Figur 2a  - korallpolypper Mareano

Benthic fauna may give warning of changes in the environment

The seabed holds a rich diversity of animals big and small. If you look closely at a handful of sand and sludge from the seabed and it will change from a dull grey mass to a writhing, hopping world of crustaceans, mussels and polychaetes. These tiny creatures may help us answer important questions.


Figur 3   Havbunn skuringslinjer Mareano_650x349.jpg

Nature’s own artwork at 260 metres depth in the Barents Sea. Using icebergs as pens, sea currents have sketched neat patterns into the seabed over the course of hundredes of years. The glacial groove in the middle of this computer-generated image is 140-150 metres wide and 8-10 metres deep. The dots in the picture are “pockmarks” made by gases or fluids forcing their way up through the seabed. Pockmarks are common in much of the Barents Sea. Image: Norwegian Mapping Authority/Mareano. Front photo: The coral reef (Lophelia pertusa) are a vulnerable specie. It grow very slowly and stick up out of the seabed and can therefore easily be damaged by e.g. fishing gear. It may take several decades for the deep sea seapen to attain its maximum height of up to 2 metres. Coral reefs need several hundred years to reestablish after damage. Photo: Pål Buhl-Mortensen / Institute of Marine Research/Mareano

By Børge Holte and Gunnar Sætra, Institute of Marine Research

If you grab a handful of sediment from the seabed, you may actually be holding dozens of species big enough to see with your own eyes. If you use a magnifying glass, pocket lens or microscope you will see even more. The animal world on the sea bottom is among the world’s most diverse per unit area. These benthic communities may give warning of climate changes and other factors that influence the environment.


Benthic creatures cannot escape

The large number of species normally found on the seabed means that benthic communities are well suited for measuring the seriousness of any changes in environmental conditions. Some species are sensitive to certain environmental changes and can disappear, whereas other species tolerate the conditions better. In this way, new species are able to take over dominance of a locality. Such changes in a community’s species structure can be proven mathematically and quantified.

It is possible to use benthic communities as a measurement tool for trends in the environment because the animals are essentially stuck in the seabed or can move only short distances. By contrast, fish, marine mammals, and several other species can go elsewhere if faced with environmental changes they dislike or cannot tolerate. Benthic fauna cannot escape. Therefore, some species die when the temperature changes, whereas other species 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. Such baseline mapping is taking place in the Mareano project.


Which areas are being mapped?

Mareano (acronym for Marine areal database for Norwegian waters) is a collaboration between the Institute of Marine Research, the Norwegian Mapping Authority and the Geological Survey of Norway (NGU). One of the reasons for starting the project was to generate data on diverse biotopes to be used in future management of Norwegian seas, as well as following up on the objectives of the UN’s Earth Summit (held in Rio de Janeiro in 1992) concerning ecologically holistic management of the natural environment.

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). Phytoplankton productivity at the edge of the sea ice is especially high because as the ice melts and retreats northward, nutrients become available for algal blooming and sunlight penetrates into the water column.

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. Unlike tropical coral reefs, cold-water reefs grow in relatively deep waters and at low temperatures (4–9°C). 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, the world’s largest known cold-water reef, shows that the conditions in Norwegian coastal waters are favourable for the growth of corals. The Røst Reef complex is as much as 35 kilometres long and 2.8 kilometres wide. On Mareano’s website, the Institute of Marine Research presents running updates about registered occurrences of corals in Norwegian waters.


Comprehensive sampling

Mareano uses vessels belonging to the Institute of Marine Research to map the seabed. We gather sediment samples with different types of tools such as grab, sled and beam trawls, and use video cameras to film the seabed and what lives there. In addition, we use modern multi-beam echo sounders. With this information, we can construct various types of maps, including computer-modelled biotopes.

From a global perspective, the Mareano Project is one of the most comprehensive of its kind. After 10 years, including 3½ years at sea, we have filled more than 4 000 pails and buckets with bottom samples, published two books and about 60 internationally peer reviewed papers, and registered 2 415 different species and taxa of macro- and megafauna. (In this context “macro” means larger than 1 mm and “mega” larger than 5 cm.) Scientists from Norway and abroad, who have borrowed material from Mareano’s fauna collection at the University Museum of Bergen, have described some ten species that are new to science, and several other unknown species are next in line.


Seven-league steps in the right direction  

One of the objectives from the Rio Conference is to ensure sufficient knowledge about ecosystems to predict the effects of human activities on nature. This is the key to holistic and sustainable management – that is, ecosystem-based management – of marine resources. In this way, instead of being caught off guard by unforeseen negative effects, we can take preventive measures. Effective prevention may often make human activities justifiable. Commercial fishing is an example: the harvest of fish is compensated by biological monitoring and a 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 Svalbard.

It is therefore more important than ever to follow up the objectives of the Rio Convention regarding knowledge-based, sustainable management – both to be able to implement preventive measures in untouched sea areas, and to implement measures in waters that have already suffered negative effects. The Mareano Project represents a seven-league step towards achieving this objective. We combine skilled experts and modern technology such as video recordings, measurements with multi-beam echo sounders, computer visualisation and modelling, electron microscopy, DNA sequencing and other tools. The unique multidisciplinary collaboration adds weight to Mareano’s mapping and provides commercial stakeholders, scientists, environmental managers and others with new knowledge. Mareano gives a voice to the benthic fauna and lets them tell us what is happening below the surface of the ocean.

This article is published in Fram Forum 2017

Fram Forum is published on behalf of FRAM - High North Research Centre for Climate and the Environment. It aims to imform the general public about the wide activities that take place within the Fram Centre. The magazine is available online free of charge  to any and all who are interested in topics related to climate, environment and people in the high north.