To be able to assess progress towards “Good Environmental Status” adopted across European Member States, and by the United Kingdom through its 3-stage Marine Strategy, contaminant concentrations and ...their biological effects need to be assessed in environmental samples by comparison to assessment criteria. This study examines the variability of concentrations (inter- and intra- species variation) of three priority heavy metals (Hg, Cd and Pb) and six additional trace metals and metalloids (As, Ni, Se, Zn, Cu and Cr) in twenty-three species across four trophic levels from different locations around Scotland. Trophic magnification factors (TMFs) were calculated using two methods for metals/metalloids possessing a significant trophic relationship (Hg, Cd, Cu, Ni and Zn) to refine and improve the application of TMFs to assess and predict biomagnification risk of metals/metalloids to biota in the environment. It was concluded that a reasonable balance in sample numbers of lower- versus higher-trophic level organisms is highly recommended when calculating TMFs and appropriate species selection is vital to ensure TMFs accurately represent the selected ecosystem.
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•Mixed effects model analysis revealed Hg, Cd, Cu, Ni and Zn to have a significant relationship with trophic level.•An unbalanced dataset influenced TMFs and in some cases, the overall conclusion on trophic transfer.•The detected and trophic adjusted Hg concentrations in shark, fish and invertebrates were all above the EU Hg biota EQS.•Factors required for the calculation of reliable TMFs raises questions on its application for environmental assessments.
Contracting Parties to the OSPAR Convention for the Protection of the Maine Environment of the North-East Atlantic are required to undertake monitoring and assessment of both inorganic and organic ...contaminants. There is a requirement to assess contaminants across different trophic levels on an ecosystem-specific basis. However, this is currently constrained by the availability of relevant samples to cover the full range of trophic levels. This study investigates the variability (inter- and intra-species variation) of the concentrations and distributions of thirty-two polychlorinated biphenyl (PCB) congeners and nine polybrominated diphenyl ether (PBDE) congeners in twenty-six species covering four trophic levels from different geographic locations around Scotland. Trophic magnification factors (TMFs) were calculated using a traditional method and a balanced method for both the ICES-7 PCBs and BDE47, to refine and improve the application of TMFs to assess and predict biomagnification risk to biota in the marine environment. There were clear differences in congener percentage distribution between sample categories and species, with differences influenced by physiological processes and eco-biological parameters. Trophic magnification was found to occur for the ICES-7 PCBs and BDE47 using the traditional method, with the highest degree of trophic magnification reported for CB52. An unbalanced dataset was found to influence the calculated TMF and in some cases, the overall conclusion of the trophic transfer of PCB and PBDE congeners. The balanced method is highly recommended for calculating TMFs to ensure that the TMF is a true indication of the biomagnification potential, particularly when conducting regional comparisons for which sampling requirements are difficult to achieve.
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•All marine mammals, demersal and pelagic fish had detectable PCBs in their tissues.•Diet contributed to PCB and PBDE concentration and congener variability.•Trophic magnification was found to occur for the ICES-7 PCBs and BDE47.•An unbalanced dataset was found to influence the calculated TMF.•The TMF of CB52 calculated in this study was higher than reported globally.
Reef fish assemblages across tropical and temperate latitudes are increasingly threatened by human impacts and climate change. Accurate and efficient survey methods are essential for quantifying ...these communities to inform management strategies. Imaging sonars (ISs) are high-frequency acoustic devices that produce camera-like images of objects. Unlike optical instruments, IS functions effectively in turbid and dark water and has proven valuable in detecting fishes in poor visibility and at night. Abundance, species richness, and fish size are desirable metrics in most reef fish surveys. This review investigates previous attempts to quantify these metrics using IS across different habitats. These metrics are often quantified in comparison with alternative methods (e.g. cameras, extractive techniques). This review examines the causes of agreement or incongruence between estimates from IS and estimates from these alternatives. Any instrument employed to quantify reef fishes should be able to operate in structurally complex habitats, and thus the ability of IS to function in these circumstances is also reviewed. Finally, 5 notable limitations of IS are described and solutions discussed. Overall, this review underlines the net value of IS for surveying reef fishes but advises using alternative methods to complement IS estimates of abundance, species richness, and fish size.
As the offshore hydrocarbon industry matures and decommissioning activities are expected to increase, there is a requirement to assess the environmental consequences of different pipeline ...decommissioning options. Previous research on fish and other ecological components associated with pipelines has focused on examining species richness, abundance and biomass surrounding structures. The extent to which subsea pipelines mimic or alter ecosystem function compared with nearby natural habitats is unknown. We analyse differences in fish assemblage biological trait composition and the functional diversity at exposed shallow-water subsea pipelines, nearby natural reef and soft sediment habitats, using mini stereo-video remotely operated vehicles (ROV). Habitats significantly differed in assemblage trait composition. The pipeline and reef habitats shared a more similar functional composition and had the presence of key functional groups required for the development and maintenance of healthy coral reef systems. The reef habitat had the greatest functional diversity, followed by the pipeline habitat and soft sediment habitat respectively.
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•Understanding subsea pipeline ecology is crucial for assessing decommissioning options.•The functional composition of fish was distinct among habitats.•Pipeline habitat had defined functional grouping and species separation.•Reef habitat had greatest functional diversity, followed by pipeline and soft sediment.•Pipelines had key functional groups required for the development of healthy coral reef systems.
Offshore oil and gas platforms (OGP) have been installed worldwide and initially with limited consideration given to the nature of their positive or negative long-term interactions with the natural ...marine habitats. However, as OGP reach the end of their useful life, with many being decommissioned and removed, it is timely to review the growing evidence of the association of marine biota with OGP to provide a summary and synthesis for policy makers and to give insight to decisions in increasingly crowded marine spatial plans. In the last decade, there has been rapid increase in studies concerning the ecological role of OGP. This research reveals strong contextual difference between platforms in different geographical regions, but all OGP add to local biodiversity particularly where hard substrata are introduced to areas dominated by depositional (mud and sand) habitats. This includes the attraction and increased productivity of fish, sessile invertebrates, and algae while also affecting change in the benthic habitats beneath platforms. There also evidence of the OGP changing local hydrodynamics conditions with effects on phytoplankton and local scour. In terms of the biota associated with OGP, water depth is a major driver of community type across systems. This study emphasises that while knowledge of OGP communities and species has improved, there are still significant knowledge gaps that may prevent the most environmentally beneficial decisions being made around decommissioning. There are few studies following the effect of decommissioning (topping, toppling, or removal) on the ecology of the systems as they change with time (longitudinal research) for the decommissioning event. There is also a need for more studies comparing the biodiversity and functionality of OGP system to artificial and natural reefs and habitats to better understand the ecological cost-benefit of decommissioning scenarios. Finally, commercial data is often unavailable and even when available, surveys are often conducted using varied methodology that prevents comparative analysis. By imposing/agreeing standards and sharing data around the ecological cost-benefit of decommissioning strategies, improve policy guidance concerning OGP planning, and management might emerge.
Scotland's marine food webs support a diversity of species and habitats. They contribute to maintaining the balance of the natural environment. Previous studies show that these ecosystems are ...contaminated by persistent organic pollutants and trace metals; with animals in higher trophic levels (e.g. cetaceans and pinnipeds) containing concentrations that are among the highest found in the ocean. Contaminants represent one of many pressures to which species and habitats are exposed. In assessing the contribution of contaminants to the overall pressure, measuring contaminants at a specific trophic level and then using trophic magnification factors (TMFs) to estimate concentrations at other trophic levels permits assessments across the food web, as well as allowing the adjustment of contaminant concentrations to a particular trophic level for comparison to assessment criteria. Fatty acid (FA) signatures and stable isotope (SI) ratios were used to develop a picture of Scottish marine food web ecology and reliably ascribe trophic levels to a wide range of species. Fatty acid trophic markers (FATMs) were used as trophic level indicators and with SI analysis, permitted identification of the mean trophic level of each species and determination of the feeding patterns and predator-prey relationships existing in the Scottish marine food web. Two hundred and eleven (211) samples comprising of seven fish species, one shark species, fourteen marine invertebrate species, three marine mammal species and two zooplankton species from different locations around Scotland were found to have mean trophic levels ranging from 1.47 ± 0.11 in zooplankton to 5.02 ± 0.35 in harbour seal. Fatty acid profile showed specific dietary information which differed between the eleven taxonomic classes and twenty-seven species. The organic and inorganic contaminant concentrations of the species for which trophic level has been determined, together with TMFs, will be reported in future papers.
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•Trophic levels and feeding patterns within Scottish marine food webs were investigated.•The complexity in fatty acid profiles and stable isotope ratios is due to multiple influences.•Significant complexity can occur within a single trophic level.•Marine assessments must use a multi-factorial approach when investigating ecological dynamics.•Data will be used to determine contaminant trophic magnification factors.
Imaging sonars are increasingly being utilised in fish surveys in conjunction with or as substitutes for optical instruments. To justify the use of imaging sonars, we must first describe their ...application, limitations, and efficacy compared to optics. This study compared quantitative data of fish assemblages obtained using imaging sonars operating at four frequencies (0.75, 1.2, 2.1, and 3 MHz) with simultaneous optical camera footage at two artificial reefs. Fish densities were on average three times higher for sonar than optics. Greater detection by the sonar was attributed to site-attached fishes that were camouflaged against the artificial reefs or the adjacent seabed, which could be discriminated by imaging sonar, but not using optics. This suggests that differences in habitat and fish assemblage composition could influence the relative performance and density estimates of imaging sonar versus optics. Several limitations of imaging sonar were identified that need to be accounted for in future survey designs, including: discriminating fishes from benthic growth; an inability to detect fishes within complex habitat structures; and seabed and side-lobe interferences that truncate survey volume. Overall, this study demonstrates the value of imaging sonar for quantifying fish communities and describes limitations and recommendations for their deployment in future surveys.
There is growing interest in understanding the ecological benefits of oil and gas structures. This is the first reported case of the spawning aggregation and mating behaviour of bigeye trevally, ...Caranx sexfasciatus, associated with an oil and gas platform, demonstrating that oil and gas jackets are capable of not only attracting large aggregations of fish, but can provide suitable conditions for reproductive purposes. Fish spawning aggregations (FSAs) are highly vulnerable events that are vitally important for the persistence of many fish species. Urgent protection and conservation of FSA sites is required to secure them from the threat of overfishing. The findings of this study bring into question the management strategies required for oil and gas structures, particularly related to removal during decommissioning, or where structures are left in place and safety exclusion zones no longer apply. These aggregations and behaviours were captured using underwater stereo-video Remotely Operated Vehicle (ROV) methods, allowing for detailed observations.
•Bigeye trevally, Caranx sexfasciatus, were observed spawning at an oil and gas platform jacket in the Gulf of Thailand.•The platform is likely to have site characteristics conducive to spawning for multiple species, similar to a “pinnacle”.•Trevally were observed spawning on the later side of the wider regional spawning period.•Fertilised eggs and larvae may travel to the nearby natural reef (∼150 km away) or mangroves.•Findings of this study contribute to the increasing evidence base that oil and gas platforms provide ecological value.
Abstract Methods that supplement optical instruments with bait, such as baited remote underwater video (BRUV), are used worldwide to detect and quantify marine life. Optical instruments only detect ...targets within visible range, such that BRUVs may underestimate fishes in light‐limited habitats, especially fishes that respond to the bait at ranges beyond visibility. Alternatively, light‐independent instruments (e.g., imaging sonars) can detect and quantify fishes regardless of visibility. This study presents the first application of a baited imaging sonar (BISON), deployed to survey fishes around a small, shallow artificial habitat in a turbid embayment in southern Florida. To establish the influence of bait on fish detection, BISON trials were alternately conducted alongside deployments of an unbaited control, with a high‐definition camera integrated to ascertain visibility and inform species composition. For fishes of two size classes, larger (> 30 cm) and smaller (10–30 cm), maximum density (MaxD) and range of detection were quantified. Although the densities of larger and smaller fishes quantified by the BISON and unbaited control did not differ, over 55% of larger fishes were detected at ranges beyond maximum visibility, with asymptotes in fish density on the BISON identified at 15–20 min and 5–10 min for larger and smaller fishes, respectively. Overall, this study demonstrates the potential of BISONs as both a complementary and alternative method to BRUVs for quantifying fishes, especially in habitats of limited visibility. Future applications of BISONs in other habitats will further demonstrate its value as a tool to detect and enumerate aquatic assemblages.
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