Vol.2, No.3, 109-114 (2012) Open Journal of Ecology http://dx.doi.org/10.4236/oje.2012.23013 Effect of localized oil spills on Atlantic loggerhead population dynamics Margaret-Rose Leung 1 , Melissa Marchand 2 , Samantha Stykel 3 , My Huynh 4 , José D. Flores 4,5* 1 Department of Mathematics, Oregon State University, Corvallis, USA 2 Department of Mathematics, California State University Bakersfield, Bakersfield, USA 3 Department of Mathematics, Luther College, Decorah, USA 4 Department of Mathematics, Arizona State University, Tempe, USA 5 Department of Mathematics, The University of South Dakota, Vermillion, USA; * Corresponding Author: jflores@usd.edu Received 30 April 2012; revised 2 June 2012; accepted 30 June 2012 ABSTRACT The purpose of this study is to analyze the population dynamics of loggerhead sea turtles (Caretta caretta) affected by localized oil spills. Methods include development of a spatial, stage- classified matrix model parameterized for the following primary loggerhead populations: Gulf of Mexico, western North Atlantic Ocean, and Florida peninsula. Oil spills are simulated de- terministically in each population's nesting re- gion, with 1) oil-induced mortality ranging from 25% to 100% and 2) stage classes affected either proportionally or equally. A transient sensitivity analysis was performed to determine the para- meters most influential to the population growth rate. Results suggest that increased protection and understanding of young sea turtles found in the Sargasso Sea is essential to the survival of the species. In addition, findings provide in- sights into the population dynamics of the At- lantic loggerhead turtles and identify conserva- tion measures appropriate in each oil spill case. Keywords: Loggerhead Sea Turtle; Oils Spill; Matrix Model; Simulations; Population Ecology 1. INTRODUCTION The loggerhead turtle (Caretta caretta) is one of six endangered sea turtles in the Atlantic Ocean threatened by human activities [1]. One example of human impact on the population is frequent oil spills in the Gulf of Mexico and along the Florida peninsula [1]. On April 20, 2010, the explosion of the Deepwater Horizon oil rig resulted in a major oil spill that threatened the logger- head population [2]. Understanding the effect of oil spills on the population dynamics is of critical importance for the preservation of the species; however, data regarding the mortality rates of turtles exposed are sparse. While the weathering of specific crude oil compounds has been studied [3,4], it is unknown which of these, if any, are particularly toxic to the loggerhead and other wildlife. The loggerhead population is declining and mortality of adults and large immatures appears to be a key factor [5-7]. Adult turtles lay eggs on nesting beaches in the Gulf of Mexico, Florida peninsula, and Carolina shores. Hatchling turtles disperse to the Sargasso Sea, and then return to coastal regions after approximately nine years. Once mature, turtles nest on the beaches where they hatched [1]. Existing models of loggerhead turtles focus on the stage classes most sensitive to long-term population growth. Crouse et al. [5] published one of the first mo- dels in 1987: a stage-classified matrix parameterized with data collected by Frazer in 1983 [8]. In 1994, Crowder et al. [6] developed a model to analyze the im- pact of turtle excluder devices (TEDs) on the population of turtles that come in contact with trawl fisheries in the southeastern United States. In 2003, Heppell et al. [7] used newer data to create two matrix models in hopes of bounding the true values for survival parameters and stage durations. We are not aware of any published mo- dels of the effect of oil spills on loggerheads. However, following the 1989 Exxon Valdez catastrophe, Reed et al. [9] modeled oil’s effect on migrating fur seals and ex- amined heuristic oil-induced mortality rates ranging from 25% - 100%. Our research is motivated by the potential impact of the Deepwater Horizon oil spill on loggerhead turtles in the western North Atlantic Ocean. We have developed a system of stage-classified, spatial matrix models whose survival parameters can be modified to simulate oil spills of varying regions and initial toxicities. We did this by creating separate models for each primary nesting region Copyright © 2012 SciRes. OPEN ACCESS