Abstract
Seafloor communities are a critical part of the unique and diverse Antarctic marine life. Processes at the ocean-surface can strongly influence the diversity and abundance of these communities, even when they live at hundreds of meters water depth. However, even though we understand the importance of this link, there are so far no quantitative spatial predictions on how seafloor communities will respond to changing conditions at the ocean surface. Here, we map patterns in abundance of important habitat-forming suspension feeders on the seafloor in East Antarctica, and predict how these patterns change after a major disturbance in the icescape, caused by the calving of the Mertz Glacier Tongue. We use a purpose-built ocean model for the time-period before and after the calving of the Mertz-Glacier Tongue in 2010, data from satellites and a validated food-availability model to estimate changes in horizontal flux of food since the glacier calving. We then predict the post-calving distribution of suspension feeder abundances using the established relationships with the environmental variables, and changes in horizontal flux of food. Our results indicate strong increases in suspension feeder abundances close to the glacier calving site, fueled by increased food supply, while the remainder of the region maintains similar suspension feeder abundances despite a slight decrease in total food supply. The oceanographic setting of the entire region changes, with a shorter ice-free season, altered seafloor currents and changes in food-availability. Our study provides important insight into the flow-on effects of a changing icescape on seafloor habitat and fauna in polar environments. Understanding these connections is important in the context of current and future effects of climate change, and the mapped predictions of the seafloor fauna as presented for the study region can be used as a decision-tool for planning potential marine protected areas, and for focusing future sampling and monitoring initiatives.
Highlights
Primary productivity is at the base of most marine ecosystems
Our results reveal that several aspects of the observed and the modeled marine environment have changed since the calving of the Mertz Glacier Tongue (MGT) (Figure 3)
We predict that the calving of massive icebergs will have farreaching effects on benthic communities mediated through the mechanism of pelagic-benthic coupling, and that changes occur even hundreds of kilometers away from the glacier tongue
Summary
Primary productivity is at the base of most marine ecosystems. In Antarctica, primary production is highly seasonal and intricately tied to the location, timing and duration of sea-ice and icefree areas such as polynyas (Arrigo and Van Dijken, 2003). For most seafloor communities living below the photic zone (∼200 m), surface-derived primary production represents their main food source (Dayton and Oliver, 1977; Duineveld et al, 2004; Ruhl et al, 2014), and is critical for their survival. One of the reasons for the lack of quantitative studies is that surface-derived food is one of the main drivers, it is only recently that the nature and strength of this relationship has been quantified on the Antarctic shelf using a so-called Food-Availability-Model (FAM) (Jansen et al, 2018). Jansen et al (2018) demonstrated a strong link between modeled flux of suspended food along the seafloor and abundances of sessile suspension feeders, providing a framework that allows to estimate the distribution of key elements of the seafloor community and to predict how they may change with changing ocean productivity and currents
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