Abstract
In recent years, Arctic and sub-Arctic fish communities have shown extensive reorganization on shelves and in shallow waters, but little is known about the ecological impact of environmental changes in deeper waters. We examined temporal changes (1998-2016) in fish diversity and community structure based on research survey data from East Greenland, over a depth gradient spanning 400 to 1500 m. A northern and a southern continental slope region, 360 km apart, were analysed for temporal changes in water temperature and fish community structure. The bottom water temperature increased by up to 0.2 and 0.5°C, respectively. Contrary to expectations, there was a concomitant loss of species richness of up to 3 and 5 species, respectively, and a decrease in total abundance in both regions. Abundances of individual species displayed different trends between regions, with 3 species of wolf fishes (Anarhichas spp.) and American plaice Hippoglossoides platessoides decreasing in the north and blue antimora Antimora rostrata, Agassiz’ slickhead Alepocephalus agassizii and the roundnose grenadier Coryphaenoides rupestris decreasing in the south. The regional differences may reflect different oceanographic characteristics, as the northern region is more influenced by colder Arctic water, whereas the southern region is primarily influenced by the Subpolar Gyre (SPG). However, the observed temperature increase is expected to be due to an intensifying Atlantic Multidecadal Oscillation and/or anthropogenic climate change and not to SPG changes. The observed changes in biodiversity and community structure associated with warming are likely to affect community dynamics and alter ecosystem functioning.
Highlights
As oceans temperatures rise with global warming, marine species and ecosystems are affected worldwide
We show that deep-water fish communities respond to long-term changes in climate and hydrographic conditions
Species richness and total abundance rapidly decreased concomitantly with an increase in bottom temperature. These observations contradict the general expectation of a delayed response to warming in deep-sea communities and an expected increase in diversity and abundance at high latitudes due to northward migration of temperate species
Summary
As oceans temperatures rise with global warming, marine species and ecosystems are affected worldwide. The expectation is supported by several recent studies showing how pelagic and demersal species rapidly expand their ranges and increase in abundance when sea ice recedes and water temperature increases (Mueter & Litzow 2008, Fossheim et al 2015). Most of these studies were conducted in shallower basins or shelf areas like the Barents Sea (Fossheim et al 2015) and the North Sea (Hiddink & Ter Hofstede 2008, Ter Hofstede et al 2010). In the Labrador Sea, deep-water temperatures changed at a rate of up to ~0.5°C decade−1 over the last 60 yr (van Aken et al 2011)
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