The role of marine birds in the Weddell Sea: a food web approach

SARAVIA, LEONARDO A.; MARINA, TOMÁS I.

Conferencia; 6th World Seabird Twitter Conference; 2020

Food web structure analysis is central to predict the vulnerability of ecosystems to climate change. Recently, the Weddell Sea (Antarctica) suffered the collapse of massive ice shelves. Understanding the role of predators gives insight into the resilience and robustness of complex ecosystems. To test the role of marine birds we performed in silico extinctions on all bird species, and calculated the following network indices: mean trophic level, omnivory, modularity and trophic coherence. Comparison between food webs indices with and without birds were done using Strona curve-ball algorithm. The Weddell Sea food web comprises 490 species and 16,041 links: 15 marine birds with 240 trophic interactions. Most birds are apex predators; Macronectes halli exhibits the highest trohic level: 4.94. All network indices were significantly different between food webs (Anderson-Darling, p < 0.01): mean trophic level, omnivory and modularity were higher in the food web including marine birds; trophic coherence was lower. The tested network indices have implications for food web stability. Therefore, marine birds are important nodes regarding the stability of the network structure. Most marine birds are migratory species and are expected to respond to climate warming by moving into new suitable regions. Considering the topological role of birds is crucial to understand the implications of these movements for ecosystem structure and functioning.