Impacts of intensive recreational diving on reef corals at Eilat, northern Red Sea

Coral reefs at Eilat, northern Red Sea, are among the most heavily used in the world for recreational diving, with >250,000 dives per year on only 12 km of coastline. We assessed patterns of dive frequency, diver behavior, and coral damage on selected reefs at Eilat, in order to determine impacts of diving tourism. Frequencies and types of recreational SCUBA dives varied widely between 12 coral reef sites, with >30,000 dives per year at the most heavily-used sites. Field observations of diver behavior revealed ca 10 incidents of reef contact per dive, mostly via raising of sediments onto the reef, but also involving direct breakage of corals. The proportion of damaged coral colonies varied significantly with the frequency of SCUBA diving, and did not depend upon site topography. We conclude that current rates of recreational diving on some reefs at Eilat are unsustainable, resulting in damage to the majority of stony coral colonies. This study reveals consequences of diving tourism at extremely high levels of use. Our estimate of diver carrying capacity for reefs at Eilat is similar to levels proposed for other reef sites around the world.     

Scuba diver behaviour and the management of diving impacts on coral reefs

Coral reefs worldwide are attracting increasing numbers of scuba divers, leading to growing concern about damage. There is now a need to manage diver behaviour closely, especially as many dive companies offer unlimited, unsupervised day and night diving from shore. We observed 353 divers in St. Lucia and noted all their contacts with the reef during entire dives to quantify rates of damage and seek ways of reducing it. Divers using a camera caused significantly more contacts with the reef than did those without cameras (mean 0.4 versus 0.1 contacts min⁻¹), as did shore versus boat dives (mean 0.5 versus 0.2 contacts min⁻¹) and night versus day dives (mean 1.0 versus 0.4 contacts min⁻¹). We tested the effect of a one-sentence inclusion in a regular dive briefing given by local staff that asked divers to avoid touching the reef. We also examined the effect of dive leader intervention on rates of diver contact with the reef. Briefing alone had no effect on diver contact rates, or on the probability of a diver breaking living substrate. However, dive leader intervention when a diver was seen to touch the reef reduced mean contact rates from 0.3 to 0.1 contacts min⁻¹ for both shore and boat dives, and from 0.2 to 0.1 contacts min⁻¹ for boat dives. Given that briefings alone are insufficient to reduce diver damage, we suggest that divers need close supervision, and that dive leaders must manage diver behaviour in situ.     

“Take only photographs and leave only footprints”?: An experimental study of the impacts of underwater photographers on coral reef dive sites

Impacts caused by recreational scuba diving on coral reefs vary widely among different dive locations and individual divers. Linear modelling was used to explore a range of individual and situational risk factors associated with divers who damaged corals in the Great Barrier Reef Marine Park. Recreational divers were followed for 10–15 min, and all contacts with, and damage to corals were recorded. Information on the dive site, diving experience, gender, and use of an underwater camera were recorded. Thirty-two out of 214 divers (15%) damaged or broke corals, mostly by fin kicks (95%). Impacts were most likely to be caused by male divers, in the first 10 min of the dive, at sites with a large abundance of branching corals. Specialist underwater photographers caused more damage on average (1.6 breaks per 10 min) than divers without cameras (0.3 breaks per 10 min). To explore the effects of gender and use of a camera further, we issued single-use underwater cameras to 31 randomly chosen divers and compared their behaviour to a control group. Use of a camera had no influence on the rate or amount of damage caused by these naïve photographers, but male divers were more likely to break corals and caused significantly more damage, on average, (1.4 breaks per 15 min) than female divers (0.3 breaks per 15 min). Variability in the amount of damage caused by divers in our sample reflected the very different underwater behaviours exhibited by specialist and non-specialist photographers, and male and female divers. Greater understanding of the causes of harmful behaviours by these groups will allow better targeting of on-site interpretative and cautionary information and may prove to be a more palatable management strategy than regulation of site use.     

Connectivity of reef fish between mangroves and coral reefs: Algorithms for the design of marine reserves at seascape scales

Many species of coral reef fish undertake ontogenetic migrations between seagrass beds, mangroves, and coral reefs. A recent study from the Caribbean found that the availability of mangrove nursery habitat had a striking impact on the community structure and biomass of reef fish in their adult, coral reef habitat. The biomass of several species more than doubled when the reefs were connected to rich mangrove resources (defined as having at least 70 km of fringing Rhizophora mangle within a region of 200 km²). Here, the results of this large-scale empirical study are translated into a series of algorithms for use in natural resource management planning. Four algorithms are described that identify (i) the relative importance of mangrove nursery sites, (ii) the connectivity of individual reefs to mangrove nurseries, (iii) areas of nursery habitat that have an unusually large importance to specific reefs, and (iv) priority sites for mangrove reforestation projects. The algorithms generate a connectivity matrix among mangroves and coral reefs that facilitates the identification of connected corridors of habitats within a dynamic planning environment (e.g., reserve selection algorithms).     

Rapid diversity and abundance decline in a Caribbean coral reef sponge community

Sponges are abundant and diverse on coral reefs, and play key functional roles; but virtually nothing is known of their dynamics. This is the first report of coral reef sponge community dynamics documented by a series of censuses in which volume and species of every individual were recorded. At the start of the 14 year study, there were 1395 sponge individuals, representing 39 species in nine orders, and a total sponge volume of 33,721 cm³ in the censused area of a shallow Caribbean reef in San Blas, Panama. The most striking results of the 5 censuses were steady disappearance of species (51.3%) throughout the study period, and a steep drop in total sponge volume (42.6%). Species in keratose orders and with massive growth forms were lost disproportionately. Sponge losses could not be attributed to predators, physical disturbance (including a hurricane), extreme episodes of other abiotic factors, or disproportionately great loss of rare species due to random fluctuations. Disease may have played a role.High loss rates documented at this and nearby sites could be a local phenomenon, but scattered reports of disease and mass mortality of sponges from other sites suggest these data may reflect region-wide losses. Monitoring programs designed for corals and mobile unitary organisms can miss changes in sponges because very high sponge species diversity, facile fragmentation and fusion, and quick and complete disappearance of dead sponges, impedes perception of changes if there are no prior censuses. Whether or not sponge declines are extensive will remain unknown until repeat censuses have been accomplished at additional sites. Sponges can increase water clarity, bind live corals to the reef frame, and facilitate reef regeneration, suggesting that loss of sponges could accelerate declines of coral reefs.     

Evidence for a depth refuge effect in artisanal coral reef fisheries

Natural refuges can play a fundamental role in protecting species from overexploitation but have not been adequately quantified in the marine environment. We quantified the effect of a depth refuge on all fish species in an artisanal coral reef fishery in Zanzibar, Tanzania by comparing changes in fish species richness and relative abundance with depth at five fished and three unfished reefs across the region. Commercial species richness was depleted by 15.1% at shallow depths in fished reefs, but there was no difference between the reefs deeper than seven metres. Non-commercial species were not affected by fishing or depth. Evidence for similar patterns in fish communities in other countries and depth-limitations to artisanal fishing methods imply this effect is widespread. The depth refuge effect could be sustaining coral reef fisheries and should be taken in to account before implementing policies or subsidies that encourage or allow fisheries to exploit deeper waters.     

El Niño induced local extinction of coral reef bryozoan species from Northern Bahia, Brazil

The 1997-1998 El-Niño Southern Oscillation was the most severe on record and dramatically impacted corals worldwide. However, the effect of this event on the associated community of reef organisms has received much less attention. The composition of the bryozoan assemblage from the coral reefs of Northern Bahia, Brazil were monitored annually from 1995 to 2000, allowing the investigation of the effects of this large-scale stressor on an important, diverse, yet understudied component of the coral reef system. Bryozoan samples (35 replicates/reef) were collected during April/May from four shallow bank reefs (10-40 m depth) located a few kilometres off the coast, together with measurements of the associated environmental parameters. Currently 157 species have been recorded from the study area, but significant reductions in density and diversity were apparent between pre- and post El-Niño Southern Oscillation (ENSO) years, multivariate analysis denoting significant changes in assemblage composition. A total of 61 species were unrecorded following the 1997-1998 ENSO event (22 species from 1997; 25 further species from 1998 and 14 more from 1999). These included several species endemic to Brazil, suggesting that the 1997-1998 ENSO has had a marked influence on the reef bryozoan community, resulting in the local extinction of several species. Bryozoan mortalities were probably initiated by elevated temperatures, but continued disappearance of species for 2 years after ENSO suggests other indirect factors are also influential. These results demonstrate that ENSO events can have severe long-term impacts on the biodiversity of coral reefs, with important conservation consequences.     

Seahorse declines in the Derwent estuary, Tasmania in the absence of fishing pressure

Seahorses have the potential to be flagship species for estuarine conservation around the world and considerable concern has arisen over their declining abundance in the face of exploitation. All seahorses were recently listed on CITES Appendix II in recognition of threats posed by unsustainable trade. However, the efficacy of this measure and the development of other effective conservation solutions will require an understanding of natural seahorse population dynamics at relevant ecological scales. In this study, we provide quantitative data on seahorse populations over nested spatial and temporal scales up to 10 km and 3.5 years. Unexploited populations of the big-bellied seahorse (Hippocampus abdominalis) in the Derwent estuary, Tasmania, Australia consisted largely of mature adults with highly female-biased sex ratios at all sites. While big-bellied seahorses had an aggregated distribution at the spatial scale of our transects (200 m²), most individuals were found alone. When they occurred in groups, the distribution of individuals was random with respect to sex in contrast to the pair bonds found in other seahorse species. All three monitored populations showed significant declines in abundance of 79-98% over the period 2001-2004. Estuarine physicochemical conditions did not change markedly during this period. Possible causes of seahorse declines are interactions with invasive species, disease or reproductive limitation through Allee effects. The magnitude of the declines in the absence of direct exploitation demonstrates that seahorses face multiple threats. Robust fisheries-independent monitoring will be required to demonstrate that conservation actions such as CITES listing are effective.     

Conservation of coral reef biodiversity: a comparison of reserve selection procedures for corals and fishes

A range of different biodiversity-based selection methods for nature reserves has been tested for terrestrial environments, including those based on diversity hotspots, endemicity hotspots and complementarity. In this study, we investigate the utility of these approaches for a coral reef embayment. We compare coral and fish species richness in a random accumulation of reserve sites with (a) hotspots analysis, (b) stratified selection of hotspots, and (c) complementarity. Cumulative species-site curves indicated that complementarity maximized the rate of accumulation of species of both corals and fishes in reserves, while the hotspot approach performed moderately well. An equivalent number of reserve sites supported a greater proportion of the coral biodiversity when compared to fishes, reflecting the broader distribution of corals. Our results indicate that when choosing an indicator group as a proxy for representing overall diversity in a reserve network, the group with the greatest heterogeneity will provide the best results. Our findings also show that although a modest number of protected sites (20%) will incorporate much of the local diversity (>75%), species-specific approaches must be incorporated to target rare species.     

Acanthaster planci on the great barrier reef: Detailed surveys of four transects between 19° and 20°S

In 1973 and 1974 two surveys were conducted of all reefs falling within four transects in the region of the Great Barrier Reef thought to represent the southern section of the area in which large populations of Crown-of-thorns starfish (Acanthaster planci (L.)) were active. The surveys were carried out by towed or free-swimming snorkel divers who covered the entire perimeter and the majority of back reef and lagoonal areas of reefs visited. Of 25 reefs surveyed ten were found to carry large populations of A. planci during one or both surveys. The interval between surveys was 11 months for transects 1–3 and six months for transect 4. During the interval A. planci populations increased on two reefs but decreased on five although the overall number of A. planci sighted was similar for the two surveys.The surveys revealed considerable changes in the density and distribution of A. planci populations on individual reefs but did not produce evidence of migration of adult A. planci onto previously unpopulated reefs.Dense populations of A. planci were studied by SCUBA divers; the highest population density recorded during the surveys was considerably less than that reported during earlier surveys of starfish populations on the Great Barrier Reef.Although there were areas on a number of reefs in which considerable coral mortality appeared to have been caused by the predation of A. planci they were generally restricted and interspersed with areas with a moderate cover of live corals.     

Thresholds and multiple scale interaction of environment, resource use, and market proximity on reef fishery resources in the Solomon Islands

Reef fish are critical in maintaining the ecological function of coral reefs and providing food security for coastal communities in developing countries. Reef fishery stocks are under increasing threat from factors such as climate-related habitat degradation, land use practices, and resource extraction related to human population growth, direct consumption and increasing connectivity between the in situ fishery and fish markets. This study investigates how reef fish stocks are related to environmental, localised resource use and market proximity indicators across 51 sites in the Solomon Islands. Hard coral cover is the best indicator of total target fishery biomass, with cover of less than around 31% associated with significantly less biomass than sites with higher coral cover. Direct resource use indicators such as fish consumption and fish sale pressure were poor predictors of target fish biomass. Distance of the fishery resource from community, provincial sub-station, provincial capital and national capital are all significantly and positively correlated with biomass for four key fishery families: Acanthuridae (surgeonfish), Scaridae (parrotfish), Lethrinidae (emperor), Lutjanidae (snapper). Multiple spatial scale relationships are evident between market proximity indicators and Lutjanidae and Scaridae families. Thus, while pooled target fishery biomass is constrained by environment, analysis at fishery family resolution reveals the effects of anthropogenic impact through market proximity on constraining fishery biomass distribution in the Solomon Islands. This study highlights the need for reef fishery managers and conservation practitioners to focus attention on proximity of resources to markets to sustain the ecological health of reef dominated ecosystems.     

Seagrass beds and mangroves as potential nurseries for the threatened Indo-Pacific humphead wrasse, Cheilinus undulatus and Caribbean rainbow parrotfish, Scarus guacamaia

The importance of seagrass beds and mangroves as a juvenile habitat as opposed to other shallow water habitat types is investigated using a single sampling method on four islands in the western Indian Ocean for Cheilinus undulatus, and on one island in the southern Caribbean Sea for Scarus guacamaia. Both species occur on the Red list of threatened species. Juveniles of Cheilinus undulatus were predominantly found on seagrass beds while adults were limited to the coral reef. The presence of seagrass beds resulted in significantly higher densities of the species on coral reefs in front of these habitats, indicating the importance of seagrass beds as a juvenile habitat. For Scarus guacamaia, juveniles were exclusively observed in mangroves while adults only occurred on the coral reef. Adult S. guacamaia occurred on all coral reefs along the sheltered coast of the island containing mangroves, but no relationship with distance to mangroves was observed. This could indicate the importance of mangroves for the occurrence of adults of this species on the scale of an entire island.     

Reefs of an uninhabited Caribbean island: fishes, benthic habitat, and opportunities to discern reef fishery impact

Navassa Island is a tiny, (5 km²) uninhabited US protectorate located between Jamaica and Haiti. It is part of the Caribbean Islands National Wildlife Refuge, under the jurisdiction of the US Fish and Wildlife Service. We conducted a quantitative assessment of Navassa's coral reef fishes and benthic habitat, in order to assist with the development of conservation plan for the island. The shallow reefs of Navassa (<23m) have high live coral cover (range 20-26.1%), high degree of architectural complexity (rugosity index range 1.4-1.9), and moderate abundance of the keystone grazing urchin, Diadema antillarum, at all sites (mean 2.9±0.9 per 30 m²). Despite its remoteness, an unregulated, artisanal fishery (primarily using traps and hook and line) carried out by Haitians is the primary mode of human impact on Navassa reefs. Even so, reef fish communities exhibit high density (range 97-140 fish per 60 m²) and retain representation by large snapper, grouper and herbivores, which are mostly lacking in nearby Caribbean locations with high fishing pressure. Thus, Navassa reefs appear to be trophically intact with fish populations relatively “unexploited,” presenting a conservation challenge and a research opportunity. The regulation and conservation of the fishery will be difficult, due to the international nature of the situation. However, given the apparently small impact that artisanal fisheries have yet had on its reef communities, Navassa presents a possibly unique opportunity to study the ecological functioning of a relatively trophically intact Caribbean reef, and represents a strong imperative for conservation, monitoring, and research.     

Impacts of lost fishing gear on coral reef sessile invertebrates in the Florida Keys National Marine Sanctuary

The Florida Keys coral reef ecosystem supports multimillion-dollar commercial and recreational fisheries. The ecological effects caused by fishing gear that is lost when cut or broken after snagging on the bottom is a growing concern to managers and scientists. Few data exist, however, to assess the impacts of lost fishing gear to benthic organisms and habitat structure. In this study, 63 offshore coral reef and hard-bottom sites were surveyed during 2001 to quantify the impacts of lost fishing gear to coral reef sessile invertebrates. Lost hook-and-line fishing gear accounted for 87% of all debris (N=298 incidences) encountered and was responsible for 84% of the 321 documented impacts to sponges and benthic cnidarians, predominantly consisting of tissue abrasion causing partial individual or colony mortality. Branching gorgonians (Octocorallia) were the most frequently affected (56%), followed by milleporid hydrocorals (19%) and sponges (13%). Factors affecting the impacts of lost fishing gear include sessile invertebrate density, the density of lost fishing gear, and gear length. While lost hook-and-line fishing gear is ubiquitous in the Florida Keys, less than 0.2% of the available milleporid hydrocorals, stony corals, and gorgonians in the habitats studied are adversely affected in terms of colony abrasions and partial mortality.     

Entanglement of monofilament fishing lines and coral death

This study examined the extent of damage by monofilament fishing lines on the cauliflower coral (Pocillopora meandrina) colonies at a popular cast fishing site in Oahu, Hawaii in March 1998. Sixty-five percent of coral colonies had fishing lines on their surface, and 80% of colonies were either entirely or partially dead. The percentage of entirely and partially dead colonies was positively correlated with the percentage of colonies entangled with fishing lines. Percent dead coral surface area was larger for colonies with fishing lines than colonies without fishing lines. In colonies with fishing lines, percent dead coral surface area was positively correlated with percent area with fishing lines. The high incidence of coral colonies with fishing lines and the three sets of significant results indicated destructive effects of monofilament fishing lines to P. meandrina corals. There is thus a clear case that reefs should be protected not only from the effects of excessive removal of fishes, but also from the effects of unsuccessful fishing that results in fishing-line entanglement on corals.     

Coral reefs: Conserving the evolutionary sources

The current worldwide degradation of coral reefs constitutes an international problem that calls for immediate attention. A multitude of conservation hotspots scattered over the circumtropical seas have been identified, but there has been no general agreement as to how to attack the problem. The major difficulty seems to be the lack of a priority system. Are some reefs more important than others? If so, where are they located and what needs to be done? Some reefs are located in areas where the biodiversity (species, genera, families) is exceptionally high and where there is evidence of past and present evolutionary production. These areas are called centres of origin and one is located in the Indo-Pacific Ocean and the other in the Atlantic. The Indo-Pacific centre, located in the East Indies Triangle, is considered to be the primary tropical center due to its broad geographic influence. The Atlantic centre, located in the southern Caribbean Sea, is considered a secondary centre because its influence is restricted to the tropical Atlantic. These centres, although occupying relatively small geographic areas, are evidently the source of dominant species that have played the major role in assembling coral reef communities across each ocean. The existence of the two centres permits one to realize that, in the coral reef environment, there is a geographical separation between process and pattern. Recognition of the separation will allow significant improvements in conservation planning. The evolutionary process in the centres must be protected in order to maintain the outlying diversity patterns.     

Storm-generated coral fragments - A viable source of transplants for reef rehabilitation

Coral reefs throughout the world have been damaged by storms, diseases, coral predators, temperature anomalies, and human activities. During the past three decades, recovery has been limited and patchy. Although a damaged coral reef cannot be restored to its original condition, interest in reef restoration is increasing. In a pilot project in the Caribbean (US Virgin Islands), storm-produced fragments of Acroporapalmata, A. cervicornis, and Porites porites were collected from donor reefs and transplanted to nearby degraded reefs. Sixty coral fragments were attached to dead-coral substrate (usually A. palmata skeletons), at similar depths from which they had been collected (1-3.5 m), using nylon cable ties. Seventy-five intact colonies were designated as controls. Study colonies were assessed at 6-month intervals for 2 years (1999-2001) and annually thereafter (through 2004). One-fourth of the 135 colonies and fragments monitored were alive at the conclusion of the 5-year study. Survival of control and transplanted A.cervicornis and P. porites was very low (median survival 2.4 and 1.8 years, respectively), with no significant differences between transplant and control colonies. Site and depth did not contribute significantly to A. palmata colony survival, but colony size and transplant/control status did. Probability of survival increased with colony size. Median survival for A. palmata was 1.3 years for transplant and 4.3 years for natural colonies when not controlled for size. A. palmata was the only viable candidate for reef rehabilitation. Storm swells were the primary cause of mortality.     

Establishing baselines for recovery in a marine reserve (Poor Knights Islands, New Zealand) using local ecological knowledge

Local ecological knowledge is a potentially valuable, but mostly untapped, resource for evaluating decadal-scale shifts in abundances of organisms. In this study, recollections of long-term divers were quantified to assess changes in underwater life at the Poor Knights Islands in temperate northeastern New Zealand from the 1960s to 2000s, in order to establish baselines for recovery since the islands were protected within a no-take marine reserve in late 1998. Data were validated against quantitative data from contemporary monitoring programmes (established in the late 1990s), with the divers conservative in that their reported changes were smaller than those from the scientific monitoring. The divers reported large (60–88%) and steady long-term declines in abundances of black corals (Lillipathes lilliei), tube sponges (Calyx imperialis), packhorse lobster (Sagmariasus verreauxi), and several large predatory fishes. There was little or no suggestion of recent recovery in these species following no-take protection. Only the sparid fish Pagrus auratus and sharks were considered to have substantially increased in numbers following no-take protection. Multivariate analysis of data derived from the divers’ recollections detected no signs of recovery at the community-level, although full no-take protection appeared to have stopped further change along the major axis of variation. Our results highlight the value of local ecological knowledge for investigating decadal-scale changes in reef biota and for providing a longer-term context for evaluating the efficacy of marine reserves.     

Alleviating impacts of anthropogenic activities by traditional conservation measures: can a small reef reserve be sustainedly managed?

Zoning schemes that are becoming an important management tool in large marine reserves, are difficult to implement in small reef areas. At the 3.4 km long reef of Eilat (Red Sea), a small (ca. 350 m of coastline) enclosure strategy has been enforced since 1992, while the remaining reef was left open to intense human activities. Here we have investigated for 2.5 y three populations of the branching coral Stylophora pistillata (3605 colonies) in a locality within the enclosed area (site NR) and in two areas open to the public, by tossing random quadrats at the shallow lagoonar zone (0.5-1.5 m depth). In the two open sites we found significantly higher levels of colony breakage (14-34% vs. 4-9% in the enclosed site), lower partial mortality levels of colonies (in the first 1.5 y; 7-9% vs. 23-30% at NR), higher recruitment (up to 3.0 vs. up to 0.9 colonies/m 2), 50% reduction in coral life span (10 vs. 20 y) and an estimated extinction period of 9-10 y for new cohorts as compared to >20 y in the enclosed site. Average colony size and maximal colony size were about half in the open sites. Live coverage fluctuated widely in all sites but was 3 times higher in the enclosed area (1.0-3.0% vs. 0.3-1.1%). Log-transformed size frequency distributions revealed, at the open sites, a shift from small towards medium-size classes and at the enclosed site, a shift from larger to medium size classes. We conclude that the enclosure of a limited core zone, although improved some ecological parameters, was not sufficient to compensate for stress imposed by anthropogenic activities. It is suggested to employ active restoration approaches, such as the “gardening concept”, as supplementary management tools.     

Deep-water scleractinian corals promote higher biodiversity in deep-sea meiofaunal assemblages along continental margins

Deep-water coral ecosystems are hot spots of biodiversity and provide habitats and refuges for several deep-sea species. However, their role in shaping the biodiversity of the surrounding open slopes is still poorly known. We investigated how meiofaunal biodiversity varies with and is related to the occurrence of deep-water living scleractinian corals and coral rubble in two deep-sea areas (the Rockall Bank, north-eastern Atlantic) and the Santa Maria di Leuca (central Mediterranean). In both areas, replicated sampling on alive and dead coral areas and from the adjacent slope sediments without corals (at the same and increasing depths) allowed us to demonstrate that sediments surrounding the living corals and coral rubble were characterised by higher meiofaunal biodiversity (as number of higher taxa, and nematode species richness) than the slope sediments. Despite the soft sediments surrounding the living coral having a higher nutritional value than those not associated with corals, with the opposite seen for coral rubble, the presence of both alive and dead corals had a significant effect on nematode assemblages. Our data suggest that, due particularly to the effects on habitat heterogeneity/complexity, both living coral and coral rubble promoted higher biodiversity levels than in surrounding slope sediments. We conclude that the protection of deep-water corals can be crucial to preserve the biodiversity of surrounding open slopes, and that the protection of dead corals, a so-far almost neglected habitat in terms of biological conservation, can further contribute to the maintenance of a high deep-sea biodiversity along continental margins.