1. Case study Assignment
Course: Marine Extreme System
Presented By
Islam Md Jakiul

2. Ploughing the deep sea floor
Objectives
 To focus on bottom trawling effects on deep ocean
floor
Results
 Bottom trawling have direct impact on fish
populations and benthic communities
 Also modify the physical properties of seafloor
sediments, water-sediment chemical exchanges and
sediment fluxes
 Reworking of the deep sea floor by trawling gradually
modifies the shape, morphology of the deep sea floor
become smoother over time
 Following modernization of fishing techniques, bottom
trawl net become an important driver of deep
seascape evolution
 Researcher anticipate that the morphology of the
upper continental slope in many parts of the world’s
oceans could be altered by intensive bottom trawlinghttp://www.newindianexpress.com/

3. Ploughing the deep sea floor
In the upper portion of continental slope the morphological complexity, as well as
benthic habitat heterogeneity, has been drastically reduced, potentially affecting
species diversity by regulating levels of competition, predation and physiological
stress
Huge volume of sediment that can be remobilized downslope by trawling activities
Bottom trawling has been compared to forest clear-cutting
The frequent repeated trawling (ploughing) over the same ground, involving
displacement of sediments owing to mechanical redistribution
 Underwater trawled continental-slope equivalent of a gullied hill slope on land, part of which has
been transformed into crop fields that are ploughed regularly, thus replacing the natural contour-
normal drainage pattern by levelled areas with a smaller-scale contour-parallel alignment of troughs
and crests
 Although farmers usually plough their land a few times per year, at sea trawling can occur on a
nearly daily basis
Conclusion and criticism

4. Ploughing the deep sea floorRelated Article
Palanques, A., Puig, P., Guillén, J., Demestre, M., & Martín, J. (2014). Effects of bottom trawling on the Ebro
continental shelf sedimentary system (NW Mediterranean). Continental Shelf Research, 72, 83-98.
Results
Trawling affects the morphology of the seabed
Trawling produces an upward increase of the silt and the organic
carbon content in the sediment column
Trawling generates significant turbidity peaks mainly during working
days.
Resuspension by trawling more than doubles the suspended
sediment load of the Bottom nepheloid layer.
Silt content and median grain size of
the surface sediment samples from
he trawled and untrawled area
Objectives
 To study the physical changes induced by trawling, analyzing seafloor
morphology, sediment characteristics and turbidity in trawled and un-
trawled zones

5. Ploughing the deep sea floorRelated Article
Trawling affects the distribution of silt content as well as organic carbon content.
Vertical distribution of the average silt content and
median grain size from trawled and untrawled area
Vertical distribution of the average organic carbon
content from trawled and untrawled area
Trawling is altering the modern sediment dynamics inducing the export of additional sedimentary supplies off-shelf.
All these effects induced by trawling have occurred during the last few decades, changing natural conditions in the fishing
ground.

6. Tighten regulations on deep-sea mining
Objectives
 This article discussed on necessity of
tight regulations for deep sea mining to
protect deep sea vents and theirs
peculiar biodiversity
Key messages and results
 Deep sea vents are underwater hot springs in
volcanically active areas of the Pacific Ocean
floor.
 These hydrothermal vent support bacteria that
use chemicals erupted from vent fluids to
generate cellular energy.
 At deep sea barren area, this bacteria feed so
many luxurious and beautiful invertebrates
 Additionally this deep sea vents are rich of
minerals e.g. Zn, Cu, Ag and Au
 With the ever increasing demand to fulfill life style
and advancement of sea mining technologies,
deep sea mining likely to be inevitable.
 To avoid/minimize the mining effects scientists
need to promote conservation at every levels-
from government to mining companies

7. Tighten regulations on deep-sea mining
 Continuing research since last three decades researchers continue to find new vent
sites in remote locations and new species, adaptations, behaviors and
microhabitats, even in well-known settings
There is much more to learn about hydrothermal vents, still now no strategies to
assess the cumulative impacts of mining and researchers still don’t know the best
way to mitigate mining activities
Government agencies and International Seabed Authorities(ISA) should function
properly for deep sea mining
It’s a urgent need to establish conservation guidelines in functioning governance and
regulatory frameworks
 Sea-floor hot springs remain pristine should kept touched by mining. But for unavoidable reasons
its scientific value must be weighed against other values, including economic ones
 Human may choose to threaten these unique habitats for development and to feed unlimited
lifestyles that depend on relentless demand for minerals and other resources.
Conclusion and criticism

8. Tighten regulations on deep-sea miningRelated Article
Lodge, M., Johnson, D., Le Gurun, G., Wengler, M., Weaver, P., & Gunn, V. (2014). Seabed mining: International
Seabed Authority environmental management plan for the Clarion–Clipperton Zone. A partnership
approach.Marine Policy, 49, 66-72.
Context
 The main deep-sea mineral resources are: Polymetallic nodules, Manganese
crusts, Polymetallic sulphide deposits
 Distinct ecosystems are or can be associated with these minerals and will be
affected in different ways by different types of mining.
 Dredging for nodules is likely to damage large areas of the seabed and
disperse large clouds of sediment.
 Polymetallic sulphide mining may destroy active and inactive hydrothermal
vents (black smokers) and their associated communities and disperse toxic
materials.
 The extraction of cobalt rich crusts may destroy the benthic seamount
communities and dependent fauna.
Objectives
 To understand the hydrothermal vents, its biodiversity, and consequence of
deep sea mining on it.
huffingtonpost.co.uk

9. Tighten regulations on deep-sea mining
 Deep-sea mining may result in the destruction of seabed communities at or near the mining site,
offsite impacts due to the dispersion of toxic and particulate material in ocean currents and from sea
surface discharges, and due to accidents involving mining gear and support vessels.
 Potential negative impacts of deep-sea mining include
 Loss of habitat
 Degradation of habitat quality
 Decreased seafloor and/or water column primary production
 Modification of trophic interactions
 Decreased diversity
 Local, regional, or global extinction of endemic or rare taxa
 Deep-sea mining activities should not commence before measures are in place to protect deep-sea
ecosystems from adverse impacts
 Until a strict governance mechanism is set up and adhered to that allows for all countries to benefit
at an equal footing from deep seabed resources in areas beyond national jurisdiction is set up and
adhered to, there are also potential socio-economic consequences
Conclusion and criticism

10. Deep carbon export from a Southern Ocean iron-fertilized diatom bloom
Objectives
 This article discussed on rules of iron into the oceans in the face of
climate change.
Context
 Ocean Iron fertilization is the deliberate introduction of Fe to
the ocean surface to fuel a phytoplankton bloom.
 This is envisioned to increase biological production, which
benefit the oceanic food chain and hopes that of increasing
CO2 abstraction from the air.
 Fe is consider as a trace element required for photosynthesis
in all plants. It’s greatly insoluble in marine water and is
frequently the limiting nutrient for phytoplankton progression.
 Huge algal blooms can be formed by providing Fe to iron
scarce ocean waters.
www.atmosedu.com

11. Results
 Fe fertilization as a means to sequester CO2 from atmosphere to deep ocean, and to upturn oceanic
biological production which is probable in decline for climate change
 Fertilization may occur when weather brings wind blown dust from a long distances above the
ocean, or Fe rich mineral deposits are carried into ocean by glaciers, rivers and icebergs.
 Fertilization of the deep-sea by addition of Fe rich compounds has prompted diatom dominated
blooms escorted by considerable CO2 drawdown into the ocean surface.
 Growth of numerous diatom species displayed 97% Chl increase, and dropping was initiated by
massive death and swift sinking which was compensated by others species.
 50% of the bloom biomass sank far beneath a depth of thousand meter and that a considerable
portion is likely to have gotten the ocean floor. Thus, Fe-fertilized diatom blooms may act as carbon
sequester for timescales of spans in oceanic bottom water and in the sediments for longer .
 Sinking of accumulated cells and chains in the decease phase of diatom blooms similarly occurs in
the open Southern Ocean, both in natural and artificially manured blooms
 Findings recommended that Fe insufficiency is not only merely impacting ocean ecosystems, it also offer
a key tools to mitigate climate change as well.
 If phytoplankton convert all the NO3
- and PO4 in existence of Fe in the shallow mixed depth through the
whole “Antarctic Circumpolar Current” into organic carbon, the resulting CO2 scarcity could be
recompensed by uptake from the atmosphere
Conclusion and comments

12. Ocean Iron FertilizationRelated Article
Buesseler, K. O., Andrews, J. E., Pike, S. M., & Charette, M. A. (2004). The effects of iron fertilization on carbon
sequestration in the Southern Ocean. Science, 304(5669), 414-417.
Context
 The Southern Ocean plays a key role in the climate system, and is known as
the marine body utmost sensitive to climate change
 Phytoplankton bloom observed induced by naturally iron fertilization. With a
view to overcome some of the limitations of associated with temporary
experiments.
 The availability of iron limits have great impact on primary productivity and on
the associated uptake of carbon over huge areas of the deep-sea.
 Thus Fe plays an vital role in the earth carbon cycle, and alterations in its
supply to the ocean surface have a significant impact on atmospheric carbon
dioxide concentrations over glacial and interglacial cycles
Objectives
 To investigate o the effect of natural iron fertilization on carbon
sequestration in the Southern Ocean
“Iron fertilization of
its surface waters
during glacial times by
enhanced
dust deposition is a
scenario (known as
the ‘iron hypothesis’)
proposed to explain
lower atmospheric
CO2 during colder
climates”
(Martin, 1990).
Iron hypothesis

13. Results
 This result sheds new light on the effect of long-term fertilization by
iron and macronutrients on carbon sequestration, suggesting that
changes in iron supply from below as invoked in some palaeoclimatic
and future climate change scenarios may have a more significant effect
on atmospheric carbon dioxide concentrations than previously thought.
Conclusion and comments
 A large phytoplankton bloom was found over the study area in the Southern
Ocean, was consistent by Fe and major nutrients supply to water surface
from Fe-rich deep water beneath.
 Addition of iron results ten times higher carbon export at the investigation
areas.
 Carbon can be exported up to 1000 meters, POC content also increase as a
result of iron fertilization.
 The higher carbon sequestration efficacy of the natural bloom in contrast to
mesoscale iron adding experimentations arises from differences in the
sequestration efficiency ratio.
Carbon export at A3 and C11.Profiles
of 234Th activity at A3 (red lines) and
C11 (blue lines).