Indicators are key tools used to assess the ecological status of the environment for ecosystem based management. Anthropogenic disturbances produce changes to habitat condition, which include modifications in species composition and their functions. Monitoring a group of sentinel species (from a taxonomic and functional point of view) provides useful insights into benthic habitat condition. Here, a new indicator, Sentinels of the Seabed (SoS) is proposed to assess state of benthic habitats using "sentinel" species (species which are characteristic of a habitat and sensitive to a given pressure). The selection of these sentinel species has two stages. First, a 'typical species set' is computed using intra-habitat similarity and frequency under reference conditions. Second, the 'sentinel species set' is generated by selecting the most sensitive species from the typical species set. This selection is made using specific indexes able to assess species sensitivity to a particular pressure. The SoS indicator method was tested on six case studies and two different pressure types (trawling disturbance and pollution), using data from otter trawl, box-corer and Remote Operate Vehicle images. In each scenario, the SoS indicator was compared to the Shannon-Wiener diversity index, Margalef index and total biomass, being the only metric, which showed the expected significant negative response to pressure in all cases. Our results shows that SoS was highly effective in assessing benthic habitats status under both physical and chemical pressures, regardless of the sampling gear, the habitat, or the case study, showing a great potential to be a useful tool in the management of marine ecosystems.

Syngnathids are considered as flagship species for marine conservation. Seahorses and pipefish are highly vulnerable to anthropogenic and environmental disturbances, but most species are currently considered Data Deficient by IUCN, requiring more biological and ecological research. Although syngnathids are well known for their unusual breeding biology, some aspects on the ecology of this family have rarely received attention. The knowledge on the factors governing syngnathids distribution is limited to some species and geographical regions. The present study is the first approach to predict syngnathid habitat preference in Spanish coasts, particularly in a marine National Park. In this study, Species Distribution Models (SDMs) were implemented to investigate the preferential habitat and distribution of the pipefish Syngnathus acus in Cíes Archipelago (Atlantic Islands of Galicia National Park, PNIA). Occurrence data of the species obtained from 2016 to 2018 surveys in PNIA were modeled as a function of bathymetric (depth, slope), substrate (sediment texture) and oceanographic (waves exposure) variables, using GAM, Random Forest and Maxent algorithms. From those SDMs, prediction models were built and the ensemble map of predictions was performed. The variables that most determined the distribution of the species were depth and wave exposure. The results of this study provide information on (1) habitat preference in the most dominant species in PNIA, the pipefish S. acus, towards sustainable management of this species in the National Park, and (2) predictive statistical tools for proper spatial conservation plans of this syngnathid species.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The ecological diversity of benthic invertebrates from bottom trawl surveys was mapped for the Flemish Cap, a plateau of similar to 200 km radius in the northwest Atlantic. Species density (SpD), the exponential Shannon diversity index (e(H)(')) and Heip's index of evenness ((E) over tilde') were measured at different spatial scales. Continuous surfaces of each were created to 2000 m depth using predictive distribution models based on random forest (RF) algorithms. When fishing effort was included as an independent variable in the RF models, it was the most important predictor of sample SpD but unimportant in predicting e(H)(') and only a minor predictor of (E) over tilde'. In the absence of a historical baseline, we used a novel approach to evaluate spatial impacts of fishing on diversity by simulating and comparing spatial SpD prediction surfaces using response data associated with different levels of fishing effort. Although it is not possible to fully evaluate the precise nature of the impact of fishing on the ecological diversity, our models have identified Sackville Spur, Flemish Pass and south of Flemish Cap as the areas of greatest impact. Combining minimum bottom salinity, annual primary production range, fishing effort and biomass of sponges and small gorgonian corals, resulted in the best performing generalized additive model, explaining 73% of the total variance in SpD. Although current closures to protect vulnerable marine ecosystems from the adverse impacts of bottom fishing activities protect an important part of the ecological diversity associated with the deeper communities, unique and representative habitats on top of the Cap remain unprotected.

We examined four species of sea pen (Anthoptilum grandiflorum, Halipteris finmarchica, Pennatula aculeata and Pennatula grandis) collected from the Gulf of St. Lawrence and mouth of the Laurentian Channel, eastern Canada. An exponential length-weight relationship was found for all four species, where growth in weight was progressively greater than growth in length with increasing colony size. Halipteris finmarchica, P. grandis and P. aculeata presented the better allometric fits, explaining over 80% of the variance. In addition, a count of growth increments visible in transverse sections in 86 A. grandiflorum and 80 P. aculeata samples was made. Presumed ages ranged between 5 and 28 years for A. grandiflorum and 2 and 21 years for P. aculeata. Radiocarbon assays were inconclusive and could not be used to confirm these ages; further age validation is required. Radial growth of the rod is slow during the first years, increasing at intermediate sizes of the colony and slowing down again for large colonies. Similar results were obtained from the relationship between colony length and number of growth increments where a logistic model was the best fit to the data. On average Spearman's rank correlations showed 11% of shared variance between sea pen length or weight and environmental variables. Bottom temperature and salinity, depth and summer primary production were significantly correlated to sea pen size for most species.

The structure, composition and distribution of epibenthic invertebrate assemblages on the Tail of the Grand Bank of Newfoundland and Flemish Cap (northwest Atlantic) were sampled using depth-stratified trawls. Faunal analysis of 152 uniquely identified taxa produced hierarchical synoptic tables of species associations with diagnostic indicators based on species fidelity. Twelve spatially coherent epibenthic megafaunal assemblages were identified, each with relatively sharp faunal boundaries and unique species attributes. These assemblages were shown a posteriori through ANOSIM to have statistically different species compositions, and were nested within three major regional-scale faunal groups: (I) the continental shelf of the Tail of the Grand Bank, typified by the sea cucumber Cucumaria frondosa and the sand dollar Echinarachnius parma; (II) the upper slope of the Grand Bank and top of Flemish Cap, typified by the sponges Radiella hemisphaerica and Iophon piceum and the sea star Ceramaster granularis; and (III) the lower slope of the Grand Bank and Flemish Cap, typified by the sea urchin Phormosoma placenta, and the sea pens Anthoptilum grandiflorum and Funiculina quadrangularis. Comparisons with literature on benthic species associations from a half century ago suggest that the assemblages identified herein have persisted in the area at least for decades. Detrended correspondence analysis (DCA) identified a well-defined biological gradient along the first axis with very high species turn-over. Ten environmental variables (including Trawling Intensity) were significantly correlated with the ordinated data. At one extreme the continental shelf faunal group (I) was associated with shallow depth (mostly, less than 200m), coarse sediments and cold and fresh water associated with the Labrador Current. At the other extreme the lower slope faunal group (III; stations below 500–600m throughout the study area) was strongly associated with deep water, muddy sediments, and warmer and saltier water. Conditional tests under a step-wise model identified the percentage of mud as having the greatest explanatory power (40%) of the tested environmental variables. Trawling Intensity explained 11% of the variation in the full data set in marginal tests. Species richness in the deep water assemblages (Cluster III) was significantly and negatively correlated with fishing intensity. The species most directly associated with high trawling intensity in the DCA were the hard-shelled scavenging and predatory gastropods and a thick-shelled bivalve, consistent with expectations based on the trawling impact literature. Our study fills a critical knowledge gap in this important fishing area, and our novel regional-scale maps of the epibenthic assemblages will facilitate the development of ecosystem-based models linking benthic and pelagic systems and inform biodiversity conservation.

Recent studies on deep-sea sponges have focused on mapping contemporary distributions while little work has been done to map historical distributions; historical distributions can provide valuable information on the time frame over which species have co-evolved and may provide insight into the reasons for their persistence or decline. Members of the sponge family Geodiidae are dominant members of deep-sea sponge assemblages in the northwestern Atlantic. They possess unique spicules called sterrasters, which undergo little transport in sediment and can therefore indicate the Geodiidae sponge historical presence when found in sediment cores. This study focuses on the slopes of Flemish Cap and Grand Bank, important fishing grounds off the coast of Newfoundland, Canada, in international waters. Sediment cores collected in 2009 and 2010 were visually inspected for sponge spicules. Cores containing spicules were sub-sampled and examined under a light microscope for the presence of sterrasters. These cores were also dated using X-radiographs and grouped into five time categories based on known sediment horizons, ranging from 17,000 years BP to the present. Chronological groupings identified Geodiidae sponges in four persistent sponge grounds. The oldest sterrasters were concentrated in the eastern region of the Flemish Cap and on the southeastern slope of the Grand Bank. Opportunistic sampling of a long core in the southeastern region of the Flemish Cap showed the continuous presence of sponge spicules to more than 130 ka BP. Our results indicate that the geodiids underwent a significant range expansion following deglaciation, and support a contemporary distribution that is not shaped by recent fishing activity.

The United Nations General Assembly Resolution 61/105, concerning sustainable fisheries in the marine ecosystem, calls for the protection of vulnerable marine ecosystems (VME) from destructive fishing practices. Subsequently, the Food and Agriculture Organization (FAO) produced guidelines for identification of VME indicator species/taxa to assist in the implementation of the resolution, but recommended the development of case-specific operational definitions for their application. We applied kernel density estimation (KDE) to research vessel trawl survey data from inside the fishing footprint of the Northwest Atlantic Fisheries Organization (NAFO) Regulatory Area in the high seas of the northwest Atlantic to create biomass density surfaces for four VME indicator taxa: large-sized sponges, sea pens, small and large gorgonian corals. These VME indicator taxa were identified previously by NAFO using the fragility, life history characteristics and structural complexity criteria presented by FAO, along with an evaluation of their recovery trajectories. KDE, a non-parametric neighbour-based smoothing function, has been used previously in ecology to identify hotspots, that is, areas of relatively high biomass/abundance. We present a novel approach of examining relative changes in area under polygons created from encircling successive biomass categories on the KDE surface to identify "significant concentrations" of biomass, which we equate to VMEs. This allows identification of the VMEs from the broader distribution of the species in the study area. We provide independent assessments of the VMEs so identified using underwater images, benthic sampling with other gear types (dredges, cores), and/or published species distribution models of probability of occurrence, as available. For each VME indicator taxon we provide a brief review of their ecological function which will be important in future assessments of significant adverse impact on these habitats here and elsewhere.

Random forest generated species distribution models have been produced for black corals, large gorgonian corals and sea pens in the NAFO regulatory area using a suite of 23 poorly correlated environmental variables. All models performed well, producing cross-validated AUC values of 0.937, 0.885 and 0.888 respectively. Prediction surfaces for the three species groups produced clearly defined areas of high occurrence probability. These can be used to identify areas for conservation where black corals and the vulnerable marine ecosystem indicators, the large gorgonian corals and sea pens, are likely to occur.

Five species of aglaopheniid hydroids (Aglaophenopsis cornuta, Cladocarpus diana, C. formosus, C. integer, and Nematocarpus ramuliferus) were collected from the Flemish Cap, Flemish Pass, and Grand Banks of Newfoundland during surveys with bottom trawls, rock dredges, and scallop gear. All are infrequently reported species, with C. diana being discovered for the first time since its original description from Iceland. We document here the southernmost collections of C. diana and N. ramuliferus, both previously unknown in the western Atlantic. Each of the five species is described and illustrated based on fertile material, a key is provided for their identification, and bathymetric distributions are noted. Known depth ranges are extended for A. cornuta, C. diana, and C. integer. Aglaophenopsis and Nematocarpus are recognized as genera distinct from the polyphyletic Cladocarpus, based on the unique structure of the phylactocarp in the former, and the existence of appendages with nematothecae (ramuli) on almost all thecate internodes of hydrocladia in the latter. These appendages occur even in the absence of gonothecae, and are here considered defensive structures that protect the hydranths. In differing from typical phylactocarps, we accept the contention that they are characters of generic value.

Distributions of deep-sea fish, benthic invertebrates and the effects of deep-sea bottom trawling were studied based on data collected in 2005 from a joint collaboration survey undertaken between the Spanish Institute of Oceanography and a deep-sea trawler on the Hatton Bank (north-east Atlantic). A total of 163 valid bottom trawl hauls (600–1600 m) were analysed. The main trawlable grounds were located on the sedimentary seabed of the western flank of the bank (Hatton Drift). Grenadiers and smoothheads were predominant in the trawl catches (67% and 11.8% by weight respectively). Both species were abundant along the western flank. Deep-water sharks accounted for 7.4% of weight, and were abundant along the south-eastern slopes. Chimerids, lotids, morids and other deep-sea species were also taken as by-catch. Grenadiers and deep-water sharks dominated the discards. By-catches of cold-water corals were generally associated with the rocky outcrop and were more abundant at the top of the bank. Abundant by-catches of large sponges, characteristic of sponge-dominated biotopes, were taken from the eastern flank.