Habitat suitability mapping of the black coral Leiopathes glaberrima to support conservation of vulnerable marine ecosystems

The black coral Leiopathes glaberrima is an important habitat forming species that supports benthic biodiversity. Due to its high sensitivity to fishing activities, it has been classified as indicator of Vulnerable Marine Ecosystems (VMEs). However, the information on its habitat selection and large-scale spatial distribution in the Mediterranean Sea is poor. In this study a thorough literature review on the occurrence of L. glaberrima across the Mediterranean Sea was undertaken. Predictive modelling was carried out to produce the first continuous map of L. glaberrima suitable habitat in the central sector of the Mediterranean Sea. MaxEnt modeling was used to predict L. glaberrima probability of presence as a function of seven environmental predictors (bathymetry, slope, aspect North–South and East–West, kinetic energy due to currents at the seabed, seabed habitat types and sea bottom temperature). Our results show that bathymetry, slope and aspect are the most important factors driving L. glaberrima spatial distribution, while in less extent the other environmental variables. This study adds relevant information on the spatial distribution of vulnerable deep water corals in relation to the environmental factors in the Mediterranean Sea. It provides an important background for marine spatial planning especially for prioritizing areas for the conservation of VMEs.

Population genomic structure of the black coral Antipathella subpinnata in Mediterranean Vulnerable Marine Ecosystems

Antipathella subpinnata(Ellis and Solander 1786) is one of the most frequently observed black corals at mesophotic depths (60–200 m) of the Mediterranean Sea, particularly in the northwestern part of the basin, where its populations can reach high densities and create forest-like aggregations, both along the coast and in offshore locations such as seamounts. Similar to other marine underwater forests, black coral gardens host a rich associated fauna and attract numerous species of commercial interest. As such, these corals are targeted by recreational and artisanal fisheries and are vulnerable to human impact due to their arborescent morphology and low growth rates. Genetic connectivity can provide valuable insight into the processes of population maintenance and replenishment following environmental disturbance and is often used as a proxy for population resilience. In our study, a restriction-site associated DNA analysis (2bRAD) was used to evaluate fine-scale population structure of the Mediterranean black coralA. subpinnata, and to understand which populations could serve as a potential source of genetic diversity for adjacent populations. Colonies from two offshore localities (a Ligurian seamount and a Tyrrhenian canyon) and four coastal populations from Liguria and Sicily were sampled and genotyped. Significant genetic differentiation was recorded between coastal and offshore localities. Moreover, offshore localities were genetically distinct from one another, while all coastal populations were characterized by panmixia. This indicates that offshoreA. subpinnatagardens are potentially less resilient to human impact (i.e., demersal fishing activities) due to a limited influx of larvae from adjacent habitats. In addition, they are unlikely to supply coral propagules to coastal populations. Overall, this study highlights the vulnerability of MediterraneanA. subpinnataforests, and the importance of enforcing conservation and management measures to achieve Good Environmental Status (GES, EU Marine Strategy Framework Directive) of these valuable marine ecosystems.

Southwest Pacific Paleoceanography During the Late Holocene: 3000 years of ocean circulation and marine biogeochemistry reconstructed from New Zealand deep-sea black corals

<p>The global climate results from interactions between the ocean and atmosphere. Ocean gyres are perhaps one of the most significant interactions; they regulate temperature, salinity and nutrient flow across the ocean basins. Gyres transport warm, tropical waters to higher latitudes and cold waters to lower latitudes and act as the dominant heat-transport mechanism in the Earth’s climate system. They also influence spatial patterns in marine primary production by distributing nutrients between the equator and poles. However, gyre circulation in the subtropics has been strengthening, leading to marine heat waves, changing biogeochemistry and reducing primary production since the early 1900s. These changes are often interpreted as a consequence of anthropogenic climate change. However, ocean circulation and primary production can exhibit natural variations on a variety of timescales. Could these recent changes be a part of a long-term natural cycle or a product of anthropogenic change? </p> <b>This research aims to reconstruct South Pacific Gyre (SPG) circulation and biogeochemistry using a suite of New Zealand black corals. The primary research goal is determining if there is a precedent for the ocean changes observed over the instrumental period. Black corals are an ideal paleoceanographic archive for this work; they provide high-resolution, multi-millennial records of biogeochemistry and ocean circulation within their skeletons, derived using radiocarbon (14C) and stable isotopes (d13C and d15N). In this thesis, I show that late Holocene SPG strength has been highly variable and the relationship between circulation and biogeochemistry is timescale dependent. </b><p>The black coral radiocarbon records suggest late Holocene SPG circulation has been controlled by westerly wind strength. Our records show the SPG exhibits natural variability on multi-centennial and millennial timescales that corresponds to the variability within the Southern Annular Mode (SAM) and the El Niño-Southern Oscillation (ENSO). The black coral circulation record shows that the modern gyre circulation is not without precedent over the last 3000 years. </p> <p>The black coral d13C and d15N records show significant variability on multi-decadal to multi-centennial timescales. Multi-centennial variability in black coral d13C and d15N appears to be driven by sea surface temperature (SST), nitrogen fixation rates and wind-driven upwelling and is possibly forced by the mean state of the Southern Oscillation Index and ocean circulation strength. A trend in black coral d13C over the last 1500 years also suggests a shift in phytoplankton community structure towards larger and faster growing phytoplankton. These records also reveal a shift in mean coral d13C and d15N between the 0-2000BP and 2000-3000BP period, the latter corresponding to a period of stronger gyre circulation inferred from the radiocarbon records. </p> <p>This work shows that: 1) New Zealand’s black corals are a promising archive for studying paleoceanography; they can extend instrumental ocean records and fill the gap between traditional southwest Pacific paleoceanographic proxy records (tropical corals, sediment cores); 2) SPG circulation has been highly variable over the last 3000 years; circulation is controlled by atmospheric patterns (e.g. SAM) on multi-centennial to millennial timescales; 3) Gyre circulation is only one of many forcing factors on southwest Pacific primary production and marine biogeochemistry; comparisons between the ∆R, d13C and d15N proxies show that variations in SPG biogeochemical patterns and productivity are likely driven by local dynamics such as phytoplankton community structure, SST, upwelling and gyre circulation. Finally, this research demonstrates the key role that a distributed set of deep-sea coral paleoceanographic reconstructions could play in characterizing the dynamical variability in southwest Pacific Ocean circulation, biogeochemistry and primary production. This information is critical for detecting and attributing past and future anthropogenic impacts on the southwest Pacific Ocean. </p>

Southwest Pacific Paleoceanography During the Late Holocene: 3000 years of ocean circulation and marine biogeochemistry reconstructed from New Zealand deep-sea black corals

<p>The global climate results from interactions between the ocean and atmosphere. Ocean gyres are perhaps one of the most significant interactions; they regulate temperature, salinity and nutrient flow across the ocean basins. Gyres transport warm, tropical waters to higher latitudes and cold waters to lower latitudes and act as the dominant heat-transport mechanism in the Earth’s climate system. They also influence spatial patterns in marine primary production by distributing nutrients between the equator and poles. However, gyre circulation in the subtropics has been strengthening, leading to marine heat waves, changing biogeochemistry and reducing primary production since the early 1900s. These changes are often interpreted as a consequence of anthropogenic climate change. However, ocean circulation and primary production can exhibit natural variations on a variety of timescales. Could these recent changes be a part of a long-term natural cycle or a product of anthropogenic change? </p> <b>This research aims to reconstruct South Pacific Gyre (SPG) circulation and biogeochemistry using a suite of New Zealand black corals. The primary research goal is determining if there is a precedent for the ocean changes observed over the instrumental period. Black corals are an ideal paleoceanographic archive for this work; they provide high-resolution, multi-millennial records of biogeochemistry and ocean circulation within their skeletons, derived using radiocarbon (14C) and stable isotopes (d13C and d15N). In this thesis, I show that late Holocene SPG strength has been highly variable and the relationship between circulation and biogeochemistry is timescale dependent. </b><p>The black coral radiocarbon records suggest late Holocene SPG circulation has been controlled by westerly wind strength. Our records show the SPG exhibits natural variability on multi-centennial and millennial timescales that corresponds to the variability within the Southern Annular Mode (SAM) and the El Niño-Southern Oscillation (ENSO). The black coral circulation record shows that the modern gyre circulation is not without precedent over the last 3000 years. </p> <p>The black coral d13C and d15N records show significant variability on multi-decadal to multi-centennial timescales. Multi-centennial variability in black coral d13C and d15N appears to be driven by sea surface temperature (SST), nitrogen fixation rates and wind-driven upwelling and is possibly forced by the mean state of the Southern Oscillation Index and ocean circulation strength. A trend in black coral d13C over the last 1500 years also suggests a shift in phytoplankton community structure towards larger and faster growing phytoplankton. These records also reveal a shift in mean coral d13C and d15N between the 0-2000BP and 2000-3000BP period, the latter corresponding to a period of stronger gyre circulation inferred from the radiocarbon records. </p> <p>This work shows that: 1) New Zealand’s black corals are a promising archive for studying paleoceanography; they can extend instrumental ocean records and fill the gap between traditional southwest Pacific paleoceanographic proxy records (tropical corals, sediment cores); 2) SPG circulation has been highly variable over the last 3000 years; circulation is controlled by atmospheric patterns (e.g. SAM) on multi-centennial to millennial timescales; 3) Gyre circulation is only one of many forcing factors on southwest Pacific primary production and marine biogeochemistry; comparisons between the ∆R, d13C and d15N proxies show that variations in SPG biogeochemical patterns and productivity are likely driven by local dynamics such as phytoplankton community structure, SST, upwelling and gyre circulation. Finally, this research demonstrates the key role that a distributed set of deep-sea coral paleoceanographic reconstructions could play in characterizing the dynamical variability in southwest Pacific Ocean circulation, biogeochemistry and primary production. This information is critical for detecting and attributing past and future anthropogenic impacts on the southwest Pacific Ocean. </p>

Southwest Pacific Paleoceanography During the Late Holocene: 3000 years of ocean circulation and marine biogeochemistry reconstructed from New Zealand deep-sea black corals

<p>The global climate results from interactions between the ocean and atmosphere. Ocean gyres are perhaps one of the most significant interactions; they regulate temperature, salinity and nutrient flow across the ocean basins. Gyres transport warm, tropical waters to higher latitudes and cold waters to lower latitudes and act as the dominant heat-transport mechanism in the Earth’s climate system. They also influence spatial patterns in marine primary production by distributing nutrients between the equator and poles. However, gyre circulation in the subtropics has been strengthening, leading to marine heat waves, changing biogeochemistry and reducing primary production since the early 1900s. These changes are often interpreted as a consequence of anthropogenic climate change. However, ocean circulation and primary production can exhibit natural variations on a variety of timescales. Could these recent changes be a part of a long-term natural cycle or a product of anthropogenic change? </p> <b>This research aims to reconstruct South Pacific Gyre (SPG) circulation and biogeochemistry using a suite of New Zealand black corals. The primary research goal is determining if there is a precedent for the ocean changes observed over the instrumental period. Black corals are an ideal paleoceanographic archive for this work; they provide high-resolution, multi-millennial records of biogeochemistry and ocean circulation within their skeletons, derived using radiocarbon (14C) and stable isotopes (d13C and d15N). In this thesis, I show that late Holocene SPG strength has been highly variable and the relationship between circulation and biogeochemistry is timescale dependent. </b><p>The black coral radiocarbon records suggest late Holocene SPG circulation has been controlled by westerly wind strength. Our records show the SPG exhibits natural variability on multi-centennial and millennial timescales that corresponds to the variability within the Southern Annular Mode (SAM) and the El Niño-Southern Oscillation (ENSO). The black coral circulation record shows that the modern gyre circulation is not without precedent over the last 3000 years. </p> <p>The black coral d13C and d15N records show significant variability on multi-decadal to multi-centennial timescales. Multi-centennial variability in black coral d13C and d15N appears to be driven by sea surface temperature (SST), nitrogen fixation rates and wind-driven upwelling and is possibly forced by the mean state of the Southern Oscillation Index and ocean circulation strength. A trend in black coral d13C over the last 1500 years also suggests a shift in phytoplankton community structure towards larger and faster growing phytoplankton. These records also reveal a shift in mean coral d13C and d15N between the 0-2000BP and 2000-3000BP period, the latter corresponding to a period of stronger gyre circulation inferred from the radiocarbon records. </p> <p>This work shows that: 1) New Zealand’s black corals are a promising archive for studying paleoceanography; they can extend instrumental ocean records and fill the gap between traditional southwest Pacific paleoceanographic proxy records (tropical corals, sediment cores); 2) SPG circulation has been highly variable over the last 3000 years; circulation is controlled by atmospheric patterns (e.g. SAM) on multi-centennial to millennial timescales; 3) Gyre circulation is only one of many forcing factors on southwest Pacific primary production and marine biogeochemistry; comparisons between the ∆R, d13C and d15N proxies show that variations in SPG biogeochemical patterns and productivity are likely driven by local dynamics such as phytoplankton community structure, SST, upwelling and gyre circulation. Finally, this research demonstrates the key role that a distributed set of deep-sea coral paleoceanographic reconstructions could play in characterizing the dynamical variability in southwest Pacific Ocean circulation, biogeochemistry and primary production. This information is critical for detecting and attributing past and future anthropogenic impacts on the southwest Pacific Ocean. </p>

Unveiling asexual reproductive traits in black corals: polyp bail-out in Antipathella subpinnata

Cnidarians are known to undergo reverse development as a survival mechanism against adverse environmental conditions. Polyp bail-out consists in the polyps’ detachment from the mother colony due to stressful conditions, followed by a complete tissue and cells rearrangement and in some cases in a regression into a simple, ciliated form. Here we describe a massive polyp bail-out event occurred in the mesophotic black coral Antipathella subpinnata in reared conditions. This is the first report of a bail-out event in this species providing new insights into the life cycle and ecology of black corals.