A new Tedania species (Porifera) was collect using remotely operated vehicles during the Canadian mission HUD2010-029 and the British RRS Discovery Cruise DY081, on the Orphan Seamount near the Orphan Knoll, northwest Atlantic, between 2999.88 and 3450.4 m depth. Orphan Knoll is an isolated, drowned continental fragment 550 km northeast Newfoundland in the Labrador Sea. This region is biologically rich and complex and in 2007, the regional fisheries management organization operating in the area regulated that no vessel shall engage in bottom-contact fishing activities until reviewed in 2020 with a review slated at the end of this year. Members of the genus Tedania are uncommon in the temperate northern hemisphere with only six species known previously: Tedania ( Tedania ) anhelans ; Tedania ( Tedania ) pilarriosae ; Tedania ( Tedania ) suctoria ; Tedania ( Tedania ) urgorrii ; Tedania ( Tedaniopsis ) gurjanovae ; and Tedania ( Tedaniopsis ) phacellina . The particular features of the new sponge we describe are the very peculiar external morphology which is tree-like with dichotomous branching—a morphology not previously described in this subgenus; and the combination of spicules found: long styles, the typical tornotes of the subgenus and two sizes of onychaetes. Additional information is provided on other species of Tedaniopsis described from the Atlantic Ocean. Based on the characteristics reported, we propose a new species, Tedania ( Tedaniopsis ) rappi sp. nov. in honor of Prof. Hans Tore Rapp (1972–2020), University of Bergen, Norway, a renowned sponge taxonomist and coordinator of the Horizon 2020 SponGES project. The holotype of T. ( T. ) phacellina Topsent, 1912 from the Azores, the only other northern Atlantic species in the subgenus Tedaniopsis , was reviewed for comparison.

Understanding the distribution and density of sponge grounds in the deep sea is key to appreciating the ecological importance, vulnerability, and role in ocean biogeochemistry of these important habitats. A novel combination of clustering analysis and fluid flow finite element modeling was used to study the distribution of four sponge grounds from the Labrador Sea, which were chosen for their distinct assemblages of sponges. Significant small-scale clustering patterns of sponges were found within each sponge ground, measured using the Ripley K function. A new approach using finite element modeling of fluid flow was then applied to understand the drivers of the observed sponge distribution, with detailed numerical experiments providing insights into the flow patterns that could not be obtained from field measurements. Simulations using idealized sponge shapes suggested that sponge wakes could interact and influence the mean flow conditions at the spacings observed within the sponge grounds. Simulations of flow over topographic models of the sponge grounds showed that these interacting wakes generated a boundary layer of slowed flow, which may be beneficial to sponge development. The boundary layer may be acting as a protective layer, affecting larval recruitment, increasing particle fall out, and increasing the effective radius of pumping. This observation has important implications for the impact of anthropogenic damage on sponge grounds, which changes the sponge distribution and may reduce the boundary layer thickness, affecting potential recovery rates. This study illustrates the power of incorporating mathematical modeling with field observations in the deep sea to increase our understanding of anthropogenic and climate change impacts on sponge ground ecosystem structure and function.

Reconstruction of silica cycling in the oceans is key to a thorough understanding of past climates because of the inherent links between the biogeochemistry of silicifiers and sequestration of organic carbon. Diatoms are one of the most important phytoplankton groups in determining export production from surface waters, and rely largely on upwelling deeper waters as a source of dissolved silicon, an essential nutrient for their growth. Quantification of changes in deep water dissolved silicon concentrations in the past allows a more robust understanding of changes in surface nutrient supply and whole-ocean silicon cycling, but cannot be achieved using surface-derived geochemical archives. In the last few years, there has been increasing focus on the use of geochemical archives in siliceous skeletal elements, or spicules, from seafloor-dwelling sponges to fill this gap. The stable silicon isotopic composition of spicules has been shown to be a function of ambient dissolved silicon, providing a potential archive for past changes in bottom water nutrients. However, biomineralisation processes impact silicon isotope fractionation and silica formed by atypical processes (derived from carnivorous sponges, hypersilicified spicules, and giant basal spicules) result in anomalous geochemical signatures. Furthermore, there is considerable scatter in the calibration between spicule silicon isotopes and dissolved silicon in seawater, even when the atypical groups have been removed. Here, we explore this variability further, by examining aggregation and assemblage-level differences in isotopic fractionation, using silicon isotopic measurements of specimens from two monospecific sponge groups (Pheronema carpenteri and Vazella pourtalesi), and one mixed-species population (genus Geodia) from the North Atlantic. Our new data reveal that variability within the monospecific aggregations is less than mixed-species assemblage, pointing towards a genetic control in isotopic fractionation. However, there is still variability within the monospecific aggregations, which cannot be explained by macroscale environmental differences: such variability is likely a reflection of the physiological health of the individuals, or highly localised heterogeneities in sponge habitats. Other challenges remain in the interpretation of spicule silicon isotopes as proxies for dissolved silicon changes through time, especially when investigating periods of Earth history that extend back considerably further than the residence time of dissolved silicon in the oceans. Despite all the questions still surrounding the use of sponge silicon isotopes in palaeoceanographic applications, they are still the only known archive of bottom water dissolved silicon. Continued efforts to understanding sponge biomineralisation and to incorporate silicon isotopes into oceanic models will help to improve further the reliability of the archive. (C) 2019 Elsevier Ltd. All rights reserved.