Abstract
Emerald Basin on the Scotian Shelf off Nova Scotia, Canada, is home to a globally unique aggregation of the glass sponge Vazella pourtalesi, first documented in the region in 1889. In 2009, Fisheries and Oceans Canada (DFO) implemented two Sponge Conservation Areas to protect these sponge grounds from bottom fishing activities. Together, the two conservation areas encompass 259 km2. In order to ascertain the degree to which the sponge grounds remain unprotected, we modelled the presence probability and predicted range distribution of V. pourtalesi on the Scotian Shelf using random forest modelling on presence-absence records. With a high degree of accuracy the random forest model predicted the highest probability of occurrence of V. pourtalesi in the inner basins on the central Scotian Shelf, with lower probabilities at the shelf break and in the Fundian and Northeast Channels. Bottom temperature was the most important determinant of its distribution in the model. Although the two DFO Sponge Conservation Areas protect some of the more significant concentrations of V. pourtalesi, much of its predicted distribution remains unprotected (over 99%). Examination of the hydrographic conditions in Emerald Basin revealed that the V. pourtalesi sponge grounds are associated with a warmer and more saline water mass compared to the surrounding shelf. Reconstruction of historical bottom temperature and salinity in Emerald Basin revealed strong multi-decadal variability, with average bottom temperatures varying by 8°C. We show that this species has persisted in the face of this climatic variability, possibly indicating how it will respond to future climate change.
Highlights
Deep-sea sponge-dominated communities have gained increasing attention in recent years from both an ecological and conservation perspective
V. pourtalesi was found in lower concentrations along the saddle between Emerald and LaHave Banks in the Scotian Gulf, and in the Northeast and Fundian Channels leading to the Gulf of Maine
While some records are associated with high-slope areas (11 ̊ in the Northeast Channel), the densest sponge grounds occurred in areas of low topographic relief (0.04 to 3.20 ̊ in Emerald Basin)
Summary
Deep-sea sponge-dominated communities have gained increasing attention in recent years from both an ecological and conservation perspective. Growing evidence suggests that these habitats are widely distributed across the deep sea globally [1,2], but that they . Predicted distribution of glass sponge Vazella pourtalesi the Russian Hat Sponge Vazella pourtalesi” led by L.I.B. and the H2020 EU Framework Programme for Research and Innovation Project SponGES (Deep-sea Sponge Grounds Ecosystems of the North Atlantic: an integrated approach towards their preservation and sustainable exploitation) The funders supported the collection of data used in this manuscript. Oceans North provided support in the form of salaries for S.D. Fuller, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of all authors are articulated in the ‘author contributions’ section
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