Conservation and Ecology of Marine Reptiles

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Conservation and Ecology of Marine Reptiles MARE
494 Dr. Turner Summer 2007
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Foraging Ecology Nutrition
Role of sea turtles in marine ecosystems Understa
nding of quantitative aspects of diet
selection digestive processing nutrition Coordi
nate population structure food web analysis
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Biomass Pyramids Transfer of energy
Whoa, slow down there maestro. There's a New
Mexico? C. Montgomery Burns
Food chain efficiency (gross ecological
efficiency)
Energy to next trophic level Energy received
from lower trophic level

2 of light E-gt organic substance
(autotrophs) 80-95 lost at each transfer
(trophic level)
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Ecosystem Energy Flow
500,000 units of solar E
2 transfer
1 unit of human E converted to human mass
10 transfer
10,000 units
10 units
1,000 units
100 units
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E!
Where did the E go?Why is transfer efficiency so
low?
Loss due to incomplete transfer among trophic
levels
1) Not eaten (evades or dies) 2) Inefficient
conversion E P R W
E ingested energy P secondary production R
respiration W waste
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First name Mr, middle name period, last name E
Quit your Jibba Jabba fools! Mr. T
E P R W
Assimilation efficiency (A) (P R)
P Secondary Production growth, fat storage,
birth R Respiration energy lost through
respiration
Assimilation efficiency the percentage of what
is initially consumed that becomes incorporated
into the consumer
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Gonna' teach this sucka a lesson!
As a kid, I got three meals a day. Oatmeal,
miss-a-meal and no meal Mr. T
Assimilation efficiency affected by 1) Food
quality 2) Amount of food 3) Age of consumer
Thereforeassimilation is opposite of excretion
(waste)
E A W
Energy available to the consumer is 1 a function
of assimilation efficiency
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Foraging Ecology
Tremendous gaps in knowledge Foraging habitat
typically separate from nesting juvenile
habitats How do we determine diet in protected
species? Feces pellets Stomach
lavage Biochemical techniques Stable
isotopes Fatty acids
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Foraging Ecology
Some sea turtles have a crop (Pacific
Green) sac-like structure between esophagus
stomach Allow for collection of relatively
undigested prey
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How Do We Track Diet?
In past studies, foraging ecology measured
with - Direct observation - Stomach contents -
Scat analysis Each have inherent
difficulties/biases - often biased by large,
hard components - underestimates small, soft
prey
Alternative approaches sought to overcome the
limitations of past studies
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Stable Isotopes and Fatty Acids
Require small tissue amounts - approximately 1
gram Use extensively in other fields Overcome
biases Longer foraging window weeks to months
Can be used to retrospectively determine diet
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Stable Isotopes
Carbon and nitrogen generally used (sulfur
recently) - Both abundant throughout
nature Values expressed as ratios of two
isotopes - 13C/12C or 15N/14N d Can
determine primary producer (CS) - Organic
material has isotopic signature trophic
level of feeding (N)
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Stable Isotopes
Based upon principle of Fractionation Each
time stable isotope is metabolized there is
Fractionation (do not participate equally
bias toward lighter)
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Fractionation
12C
12C
12C
C
13C
13C
13C
-20
-19
-18
-17
Est. Value
1
1
1
14N
14N
14N
N
15N
15N
15N
10
7
13
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Est. Value
3
3
3
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? 13Corigin of organic matter
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-20
Fractionation of Carbon? 1 ppt per Trophic level
-9
-21
-10
-22
Phytoplankton
Seagrass
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?15NTrophic position of consumer
Fractionation of Nitrogen? 3-4 ppt Per Trophic
level
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SHARKS!
14 12 10 8 6
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Turtles
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Crabs
?15N
Shrimp
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diatoms
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-22 -20 -18 -16
?13C
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What are Fatty Acids
Whoo Hoo, look at that blubber fly Homer
Simpson
Largest components of lipids (fat
molecules) Three fatty acids glycerol
backbone triacylglyceride (TAG) Saturated
no double bonds Monounsaturated one double
bond Polyunsaturated more than one double
bond PUFAs Polyunsaturated Fatty Acids
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PUFAs
Prevalent in most marine organisms Highly
conserved and abundant Cannot be synthesized de
novo in consumers Essential for life processes
Must be obtained exclusively from dietary
sources Represent natural dietary tracers in
marine organisms
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Stable Isotope Fatty Acid Analyses
You Are What You Eat
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Green Feeding Ecology
Juveniles in pelagic stage thought to be
omnivorous to carnivorous Associated with
Sargassum mats? Known to feed on jellies
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Green Sea Turtles
Empirical evidence of difference in pelagic vs.
neretic feeding ecology?
RS1 smaller RS3 larger
Seaborn et al. 2005
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Green Sea Turtles
Enter neretic habitat and shift to herbivorous
diet 20-25 cm (Atl) 35 (Hawaii) Why herbivorous?
Lower trophic level higher energy Niche Low
assimilation efficiency Either seagrasses
(Caribbean) or seaweeds (Hawaii)
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Hawaiian Green Sea Turtles
Feed on up to 56 species of algae typically
9 Green, red, Brown Feed on several
introduced species Minimal feeding on seagrass
(Halophila) invertebrates (jellies sponges)
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Hawaiian Green Sea Turtles
Low/no growth in several regions Poor food
quality? Assimilation efficiency?
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Loggerhead Feeding Ecology
Juveniles associated with Sargassum Current
fronts mixture of drift material algae,
detritus, insects, crustaceans Rely upon jellies
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Loggerhead Sea Turtles
Adults feed in benthos Primarily sea pens
crustaceans
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Hawksbill Sea Turtles
Juveniles again with the Sargassum Carnivorous
pelagic life history Recruit to neretic habitat
20-25cm 35cm similar to greens
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Hawksbill Sea Turtles
Adults gt95 of diet urchins, crabs, jellies -
rare Some soft coral feeding Sponge nutrition
thought to be low but contain high number of
endosymbiotic algae Produce chemical toxins
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Kemps Ridley
Juveniles Sargassum, Yes Sargassum Recruits/adu
lts primarily crabs also molluscs, fish,
shrimp Thought to scavenge shrimp trawling
bycatch not thought to include dead-turtle
bycatch
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Olive Ridley
Juveniles Sarg..No, really? Are you sure? Not
known Recruits/adults primarily salps fish
- also molluscs crustaceans Little known
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Flatback
Juveniles planktonic (larvae) benthic
(corals, molluscs, bryozoans) Recruits/adults
jellyfish soft-bodied invertebrates (sea pens
soft corals)
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Leather Back Kotter
Most pelagic of sea turtles Foraging patterns
dependent upon distribution of prey jellies,
ctenophores, salps accumulate along convergent
zones Feeding not size dependent jellies not
ontogenetic feeding shift
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Leather Back Kotter
Also known to feed on squid Interact with
long-line fisheries using squid as bait