1. Conservation and Ecology of Marine Reptiles
MARE 490
Dr. Turner
Summer 2011

2. Turtles in Marine Ecosystems
Sea turtle populations severely declined
Many substantially harvested before European contact with Caribbean
Difficult to determine past roles due to :
“Shifting Baseline Syndrome”

3. Shifting Baseline Syndrome
“You have an absolutely unique genetic condition known as "Homer Simpson" syndrome.” Dr. Julius Hibbert
Use of inappropriate baselines to assess population change
Usually based upon “recent levels” or levels present at “British Invasion”
Example – hawksbills heavily taken for shells long before they were recorded

4. Ecological Roles Important?
1. Ecosystem function
2. Understanding of environmental effects
3. Meaningful goals of conservation & management

5. Ecological Roles Important?
1. Ecosystem function
What has been lost – consumers
Fishing down marine foodwebs
Historic Overfishing/Recent collapse

6. Ecological Roles Important?
2. Understanding of Environmental Effects
Past or present environmental changes effect populations of sea turtles
Temperature – hatchlings
timing of nesting
Currents – migrations, 1° production
Habitat loss – nesting beaches, foraging areas

7. Ecological Roles Important?
3. Meaningful goals of conservation & management
From – single-species management
To – Ecosystem-based fishery management
Lack of information – how many sea turtles required for a population to be ecologically important

8. Return of the Chelonii
"Oh Jar Jar, everyone hates you but me.“ – Comic Book Guy
Difficult to conceive large numbers of sea turtles in past oceans
Estimates: fold decrease in last years
Would have had very significant effects/impacts upon marine ecosystems

9. Significant Effects
Consumers – crustaceans, jellyfish, seagrass, seaweed
Prey – fish, sharks, birds, whales
Competitors - fish
Hosts (parasites)
Substrates (epibionts) – barnicles, algae
Nutrient transporters – connectivity
Habitat modifiers - seagrass

10. Case Studies Ecological role of sea turtles as consumers
Caribbean Green – herbivore (seagrass)
Caribbean Hawksbill – carnivore (sponges)

11. Caribbean Green Turtle
Cayman Islands not inhabited by people but turtles exploited by visitors
– 13,000 turtles/yr
1790 economically extinct
1830 – econ extinct off Cuba
1890 – Miskito Cays
1901 – urged rearing program
How high were pre-exploitation numbers?
Past records say million

12. Preexploitation Populations
Typically regulated by food limitations
Carrying capacity (K) would be a maximum estimate of population size
Could use seagrass beds (Thalassia) to determine preexploitation carrying capacity
Green only significant sea grass consumer since Dugongid extinct in Pleistocene

13. Survey Says!
Based upon estimates of intake and productivity – 660 million green turtles
Dependent upon grazing variability probably ranged from million
Current estimates represent 3-7% of preexploitation levels

14. Seagrass Communities Thalassia testudinum - Turtle grass
Typically long (30cm) and covered with epiphytes/bionts
Low grazer effects – few/no herbivorous consumers

15. Grazer Effects Reduced epibionts
Moderate disturbance – “Intermediate disturbance hypothesis”
Reduced sediment deposition – more aquatic habitat
Deposition could significantly change habitat structure
Mass mortality in 1980’s

16. Caribbean Hawksbill Turtle
Preexploitation/expoitation records not as well known
Estimated current population ≈ 27,000
Can use a similar model of food limitations
Use sponges (Chondrilla) to determine preexploitation carrying capacity

17. Spongeworthy
Estimates of abundance, energy content, & assimilation efficiency
Used intermediate models between green (herbivore) & loggerhead (carnivore)
Sponge wet mass shows carrying capacity for more than recorded decline

18. Survey Says! Documented decline in last 100 yrs – 75-98%
Estimated preexploitation levels at 540,000
conservative estimate – 95% decline
Levels high enough to have significant effect upon structuring of coral reef systems

19. Office Space
Hawksbills can effect space competition among sponges and Scleractinian corals
Sponges often superior competitor
Also competition among sponge species

20. Caribbean Situation
Why extensive coral populations in Caribbean as compared with sponges in postexploitation hawksbill ecosystems?
Shift in other species – redundancy in web
Can mask the effect of species removal
Fishing effects on spongivorous fish species now becoming depleted

21. Conclusions
1. All species of sea turtle once extremely abundant millions to tens of millions
2. Past populations consumed large quantities of prey
3. Virtual ecological extinction of sea turtles have resulted in significant changes to structure & function of marine ecosystems