Long-Term Climate Forcing in Loggerhead Sea Turtle Nesting

Abstract

The long-term variability of marine turtle populations remains poorly understood, limiting science and management. Here we use basin-scale climate indices and regional surface temperatures to estimate loggerhead sea turtle (Caretta caretta) nesting at a variety of spatial and temporal scales. Borrowing from fisheries research, our models investigate how oceanographic processes influence juvenile recruitment and regulate population dynamics. This novel approach finds local populations in the North Pacific and Northwest Atlantic are regionally synchronized and strongly correlated to ocean conditions—such that climate models alone explain up to 88% of the observed changes over the past several decades. In addition to its performance, climate-based modeling also provides mechanistic forecasts of historical and future population changes. Hindcasts in both regions indicate climatic conditions may have been a factor in recent declines, but future forecasts are mixed. Available climatic data suggests the Pacific population will be significantly reduced by 2040, but indicates the Atlantic population may increase substantially. These results do not exonerate anthropogenic impacts, but highlight the significance of bottom-up oceanographic processes to marine organisms. Future studies should consider environmental baselines in assessments of marine turtle population variability and persistence.

Active dispersal in loggerhead sea turtles ( Caretta caretta ) during the ‘lost years’

“…Basin-level differences in environmental and oceanographic conditions can affect population dynamics, access to resources, growth rates and age at maturity [52]. Bailey [18] reinforced this basin-level comparison for leatherbacks (Dermochelys coriacea), suggesting that the processes which drive foraging success may strongly shape the conservation status of conspecific populations.…”

“…The NPSG causes surface convergence and retention of biomass and debris [52]. Various studies have described this feature, often called the 'great North Pacific Garbage Patch' or 'Eastern Garbage Patch' [57].…”

Forecasting ocean warming impacts on seabird demography: a case study on the European storm petrel

“…Wintering storm petrels are thought to move to the Alboran Sea (Soldatini et al 2014), a particularly nutrientrich area that benefits from currents inflowing from the Atlantic Ocean (Agostini & Bakun 2002, Reul et al 2005, Renault et al 2012. This is a first attempt at a deeper analysis of the demography of the Mediterranean storm petrel, considering population growth as a function of oceanographic conditions (Van Houtan & Halley 2011). Some demographic traits of the storm petrel were described in previous studies (Sanz-Aguilar et al 2008, Soldatini et al 2014, but information on senescence and age effects on the species' demography is still lacking.…”

Assignment of nesting loggerhead turtles to their foraging areas in the Northwest Atlantic using stable isotopes

“…Concern was raised when nesting activity in one of these NWA populations declined markedly from 1998 to 2007 (Witherington et al 2009); however, an increase in nesting numbers has been reported in recent years (Van Houtan and Halley 2011). Anthropogenic threats (Jackson et al 2001, Witherington et al 2009, Finkbeiner et al 2011) and changing oceanographic conditions (Chaloupka et al 2008, Saba et al 2008, Van Houtan and Halley 2011 have been proposed as the main drivers of fluctuations in sea turtle abundance. Because these factors may change depending on geographic location (Kot et al 2010 and references therein), efforts to identify foraging grounds of sea turtles are vital to understand spatial and temporal fluctuations in nesting numbers.…”