Cephalopods, particularly squids, are known to play an important role in Southern Ocean (SO). There are eighteen squids’ species in the SO and it is expected that more waits to be discovered. Pelagic species [1] have their distribution determined by latitude and can be classified in relation to the major latitudinal fronts system [2].
The major role of squids in the SO is related with trophic relations [3]. Squids are voracious predators that feed in a wide range of prey including crustaceans, fish and other squids, although with particular interest by Antarctic krill. They are also prey of top predators such as wales, seals, albatrosses, penguins, toothfish and others, being consumed 34 106 tons per year, linking the lower trophic levels with the top of food chains.
Besides the ecological importance, Antarctic squid are a target for future commercial exploitation. Nowadays there are exploratory fisheries to Martialia hyadesi, although already with precautionary measures [4] applied due to the importance that squid have in ecosystem and the collapse of stocks will have dramatic consequences in top predators’ populations.
For these reasons and with the global climate changes it is important to understand how squid populations will be affected by environmental changes, such as rising temperatures, physical changes (ocean circulation, sea ice changes and ocean acidification) and complex ecological changes. With predictions pointing to an increase of almost +1ºC in 2100 it is expected that this increasing will affect the latitude [5] range of several species, with endemic high latitude species having their north limit decreasing and with warmer water going further to south. Physical factors like ocean acidification will affect statolith [6] development which leads to uncontrolled swimming behaviour. Changes in ocean circulation will affect primary production and the transport of squid paralarvae (critical to complete the early phase of squids’ life cycle). Sea ice changes won’t affect squid directly, instead will influence ecosystems that squid depends, affecting species like Antarctic krill which are the main prey of SO squid.
Climate changes will, on different ways, affect negatively SO squid, however this impact will be due to ecosystem changes than by stress caused in organisms. A positive point is that the biology of squid, i.e. fast growing, iteroparity, short generation times, voracity and a large diet spectrum gives to them ability to respond rapidly to environmental changes and to fill empty ecological niches [7] left by other species.
[1] Pelagic species are species that live in the water column, i.e. species that don’t depend of the ocean floor to live.
[2] Oceanic fronts are boundaries between two distinct water masses, generally these water masses have distinct characteristics, different temperatures for example.
[3] Trophic relations are the relations that exist between species along the food chain
[4] Precautionary measures are measures that are applied to prevent something bad to happen before we know the real impact
[5] Latitude is the distance (measure in degrees) from equator to the pole, and varies between 90º North and 90º South
[6] Statoliths are carbonated pieces that helps fish and cephalopods in their perception of the surrounding environment
[7] Ecological niches are places that fill the conditions for a species to survive.
Source:
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Rodhouse, P. G. K. (2013). Role of squid in the Southern Ocean pelagic ecosystem and the possible consequences of climate change. Deep Sea Research Part II: Topical Studies in Oceanography, 95, 129–138. doi: 10.1016/j.dsr2.2012.07.001
Author: José Queirós