Benthic Surveys Research Articles

Source and supply of sediment to a shoreline salient in a fringing reef environment

AbstractReef‐associated landforms are coupled to the health of the reef ecosystem which produces the sediment that forms and maintains these landforms. However, this connection can make reef‐fronted coastlines sensitive to the impacts of climate change, given that any decline in ecosystem health (e.g. decreasing sediment supply) or changes to physical processes (e.g. sea level rise, increasing wave energy) could drive the sediment budgets of these systems into a net erosive state. Therefore, knowledge of both the sediment sources and transport mechanisms is required to predict the sensitivity of reef‐associated landforms to future climate change. Here, we examine the benthic habitat composition, sediment characteristics (composition, texture, and age), and transport mechanisms and pathways to understand the interconnections between coastal morphology and the reef system at Tantabiddi, Ningaloo Reef, Western Australia. Benthic surveys and sediment composition analysis revealed that although live coral accounts for less than 5% of the benthic cover, coral is the dominant sediment constituent (34% on average). Sediment ages (238U/230Th) were mostly found to be thousands of years old, suggesting that the primary sediment source is relic reef material (e.g. Holocene reef framework). Sediment transport across the lagoon was quantified through measurements of ripple migration rates, which were found to be shoreward migrating and responsible for feeding the large shoreline salient in the lee of the reef. The derived sediment fluxes were comparable with previously measured rates of sediment production by bioerosion. These results suggest that sediment budgets of systems dependent on old (>103 years) source materials may be more resilient to climate change as present‐day reef health and community composition (i.e. sources of ‘new’ carbonate production) have limited influence on sediment supply. Therefore, the vulnerability of reef‐associated landforms in these systems will be dictated by future changes to mechanisms of sediment generation (e.g. bioerosion) and/or physical processes. © 2018 John Wiley & Sons, Ltd.

Artificial structures as a source of elevated detrital loads for sedimentary environments

Artificial structures, such as seawalls and breakwaters, are essential components of shoreline protection, yet they can have major consequences for marine organisms, particularly those in surrounding sediments. Improved understanding of the mechanisms by which artificial structures influence sedimentary habitats and the scale at which these mechanisms operate is needed to assess impacts of intensifying shoreline armoring on nearshore ecosystems. We examined detrital production on artificial structures and influx into surrounding sedimentary habitat in Puget Sound, Washington. Benthic surveys of hard substrates and drift composition indicated that red macroalgae and encrusting invertebrates were the major producers of detrital material on subtidal artificial structures in the region. Core samples collected at three distances (1, 7, and 15 m) from selected artificial structures revealed that these materials were moving into adjacent sedimentary seascapes and becoming incorporated into the upper layers of sediment. Though detrital influx occurred only in the immediate vicinity of artificial structures, it altered sediment characteristics considerably, increasing the quantity of shell fragments and thus the average grain size, as well as the concentration of red macroalgal detritus in sediments. Furthermore, rapid turnover rates of macroalgal detritus in experimental sediment plots suggested the influx of red macroalgal material from artificial structures was a frequent occurrence. These results indicate that elevated detrital influx is a persistent process in habitats bordering artificial structures in Puget Sound. Further work is needed to assess ecosystem response to detrital influx and to understand detritus-related impacts of shoreline armoring at the landscape scale.

Characterising the invertebrate megafaunal assemblages of a deep-sea (200–3000 m) frontier region for oil and gas exploration: the Great Australian Bight, Australia

The first systematic benthic survey in the deep sea (200–3000 m) of Australia’s Great Australian Bight (GAB) was undertaken in 2015 to characterise the invertebrate megafauna, and to inform the selection of indicators and metrics for ecological monitoring ahead of oil and gas exploration. The survey yielded more than 629 species of invertebrate megafauna; of the 376 species with distributional data, 92 (25%) were undescribed and 77 were new records for Australian waters. The families and genera present were all known to occur in the deep sea and many species had been previously recorded in Australia and worldwide; faunal composition was broadly typical for temperate deep-sea regions. The highest diversities (>80 putative species, or Operational Taxonomic Units, OTUs) were recorded within the higher taxa Demospongiae, Decapoda, Gastropoda and Echinodermata. Multispecies analyses showed clear changes in the assemblage structure with depth; sponges and echinoderms dominated the overall biomass and density, with the former being more prominent in shallower depths. The assemblage structure is consistent with the GAB being a single provincial-scale bioregion, with no longitudinal pattern in assemblage, biomass or density distribution. Approximately 70% of species that could be assigned biogeographic data were previously recorded from Australia, with less than half (146 species, 39%) previously known from the GAB. Only two described species, the crab Choniognathus granulosus and barnacle Arcoscalpellum inum, appear restricted to the GAB; it would be premature to assign any undescribed species as having endemic status. The clear eastwards biogeographic affinity of the GAB fauna is influenced by the relatively high deep-sea sampling effort to the east off southeastern Australia and New Zealand. Our survey of invertebrate megafauna at baseline (unperturbed) sites provides the basis to evaluate indicators and metrics using a reference-site monitoring approach. A robust (consistent species-level) taxonomic foundation will enable a variety of assemblage-level (composite) metrics (e.g. richness, diversity, distinctness) to be derived, and this is possible across several major taxa including Porifera, Cnidaria, Mollusca, Echinodermata and Crustacea. Species-level data also permit structural and functional changes (including recovery) to be assessed in response to disturbance. Where reference sites should be established can only be determined once the exploration phase of industry development is further advanced because the spatial scales of potential impact are highly activity-specific. However, our data show the high importance of depth to selecting monitoring sites because invertebrate megafaunal assemblage composition (turnover), diversity, and abundance are all highly correlated with depth. Conversely, latitude is not important because the central GAB is a single biogeographic province.

The highly competitive ascidian Didemnum sp. threatens coral reef communities in the Wakatobi Marine National Park, Southeast Sulawesi, Indonesia

Coral reefs in the Wakatobi Marine National Park (WMNP), Indonesia, are protected but have been degrading in several areas due to local anthropogenic stressors. In affected areas, benthic surveys revealed the occurrence of a dominant ascidian species of the genus Didemnum, which may negatively impact the benthic community composition and structure. We quantified the abundance, substrate preference, and growth rate of Didemnum sp. in non-degraded and degraded reefs to assess its impact on the benthic community. While Didemnum sp. occurred in similar high abundances in both, non-degraded (0.66%) and degraded (0.75%) reef sites, this species showed a substantially (>10-fold) increased growth rate in degrading reefs (2.7 ± 0.98% day−1 increase in colony size, compared to 0.17 ± 0.39% day −1 in non-degraded reefs). Furthermore, Didemnum sp. colonized many different substrates and showed the ability to overgrow live corals quickly. These observations indicate that Didemnum sp. can be a severe threat to a reef community by outcompeting live corals and call for further studies on the interaction between environmental pollution and Didemnum growth patterns in coral reefs.

New records of marine planktonic invertebrates from the Caribbean coast of Costa Rica

The coral reef at Cahuita National Park in the Caribbean coast of Costa Rica represents very diverse marine ecosystem. Most of this diversity knowledge has been the result of benthic surveys, while very little is known from pelagic studies. A zooplankton survey sampling was conducted monthly from September 2010 to August 2011, finding new records of marine invertebrates: 32 for the Caribbean coast of Costa Rica, seven for Costa Rican water and 16 for the Caribbean coast of Central America. These reports include the hoplitomella larva of the sponge Thoosa sp., larval stages of three lophophorates, seven families, five genera and six species of polychaetes, a juvenile of the lancet Branchiostoma (Phylum Chordata, Subphylum Cephalochordata) and four pelagic chordates. Analyzing the zooplankton of Cahuita, is an essential approach to studying not only the diversity, but also enhances the possibility of better understanding the ecological goods and services that the coral reef can provide.

Salinity gradient meiobenthos distribution on the Razdolnaya River’s estuary

The paper studies salinity gradient meiobenthos distribution based on the results of the benthic surveys of the Razdolnaya estuary (the Sea of Japan, Amursky Bay). The density was increased with salinity growth on the Razdolnaya Rivers estuary. Meiobenthos was comprised by 8 taxonomic groups (Nematoda, Copepoda, Ostracoda, Oligochaeta, Mollusca, Amphipoda, Polychaeta и Chironomidae) with the dominance of nematodes. Most of meiobenthic species are presented by marine euryhaline species and registered throughout the Razdolnaya Rivers estuary. Fresh water species Dorylaimus chassanicus, Hofmaenneria gratiosa, Theristus brevisetosus and nematodes of the genera Paradontophora , widespread on estuaries of Far East of Russia, were dominated in meiobenthos in oligohaline zone of estuary; Monhystrella sp. Oncholaimium japonicum, Anoplostoma cuticularia, Daptonema inversum and Harpacticoid Copepods Remanea naksanensis, Onychocamptus mohammed, Huntemannia biarticulatus, Halectinosoma sp. were dominated in mesohaline zone. Nematode community are changed by zones throughout the estuary: Paradontophora genera are dominated in freshwater and olihaline zones, as well as freshwater species ( Dorylaimus chassanicus, Hofmaenneria gratiosa, Theristus brevisetosus ) were presented; Monhystrella sp. are dominated and freshwater spicies are decreased in the number at the mesohaline zone; Paracanthonchus macrodon, Onсholaimium paraolium, Sabatieria finitima, Dorylaimopsis peculiaris and S. palmaris are dominated at the euhaline zone. The nematocenes of inner part of estuarine zone arent characterized by specific species assemblage and consist of species typical for nematode community of shallow water and of marine zones.

Coral reefs for coastal protection: A new methodological approach and engineering case study in Grenada

Coastal communities in tropical environments are at increasing risk from both environmental degradation and climate change and require urgent local adaptation action. Evidences show coral reefs play a critical role in wave attenuation but relatively little direct connection has been drawn between these effects and impacts on shorelines. Reefs are rarely assessed for their coastal protection service and thus not managed for their infrastructure benefits, while widespread damage and degradation continues. This paper presents a systematic approach to assess the protective role of coral reefs and to examine solutions based on the reef's influence on wave propagation patterns. Portions of the shoreline of Grenville Bay, Grenada, have seen acute shoreline erosion and coastal flooding. This paper (i) analyzes the historical changes in the shoreline and the local marine, (ii) assess the role of coral reefs in shoreline positioning through a shoreline equilibrium model first applied to coral reef environments, and (iii) design and begin implementation of a reef-based solution to reduce erosion and flooding. Coastline changes in the bay over the past 6 decades are analyzed from bathymetry and benthic surveys, historical imagery, historical wave and sea level data and modeling of wave dynamics. The analysis shows that, at present, the healthy and well-developed coral reefs system in the southern bay keeps the shoreline in equilibrium and stable, whereas reef degradation in the northern bay is linked with severe coastal erosion. A comparison of wave energy modeling for past bathymetry indicates that degradation of the coral reefs better explains erosion than changes in climate and historical sea level rise. Using this knowledge on how reefs affect the hydrodynamics, a reef restoration solution is designed and studied to ameliorate the coastal erosion and flooding. A characteristic design provides a modular design that can meet specific engineering, ecological and implementation criteria. Four pilot units were implemented in 2015 and are currently being field-tested. This paper presents one of the few existing examples available to date of a reef restoration project designed and engineered to deliver risk reduction benefits. The case study shows how engineering and ecology can work together in community-based adaptation. Our findings are particularly important for Small Island States on the front lines of climate change, who have the most to gain from protecting and managing coral reefs as coastal infrastructure.

Amphipod family distributions around Iceland.

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.

Ecological assessment of the marine ecosystems of Barbuda, West Indies: Using rapid scientific assessment to inform ocean zoning and fisheries management.

To inform a community-based ocean zoning initiative, we conducted an intensive ecological assessment of the marine ecosystems of Barbuda, West Indies. We conducted 116 fish and 108 benthic surveys around the island, and measured the abundance and size structure of lobsters and conch at 52 and 35 sites, respectively. We found that both coral cover and fish biomass were similar to or lower than levels observed across the greater Caribbean; live coral cover and abundance of fishery target species, such as large snappers and groupers, was generally low. However, Barbuda lacks many of the high-relief forereef areas where similar work has been conducted in other Caribbean locations. The distribution of lobsters was patchy, making it difficult to quantify density at the island scale. However, the maximum size of lobsters was generally larger than in other locations in the Caribbean and similar to the maximum size reported 40 years ago. While the lobster population has clearly been heavily exploited, our data suggest that it is not as overexploited as in much of the rest of the Caribbean. Surveys of Barbuda’s Codrington Lagoon revealed many juvenile lobsters, but none of legal size (95 mm carapace length), suggesting that the lagoon functions primarily as nursery habitat. Conch abundance and size on Barbuda were similar to that of other Caribbean islands. Our data suggest that many of the regional threats observed on other Caribbean islands are present on Barbuda, but some resources—particularly lobster and conch—may be less overexploited than on other Caribbean islands. Local management has the potential to provide sustainability for at least some of the island’s marine resources. We show that a rapid, thorough ecological assessment can reveal clear conservation opportunities and facilitate rapid conservation action by providing the foundation for a community-driven policymaking process at the island scale.

Soft Bottom Communities in Marine Lakes Sisjajarvi and Linjalampi (Barents Sea).

Based on the data of benthic surveys of 2010-2012, three benthic communities: a shallow-water community with the dominance of Scoloplos spp., Nucula tennuis, and Scalibregma inflatum; a deep-water community with the dominance of Chaetosone sp.; and a community of mixed sediments, have been distinguished in soft sediments in marine lakes Sisjajarvi and Linjalampi. These communities are typically marine and similar to other communities in shallow areas of the Barents Sea. They mostly differ in a high abundance of the polychaete Scalibregma inflatum and a small number of echinoderms from the communities in other bays of the Barents Sea. The abundance of the polychaete S. inflatum indicates indirectly possible cases of anoxia in Lake Sisjajarvi.

The Distribution of Macrozoobenthos Taxa, as Potential Indicators of Vulnerable Marine Ecosystems in the Western Bering Sea: 1. Anadyr Bay Area

The composition of common species in some macrozoobenthos groups that are considered as potential indicators of vulnerable marine ecosystems (VME), in the Anadyr Bay area, Bering Sea have been determined based on the results of four benthic surveys using a benthic grab sampler (1985, 2005) and a bottom trawl (2008, 2012). These are soft corals (Gersemia rubiformis), sponges (Myxilla incrustans, Halichondria panicea, and Semisuberites cribrosa), ascidians (Halocynthia aurantium and Boltenia ovifera), bryozoans (Cystisella saccata and Flustra foliacea), barnacles (Chirona evermanni), and the brittle star (Gorgonocephalus eucnemis). The distribution of these animals has been mapped. Aggregations of immobile sestonophages (the former five groups) are formed on hard coarse-grained and mixed sediments in waters with higher hydrodynamic activity (along the southwestern and northeastern coasts of the Anadyr Bay, mainly at depths of 80–90 m). In some cases, sponges and bryozoans in the southern part of the area can descend to a depth of 250 m (in the Navarin Canyon). The mobile filterer G. eucnemis forms aggregations mainly on soft sediments in the central part of Anadyr Bay, at depths of 50–270 m, in the area of a localized spot of near-bottom cold water. According to the results of trawl surveys conducted in 2008 and 2012, the mean biomass of the sponges, the brittle star G. eucnemis, and the sea squirt B. ovifera did not change, whereas the mean biomass of the barnacle Ch. evermanni and sea peach H. aurantium decreased by 6.5 and 3.7 times, respectively. Since the level of trawl fishing activity in the region is not high, the hypothesis has been proposed that the decrease in the abundance of the latter two species is presumably caused by the natural dynamics of their population or can be related to the factor of randomness, as these species are caught in their mosaically distributed local aggregations.

Mapping sites of reef vulnerability along lagoons of Lakshadweep archipelago, Indian Ocean.

Tissue degradation and mediated mortality have turned into a major threat to coral reef systems around the world. Detailed knowledge on interactions of prime biological factors that mediate tissue loss and mortality is of paramount importance in understanding the prevailing reef health scenario and to trial management actions. In the present study, a series of benthic surveys were conducted in Lakshadweep islands to understand the interactions of plausible biological factors in causing tissue loss and mediated mortality. Interactions of biological scenarios were prioritized using hierarchical regression analysis. The hierarchical regression model analysis revealed black band disease (β=0.59; p<0.001) and algal interactions (β=0.48; p<0.001) as the major factors responsible for tissue-loss-mediated coral mortality in the region. The observations from the hierarchical analysis were used to derive vulnerability maps based on weighted overlay analysis. The vulnerability mapping revealed that lagoon of Kalpeni Island is very highly vulnerable to coral degradation with 683.5ha followed by Kavaratti (70.2ha), Bangaram (70ha), and Amini (47ha). Chethalath and Agatti lagoons were inferred as low vulnerable sites where coral reefs can sustain. The vulnerability maps derived can be used as a baseline observation to identify areas of very high vulnerability and specific stressor prevalent in those sites. This will be helpful in defining stressor and site-specific management plans.

Distribution of macrozoobenthic taxa - potential indicators of vulnerable marine ecosystems in the western part of Bering Sea. 1. Anadyr Bay area

Following recent tendencies in fisheries policy to ensure both sustainability of ecosystems and conservation of economically sustainable fisheries, protection of vulnerable resources with low direct economic value comes to the focus of fisheries management on ecosystem principles. One of the problems of modern fishing is a negative impact of bottom trawling because of destruction of benthic organisms vulnerable to mechanical impacts. This by-effect of fishing could affect negatively on functioning of bottom biocenoses, reproduction of exploited species, and decrease generally productivity of vulnerable marine ecosystems (VME). Potential VME indicators are determined for the area of the Anadyr Bay in the Bering Sea on the base of results of 4 benthic surveys using bottom sampler (1985, 2005) and bottom trawl (2008, 2012), as the most common species in some macrozoobenthic groups of epifauna. They are Gersemia rubiformis for soft corals, Myxilla incrustans , Halichondria panicea , Semisuberites cribrosa for sponges, Halocynthia aurantium , Boltenia ovifera for sea squirts, Cystisella saccata , Flustra foliacea for bryozoans, Chirona evermanni for barnacles, and Gorgonocephalus eucnemis for brittle stars. Their distribution is mapped. According to their life history and feeding habits, these species-indicators are divided onto two groups: immobile sestonophages (alcyonarians, sponges, ascidians, bryozoans, cirripedians) and mobile filtrators (brittle stars). The first group prevails on hard and mixed grounds mainly along southwestern and northeastern coasts of the Anadyr Bay at the depths of 80-90 m (sponges and bryozoans - to 250 m in the Navarin Canyon) with relatively warm water, active hydrodynamics and high biological productivity. The second group represented by G. eucnemis dominates on soft sediments in the central part of the Anadyr Bay with the depths of 50-270 m occupied by the cold water pool. Quantitative distribution of brittle star, on the one hand, and barnacles with sea squirts, on the other hand, is alternative to each other. On the contrary, barnacles, sponges and sea squirts have similar distribution of the biomass, being complementary species. Distribution patterns of all species-indicators are stable for many decades. However, biomass of some these species has changed in the southern Anadyr Bay between the similar surveys conducted in the 2008 and 2012: the mean biomass of barnacle Ch. evermanni and sea squirt H. aurantium had decreased in 6.5 and 3.7 times, respectively, whereas the mean biomass of sponges, brittle star G. eucnemis and sea squirt B. ovifera did not change. Bottom trawl fishery is not active in the northwestern Bering Sea, moreover, the habitats of immobile sestonophages with hard grounds are avoided by bottom trawlers being dangerous for fishing gears, so the observed decreasing of two species abundance is presumably caused by natural reasons or is a random error of the mosaic-distributed stocks assessment with insufficiently dense sampling grid.

Spatiotemporal Dispersal and Deposition of Fish Farm Wastes: A Model Study from Central Norway

Abstract A spatially explicit coupled hydrodynamic-mass transport model system was used to simulate dispersal of particulate organic matter from Atlantic salmon (Salmo salar) farming in central Norway. Model setups of 32 m horizontal resolution were run for periods of up to 650 days for 3 sites of different oceanographic characteristics: one fjord location, one medium-exposed location influenced by fjord water and one coastal location. Records on feed used for each cage at each location were converted to feces released based on a published mass balance model. The results from the simulations were compared with scores from corresponding mandatory benthic surveys (MOM-B) of the sediment layer beneath the farms. The correspondence between simulated and measured thickness of the sediment layer was good, and improved with the inclusion of resuspension processes. At all sites the distribution of organic matter in the bottom layer was non-homogeneous, with significant temporal variation and transport and settling of matter up to at least 0.5 km away from one of the farms. Our results indicate that the monitoring practice used in Norway until now, with a few sediment grab samples taken mainly within the fish farm, may not adequately determine the areal impacts of all salmon farming operations. The patchy distribution of organic matter and the correspondence between simulation and survey results is attributed to the use of full 3D current fields of a high spatiotemporal resolution and a good model for resuspension processes that some previous model studies have failed to properly account for.

Toxicity of oil and dispersant on the deep water gorgonian octocoral Swiftia exserta, with implications for the effects of the Deepwater Horizon oil spill

Benthic surveys of mesophotic reefs in the Gulf of Mexico post Deepwater Horizon (DWH) showed that Swiftia exserta octocorals exhibited significantly more injury than in years before the spill. To determine the vulnerability of S. exserta to oil and dispersants, 96h toxicity assays of surrogate DWH oil water-accommodated fractions (WAF), Corexit® 9500 dispersant, and the combination of both (CEWAF) were conducted in the laboratory. Fragment mortality occurred within 48h for some fragments in the dispersant-alone and oil-dispersant treatments, while the WAF group remained relatively unaffected. The 96h LC50 values were 70.27mg/L for Corexit-alone and 41.04mg/L for Corexit in CEWAF. This study provides new information on octocoral sensitivity to toxins, and indicates that combinations of oil and dispersants are more toxic to octocorals than exposure to oil alone. These results have important implications for the assessment of effects of the DWH spill on deep-water organisms.

A decadal analysis of bioeroding sponge cover on the inshore Great Barrier Reef

Decreasing coral cover on the Great Barrier Reef (GBR) may provide opportunities for rapid growth and expansion of other taxa. The bioeroding sponges Cliona spp. are strong competitors for space and may take advantage of coral bleaching, damage, and mortality. Benthic surveys of the inshore GBR (2005–2014) revealed that the percent cover of the most abundant bioeroding sponge species, Cliona orientalis, has not increased. However, considerable variation in C. orientalis cover, and change in cover over time, was evident between survey locations. We assessed whether biotic or environmental characteristics were associated with variation in C. orientalis distribution and abundance. The proportion of fine particles in the sediments was negatively associated with the presence-absence and the percent cover of C. orientalis, indicating that the sponge requires exposed habitat. The cover of corals and other sponges explained little variation in C. orientalis cover or distribution. The fastest increases in C. orientalis cover coincided with the lowest macroalgal cover and chlorophyll a concentration, highlighting the importance of macroalgal competition and local environmental conditions for this bioeroding sponge. Given the observed distribution and habitat preferences of C. orientalis, bioeroding sponges likely represent site-specific – rather than regional – threats to corals and reef accretion.

Sources and threats of chronic tissue loss on coral reefs in the Lakshadweep Islands, Indian Ocean

AbstractTissue degradation and resulting mortality are major threats to coral reefs around the world. Information on interactions of the major environmental factors that mediate tissue loss and mortality in coral reefs is of great importance. It is essential to understand the prevailing reef health conditions and to develop appropriate management actions. In the present study, a series of benthic surveys conducted in the Lakshadweep Islands revealed the interaction of major biological factors in causing tissue loss and mortality. Hierarchical regression analysis revealed interactions of various environmental scenarios. Tissue loss was prevalent in islands with high cover of massive corals (m = 20.91) and low in islands dominated by branching corals (m = 0.61). Hierarchical regression analysis revealed black band disease (β = .59; p &lt; .001) and algal interactions (β = .48; p &lt; .001) to be major factors responsible for coral mortality caused by tissue loss in the region.

Long-term change in epibenthic assemblages at the Prince Edward Islands: a comparison between 1988 and 2013

As proxies and indicators of environmental conditions, offshore benthic assemblages are pertinent to understanding global change. To investigate long-term change in epibenthic assemblages, we compared digitally reprocessed historical (1988) and repeat (2013) benthic survey photographs from nearshore (40–130 m) and inter-island locations (140–500 m) at the sub-Antarctic Prince Edward Islands. Given changing interactions between regional oceanography and terrestrially influenced productivity at the islands, temporal change in the benthos is likely, and is expected to be dependent on proximity to the islands (nearshore vs. inter-island). Multivariate PERMANOVA analyses identified a significant interaction effect on epibenthic assemblages (Year × Location), with significant dispersion effects defining temporal differences within the inter-island region but not in the nearshore area. Differences in epibenthic assemblages observed between 1988 and 2013 were found to be driven primarily by increased abundances of several common suspension feeding taxa, including a significant increase in the density of a key bioengineering species, the polychaete Lanice marionensis. These higher abundances are congruent with local trophic evidence of long-term, climate-related shifts towards greater allochthonous food supply to the benthos. Given this congruence, a unifying explanation for the observed temporal differences in epibenthic assemblages is that long-term alteration of the position of the sub-Antarctic Front has changed the local primary productivity regime and hence the flux of food to the benthos. This study provides the first direct support for the notion of long-term change in epibenthic assemblage composition at the islands.

OIL BEHAVIOUR AND THE RESPONSE TO A SUNKEN OIL SPILL OF SLURRY IN QUINTERO BAY, CHILE

ABSTRACT Slurry oils are one of the few groups of oils that have a density greater than full salinity seawater. Slurry spills at sea are rare, but when they do occur, the response can be difficult, with low final recovery rates. Oil spill response planning and recovery techniques have been refined over many years and the research and development of most methods has been underpinned by the principle that oil floats on water. This recent case study provides an example of the behavior of a slurry spill and the subsequent response operations. A leak of an API gravity 4° slurry occurred from a submarine pipeline in Quintero Bay, Chile, on 14th May 2016. The oil sank to the adjacent sea bed and covered an area of approximately 10,000 m2 in water depths of 18–22 m. The initial response involved over 20 dry-suit divers with surface air to recover the oil with vacuum hoses. These were then supplemented by four diver-operated vacuum dredges. Fortunately weak bottom currents did not redistribute the oil; nevertheless “sea bed booms” were deployed around the perimeter to prevent migration. These “booms” were initially a screen mesh that was later supplemented by sturdier metal frame screens deployed around the zone of the sunken oil in a zigzag configuration. Baseline benthic sediment samples were collected from the adjacent unaffected area and subsequently from the treatment area after completion of operations. A benthic SCUBA SCAT survey using a track-line positioning system was conducted to systematically document the distribution of the oil and post-treatment systematic ROV survey ensured that the end-point oiling conditions had been achieved.

Environmental indicators from underwater soundscapes and simultaneously collected non-acoustic data

Drawing environmental conclusions from underwater acoustic recordings alone can to be challenging as most received sounds, especially in shallow water, are from sources that cannot easily be classified. This presentation will discuss two ongoing projects in which soundscapes were recorded simultaneously with non-acoustic, validating environmental data. In one case, acoustic data were collected simultaneously with bottom composition, organism censuses, and night-time time-lapse imagery over shallow reefs in the Hawaiian Islands. Multivariate analysis showed that areas defined by a “cool tropics” oceanographic regime grouped along a principal component parallel to monotonically increasing acoustic frequency: protected or more remote sites produced soundscapes that featured greater levels of low frequency (<2 kHz) biological sound. Degraded and/or algae dominated sites produced soundscapes featuring higher levels of high frequency (2-20 kHz) sound. The second case involves experimental work using hyperspectral optical data and simultaneously obtained acoustic recordings in shallow water, combined with in-situ spectrophotometer readings and visual benthic surveys. Optical reflectance and sound are produced through completely different mechanisms, yet the underlying environmental phenomena we wish to evaluate exhibit both. This presentation will discuss the potential of fusing these data in order to enhance our understanding of the shallow water environment. [Work supported by ONR.]