Elevated fish densities extend kilometres from oil and gas platforms.

Thousands of offshore oil and gas platforms have been installed throughout the world's oceans and more structures are being installed as part of the transition to renewable energy. These structures increase the availability of ecological niches by providing hard substrate in midwater and complex 3D habitat on the seafloor. This can lead to 'hotspots' of biodiversity, or increased densities of flora and fauna, which potentially spill over into the local area. However, the distances over which these higher densities extend (the 'range of influence') can be highly variable. Fish aggregate at such structures, but the range of influence and any implications for wider fish populations, are unclear. We investigated the relationship between fish and platform areal densities using high resolution fisheries acoustic data. Data were collected in the waters surrounding the vessel exclusions zones around 16 oil and gas platforms in the North Sea, and throughout the wider area. We estimated densities of schooling fish using echo-integration, and densities of non-schooling fish using echo-counting. At 10 platforms, non-schooling fish densities were elevated near the platform relative to background levels in the equivalent wider area. The range of influence, defined here as the range to which fish densities were elevated above background, varied from 0.8 to 23 km. In areas of high platform density, fish schools were encountered more often, and non-schooling fish densities were higher, when controlling for other sources of environmental variation. This is the first time such long-range effects have been identified; previously, ranges of influence have been reported in the order of just 10s-100s of metres. These findings suggest that the environmental impact of these structures may extend further than previously thought, which may be relevant in the context of upcoming management decisions around the decommissioning of these structures.

Evaluating the effect of the incidence angle of ALOS-2 PALSAR-2 on detecting aquaculture facilities for sustainable use of coastal space and resources.

Background: Driven by the growing world population, aquaculture plays a key role in meeting the increasing demand for food. However, aquaculture facilities in Japan are widely installed in coastal waters where natural disasters, such as typhoons and tsunamis, might wash these facilities away, thereby interfering with maritime navigation safety. Therefore, it is imperative to efficiently monitor the state of aquaculture facilities daily, particularly after a disaster in real time. To this end, several new space-borne L-band synthetic aperture radars (SARs) continue to be launched now and in the future, whose utilizations are expected to increase nationally and internationally. An example is the Japan Aerospace Exploration Agency, currently operating a SAR that can be operated day and night, and even under cloudy conditions, called ALOS-2 PALSAR-2. Methods: Based on the above facts, this study evaluated the effect of the incidence angle of ALOS-2 PALSAR-2 HH single-polarization data, using 3 m spatial resolution, on aquaculture raft detection. As the study site, we selected Ago Bay, located on the Pacific coast of Mie Prefecture in central Japan since the Nankai Trough Megathrust Earthquake and tsunamis have been predicted to occur in the future around this area. Then, we analyzed the sigma zero (backscattering coefficient) of aquaculture rafts and their surrounding sea surfaces, including the relationships between satellite orbits and aquaculture raft directions. Results: Investigations revealed that the optimum incidence angle for detecting aquaculture rafts in this study was 33.8°-45.1°. Differences in the sigma zero values existed between the ascending and descending orbits. However, the incidence angles differed on the orbits. Then, differences in the median sigma zero values across a range of incidence angles were evaluated under the descending orbit. In addition, when the directions of the aquaculture rafts were closely perpendicular to the satellite orbit, aquaculture rafts tended to show the highest values of sigma zero due to Bragg resonance scattering. Hence, this knowledge may allow for the rapid detection of aquaculture rafts during an emergency without going on-site.

Locomotory activity and feeding strategy of the hadal munnopsid isopod Rectisura cf. herculea (Crustacea: Asellota) in the Japan Trench.

Benthic fauna in the hadal zone (6500-11,000 m) rely on maintaining sufficient locomotory activity to exploit a low, patchy and uniquely distributed food supply while exposed to high pressure, low temperatures and responding to predator-prey interactions. Very little is currently known about the locomotory capabilities of hadal fauna. In situ video footage of the isopod Rectisura cf. herculea (Birstein 1957) (Asellota, Munnopsidae) was obtained from 6945 and 7703 m deep in the Japan Trench (NW Pacific Ocean). Measurements of locomotion revealed routine walking speeds of 0.19 ± 0.04 BL s(-1) (mean ± s.d.), increasing to 0.33 ± 0.04 BL s(-1) if naturally perturbed by larger organisms. When immediately threatened by the presence of predators (decapod crustaceans), the isopods are capable of eliciting backward escape jumps and burst swimming escape responses of 2.6 ± 1.5 BL s(-1) and 4.63 ± 0.9 BL s(-1), respectively. These data suggest no significant reduction in locomotory capability despite the extreme depths in which they inhabit. These observations also revealed the isopod to be a bait-attending and aggregative species and suggest that it may not be obligatorily selecting infaunal food sources as previously thought.

Trench connection.

'Trench Connection' was the first international symposium focusing primarily on the hadal zone (depths greater than 6000 m). It was held at the University of Tokyo's Atmosphere and Ocean Research Institute in November 2010. The symposium was successful in having attracted an international collective of scientists and engineers to discuss the latest developments in the exploration and understanding of the deepest environments on Earth. The symposium sessions were categorized into three themes: (i) new deep-submergence technology; (ii) trench ecology and evolution; and (iii) the physical environment. Recent technological developments have overcome the challenges of accessing the extreme depths, which have in turn prompted an international renewed interest in researching physical and biological aspects of the hadal ecosystems. This bringing together of international participants from different disciplines led to healthy discussions throughout the symposium, providing potential opportunities and realizations of where the future of unravelling hadal ecology lies. Hadal science is still at relatively rudimentary levels compared with those of shallower marine environments; however, it became apparent at the symposium that it is now an ever-expanding scientific field.

Assessment of coastal anthropo-ecological system dynamics in response to a tsunami catastrophe of an unprecedented magnitude encountered in Japan.

On 11 March 2011, a catastrophic earthquake and subsequent tsunami hit the Pacific coast of northern Japan, devastating many of the towns, villages and coastal ecosystems located along the shoreline. To assess the impacts of the disaster, we investigated temporal dynamics of fish and epibenthic megafaunal community structure in relation to changes in a range of physical, biological and anthropogenic variables between 2007 and 2018 in Onagawa Bay. Commercially important fish such as greenlings, Japanese anchovy, flatfishes, rockfishes were consistently abundant in both larval and adult fish assemblages. While abundance, species richness, and Shannon index H' for adult fish and epibenthic megafaunal assemblages increased significantly soon after the disaster to peak values towards the end of the study period, the same metrics did not change accordingly for larval fish assemblages. Temporal dynamics of larval fish community clearly demonstrated significant seasonal variation along with changes in large-scale environmental conditions such as temperature and nutrients. However, anthropogenic components such as decline in human population, reduction in fishing pressure and the recovery of aquaculture operations significantly explained the observed post-disaster change in adult fish and epibenthic megafaunal communities. The pelagic and benthic components of Onagawa Bay appeared to have responded to the 2011 disaster very differently, and this study suggests the post-disaster recovery and dynamics of the coastal ecosystems may be regulated by how human societies respond to the impacts of a tsunami catastrophe through their influences on benthic habitat of ecosystems.

Bioaccumulation of persistent organic pollutants in the deepest ocean fauna.

The legacy and reach of anthropogenic influence is most clearly evidenced by its impact on the most remote and inaccessible habitats on Earth. Here we identify extraordinary levels of persistent organic pollutants in the endemic amphipod fauna from two of the deepest ocean trenches (>10,000 metres). Contaminant levels were considerably higher than documented for nearby regions of heavy industrialization, indicating bioaccumulation of anthropogenic contamination and inferring that these pollutants are pervasive across the world's oceans and to full ocean depth.

Temporal variation in environmental conditions and the structure of fish assemblages around an offshore oil platform in the North Sea.

This study reports temporal variations in the environmental conditions and the structure of fish assemblages observed in the vicinity of an offshore oil platform and the surrounding seafloor in the North Sea. Multi-seasonal sampling was conducted at a typical large steel jacketed facility, using mid-water fish traps at three different depths (i.e., 10, 50 & 100 m). Commercially important gadoids such as saithe Pollachius virens, haddock Melanogrammus aeglefinus and cod Gadus morhua were the most abundant species, however, the species composition and the relative abundances of the species varied with depth, season and between years. Comparisons with a large-scale bottom trawl survey data suggested highly dynamic and species-specific interactions between fish movements, changing environmental conditions and the physical presence of an offshore platform. Given the number of platforms currently installed across the North Sea, there is a need to identify biological mechanisms behind such dynamic interactions.

Climate Change, Sea-Level Rise and Implications for Coastal and Estuarine Shoreline Management with Particular Reference to the Ecology of Intertidal Benthic Macrofauna in NW Europe.

In many European estuaries, extensive areas of intertidal habitats consist of bare mudflats and sandflats that harbour a very high abundance and biomass of macrobenthic invertebrates. The high stocks of macrobenthos in turn provide important food sources for the higher trophic levels such as fish and shorebirds. Climate change and associated sea-level rise will have potential to cause changes in coastal and estuarine physical properties in a number of ways and thereby influence the ecology of estuarine dependent organisms. Although the mechanisms involved in biological responses resulting from such environmental changes are complex, the ecological effects are likely to be significant for the estuarine benthic macrofauna and hence the consumers they support. This paper reviews the utilisation patterns of estuarine intertidal habitats by shorebirds, fish and crustaceans, as well as factors affecting the distribution, abundance and biomass of estuarine macrobenthos that is known to be important food source for these estuarine predators. This study also provides simple conceptual models of the likely impacts of sea-level rise on the physical and biological elements of estuarine intertidal habitats, and implications of these results are discussed in the context of sustainable long term flood and coastal management in estuarine environments.

Hadal trenches: the ecology of the deepest places on Earth.

Hadal trenches account for the deepest 45% of the oceanic depth range and host active and diverse biological communities. Advances in our understanding of hadal community structure and function have, until recently, relied on technologies that were unable to document ecological information. Renewed international interest in exploring the deepest marine environment on Earth provides impetus to re-evaluate hadal community ecology. We review the abiotic and biotic characteristics of trenches and offer a contemporary perspective of trench ecology. The application of existing, rather than the generation of novel, ecological theory offers the best prospect of understanding deep ocean ecology.