Nearshore marine communities

Nearshore marine communities (6)

nearshore

The coastline represents the face of marine biodiversity for the general public, and the first evidence of habitat degradation due to, for example, accidental discharges from the petroleum industry. Furthermore, they are important in terms of both their biodiversity, and their ecosystem function. Provision of food and/or shelter for many organisms, including commercial fish, shellfish, and seabirds, is linked with the physical regime (light field, wave and current exposure, depth), and the variability in these habitat-determining factors over relatively small spatial scales.

This activity will focus on cataloguing the biodiversity of multiple nearshore subhabitats in northwestern Finnmark, including intertidal macroalgae, kelp forests, and subtidal algal- and gravel- associated fauna. Time-series analysis of hard-substrate communities will provide a baseline of community variability from one of the longest continuous photographic series in northern Europe (annual for 28 years). While the kelp-bed ecosystem has been fairly well described for western and southern Norway, the ecology of kelp systems in northern Norway has received little attention. Seasonal migration of resident fauna, persistence of ‘barrens’ devoid of kelps, and interactions of faunal life-histories with physical characteristics all could provide important insights into the recovery/restitution potential of these habitats. In conjunction with habitat models, results of studying kelp-bed ecology across a range of exposure levels can also indicate vulnerability of coastal areas to impacts of petroleum discharges from nearby installations.

Biodiversity of intertidal macroalgae

Intertidal macrolage are one the first elements of marine biodiversity the public see

Macroalgae in the littoral zone are important refuges and feeding areas for a range of organisms. Capelin spawn in the intertidal zone, depositing the eggs on different species of seaweeds (Fucus spp.) or directly on gravely substrate. In addition, dense populations of algae have a habitat structuring function, stabilising gravelly substrates, thereby counteracting coastal erosion. Further, the intertidal zone is the place the public first meets marine biodiversity, such that a study of macroalgae in the Finnmark region is an important part of ASBD.

In Finnmark, many macroalgal species have never been recorded, but on species lists they are marked as inferred occurrences. The purpose of sampling is to get as much information on species composition as possible. The activity will contribute to baseline data on Finnmark coastal biodiversity.

Effects of petroleum activities on sensitive life-stages

Oil release nearby vulnerable fjord ecosystems could have disastrous effects on local fish which spawn in the littoral zone such as the capelin (Mallotus villosus). Eggs attached to the substrate, developing fish embryos or fry have no or only limited capacity to escape oil spills and it is more likely that they are exposed to toxic components of oil in the water column or accumulated in the sediment. Therefore, accidental oil releases during or before the spawning period could be critical to the fish populations of seasonal littoral zone spawners.

Shallow subtidal soft sediment communities

Soft-bottom benthic faunal surveys are fundamental to marine environmental programmes, including monitoring of the petroleum activities at the Norwegian offshore. Based on data series extending from the 1980's to today, we can trace sea-floor changes due to natural fluctuations (reference stations) and anthropogenic effects (monitoring stations). Based on these surveys, the petroleum industry has been able to implement a number of remedial measures, to minimise the environmental impact on the sea floor.

Coastal areas are the regions where the public first meet marine biodiversity, and, as such, it has a high esthetical and "bequest" value. In the event of any, real or perceived, impacts in the coastal zone, it is essential that we can distinguish anthropogenic changes from natural fluctuations. To do this, we need reference data from fixed sampling stations, preferably sampled over several time-periods. However, unlike off-shore, there are no comprehensive national monitoring programmes ongoing for sublittoral, coastal soft-bottom fauna.

Long term variability of shallow hard bottom substratum

Since the 1980's photographs have been taken annually at exactly the same place, at several locations around Troms, Finnmark and Svalbard

One of the most critical needs for understanding ecosystem change is long term data series. This project provides such a data series in the region of interest for ASBD. By examining changes in community composition over several decades, we hope to identify and explain past changes in species interactions for underwater marine rocky habitats. This examination will generate key baseline environmental information to assess the magnitude of changes that are occurring over time and to examine relationships between biological community compositions and climatic variables.

Nearshore habitat mapping and spatial predictive modeling

Modeling of coastal habitats. Trine Bekkby. NIVA

The purpose of this activity is to develop spatial predictive models, showing the probability of finding various habitats, such as kelp forest, potential eelgrass meadows and littoral soft bottom along environmental gradients. As part of this work, digital depth models, models on terrain variability and wave exposure models are developed and integrated. This sub-project is tightly coupled to ASBD activity WP3-1.1.

This activity integrates data relevant for evaluating the vulnerability of areas to disturbances (data from the national marine mapping program): areas important for sea birds, areas of coral and areas of high current speed.

Biodiversity and ecology of nearshore ecosystems - kelpbeds and associated habitats

Sea urchins have grazed down the kelp forest in Porsangerfjorden, Finnmark. Photo: Hartvig Christie. NIVA.

Kelp forests are prominent features of coastal ecosystems along the coast of Norway and provide a habitat for highly diverse communities of animals and plants. This abundant food source, as well as the physical shelter provided by the kelp in turn attracts large populations of fish, seabirds and marine mammals.

Some species inhabiting kelp forests are sedentary, more or less permanently attached to the kelp, whereas others are highly mobile. As a result, the composition of the biodiversity of kelp forests can vary considerably, both between areas, seasonally and inter-annually.

The kelp forests north of Brønnøysund (Nordland County) have been partly grazed down by the sea urchin Strongylocentrotus droebachiensis. Grazing is most severe in areas with moderate to low wave exposure. The kelp forests of North America has also been grazed down by sea urchins, but restitution of the kelp forests has been observed in some areas, partly due to predation of sea urchin larvae by crabs. One mechanism causing the imbalance is thought to be overfishing of bottom-feeding fish, although other unsubstantiated hypotheses for the situation in Northern Norway exist. For example, some 15 years ago, seal hunting was forbidden in the coastal fjords. Seals are a major predator of wolfish, which in turn are major predators of urchins. Therefore, it is not unlikely that seal predation on wolffish also may have contributed to the increase in urchin populations.

The natural predators in the system, such as juvenile cod, disappeared thereby providing an opportunity for the sea urchins to have unusual reproductive success, in turn causing the huge aggregations of sea urchins grazing down the kelp forest.