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Benthic fauna can offer environmental alerts

05 April 2017

Benthic communities are an ideal measurement tool for trends in the marine environment – a fact that is inspiring a current research project by Norway’s Institute of Marine Research (IMR).

Called the Mareano project, it involves baseline mapping of the seabed and the animals that live there, in a bid to measure climate change. After all, these bottom-dwelling animals are essentially stuck in the seabed, or can move only short distances. By contrast, fish and marine mammals are more mobile if faced with environmental changes they dislike or cannot tolerate. Benthic fauna cannot escape – some species die when the temperature changes, whereas others proliferate.

Human activity also affects the seabed: fishing gear such as trawls leave tracks and change the benthic fauna’s physical living conditions. Mining waste spilled into the sea changes the seabed; the same may be true of extraction of oil and gas. Indeed, benthic animals are already being used to measure any influence around offshore installations. It is important to map the seabed before starting such activities, so it is possible to find out which changes follow from fisheries, mineral extraction or petroleum activities.

Site selection

Mareano (Marine areal database for Norwegian waters) is a collaboration between IMR, the Norwegian Mapping Authority and the Geological Survey of Norway (NGU). The areas being mapped by Mareano have been carefully selected to include fish spawning grounds, areas with high biological productivity, fishing grounds, the marginal ice zone in the Barents Sea, and the transition area between arctic and subarctic water masses (the polar front). 

Mapping of coral reefs is a high priority. The coral in question (Lophelia pertusa) grows very slowly, only a few millimetres per year, and is therefore particularly vulnerable to damage by fishing gear. These reefs provide shelter and nutrition for scores of benthic animal species and fish, and are known to harbour rich biodiversity. There are several thousand coral reefs on the Norwegian continental shelf, especially in areas like the edge of the slope, where seabed currents transport food particles and supply the coral polyps with sustenance. The Røst Reef, at 35 kilometres long and 2.8 kilometres wide, is the world’s largest known cold water reef.

Mareano uses IMR’s vessels to map the seabed. Project partners gather sediment samples with grabs, sleds and beam trawls, and use video cameras to film the seabed. In addition, modern multi-beam echo-sounders are used to help construct various types of maps, including computer-modelled biotopes. After 10 years, including 3½ years at sea, participants have filled more than 4,000 pails and buckets with bottom samples, published two books and about 60 internationally peer-reviewed papers, registered 2,415 different species and taxa of fauna and already described some ten species that are new to science.

Ecosystem-based management

One of the objectives from the Rio Conference is to be able to predict the effects of human activities on nature – which is the key to ecosystem-based management of marine resources, as it allows preventive measures to be adopted. Effective prevention may often make human activities justifiable. Commercial fishing is an example: the harvest of fish is compensated by biological monitoring and controlled by a strictly enforced quota system. The effects of ongoing climate change are apparent in northern waters. Higher temperatures have been registered in the Barents Sea over the last decades. Climate effects have been detected in shallow benthic fauna communities near Svalbard, and the geographical range of several fish species has expanded into arctic waters east of the archipelago.

A longer version of this article, by Børge Holte and Gunnar Sætra, was published on IMR’s website this week.



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