A set of lander deployments in a deep marine protected area (MPA; El Cachucho) combining environmental sensors and a baited camera provided insight on the relationship between faunal behavior and ...oceanographic dynamics. Landers were deployed at different depths, ranging from 500 to 960 m for a period of 24–26 h. A total of 10,989 photographs were downloaded and synchronized using a time code with all the environmental variables recorded (pressure, temperature, salinity, water current, and direction). Total richness accounted for 41 species of different taxonomic groups (21 fishes, 11 crustaceans, 6 echinoderms, and 3 molluscs). The most abundant species were Synaphobranchus kaupii, Mora moro, Phycis blennoides, Helicolenus dactylopterus, and Etmopterus spinax. Arrival times (Tarr) and maximum number of individuals (Nmax) greatly differed among stations.
Cluster analysis showed two main faunal groups in relation to depth: those close to the top of the bank and those in the flanks. Species densities were estimated using Priede's equations and compared with those obtained in previous studies using trawl samplers. The relation of species with environmental variables showed high variability depending on the location of the station and the associated variables (depth, current, and water masses). Near-bottom dynamics were consistent with previously known oceanographic patterns at the bank, dominated by background anticyclonic recirculation along the flanks overlaid by strong tidal cycles. Current and hydrography tidally driven phases showed an evident effect in the arrival of species at some locations. Species appeared during specific periods matching the beginning of the flooding phase or end of the ebb phase. Movement rates (cm s−1) were estimated for some invertebrate species, such as crabs (Bathynectes maravigna, 0.66; Pagurus sp., 0.09), the gasteropod Colus gracilis (0.15), and echinoderms (Cidaris cidaris, 0.04; Araeosoma fenestratum, 0.23).
•Landers provide valuable information on hydrographic dynamics and benthic fauna.•Tidal cycles have great importance on the deep-sea ecosystem dynamics.•Richness, abundance and species behavior were estimated from baited cameras in a MPA.•Movement rates of some deepwater invertebrates were recorded for the first time.•Current and tide phases have evident effect in the arrival of species at some landers.
Gorgonians play a fundamental role in the deep sea (below 200 m depth), composing three-dimensional habitats that are characterized by a high associated biodiversity and playing an important part in ...biogeochemical cycles. Here we describe the use of a benthic lander to monitoring polyps activity, used as a proxy of gorgonian feeding activity of three colonies of Placogorgia sp. Images cover a period of 22 days with a temporal resolution of 30 min. In addition, this seafloor observatory is instrumented with oceanographic sensors that allows continuous monitoring of the hydrographic conditions in the site. Deep-learning is used for automatic detection of the state of the polyps registered in the images. More than 1000 images of 3 large specimens of gorgonians are analyzed, annotating polyps as extended or retracted, using the semantic segmentation algorithm ConvNeXt. The segmentation results are used to describe the feeding patterns of this species. Placogorgia sp. shows a daily pattern of feeding conduct, depending on the hours of day and night. Using a Singular Spectrum Analysis approach, feeding activity is related to currents dynamics and Acoustic Doppler Current Profile (ADCP) return signal intensity, as proxy of suspended matter, achieving a linear correlation of 0.35 and 0.11 respectively. This is the first time that the behavior of the Placogorgia polyps, directly related to their feeding process, is described.
Microplastic fibres are a widespread pollutant in the marine environment. Their presence has been searched for in marine sponge specimens of a museum, collected over 20 years ago. The pollutant was ...observed in more than half of the samples analysed, allowing a reference point to be fixed in the past. Analysis has demonstrated that fibres were vagrant in the water column and were incorporated actively by sponges. Inclusion into bottom-fixed sponges has been demonstrated for the natural environment. The study of microplastic in organisms collected in the past and stored in natural history collections is the key for fixing reference points and build up temporal trends, especially considering the lack of studies on this topic before 1980. The idea of using animals preserved in natural history museums could be extended to other pollutants in order to search for reference points or past baselines.
•Microplastic fibres debris were searched in elder sponge museum collection.•Microplastic fibres debris were found in specimens of Porifera collected more than 20 years ago.•Elder animals museum’s collections are the only way to assess past levels of microplastic debris in marine biota.•Analysing other museum’s collection would help in setting the birth date of interaction between plastic and biota.•Knowing the beginning of interaction could give useful insight to understand the effects of this harmful pollutant.
The aim of this study was to describe the epibenthic and demersal communities of the Avilés Canyon System (ACS) in relation to the environmental variables that characterize their biotope. ACS ...(Cantabrian Sea, NE Atlantic) was recently included in the Natura 2000 network as a Site of Community Importance (SCI). Data of faunal biomass derived from 6 surveys carried out using beam trawl and otter trawls in 2009 and 2010 within INDEMARES and ERDEM projects. Data were divided into two groups to obtain information about the two ecological compartments: benthic and demersal. The total number of species used in this analysis ascended to 116 in the case of benthic organisms and 110 in the case of demersal. Hierarchical clustering analysis was applied to obtain groups of samples similar in terms of species composition for the two ecological components. Depth was the main discriminating factor for grouping hauls, showing high consistency of bathymetric range independently from the compartment examined. Six groups were identified by depth as follows: medium shelf (∼100–200 m), external shelf (∼150–300m), shelf break (∼300–400 m), upper-slope (∼500–700 m), upper middle-slope (∼700–1100 m), and lower-middle-slope (1200–1500 m). SIMPER analysis on biomass values was performed to determine the structure of the faunal assemblages observed for each group in both compartments. Using biomass values for the analysis allowed for the exploration of groups playing important roles in ecosystem functioning and energy fluxes taking place on the sedimentary bottom of this SCI. Finally, CCA analysis revealed that the main environmental drivers were depth, broad scale bathymetric position index (BPI), near-bottom salinity, sedimentary type, and dynamics related variables (Q50 phy and So). This study gives an inventory of the soft bottom assemblages along a very wide depth range (100–1500 m) inside a SCI, linking both epibenthic and demersal communities with the biotope preferences. This study contributes to fundamental knowledge on soft-bottom communities as a pre-requisite, necessary for the next steps in terms of management framework in the SCI.
•Data of bottom related fauna in a marine SCI were analysed in North of Spain.•Soft bottom communities of the Avilés Canyon System were determined.•Epibenthic and demersal assemblages described followed a bathymetric pattern.•Environmental linkages were observed related with physics and geological factors.•BPI broad, Salinity, Bottom type and sedimentary dynamics influence assemblages.
Abstract
The large fish indicator (LFI) was developed to support the North Sea fish community Ecological Quality Objective (EcoQO) pilot study, intended to establish an operational ecosystem approach ...to management. Subsequently, procedures established in the North Sea were applied to the Celtic Sea to derive an LFI and target specific to this region. The Marine Strategy Framework Directive (MSFD) requires EU Member States sharing marine regions to cooperate using the Regional Seas Conventions, and using indicators already adopted by them. The MSFD explicitly suggests the LFI as a foodweb indicator, but it could equally well be used to monitor biodiversity. Here, we apply the established rationale to develop an LFI and target specific to the southern Bay of Biscay. Despite declining in the 1990s, the LFI subsequently recovered to near original values in 2008. Previously, relationships between the LFI and fishing pressure have involved lengthy time-lags. We observe a similar relationship, but with shorter lag. The nature of the larger species responsible for much of the change in the LFI may explain this difference, and might also suggest that, in the Bay of Biscay, the LFI is more appropriately used as a biodiversity indicator, rather than a foodweb indicator.
The trophic niche width and feeding strategy (FS) of juvenile European hake were studied during three trawl surveys in two different areas of the Mediterranean Sea. Both of these aspects of trophic ...behaviour were analysed as function of different biotic and abiotic factors. Prey were grouped by factors such as size, swimming behaviour and energy density. The trophic niche breadth values observed (2.25–2.89) were very similar regardless of the geographic area (geomorphology) and season. The FSs analysed were also quite similar regardless of the geographic area (geomorphology) and season, or predation environment (bottom or water column). Conversely, the FSs were linked with predator size. Increased predator size allowed changes in predatory behaviour through the development of preferences for larger and more energy-rich prey. The changes in FS from generalist to specialist began at a total length (TL) of approximately 12cm in both populations analysed. At larger sizes, the juveniles of both populations became more specialised, as confirmed by the reduction in the breadth of the individual trophic niche. The observed simultaneous changes in the FS, which occurred regardless of the geomorphology and seasonal characteristics, suggest that this shift is driven primarily by endogenous factors. The influence of body size on the foraging behaviour of European hake in the early life stages after bottom recruitment is a crucial information for the application of ecosystem mass-balance models.
•We analyse the trophic ecology of two different juvenile European hake populations.•Prey were grouped by factors such as size, swimming behaviour and energy density.•We analyse their feeding strategy in relation to biotic and abiotic factors.•Changes in feeding strategy are linked with both predator and prey size.•We report a specialism in feeding behaviour toward prey with higher energy density.
Gorgonians play a fundamental role in the deep sea (below 200 m depth), composing three-dimensional habitats that are characterized by a high associated biodiversity and playing an important part in ...biogeochemical cycles. Here we describe the use of a benthic lander to monitoring polyps activity, used as a proxy of gorgonian feeding activity of three colonies of Placogorgia sp. Images cover a period of 22 days with a temporal resolution of 30 min. In addition, this seafloor observatory is instrumented with oceanographic sensors that allows continuous monitoring of the hydrographic conditions in the site. Deep-learning is used for automatic detection of the state of the polyps registered in the images. More than 1000 images of 3 large specimens of gorgonians are analyzed, annotating polyps as extended or retracted, using the semantic segmentation algorithm ConvNeXt. The segmentation results are used to describe the feeding patterns of this species. Placogorgia sp. shows a daily pattern of feeding conduct, depending on the hours of day and night. Using a Singular Spectrum Analysis approach, feeding activity is related to currents dynamics and Acoustic Doppler Current Profile (ADCP) return signal intensity, as proxy of suspended matter, achieving a linear correlation of 0.35 and 0.11 respectively. This is the first time that the behavior of the Placogorgia polyps, directly related to their feeding process, is described.
Silvery pout (Gadiculus argenteus, Guichenot, 1850) is a very common and quite abundant species in Galicia and in the Cantabrian Sea, which plays an important role in the Cantabrian Sea ecosystem ...since it is one of the main trophic resources of many commercial species. In this study we analysed data obtained from a series of bottom trawl surveys carried out annually in autumn from 1990 to 2010 along the continental shelf of Galicia and the Cantabrian Sea. We examined the changes observed in the distribution patterns and abundance indices of this species and relate these with the occurrence and abundance of other commercial species in the area like hake (Merluccius merluccius), megrims (Lepidorhombus spp.) and blue whiting (Micromesistius poutassou). A significant correlation was found (R=0.45, p=0.038) between the abundance index of G. argenteus and hake, one of its main predator. A total of 137,780 stomachs of 19 most important predators were analysed during this period. The volume percentage (% V) of G. argenteus in the diet of some species was very high as it was the case of Lepidopus caudatus (94%) or Molva macrophthalma (58.2%). The frequency of occurrence (% FO) was important for these and other commercial species such as Lepidorhombus whiffiagonis (12.3%), Zeus faber (11.1%), Helicolenus dactylopterus (9.5%), Eutrigla gurnardus (8.6%), Lophius budegassa (8.9%) and M. merluccius (6.4%). There were evidences of density dependant feeding on G. argenteus. A significant correlation between G. argenteus yearly abundance in the stomachs of the assemblage of its 19 predators and survey abundance was observed (R=0.8977, p<0.01). Also, high correlation has been observed between the yearly survey biomass indices of G. argenteus and its % FO in the stomachs of hake, megrims and blue whiting for some length ranges of these predators. G. argenteus is an extremely important species in Galicia and Cantabrian Sea due to both its abundance in the ecosystem and its trophic role as forage species.
•We analysed the role of silvery pout as trophic resource in North East Atlantic.•We studied 137,780 stomachs of its 19 main predator species during 10years.•Silvery pout is a very abundant species in North East Atlantic.•Evidences of density dependant feeding on silvery pout are provided.•Silvery pout is a key species in the area due to its trophic role as forage species.
Seasonal study of the diet and food consumption of juvenile hake has been carried out in the Central Mediterranean Sea (Southern Tyrrhenian Sea). Fish were the most important food resource in terms ...of weight (ca. 70%). Among the fish, Myctophidae and Sternoptychidae, which are usually distributed deeper than juvenile hake, are most important. During summer, Ceratoscopelus maderensis constituted up to 21% of weight of all prey, and Maurolicus muelleri represented almost 10%. During autumn M. muelleri became the most important food resource. The way in which these more deeply distributed prey enter shallower food webs relates to the daily vertical migrations of lanternfish. In upper water column strata at night or near dawn they become prey of the juvenile hake. Considering that trophic energy flows primarily downward, in the direction of the productivity gradient, the observed flow of energy from deep strata into epipelagic layers could be considered an inverse energy transfer. Daily food consumption of juvenile hake ranged between 4.11 and 4.72% of the body wet-weight (BWW). The application of a square-root model allowed calculation of the fraction of this consumption derived by ingestion of the more deeply distributed mesopelagic fish. Between 11.6% and 17.8% of food consumption was sustained by this energy flow. Such information is useful for understanding the interaction between communities distributed in different depth ranges and to reinforce the idea that marine communities are open systems in which migratory movements can dramatically change the assumptions and results of mass-balance models.
•We analyzed trophic relationships and food consumption of juvenile European hake.•We assessed an energy transfer between mesopelagic and neritic communities.•We assessed this energy flow in areas with upwelling or strong water circulation.•We identified hake as energy receiver and mesopelagic fish as energy donor.•We quantified that 1/5 of energy intake of hake is due to deeper distributed fish.
Predation, feeding strategy (FS) and food daily ration (DR) were analysed in juveniles of the European hakeMerluccius merlucciusduring a 24 h trawl survey carried out in the northwestern ...Mediterranean. Predatory activity, expressed as the stomach fullness index (FI) and prey digestion stage, was initiated in the early night and continued throughout the night, reaching maximum activity in the early morning. The feeding activity progressively decreased after this time, reaching a minimum before sunset, when a rest phase was observed. Changes in prey taxa during the 24 h cycle indicated that prey selection was time-of-day and predator-size dependent. Zooplankton crustaceans were mostly consumed during the night and in the early afternoon. The 2 main categories (euphausiids and mysids) comprising the zooplankton and hyperbenthos trophic resource of the hake, were consumed in a temporally shifted manner, such that the macrozooplankton (euphausiids) was consumed at night and the hyperbenthos (mysids) during the day. FS and length-distribution analysis indicated that early juveniles (9.3 ± 1.7 cm total length, TL) primarily fed on these resources in these periods. In contrast, advanced juveniles (12.0 ± 3.4 cm TL) preyed largely on decapod crustaceans and fishes and fed mostly during the day, exhibiting a more specialised FS. Differences in the DR were estimated using Exponential (Exp) and Square-root (Sq-r) models, the latter taking into account predator size. The Exp model yielded a mean consumption of 1.5% body wet weight (BWW) and the Sq-r model yielded mean values ranging between 4.09 and 5.09% BWW, with a difference between the 2 methods ranging from 63 to 70% larger for the latter method. Therefore, the application of the Sq-r model gives an alternative insight into the range of consumption in juvenile hakes.
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