Beschreibung: The Scotian Shelf harbors unique aggregations of the glass sponge Vazella pourtalesii providing an important habitat for benthic and pelagic fauna. Recent studies have shown that these sponge grounds have persisted in the face of strong inter-annual and multi-decadal variability in temperature and salinity. However, little is known of the environmental characteristics on hourly-seasonal time scales. This study presents the first hydrodynamic observations and associated (food) particle supply mechanisms for the Vazella sponge grounds, highlighting the influence of natural variability in environmental conditions on sponge growth and resilience. Near-bottom environmental conditions were characterized by high temporal resolution data collected with a benthic lander, deployed during a period of 10-months in the Sambro Bank Sponge Conservation Area. The lander was equipped with temperature and oxygen sensors, a current meter, a sediment trap and a video camera. In addition, water column profiles of temperature and salinity were recorded along a transect, conducted in a gradient from high to lower sponge presence probability. Over the course of the lander deployment, temperature fluctuated between 8.8-12 °C with an average of 10.6 °C ± 0.4 °C. The water contained on average 6.3 mg l-1 oxygen and near bottom current speed was on average 0.12 m/s, with peaks up to 0.47 m/s. Semi-diurnal tidal flow was observed to result in constant resuspension of particulate matter in the benthic boundary layer. Surface storm events episodically caused extremely turbid conditions on the seafloor that persisted for several days, with particles being resuspended to more than 13 m above the seabed. The carbon flux in the near-bottom sediment trap peaked during storm events and also after a spring bloom in April, when fresh phytodetritus was observed in the bottom boundary layer. While resuspension events can represent a major stressor for sponges, limiting their filtration capability and remobilizing them, episodes of strong currents and lateral particle transport likely play an important role in food supply and the replenishment of nutrients and oxygen. Our results contextualize human-induced threats such as bottom fishing and climate change by providing more knowledge of the natural environmental conditions under which sponge grounds persist.

Beschreibung: The Scotian Shelf harbors unique aggregations of the glass sponge Vazella pourtalesii providing an important habitat for benthic and pelagic fauna. Recent studies have shown that these sponge grounds have persisted in the face of strong inter-annual and multi-decadal variability in temperature and salinity. However, little is known of the environmental characteristics on hourly-seasonal time scales. This study presents the first hydrodynamic observations and associated (food) particle supply mechanisms for the Vazella sponge grounds, highlighting the influence of natural variability in environmental conditions on sponge growth and resilience. Near-bottom environmental conditions were characterized by high temporal resolution data collected with a benthic lander, deployed during a period of 10-months in the Sambro Bank Sponge Conservation Area. The lander was equipped with temperature and oxygen sensors, a current meter, a sediment trap and a video camera. In addition, water column profiles of temperature and salinity were recorded along a transect, conducted in a gradient from high to lower sponge presence probability. Over the course of the lander deployment, temperature fluctuated between 8.8-12 °C with an average of 10.6 °C ± 0.4 °C. The water contained on average 6.3 mg/l oxygen and near bottom current speed was on average 0.12 m/s, with peaks up to 0.47 m/s. Semi-diurnal tidal flow was observed to result in constant resuspension of particulate matter in the benthic boundary layer. Surface storm events episodically caused extremely turbid conditions on the seafloor that persisted for several days, with particles being resuspended to more than 13 m above the seabed. The carbon flux in the near-bottom sediment trap peaked during storm events and also after a spring bloom in April, when fresh phytodetritus was observed in the bottom boundary layer. While resuspension events can represent a major stressor for sponges, limiting their filtration capability and remobilizing them, episodes of strong currents and lateral particle transport likely play an important role in food supply and the replenishment of nutrients and oxygen. Our results contextualize human-induced threats such as bottom fishing and climate change by providing more knowledge of the natural environmental conditions under which sponge grounds persist.

Beschreibung: Deep-sea sponge grounds are underexplored ecosystems that provide numerous goods and services to the functioning of the deep-sea. This study assessed the microbial diversity (by 16S rRNA gene amplicon sequencing) in embryos, juveniles and adults of Craniella zetlandica and Craniella infrequens, common and abundant representatives of deep-sea sponge grounds in the North Atlantic. For this study, in total 39 sponge individuals of the two sponge species were collected and analysed for their associated microbial community composition: C. zetlandica (8 adults, of which one was brooding, and 9 juveniles) and C. infrequens (8 adults, of which four were brooding, and 9 juveniles). We use the term 'juvenile' for small (i.e. mean diameter = 1 cm for C. infrequens; and maximal diameter = 0.3 cm for C. zetlandica), young individuals. For C. zetlandica, juveniles were sampled in September 2018 from an aquarium system (Bergen, Norway). C. zetlandica juveniles were smaller (and most likely younger) than the in situ sampled C. infrequens juveniles and therefore flash-frozen as a whole. Embryos of both sponge species were carefully picked out of the parent sponges with sterile spring steel forceps onboard the research vessel using a stereomicroscope. Ten whole embryos were pooled per adult sponge to account for the small biomass. Data such as presented here provide information on the recruitment of deep-sea sponge holobionts which is needed to develop integrated management tools of such vulnerable marine ecosystems.

Beschreibung: The Scotian Shelf harbors unique aggregations of the glass sponge Vazella pourtalesii providing an important habitat for benthic and pelagic fauna. Recent studies have shown that these sponge grounds have persisted in the face of strong inter-annual and multi-decadal variability in temperature and salinity. However, little is known of the environmental characteristics on hourly-seasonal time scales. This study presents the first hydrodynamic observations and associated (food) particle supply mechanisms for the Vazella sponge grounds, highlighting the influence of natural variability in environmental conditions on sponge growth and resilience. Near-bottom environmental conditions were characterized by high temporal resolution data collected with a benthic lander, deployed during a period of 10-months in the Sambro Bank Sponge Conservation Area. The lander was equipped with temperature and oxygen sensors, a current meter, a sediment trap and a video camera. In addition, water column profiles of temperature and salinity were recorded along a transect, conducted in a gradient from high to lower sponge presence probability. Over the course of the lander deployment, temperature fluctuated between 8.8-12 °C with an average of 10.6 °C ± 0.4 °C. The water contained on average 6.3 mg l-1 oxygen and near bottom current speed was on average 0.12 m/s, with peaks up to 0.47 m/s. Semi-diurnal tidal flow was observed to result in constant resuspension of particulate matter in the benthic boundary layer. Surface storm events episodically caused extremely turbid conditions on the seafloor that persisted for several days, with particles being resuspended to more than 13 m above the seabed. The carbon flux in the near-bottom sediment trap peaked during storm events and also after a spring bloom in April, when fresh phytodetritus was observed in the bottom boundary layer. While resuspension events can represent a major stressor for sponges, limiting their filtration capability and remobilizing them, episodes of strong currents and lateral particle transport likely play an important role in food supply and the replenishment of nutrients and oxygen. Our results contextualize human-induced threats such as bottom fishing and climate change by providing more knowledge of the natural environmental conditions under which sponge grounds persist.

Beschreibung: The collected samples of Geodia species were used to identify if they were reproductive and understand which genes are expressed during gametogenesis. Specifically, specimens fixed in glutaraldehyde solution, were processed for histological analysis to observe gametes in the sponge tissue. Once, we identified male, female (while in gametogenesis) and non-reproductive specimens, we used the RNAlater fixed samples to extract RNA from those specimens. Then, we prepared cDNA libraries, sequenced them with illumina nextseq and we did differential gene expression analysis in order to compare the expressed genes in male vs female specimens and vs non-reproductive specimens. The goal was to understand the molecular machinery of gametogenesis in sponges from an evolutionary point of view.