Environmental Drivers of Mesophotic Echinoderm Assemblages of the Southeastern Pacific Ocean

Mesophotic ecosystems (50–400 m depth) of the southeastern Pacific have rarely been studied because of the logistical challenges in sampling across this remote zone. This study assessed how oxygen concentrations and other environmental predictors explain variation in echinoderm assemblages at these mesophotic systems, where this group is among the predominant fauna. We compiled data on echinoderm taxa at 91 sampling stations, from historical and recent surveys (between 1950 and 2019), covering a longitudinal gradient of approximately 3,700 km along with the Nazca, Salas y Gómez, and Juan Fernández ridges. Uni- and multivariate model-based tools were applied to analyze the patterns of benthic fauna in relation to environmental factors. Our results indicate a significant positive relationship between echinoderm species richness and depth, oxygen, and salinity. Changes in echinoderm community composition were significantly explained by oxygen, longitude, and chlorophyll-a. We observed notable species turnovers at ∼101 and ∼86°W, where assemblages tend to be more variable across stations. This turnover possibly reflects the effects of physical barriers to dispersion (e.g., currents) and habitat changes. Echinoderm assemblages observed around Easter and Desventuradas Islands presented a high occurrence of potentially endemic taxa and distinct species assemblages. This study is the first to assess the structure of mesophotic echinoderm assemblages of the southeastern Pacific Ocean along a large spatial scale. The information reported here could help design appropriate management tools for the vast, recently created, marine protected areas in the southeastern Pacific

First in situ observations of the deep-sea carnivorous ascidian Dicopia antirrhinum Monniot C., 1972 in the Western Mediterranean Sea

Dicopia antirrhinum C. Monniot, 1972 is a rare species of deep-sea ascidian belonging to the Family Octacnemidae, reported at depths of 1000-2500 m in European Atlantic waters. Adult individuals have never been reported before in the Mediterranean Sea, where only seven juvenile specimens were found in 1975 at 500 m water depth in the Central basin (Malta). The affinities of these specimens with D. antirrhinum were noted, but lack of some typical characters of the species in juveniles prevented a definite taxonomical identification. No other member of the Octacnemidae has ever been found in the Mediterranean. In this study we describe the sampling of an adult specimen of D. antirrhinum at around 1100 m water depth on the flank of the La Fonera (Palamós) canyon, Northwestern Mediterranean, confirming their presence in the Mediterranean Sea. We also observed 5 individuals of this species on their natural habitat with a Remotely Operated Vehicle (ROV). Our results highlight the potential occurrence of Octacnemidae, the presence of which has been largely overlooked, in several deep-sea canyon areas within the Western Mediterranean basin. These observations are important because they indicate the need for increased sampling effort with new technologies, such as ROVs, in ecologically relevant habitats such as canyons, in order to obtain a more accurate picture of deep-sea biodiversity in the Mediterranean Sea

Comparison between ROV video and Agassiz trawl methods for sampling deep water fauna of submarine canyons in the Northwestern Mediterranean Sea with observations on behavioural reactions of target species

In this paper we present a comparison between Remotely Operated Vehicle (ROV) and Agassiz trawling methods for sampling deep-water fauna in three submarine canyons of the Northwestern Mediterranean Sea and describe the behavioural reactions of fishes and crustacean decapods to ROV approach. 10 ROV dives, where 3583 individuals were observed and identified to species level, and 8 Agassiz trawls were carried out in a depth range of 750-1500 m. As noticed in previous studies, abundances of fishes and decapod crustaceans were much higher in the ROV videos than in Agassiz trawl samples, as the latter are designed for the retrieval of benthic, less motile species in permanent contact with the bottom. In our observations fish abundance was one order of magnitude higher with ROV (4110.22 ind/km2) than with Agassiz trawl (350.88 ind/km2), whereas decapod crustaceans were six times more abundant in ROV videos (6362.40 ind/km2) than in Agassiz samples (1364.52 ind/km2). The behaviour of highly motile fishes was analysed in terms of stationary positioning over the seafloor and avoidance or attraction to ROV approach. The most frequently occurring fish species Coelorinchus mediterraneus, Nezumia aequalis, Bathypterois dubius, Lepidion lepidion, Trachyrincuss scabrus and Polyacanthonotus rissoanus did not react to the presence of the ROV in most cases (>50%). Only B. dubius (11%), Lepidion lepidion (14.8%), P. rissoanus (41%) and T. scabrus (14.3%) reacted to ROV approach. More than 60% of less motile species, such as crustacean decapods, did not respond to ROV presence either. Only 33.3% of Geryon longipes, 36.2% of Munida spp. and 29.79% of Pagurus spp. were observed avoiding or defensively reacting to the ROV. The comparison of results obtained with ROV and trawl sampling is of ecological relevance since ROV can report observations in areas where trawling is technically unfeasible. The lack of reaction by most fish and crustacean decapod specimens further confirms that ROV surveying is an efficient technique to assess abundance and species composition in deep-sea waters for these motile species and questions trawl-based estimations

Visual faunistic exploration of geomorphological human-impacted deep-sea areas of the north-western Mediterranean Sea

This study reports the composition and distribution of demersal megafauna from various north-western Mediterranean submarine areas such as canyons, seamounts and landslides between 60-800 m depth, based on remotely operated vehicle (ROV) observations. From a total of 30 h of video, 4534 faunistic observations were made and analysed in relationship to environmental factors (i.e. topography, substrate type and depth). In addition, anthropogenic impact was quantified by grouping observations in four categories: fishing nets, longlines, trawl marks and other litter. The different targeted environments showed similarities in faunal composition according to substrate, depth and topography. Our results also indicated the presence of anthropogenic impact in all the sampled areas in which litter and trawl marks were the most observed artefacts

Deep-sea litter in the Gulf of Cadiz (Northeastern Atlantic, Spain)

This study describes the distribution and composition of litter from the Gulf of Cadiz (Northeastern Atlantic, Spain), a region of confluence between the Atlantic and Mediterranean, with intense maritime traffic. Several geological features, such as canyons, open slopes and contourite furrows and channels, were surveyed by remotely operated vehicle (ROV) observations between depths of 220 and 1000 m. Marine litter was quantified by grouping the observations into six categories. Our results indicate the presence of markedly different habitats in which a complex collection of different types of litter accumulate in relation to bottom current flows and maritime and fishing routes. This result justifies a seascape approach in further anthropogenic impact studies within deep-sea areas.Postprint (author's final draft

Evaluating future climate change exposure of marine habitat in the South East Pacific based on metabolic constraints

IntroductionOn-going climate change is now recognized to yield physiological stresses on marine species, with potentially detrimental effects on ecosystems. Here, we evaluate the prospect of using climate velocities (CV) of the metabolic index (Φ) for assessing changes in habitat in the South East Pacific.MethodsOur approach is based on a species with mean ecophysiotype (i.e. model species) and the use of a global Earth System Model simulation (CESM-LE) under RCP 8.5 scenario. The SEP is chosen as a case study as it hosts an Oxygen Minimum Zone and seamounts systems sustaining local communities through artisanal fisheries.Results and DiscussionOur results indicate that CVΦ pattern is mainly constrained by the oxygen distribution and that its sign is affected by contrasting oxygen trends (including a re-oxygenation in the upper OMZ) and warming. We further show that CVΦ is weakly dependent on physiological traits composing Φ, which conveys to this metrics some value for inferring the projected mean displacement and potential changes in viability of metabolic habitat in a region where physiological data are scarce. Based on sensitivity experiments to physiological traits and natural variability, we propose a general method for inferring broad areas of climate change exposure regardless of species-specific Φ. We show in particular that for the model used here, the upper OMZ region can be considered a “safe” area for the species with ecophysiotype close to that of 71 species used to derive the model species. Limitations of the approach and perspectives of this work are also discussed

Taxonomy, distribution and community composition of megabenthic non-crustacean invertebrates in the deep Catalan margin = Taxonomía, distribución y composición de la comunidad de invertebrados no crustáceos del megabentos del Mar Catalán profundo

[spa] En el estudio de la presente tesis se pretende realizar una exhaustiva clasificación taxonómica de las especies de invertebrados no-crustáceos muestreados en el margen catalán profundo, así como determinar sus patrones de distribución y su composición faunística. El material utilizado fue recopilado a lo largo de 10 campañas oceanográficas realizadas entre octubre 2008 y abril 2013 en el Mediterráneo occidental en el marco de los Proyecto Nacionales y Europeos PROMETEO, DOSMARES, BIOFUN, PROMARES y EUROLEON. Las áreas de muestreo incluyeron el Cañón de Blanes y su talud adyacente, los cañones de la Fonera y Cap de Creus, dos montañas submarinas ubicadas en el Golfo de Valencia y el Canal de Ibiza, y dos deslizamientos submarinos del Canal de Ibiza. Adicionalmente se realizó una campaña transmediterránea en la cual se muestrearon tres áreas del Mediterráneo, oeste, central y este. Se utilizaron para la recolección de muestras tanto métodos de muestreos tradicionales (artes de arrastre) como nuevas tecnologías de muestreo visual (ROV). Las profundidades muestreadas mediante ROV fueron de entre los 60 m y los 1100 m de profundidad; y entre los 850 m y los 2850 m mediante muestreos tradicionales. Se obtuvieron 5877 individuos distribuidos en 8 Filos, 18 Clases y 69 especies. En la presente Tesis se describe por primera vez en el Mediterráneo la presencia de dos especies: el equinoideo regular Gracilechinus elegans (Düben & Koren, 1844) y la ascidia carnívora Dicopia antirrhinum C. Monniot, 1972. Igualmente se describió la presencia de tres especies consideradas ‘raras’: las holoturias endémicas Hedingia mediterranea (Bartolini Baldelli, 1914) y Penilpidia ludwigi (von Marenzeller, 1893) así como el sipúnculido Phascolosoma (Phascolosoma) turnerae Rice, 1985. Asimismo se amplió el rango de distribución batimétrica de 11 especies. Los datos se analizaron además de a nivel puramente taxonómico, a nivel poblacional, revelando mayores densidades (individuos • km -2) y biomasas (kg • km -2) en zonas de cañones submarinos. También se observó que a nivel faunístico el grupo más abundante fueron los equinodermos, representando el 57% del total de especímenes recolectados. Si pasamos a considerar los datos obtenido mediante imágenes de ROV, se recopilaron un total de 4520 observaciones faunísticas de los tres hábitats geomorfológicos descritos (un cañón, dos montes y dos deslizamientos submarinos) y entre los cuales se describieron similitudes en cuanto a comunidades faunísticas en función de parámetros tales como la profundidad, geomorfología y tipo de substrato.[eng] The study of the non-crustacean invertebrates dwelling on the deep Mediterranean Sea is of interest for different marine science disciplines, being the diversity of species and their distributions largely unexplored. In fact, the present Thesis conducted an effort in order to increase valid scientific information not only at taxonomical level, but also at the level of community composition and distribution. Detailed data on the reproductive biology and ethology was required for some group of ecological relevance in order to solve some relevant gaps of information. Ten multidisciplinary oceanographic cruises were conducted between October 2008 and April 2013 to sample the deep seafloor of the western Mediterranean Sea. The sampling areas included the Blanes Canyon and its adjacent open slope, the Palamós (also named La Fonera) and Cap de Creus Canyons, sea hills in the Gulf of Valencia and Eivissa Channel, and landslides on the Eivissa Channel. A total of 223 benthic trawls were completed resulting in a total swept area of 10.3 km². Samples were also observed by means of two ROV’s. Resulting from these ten cruises, this work evidenced and updated species bathymetrical and geographical distributions ranges of non-crustacean invertebrate species by different methodologies (i.e. traditional and technologically advanced sampling). As a result of that effort, new faunistic reports were described: two first records (i.e. Gracilechinus elegans (Düben & Koren, 1844) Dicopia antirrhinum C. Monniot, 1972), three rare species (i.e. Hedingia mediterranea (Bartolini Baldelli, 1914), Penilpidia ludwigi (von Marenzeller, 1893) and Phascolosoma (Phascolosoma) turnerae (Rice, 1985), and eleven extensions of maximum depth range of distribution. This new record for Dicopia antirrhinum increased the lower depth limit of this genus in the Mediterranean Sea from 500 to 1100m depth. This finding contributes to the knowledge of the poorly investigated Mediterranean deep ascidian fauna, in sharp contrast with the relatively well-known shallow-water Mediterranean ascidians. We also observed that densities and biomass of non-crustacean invertebrates were pointed to be significantly higher in submarine canyons than in surrounding open slopes. These findings suggest submarine canyon habitats of the north-western Mediterranean Sea as hotspots of benthic megafauna communities. The most abundant group in terms of density was the Phylum Echinodermata. A Phylum largely undescribed in deep Mediterranean waters, when compared with the faunistic data already available for the Atlantic. All specimen sampled of this Phylum were classified, described and their bathymetrical ranges re-defined. These results were compared and extended with the previous published literature, checking, validating (or discarding) all available information. The reproductive pattern of the most abundant species of Asteroidea in the present study, Ceramaster grenadensis was studied. The size pattern distribution of show a depth related trend showing smaller sizes at greater depths (dwarfism), as observed in other species of Atlantic Ocean. Additionally, juveniles were sampled at the deepest range of distribution of the species (i.e. 2250 m). Histological analysis of C. grenadensis gonads, revealed a semicontinous reproductive patterns, with a maximum of reproductive activity in autumn (maximum values of Gonadal Index). This finding coincides with some already published study for other deep-sea Mediterranean Echinoderm species such as B. lyrifera. The in situ faunal sampling with video technologies (i.e. Remotely Operated Vehicles; ROVs) showed the occurrence of different species assemblage compositions in different geomorphological habitats such as, submarine canyons, sea hills and landslides. Benthic cnidarian communities were observed in seamount rocky areas while submarine landslides fauna were mainly composed by vagil fauna as fishes and crustaceans. The description of characteristics seascape units might help to estimate taxonomical group in other similar but presently unexplored deep-sea areas. Finally, this study suggests that an increasing effort combining traditional and technologically-new sampling methods is advisable in order to obtain a more complete overview of species inhabiting the different deep-sea continental margins

Seafloor litter at oceanic islands and seamounts of the southeastern Pacific

International audienc

Chloeia rozbaczyloi, a new species of polychaete (Archinominae: Amphinomidae) and first record of the family for the Nazca Ridge, southeastern Pacific Ocean

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