Disentangling the effects of El Ni?o on a population of the polychaete iSigambra bassi/i in the Bay of Ancón, Peru

摘要

The macrobenthic community in shallow soft-bottom areas in the Bay ofAncón, Peru, is characterized by low biodiversity due to low oxygenconcentrations. During El Niño (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 Sigambra bassi, 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 S. bassi, population models were developed based on detailedlong-term monitoring data, which include four El Niño events. Theresults show that S. bassi 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 S. bassi.