Trajectories of trace element accumulation in seagrass (Posidonia oceanica) over a decade reveal the footprint of fish farming.

To evaluate the effect of trace element (TE) release from fish farms on seagrass Posidonia oceanica, we compared TE concentrations (As, Cd, Co, Cu, Mn, Mo, Ni, Pb, V, Zn) in shoots near fish cages (Station 'Cage') with those away from them (Station 'Control') in two fish farm facilities (Site 1 and Site 2, North Aegean Sea, Greece). We assessed the present (i.e.

Transcriptomic Responses of a Lightly Calcified Echinoderm to Experimental Seawater Acidification and Warming during Early Development.

Ocean acidification (OA) and ocean warming (OW) are potential obstacles to the survival and growth of marine organisms, particularly those that rely on calcification. This study investigated the single and joint effects of OA and OW on sea cucumber larvae raised under combinations of two temperatures (19 °C or 22 °C) and two CO levels (400 or 1000 μatm) that reflect the current and end-of-21st-century projected ocean scenarios. The investigation focused on assessing larval development and identifying differences in gene expression patterns at four crucial embryo-larval stages (blastula, gastrula, auricularia, and doliolaria) of sea cucumbers, using RNA-seq.

Holothurians play an important role in mitigating the impacts of aquaculture on sediment conditions.

As deposit feeders contribute to bioremediation and nutrient recycling in sediments, positively impacting water and sediment quality, holothurians are candidate organisms for multitrophic aquaculture. This study aimed to investigate the potential of Holothuria poli to reduce the environmental footprint of fish farms through a benthocosm experiment. The experimental setup included four benthocosms with holothurians(H+) and four without (H-).

Contribution of holothuroids to the bioremediation and stimulation of the benthic microbial metabolism in aquaculture.

The implementation of sustainable system designs in aquaculture comprises the biological treatment of pollutants. In order to test the potential of Holothuria (Roweothuria) poli as a candidate for bioremediation of aquaculture wastes, the effect of this species on the benthic microbial activity was studied. Two experimental treatments, with and without holothuroids, were allocated in two benthocosms, each one containing four replicate tanks with undisturbed sediment and a volume of water above it.

Metals in tissues of marine fish from the Thermaikos Gulf, Eastern Mediterranean Sea: Detection of changes with trophic level.

Concentrations of 27 metals and elements were investigated in the tissues of 28 demersal and pelagic marine fish species from the Eastern Mediterranean Sea. The analysis indicated highest concentrations of accumulation for the majority of elements in the gills, liver, and scales; whereas, lowest assimilation of elements was reported in the muscle. Pelagic fish accumulated higher concentrations of elements than demersal fish.

Viral Metagenomic Content Reflects Seawater Ecological Quality in the Coastal Zone.

Viruses interfere with their host's metabolism through the expression of auxiliary metabolic genes (AMGs) that, until now, are mostly studied under large physicochemical gradients. Here, we focus on coastal marine ecosystems and we sequence the viral metagenome (virome) of samples with discrete levels of human-driven disturbances. We aim to describe the relevance of viromics with respect to ecological quality status, defined by the classic seawater trophic index (TRIX).

Assessing large-scale macrobenthic community shifts in the Aegean Sea using novel beta diversity modelling methods. Ramifications on environmental assessment.

The effects of large-scale environmental gradients on the spatial patterns of macrobenthic communities used in marine health assessment were evaluated using beta diversity methods. In this work, beta diversity partitioning and relevant ecological modelling methods revealed clear patterns between the northern and the southern parts of the Aegean Sea (Greece). A community turnover point was observed in the Evoikos Gulf marking the transition between the northern and the southern communities.

Prokaryotic and eukaryotic microbial community responses to N and P nutrient addition in oligotrophic Mediterranean coastal waters: Novel insights from DNA metabarcoding and network analysis.

The effects of the abrupt input of high quantities of dissolved inorganic nitrogen and phosphorus on prokaryotic and eukaryotic microbial plankton were investigated in an attempt to simulate the nutrient disturbances caused by eutrophication and climate change. Two nutrient levels were created through the addition of different quantities of dissolved nutrients in a mesocosm experiment. During the developed blooms, compositional differences were found within bacteria and microbial eukaryotes, and communities progressed towards species of faster metabolisms.

Modelling the effects of climate change on the distribution of benthic indicator species in the Eastern Mediterranean Sea.

The potential effects of climate change on the distribution of benthic species commonly used in marine ecological quality assessment were investigated using a spatial modelling approach. In this work, the relevance of the ecological groups that macrofaunal molluscs are assigned according to their sensitivity or tolerance to environmental disturbance was examined under the scope of the RCP 8.5 severe emissions scenario.

Can intensive fish farming for 20 years induce changes in benthic ecosystems on a scale of waterbody? An assessment from Cephalonia bay (Ionian Sea).

The environmental impacts of fish farming on benthic ecosystems beneath the fish cages have been widely addressed the past decades. However, the chronic release of nutrients can cause a shift in local primary productivity and a chronic increase in the sedimentation of organic material at a large spatial scale which could be reflected in benthic ecosystems. In this context, the indirect effects of aquaculture on the benthic ecosystem were studied in a semi-closed bay (Cephalonia, Ionian Sea) where a relatively large fish farm has been operating since 1982.

Molluscan indicator species and their potential use in ecological status assessment using species distribution modeling.

Marine habitat assessment using indicator species through Species Distribution Modeling (SDM) was investigated. The bivalves: Corbula gibba and Flexopecten hyalinus were the indicator species characterizing disturbed and undisturbed areas respectively in terms of chlorophyll a concentration in Greece. The habitat suitability maps of these species reflected the overall ecological status of the area.

Species-specific response to sulfide intrusion in native and exotic Mediterranean seagrasses under stress.

We explored the sulfur dynamics and the relationships between sediment sulfur and nutrient pools, seagrass structural and physiological variables and sulfide intrusion in native (Posidonia oceanica, Cymodocea nodosa) and exotic (Halophila stipulacea) Mediterranean seagrasses at six sites affected by cumulative anthropogenic pressures to understand the factors controlling sulfide intrusion in seagrass. Sensitive indicators of seagrass stress (leaf TN, δN, TS, F) were increased at several sites, implying that seagrasses are under pressure. Sulfide intrusion was not related to sediment TOC but it was negatively related to shoot size and below-ground biomass.

Benthic pelagic coupling in a mesocosm experiment: Delayed sediment responses and regime shifts.

A mesocosm experiment was performed to study benthic-pelagic coupling under a eutrophication gradient. Nine mesocosms were deployed in the facilities of the Hellenic Center for Marine Research in Crete, in the Eastern Mediterranean. The mesocosms were 4m deep, containing 1.

Long-term (1998-2010) large-scale comparison of the ecological quality status of gulf of lions (NW Mediterranean) benthic habitats.

A comprehensive Mediterranean data set has been used to address 3 questions associated with the use of sensitivity/tolerance based biotic indices to infer the Ecological Quality status (EcoQs) of benthic habitats. Our results showed: (1) a significant effect of the reference database on derived sensitivity/tolerance measure (ES500.05) as well as associated Benthic Quality Index values and derived EcoQs; (2) a lack of correlation neither between BQI and AZTI Marine Biotic Index values nor between BQI and Multivariate-AZTI Marine Biotic Index values; (3) a lack of correlation between the values of the Benthic Habitat Quality Index (index derived from Sediment Profile Imagery) and those of either of the 3 tested biotic indices; and (4) a general agreement between the 3 tested biotic indices in describing the lack of global trend for the EcoQs of the Gulf of Lions despite the occurrence of significant changes in benthic macrofauna composition between 1998 and 2010.

One Step forward: Benthic Pelagic Coupling and Indicators for Environmental Status.

A large data set from the Eastern Mediterranean was analyzed to explore the relationship between seawater column variables and benthic community status. Our results showed a strong quantitative link between the seawater column variables (Chlorophyll a and Eutrophication Index) and various indicators describing benthic diversity and community composition. The percentage of benthic opportunistic species increased significantly in the stations with high trophic status of the seawater column and so did the strength of the coupling between values of seawater column and benthic indicators.

Mussel farming in Maliakos Gulf and quality indicators of the marine environment: Good benthic below poor pelagic ecological status.

Biological and geochemical variables in the water column and sediments were monitored along a transect of a mussel farm located in a transitional environment in Maliakos Gulf, a semi-enclosed gulf in eastern Mediterranean. Analyses of water, sediment and macrofauna samples were used to calculate ecological status indicators in the context of the European Water Framework Directive. The water column ecological status was "Poor" or "Bad" showing little change with distance from the farm, but the ecological status of the benthic communities was found to be "Good," although there were quantitative changes in macrofaunal indices with distance from the farm.

The pattern of change in the abundances of specific bacterioplankton groups is consistent across different nutrient-enriched habitats in Crete.

A common source of disturbance for coastal aquatic habitats is nutrient enrichment through anthropogenic activities. Although the water column bacterioplankton communities in these environments have been characterized in some cases, changes in α-diversity and/or the abundances of specific taxonomic groups across enriched habitats remain unclear. Here, we investigated the bacterial community changes at three different nutrient-enriched and adjacent undisturbed habitats along the north coast of Crete, Greece: a fish farm, a closed bay within a town with low water renewal rates, and a city port where the level of nutrient enrichment and the trophic status of the habitat were different.

Metals and other elements in tissues of wild fish from fish farms and comparison with farmed species in sites with oxic and anoxic sediments.

Farmed fish and wild fish aggregating in the vicinity of four Mediterranean fish farms with different environmental conditions were sampled. Levels of metals (including As and Se) were measured in the muscle, liver, gills, bone and intestine. The wild fish from sites with anoxic substrata accumulate metals (including As and Se) from the ambient habitat in their gills whereas those from sites with oxic substrata concentrate these elements through their diet in their intestine.

PAHs and n-alkanes in Mediterranean coastal marine sediments: aquaculture as a significant point source.

The occurrence of polycyclic aromatic and aliphatic hydrocarbons in fish feed, sediment trap material and marine sediments was examined at two fish farms in the eastern Mediterranean. The average (min-max) concentrations of polycyclic aromatic hydrocarbons (PAHs) in fish feed and particulate effluents were 316 (287-351) ng g(-1) DW and 487 (475-499) ng g(-1) DW, respectively. Lower PAH levels were determined in the underlying marine sediments.

Effects of fish farming on the biological and geochemical properties of muddy and sandy sediments in the Mediterranean Sea.

The aim of this paper was to test how benthic fauna and biogeochemical properties of sediment will vary in response to similar levels of organic enrichment (induced by fish farming) as a function of bottom-habitat type (i.e., mud versus seagrass/coarse sediments), distance from the enrichment source and depth.

Assessing coastal benthic macrofauna community condition using best professional judgement--developing consensus across North America and Europe.

Benthic indices are typically developed independently by habitat, making their incorporation into large geographic scale assessments potentially problematic because of scaling inequities. A potential solution is to establish common scaling using expert best professional judgment (BPJ). To test if experts from different geographies agree on condition assessment, sixteen experts from four regions in USA and Europe were provided species-abundance data for twelve sites per region.

Effects of fish farm waste on Posidonia oceanica meadows: synthesis and provision of monitoring and management tools.

This paper provides a synthesis of the EU project MedVeg addressing the fate of nutrients released from fish farming in the Mediterranean with particular focus on the endemic seagrass Posidonia oceanica habitat. The objectives were to identify the main drivers of seagrass decline linked to fish farming and to provide sensitive indicators of environmental change, which can be used for monitoring purposes. The sedimentation of waste particles in the farm vicinities emerges as the main driver of benthic deterioration, such as accumulation of organic matter, sediment anoxia as well as seagrass decline.

Benthic input rates predict seagrass (Posidonia oceanica) fish farm-induced decline.

Fish farms represent a growing source of anthropogenic disturbance to benthic communities, and efficient predictors of such impacts are urgently needed. We explored the effects of fish farm benthic organic and nutrient inputs on the population dynamics of a key seagrass species (Posidonia oceanica) in four Mediterranean deep meadows adjacent to sea bream and sea bass farms. We performed two annual plant censuses on permanent plots at increasing distance from farms and measured benthic sedimentation rates around plots.

Benthic impacts of fish farming: meta-analysis of community and geochemical data.

A number of 41 papers dealing with the benthic effects of fish farming were reviewed and the values of the variables studied were extracted to be used in a meta-analysis of effects. The papers used covered a wide range of farmed species, geographic regions, management practices and specific site characteristics (e.g.

Cost/benefit analysis of a benthic monitoring programme of organic benthic enrichment using different sampling and analysis methods.

To investigate the combined effects of decreasing taxonomic resolution (i.e. species, family, phylum), the use of different mesh-size (1.