Field deployments of a self-contained subsea platform for acoustic monitoring of the environment around marine renewable energy structurea

The drive towards sustainable energy has seen rapid development of marine renewable energy devices, and current efforts are focusing on wave and tidal stream energy. The NERC/DEFRA collaboration FLOWBEC-4D (Flow, Water column & Benthic Ecology 4D) is addressing the lack of knowledge of the environmental and ecological effects of installing and operating large arrays of wave and tidal energy devices. The FLOWBEC sonar platform combines a number of instruments to record information at a range of physical and multi-trophic levels. Data are recorded at a resolution of several measurements per second, for durations of 2 weeks to capture an entire spring-neap tidal cycle. An upward-facing multifrequency Simrad EK60 echosounder (38, 120 and 200 kHz) is synchronized with an upward-facing Imagenex 837B Delta T multibeam sonar (120° × 20° beamwidth, 260 kHz) aligned with the tidal flow. An ADV is used for local current measurements and a fluorometer is used to measure chlorophyll (as a proxy for plankton) and turbidity. The platform is self-contained with no cables or anchors, facilitating rapid deployment and recovery in high-energy sites and flexibility in allowing baseline data to be gathered. Five 2-week deployments were completed in 2012 and 2013 at wave and tidal energy sites, both in the presence and absence of renewable energy structures. These surveys were conducted at the European Marine Energy Centre, Orkney, UK. Algorithms for noise removal, target detection and target tracking have been written using a combination of LabVIEW, MATLAB and Echoview. Target morphology, behavior and frequency response are used to aid target classification, with concurrent shore-based seabird observations used to ground truth the acoustic data. Using this information, the depth preference and interactions of birds, fish schools and marine mammals with renewable energy structures can be tracked. Seabird and mammal dive profiles, predator-prey interactions a- d the effect of hydrodynamic processes during foraging events throughout the water column can also be analyzed. These datasets offer insights into how fish, seabirds and marine mammals successfully forage within dynamic marine habitats and also whether individuals face collision risks with tidal stream turbines. Measurements from the subsea platform are complemented by 3D hydrodynamic model data and concurrent shore-based marine X-band radar. This range of concurrent fine-scale information across physical and trophic levels will improve our understanding of how the fine-scale physical influence of currents, waves and turbulence at tidal and wave energy sites affect the behavior of marine wildlife, and how tidal and wave energy devices might alter the behavior of such wildlife. Together, the results from these deployments increase our environmental understanding of the physical and ecological effects of installing and operating marine renewable energy devices. These results can be used to guide marine spatial planning, device design, licensing and operation, as individual devices are scaled up to arrays and new sites are considered. The combination of our current technology and analytical approach can help to de-risk the licensing process by providing a higher level of certainty about the behavior of a range of mobile marine species in high energy environments. It is likely that this approach will lead to greater mechanistic understanding of how and why mobile predators use these high energy areas for foraging. If a fuller understanding and quantification can be achieved at single demonstration scales, and these are found to be similar, then the predictive power of the outcomes might lead to a wider strategic approach to monitoring and possibly lead to a reduction in the level of monitoring required at each commercial site

Distribution maps of cetacean and seabird populations in the North‐East Atlantic

1. Distribution maps of cetaceans and seabirds at basin and monthly scales are needed for conservation and marine management. These are usually created from standardized and systematic aerial and vessel surveys, with recorded animal den- sities interpolated across study areas. However, distribution maps at basin and monthly scales have previously not been possible because individual surveys have restricted spatial and temporal coverage. 2. This study develops an alternative approach consisting of: (a) collating diverse survey data to maximize spatial and temporal coverage, (b) using detection func- tions to estimate variation in the surface area covered (km2) among these surveys, standardizing measurements of effort and animal densities, and (c) developing species distribution models (SDM) that overcome issues with heterogeneous and uneven coverage. 3. 2.68 million km of survey data in the North-East Atlantic between 1980 and 2018 were collated and standardized. SDM using Generalized Linear Models and General Estimating Equations in a hurdle approach were developed. Distribution maps were then created for 12 cetacean and 12 seabird species at 10 km and monthly resolution. Qualitative and quantitative assessment indicated good model performance. 4. Synthesis and applications. This study provides the largest ever collation and standardization of diverse survey data for cetaceans and seabirds, and the most comprehensive distribution maps of these taxa in the North-East Atlantic. These distribution maps have numerous applications including the identification of im- portant areas needing protection, and the quantification of overlap between vul- nerable species and anthropogenic activities. This study demonstrates how the analysis of existing and diverse survey data can meet conservation and marine management needs.Versión del editor4,7

An evaluation of the use of shore-based surveys for estimating spatial overlap between deep-diving seabirds and tidal stream turbines

As we approach the first array deployments of tidal stream turbines, the risk of collisions between moving components of devices and deep-diving seabirds need assessing at population levels. Part of assessing risks is quantifying the extent to which the foraging distributions of deep-diving seabirds overlap with the potential locations of devices in the large tidal pass habitats favoured for array installations (spatial overlap). Shore-based surveys using single vantage points and extensive grid systems to record the locations of foraging birds are often used in large tidal passes. Here, an application of these methods in the Fall of Warness (FOW), Orkney, UK are used to evaluate their effectiveness for quantifying and statistically analysing spatial overlap in large tidal passes. Whilst it was possible to quantify and statistically analyse spatial overlap using the methods evaluated here, viable statistical analysis required data sacrifices through the use of presence rather than abundance data. Moreover, comparisons between simultaneous shore-based and boat-based surveys, which are assumed to represent an accurate method, showed that sightings in the former were biased towards non-turbine microhabitats. This shore-based survey bias reflected low detection rates of foraging birds in fast unidirectional currents away from coastlines. Therefore, the methods evaluated here are unsuitable for quantifying and statistically analysing spatial overlap in large tidal passes. It is suggested that future shore-based surveys should overcome aforementioned issues by using several vantage points spread throughout large tidal passes, and comparing species use of neighbouring turbine and non-turbine microhabitats at reasonable distances to the vantage points (<2 km) during favourable sea states (Beaufort Scale < 3). It is hoped that these recommendations lead to the development of standardised shore-based survey methods, providing comparable measurements of spatial overlap across tidal passes earmarked for array deployments: a key step towards estimations of collision risks at population levels

The effect of environmental factors on shell growth and repair in Buccinum undatum

The processes and factors which affect shell growth and repair in molluscs are poorly understood. In this study, the capabilities of shell growth and repair in the marine gastropod Buccinum undatum were investigated experimentally by implementing laboratory-controlled mechanical damage to the shell margin/lip. Three key factors, life stage (juvenile or adult), seawater temperature (5–15 °C) and food availability (unfed, weekly, or daily feeding), were investigated in a series of controlled laboratory experiments to establish their roles in the processes of shell growth and repair. Significant differences in rates of shell growth and repair between food and temperature regimes were observed, with the greatest difference occurring with different life stages. Rates of shell growth in non-damaged whelks were slightly faster but not significantly different from damaged individuals in any of the experiments. Tank-reared juveniles maintained in the highest seawater temperature regime (15 °C) displayed significantly faster rates of shell repair (F = 6.47, p < 0.05) than conspecifics held at lower seawater temperatures. Through characterising both biological and environmental factors affecting shell growth and repair, it is demonstrated that there are multiple aspects influencing shell growth and shell repair. It is important to be able to understand and establish differences in rates of growth to better manage this commercial species

Testing for sub-colony variation in seabird foraging behaviour: ecological and methodological consequences for understanding colonial living

Intraspecific interactions have important roles in shaping foraging behaviours. For colonial species such as seabirds, intense competition for prey around colonies may drive differences in foraging behaviour between age-classes and sexes or lead to individual specialisation. While much research has focussed on understanding these differences in foraging behaviour, few studies have investigated the possibility of sub-colony foraging asymmetries within colonies. Such knowledge could improve our understanding of the ecological processes associated with colonial living. It may also have important methodological implications in studies where the foraging behaviours recorded from individuals in a small number of sub-colonies are assumed to be representative of those from the colony as a whole. Here, we use GPS loggers and stable isotope analysis of red blood cells to test for differences in foraging behaviour among 7 sub-colonies of a large northern gannet Morus bassanus colony over 3 yr. We found no instances of statistically significant differences in foraging behaviour among sub-colonies. Although complimentary in situ observations found similarities among neighbours’ departure directions, these results may be attributable to wind vectors. We therefore conclude that sub-colony foraging asymmetries are either limited or absent in northern gannets. However, given the current lack of knowledge across seabird species, we urge similar studies elsewhere

Sex-specific foraging behaviour in northern gannets Morus bassanus: incidence and implications

Sexual segregation in foraging and migratory behaviour is widespread among sexually dimorphic marine vertebrates. It has also been described for a number of monomorphic species, yet the underlying mechanisms are poorly understood. We examined variation among years, seasons and age-classes in sex-specific foraging and over-wintering behaviour in the northern gannet Morus bassanus, a species with slight sexual dimorphism. Our results revealed consistent sexual differences in the stable isotope ratios of breeding birds: over 3 different breeding periods, adult females consistently consumed prey with significantly lower δ13C and δ15N values than adult males. Additionally, GPS tracking data showed that breeding females foraged further offshore than breeding males (a result consistent with the δ13C data), and the home ranges of the 2 sexes were distinct. Analyses of stable isotope ratios using a Bayesian mixing model (SIAR) revealed that breeding males consumed a higher proportion of fishery discards than females. Analysis of stable isotope ratios in red blood cells of immature gannets (aged 2 to 4) indicated that sexual segregation was not present in this age-class. Although sample sizes were small and statistical power correspondingly low, analysis of geolocator data and of stable isotope ratios in winter-grown flight feathers revealed no clear evidence of sexual segregation during the non-breeding period. Together these results provide detailed insight into sex-specific behaviour in gannets throughout the annual cycle, and although the mechanisms remain unclear they are unlikely to be explained by slight differences in size