New insights into the Weddell Sea ecosystem applying a quantitative network approach

Abstract

Abstract. Network approaches can shed light on the structure and stability of complex marine communities. In recent years, such approaches have been successfully applied to study polar ecosystems, improving our knowledge on how they might respond to ongoing environmental changes. The Weddell Sea is one of the most studied marine ecosystems outside the Antarctic Peninsula in the Southern Ocean. Yet, few studies consider the known complexity of the Weddell Sea food web, which in its current form comprises 490 species and 16041 predator-prey interactions. Here we analysed the Weddell Sea food web, focusing on the species and trophic interactions that underpin ecosystem structure and stability. We estimated the strength for each interaction in the food web, characterised species position in the food web using unweighted and weighted food web properties, and analysed species’ roles with respect to the stability of the food web. We found that the distribution of the interaction strength (IS) at the food web level is asymmetric, with many weak interactions and few strong ones. We detected a positive relationship between species mean IS and two unweighted properties (i.e., trophic level and the total number of interactions). We also found that only a few species possess key positions in terms of food web stability. These species are characterised by high mean IS, mid to high trophic level, relatively high number of interactions, and mid to low trophic similarity. In this study, we integrated unweighted and weighted food web information, enabling a more complete assessment of the ecosystem structure and function of the Weddell Sea food web. Our results provide new insights, which are important for the development of effective policies and management strategies, particularly given the ongoing initiative to implement a Marine Protected Area (MPA) in the Weddell Sea.

Potter Cove’s Heavyweights: Estimation of species’ interaction strength of an Antarctic food web

“…Our findings show some discrepancies with those of Marina et al (2024), who applied the same method to calculate interaction strength for the Weddell Sea (Antarctica) food web, without incorporating empirical density/biomass values. They found a positive relationship between species interaction strength, trophic level, and degree.…”

“…The estimation of the species interaction strength for the Potter Cove food web allowed us a better understanding of species' role in food web stability. We found that the distribution of interaction strength was skewed toward a few strong and many weak links, as observed in extensive theoretical and empirical studies (Drossel et al, 2004;Kortsch et al, 2021;Marina et al, 2024; J. T. Wootton & Emmerson, 2005). This asymmetrical pattern has been proposed to promote ecosystem persistence and stability (Bascompte et al, 2005;Drossel et al, 2004;Emmerson & Yearsley, 2004;McCann et al, 1998).…”