Evaluating the impacts of extinction thresholds of species in a marine food web in the Yellow Sea (China)

The Earth's biosphere is undergoing a drastic reorganization. Multiple approaches focus on extinction cascades in food webs through species interactions, but the extinction thresholds (ET) of interactions is often overlooked in this process. Furthermore, the accumulation of species extinction could dramatically alter the structure and function of food webs. Therefore, considering ET on the basis of species interactions is critical for predicting the potential impact of cumulative species extinctions. Based on the bottom trawl survey data in Haizhou Bay located in the central Yellow Sea of China, a food web model was constructed to compare the response variance of food web to species extinction from different trophic level categories. In addition, we simulated the cumulative extinction sequences and combined all ETs (0.05 intervals from 0.00 to 1.00) to explore their effect on the food web through indicators such as species richness (S), connectance (C), link density (LD), pred-release (Pr), and Structural robustness (R₅₀ and R₁₀₀). Eventually, by comparing the response of cumulative extinction of species with and without ET, we predicted the potential effects of multiple species extinctions on food webs. t-test showed that there was no significant difference in the response of food web to trophic species (at the species taxonomic level) extinction with different trophic level categories (P > 0.05), and no secondary extinction occurred. The regression analysis of ET and the number of primary extinctions until network fully unconnected was performed as explanatory and response variable, respectively, and showed that there was a significant linear negative correlation between them (P < 0.01). We found that ignoring ET of interactions during the extinction cascade underestimates the impact of species extinctions on food web, especially cumulative extinctions of multiple species. These findings will help to comprehensively understand the impact of species extinction on food webs and provide a good direction for future management.