Evaluating the impacts of El Nino events on a marine bay ecosystem based on selected ecological network indicators

摘要

El Nino events have great impacts on marine ecosystems worldwide, ranging from low trophic plankton production to fishery resources. Understanding how ecosystems respond to El Nino is the key to the success of ecosystem-based fisheries management (EBFM). However, few studies have focussed on the ecosystems respond to this natural perturbation in China seas, and the selection of effective ecological network analyses (ENA) indicators to evaluate the ecosystem response under El Nino conditions needs to be assessed. In this study, we constructed Ecopath models for Haizhou Bay in ENSO-neutral (2013) and El Nino (2015) years. Comprehensive analyses were conducted to evaluate ENA indicators in terms of sensitivity to the ecosystem variations, robustness to the model parameters uncertainties, and statistical check. Results showed that there were obvious variations in the species composition and biomass in the Haizhou Bay ecosystem under the El Nino event. Four optimal ENA indicators were selected, including total system throughput, total primary production, total system non-cycled throughflow, and ascendency. The indicators further showed a shrunken ecosystem size, increased energetic efficiency, and less organised ecosystem under the El Nino event. These findings enhance our understanding of ecosystem dynamics and underscore the need for precautionary management under El Nifio conditions. Moreover, this work can be helpful in guiding the further selection of ENA indicators for evaluating and managing marine ecosystems during El Nino events elsewhere and thusly contribute to the implementation of EBFM.