Structure And Function Of The Southeastern Gulf Of California Ecosystem During Low And High Sea Surface Temperature Variability

The southeastern Gulf of California is located where two major ocean systems meet: the California Current at the north and the North Equatorial current at the south, however the ecosystem-level effects that have such confluence remain unknown. In this study, we compared the structure and function of this ecosystem between two periods 1994-1997 and 2006-2007. We based the comparison on food web models built with Ecopath with Ecosim (EwE) modeling software and assumed local sea surface temperature anomalies (1993-2009) as an environmental indicator. We analyzed the ecosystem function using indicators estimated by EwE. We performed structural analysis using topological centrality indices to analyze the role of trophic species in the food web. We found that the structure and function of the ecosystem differed among the two periods, which were characterized by two clearly different levels of variation (low variability in 1994-1997 and high variability in 2006-2007). The total biomass, total system throughput, net production of the system, connectance and Finn's cycling index decreased from 1994-1997 to 2006-2007. The mean transfer efficiency (MTE) revealed that in the period, the energy flow among trophic levels was more efficient. During 2006/07, there was an increase in the ecosystem's organization, but at the same time, the ecosystem may have been more vulnerable to external perturbations because its resilience decreased. In relation to the structural role of trophic compartments, there were differences in both periods. We found that most groups change their trophic role under different oceanographic conditions. We discuss that the changes in the ecosystem are related to local variability in sea surface temperature. (C) 2021 Elsevier B.V. All rights reserved.