Implementation of the OBSEA coastal seafloor observatory to derive ecological indicators

Abstract

Reliable biodiversity and ecosystem functioning assessment can be achieved through the development and implementation of new cabled seafloor observatories. Those multiparametric video-platforms have the capability to achieve continuous, high-frequency and long-lasting monitoring of marine ecosystems (Aguzzi et al., 2019; Danovaro et al., 2017). In this framework, the OBSEA (www.obsea.es) was deployed at 20 m depth in 2009, 4 km off of Vilanova i la Gertrú (Barcelona). Since 2009, a 30 min time-lapse image acquisition focused on the bony fish community composed by 25 species and 2 genres (Aguzzi et al., 2015), as highly motile species considered good indicators for climatechange (Duvly et al., 2008). This has been accompanied by environmental data collection (Aguzzi et al. 2011). The described assetis now being upgraded with the implementation of an additional satellite tripod camera and an Internet Operated Vehicle (IOV), a crawler, to increase the video spatial coverage. The existing imaging and environmental data set, reaching a length of nearly a decade, will be now complemented by the new spatially-extended one, in order to test the ecological representation power of still and mobile cameras and to derive ecological indicators (i.e. density of populations, richness and relative abundance as evenness) at diel, monthly, seasonal and inter-annual scales. Moreover, inferences of potential cause-and-effects principles between environmental variables and species responses (i.e. expressed as fluctuations in counts) will be evaluated to identify putative drivers controlling their behaviour. To date we are observing marked diel counts fluctuations for all fish species. This tendency is maintained throughout the seasons with the amplitude of the total fish counts curve following the variation in the photophase length amplitude, described through the sun irradiance