Suspension feeders as natural sentinels of the spatial variability in food sources in an Antarctic fjord: A stable isotope approach

Antarctic ascidians under increasing sedimentation: Physiological thresholds and ecosystem hysteresis

“…Like the canary in the coal mine, ascidians may act as sentinels of sedimentation conditions and living 'sediment traps' since their gut contents provide relevant insights on the sedimentation process, witnessing what is reaching the bottom in Potter Cove (Tatián et al, 2002;Tatián et al, 2004). As sessile suspension-feeders and primary consumers, ascidians serve as indicators of different aspects of ecosystem functioning and spatial heterogeneity of food sources due to local environment and hydrology (Alurralde et al, 2020;Kim et al, 2021;Lefebvre et al, 2009). Spring/summer glacier discharge and wind stress set local differences between the inner and outer part of Potter Cove, as well as between surface and deeper waters (Ruiz Barlett et al, 2021;Schloss et al, 2012).…”

“…Spring/summer glacier discharge and wind stress set local differences between the inner and outer part of Potter Cove, as well as between surface and deeper waters (Ruiz Barlett et al, 2021;Schloss et al, 2012). In addition, variable water retention times and stratification due to meltwater inflows may dilute food sources or patchly distribute them within the fjord (Alurralde et al, 2020). On the other hand, the observed differences among the species provide insights on speciesspecific trophic traits that could determine to some extent the interplay between energy intake and population abundances.…”

Glacial melt impacts carbon flows in an Antarctic benthic food web

“…The substantial biomass of macroalgae has been suggested to contribute significantly to the feeding of benthic communities in Potter Cove (Quartino and de Zaixso, 2008;Seefeldt et al, 2017;Braeckman et al, 2019;Alurralde et al, 2020) and other shallow coastal systems on the WAP (Corbisier et al, 2004;Ortiz et al, 2016). Macroalgae are expanding on the new hard substrate areas that are becoming available due to glacial retreat (Quartino et al, 2013;Amsler et al, 2023;Deregibus et al, 2023).…”

“…When tide-water glaciers retreat on land, coastal and sub-glacial runoff of lithogenic particles increase water column turbidity (Monien et al, 2017) and reduce photosynthetic active radiation levels, hampering primary production of phytoplankton (Kim et al, 2018), macroalgae (Deregibus et al, 2016) and benthic diatoms Hoffmann et al, 2019). Benthic communities further have to cope with increased ice scour frequency (Smale et al, 2008), which may lead to benthos mortality (Gutt, 2001;Smale et al, 2007;Barnes and Souster, 2011), stress for filter feeders due to sediment resuspension (Torre et al, 2012), and consequently, a restructuring of benthic assemblages in terms of community composition (Pasotti et al, 2015a;Sahade et al, 2015) and trophic interactions (Pasotti et al, 2015b;Alurralde et al, 2020). This results in a shift in benthic community functioning from being net autotrophic to net heterotrophic (Braeckman et al, 2021).…”

“…Qualitative networks of food webs in polar marine ecosystems are increasingly being used to infer information on food web structure and stability (Gillies et al, 2012;De Santana et al, 2013;Kortsch et al, 2015;Pasotti et al, 2015b;Marina et al, 2018;Michel et al, 2019;Rodriguez et al, 2022). However, these networks primarily remain descriptive in nature, with limited attention given to quantifying the impact of climate-induced changes to the cryosphere on the food web (Gillies et al, 2012;Pasotti et al, 2015b;Michel et al, 2019;Alurralde et al, 2020). Yet, fluctuations in composition and magnitude of the organic carbon input from primary producers and alterations in the composition and stocks of secondary (and higher order) consumers have been shown to change food web structure and stability (Forest et al, 2011;Sailley et al, 2013).…”