Benthic Suspension Feeders Research Articles

A First Approach to the Marine Heterobranchia (Mollusca: Gastropoda) Fauna of Marettimo, Egadi Islands, MPA (Western Sicily, Mediterranean Sea)

For almost all the Sicilian islands, there are no faunistic data concerning marine Heterobranchia, which is one of the most sought-after groups of marine critters by photographers and diving enthusiasts all over the world. With the present study, carried out through underwater photography at various dive sites and stretches of coastline in the island of Marettimo, we made the first contribution to the knowledge of the marine Heterobranchia fauna present on this island of the Egadi archipelago. Through data collection, it was possible to document the presence of 43 species of marine Heterobranchia. Data analysis showed a remarkable homogeneity in the number of species between the examined sites. This is probably due to the peculiar environmental homogeneity present in the sites of this island, which are almost all rich in the presence of both benthic suspension feeders (the favorite prey of many groups of marine Heterobranchia) and environments full of crevices, grottos, and vertical walls, which are the preferred habitats of the majority of these mollusks. The higher number of marine heterobranch species found in Marettimo compared to the smaller number of species found on the other recently examined Sicilian islands (Pantelleria, Lipari, and Vulcano) is probably due to the massive presence of rich coralligenous biocoenoses and the particular hydrodynamic regime to which Marettimo is subject.

Influence of an innovative IMTA system (Mediterranean Sea, Italy) on environmental and biological parameters: Seasonal analysis

The influence of benthic suspension feeders as bioremediating organisms on water column seston and their ability to mitigate fish farm waste was assessed by monthly analyses for one year. A monthly monitoring from July 2020 to October 2021 of physico-chemical and biochemical variables of the water column and the sediment was performed in an in-shore mariculture plant located in the Mar Grande of Taranto (Italy), comparing two adjacent areas that differ in type of farming. The first (reference site) is a fish monoculture, while the second consists of an innovative Integrated Multi-Trophic Aquaculture system (IMTA site). The annual cycle of chlorophyll-a concentration showed values corresponding to mesotrophic/eutrophic conditions, with peak production in early fall (4.64 μg L−1). During the spring and summer sampling times, when the amount of aquaculture waste is greater than during the rest of the year, the reference site showed the highest lipid (151.73 μg L−1) and organic matter (189.00 mg g−1) values with respect to those at the IMTA site. The IMTA bioremediating organisms possibly acted as underwater gardens changing the seston quality and availability and providing protection and food for the zooplankton community, which showed higher abundance of individuals for most sampling times at the IMTA site, peaking during September and October in both 2020 and 2021 (max 232,985.20 ind m−3). Our results demonstrate the effectiveness of the considered IMTA system in mitigating the negative impact of organic matter release into the environment due to fish farming activities. The influence of bioremediating organisms on seston composition and concentration opened up mitigation as well as restoration scenarios.

High variability and enhanced nocturnal oxygen uptake in coral reef sponges

AbstractSponges are animals that feed by filtering water through their perforated body. We examined the in situ diel dynamics of sponge metabolism by continuously measuring the oxygen concentrations in the water inhaled and exhaled by undisturbed sponges. A clear daily pattern of oxygen removal was evident for six of the seven species we studied with their nocturnal oxygen removal being almost double the diurnal values (+ 86 ± 57%). Oxygenic photosynthesis by the sponge's symbiotic or endolithic phototrophic microbes may explain some of the diel difference, but significant day–night differences were also observed in three sponge species for which no evidence of photosynthetic activity (tested with imaging pulse‐amplitude‐modulation Fluorometry) was found. Mean oxygen removal (± 95% confidence interval for the mean) per species ranged from 1.7 ± 1 μmol O2 per liter (hereafter: μmol O2 L−1) for the low microbial abundance (LMA) sponge Callyspongia siphonella to 30.5 ± 10.5 μmol O2 L−1 for the high microbial abundance HMA) sponge Theonella swinhoei with considerable variation in oxygen removal across all scales (minutes to hours, within and among specimens). Events of high oxygen removal (> 50 μmol L−1) were regularly observed for five of the seven species and were predominantly nocturnal, occasionally lasting several hours. The high variability in oxygen removal stresses the need for long‐term in‐situ measurements of benthic suspension feeders metabolism.

High frequency monitoring of feeding activity in benthic suspension feeders

AbstractSuspension feeders ecosystem role and services are mainly driven by their efficiency in clearing particles from the water column. As such there is an interest on suspension feeders feeding activity and how they interact with the ecosystem. Advancing research on feeding response requires experimental designs where individuals can be exposed to continuously changing environments and where feeding activity can be monitored at a high frequency and at different time scales. However, interindividual variability or temporal dynamics in feeding behaviors cannot be investigated properly by the methods commonly used. There are several methods to monitor feeding activity of suspension feeders. Among them, the flow‐through method allows individuals to be exposed to changing conditions. As with the other existing methods, the flow‐through method is labor intensive limiting both the number of individuals that could be observed simultaneously and the time resolution of observations. The flow‐through method is constrained by the need to measure the flow rate through the chambers and to take samples to determine particle concentration in the water. In this work, we automated the standard flow‐through method using microcontroller based prototyping. The result is a methodological approach that continuously monitor feeding at high frequency and on a larger number of individuals while reducing handling and measurement errors. As such, this method brings a solution to the current limitations when studying suspension feeders feeding behaviors. This work provides the description and assessment of the automated set‐up, which is an end to end solution that can readily assembled and configured.

HOW CARBON IMMOBILIZATION FROM RESTORED MARINE FORESTS MAY HELP CLIMATE CHANGE MITIGATION PLANS?

The ocean transformation due to the direct or indirect human influence is a fact. One of the most affected ecosystems are the benthic ones, where bottom trawling, urban/agricultural development and climate change (among other things) deeply transform the bottom communities. Among these threatened communities, the marine forest is the most extended. The marine forest is composed of benthic macroalgae, phanerogams and suspension feeders (sponges, corals, gorgonians, etc.) which conform three-dimensional living structures. Coral reefs, seaweeds, sponge grounds, seagrasses, oyster banks, cold water corals are some examples of this vast set of ecosystems dispersed all over the world. During the last two decades, the concept of Blue Carbon has been consolidated, describing the stocked carbon in vegetated coastal and marine habitats such as mangroves, salt marshes, seagrasses and seaweeds. There are also world-wide numbers about how much carbon is retained in the terrestrial forests, crops and soils. These systems act as carbon immobilizers from which we have proxies. Can we design and apply an ambitious shallow and deep marine forest restoration plan to help climate change mitigation? The aim of thispaper is developing a simplified realistic calculation of the role as carbon immobilizers of a restored marine forests in one area as a case study, setting up a huge restoration plan to help mitigating climate change, enhancing carbon retention. A shallow (10-30 meters depth) restoration plan of the marine animal forests with new technologies based on symbiotic artificial reefs, enhancing the role as carbon immobilizers and creating a protocol to help the climate change mitigation, is explained, using realistic numbers to calculate the real impact of such regenerative plan. Is time to have a much more applied and holistic view of what is in the ocean’s floors in terms of habitat composition, complexity and biomass stocks, implementing new methods and technologies that are already in our hands. It is also time to give a chance to the oceans in helping in the climate change mitigation plans applying brave new restoration approaches that may change our relation with the sea.
 Keywords: marine restoration, marine animal forests, artificial reefs, transplantation,forest ecology.

Seasonal trends of the polyp expansion and nutritional condition of Alcyonium acaule (Octocorallia, Alcyonacea).

The ecological physiology of anthozoans, as well as their resistance to stressors, are strongly influenced by environmental factors and the availability of resources. The energy budget of anthozoans can vary seasonally in order to find an equilibrium between the available resources and respiration, polyp activity, growth, and reproduction processes. The variation in the biochemical composition of the animal tissues in these organisms results from a combination of the productivity processes of the water column coupled with the reproductive effort and potential starvation periods of the anthozoans. Here, the seasonal variation in the polyp activity of a slow-growing passive suspension feeder, the octocoral Alcyonium acaule, as well as their carbohydrate, protein and lipid contents, was investigated in a warm temperate environment using in-situ observations and biochemical analyses. Polyp activity exhibited a significant variability that was moderately dependent on season, while an aestivation phenomenon in A. acaule (i.e., a resting period in which the anthozoan is not capable of any polyp activity) during the warmer months is clearly observed. Carbohydrate concentrations in the coral species showed a significant increase in the late winter and spring seasons, and the lipid content increased during the spring. A higher abundance of lipids and carbohydrates coincided with a higher primary productivity in the water column, as well as with the octocoral reproduction period. In late autumn, there was a depletion of these biomolecules, with protein levels exhibiting great variability across sampling times. Complex alterations driven by climate change could affect the energy fluxes that depend on the dead or alive particles that are intercepted by marine animal forests. The obtained findings show a food shortage in late summer and autumn of the benthic suspension feeder A. acaule through the integrative descriptors of the ecophysiology of these anthozoans. This research contributes to the knowledge of energy storage capabilities in benthic suspension feeders in general, highlighting the importance of understanding the limits of resistance to starvation periods through these indicators.

The Importance of Food Pulses in Benthic-Pelagic Coupling Processes of Passive Suspension Feeders

Benthic-pelagic coupling processes and the quantity of carbon transferred from the water column to the benthic suspension feeders need multiple intensive sampling approaches where several environmental variables and benthos performance are quantified. Here, activity, dietary composition, and capture rates of three Mediterranean gorgonians (Paramuricea clavata, Eunicella singularis, and Leptogorgia sarmentosa) were assessed in an intensive cycle considering different variables such as the seston concentration and quality (e.g., carbon, nitrogen, and zooplankton), the colony branch patterns, and the energetic input of the single species (i.e., mixotrophic and heterotrophic). The three species showed clear differences in their impact on the seston concentration. Paramuricea clavata, the most densely distributed, showed a greater impact on the near bottom water column seston. The lowest impact of E. singularis on the seston could be explained by its mixotrophy and colony branching pattern. Leptogorgia sarmentosa had a similar impact as E. singularis, having a much more complex branching pattern and more than an order of magnitude smaller number of colonies per meter square than the other two octocorals. The amount of carbon ingested in the peaks of the capture rates in the three species may cover a non-neglectable proportion of the potential carbon fluxes.

Corrigendum: Ocean Circulation Over North Atlantic Underwater Features in the Path of the Mediterranean Outflow Water: The Ormonde and Formigas Seamounts, and the Gazul Mud Volcano

Seamounts constitute an obstacle to the ocean circulation, modifying it. As a result, a variety of hydrodynamical processes and phenomena may take place over seamounts, among others, flow intensification, current deflection, upwelling, Taylor caps and internal waves. These oceanographic effects may turn seamounts into very productive ecosystems with high species diversity, and in some cases, are densely populated by benthic organisms, such corals, gorgonians and sponges. In this study, we describe the oceanographic conditions over seamounts and other underwater features in the path of the Mediterranean Outflow Water (MOW), where populations of benthic suspensions feeders have been observed. Using CTD, LADPC and biochemical measurements carried out in the Ormonde and Formigas seamounts and the Gazul mud volcano (Northeast Atlantic), we show that Taylor caps were not observed in any of the sampled features. However, we point out that the relatively high values of the Brunt-Vaisala frequency in the MOW halocline, in conjunction with the slope of the seamount flanks, set up conditions for the breakout of internal waves and amplification of the currents. This may enhance the vertical mixing, resuspending the organic material deposited on the seafloor and, therefore, increasing the food availability for the communities dominated by benthic suspension feeders. Thus, we hypothesize that internal waves could be improving the conditions for benthic suspension feeders to grow on the slope of seamounts.

Pentaradial eukaryote suggests expansion of suspension feeding in White Sea-aged Ediacaran communities

Suspension feeding is a key ecological strategy in modern oceans that provides a link between pelagic and benthic systems. Establishing when suspension feeding first became widespread is thus a crucial research area in ecology and evolution, with implications for understanding the origins of the modern marine biosphere. Here, we use three-dimensional modelling and computational fluid dynamics to establish the feeding mode of the enigmatic Ediacaran pentaradial eukaryote Arkarua. Through comparisons with two Cambrian echinoderms, Cambraster and Stromatocystites, we show that flow patterns around Arkarua strongly support its interpretation as a passive suspension feeder. Arkarua is added to the growing number of Ediacaran benthic suspension feeders, suggesting that the energy link between pelagic and benthic ecosystems was likely expanding in the White Sea assemblage (~ 558–550 Ma). The advent of widespread suspension feeding could therefore have played an important role in the subsequent waves of ecological innovation and escalation that culminated with the Cambrian explosion.

Online tool to integrate evidence-based knowledge into cumulative effects assessments: Linking human pressures to multiple nature assets

Intensification and diversification of human-induced pressures in marine ecosystems have raised concerns over several sustainability-diminishing consequences, such as hypoxia and overexploitation of resources. We present the PlanWise4Blue tool (PW4B), which assesses the cumulative effects of multiple pressures on nature assets. In order to express the sensitivity of different nature assets to a plethora of pressure combinations, a meta-analysis based on published literature and available datasets was performed to calculate a set of standardized effect sizes. These calculations relied mostly on experimental or observational evidence; expert knowledge was used to estimate the impact coefficients only in the absence of impact data. Spatial modelling techniques (machine learning) were used to model the probability of occurrence and abundances of different nature assets in lattice grids with a cell size of 1 km2. Users can use the portal to estimate impacted areas and changes to natural assets caused by any combination of anthropogenic pressure. The PW4B tool can be used to predict individual and synergistic effects — both current and future — of a wide range of human activities and can be used regardless of scientific background. The tool was tested in the Baltic Sea region in coordination with the process of the Estonian Maritime Spatial Planning. This test evaluated the combined effects of human activity such as fisheries, aquaculture, wind energy, mining and maritime transport sectors on nature assets such as selected seaweed, invertebrate, fish habitats as well as bird and mammal species. The analyses showed that current Estonian maritime spatial planning will result in a moderate loss of some nature assets and a significant gain of benthic suspension feeders, although predicted losses in wind park areas can be mitigated if novel aquaculture activities such as mussel or macroalgal farming are established This test demonstrates how the PW4B tool can be used by planners to minimize adverse environmental effects, to suggest effective mitigation strategy, and to attain sustainable planning solutions.

Feeding biology of a habitat-forming antipatharian in the Azores Archipelago

Benthic suspension feeders have developed a variety of feeding strategies and food availability has often proven to be a key factor explaining their occurrence and distribution. The feeding biology of coral species has been the target of an increasing number of studies, however most of them focus on Scleractinia and Octocorallia, while information for Antipatharia is very scarce. The present study focused on Antipathella wollastoni, a common habitat-forming antipatharian in the Azores Archipelago, forming dense black coral forests between 20 and 150 m. The objective of the study was to investigate the food preferences of the target species upon availability of different isotopically enriched food substrates and determine its ability to capture zooplankton prey under different flow speeds. The species was able to utilize different food sources including live phytoplankton, live zooplankton and dissolved organic matter (DOM), indicating the ability to exploit seasonally available food sources. However, ingestion of zooplankton enhanced carbon (C) and nitrogen (N) incorporation in coral tissue and metabolic activity, highlighting the importance of zooplankton prey for vital physiological processes such as growth and reproduction. Maximum zooplankton capture rates occurred under 4 cm−1, however the species displayed high capacity to capture zooplankton prey over different flow rates highlighting the ability of A. wollastoni to exploit high quantities of shortly available prey.

Macrophyte-derived detritus in shallow coastal waters contributes to suspended particulate organic matter and increases growth rates of Mytilus edulis

Benthic suspension feeders, such as bivalves, potentially have several different food sources, including plankton and resuspended detritus of benthic origin. We hypothesised that suspension feeders are likely to feed on detritus if it is present. This inference would be further strengthened if there was a correlation between δ13C of suspension feeder tissue and δ13C of particulate organic matter (POM). Since detritus is characterised by high particulate organic matter (POC):chl a ratios, we would also predict a positive correlation between POM δ13C and POC:chl a. We hypothesised that increasing depth and greater distance from shore would produce a greater nutritional reliance by experimentally transplanted blue mussels Mytilus edulis on plankton rather than macrophyte-derived detritus. After deployments of 3 mo duration in 2 different years at depths from 3 to 40 m, M. edulis sizes were positively correlated with POM concentrations. POC:chl a ratios and δ13C of POM and M. edulis gill tissue decreased with increasing depth (and greater distance from shore). δ13C of POM was correlated with δ13C of M. edulis. Our results suggest that detritus comprised a large proportion of POM at shallow depths (<15 m), that M. edulis ingested and assimilated carbon in proportion to its availability in POM, and that growth of M. edulis was higher where detritus was present and POM concentrations were higher.

Suspension feeders as natural sentinels of the spatial variability in food sources in an Antarctic fjord: A stable isotope approach

• δ 13 C and δ 15 N signatures of benthic suspension feeders differed across Potter Cove. • Food sources presented obvious small-scale spatial heterogeneity across Potter Cove. • Mixing models showed different contributions of food sources across Potter Cove. • Glacial melt-related environmental conditions govern the spatial heterogeneity of food sources. We examined the effect of glacial melt-related retreat environmental conditions on the spatial heterogeneity of food sources for Antarctic nearshore marine benthic communities of Potter Cove, a representative fjord on King George Island on the West Antarctic Peninsula. Focusing on Antarctic suspension feeders, we surveyed the variation of carbon (δ 13 C) and nitrogen (δ 15 N) stable isotopes in three different stations with contrasting characteristics in terms of glacier-sedimentary regimes and distance from the glacier. Bayesian mixing models were used to estimate the relative contribution of eight potential food sources at the study sites and to the consumers' diet. The isotopically signatures of suspension feeders displayed a broad range of assimilate available food sources with distinct contributions at each site. Overall, for most of the suspension feeders analysed, contributions of suspended particulate matter and macroalgae detritus tended to prevail over the rest of the potential food sources. Additionally, we confirm the assimilation of krill faeces by benthic organisms reinforcing its relevance as food source in nearshore Antarctic ecosystems. Mixing models corroborated the influence of glacier discharge on the spatial distribution of available food sources, since their contribution in the suspension feeders diet was different and more heterogeneous in the internal stations (ice-proximal zone) than in the external one (ice-distal zone). The analysis of isotopic signatures of primary benthic consumers (suspension feeders) indicated the spatial heterogeneity of food sources and its composition in coastal Antarctic nearshore, as consequence of the glacial influence on the local environment and hydrology.

Responses of a common New Zealand coastal sponge to elevated suspended sediments: Indications of resilience

Suspended sediments can affect the health of marine benthic suspension feeders, with concomitant effects on community diversity, abundance and ecosystem function. Suspended sediment loads can become elevated through trawling and dredging, and via resuspension of bottom sediments and/or direct input from land during storms. We assessed the functioning (survival, respiration, morphology) of a common New Zealand cushion sponge, Crella incrustans (Carter, 1885), during four weeks of exposure to a gradient of suspended sediment concentrations (SSC). Survival was high, and oxygen consumption was not affected. Sponges did, however, develop apical fistules, a phenomenon never-before observed in this species. Although sediments accumulated internally within the sponges, around a third had cleared these sediments two weeks after the elevated SSCs were removed. The environments these sponges inhabit may predispose them to coping with high SSCs. Such experiments are useful for defining SSC tolerances, which may influence how such impacts can be managed.

Ocean Circulation Over North Atlantic Underwater Features in the Path of the Mediterranean Outflow Water: The Ormonde and Formigas Seamounts, and the Gazul Mud Volcano

Seamounts constitute an obstacle to the ocean circulation, modifying it. As a result, a variety of hydrodynamical processes and phenomena may take place over seamounts, among others, flow intensification, current deflection, upwelling, Taylor caps, and internal waves. These oceanographic effects may turn seamounts into very productive ecosystems with high species diversity, and in some cases, are densely populated by benthic organisms, such corals, gorgonians, and sponges. In this study, we describe the oceanographic conditions over seamounts and other underwater features in the path of the Mediterranean Outflow Water (MOW), where populations of benthic suspensions feeders have been observed. Using CTD, LADPC and biochemical measurements carried out in the Ormonde and Formigas seamounts and the Gazul mud volcano (Northeast Atlantic), we show that Taylor caps were not observed in any of the sampled features. However, we point out that the relatively high values of the Brunt–Väisälä frequency in the MOW halocline, in conjunction with the slope of the seamount flanks, set up conditions for the breakout of internal waves and amplification of the currents. This may enhance the vertical mixing, resuspending the organic material deposited on the seafloor and, therefore, increasing the food availability for the communities dominated by benthic suspension feeders. Thus, we hypothesize that internal waves could be improving the conditions for benthic suspension feeders to grow on the slope of seamounts.

New Records of Two Non-native Clam Species (Bivalvia: Cardiidae) from the Coastal Waters of Bangladesh

Benthic suspension feeders, such as many marine bivalve molluscs, influence the nutrient and organic cycles of benthic and pelagic systems through their ability to filter a wide size range of particles and deposit organic matters that sink to the bottom. They also play important roles in coastal and marine ecosystems by filtering the water and serving as habitat and prey for a variety of sea life. Due to the increasing trends of environmental contaminations in recent years, many bivalves have been using as a potential biomarker for assessing the worse environment. Moreover, the shell of a bivalve is comprised of calcium carbonate, which may support thousands of calciferous organisms into the water body. Mostly, bivalves inhabit the tropics, as well as temperate and boreal waters, and they can survive and even flourish in extreme environmental conditions like Bangladesh. Nowadays, many bivalve molluscs have been identified as a superior source of bioactive compounds and are using for pharmaceutical and nutraceutical purposes as well as other applications. However, until now, few systematic studies on marine bivalve molluscs have been conducted through which a total of 437 marine and brackish water species were identified and recorded in Bangladesh. But still, our knowledge of taxonomy and systematic on marine molluscs are primitive in the context of the country. Here we report two new species of bivalve molluscs, Parvicardium exiguum and Trachycardium procerum belonging to the family Cardiidae, from the Kutubdia Island of Bangladesh. The study added these two bivalve species, which has not been recorded from the coastal zone of Kutubdia Island during the previous studies. To sum up, studies and survey on taxonomy and systematics in marine bivalves will provide new dimensions for further research about these important marine invertebrates.

Phenotypic Plasticity or a Reproductive Dead End? Primnoa pacifica (Cnidaria: Alcyonacea) in the Southeastern Alaska Region

Red tree corals (Primnoa pacifica) are abundant in the eastern Gulf of Alaska, from the glacial fjords of Southeast Alaska where they emerge to as shallow as 6 m, to the continental shelf edge and seamounts where they are more commonly found at depths greater than 150 m. This keystone species forms large thickets, creating habitat for many associated species, including economically valuable fishes and crabs, and so are important benthic suspension feeders in this region. Though the reproductive periodicity over 1.5 year period was reported in 2014 from a shallow fjord (Tracy Arm), this study examined reproductive ecologies from 8 sites – two within Glacier Bay National Park and Preserve, three on the continental shelf edge, one within Endicott Arm (Holkham Bay) and two time points from the Tracy Arm (Holkham Bay) study. Male reproductive traits were similar at all sites but there were distinct differences in oogenesis. Though fecundity mostly showed no significant difference between sites, there was a trend of increasing number of eggs with depth. Indeed, the average oocyte sizes from Tracy Arm (the shallowest site) was 105 m, whereas from Shutter Ridge (one of the deepest sites) the average size was 309 m. Moreover, the maximum oocyte size at Tracy Arm was 802 m, whereas it was 2120 m at Dixon Entrance, an almost 3-fold difference, and one not usually observed within a single species. We propose two theories to explain the observed differences, a) this species shows great phenotypic plasticity in reproductive ecology, adjusting to different environmental variables based on energetic need and potentially demonstrating micro-evolution; or b) the fjord sites are at a reproductive dead end, with the stress of shallow water conditions effectively preventing gametogenesis reaching full potential and likely limiting successful reproductive events from occurring, at least on a regular basis.

The importance of coastal gorgonians in the blue carbon budget

Terrestrial (trees, shrubs) and marine (seaweeds and seagrasses) organisms act as carbon (C) sinks, but the role of benthic suspension feeders in this regard has been largely neglected so far. Gorgonians are one of the most conspicuous inhabitants of marine animal forests (mainly composed of sessile filter feeders); their seston capture rates influence benthic-pelagic coupling processes and they act as C sinks immobilizing carbon in their long-living structures. Three gorgonian species (Paramuricea clavata, Eunicella singularis and Leptogorgia sarmentosa) were studied coupling data of population size structure, biomass and spatial distribution in a NW Mediterranean area (Cap de Creus, Spain) with feeding, respiration and growth rates. In the study area, we calculated that P. clavata sequestered 0.73 ± 0.71 g C m−2 year−1, E. singularis 0.73 ± 0.89 g C m−2 year−1 and L. sarmentosa 0.03 ± 0.02 g C m−2 year−1. To our knowledge, this is the first attempt to calculate the importance as C sinks of gorgonian species that we consider as a starting point to estimate the importance of marine animal forests in C sequestration, and to ensure appropriate management and protection especially in areas and at depths where they are concentrated.

Impact of excessive sedimentation caused by anthropogenic activities on benthic suspension feeders in the Sea of Marmara

AbstractA massive die-off of benthic suspension feeders (BSF) covered by large amounts of sediments was observed along Prince Islands coasts (north-eastern Sea of Marmara) in August 2015. Alcyonarians, pennatulaceans, bivalves and sponges were severely affected. Many BSF probably died from burial and clogging of their feeding and respiratory apparatus. Of the gorgonian colonies, 66 ± 34% (mean ± SD) were dead, while 15 ± 16% (mean ± SD) displayed recent necrosis on the colony surface. In addition, histopathological and microbial examinations of the affected gorgonians and gold corals (Savalia savaglia) suggest that stress caused by sedimentation made them vulnerable to exploitation by consistently isolated opportunistic microorganisms. We isolatedVibrio splendidusandVibrio neptuniusfrom diseased gold coral colonies, but the bacterial isolates obtained from gorgonians could only be identified to genusVibriolevel. The presumably artificially introduced fungusMucor circinelloideswas common on both gold coral and gorgonians. This mould and opportunistic bacteria may have colonized BSF by taking advantage of low oxygen levels leading to impaired coral immune responses and thereby exacerbated the BSF mortality. Construction and landfill operations at Yassıada seem to be the greatest contributor to the observed sedimentation, as shown by silicate concentrations in nearby waters. These observations imply that preventive measures are necessary when construction operations take place in the vicinity of sensitive marine habitats.

Oases of biodiversity: Early Devonian palaeoecology at Hamar Laghdad, Morocco

The mudmound locality of Hamar Laghdad (Tafilalt Platform) contains possibly the greatest palaeobiodiversity, both horizontally in the surrounding sediments and stratigraphically through the Devonian sedimentary succession of the Moroccan eastern Anti-Atlas. From the Ordovician to the Devonian, sediments of the Hamar Laghdad region and their fossil contents tend to differ slightly from those in time-equivalent strata of other parts of the Tafilalt Platform. Our research provides a description of the sedimentological and palaeontological record at Hamar Laghdad covering the Lochkovian to Givetian interval. We use alpha-diversity data based on macrofossils from selected fossiliferous strata and compare the results with the relative abundance of bioclasts in polished slabs. We show that the palaeobiodiversity at Hamar Laghdad was similar to that of the southern Tafilalt with a normal diversity during the Pragian, i.e.prior to mudmound initiation and growth. By contrast, the layers covering the mudmound carbonates (i.e.when their activity had ceased) show a high diversity during the latest Emsian with a trophic nucleus comprising 36 species. This fauna, here exemplified by the 'Red Fauna' (from the Red Cliff), is dominated by benthic suspension feeders (corals, brachiopods and crinoids) and cephalopods. The shift in biodiversity is most likely related to the local occurrence of a favourable environmental setting, characterized by a temporally and spatially varying topography. It is assumed that this setting was influenced by sea-level fluctuations, currents and nutrient availability.