Where is trawling post

Mazor and colleagues used data from 18 surveys of seabed biota to model and predict the large-scale distributions of seabed invertebrate communities in nine continental shelf and slope regions around Australia. They combined these predictions with spatial data for marine reserves, fishery closures and trawling effort to assess the extent these invertebrate communities were exposed to, or protected from, trawling.

The researchers found that across all invertebrate communities studied, an average of 7 per cent of each occurred in trawled areas, with 38 per cent in areas protected from trawling. In other words, about five times more seabed fauna is protected from trawling than exposed. Trawling disturbance can modify benthic production processes. Pipitone, C. Pranovi, F.

Permanent trawl fishery closures in the Mediterranean Sea: an effective management strategy. Policy 60 , — Ardron, J. Marine spatial planning in the high seas.

Policy 32 , — Burridge, C. A comparison of demersal communities in an area closed to trawling with those in adjacent areas open to trawling: a study in the Great Barrier Reef Marine Park, Australia.

Buchary, E. Cheung, W. Agriculture, Fisheries and Conservation Department, Morton, B. Leung, K. Hong Kong University Press, Leung, A. Agriculture, Fisheries and Conservation Department. Wilson, K. Restoration of Hong Kong fisheries through deployment of artificial reefs in marine protected areas.

ICES J. Legislative Council of Hong Kong. Wang, Z. Macrobenthic communities in Hong Kong waters: comparison between and and potential link to pollution control. Shin, P. An updated baseline of subtropical macrobenthic communities in Hong Kong. Pitcher, T. Marine reserves and the restoration of fisheries and marine ecosystems in the South China Sea.

A cover story: fisheries may drive stocks to extinction. Pearson, T. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment.

Global analysis and prediction of the response of benthic biota and habitats to fishing. The effects of fishing on marine ecosystems. The subsidiary impacts of dredging and trawling on a subtidal benthic molluscan community in the southern waters of Hong Kong. Lindeboom, H. Netherlands Institute of Sea Research, Tao, L.

Trawl ban in a heavily exploited marine environment: responses in population dynamics of four stomatopod species. Rijnsdorp, A. Towards a framework for the quantitative assessment of trawling impact on the seabed and benthic ecosystem. Watling, L. Impact of a scallop drag on the sediment chemistry, microbiota, and faunal assemblages of a shallow subtidal marine benthic community. Sea Res. Wu, R. Periodic defaunation and recovery in subtropical epibenthic community, in relation to organic pollution.

Dauer, D. Relationships between benthic community condition, water quality, sediment quality, nutrient loads, and land use patterns in Chesapeake Bay. Estuaries 23 , 80—96 Environmental Protection Department. Marine Water Quality Data. EPD, Cheung, S. Spatio-temporal changes of marine macrobenthic community in sub-tropical waters upon recovery from eutrophication. Life-history traits and feeding guilds of polychaete community. Fauchald, K. The diet of worms: a study of polychaete feeding guilds.

Macdonald, T. Taxonomic and feeding guild classification for the marine benthic macroinvertebrates of the Strait of Georgia, British Columbia. Jumars, P. Diet of worms emended: an update of polychaete feeding guilds. World Register of Marine Species. Pagliosa, P. Another diet of worms: the applicability of polychaete feeding guilds as a useful conceptual framework and biological variable. Clarke, K. Primer-E Ltd, Grall, J. Using biotic indices to estimate macrobenthic community perturbations in the Bay of Brest.

Shelf Sci. Borja, A. A marine biotic index to establish the ecological quality of soft-bottom benthos within European estuarine and coastal environments. AMBI software. FactoMineR: an R package for multivariate analysis. RStudio Team. RStudio: Integrated Development for R. Fox, J. An R Companion to Applied Regression. Sage, Neter, J. Applied linear statistical models: Regression, analysis of variance, and experimental design Irwin, Chatterjee, S.

Regression Analysis by Example. Download references. We thank Ms. Helen Leung and Dr. Yu Sheung Law for their technical support. You can also search for this author in PubMed Google Scholar. All authors contributed to the review, revision and preparation of the manuscript. Correspondence to Kenneth M.

Leung or Jian-Wen Qiu. Reprints and Permissions. Recovery of tropical marine benthos after a trawl ban demonstrates linkage between abiotic and biotic changes. Commun Biol 4, Download citation. Received : 13 May Accepted : 19 January Published : 16 February Anyone you share the following link with will be able to read this content:. Many animals are associated with sponge grounds; fishes and invertebrates use them as an indirect food source Kunzmann, , shelter from predators Kunzmann, ; Cook et al.

Deep-sea sponge aggregations are included in the list of vulnerable marine ecosystems VMEs FAO, because of their overall low resilience to disturbance and because they are threatened by deep-sea fisheries OSPAR Commission, Epibenthic animals known to form complex structures emerging from the seabed including sponges are particularly vulnerable to bottom-contact fishing practices through direct and indirect effects Clark et al.

Direct effects include the removal of individuals as bycatch but also the damage, dislodgement and crushing caused by the motion of the trawl Clark et al.

As a result, many studies have observed a reduction in the abundance of epibenthic invertebrates in highly trawled locations Freese et al. Furthermore, the removal of habitat forming organisms or structural engineers can lead to long-term changes in community structure and composition e. Such shifts have been particularly well documented in shelf communities Kaiser et al.

While certain sponges can tolerate high levels of sedimentation Bell et al. The loss of dense sponge aggregations is a detrimental outcome of bottom trawling because it can lead to a loss of ecosystem functioning and decreased biodiversity Bell, ; Pusceddu et al.

The time it takes for a community to recover to its pre-disturbed state depends on the degree of disturbance, the life history characteristics of the fauna, and management practices in place Lotze et al.

Most deep-sea organisms have life history characteristics making them particularly vulnerable to anthropogenic disturbances. Therefore, recovery of deep-water assemblages from external disturbance events occurs extremely slowly and is predicted to take decades to centuries Leys and Lauzon, ; Gatti, ; Young, Williams et al. Clark et al. Currently, there are no studies documenting recovery of deep-sea Arctic sponge grounds following disturbance. Information on the recovery of communities living in extreme environments are relevant for understanding the impacts of anthropogenic activities but also to increase our knowledge of the ecological processes of sponge communities.

The Schulz Bank, an Arctic seamount, is an ideal case study because it is a pristine sponge-dominated community that remains untouched by direct human activities. Here, we used video surveys collected 4 years after experimental trawls on the summit and on a deeper area of the Schulz Bank to understand the recovery potential of this highly productive seamount after disturbance events.

Specifically, we compare the taxonomic composition and abundance of sponges and associated fauna within disturbed areas to nearby control sites. The summit of Schulz Bank is the richest area of the bank with a diverse and dense benthic community Roberts et al. As depth increases, species density and richness decreases Roberts et al.

Figure 1. Map of Schulz Bank showing the two Agassiz trawl marks made in Control transects are located 50 m to the west and east of each trawl mark. The red box in the overview panel highlights the location of Schulz Bank.

In , two experimental Agassiz trawls were conducted on the Schulz Bank Figure 1 ; one at the summit — m depth and one on the southwestern flank 1, m depth. The 3-m-wide Agassiz trawl, with a 1 cm mesh size in the cod-end Figure 2 , was towed along the seafloor for m on the summit and m on the flank, resulting in a disturbed area of 2, and 1, m 2 , for the summit and flank, respectively. Towing speed was maintained at around 2 knots and the initial and final position were recorded.

Although we do not have visual information on the communities inhabiting that specific patch prior to trawling, the densities estimated from the trawl catches suggested that most morphospecies were present in comparable densities compared to neighboring areas Rapp, H.

T, unpublished data. This is further corroborated by the study of Meyer et al. Sars Table 1. Control transects were located 50 m to the east and west of each trawl mark and were performed parallel to the mark. Prior to the collection of video footage, we performed various transects in order to carefully map the trawl marks using the high resolution multibeam mounted on the remotely operated vehicle ROV.

In addition, scrape marks were clearly visible on both sides of the Agassiz trawl transect line, which helped the ROV pilots maintaining the transects.

Only the downward looking camera was used for quantitative ecological data. Two parallel lasers were used as scale 16 cm apart. During every transect the ROV was run in a straight line, on a set bearing, at a constant speed and at the same set altitude 2—3 m. From the summit transects, we extracted randomly selected, non-overlapping images at least 5 m apart. Seafloor images were excluded if 1 the area of the image was less than 1. From the summit, after excluding unusable images, a total of images were used.

Fauna that could not be identified to genus or species level were grouped by their size. For each image, we also measured image area, percent coverage of different substrate types soft substrate, hard substrate, and spicule mat , and percent coverage of Lissodendoryx complicata which could not be distinguished by individuals, using a grid in IMAGEJ software.

Substrate types and fauna were counted in each grid cell and divided by the total number of cells and multiplied by to get percent coverage. Percent coverage of Hexadella dedritifera , an encrusting sponge, was recorded as part of a subsample. A subsample of 46 random frames taken from our summit samples was used to count highly abundant fauna Ascidiacea sp. Single photographs do not represent adequate sampling units because the area of one image is too small to represent benthic communities Durden et al.

Figure 3. Species accumulation curves for each site determined from seafloor area coverage of the summit A and the flank B of Schulz Bank. The benthic community found in the deeper area was less dense and patchier, therefore we chose to do continuous annotation of the entire transects to quantify sponges and associated fauna to ensure appropriate coverage. Like the summit, all taxa greater than 1 cm were counted and identified to the lowest possible taxonomic level.

In addition, a subsample of random frames was taken to count ophiuroids, which were highly abundant. For each sampling unit, we computed total morphospecies density individuals m —2 and individual morphospecies densities. Fishes were excluded from analyses due to their high mobility and, to focus on more abundant and reliably sampled taxa, only data from morphospecies observed at least three times were included in analyses excluding 20 morphospecies on the summit and 8 on the flank.

On the summit 23 morphospecies were used. On the flank 19 morphospecies were used Supplementary Table 1. To evaluate if there were significant differences in morphospecies densities and diversity indices between the different transects, we used either a one-way ANOVA following assumptions of normality or Kruskal—Wallis matched pairs test if normality was not met.

Normality was tested using the Anderson—Darling normality test. To identify which treatments differed for each site, post hoc tests were performed Tukey HSD for parametric and Dunn for non-parametric.

For multivariate community analyses, Bray—Curtis metric was chosen for its capability in handling a large proportion of zeros. Matrices were used in non-metric multidimensional scaling nMDS to visualize differences in community composition among transects. Differences in substrate types and in the sizes of the five largest structural sponges between the control and trawled transects were assessed with one-way Kruskal—Wallis tests. Statistical analyses were performed using the computing environment R version 4.

The epibenthic megafaunal density and composition on the summit and flank of Schulz Bank were visually different Figure 4. Pairwise comparisons using Dunn post hoc tests showed that the disturbed areas of both sites had significantly lower densities than both control areas Figure 5. Figure 4. Stills of the epibenthic communities on Schulz Bank; A summit control, B summit trawl mark note the exposed soft sediment , C flank control, and D flank trawl mark.

Figure 5. Boxplots of the density of all megafauna found on the summit A and the flank B of Schulz Bank. Means are noted by diamond shapes.

Disturbed areas had significantly less Hexactinellida spp. The encrusting sponge H. Figure 6. Mean percentage cover of H. Table 2. Schulz Bank summit mean individuals m —2 SE of morphospecies and significance of the difference between transects. On the flank, the average density of morphospecies excluding ophiuroids on the disturbed site was 0. Trawled areas had significantly less S.

The most abundant associated fauna was ophiuroids, which averaged 8. Trawled areas had significantly less Actiniaria sp. Table 3. Schulz Bank flank mean individuals m —2 SE of morphospecies and significance of the difference between transects. There were significantly less morphospecies in the trawled area. In the trawl and Control East areas, there was a lower probability that two random individuals belonged to different morphospecies, indicating lower diversity than in the Control West area.

Trawling significantly increased the evenness of summit morphospecies Table 4. There were fewer morphospecies within trawled areas. The morphospecies on the flank were more even than those on the summit Table 4.

For the summit, the nMDS plot showed strong separation between megafaunal communities in trawled and control areas Figure 7. Table 5. Figure 7. Each point represents a sampling unit and each polygon represents a transect.

Morphospecies abundance values were standardized to individuals m —2. For the flank, the nMDS plot also showed a strong difference between megafaunal communities in trawled and control areas Figure 8. On the flank, dissimilarity was driven by S. Figure 8. Overall, the sizes of the largest sponge morphospecies G.

However, Dunn post hoc tests did reveal that G. On the control sites, spicule mat dominated the substrate On the other hand, the flank had no significant differences in substrate type between the disturbed and control areas, being all exclusively composed of soft sediment.

This is the first study looking at recovery of Arctic sponge grounds following physical disturbance. Our results provide useful insight on how the diversity and megafaunal composition of sponge-dominated communities can be affected by anthropogenic activities like trawling. Overall, our results suggest that after four years, benthic communities within trawl marks have not returned to a pre-disturbed state represented by the control transects with overall densities of epibenthic morphospecies being significantly lower in the disturbed sites than in nearby control areas.

One unavoidable limitation of this study was our lack of true replicates for both trawled areas, implying that are sampling units our essentially pseudo-replicates.

Although many structural sponge morphospecies found on the summit were significantly less abundant within the trawl mark than in control areas, we still observed some large sponges in the disturbed area Table 6. It is likely that these individuals survived the Agassiz trawl in and are unlikely to be new growth since deep-sea sponges typically have slow growth rates Leys and Lauzon, ; Fallon et al.

Fallon et al. Similarly, Leys and Lauzon found longevities of another deep-sea hexactinellid Rhabdocalyptus dawsoni , Lamb to be over years old. In a similar study, Wassenberg et al.

Sainsbury et al. Looking at these studies, the catchability of large sponges by bottom trawls is highly variable, so it is not surprising that we found occasional large sponges in the disturbed area even though Agassiz trawls are among the most efficient types of trawls for sampling benthic communities. The Schulz Bank summit is made dynamic by strong internal waves at the water mass boundary Roberts et al.

Associated fauna have been demonstrated to be more abundant and diverse in and around large and structurally complex sponges compared to nearby areas without sponges Wendt et al. Sponges serve numerous functional roles which benefit other species Bell, ; Buhl-Mortensen et al.