Eco-Dynamic Analysis of the Community Structure of Nekton in the Northern South China Sea

Abstract

The universal laws of thermodynamics in the process of ecosystem development have long been the common research focus of ecology and biophysics. Eco-exergy from thermodynamics is a popular theory in the study of ecosystem self-organization that has been widely used in the study of wetlands and aquatic ecosystems. This study is based on the data of bottom trawl fishery resources in the Northern South China Sea in 1964–1965, 1997–1999, 2006–2007, and 2017. Based on the eco-exergy theory, the exergy contribution rate (PC) of the nekton community and the exergy contribution rate (PL) of different organismic populations were constructed. The eco-exergy (EX) and specific eco-exergy (EXsp) of the nekton in the northeastern South China Sea were analyzed. The results show that, from 1964 to 2017, the EX and EXsp of the nekton community decreased 13.28-fold and 1.42-fold, respectively. Fish populations remained the major contributors to the EX and EXsp of the nekton community; however, compared to crustaceans and cephalopods, their role in maintaining the stability and complexity of the community structure was gradually weakened, and the genetic information per unit of biomass decreased. Meanwhile, compared to fish, the proportion of the EX of crustaceans and cephalopods in the nekton community showed an upward trend. The proportion of crustaceans increased from 2.76% in 1997–1999 to 14.84% in 2017, while that of cephalopods increased from 3.55% to 16.67%. Based on the findings, we speculate that crustaceans and cephalopods play an increasing role in the stability and complexity of the fishery resource structure in the Northern South China Sea. The species replacement in the nekton was obvious, and the dominant species of the Nekton community gradually changed from k-type species to r-type species in the Northern South China Sea.