Seafloor warm water temperature anomalies impact benthic macrofauna communities of a high-Arctic cold-water fjord

• Published in: Marine Environmental Research
• Main Authors: Jorda Molina, Eric, Renaud, Paul Eric, Silberberger, Marc J., Sen, Arunima, Bluhm, Bodil, Carroll, Michael Leslie, Ambrose, William, Cottier, Finlo Robert, Reiss, Henning
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2023
• Subjects: Arctic; Rijpfjorden; Svalbard; Svalbard Archipelago; Rijpfjord*; Sea ice
• Online Access: https://hdl.handle.net/11250/3085513; https://doi.org/10.1016/j.marenvres.2023.106046

Amid the alarming atmospheric and oceanic warming rates taking place in the Arctic, western fjords around the Svalbard archipelago are experiencing an increased frequency of warm water intrusions in recent decades, causing ecological shifts in their ecosystems. However, hardly anything is known about their potential impacts on the until recently considered stable and colder northern fjords. We analyzed macrobenthic fauna from four locations in Rijpfjorden (a high-Arctic fjord in the north of Svalbard) along its axis, sampled intermittently in the years 2003, 2007, 2010, 2013 and 2017. After a strong seafloor warm water temperature anomaly (SfWWTA) in 2006, the abundance of individuals and species richness dropped significantly across the entire fjord in 2007, together with diversity declines at the outer parts (reflected in Shannon index drops) and increases in beta diversity between inner and outer parts of the fjord. After a period of three years with stable water temperatures and higher sea-ice cover, communities recovered through recolonization processes by 2010, leading to homogenization in community composition across the fjord and less beta diversity. For the last two periods (2010-2013 and 2013-2017), beta diversity between the inner and outer parts gradually increased again, and both the inner and outer sites started to re-assemble in different directions. A few taxa began to dominate the fjord from 2010 onwards at the outer parts, translating into evenness and diversity drops. The inner basin, however, although experiencing strong shifts in abundances, was partially protected by a fjordic sill from impacts of these temperature anomalies and remained comparatively more stable regarding community diversity after the disturbance event. Our results indicate that although shifts in abundances were behind important spatio-temporal community fluctuations, beta diversity variations were also driven by the occurrence-based macrofauna data, suggesting an important role of rare taxa. This is the first ...