Disentangling the effects of El Niño on a population of the polychaete Sigambra bassi in the Bay of Ancón, Peru

摘要

The macrobenthic community in shallow soft-bottom areas in the Bay ofAncuf3n, Peru, is characterized by low biodiversity due to low oxygenconcentrations. During El Niuf1o (EN) events, higher water temperature andhigher concentrations of dissolved oxygen induce a temporary increase inbiodiversity. However, the structure and dynamics of the emergingmacrobenthic community and populations, especially the polychaete , varystrongly among events. The reasons for this variation are poorly understood,in particular the relative influence of abiotic versus biotic factors. Todisentangle how abiotic and biotic factors influence the different responsesof the population of , population models were developed based on detailedlong-term monitoring data, which include four El Niuf1o events. Theresults show that abundances are favored by abiotic environmentalconditions during EN, namely high temperature and dissolved oxygenconcentration, but these abiotic effects are modulated by different bioticprocesses. In two EN events with relatively similarly high temperatureanomalies (EN 1982-1983 and 1997-1998) different biological interactions(competition, predation, facilitation) and different species composition ofthe community resulted in different responses of the population of .