An experimental comparison of three towed underwater video systems using species metrics, benthic impact and performance

Managing ecological systems, which operate over large spatial scales, is inherently difficult and often requires sourcing data from different countries and organizations. The assumption might be made that data collected using similar methodologies are comparable, but this is rarely tested. Here, benthic video data recorded using different towed underwater video systems (TUVSs) were experimentally compared. Three technically different TUVSs were compared on different seabed types (rocky, mixed ground and sandy) in Kingmere Marine Conservation Zone, off the south coast of England. For each TUVS, species metrics (forward facing camera), seabed impact (backward facing camera) and operational performance (strengths and limitations of equipment and video footage) were compared with the aim of providing recommendations on their future use and comparability of data between different systems. Statistically significant differences between species richness, density, cover and assemblage composition were detected amongst devices and were believed to be mostly due to their optical specifications. As a result of their high image definition and large field of vision both the benthic contacting heavy and benthic tending TUVS provided good quality footage and ecological measurements. However, the heaviest TUVS proved difficult to operate on irregular ground and was found to cause the most impact to the seabed. The lightest TUVS (benthic contacting light) struggled to maintain contact with the seabed. The benthic tending TUVS was able to fly over variable seabed relief and was comparably the least destructive. Results from this study highlight that particular care should be given to sled and optic specifications when developing a medium- or long-term marine protected area monitoring programme. Furthermore, when using data gathered from multiple sources to test ecological questions, different equipment specifications may confound observed ecological differences. A benthic tending TUVS is recommended for benthic surveys over variable habitat types, particularly in sensitive areas, such as marine protected areas

First round of MaRINET 2 Tidal Energy Round Robin Tests : combined wave and current tests

This second Round Robin Test program aims to establish the influence of the combined wave and current effect on the power capture and performance of a generic tidal turbine prototype. In this paper, we present the results obtained in the first two selected facilities: the IFREMER wave and current circulating tank and the CNR-INM wave towing tank. These facilities were selected on the basis that their dimensions along with the rotor diameter of the turbine translate into low blockage ratio conditions and that both facilities can provide the same range of experimental conditions. The experimental campaigns uses the same setup, except from additional equipment to measure flow characteristics. The performance of the turbine is comparable between the tanks, but because some intrinsic differences in creating wave and current, it may be slightly different for the corresponding conditions. The blockage effect and, in some cases, the velocity disc-integrated averaging need to be accounted for a better agreement. The slight remaining differences observed on the power coefficient curves may be related to turbulence and wave-current interactions. A deeper analysis is required to process the other parameters in order to better understand this phenomena

Data from: An experimental comparison of three Towed Underwater Video Systems using species metrics, benthic impact and performance

1. Managing ecological systems, which operate over large spatial scales is inherently difficult and often requires sourcing data from different countries and organizations. The assumption might be made that data collected using similar methodologies are comparable but this is rarely tested. Here, benthic video data recorded using different towed underwater video systems (TUVSs) were experimentally compared. 2. Three technically different TUVSs were compared on different seabed types (rocky, mixed ground and sandy) in Kingmere Marine Conservation Zone, off the south coast of England. For each TUVS, species metrics (forward facing camera), seabed impact (backward facing camera).and operational performance (strengths and limitations of equipment and video footage) were compared with the aim of providing recommendations on their future use and comparability of data between different systems. 3. Statistically significant differences between species richness, density, cover and assemblage composition were detected amongst devices and were believed to be mostly due to their optical specifications. As a result of their high image definition and large field of vision both the Benthic Contacting Heavy and benthic tending TUVS provided good quality footage and ecological measurements. However the heaviest TUVS proved difficult to operate on irregular ground and was found to cause the most impact to the seabed. The lightest TUVS (Benthic Contacting Light) struggled to maintain contact with the seabed. The benthic tending TUVS was able to fly over variable seabed relief and was comparably the least destructive. 4. Results from this study highlight that particular care should be given to sled and optic specifications when developing a medium or long term MPA monitoring programme. Furthermore, when using data gathered from multiple sources to test ecological questions, different equipment specifications may confound observed ecological differences. 5. A benthic tending TUVS is recommended for benthic surveys over variable habitat types, particularly in sensitive areas such as marine protected areas

Impact, Taxa, Cover, Count and Assemblage data

Impact, Taxa, Cover and count data show metrics as described in the paper. The assemblage data is averaged over frame grabs per site as described in the paper. Details of Towed Underwater Video System, Habitat, Area and Site are included. Metrics are labelled on separate tabs in the same file