, energy
i...
selenium (Se), vanadium (V), oils and grease, pesticides, etc are very harmful, toxic and
poisonous even in ppb (parts per...
Higher concentrations of heavy metals (such as Cd, Pb, Cu and Zn) in the sediment of an
estuary concur with the pattern of...
2.2.2. Sediments and Heavy Metals in Estuaries
Estuaries are important zones of sediment transfer between fluvial and mari...
pose a potential threat to the aquatic environment. Resuspension of contaminated bed
sediments caused by strong tidal curr...
concentration of copper and hardness, alkalinity, salinity, pH and concentration of
bicarbonate, bicarbonate sulphide, pho...
Lead is a micro element naturally present in trace amounts in all biological materials,
thus, in soil, water, plants and a...
levels with increased exposure concentration, and there are indications that lead is present
on the egg surface but not ac...
higher concentration, this process appears to breakdown leading to an influx of zinc also
according to (NAS, 1979), gills ...
µg cadmium l-1), cadmium inhibits ion transport systems and induces
metallothionein synthesis (< 1 &micro;g cadmium ...
deficiency causes anaemia and retardation of growth and development (McCluggage,
1991). Calcium is a very vital element in...
cadmium pneumonitis, resulting from inhaled dusts and fumes. It is characterized by
chest pain, cough with foamy and blood...
quotient (IQ) (Udedi, 2003). Its absorption in the body is enhanced by Ca and Zn
deficiencies. Acute and chronic effects o...
Natural waters therefore become the key environmental component that suffers massively
from such pollution and this is the...
already inadequate urban facilities including the housing and basic sanitation amenities.
This situation has led to the de...
Other sources of heavy metals into the Lagoon can be traced to effluent discharged from
domestic and industrial activities...
Presently however, beach seining and other fishing activities take place at the estuary of
the lagoon and within 500 m off...
2.7.1. Seriola spp
The genus Seriola is of the family Carangidae, order Perciformes, and class
Actinopterygii. Three speci...
fisheries worldwide. This species is a spring-summer spawner, with a multiple group
synchronous oocyte development and, li...
CHAPTER THREE
3.0. METHODOLOGY
3.1. Description of the study area
The Korle lagoon is a coastal wetland that joins the Gul...
3.2. Sample collection
Fish samples were obtained from fishers (Plate 3, 4) at the estuary of the Lagoon and
transported o...
Plate 3 Beach Seining at the Korle lagoon estuary Plate 4 Obtaining samples from fishers
Plate 5 Some Pteroscion peli obta...
releasing the instrument to the bottom the boat owner dived to trip the over lapping
spring loaded with scoop, the depth o...
Plate 8 Sampling point (B)
Sampling point (C) is the area that receives fresh water frequently than sea water and also
joi...
3.3.1. Sample Digestion
Fish and sediments samples acquired were digested at the same time. Sample digestion is
the remova...
temperature. The volume was made up with distilled water and filtered with a Whatmann
filter paper. The filtrate was then ...
Plate 12 Some containers containing digested samples
3.3.3. Determination of heavy metal concentration
Heavy metal analysi...
All samples were accompanied by blanks at a rate of one blank per 20 samples. Replicate
analyses were conducted for all th...
CHAPTER FOUR
4.0. RESULTS
4.1. Heavy metal concentrations in Sediment Samples
Copper concentration s were consistently flu...
Table 4.1. Copper (Cu), Lead (Pb), Zinc (Zn) and Cadmium (Cd) concentration (μg/g
ww) in the sediment from the Korle lagoo...
μg/g ww for both months respectively. Between October 2011 and November 2011
concentration dropped from 14.09 μg/g ww to 1...
Concentration trend observed in Seriola dumerili varied to that of Pteroscion peli.
Copper (Cu) concentration increased fr...
Month n Cu Pb Cd Zn
October 8 3.38 ± 0.76 2.90 ± 2.0 1.42 ± 0.31 13.45 ± 6.26
November 8 3.36 ± 0.32 3.01 ± 2.07 1.35 ± 0....
Heavy metal concentration in relation to size of Pteroscion peli increased with increase in
size for October 2011 and Dece...
Heavy metal concentration in October 2012 and November 2012 increased with increase
in size as large size Seriola dumerili...
4.5. Physicochemical Parameters of the Korle lagoon
Physicochemical parameters for the four months (October 2011 to Januar...
CHAPTER FIVE
5.0. DISCUSSION
5.1. Heavy Metal Concentration in Sediments
Heavy metals in sediments may represent a combina...
disturbed. The low copper levels recorded could be due to the regular mixing of the water
column due to its fluvial flow r...
below the ERM, which implies that fishes at the estuary could occasionally be affected
by Cadmium.
5.2. Heavy Metal effect...
compounds may rapidly be taken up by fish and rapidly eliminated after the end of the
exposure (WHO, 1995).
Cadmium bio ac...
CHAPTER SIX
6.0. CONCLUSIONS
Heavy metal levels in fishes sampled were less than what was found in the sediment
samples. H...
Moreover, Secondary feeders like filter feeders (Mugil cephalus) and other herbivores
fishes from the Korle lagoon estuary...
REFERENCES
Aanstoos , T. A., Nichols, S. P., Torres ,V. M. (1998). IEEE Transactions on Components,
Hybrids, and Manufactu...
Begum, A., Harikrishina, S. and Khan, I. ( 2009). Analysis of heavy metals in water, sediments
and fish samples of Madival...
European Union, (2002). Heavy Metals in Wastes, EuropeanCommission on Environment
(http://ec.europa.eu/environment/waste/ ...
Grimwood M. J. and Dixon, E. (1997). Assessment of risks posed by list II metals to Sensitive
Marine Areas (SMAs) and adeq...
Kudesia, V. P. (2002). “Water Pollution—Toxicity of Metals”, Pragati Prakashan, Meerut
(2002) (India).
Lenntech Water Trea...
Micale, V., Genovese, L., Greco, S., Perdichizzi, F. (1993). Aspects of the reproductive biology
of the amberjack, Seriola...
Ridgway, J. and Shimmield, G. (2002). Estuaries as Repositories of Historical Contamination
and their Impact on Shelf Seas...
Woo, P. T. K., Sin Y. M. and Wong M. K. (1993). Environ. Biol. of Fishes, 37: 67-74.
WHO, (1992). Environmental health Cri...
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Heavy Metal Concentration in the Sediments and Flesh of Boe Drum and Greater Amberjack from the Korle lagoon estuary,Accra - Ghana

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Heavy Metal Concentration in the Sediments and Flesh of Boe Drum and Greater Amberjack from the Korle lagoon estuary,Accra - Ghana

  1. 1. KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY COLLEGE OF AGRICULTURE AND NATURAL RESOURCES DEPARTMENT OF FISHERIES AND WATERSHED MANAGEMENT HEAVY METAL CONCENTRATION IN THE SEDIMENTS AND FLESH OF BOE DRUM (Pteroscion peli) AND GREATER AMBERJACK (Seriola dumerili) FROM THE KORLE LAGOON ESTUARY, ACCRA, GHANA. A THESIS SUBMITTED TO THE FACULTY OF RENEWABLE NATURAL RESOURCES IN PARTIAL FULFILMENT OF THE REQUIRMENTS FOR THE AWARD OF BACHELOR OF SCIENCE DEGREE IN NATURAL RESOURCE MANAGEMENT ABOAGYE HACKMAN RICHARD MAY 2012 i
  2. 2. ABSTRACT The Korle Lagoon in Accra, Ghana, has become one of the most polluted water bodies on earth. Different aquatic organisms often respond to external contamination in different ways, where the quantity and form of the element in water, sediment, or food will determine the degree of accumulation. The concentration of copper (Cu), Lead (Pb), Zinc (Zn), and Cadmium (Cd) in the flesh of Pteroscion peli and Seriola dumerili were assessed from October 2011 to January 2012. Eight fishes were sampled for each fish species. Sediments were taken from three different sites on a monthly basis at the estuary of the Korle lagoon. Samples collected were digested with a di-acid of the ratio 9; 4 of nitric acid and perchloric acid respectively. Heavy metal was determined using the Atomic Adsorption Spectrophometer (AAS). Heavy metal concentrations in sediment were below the National Oceanic and Atmospheric Administration (NOAA) Sediment Quality Guideline for Estuaries over the period and ranked in the order: Pb> Zn> Cu> Cd. The result of this research showed that heavy metals were continuously deposited and removed from sediments into the water column of the Korle lagoon estuary. Also the study indicated that the levels of metal in the flesh of Seriola dumerili and Pteroscion peli were low for, copper and zinc but higher for Lead and Cadmium as compared to the World Health Organization Standard (2005). Heavy metal concentrations in the flesh of S. Dumerili and P. peli in relation to size revealed that both sizes accumulated higher lead and cadmium concentrations and lower Zinc and Copper concentration. The present study showed that consumption of fish from the Korle Lagoon estuary should be prohibited and should be discouraged because of the high levels of Pb and Cd in the flesh of Seriola dumerili and Pteroscion peli in both small and large sizes. ii
  3. 3. ACKNOWLEDGMENT I thank the most high God for the strength and calm through the perplexing times during my study. I wish to express my deepest appreciation to my supervisor, Dr Nelson W Agbo, for his invaluable comments and excellent supervision. I must also thank him for the cordial relations showed towards me, which was very helpful and very much cherished. My thanks also goes to Mr Kwasi Adu Obirikorang for being my second supervisor, assisting me on field, laboratory and in putting this together. I wish to thank Mr Napoleon Jackson and Mr Douglas for their assistance in the laboratory. I thank my mum, Miss Monica Hackman so much for her inspiration, motivation and financial assistance in putting this thesis together. My thanks also go to the entire membership of Christ Apostolic Church, Odorkor Official Town Assembly for their prayers into this dissertation. My sincere thanks also go to the following persons Mary Abena Yamoah, Enoch Adjei Mensah and Solomon Antwi for their diverse assistance in the preparation of this dissertation. My special thanks go to Mr. Daniel, Maame Awotwe, Sister Violet and all fishers of the Korle Lagoon Estuary. iii
  4. 4. TABLE OF CONTENT CONTENT PAGE ABSTRACT.............................................................................................................................ii ACKNOWLEDGEMENT.....................................................................................................iii TABLE OF CONTENT…………………………………………………………………………………….iv LIST OF TABLES.................................................................................................................vii LIST OF PLATES................................................................................................................viii LIST OF FIGURES................................................................................................................ix 1.0. INTRODUCTION.....................................................................................................1 1.1. Justification....................................................................................................................2 1.2. OBJECTIVES....................................................................................................................4 2.0. LITERATURE REVIEW..............................................................................................6 2.1. Global Water Pollution...................................................................................................6 2.1.1. Environmental Aquatic Pollution...............................................................................................8 2.2. Heavy Metals.................................................................................................................9 2.2.1. Source of Heavy Metals...........................................................................................................10 2.2.2. Sediments and Heavy Metals in Estuaries...............................................................................11 2.3. Some Common Heavy Metals.......................................................................................12 2.3.1. Copper......................................................................................................................................12 2.3.2. Lead..........................................................................................................................................13 2.3.3. Zinc...........................................................................................................................................15 2.3.4. Cadmium .................................................................................................................................16 2.4. Bio-Importance of Heavy Metals to Humans................................................................17 2.4.1. Effect of bioaccumulation on humans.....................................................................................18 2.5. Lagoon Pollution in Ghana............................................................................................20 2.6. State of the Korle lagoon..............................................................................................21 2.6.1. Heavy metal sources to the lagoon.........................................................................................22 2.6.2. Effect of Korle lagoon pollution...............................................................................................23 2.6.3. Activities at the estuary...........................................................................................................23 2.7. Fish Species..................................................................................................................24 2.7.1. Seriola spp................................................................................................................................25 2.7.2. Pteroscion peli.........................................................................................................................26 3.0. METHODOLOGY...................................................................................................27 iv
  5. 5. 3.1. Description of the study area ......................................................................................27 3.2. Sample collection.........................................................................................................28 3.3. Heavy Metal Analysis ..................................................................................................31 3.3.1. Sample Digestion.....................................................................................................................32 3.3.2. Sediment digestion..................................................................................................................33 3.3.3. Determination of heavy metal concentration.........................................................................34 3.3.4. Measurement of Physicochemical Water Parameters............................................................35 4.0. RESULTS...............................................................................................................36 4.1. Heavy metal concentrations in Sediment Samples.......................................................36 4.2. Heavy metal concentrations in Pteroscion peli.............................................................37 4.3. Heavy metal concentration in Seriola dumerili.............................................................38 4.4. Heavy metals in the flesh of P. peli and the S. dumerili in relation to sizes...................40 4.4.1. Pteroscion peli ........................................................................................................................40 4.4.2. Seriola dumerili........................................................................................................................41 4.5. Physicochemical Parameters of the Korle lagoon ........................................................43 5.0. DISCUSSION.........................................................................................................44 5.1. Heavy Metal Concentration in Sediments.....................................................................44 5.2. Heavy Metal effect in fish species................................................................................46 5.3. Variation in Metal Concentrations in Relation to Body Size..........................................47 6.0. CONCLUSIONS.....................................................................................................48 6.1. RECOMMENDATIONS...................................................................................................48 REFERENCES..............................................................................................................50 v
  6. 6. LIST OF TABLES TABLE PAGE Table 4.1 Heavy metal concentration (μg/g ww) concentration in the sediment from the Korle lagoon estuary.............................................................. 37 Table 4.2 Heavy metal concentration (μg/g ww) in the flesh of Pteroscion peli from the Korle lagoon estuary............................................................... 38 Table 4.3 Heavy metal concentration (μg/g ww) in the flesh of Seriola dumerili from the Korle lagoon estuary....... ...................................................... 40 Table 4.4 Physiochemical parameters ......................................................................43 vi
  7. 7. LISTS OF PLATES PLATES PAGE Plate 1 Pteroscion peli …………………………………………………………….. 29 Plate 2 Seriola dumerili ………………………………………………………….... 29 Plate 3 Beach seining at the Korle lagoon estuary ……………………………..... 30 Plate 4 Obtaining samples from fishers ………………………………………….. 30 Plate 5 Some Pteroscion peli obtained …………………………………………… 30 Plate 6 Some Seriola dumerili obtained ………………………………………….. 30 Plate 7 Sampling point (A) ……………………………………………………….. 31 Plate 8 Sampling point (B) ……………………………………………………….. 32 Plate 9 Sampling point (C) ……………………………………………………….. 32 Plate 10 Total length of Seriola dumerili being taken …………………………… 33 vii
  8. 8. Plate 11 Sediment being air dried ………………………………………………… 34 Plate 12 some containers containing digested sample …………………………... 35 Plate 13 Water quality parameter being taken insutu ………………………... 36 LISTS OF FIGURES FIGURES PAGE Fig 3.1 Study area and its environs..............................................................................28 Fig 4.1 Variation in Cu, Pd, Cd and Zn concentration in the flesh of Pteroscion peli from the Korle lagoon estuary.........................................................................41 Fig 4.2 Variation in Cu, Pb, Cd and Zn concentration in the flesh of Seriola dumerili from the Korle lagoon estuary.........................................................................42 viii
  9. 9. CHAPTER ONE 1.0. INTRODUCTION The coastline of Ghana is abundantly endowed with many lagoonal resources and is of major significance for domestic, spiritual and economic activities. In recent times, the coast of Ghana is encountering serious environmental challenges. These problems are in response to rapid demographic changes and growth of industrial activities along the coast. This development has coincided with the establishment of human settlements which lack credible sanitary infrastructure to give adequate support to waste disposal (Karikari, 2005). This has led to degradation of water quality leading to loss of the ecological integrity of most lagoons. Korle lagoon is one such lagoon in Accra, Ghana which used to support a vibrant artisanal fishery with attendant socio-economic activities for the communities living around the lagoon up to the 1980’s when uncontrolled pollution from domestic and industrial sources severely impacted on the Lagoon’s fishery and nearly led to its collapse. According to Entsua-Mensah et al. (2004), the Korle Lagoon estuary still supports artisanal fisheries which play an important role in the economy of some coastal inhabitants, especially during the off-season for marine fishing. The Lagoon also serves as breeding grounds for some fish species. Heavy metals are intrinsic, natural constituents of our environment. They are generally present in small amounts in natural aquatic environments. Apart from the natural sources, several anthropogenic activities also contribute to metal concentrations in the environment (Woo, et al., 1993). An activity that massively contributes to the pollution 1
  10. 10. of the lagoon with heavy metal is the local and crude methods of recycling electronic waste (e-waste) to retrieve its metallic components. According to Aanstoos et al (1998) electronic waste consist of 32 different metals at different percentage mass. An excessively high metal concentration in the sediments of Korle lagoon has been reported (Greenpeace 2008). Copper and Zinc were selected based their importance to living organisms. Lead and Cadmium was selected base on their toxicity in small concentrations. Different aquatic organisms often respond to external contamination in different ways, where the quantity and form of the element in water, sediment, or food will determine the degree of accumulation (Begum et al., 2009). The degree of contamination depend on pollutant type, fish species, sampling location, trophic level and their mode of feeding (Asuquo et al. 2004). Species in relatively low trophic levels are exposed to comparatively lower heavy metal concentration. Fishes in the upper food web position are prone to accumulate more heavy metals through bio magnification (Al- Yousuf et al 2000) contamination, although plants can accumulate metals in high levels (Peakall et al 2003). 1.1. Justification 2
  11. 11. The Korle Lagoon in Accra, Ghana, has become one of the most polluted water bodies on earth. It is the principal outlet through which all major drainage channels in the city empty their wastes into the sea. Large amounts of untreated industrial waste emptied into surface drains has led to severe pollution in the lagoon and disrupted its natural ecology. The increased levels of industrial activity and consumption by the urban population lead to the generation of copious quantities of waste (Boadi & Kuitunen. 2002). Agbogbloshie, a suburb of Ghana’s capital, Accra, and just adjacent the lagoon is a known destination for legal and illegal electronic waste (e-waste) dumping from industrialized nations, often referred to as a "digital dumping ground". Millions of tons of e-waste are processed each year in the local recycling workshops. A study by Greenpeace (2008) revealed excessively high metal concentrations in the soils of the open burning grounds and in the sediments of the lagoon. Contaminated sediments do not always remain at the bottom of a water body. Anything that stirs up the water, such as dredging and upwelling, can resuspend sediments. Resuspension may mean that all animals in the water, and not just the bottom-dwelling organisms, will be directly exposed to toxic contaminants (Begum, et al., 2009). Fishes often accumulate large amounts of these metals in polluted areas. They assimilate these heavy metals through ingestion of suspended particulates, food materials and sometimes by constant ion exchange process of dissolved metals across lipophilic membranes like the gills and adsorption of dissolved metals on tissue and membrane 3
  12. 12. surfaces (Begum, et al., 2009). Bio magnification can result in fish at the top of food chain containing hundreds more heavy metals than it appears in the water or in any single fish they eat. Seriola dumerili and Pteroscion peli are important fish species in the Korle lagoon fishery and are in high demand by the inhabitants of Accra especially those around the Korle lagoon. Inhabitants often prefer large sizes of Seriola dumerili and small sizes of Pteroscion peli. Since these species are carnivores they could possibly accumulate heavy metals which could be detrimental to those who consume them. In small quantities, certain heavy metals are nutritionally essential for a healthy life. Some of these are referred to as the trace elements (e.g., iron, copper, manganese, and zinc). These elements, or some form of them, are commonly found naturally in foodstuffs, in fruits and vegetables, and in commercially available multivitamin products (International Occupational Safety and Health Information Centre, 1999) but high quantities of these toxic metals may cause defects like memory loss, high blood pressure, poor concentration, aggressive behaviour, sleeplessness and a number of other defects (Aneum, 2010). 1.2. OBJECTIVES 4
  13. 13. Based on the above reasons the objectives of this study were: • To assess the concentration of zinc, lead, copper and cadmium in the sediment and flesh of Pteroscion peli and Seriola dumerili. • To examine variations in heavy metal concentration in the flesh of the Pteroscion peli and Seriola dumerili in relation to size. 5
  14. 14. CHAPTER 2 2.0. LITERATURE REVIEW 2.1. Global Water Pollution Every day, 2 million tons of sewage, industrial and agricultural waste is discharged into the world’s water (UN-WWAP, 2003), the equivalent of the weight of the entire human population of 6.8 billion people. The UN estimates that the amount of wastewater produced annually is about 1,500 km3, six times more water than exists in all the rivers of the world (UN-WWAP, 2003). Lack of adequate sanitation contaminates water courses worldwide and is one of the most significant forms of water pollution. Worldwide, 2.5 billion people live without improved sanitation (UNICEF and WHO, 2008). Over 70% of these people, who lack sanitation, live in Asia. Sub-Saharan Africa is slowest of the world’s regions in achieving improved sanitation: only 31 percent of residents have access to improved sanitation in 2006. Eighteen percent of the world’s population, or 1.2 billion people, defecate in the open. Open defecation significantly compromises quality in nearby water bodies and poses an extreme human health risk (UNICEF and WHO, 2008). The effects of water pollution is said to be the leading cause of death for humans across the globe, moreover, water pollution affects our oceans, lakes, rivers, and drinking water, making it a widespread and global concern (Scipeeps, 2009). Since the population of cities in the developing world are rising rapidly (Grobicki, 2001) and in-order to meet the ever increasing demand for food, other services for human 6
  15. 15. development including rapid urbanization and industrial growth, many unplanned interventions have been made in water bodies in many parts of the world (Vass, 2007). Polluted water consists of Industrial discharged effluents, sewage water, rain water pollution (Ashraf et al, 2010) and pollution by agriculture or households cause damage to human health or the environment (European Public Health Alliance, 2009). This water pollution affects the health and quality of soils and vegetation, (Carter, 1985). Some water pollution effects are recognized immediately, whereas others don’t show up for months or years (Ashraf et al, 2010). There has been widespread decline in biological health in inland (non-coastal) waters. Globally, 24 percent of mammals and 12 percent of birds connected to inland waters are considered threatened (UN-WWAP, 2003). In some regions, more than 50% of native freshwater fish species are at risk of extinction, and nearly one-third of the world’s amphibians are at risk of extinction. Freshwater ecosystems sustain a disproportionately large number of identified species, but are increasingly threatened by a host of water quality problems (Vié et al, 2009). Seventy percent of industrial wastes in developing countries are disposed of untreated into waters where they contaminate existing water supplies, (UN-Water, 2009). Roughly one unit of mercury is emitted into the environment for every unit of gold produced by small-scale miners; a total of as much as 1000 tons of mercury is emitted each year (UNEP/GRID-Arendal, 2009). 7
  16. 16. 2.1.1. Environmental Aquatic Pollution The pressure of increasing population, growth of industries, urbanization, energy intensive life style, loss of forest cover, lack of environmental awareness, lack of implementation of environmental rules and regulations and environment improvement plans, untreated effluent discharge from industries and municipalities, use of non- biodegradable pesticides/fungicides/ herbicides/insecticides, use of chemical fertilizers instead of organic manures, etc are causing water pollution. The pollutants from industrial discharge and sewage besides finding their way to surface water reservoirs and rivers are also percolating into the ground to pollute ground water sources (Trivedi, 2008). The polluted water may have undesirable colour, odour, taste, turbidity, organic matter contents, harmful chemical contents, toxic and heavy metals, pesticides, oily matters, industrial waste products, radioactivity, high Total Dissolved Solids (TDS), acids, alkalises domestic sewage content, virus, bacteria, protozoa, rotifers, worms, etc. The organic content may be biodegradable or non-biodegradable. Pollution of surface waters (rivers, lakes, and ponds), ground waters, and sea water are all harmful for human and animal health. Pollution of the drinking water and that of food chain is by far the most worry-some aspect (Kant, 2005). Toxic chemical substances introduced into the environment may be transported by the air, water and living organisms and may become a part of the natural biogeochemical cycle and accumulate in the food chain (Gadzała-Kopciuch, 2004). Some of the pollutants like lead (Pb), arsenic (As), mercury (Hg), chromium (Cr) specially hexavalent chromium, nickel (Ni), barium (Ba), cadmium (Cd), cobalt (Co), 8
  17. 17. selenium (Se), vanadium (V), oils and grease, pesticides, etc are very harmful, toxic and poisonous even in ppb (parts per billion) range (Lucky, 2002). There are some minerals which are useful for human and animal health in small doses beyond which these are toxic. Zinc (Zn), copper (Cu), iron (Fe), etc fall into this category. For agriculture, some elements like zinc, copper, manganese (Mn), sulphur (S), iron, boron (B), together with phosphates, nitrates, urea, potassium, etc are useful in prescribed quantities. There are some compounds like cyanides, thiocyanides, phenolic compounds, fluorides, radioactive substances, etc which are harmful for humans as well as animals (Kudesia, 2002). Water bodies contaminated by heavy metals may lead to bioaccumulation in the food chain of an estuarine environment. Such contaminants are transported from its sources through river system and deposited downstream. Since most of the pollutants could be mixed and become suspended solid and bottom sediment through sedimentation, therefore estuary is a potential sink for these pollutants over a long period of time (Morrisey et al., 2003). 2.2. Heavy Metals Heavy metals are metals or, in some cases, metalloids which are stable and have a density greater than 4.5 g/cm 3 and their compounds (UNECE, 1998). Low concentration of metals in water might not necessary reflect that the area is pollution free. The biotic life in such an area might have accumulated the metals from water from time to time. Such a situation could be observed from the higher concentration of heavy metals in the tissue of organisms found in the estuary (Abdullah, 2007). 9
  18. 18. Higher concentrations of heavy metals (such as Cd, Pb, Cu and Zn) in the sediment of an estuary concur with the pattern of those metals found in the tissues of estuary organisms (Abdullah, 2007). 2.2.1. Source of Heavy Metals Heavy metals differ in their chemical properties, and are used widely in electronic components, machinery and materials. Consequently, they are emitted to the environment from a variety of anthropogenic sources to supplement natural background geochemical sources. Some of the oldest cases of environmental pollution in the world were caused by heavy metal extraction and use, for example, copper, mercury and lead mining, smelting The amounts of most heavy metals deposited to the surface of the Earth are many times greater than depositions from natural background sources. Combustion processes are the most important sources of heavy metals, particularly, power generation, smelting, incineration and the internal combustion engine (Battarbee, 1988). Common Metals and their sources also include: • Lead: leaded gasoline, tire wear, lubricating oil and grease, bearing wear • Zinc: tire wear, motor oil, grease, brake emissions, corrosion of galvanized parts • Copper: bearing wear, engine parts, brake emissions • Cadmium: tire wear, fuel burning, batteries (Kiliç, 2011). 10
  19. 19. 2.2.2. Sediments and Heavy Metals in Estuaries Estuaries are important zones of sediment transfer between fluvial and marine systems, often forming sinks for sediment moving downstream, alongshore or landwards and consequently for dissolved and particulate contaminants from recreational, farming, manufacturing and extractive industries, both on land and offshore (Morrisey et al, 2003). Heavy metals in sediments represent a combinational effect of chemical, biological and physical processes occurring in fluvial, estuarine, and coastal environments. Surface sediments integrate these changes that occur in the water column and act both as a repository and source of suspended materials. Spatial variations of heavy metals in the surface sediments are the results of these processes (Lin, et al, 2003). Heavy metals generally exist in two phases in estuarine waters, i.e., in the dissolved phase in the water column and in the particulate phase adsorbed on the sediments. The behaviour of heavy metals in the aquatic environment is strongly influenced by adsorption to organic and inorganic particles. The dissolved fraction of heavy metals may be transported through the water column via the processes of advection and dispersion, while the particulate fraction may be transported with the sediments, which are governed by sediment dynamics. The partition of heavy metals between the dissolved and adsorbed particulate phases depends on the physical and chemical characteristics of the suspended particles as well as various ambient conditions, such as: salinity, pH, and the types and concentrations of dissolved organic matter (Wu et al., 2005). Fine sediments, acting as a source (or sink) for the organic chemical and heavy metals entering (or leaving) the water column with sediments contaminated by the heavy metals, 11
  20. 20. pose a potential threat to the aquatic environment. Resuspension of contaminated bed sediments caused by strong tidal currents may release a significant amount of heavy metals into the water column, and this desorption of contaminants from their particulate phase can have a pronounced impact on the aquatic environment and ecosystem (Zagar, 2006). Although estuaries are sinks for contaminants from the terrestrial environment, there is significant transport of marine material up-estuary as bed load sediment whilst fine- grained terrestrial material may be transported seawards in suspension. Major movement of contaminants from estuaries onto the continental shelf probably occurs only during floods and storms and, in general, the impact on shelf seas is relatively minor and confined to the coastal zone (Ridgway et al, 2000). 2.3. Some Common Heavy Metals Several metals are found in the ecosystem in trace amounts and these metals are of great importance to living organisms. 2.3.1. Copper Copper exist in the natural water system either in the form as the cupric (Cu2+ ) ion or complexes with inorganic anions or organic ligands or as a suspended particle when present as precipitates or absorbed to organic matter ( Mance et al 1984). It can also be adsorbed to bottom sediments or exist as settled precipitate. The concentration of each of these forms depends on complex interaction of many variables including the 12
  21. 21. concentration of copper and hardness, alkalinity, salinity, pH and concentration of bicarbonate, bicarbonate sulphide, phosphate organic ligands and other metal ions. Copper is an essential element to all living organisms, and because of that both deficiency and excess have consequence for the integrity of biochemical functions. The main biological role of copper is as an ingredient, normally in the prosthetic group, of oxidizing enzymes which are important in oxidation-reduction processes (Moolenaar, 1998). Complexes formed by copper are more stable than other metals such as cadmium, lead and zinc. The high concentration of particulate matter in most estuaries will facilitate removal of copper from solution by adsorption to suspended particles which in turn may be deposited and accumulate in sediments. Estuarine sediments are thought to be the most important depositional site for particulate copper transported from rivers, although remobilization may occur when sediments is disturbed. The remaining dissolve copper in the water column is likely to be present either as an organic complex or as a cupric ion. Copper in the cupric form is the most bio available (Grimwood, 1997). Copper is readily accumulated by plants and animals. Whole –body concentration tends to decrease with increasing trophic level. it is also regulated or immobilized in many species and is not biomagnified in food chains to any significant extent (CCREM.,1987). 2.3.2. Lead 13
  22. 22. Lead is a micro element naturally present in trace amounts in all biological materials, thus, in soil, water, plants and animals. It has no physiological function in the organism. Some sources of lead pollution are those emanating from anthropogenic activities such as smelting works, application of wastewater treatment sludges to soil, transportation and also from surface runoffs. Lead pollution sources can also be extended to paints, lead wastes, cell batteries and lead solders and most do enter the organism through contaminated food and air (Boakye, 2011). The maximum acceptable toxicant limit for inorganic lead has been determined for several species under different conditions and results range from 0.04 mg l-1 to 0.198 mg l-1. The acute toxicity of lead is highly dependent on the presence of other ions in solution, and the measurement of dissolved lead in toxicity tests is essential for a realistic result. Organic compounds of lead are more toxic to fish than inorganic lead salts (WHO, 1995). Lead accumulates in sediments and can pose a hazard to sediment-dwelling organisms at concentrations above 30.2 mg kg-1, (according to Canadian Interim Marine Sediment Quality Guidelines). In aquatic ecosystems, uptake by primary producers and consumers seems to be determined by the bioavailability of the lead. The uptake and accumulation of lead by aquatic organisms from water and sediment are influenced by various environmental factors, such as temperature, salinity, and pH, as well as humic and alginic acid content. In many organisms, it is unclear whether lead is adsorbed onto the organism or actually taken up. Consumers take up lead from their contaminated food, often to high concentrations, but without biomagnifications (WHO 1995). Lead uptake by fish reaches equilibrium only after a number of weeks of exposure. Lead is accumulated mostly in gill, liver, kidney, and bone. Fish eggs show increasing lead 14
  23. 23. levels with increased exposure concentration, and there are indications that lead is present on the egg surface but not accumulated in the embryo. Also young stages of fish are more susceptible to lead than adults or eggs. Typical symptoms of lead toxicity include spinal deformity and blackening of the caudal region. In contrast to inorganic lead compounds, tetra alkyl lead is rapidly taken up by fish and rapidly eliminated after the end of the exposure (WHO 1995). 2.3.3. Zinc Zinc is one of the most ubiquitous and mobile heavy metals and is transported in natural waters in both dissolved forms and associated with suspended particles (Mance et al, 1989). In estuaries where concentration of suspended particles is greater, zinc accumulates particularly in anaerobic sediments. A greater proportion is adsorbed to the suspended particles (CCREM, 1987). In low salinity areas of estuaries, zinc can be mobilized on particles by microbial degradation of organic matter and displacement by calcium and magnesium. In high turbidity, greater levels of zinc associated with suspended sediments is deposited with flocculated particles where it can and where it can particularly accumulate in anaerobic sediments. The toxicity and bioaccumulation of zinc is greater at lower salinity (Hunt et al, 1992) and invertebrates generally have high concentrations than fish species. Zinc accumulates in sediments and can pose hazard to sediment dwelling organisms at concentration above 125mg/kg. Zinc is an essential element for many marine organisms and as such is readily bio accumulated. Several species of crustaceans are able to regulate the uptake of zinc but at 15
  24. 24. higher concentration, this process appears to breakdown leading to an influx of zinc also according to (NAS, 1979), gills of fish are physically damaged by high concentrations of zinc. Organisms can take up zinc which is reflected in the bioaccumulation factor but may not reflect in the tissue (Hunt et al 1992). 2.3.4. Cadmium Cadmium is a relatively volatile element not essential to plants, animals and humans. Its presence in organisms is unwanted and harmful. An increased level of cadmium in the air, water and soil increases its uptake by organisms (Järup, 2003). Cadmium uptake from water by aquatic organisms is extremely variable and depends on the species and various environmental conditions, such as water hardness (notably the calcium ion and zinc concentration), salinity, temperature, pH, and organic matter content. The majority of chelating agents decrease cadmium uptake but some, such as dithiocarbamates and xanthates, increase uptake. Increasing temperature increases the uptake and toxic impact, whereas increasing salinity or water hardness decreases them. Acute lethal effects for marine organisms have been noted as low as 16 &micro;g l-1 (WHO ,1992). Cadmium is toxic because it has some similarities with zinc that is an essential element; it is a typical example of a cumulative poison (Järup, 2003). Cadmium is toxic to a wide range of micro-organisms. The presence of sediment, high concentrations of dissolved salts or organic matter all reduces the toxic impact. The main effect is on growth and replication. An increase in toxicity as temperature increases and salinity decreases has been noted. This implies that the same cadmium concentration may have the potential to cause greater toxicity to estuarine rather than to marine species. At low concentrations (10 16
  25. 25. &micro;g cadmium l-1), cadmium inhibits ion transport systems and induces metallothionein synthesis (< 1 &micro;g cadmium l-1) in freshwater fish. Cadmium toxicity has been found to be variable in fish, with salmonids being particularly susceptible to cadmium. Sub-lethal effects in fish, notably malformation of the spine, have been reported. The most susceptible life-stages are the embryo and early larva, while eggs are the least susceptible. There is no consistent interaction between cadmium and zinc in fish (WHO 1992). Cadmium bio accumulates in organisms with the main uptake routes being dissolved cadmium from the water column and cadmium associated with prey items. 2.4. Bio-Importance of Heavy Metals to Humans Some heavy metals (like Zinc and Copper) have been reported to be of bio-importance to man and their daily medicinal and dietary allowances. Their tolerance limits in drinking and potable waters have also been reported, However, some others (like Cadmium and Lead, ) have been reported to have no known bio-importance in human biochemistry and physiology and consumption even at very low concentrations can be toxic (Holum, 1983; Fosmire, 1990; McCluggage, 1991; Ferner, 2001; European Union, 2002; Nolan, 2003; Young, 2005). Even for those that have bio-importance, dietary intakes have to be maintained at regulatory limits, as excesses will result in poisoning or toxicity, which is evident by certain reported medical symptoms that are clinically diagnosable (Fosmire, 1990; Nolan, 2003; Young, 2005). Zinc is a ‘masculine’ element that balances copper in the body, and is essential for male reproductive activity (Nolan, 2003). It serves as a co- factor for dehydrogenating enzymes and in carbonic anhydrase (Holum, 1983). Zinc 17
  26. 26. deficiency causes anaemia and retardation of growth and development (McCluggage, 1991). Calcium is a very vital element in human metabolism. It is the chief element in the production of very strong bones and teeth in mammals. Its tolerance limit is high relative to other bio-useful metals, that is, at 50 mg/l of drinking water .The daily dietary requirement of calcium soars at the highest across both sexes and all ages of humans accommodated at higher doses in the body because its concentration in the blood is well regulated by thyrocalcitonin and parathormone hormones (Holum, 1983). Lead and cadmium have been reported not to have any known function in human biochemistry or physiology, and do not occur naturally in living organisms (Lenntech, 2004). Hence dietary intakes of these metals, even at very low concentrations can be very harmful because they bio accumulate. 2.4.1. Effect of bioaccumulation on humans The bio toxic effects of heavy metals refer to the harmful effects of heavy metals to the body when consumed above the bio-recommended limits. Although individual metals exhibit specific signs of their toxicity, the following have been reported as general signs associated with cadmium, lead, zinc, and copper poisoning: gastrointestinal disorders, diarrhoea, stomatitis, tremor, hemoglobinuria causing a rust–red colour to stool, ataxia, paralysis, vomiting and convulsion, depression, and pneumonia when volatile vapours and fumes are inhaled (McCluggage, 1991). The nature of effects could be toxic (acute, chronic or sub-chronic), neurotoxin, carcinogenic, mutagenic or teratogenic. Cadmium is toxic at extremely low levels. In humans, long term exposure results in renal dysfunction, characterized by tubular proteinuria. High exposure can lead to obstructive lung disease, 18
  27. 27. cadmium pneumonitis, resulting from inhaled dusts and fumes. It is characterized by chest pain, cough with foamy and bloody sputum, and death of the lining of the lung tissues because of excessive accumulation of watery fluids. Cadmium is also associated with bone defects, viz; osteomalacia, osteoporosis and spontaneous fractures, increased blood pressure and myocardic dysfunctions. Depending on the severity of exposure, the symptoms of effects include nausea, vomiting, abdominal cramps, dyspnea and muscular weakness. Severe exposure may result in pulmonary oedema and death. Pulmonary effects (emphysema, bronchiolitis and alveolitis) and renal effects may occur following subchronic inhalation exposure to cadmium and its compounds (McCluggage, 1991; INECAR, 2000; European Union, 2002; Young, 2005). Lead is the most significant toxin of the heavy metals, and the inorganic forms are absorbed through ingestion by food and water, and inhalation (Ferner, 2001). A notably serious effect of lead toxicity is its teratogenic effect. Lead poisoning also causes inhibition of the synthesis of haemoglobin; dysfunctions in the kidneys, joints and reproductive systems, cardiovascular system and acute and chronic damage to the central nervous system (CNS) and peripheral nervous system (PNS), (Ogwuebgu and Muhanga, 2005). Other effects include damage to the gastrointestinal tract (GIT) and urinary tract resulting in bloody urine, neurological disorder and can cause severe and permanent brain damage. While inorganic forms of lead, typically affect the CNS, PNS, GIT and other bio systems, organic forms predominantly affect the CNS (McCluggage, 1991; INECAR, 2000; Ferner, 2001; Lenntech, 2004). Lead affects children by leading to the poor development of the grey matter of the brain, thereby resulting in poor intelligence 19
  28. 28. quotient (IQ) (Udedi, 2003). Its absorption in the body is enhanced by Ca and Zn deficiencies. Acute and chronic effects of lead result in psychosis. Zinc has been reported to cause the same signs of illness as does lead, and can easily be mistakenly diagnosed as lead poisoning (McCluggage, 1991). Zinc is considered to be relatively non-toxic, especially if taken orally. However, excess amount can cause system dysfunctions that result in impairment of growth and reproduction (INECAR, 2000; Nolan, 2003). The clinical signs of zinc toxicities have been reported as vomiting, diarrhoea, bloody urine, icterus (yellow mucus membrane), liver failure, kidney failure and anaemia (Fosmire, 1990). 2.5. Lagoon Pollution in Ghana Presently, Ghana is dealing with the rate of urban periphery settlements which is as a result of the massive migration of the rural inhabitants to the cities, especially to Accra. Unfortunately persons in these settlements often lack essential social amenities, especially those related to sanitation, resulting in heavy environmental pollution. The contamination of lagoons with heavy metals is a major source of concern since it is a habitat for fish and other aquatic organisms such as mussels, oysters, prawns and lobsters which are major sources of protein for most people in Ghana. Heavy metals released into the environment find their way into aquatic systems as a result of direct input, atmospheric deposition and surface runoffs. Fish species can accumulate these heavy metals in their tissues at concentrations greater than the ambient water and pose a health threat to humans who consume them (Armah, 2007). 20
  29. 29. Natural waters therefore become the key environmental component that suffers massively from such pollution and this is the current situation epitomized by the Korle lagoon in Accra. Some years ago the Korle lagoon was of economic importance to the country of which some were able to reach it outside borders. Some of which were salt, fish and wood (Armah, 2007). 2.6. State of the Korle lagoon The Korle lagoon, which is a major run-off water receptacle and a point source of pollution into the Gulf of Guinea, has been negatively impacted by the uncontrolled domestic and industrial pollution. Previous water quality surveys indicated that the Korle lagoon is moderate to grossly polluted water body as evidenced by the physical, chemical and bacteriological characteristics which can be traced to discharges of domestic and industrial effluents from inland as well as to the operations of the sewage outfall in the vicinity of the lagoon’s entrance (Karikari et al, 2007). Up to the 1950s, the Korle Lagoon supported a thriving fishery, but presently it supports only a few fish species which include Seriola dumerili and Pteroscion peli, are restricted to its estuary (Biney and Amuzu, 1995). The increasing pollution of Korle Lagoon is as a result of the rapid urbanization of Accra. This has been unaccompanied by a significant increase in sanitation facilities. The process has been assisted by rapid industrialization without regard for environmental safety. Rapid population growth, enhanced by the facilities and job opportunities, continues to draw people into Accra. This has resulted in considerable stress on the 21
  30. 30. already inadequate urban facilities including the housing and basic sanitation amenities. This situation has led to the development of slums and shantytowns, and the consequent degradation of the urban environment. With little equipment to manage the refuse, garbage is collected only in high-income areas (Doe, 2000). The remaining areas disposed of their garbage in public containers, in open spaces, streams and drainage systems. The catchment area is surrounded by shantytowns, including Korle Gonno, Korle Dudor, Adadinkpo and James Town, among many others. Prominent among these slums is Sodom and Gomorra (Old Fadama), a growing squatter settlement. The site exhibits poor housing conditions and consists mainly of wooden shacks (Doe, 2000). There are no sanitation facilities, and people defecate directly into the lagoon with all kinds of waste being disposed of into the water body. 2.6.1. Heavy metal sources to the lagoon A major activity that massively contributes to the pollution of the lagoon is the local and crude methods of recycling electronic waste (e-waste) to retrieve the metallic components. Agbogbloshie, a suburb of Ghana’s capital, Accra, and just adjacent the lagoon is a known destination for legal and illegal of electronic waste (e-waste) from industrialized nations. Often referred to as a "digital dumping ground", millions of tons of e-waste are processed each year in the local recycling workshops. At these workshops, e- waste is recycled with virtually no regulations, and primarily involves manual disassembly of the obsolete electronic products and open burning to isolate copper and other valuable metals from plastics. 22
  31. 31. Other sources of heavy metals into the Lagoon can be traced to effluent discharged from domestic and industrial activities. According to Boadi and Kuitunen (2002) and Agodzo et al, (2003), approximately 60% of the domestic and industrial waste from Accra, the capital of Ghana, with a population of approximately 4.0 million people, flows into the Lagoon. Other major potential sources of heavy metal pollution in the Lagoon are the numerous local metal smelting industries and the small garages and workshops located within in the vicinity of the Lagoon. Another major source of pollution in the Lagoon is the Odaw River, a major inlet of the Korle Lagoon. The Odaw River drains the high density low income areas of Accra and has a large concentration of industries including breweries, several textile factories and vehicle repair workshops in its catchment. 2.6.2. Effect of Korle lagoon pollution Severe pollution of the lagoon has resulted in the reduction of aquatic invertebrates and the complete disappearance of some species from the lagoon’s environs. The break in the food chain has resulted in the near extinction of both resident and non-resident birds, which feed and roost in the mangroves and mudflats along the lagoon. The pollution has also resulted in a fowl stench, which in itself is a disincentive for tourism development. Domestic and industrial pollutants have contributed to increased biochemical oxygen demand and concentration of toxic chemicals in the water body (Biney and Amuzu, 1995). 2.6.3. Activities at the estuary 23
  32. 32. Presently however, beach seining and other fishing activities take place at the estuary of the lagoon and within 500 m offshore and the harvested fish are usually sold to local food vendors and also to satisfy domestic protein requirements. Although fish from the estuary of the lagoon are believed to be unwholesome for human consumption, very little research has been carried out to determine the levels of contaminants in the flesh of the fish harvested from the Lagoon (Entsua-Mensah, 2004). 2.7. Fish Species There is a definite pattern in the distribution of fish species on the continental shelf (Longhurst, 1965). The available data indicate that the distribution of a number of species is limited by the depth of the thermocline and is influenced by the type of bottom deposits (sand and silts), and the depths on the continental shelf, the slope of which is variable. There are discrete ecological fish communities, each of which is fairly homogeneous. However, there is also ecological and micro geographical heterogeneity of fish communities. Besides, migration of species from the estuaries and creeks to the open shelf areas and vice versa is known to occur. The following fish communities are exploited by the artisanal fishing units: i. the estuarine and creek sciaenid sub-community, ii. the offshore suprathermoclinal sciaenid sub-community (on soft deposits), iii. the sparid sub-community (on sandy) (FAO, 1981). 24
  33. 33. 2.7.1. Seriola spp The genus Seriola is of the family Carangidae, order Perciformes, and class Actinopterygii. Three species of the genus Seriola are caught at the estuary of the Korle lagoon with the dominant species being Seriola dumerili. The greater amberjack, S. dumerili, is a cosmopolitan species, found in warm waters all over the world. Its main morphological characteristics are the elongated, fusiform and slightly laterally compressed body, covered with small scales (cycloids). Their color is yellow-green in juveniles; in adults it is blue or olivaceous dorsally and silvery to white on the sides and belly. S. dumerili is a multiple spawning fish, and it may release several batches of eggs during the same spawning season. The ovary type in this group is synchronous: at least two size groups of oocytes are present at the same time (Grau 1992). This species is gonochoric without sexual dimorphism, and both sexes are separated. According to Micale et al. (1993), maturity occurs at three years of age but functional breeders are 4 and 5 years old for males and females respectively. Marino et al. (1995) reported the first reproductive season for this species to be at 4 years of age for both sexes, even though 40% of males are sexually mature at 3 years of age. Japanese amberjack (S. quinqueradiata) are present in the Western Central Pacific Ocean from Japan and the eastern Korean Peninsula to the Hawaiian Islands. This species reaches a maximum size of 150 cm TL (male/unsexed) and a maximum weight of 40 kg. It shows asynchronous oocyte development. Yellowtail amberjack (Seriola lalandi) are present in Atlantic, Pacific and Western Indian Oceans. It is considered a circumglobal species, supporting commercial and recreational 25
  34. 34. fisheries worldwide. This species is a spring-summer spawner, with a multiple group synchronous oocyte development and, like the greater amberjack (S. dumerili), has the capacity for multiple spawning within a reproductive season. The smallest size at which females caught in New Zealand matured was 775 mm FL; 50% reached sexual maturity at 944 mm, while all were mature at 1 275 mm. McGregor (1995) reported maturity at 580-670 mm. In Australia, according to Gillanders, et al (1999), mature females of this species appeared at 698 mm (3 years) reaching 50% at 834 mm (4-5 years). The differences in size between these 2 populations could be attributed to different rearing conditions. 2.7.2. Pteroscion peli Belongs to the Class Actinopterygii (ray-finned fishes) order perciformes (Perch-likes) > family sciaenidae (Drums or croakers). Pteroscion peli occurs only along the West coast of Africa, from Senegal to Angola, where it is found in mid waters as well as on mud, sandy mud bottoms in coastal waters and also occurs seasonally in brackish water areas. Its depth distribution extends from the shoreline to 200 m but the species prefers waters of less than 50 m and is one of the most abundant sciaenids in shallower waters and feeds on fish, cephalopods, shrimps and annelids (FAO 1986). 26
  35. 35. CHAPTER THREE 3.0. METHODOLOGY 3.1. Description of the study area The Korle lagoon is a coastal wetland that joins the Gulf of Guinea at a point near Korle Gonno; a suburb of Accra (Grant, 2006). It serves as the major floodwater conduit for the Accra Metropolitan Assembly (Fig 3.1), the lagoon is estimated to drain a total catchment area of 400 km2 (Karikari et al, 1998). The major hydrological input includes the Odaw River, two huge drains that border the lagoon, and rainfall including runoff. A mixture of land uses characterizes the areas adjacent to the lagoon (Boadi and Kuitunen, 2002). Fig 3.1 Korle lagoon and its environs (IMDC, 2011) 27
  36. 36. 3.2. Sample collection Fish samples were obtained from fishers (Plate 3, 4) at the estuary of the Lagoon and transported on ice in an insulated chest (Plate 1, 2). Plate 1 Pteroscion peli from the Korle lagoon Estuary Plate 2 Seriola dumerili from the Korle lagoon Estuary A total of 8 samples (Plate 5, 6) were obtained monthly for each species over the four months period. Samples from each species were categorized into two classes based on the sizes obtained for each; Pteroscion peli (Small ≤14cm and large ≥ 15cm) and Seriola dumerili (Small ≤24cm and large ≥25 cm) and were stored in a deep freezer prior to the heavy metal analysis. 28
  37. 37. Plate 3 Beach Seining at the Korle lagoon estuary Plate 4 Obtaining samples from fishers Plate 5 Some Pteroscion peli obtained Plate 6 Some Seriola dumerili obtained Three sediment sampling sites were selected from site A, site B and site C as shown in The sediment sample was taken from each site and was divided into three to ensure accuracy in the result for each site sampled. This was done for the four months study period; October 2011 to January 2012. The Ekman grab was used in collecting the sediments samples. At site B and C the Ekman grab was mounted in a boat, after 29
  38. 38. releasing the instrument to the bottom the boat owner dived to trip the over lapping spring loaded with scoop, the depth of both portion could be between 1 to 4 meters whilst at point C samples were taken by walking into the water to points where the water reached the knee and with the Ekman grab sediments were collected. Samples were stored in plastic bottles and packaged in plastic bags and were kept in a cool, dry and ventilated room prior to heavy metal analysis. Sampling point (A) is the area that receives frequent sea water at both low tides and high tides with no rock deposited on both side (Plate 7). Plate 7 Sampling point (A) Sampling point (B) is the area affected by the influx of both fresh water and sea water and rocks are deposited on the right side of the curved channel (Plate 8). 30
  39. 39. Plate 8 Sampling point (B) Sampling point (C) is the area that receives fresh water frequently than sea water and also joins B in a slightly curved channel with rocks deposited on both sides (Plate 9). Plate 9 Sampling point (C) 3.3. Heavy Metal Analysis In order to free bonded heavy metals in the flesh of Pteroscion peli, Seriola dumerili and sediments, wet di-acid digestion was done. All procedures for the analyses were based on the Association of Analytical Chemist (AOAC 2003) protocol. 31
  40. 40. 3.3.1. Sample Digestion Fish and sediments samples acquired were digested at the same time. Sample digestion is the removal of organic materials and the conversion of metals present into soluble forms. 3.3.2 Fish digestion The total length (Plate 10) and body weight of the fish samples after defrosting were measured with a centimetre rule and weighed with an electric scale (Sartorius model, BP 6100) and labelled after identification. Small part (5grams) of the flesh from its side were removed and chopped with the aid of stainless steel dissection instruments, while wearing surgical gloves. After, flesh samples were then digested with a di- acid mixture, (nitric acid, and perchloric acid in a ratio of 9: 4). Plate 10 Total length of Seriola dumerili being taken One gram of the chopped flesh samples was separately taken and placed in a 100ml volumetric flask. Ten millilitres of di acid mixture was added. The content was mixed by swirling in the volumetric flask. The flask was then placed on a hotplate in a fume hood and heated starting at 90o C and raised to 200o C. Heating continued until the production of a red NO2 fume ceases. The contents were further heated until the volume was reduced to 3-4ml and became colourless without being dry. It was made to cool to room 32
  41. 41. temperature. The volume was made up with distilled water and filtered with a Whatmann filter paper. The filtrate was then diluted to 50ml mark in a volumetric flask with double distilled water. It was then poured into small containers. The containers containing the digested samples were kept at 4˚c in a refrigerator prior to heavy metal analysis (Plate 12). 3.3.2. Sediment digestion Sediment samples were labelled (according to their location) on the field and air dried at room temperature. Sediments were dried on a plastic sheet (Plate 11). Plate 11 Sediments being air dried at room temperature The dried materials were grounded to pass through a 63µm sieve and stored in plastic bottles. Digestion was done for the sediments as it was done for the fish flesh samples above at the Faculty of Renewable Natural Resources. 33
  42. 42. Plate 12 Some containers containing digested samples 3.3.3. Determination of heavy metal concentration Heavy metal analysis was done at the Anglo Gold Ashanti Laboratory. The concentrations of copper, cadmium, lead, and zinc, were determined with the aid of flame Atomic Absorption Spectroscopy, (AAS) (SpectrAA 220 model). A blank solution of the di-acid and distilled water used which contained no analyte element was made and after, a series of calibrated solutions of the di acid and distilled water containing known amounts of analyte element (the standards) were also made. The blank and standards were atomized in turn, with their respective responds measured. Graph of both responses were plotted. The digested samples were then atomized and their response measured. The concentrations of heavy metal in the sample were known by the calibration and the absorbance obtained for the unknown. 34
  43. 43. All samples were accompanied by blanks at a rate of one blank per 20 samples. Replicate analyses were conducted for all the samples to evaluate the precision of the analytical technique. The results were expressed as total concentration (μg/g wet weight (ww). 3.3.4. Measurement of Physicochemical Water Parameters Monthly measurement of temperature, salinity, pH, total dissolved solids (TDS), conductivity and dissolved oxygen (DO) of the Korle Lagoon were taken between the hours of 7am-10am, using a multi-parameter probe at the 3 sampling site over the four months period -(YSI 550A model)(Plate 13). Plate 13 Water Quality parameter been taken insitu 35
  44. 44. CHAPTER FOUR 4.0. RESULTS 4.1. Heavy metal concentrations in Sediment Samples Copper concentration s were consistently fluctuating over the period and ranged between 4.38 μg/g ww to 5.90 μg/g ww from November 2011 to January 2012. A mean concentration of 5.12 μg/g ww was recorded for the estuary over the four month period. Lead concentration increased drastically from a mean value of 2.80 μg/g ww in October to 39.20 μg/g ww in December 2011. A decrease in the concentration of lead was recorded for January 2012. Zinc ranged from 9.46 μg/g ww to 14.66 μg/g ww but this decrease was inconsistent as concentration declined from 12.44 μg/g ww in November 2011 to 9.46 μg/g ww in December 2011. Cadmium concentration fluctuated over the period with highest concentration of 2.50 μg/g ww recorded in December 2011.Heavy metal levels in sediment over the period ranked in the following order: Pb > Zn >Cu >Cd. The monthly heavy metal concentrations of the four metals in the sediments of the Korle lagoon estuary are shown in Table 4.1. 36
  45. 45. Table 4.1. Copper (Cu), Lead (Pb), Zinc (Zn) and Cadmium (Cd) concentration (μg/g ww) in the sediment from the Korle lagoon Estuary. Month n Cu Pb Zn Cd October 9 4.41±0.15 2.80±0.96 12.21±4.28 2.33±0.25 November 9 4.38±0.39 2.86±1.49 12.44±3.62 2.26±0.30 December 9 5.80±0.02 39.20±0.46 9.46±0.88 2.50±0.10 January 9 5.90±0.08 38.36±1.69 14.66±0.05 2.23±1.00 Mean 5.12±0.16 20.80±1.15 12.19±2.20 2.33±0.41 NOAA (1995) ERL 34.00 46.70 150.00 1.20 ERM 270.00 218.00 410.00 9.60 National Oceanic and Atmospheric Administration (NOAA), Effect Range low (ERL), Effect Range Medium (ERM) Values are mean± SD, n= number of samples. 4.2. Heavy metal concentrations in Pteroscion peli Mean concentration of copper in Pteroscion peli over the sampled period was 5.11 μg/g ww. Copper (Cu) levels increased between 2.83 μg/g ww in November 2011 to 7.65 μg/g ww January 2012. In October 2011 concentration declined from 3.02 μg/g ww to 2.02 μg/g ww in November 2011. A mean lead (Pb) concentration of 2.73 μg/g ww was recorded over the study period. An increase and decrease in concentration alternated over the sampling period. Cadmium (Cd) concentration consistently increased from 1.48 μg/g ww to 2.91 μg/g ww over the study period. Zinc (Zn) concentration increased from November 2011 to January 2011 with values ranging between 13.58 μg/g ww to 23.11 37
  46. 46. μg/g ww for both months respectively. Between October 2011 and November 2011 concentration dropped from 14.09 μg/g ww to 13.58 μg/g ww. A mean concentration of 16.41 μg/g ww was recorded over the study period. Mean ± standard deviation of Cu, Pb, Zn and Cd concentrations (μg/g ww) in the flesh of Pteroscion peli from the Korle lagoon estuary from October 2011 to January 2012 is presented in Table 4.2. Table 4.2. Heavy metal concentrations (μg/g ww) in the flesh of Pteroscion peli from the Korle lagoon estuary Month n Cu Pb Cd Zn October 8 3.02 ± 1.20 2.62±1.1.83 1.48± 0.25 14.09±2.80 November 8 2.83 ± 0.42 2.87 ±1.80 1.51±0.29 13.58±1.97 December 8 6.92±0.91 2.51±0.45 2.81±0.22 14.86±4.27 January 8 7.65±0.93 2.95±0.34 2.91±0.15 23.11±6.99 Mean 5.11±0.86 2.73±1.10 2.17±0.22 16.41±4.00 WHO (1983) 10 2.0 2.0 1000 WHO (2005) - 0.5 0.5 1000 World Health Organization (WHO) Values are mean± SD, n= number of samples 4.3. Heavy metal concentration in Seriola dumerili 38
  47. 47. Concentration trend observed in Seriola dumerili varied to that of Pteroscion peli. Copper (Cu) concentration increased from November 2011 to January 2012 from 3.36 μg/g ww to 6.14 μg/g ww. A mean concentration of 4.43 μg/g ww was recorded over the period. Lead (Pb) concentrations over the period fluctuated between 2.07 μg/g ww in December 2011 to 3.01 μg/g ww in November 2011. A decrease in concentration was observed from October 2011 to November 2011 and that of November 2011 to December 2011.A mean concentration of 2.54 μg/g ww was recorded over the period. Cadmium (Cd) level of 1.75 μg/g ww was recorded as the mean concentration over the sampling period. Cadmium levels in Seriola dumerili were inconsistent over the study period between 1.35 μg/g ww to 2.95 μg/g ww. Zinc (Zn) concentrations increased from November 2011 to January 2012 with its level increasing from 13.43 μg/g ww to 14.98 μg/g ww respectively. A mean concentration of 13.90 μg/g ww was recorded over the study period. Cu, Pb, Zn and Cd concentrations (μg/g ww) in the flesh of Seriola dumerili from the Korle lagoon estuary is presented in Table 4.3. Table 4.3. Heavy metal concentrations (μg/g ww) in the flesh of Seriola dumerili from the Korle lagoon estuary 39
  48. 48. Month n Cu Pb Cd Zn October 8 3.38 ± 0.76 2.90 ± 2.0 1.42 ± 0.31 13.45 ± 6.26 November 8 3.36 ± 0.32 3.01 ± 2.07 1.35 ± 0.29 13.43 ± 6.34 December 8 4.85±2.32 2.07±0.30 2.31±1.20 13.76±6.04 January 8 6.14±1.52 2.20±0.59 2.95±0.43 14.98±4.66 Mean 4.43 ± 0.87 2.54 ± 0.92 2.03 ± 0.43 13.90 ± 0.78 WHO (1983) 10 2.0 2.0 1000 WHO (2005) - 0.5 0.5 1000 World Health Organization (WHO) Values are mean± SD, n=number of samples 4.4. Heavy metals in the flesh of P. peli and the S. dumerili in relation to sizes In order to examine variations in heavy metal concentration in the flesh of the two fish species in relation to size, a plot of total accumulation versus size were carried out for the two fish species (Fig 4.1 and 4.2). 4.4.1. Pteroscion peli 40
  49. 49. Heavy metal concentration in relation to size of Pteroscion peli increased with increase in size for October 2011 and December 2011, even though for November 2011, zinc concentration in Small Pteroscion was higher than that of large size. In January 2012, copper and zinc concentrations increased in small Pteroscion peli than in large size Pteroscion peli. Lead concentration in December 2011 was relatively higher in the small fishes than in large samples (Fig 4.1 below). Fig 4.1 Variations in Cu, Pb, Cd and Zn concentrations in the flesh of Pteroscion peli in relation to body size (Small ≤14cm , Large ≥ 15cm) 4.4.2. Seriola dumerili 41
  50. 50. Heavy metal concentration in October 2012 and November 2012 increased with increase in size as large size Seriola dumerili recorded higher levels than smaller Seriola dumerili. On the other hand, small fish size fishes had higher concentration of copper and zinc for December 2011 and January 2012. Lead concentrations in December 2011 were high in large Seriola dumerili than in small once. Fig 4.2.Variations in Cu, Pb, Cd and Zn concentrations in the flesh of Seriola dumerili in relation to body size (Small ≤24cm, large ≥25 cm) 42
  51. 51. 4.5. Physicochemical Parameters of the Korle lagoon Physicochemical parameters for the four months (October 2011 to January 2012) sampling period was relatively uniform as shown in Table 4.4. Temperature conditions in the lagoon ranged from 26.60°C to 29.10 °C over the period, a consistent increase in temperature from November 2011 to January 2012 was recorded Dissolve oxygen levels in the estuary was fairly constant over the sampling period even though some portions of the estuary recorded very low oxygen levels. pH level over the sampling period was relatively neutral. A high conductivity of 3901 mg/l was recorded in January 2012. Salinity levels were low over the sampling months and were relatively similar for the sampling months. A Total Dissolve Solid value of 1991 μs/cm was recorded in December and was the highest over the study period. Table 4.4. The physicochemical parameters of the Korle Lagoon from October, 2011 – January, 2012 Parameter n October November December January Temperature (°C) 3 26.81±0.59 26.60±0.80 29.10±1.10 28.50±0.10 DO (mg/l) 3 6.10±1.10 6.00±0.41 5.98±0.04 6.00±1.30 TDS ( μs/cm) 3 1748±397.93 1553±495.62 1991±0.05 1901±1.42 Salinity (ppm) 3 15.05± 0.41 14.77± 1.80 16.01± 0.01 15.98± 1.03 Conductivity (mg/l) 3 3588±553.65 3381±158.04 3008±0.01 3901±1.07 pH 3 7.30±0.30 7.16±0.24 7.07±0.86 7.18±1.05 Total Dissolve Solids (TDS), Dissolved Oxygen (DO), Values are mean± SD, n=number of data recorded 43
  52. 52. CHAPTER FIVE 5.0. DISCUSSION 5.1. Heavy Metal Concentration in Sediments Heavy metals in sediments may represent a combinational effect of chemical, biological and physical processes occurring in the fluvial, estuarine, and coastal environments. Fluctuations in the concentrations of heavy metals in the sediment of the Korle lagoon estuary might be due to the ability of surface sediments to integrate these changes that occur in the water column and act both as a repository and source of suspended materials. Spatial variations of heavy metals in the surface sediments are the results of these processes (Lin, et al 2003). Moreover, heavy metals generally exist in the particulate phase adsorbed on the sediments. This behaviour of heavy metals in the estuary sediment may be strongly influenced by adsorption to organic particles (sewage deposited at the Korle lagoon estuary) and the inorganic particles in the lagoon (Table 4.4). The particulate fraction may be transported with the sediments, which are governed by sediment dynamics. Re-suspension of contaminated bed sediments may be caused by strong tidal currents which may release a significant amount of heavy metals into the water column (Zagar, 2006). In addition, the relatively high levels of cadmium in the sediments compared to the Effect Range Low (ERL) could be due to the high concentrations of dissolved salts or organic matter which reduces its accumulation in sediments. Lead readily accumulates in sediments and this could be the reason for the high levels recorded over the period. Sediments are also thought to be the most important depositional site for particulate copper transported from rivers; although remobilization may occur when sediments are 44
  53. 53. disturbed. The low copper levels recorded could be due to the regular mixing of the water column due to its fluvial flow rate. Moreover, during high turbidity, greater levels of zinc associated with suspended sediments are deposited with flocculated particles where it can and where it can particularly accumulate in anaerobic sediments (Hunt et al, 1992). Furthermore, fluctuation of heavy metals in the sediment could be due to the water chemistry of the Korle lagoon estuary which may controls the rate of adsorption and desorption of metals to and from sediments. The adsorption process could remove metals from the water column and store these metals in the substrate. Desorption on the other hand may return the heavy metals from sediment to the water column where recirculation and bio assimilation could take place. High salt concentrations could create increase competition between cations and metals for binding site. This may cause metals to be driven off from sediments into the overlying water, and this may often occur at estuary due to river flow inputs and tides. Decreased redox potential under hypoxic conditions could change the composition of metal complexes as metals bind to oxygen to form oxides and this could release the heavy metal ions into the overlying water at the estuary. pH may increase competition between metals and hydrogen ions for binding site. A lower pH could also dissolve metal carbonate complexes releasing free ions into the water column (Connell et al, 1984) as a result of the deposition of Sewage into the Korle lagoon estuary. According to Long et al. (1995), the concentration of copper, lead and Zinc recorded occurs below the Effect Range Low value therefore their effects on fishes at the estuary would rarely be observed. Cadmium concentration recorded was equal to the ERL but 45
  54. 54. below the ERM, which implies that fishes at the estuary could occasionally be affected by Cadmium. 5.2. Heavy Metal effect in fish species The mean concentration of Copper and Zinc in Pteroscion peli and Seriola dumerili were lower as compared to the World Health Organization standards (2005). Cadmium and Lead concentration were higher than the standard used. The lower levels of copper in the flesh of both fishes could be due to the role of copper as an ingredient, normally in the prosthetic group, of oxidizing enzymes which are important in oxidation-reduction processes in fishes (Moolenaar, 1998). Also, copper in the cupric form may be the most bio available (Grimwood, 1997) and could be readily accumulated by the fishes. It may also be regulated or immobilized in many species and might not be biomagnified in the food chain to any significant extent (CCREM, 1987). Low level of Zinc recorded could be due to the up take of zinc readily by the study fish species which may not reflect in the flesh tissue (Hunt et al, 1992). High level of lead concentration could be due to the uptake and accumulation of lead by fish from water and sediment and this may be influenced by various environmental factors. Consumers such as (Pteroscion peli and Seriola dumerili) may take up lead from their contaminated food, often to high concentrations, but without bio magnifications (WHO, 1995). Lead uptake by fish could reach equilibrium only after a number of weeks of exposure. Typical symptoms of lead toxicity include spinal deformity and blackening of the caudal region as observed in the obtained fish samples. Tetra alkyl lead which is an inorganic lead 46
  55. 55. compounds may rapidly be taken up by fish and rapidly eliminated after the end of the exposure (WHO, 1995). Cadmium bio accumulates in organisms with the main uptake routes being dissolved cadmium from the water column and cadmium associated with prey items. This could be the reason for the high levels in Seriola dumerili and Pteroscion peli (WHO, 1992). 5.3. Variation in Metal Concentrations in Relation to Body Size Large fishes for both species had a higher metal concentration in Pteroscion peli and Seriola dumerili, but thoroughly there were no variations in metal concentrations between the two size classes for both fish species and may be due to similarities in bioavailability of the heavy metals to the two fish species (Pteroscion peli and the Seriola dumerili.) from the Korle lagoon estuary, since both fish species are piscivorous (Ferreira et al., 2004). Smaller fishes might have accumulated high concentrations of heavy metals and this might be due to their size, their feeding pattern and availability of the heavy metals (FAO, 2012). 47
  56. 56. CHAPTER SIX 6.0. CONCLUSIONS Heavy metal levels in fishes sampled were less than what was found in the sediment samples. Heavy metals in sediment were continuously adsorbed and desorbed from sediments into the overlying water column. The sediment quality in terms of the heavy metals was acceptable but could pose a serious risk to the aquatic life of the lagoon estuary in future if nothing is done to check metal accumulation in the Korle lagoon estuary sediment. The four metal concentrations in the flesh of the two fish species were lower for Zinc and Copper but saw a high concentration for Cadmium and Lead as compared to the World Health Organization Standard (2005) hence not safe for human consumption. From the study however, it was also depicted that Pteroscion peli and Seriola dumerili accumulate heavy metals in their flesh regardless of size. 6.1. RECOMMENDATIONS The heavy metal concentrations in estuary have to be monitored on a more regular basis for the effects of pollution on other fish communities. Although fish flesh (muscle) is the most important part to be used for human consumption, fish skin and liver may also be consumed to some extent. Target organs such as liver, kidney, gonads and gills, have a tendency to accumulate heavy metals in high values and therefore a study has to be conducted to assess the concentration of heavy metals in them. 48
  57. 57. Moreover, Secondary feeders like filter feeders (Mugil cephalus) and other herbivores fishes from the Korle lagoon estuary could be studied to know their bio accumulation levels and their magnification in the food chain. Accumulation of heavy metals in fish flesh may be considered as an important warning signal for fish health and human consumption. The present study shows that consumption of fish from the Korle Lagoon estuary should be prohibited and should be discouraged because of the high levels of Pb and Cd in the flesh of Seriola dumerili and Pteroscion peli in both small and large sizes. 49
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