Grantee Research Project Results
2002 Progress Report: Evaluating Multiple Stressors in Loggerhead Sea Turtles: Developing A Two-Sex Spatially Explicit Model
EPA Grant Number: R829094Title: Evaluating Multiple Stressors in Loggerhead Sea Turtles: Developing A Two-Sex Spatially Explicit Model
Investigators: Wyneken, Jeanette , Crowder, Larry B. , Snover, Melissa , Epperly, Sheryan
Current Investigators: Wyneken, Jeanette , Crowder, Larry B. , Epperly, Sheryan
Institution: Florida Atlantic University - Boca Raton , University of California - Santa Cruz , Duke University
Current Institution: Florida Atlantic University - Boca Raton , Duke University , National Marine Fisheries Service
EPA Project Officer: Packard, Benjamin H
Project Period: November 15, 2001 through November 14, 2004 (Extended to November 14, 2005)
Project Period Covered by this Report: November 15, 2001 through November 14, 2002
Project Amount: $349,421
RFA: Wildlife Risk Assessment (2001) RFA Text | Recipients Lists
Research Category: Biology/Life Sciences , Ecological Indicators/Assessment/Restoration , Aquatic Ecosystems
Objective:
The objectives of this research project are to: (1) synthesize the new empirical data available; (2) produce a two-sex, spatially explicit model of North Atlantic loggerheads; and (3) evaluate and predict the impacts of multiple environmental stressors on these populations. Our new modeling framework will allow us to integrate the effects of multiple stressors at the appropriate spatio-temporal scale, and address contemporary management alternatives. This approach to wildlife risk assessment for highly migratory, long-lived species may subsequently be extended to other protected species. Inhabitants of coastal systems often are sentinels for ecosystem health. The need for wildlife risk assessment now is clear, and particular attention should be given to sentinel species. Loggerhead sea turtles are ideal sentinels for the coastal zone because they are both terrestrial and aquatic, and their nesting beaches are experiencing increased threats from high-density development. Loggerheads encounter fishing gear and experience damage from concentrated recreational boating in particular locations and seasons. After the juveniles return from the open ocean at age 8-11, loggerheads spend prolonged periods in the specific ecosystems (e.g., estuaries or coastal reefs while maturing; they first reproduce at about age 30), and adults show fidelity to the same feeding grounds when not at breeding grounds. Loggerhead turtles spend most of their lives immersed in oceanic and estuarine waters; they are divers that feed primarily upon mollusks, crustaceans, and fish while they are submerged. However, like seabirds, they are obliged to return to land to lay eggs.
Scientists have access to the adult females and their eggs and hatchlings on land, as well as the adult males and immature turtles in the water via a number of mark and recapture studies. The most robust of these data sets have been loaned to us for inclusion in our models and for indepth analyses. Long-term mark and recapture data, basic demographic data, and systematic documentation of some life history parameters have been used to establish and test management plans. Yet, management alternatives frequently address only a particular life stage, sex, habitat, or spatial locations. Therefore, assessment of the integrated population-level responses, and consideration of management tradeoffs, will require a new generation of population models that can accommodate multiple environmental stressors.
Progress Summary:
Our hypothesis is that North Atlantic loggerhead sea turtle (Caretta caretta L.) populations respond to the integrated effects of multiple environmental stressors that differentially affect different age classes, sexes, and subpopulations. These stressors also vary in magnitude depending upon the spatial habitat in which they occur. Management alternatives often only address a particular life stage, sex, habitat, or spatial location. Therefore, assessment of the integrated population-level response, and consideration of management tradeoffs, will require a new generation of population models.
Our approach is synthetic, drawing from existing pools of empirical data and
adding new data so that the vulnerabilities of specific life stages and/or subpopulations
can be anticipated using models and management techniques adjusted proactively.
Additionally, the new models we propose may be used to test whether existing
management practices are sufficiently robust to accommodate multiple environmental
stressors. We have accomplished phase 1 of our plan to
collate and summarize long-term data to update our understanding of the North
Atlantic loggerhead population structure in a spatially explicit way. The new
model will be a two-sex model because the sex ratio appears to be skewed toward
females and because males and females may differ in migratory pattern and their
fidelity to nesting grounds. Our data on sex ratio to date, which strongly is
skewed towards female, make this spatially explicit model even more important
than previously thought.
Loggerhead sea turtles are considered threatened under the U.S. Endangered Species Act, and their population demographics reflect the effects of stressors that include a history of terrestrial habitat loss, terrestrial and aquatic habitat degradation, and direct hunting and nontarget bycatch in several fisheries ranging over whole ocean basins (see Figure 1). Specifically, beach development, photopollution, beach renourishment, and beach armoring have resulted in loss of nesting habitat, compromised incubation environments, and reduced hatchling production (Salmon, et al., 1995; Lutcavage, et al., 1996; Schroeder, 1997). These threats continue, but new threats include increases in incubation temperatures (further skewing sex ratios, which are defined by incubation temperature) and loss of nesting habitat to rising sea levels on developed and armored beaches. In the marine system, accumulation of pollutants such as plastics, heavy metals, environmental estrogens, and oil products in pelagic nursery and demersal coastal habitats, as well as rapid degradation of marine and estuarine environments by nutrient runoff, have the potential to further reduce loggerhead populations.
(a) | (b) | (c) |
Figure 1. (a) Loggerhead Laparopscopy, (b) Loggerhead After Laparoscopy, and (c) Loggerhead Ovary.
Future Activities:
In the coming year, we will update and partition the mortality associated with several well-documented environmental stressors (including photopollution, beach renourishment, boat interactions, and fishery interactions). Additionally, we will expand our new comprehensive data to describe the sex ratios of hatchlings throughout the entire season from multiple beaches encompassing both subpopulations. We also will document hatchling survivorship following migration past predator-rich nearshore waters for multiple beaches representing the subpopulations.
Journal Articles:
No journal articles submitted with this report: View all 50 publications for this projectSupplemental Keywords:
loggerhead sea turtles, multiple stressor, ecosystem health, wildlife risk assessment., RFA, Economic, Social, & Behavioral Science Research Program, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Toxicology, Ecosystem/Assessment/Indicators, Ecosystem Protection, exploratory research environmental biology, wildlife, Ecological Effects - Environmental Exposure & Risk, Monitoring/Modeling, Zoology, Environmental Statistics, Ecology and Ecosystems, Ecological Risk Assessment, Ecological Indicators, ecological exposure, risk assessment, predicting risk, spatial distribution, demographic, contaminants, demographic data, stressors, loggerhead sea turtles, multiple stressors, Wildlife Risk Assessment, wildlife populations, stress effects on wildlife populations, two-sex spatially explicit model, spatial demographic model, sensitive populationProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.