High‐resolution seabed imagery as a tool for biodiversity conservation planning on continental margins

Abstract

Submarine canyons increase seascape diversity on continental margins and harbour diverse and abundant biota vulnerable to fishing. Because many canyons are fished, there is an increasing emphasis on including them in conservation areas on continental margins. Here we report on sponge diversity and bottom cover in three canyons of South‐eastern Australia, test the performance of biological and abiotic surrogates, and evaluate how biological data from detailed seabed surveys can be used in conservation planning in these habitats. The biological data on sponge assemblage structure and species richness were obtained from 576 seafloor images taken between 148 and 472 m depth, yielding 65 morphospecies. Seafloor characteristics were similar within and between canyons, being almost exclusively composed of sediments with very few rocky substrates of higher relief. This environmental homogeneity did not, however, translate into biological uniformity of the megabenthos, and environmental factors were consequently poor predictors of biological features. By contrast, total bottom cover of sponges was highly correlated with species richness and served as a good proxy for species‐level data in this situation. Design strategies that employ information on cover or richness of sponges provided a large dividend in conservation effort by dramatically reducing the number of spatial units required to achieve a specified conservation target of 50–90% of species to be included in reserves. This demonstrates that image‐derived data are useful for the design of reserves in the deep sea, particularly where extractive sampling is not warranted. Using biological data on the sponge megabenthos to identify conservation units can also minimise socio‐economic costs to fisheries because of a smaller geographic and bathymetric ambit of conservation areas.

Megafaunal distribution and biodiversity in a heterogeneous landscape: the iceberg-scoured Rockall Bank, NE Atlantic

“…The use of morphospecies is somewhat problematic, as cryptic species will be considered under a single grouping while other groups showing greater morphological variation (e.g. sponges) may be split into more groups, but their use is common in marine studies where imagery is used as the main sampling tool (Soltwedel et al 2009, Schlacher et al 2010, Compton et al 2013. Although the use of higher taxonomic levels is another option to estimate biodiversity (Roy et al 1996), these tend to be more useful when investigating broader scale patterns -and in the case of our dataset, even family-level identification of sponges is problematic without specimen collection.…”

Topographic complexity and landscape ­temperature patterns create a dynamic habitat structure on a rocky intertidal shore

“…Banks & Skilleter 2007, McArthur et al 2010, Schlacher et al 2010. The basic tenet of this approach is that the measures of habitat structure used are accurate and biologically relevant.…”

Changes in deep reef benthic community composition across a latitudinal and environmental gradient in temperate Eastern Australia

“…On deep mesophotic (depth > 30 m) temperate reefs, sessile invertebrates, including sponges, cnidarians, ascidians and bryozoans, dominate and contribute to the diversity, structure and functioning of benthic ecosystems (Fromont et al 2006, Bell 2007, Schlacher et al 2010, Schönberg & Fromont 2012. Larger sessile invertebrates, in particular sponges, gorgonians and octocorals, provide essential structural and functional ecosystem services, including nutrient provisioning and recycling (de Goeij et al 2013) (i.e.…”

“…Larger sessile invertebrates, in particular sponges, gorgonians and octocorals, provide essential structural and functional ecosystem services, including nutrient provisioning and recycling (de Goeij et al 2013) (i.e. benthic−pelagic coupling), as well as provision of complex habitat and refuge for other organisms (Fromont et al 2006, Bell 2007, Schlacher et al 2010, Schönberg & Fromont 2012.…”