Lene Buhl-Mortensen

The footprint of bottom trawling in European waters: distribution, intensity, and seabed integrity

Mapping trawling pressure on the benthic habitats is needed as background to support an ecosystem approach to fisheries management (EAFM). The extent and intensity of bottom trawling on the European continental shelf (0–1000 m) was analyzed from logbook statistics and VMS data for 2010, 2011 and 2012 at a resolution of 1×1 minutes longitude and latitude. Trawling intensity profiles with seabed impact at the surface and subsurface level are presented for 14 management areas in the North-east Atlantic, Baltic Sea and Mediterranean Sea. The footprint (proportion of the seabed trawled 1 or more times every ten years) ranged between 40–90% across EUNIS habitats with largest footprints observed in sandy (A5.2) and muddy (A5.3) habitats. The footprint of the management areas ranged between 52-99% and 5-94% for the depth zone from 0–200 m (Shallow) and from 201–1000 m (Deep), respectively. The footprint was estimated as the total area of all grid cells that were trawled fully or partially. Excluding these untrawled proportions reduced the footprint estimates to 28-85% and 2-77%. Mean trawling intensity ranged between 0.5 and almost 8.5 times per year, but was less in the Deep zone with a maximum intensity of 6.4 times per year. Highest intensities were recorded in the Skagerrak–Kattegat and Adriatic Sea. Largest footprints per unit landings were observed in the Mediterranean Sea. Bottom trawling was highly aggregated. The seabed area where 90% of the effort occurred comprised between 11% and 65% (median 44%) of the total area trawled. Using the longevity distribution of the untrawled infaunal community, the seabed integrity was estimated as the proportion of the biomass of benthic taxa where the trawling interval at the subsurface level exceeds their life span. Seabed integrity was low (<0.1) in large parts of the European continental shelfs, although smaller pockets of seabed with higher integrity values occur. The methods developed here integrate official fishing effort statistics and industry-based gear information to provide high-resolution pressure maps and indicators, which greatly improve the basis for assessing and managing benthic pressure from bottom trawling. Further they provide quantitative estimates of trawling impact on a continuous scale by which managers can steer.

The MAREANO programme – A full coverage mapping of the Norwegian off-shore benthic environment and fauna

Abstract Information about the distribution, composition and status of the benthic environment and communities is important for the implementation of ecosystem-based management involving assessment of the effects of human activities. The MAREANO programme (Marine Areal Database for Norwegian Coasts and Sea Areas) conducts seabed mapping in order to fill knowledge gaps in relation to the implementation of management plans for the Norwegian EEZ. This paper describes the experience from the mapping strategy used by MAREANO. By using a variety of sampling gears the benthic environment and communities from all types of seabed are thoroughly documented. This involves the mapping of bottom topography, seabed substratum, pollutants, species composition, biomass and habitat forming vulnerable biota in a varied marine landscape. The area mapped from 2006 to 2013 is 131,000 km2, spans depths ranging from 40 to 2700 m and covers a variety of topographic features including canyons, cold seeps and coral reefs. The information gained by this broad mapping approach has offered a unique insight into the diversity of benthic species and habitats. Through interpretation and classification of the information gained MAREANO scientists produce a database and detailed maps of seabed surficial geology, marine landscapes, biotopes and particularly sensitive and threatened habitats. Indicators of human impact, such as pollutants, trawl marks and marine litter are also presented on maps. Experience from 8 years of detailed mapping shows the necessity of thorough mapping for informed management decision-making.

Amphipod fauna along an offshore-fjord gradient

The relationship between the species richness of amphipods and environmental variables was investigated at 10 localities along an offshore-fjord gradient in Norway. The amphipods were fewer, both in numbers and in species, at the fjord localities compared with offshore. Shannon-Wiener diversity (H′) decreased markedly from offshore to the innermost stations, and was positively correlated with sill depth, and negatively correlated with distance to ‘species pool’, C/N, and percentage carbon in the surface sediment. TWINSPAN, a numerical classfication method, divided the amphipod fauna into three groups; (I) offshore, (II) outer fjord, and (III) inner fjord fauna. The faunal pattern was also investigated using Detrended Correspondence Analysis (DCA) and the resulting principle axes were related to 15 environmental variables by correlation analysis. The environmental variables that explained most of the variance in species data were sill depth, C/N, percentage carbon, depth and median grain-size, and together...

Diverse and vulnerable deep-water biotopes in the Hardangerfjord

Abstract This study describes the distribution, species composition and environmental characteristics of benthic habitats and biotopes from 38 stations in the Hardangerfjord, based on observations using high-definition video. Faunal composition was primarily related to substrate composition, distance from open ocean and depth (water masses) by using Detrended Correspondence Analysis. Six different biotopes were observed at depths between 100 and 400 m: (1) Lophelia reef, (2) sponge garden, (3) seapen communities, (4) soft bottom coral garden, (5) hard bottom coral garden and (6) cerianthid stands. Three Lophelia reefs were observed between 140 and 230 m depth in the outer part of the fjord. Geodia spp. and other large sponges were abundant on morainic bottom, on sills. Seapen communities occurred on muddy bottoms mainly between 250 and 350 m depth. The soft bottom coral garden comprised the gorgonian Isidella lofotensis, locally with densities up to 167 colonies/100 m2. Hard bottom coral gardens with Paragorgia arborea and Paramuricea placomus had a much lower density with a maximum of 33 colonies/100 m2. Litter and lost fishing gear were observed on 49% of the locations. Lophelia and sponges were covered with silt to a much higher degree than previously observed offshore. Whether this is caused by naturally higher particle flux in fjords or is due to an increased input from anthropogenic sources cannot be concluded from the present study. In general, anthropogenic activities have lead to increased particle flux in fjords and a demand for monitoring sensitive deep-water habitats to detect related trends of declining biodiversity.

Banks, Troughs, and Canyons on the Continental Margin off Lofoten, Vesterålen, and Troms, Norway

Publisher Summary The continental margin off Lofoten, Vesteralen, and Troms comprises a great variation of marine landscapes, ranging from 0 to 3,000 m in depth largely influenced by previous glaciations and oceanographic processes governed by three different water masses. The biological communities identified with multivariate analyses of results from visual surveys were strongly correlated with water mass distribution, sediment type, and various topographic indices. Broadscale geomorphic features such as canyons and troughs have a significant influence on the distribution of sediment types and biological communities through their modification of current patterns. Currents also influence the distribution of geomorphic features such as sand waves and coral reefs. At a broadscale, the largest faunistic change occurs between the warm Atlantic water and the cold intermediate water mass at depths around 700 m. Banks and plains are important geomorphic elements on the continental shelf off LVT. The biological communities identified with multivariate analyses of results from visual surveys were strongly correlated with water mass distribution, sediment type, and various topographic indices. Broadscale geomorphic features such as canyons and troughs have a significant influence on the distribution of sediment types and biological communities through their modification of current patterns. Currents also influence the distribution of geomorphic features such as sand waves and coral reefs. At a broadscale, the largest faunistic change occurs between the warm Atlantic water and the cold intermediate water mass at depths around 700 m.

Differences in biological traits composition of benthic assemblages between unimpacted habitats

There is an implicit requirement under contemporary policy drivers to understand the characteristics of benthic communities under anthropogenically-unimpacted scenarios. We used a trait-based approach on a large dataset from across the European shelf to determine how functional characteristics of unimpacted benthic assemblages vary between different sedimentary habitats. Assemblages in deep, muddy environments unaffected by anthropogenic disturbance show increased proportions of downward conveyors and surface deposit-feeders, while burrowing, diffusive mixing, scavenging and predation traits assume greater numerical proportions in shallower habitats. Deep, coarser sediments are numerically more dominated by sessile, upward conveyors and suspension feeders. In contrast, unimpacted assemblages of coarse sediments in shallower regions are proportionally dominated by the diffusive mixers, burrowers, scavengers and predators. Finally, assemblages of gravelly sediments exhibit a relatively greater numerical dominance of non-bioturbators and asexual reproducers. These findings may be used to form the basis of ranking habitats along a functional sensitivity gradient.

Assembling ecological pieces to reconstruct the conservation puzzle of the aegean sea

The effective conservation of marine biodiversity through an integrated ecosystem-based management approach requires a sound knowledge of the spatial distribution of habitats and species. Although costly in terms of time and resources, acquiring such information is essential for the development of rigorous management plans and the meaningful prioritization of conservation actions. Located in the northeastern part of the Mediterranean, the Aegean Sea represents a stronghold for marine biodiversity. However, conservation efforts are hampered by the apparent lack of spatial information regarding marine habitats and species. This work is the first to address this knowledge gap by assembling, updating, and mapping information on the distribution of key ecological components. A range of data sources and methodological approaches was utilized to compile and complement the available data on 68 ecological features of conservation interest (58 animal species, six habitat categories, and four other vulnerable ecological features). A standardized data evaluation procedure was applied, based on five semi-quantitative data quality indicators in the form of a pedigree matrix. This approach assessed the sufficiency of the datasets and allowed the identification of the main sources of uncertainty, highlighting aspects that require further investigation. The overall dataset was found to be sufficient in terms of reliability and spatiotemporal relevance. However, it lacked in completeness, showing that there are still large areas of the Aegean that remain understudied, while further research is needed to elucidate the distribution patterns and conservation status of several ecological features; especially the less charismatic ones and those found in waters deeper than 40 m. Moreover, existing conservation measures appear to be inadequate to safeguard biodiversity. Only 2.3% of the study area corresponds to designated areas for conservation, while 41 of the ecological features are underrepresented in these areas. Considering the high geomorphological complexity and transnational character of the Aegean Sea, this study does not offer a complete account of the multifaceted diversity of this ecoregion. Instead, it represents a significant starting point and a solid basis for the development of systematic conservation plans that will allow the effective protection of biodiversity within an adaptive management framework.

Marine litter in the Nordic Seas: Distribution composition and abundance

Litter has been found in all marine environments and is accumulating in seabirds and mammals in the Nordic Seas. These ecosystems are under pressure from climatic change and fisheries while the human population is small. The marine landscapes in the area range from shallow fishing banks to deep-sea canyons. We present density, distribution and composition of litter from the first large-scale mapping of sea bed litter in arctic and subarctic waters. Litter was registered from 1778 video transects, of which 27% contained litter. The background density of litter in the Barents Sea and Norwegian Sea is 202 and 279 items/km2 respectively, and highest densities were found close to coast and in canyons. Most of the litter originated from the fishing industry and plastic was the second most common litter. Background levels were comparable to European records and areas with most littering had higher densities than in Europe.

Amphipod family distributions around Iceland

Abstract Amphipod crustaceans were collected at all 55 stations sampled with an epibenthic sledge during two IceAGE expeditions (Icelandic marine Animals: Genetics and Ecology) in 2011 and 2013. In total, 34 amphipod families and three superfamilies were recorded in the samples. Distribution maps are presented for each taxon along with a summary of the regional taxonomy for the group. Statistical analyses based on presence/absence data revealed a pattern of family distributions that correlated with sampling depth. Clustering according to the geographic location of the stations (northernmost North Atlantic Sea and Arctic Ocean) can also be observed. IceAGE data for the Amphilochidae and Oedicerotidae were analysed on species level; in case of the Amphilochidae they were compared to the findings from a previous Icelandic benthic survey, BIOICE (Benthic Invertebrates of Icelandic waters), which also identified a high abundance of amphipod fauna.

Behaviour and habitat of Neohela monstrosa (Boeck, 1861) (Amphipoda: Corophiida) in Norwegian Sea deep water

Abstract There are few in situ observations of deep-sea macrofauna, due to the remoteness of this ecosystem. Visual surveys conducted for marine management by MAREANO, (marine area database for Norwegian waters) and the petroleum industry (by SERPENTS, scientific and environmental remotely operated vehicle partnership using existing industrial technology) have provided unique material of visual information from large areas in the Norwegian Sea. The distribution, density and behaviour of the deep-sea amphipod Neohela monstrosa (Boeck, 1861) is described based on videos and samples from the Norwegian Sea. This amphipod is common on mud bottoms at 200–2181 m depth in the area. Dense communities were found in stands of the arctic sea pen Umbellula encrinus at more than 1000 m depth where temperatures were below 0° C. The mean density of N. monstrosa observed for larger areas was 4/100 m2 but densities of 15–36 individuals per m2 were found in local patches. It is domicolous which is characteristic of the superfamily Corophiida and digs burrows in soft muddy bottoms primarily by using large shovel-like gnathopods to scoop the sediment out. The amphipod was observed pushing and rolling sediment balls out of its burrow, which were probably held together with amphipod silk. It digs out an upper 3 to 4 cm wide burrow with a horizontal side burrow a couple of centimetres down. Neohela monstrosa appears to feeds on newly settled detritus that it collects from the surface sediment through the use of its long antennae while the burrow is mainly used for protection against predators such as demersal fish. Newly released juveniles are probably kept in the burrow for protection. Based on the local high density of N. monstrosa together with its habit of making long burrows, we suggest that there is significant bioturbation associated with the presence of N. monstrosa in deep sedimentary habitats of the Norwegian Sea, which likely provides an important ecosystem function.