The relative role of ecological interactions and environmental variables on the population dynamics of marine benthic polychaetes

Abstract

In order to elucidate how ecological interactions drive the abundances of marine benthic polychaete populations and the role that environmental variables play in their dynamics, we examined long-term dynamics of winter abundance in 13 polychaete species from benthic samples obtained over 15 years (1993 to 2007) at Punta Coloso, northern Chile on the Pacific coast of South America. We examined the relative importance of density dependence, winter sea surface temperature (SSTW) and Southern Oscillation Index (SOI) on polychaete dynamics. All species studied showed conspicuous abundance oscillations, consistent with negative density-dependent population feedbacks. Model selection across a suite of population dynamic models showed that for six species, the best model included the effect of environmental variables, SSTW in the previous year, while the SOI index was the relevant variable in two polychaete species. A pure density-dependent model best explained the population dynamics of the remaining five species. Our results contrast with traditional approaches, which focus on the importance of abiotic factors in structuring marine benthic systems, and demonstrate the importance of theoretical synthesis and analysis to understand long-term dynamics in these ecosystems.