Sea turtles, sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the green sea turtle, loggerhead sea turtle, Kemp's ridley sea turtle, olive ridley sea turtle, hawksbill sea turtle, flatback sea turtle, and leatherback sea turtle. Sea turtle, any of seven species of marine turtles belonging to the families Dermochelyidae (leatherback sea turtles) and Cheloniidae (green turtles, flatback sea turtles, loggerhead sea turtles, hawksbills, and ridleys). Seven different species of sea (or marine) turtles grace our ocean waters, from the shallow seagrass beds of the Indian Ocean, to the colorful reefs of the Coral Triangle, and even the sandy beaches of the Eastern Pacific. WWFs work on sea turtles focuses on five of those species: green, hawksbill, loggerhead, leatherback and olive ridley. See more on worldwildlife.org

1. Ashish sahu
FSM-2019-20-04
KUFOS, Kochhi, Kerala
SEA TURTLE- IMPORTANCE TO
MARINE ECOSYSTEM, THREATS &
CONSERVATION
Submitted to,
Dr. Rajeev Raghvan

2. SEA TURTLE
Introduction Sea turtles are air-breathing reptiles with streamlined bodies and large
flippers. They are well adapted to life in the ocean and inhabit tropical and subtropical ocean
waters around the world. Although sea turtles live most of their lives in the ocean, adult females
have to return to beaches to lay their eggs. They often migrate long distances between feeding
areas and nesting beaches.
 Air breathing reptiles with streamlined body and large flapper.
 Found in tropical and subtropical waters.
 Cold blooded – need warmer waters. (Reptiles are ectothermic.)
 Evolved about 200 million years ago.
 Migrate long distances between Feeding areas and nesting.
 Long living organisms.
 Sea turtles are toothless, but have powerful jaws to crush, bite, and tear their food.
 Sea turtles are among the oldest creatures on Earth.
 Most sea turtles grow slowly and have a lifespan of many decades.
 generally not extremely fast swimmers.
 Usually, they cruise at around 0.9 to 5.8 mph (1.4 to 9.3 km/h), but have been found to
swim up to 22 mph (35 km/hr) when frightened.
Systematic position of sea turtle:
Kingdom: Animalia.
Phylum: Chordata.
Class: Reptilia.
Order: Testudines.
Suborder: Cryptodira.
Clade: Panchelonioidea.
Superfamily: Chelonioidea.
Families; Pancheloniidae, Cheloniidae, Dermochelyidae, Protostegidae.
Behaviour and habit
Sea turtles are generally found in the waters over continental shelves. After taking to the
water for the first time, males will not return to shore again. During the first three to five years of
life, sea turtles spend most time in the pelagic zone floating in seaweed beds. Green sea turtles in
particular are often found in Sargassum beds, a brown seaweed in which they find shelter and
food. Once the sea turtle has reached adulthood it moves closer to the shore. Females will come
ashore to lay their eggs on sandy beaches during the nesting season.
Diet:

3. Sea turtles feed on a wide range of animals and plants. They are mostly omnivorous in their
adult life.
 Most sea turtles are omnivores, meaning they eat both plants and animals. The only
herbivorous sea turtle is the green sea turtle, but they do not start out as herbivores. As
hatchlings, green sea turtles eat fish eggs, mollusks, and crustaceans. It is not until
adulthood that their diet switches exclusively to algae, seaweed, and seagrasses.
1. Green sea turtles- commonly found in sea grass meadows closer inshore as herbivorous
grazers.
2. The flat back turtle -Sea grass, marine invertebrates including molluscs, jellyfish and
shrimp fishes. It also consumes of soft coral, sea cucumbers.
3. The loggerhead – Bottom dwelling invertebrates, such as gastropods, bivalves, and
decapods. Other food items include sponges, corals, sea pens, polychaete worms, sea
anemones, insects, sea urchins, sea cucumbers, starfish, fish, and hatchling turtles
(including members of its own species).
4. Kemp's ridley- molluscs, crustaceans, jellyfish, algae or seaweed and sea urchins.
5. The olive ridley- predominantly carnivorous, especially in immature stages of the life
cycle. Animal prey consists of invertebrates.
FUNDAMENTAL LINK IN MARINE ECOSYSTEMS

4. Sea turtles are a fundamental link in marine ecosystems. They help maintain the health of
seagrass beds and coral reefs that benefit commercially valuable species such as shrimp, lobster,
and tuna. Sea turtles are the live representatives of a group of reptiles that have existed on Earth
and traveled our seas for the last 100 million years. Turtles have major cultural significance and
tourism value. Five of the seven species are found around the world, mainly in tropical and
subtropical waters. The remaining two species, though, have relatively restricted ranges: Kemp's
ridley is found mainly in the Gulf of Mexico and the flatback turtle around northern Australia and
southern Papua New Guinea.
Hawksbills help maintain the health of coral reefs. As they remove prey such as sponges from
the reef's surface, they provide better access for reef fish to feed. They also have cultural
significance and tourism value. For example, for local residents in the Coral Triangle, the flow
of visitors who come to admire turtles is a vital source of income.
Adaptations: -
Swimming: All species share features such as paddle-shaped limbs and a streamlined shape
with an enlarged shoulder girdle and well-developed pectoral muscles which aid in swimming.
Sea turtles are also excellent divers. Leatherbacks routinely dive to depths exceeding 1000 feet
in search of jellyfish. During long dives, blood is shunted away from tissues tolerant of low
oxygen levels toward the heart, brain, and central nervous system.
Respiration: Sea turtles are almost always submerged, and therefore, have developed an
anaerobic system of energy metabolism. Although all sea turtles breathe air, under dire
circumstances they may divert to anaerobic metabolism for long periods of time. When surfacing
to breathe, a sea turtle can quickly refill its lungs with a single explosive exhalation and rapid
inhalation. Their large lungs have adapted to permit rapid exchange of oxygen and to avoid
trapping gases during deep dives.
Metabolism: Sea turtles are known to have a reduced metabolic rate which allows them to
stay underwater for long periods of time before needing to resurface to breathe. They are also
equipped with enlarged lacrimal or tear glands modified to remove excess salts from body fluids.
They are able to live in seawater without the need for a freshwater source as they can obtain
sufficient water from their diet and from metabolising seawater.
Thermoregulation: A sea turtle’s large size leads to a low surface area to volume ratio, so the
heat exchange rate is low compared to total size. The thermoregulatory adaptations of leatherback
turtles in particular, such as a counter-current heat exchange system, high oil content, and large
body size, allow them to maintain a core body temperature higher than that of the surrounding
water (up to 18◦C above their surroundings), thereby allowing them to tolerate colder water
temperatures.

5. Navigation: The ability of some sea turtles to migrate in the open ocean between feeding and
nesting grounds sometimes separated by thousands of kilometres. Commonly held among the
suggested theories is that when hatchlings emerge, they are “imprinted” on the earth’s
geomagnetic field. Using their ability to differentiate magnetic field intensities and inclination
angles, they are able to migrate back to their natal beaches as adults.

6. Anatomy- Reptile of the Sea
 Internal and external skeleton.
 for protection and support.

7.  Plastron – lower part of shell.
 Carapace – upper part of shell.
 The carapace and plastron consist of two separate layers.
 One layer is composed of flattened bone plates that grow between and fuse with the ribs
as the turtle grows.
 The second layer is the keratin.
 Scales (or scutes) that protect the sea turtle and prevent water loss.
 Scutes are firm and flexible without being brittle.
 Marine turtles cannot retract body.

9. A Tough Shell……..
Epibionts
 The shell can do more than protect and streamline.
 Many other ocean organisms use sea turtle shells as a home or a feeding station.
 Small organisms, called epibionts, can live on the surface of a sea turtle’s shell.
 They can include barnacles, algae, and even small crabs.
 parasitic organisms like the marine turtle leech (Ozobranchus margoi)
 In fact, more than 100 different epibionts have been identified living on loggerhead sea
turtle shells.
 Thankfully for sea turtles, certain fish love to eat the epibionts—the sea turtle gets a
cleaning while the specialized fish swim away with a nice meal.

10. Senses in sea turtle:
Sensory adaptations help sea turtles survive in the ocean environment.
1. VISION
 Sea turtles spend most of their lives submerged in an aquatic environment, but they also
can spend significant amounts of time at the surface of the water because they require air
to breathe.
 In addition, new hatchlings and nesting females spend time, however brief, on the beach.
 Therefore, sea turtles have eyes adapted to see in both water and air.
 However, their eyes are best adapted for seeing well under the waves.
 Humans have a curved cornea that refracts
light and helps to see in the air.
 Corneas lose all ability to refract light when
submerged in water, , which causes the
unfocused view we see when opening eyes
while underwater.
 Underwater, fish have a cornea merely as a
protective barrier.
 All the refractive power of a fish's eye is
contained in their lens.
 Animals such as turtles that spend time in both
aquatic and air environments have eyes that combine these two eye types.

11.  Sea turtles have flat corneas and a nearly spherical lens adapted to their mostly aquatic
lifestyle.
 In the eye, cells called rods detect movement in dim light conditions and cells called cones
detect colored light.
2. HEARING
 No ears
 Sea turtle ears are much smaller than ours and though not visible on the outside of their
head, their ears allow them to hear vibrations in the water.
 Their ears are covered by a protective layer of skin called the tympanum.
 Underneath the tympanum is a layer of fat unique to sea turtles; freshwater turtles do not
have this feature.
 A 2014 study showed that both hatchling and juvenile loggerhead sea turtles hear and
respond to low-frequency sounds.
 This observation suggests that, like some whales, sea turtles are low-frequency specialists.
 More research needs to be done to further understand how and what sea turtles are hearing.
3. SMELL
 Sea turtles possess an acute sense of smell.
 Good sense of smell.
 It is thought that this well-developed sense of smell, along with vision, plays a role in a sea
turtles’ ability to locate prey.
 Being able to smell prey in murky or dark water.
 Smell is also believed to contribute to how female sea turtles find their way back to their
home beach to nest (see “Natal Homing” section below).
4. MAGNETIC SENSE
Sea turtles also have a sense that enables them to detect and utilize the magnetic field of
the Earth as a guide, although scientists do not fully understand how their magnetic sensitivity
works.
5. NATAL HOMING
Female sea turtles migrate thousands of miles, sometimes to the same beach where they were
born, in order to nest. This phenomenon is called natal homing

12. Scientists recognise seven living species of sea turtles, which are grouped into six genera. These
species include: the olive ridley (Lepidochelys olivacea), loggerhead (Caretta caretta), green
(Chelonia mydas), hawksbill (Eretmochelys imbricata), Kemp’s ridley (Lepidochelys kempii),
Australian flatback (Natator depressa) and leatherback (Dermochelys coriacea) turtle. Of the

13. seven species, the Australian flat back is the only one that isn’t either endangered or critically
endangered. All are found in coast of the maritime state of India.
1. Green sea turtle: Green turtles are the largest of all the hardshelled sea turtles, but have a
comparatively smaller head. They are large in size, attaining about 120 cm in length and
weighing about 136159 kg.
2. Hawksbill One of the smaller sea turtle species, the hawksbill turtle gets its name from its
narrow, elongated head which tapers sharply with a Vshaped lower jaw. The carapace is
orange, brown or yellow in colouration. Adult hawksbills measure about 76-91 cm in
length and weigh around 40-60 kg
3. Leatherback Largest among all the sea turtle species, leatherbacks get their name from the
unique shell composition that make it appear “leathery”. Leatherbacks are known to travel
great distances, and dive the deepest, when compared to other sea turtles. They growing up
to 170 cm in length and weighing up to 500 kg.
4. Loggerhead Adult loggerheads measure between 75 and 100 cm in length and typically
weigh up to 159 kg. Loggerheads are named after their exceptionally large heads. The
carapace is reddish-brown with a yellowish-brown in colour.
5. Olive ridley The olive ridley is the smallest of all the sea turtle species. It gets its name
from the olive green colouration of its carapace (shell). An adult typically measures
between 62 and 70 cm in length and weighs about 35-45 kg. Juveniles are charcoal grey in
colour, while adults are a dark greyish green.
6. Australian flat back The Australian flat back (Natator depressa) is endemic to the
continental shelf of Australia and is so called because of its flattened carapace. The adults
weigh about 200 kg.
7. The Kemp's ridley The Kemp’s ridley (Lepidochelys kempii) turtle is also known as the
Atlantic ridley turtle and is found in the Atlantic Ocean and the Gulf of Mexico. Adults
weigh about 50 kg and are about 60 – 90 cm in length and closely resemble olive ridleys

15.  Sea turtles don’t have sexual chromosome like mammals.
 Instead, their sex is determined by the temperature of incubation of the eggs, something
called TDS (Temperature-Determined Sex).
 Nests that were incubated at lower temperatures may create more males, while warmer
temperatures will increase the female's numbers.

17. Ecological importance
Sea grass needs to be constantly cut short to help it grow across the sea floor. Sea turtles
act as grazing animals that cut the grass short and help maintain the health of the sea grass beds.
Dune vegetation is able to grow and become stronger with the presence of nutrients from sea
turtle eggs, unhatched nests, eggs and trapped hatchlings. As the dune vegetation grows stronger
and healthier, the health of the entire beach/dune ecosystem becomes better.
Economic importance
 Sea turtle harvests worldwide are for food.
 Many parts of the world have long considered sea turtles to be fine dining.
 Sea turtles as a source of protein. Turtle eggs is used for consumption.
 Tortoiseshell, a traditional decorative ornamental material used in japan and china.
 The skin of the flippers is prized for use as shoes and assorted leather goods.
Valuation:
 Significant contribution to GDP
 Taxes paid to government
 Jobs and wages dependent on sea turtles.
 Jewellery, instruments, sunglasses or wall decorations.
 Recreation purpose.
Threats to sea turtles:
Artificial lighting: When a sea turtle hatches, its evolutionary instincts push it to move towards
the brightest light in view, which naturally would be the sun or the moon, leading them toward
the ocean horizon and into their new ecosystem. With the invention of the light bulb the hatchlings
become easily confused and turned around, few of them making successful treks to the ocean.
Studies support artificial light as the leading cause for hatchling disorientation, showing that in
1999, 51% of the nests studied showed signs of confusion with one-fourth of all the hatchlings
headed in the wrong direction.
Ocean plastic: Discarded plastic bags floating in the ocean resemble jellyfish, a common food
of sea turtles. If a turtle eats a plastic foil, it tends to clog the turtle's digestive system and results
in the animal dying. There have been many cases of dissection showing plastic foil and other
debris inside turtle’s stomachs and intestines.
Oil spills: Oil spills are particularly dangerous to sea turtles. Sea turtles are still at risk when they
surface for air, where oil can get in their eyes, skin, and lungs which can lead to significant health
problems. Oil is also a cause for the death of sea grass. Eggs is still at risk due to either oil in the
sand or contamination. If the eggs in the nest have contact with oil while in the last half of their

18. incubation phase, the rate of hatchling survival sharply decreases and those that do survive have
a greater chance of physical deformities.
Marine pollution: Most dangerous ocean pollutants include toxic metals, fertilizers, untreated
waste, chemicals and a variety of petroleum products. Breeding season is in particular a dangerous
time for sea turtles due to the pollution of beach nesting sites. Contamination of their diet can
lead to disruption of digestion as well as physical injury of the sea turtles’ digestive tracts. A
study in 1994 at Atlantic coast, 63% of hatchlings surveyed had been found to have ingested tar
leading to oesophageal swelling that can dislocate the intestines and liver leading to serious
buoyancy issues as well as excessive swelling.
Magnetic interference: Ferrous metal wire mesh screens are commonly used to protect sea turtle
nests from predators' excavating and devouring the eggs and hatchlings. A new concern is that
nestlings' delicate magnetic sense may not develop normally in the presence of the magnetic field
interference from these steel mesh cages. Gravid turtles or their hatchlings may also be affected
by the presence of magnetic fields arising from power cables, iron debris, steel seawalls or other
human activities that locally modify earth's magnetic field.
Fishing: Long line, trawl, and gillnet fishing are three types of fishing with the most sea turtle
accidents. Deaths occur often because of drowning, where the sea turtle was ensnared and could
not come up for air. Another dangerous aspect of fishing that is common is when sea turtles
inadvertently swallow sharp hooks, which can get stuck within the soft tissue of the throat and
stomach, or damage vital organs and intestines. According to an article in AAAS & Science, over
8 million sea turtles have died over the past twenty years due to injuries caused by being
accidentally caught by fishing boats.
Sea turtle bycatch – a global issue:
The problem of the seven species of sea turtles that inhabit our planet’s seas, the International
Union for the Conservation of Nature (IUCN) Red List of Threatened Species classifies the
hawksbill and Kemp’s ridley as “Critically Endangered”, the green as “Endangered”, the olive
ridley as “Vulnerable”, and certain sub-populations of loggerhead and leatherback as “Critically
Endangered”, while the flatback turtle is currently considered as data deficient. While sea turtles
face a growing number of human-induced threats, including marine pollution and loss of nesting
habitat due to coastal development or degradation, incidental capture of turtles – also known as
Hawksbill turtle hooked on a longline. Hawksbills are
particularly susceptible to entanglement in gillnets and
accidental capture on fishing hooks.

19. bycatch - in fisheries poses the single most serious threat to marine turtles worldwide1. Bycatch
occurs in both large-scale and small-scale fisheries (SSFs) using trawls2, longlines3,4,
gillnets5,6, trammel nets, seine nets, and many other gears. According to one 2004 study, pelagic
longline fleets from 40 countries set an estimated 1.4 billion hooks in the water, the equivalent of
3.8 million hooks every day7. Trained observers working on longline fleets and other large scale
industrial fishing vessels, have generated a wealth of data through a focus on these fisheries to
avoid further sea turtle population declines3,7,8. The cumulative impacts of these large-scale
fisheries are of high conservation concern, and have driven the mobilization of resources to
monitor and reduce sea turtle bycatch through collaboration between NGOs, researchers,
governments, the fishing industry, and regional fisheries management organisations (RFMOs)9.
However, estimating rates of bycatch in small-scale fisheries (SSFs), which operate
predominantly in nearshore waters and use a range of gear types including gillnets, trammel nets,
and traps, is much more challenging. Several studies show that turtles are less likely to survive
entanglements in gillnets than trawls or longlines, leading to a higher mortality rate10,11. In
2014, 85% of the world’s motorized fishing vessels were under 12m in length12, too small to
host on-board observers. SSF fishing effort is also widely dispersed, making it difficult to sample
a representative portion of the fleet with interviews or fish landing site inspections13.
Furthermore, small-scale fisheries are most prominent in developing countries where resources
are limited for monitoring of fisheries5,14. Recent studies indicate that turtle bycatch in small-
scale (gillnet) fisheries may be responsible for as much if not more sea turtle mortality than large-
scale fisheries2,10,15,16. As such, finding effective ways to assess, monitor and mitigate bycatch
in SSF should be a high conservation priority. Without efforts to reduce bycatch in both large and
small-scale fisheries, many marine turtle populations face a serious threat of extinction.
Global distribution of turtle bycatch: Hotspots where mitigation efforts should be focused:
For conservation management purposes, sea turtle populations around the globe have been
categorized into Regional Management Units (RMUs) 17 that take into account information from
genetic, nesting, mark-recapture and satellite telemetry studies. The RMU framework allows
researchers and conservation managers to assess the risk that bycatch poses to turtle populations
around the world on a biologically meaningful scale. For example, high rates of bycatch of
loggerhead turtles in fisheries off the coast of Peru where they feed, could be the cause of reduced
numbers of reproductive females on Australian coasts, where they nest. A 2013 study of over
1,800 sea turtle bycatch records from 230 sources found that the highest bycatch rates occurred
in the East Pacific, Northwest and Southwest Atlantic, and Mediterranean regions11. However,
these were also the regions that contributed the highest volume of data. Over 60% of this data
comprised records from longline fisheries11. While the bycatch occurring in these fisheries is of
serious conservation concern, the authors point out that “data poor” coastal areas off Africa,
within the Northern Indian Ocean and throughout Southeast Asia are also known to host
numerous nesting colonies of turtles from RMUs that are under high threat from small-scale
fisheries11,13. As such, the magnitude of the threat posed by small-scale gillnet fisheries in these

20. areas where so little research on bycatch has occurred may not be accurately reflected in the map
to the right.
Global warming: This rise in sea levels has been a factor in the loss of beach, which for sea
turtles means less nesting area. As the overall temperature of the earth rises, so does the
temperature of the sand, which diminishes the rate of hatchling survival. The temperature of the
sand also affects gender, as higher temperatures have been shown to yield more female hatchlings.
Changes in climate also influence currents and change the number and location of prey species.
Water that is too warm can also cause coral bleaching, which is detrimental to reefs that are
essential to certain species, such as the Hawksbill sea turtle.
Disease: A disease known as fibropapillomatosis manifests itself in turtles through external
tumours. These tumours often grow to be so large that they hinder a sea turtle’s ability to see, eat,
and swim, therefore rendering the sea turtle unable to survive. the causes of this disease are not
clear, many believe the source to be viral. These tumours are either smooth or contain pointed
projections and they are red, pink, grey, black, or purple in colour.

22. Law & policy (international):
International union for the conservation of nature and natural resources as the first
international forum (1963) for sea turtle research and conservation. In 1973, the endangered
species act was passed, providing protection for all sea turtle species. NOAA national marine

23. fisheries service (NMFS) and the U.S. Fish and wildlife service (USFWS) administer the
endangered species act with respect to marine turtles. NOAA fisheries has the lead for the
conservation and recovery of sea turtles when turtles are at sea. The USFWS has the lead when
sea turtles are on nesting beaches.
Law & policy (India):
The Indian Wildlife Protection Act (1972) lists all species of marine turtles in Schedule I,
thereby offering them the highest degree of protection. Under international law, India is a
signatory to CITES (Convention on International Trade in Endangered Species) and the
Convention on the Conservation of Migratory Species of Wild Animals (CMS). CITES regulates
international trade on sea turtles and their products but does not protect habitat or control other
threats to sea turtles. And according to the CMS, all seven species of sea turtles require
international cooperation for their conservation. But here again, conservationists feel that not
enough provision has been made for effective protection and conservation.
Last note:
 Beach management and hatchery programmes
 Education and Awareness.
 Rehabilitation.
 By catch reduction.
 Reducing Overharvesting and Illegal Trade.
 Protecting Marine Turtle Habitat.
 Minimizing Climate Change Impacts.
 Satellite Tracking.
Turtle or tortoise: There is some confusion about the usage of terms 'turtle' and 'tortoise'.
Basically, the usage of these terms differs in accordance to the language in question. In British
English, the term 'turtles' is used for those species which are found in the sea, and 'tortoises'
for those inhabiting the land. In American English, the term 'turtles' is used as a general term
to all the species belonging to this family; and the sea-dwelling species are specifically referred
to as 'sea turtles'.
Reference
• "Marine Turtles." Office of Protected Resources. NOAA Fisheries, 11 Nov 2010. Web. 8
Dec 2010.
• Hirayama, R., & Tong, H. (2003). "Osteopygis (Testiness: Cheloniidae) from the Lower
Tertiary of the Ouled Abdoun phosphate basin, Morocco.
• Roy D Silva Last Updated: January 19, 2012.
• NOAA Education Resources: Sea Turtles Collection.
• http://seaturtlesofindia.org/?page_id=462.
• Turtle excluder device From Wikipedia, the free encyclopaedia.

24. • http://seaturtlesofindia.org/?page_id=180.
 Animal Diversity Web, University of Michigan Museum of Zoology
 Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission
 National Marine Fisheries Service, National Oceanic and Atmospheric Administration
 Sea Turtle Conservancy
 U.S. Fish & Wildlife Service
THANK YOU…….