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. The increased beta diversity in this work was due to species replacement driven mainly by the latitudinal gradients of bottom temperature and salinity whereas species richness did not present substantial differences between the Aegean macrobenthic communities. These findings are attributed to the ability of beta diversity methods to detect the environmental filtering that occurs in these marine provinces through the assessment of biotic interactions in respect to geographic distance. We propose a new standpoint of using beta diversity measures for benthic environmental assessment on a large spatial scale and in marine areas characterised by environmental gradients.
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•Beta diversity metrics detect large-scale macrobenthic community shifts.•Species replacement is the main driver for the Aegean benthic community structure.•Novel modelling framework can detect macrobenthic community turnover.•Beta diversity provides a promising tool in large-scale environmental assessment.
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. It was anticipated that H. poli could affect the overall assimilative capacity of the aquaculture effluent system either through the consumption of particulate organic matter or through the stimulation of benthic microbial metabolism. Indeed, the results indicated that the microbial activity related to the mineralization of the N and C was significantly different between the treatments verifying our hypothesis that deposit-feeders that move above or inside the sediment matrix can accelerate the depletion of organic matter through bioturbation.
•Holothuria poli as a candidate for bioremediation of aquaculture wastes was studied.•H. poli altered the quantity and composition of sedimentary organic matter.•H. poli reduced the environmental footprint of aquaculture.•H. poli is capable to promote sustainability in multitrophic aquaculture.
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-). The 58-day experiment included two phases: constant organic enrichment and recovery. In order to simulate the organic enrichment sediment conditions under a typical fish farm, a mixture of fish feces and fish feed pellets was added. Results showed that holothurians effectively reduced organic matter and H
S and increased redox, RPD depth and sediment oxygenation, thereby preventing anoxic conditions. Also, during the recovery phase, holothurians facilitated rapid sediment recovery, while the sediments without holothurians remained organic-enriched until the end of the experiment. The study emphasizes the significance of holothurians in mitigating the impacts of aquaculture on sediment conditions and so promoting environmental sustainability.
In a changing environment, it is important to understand the contribution of faunal and microbial communities to ecosystem functioning. In this context, the present study aimed to explore the effect ...of organic matter inputs due to aquaculture on the interaction between microphytobenthos and macrofaunal traits related to bioturbation. The study was conducted in the vicinity of a fish farm in a semi-enclosed bay in Cephalonia (Eastern Mediterranean). Two different disturbance zones were compared – a control area and an area close to fish cages and, more specifically, at the edge of the Allowable Zone of Effect (AZE) subject to intermediate stress from aquaculture waste discharge. Bioturbation potential was the main driver shaping microphytobenthic community composition. While Euglenophytes prevailed in the benthic communities close to fish farms, Cyanobacteria were more abundant in the control area, indicating a shift from a microbially driven functioning to a more macrofaunal one near fish cages. Indeed, a shift from suspension feeding to predation and scavenging was recorded close to fish cages. This shift was caused by the interaction of different trophic groups, food availability, as well as the interference of the increased bioturbation in suspension feeding near fish cages. High bioturbation and bioirrigation potentials recorded near fish cages probably acted as moderators of the negative effects of organic matter deposition caused by fish farming. In conclusion, the benthic community close to fish cages was more diverse in terms of biological traits than at the control sites. This indicated the co-existence of species with different ecological strategies near fish cages.
•Species traits were studied at two disturbance zones.•A microbially driven functioning prevailed in the low organic matter area.•Large predators and grazers attracted by the rich-in-food community at AZE.•Bioturbation was the main factor shaping microphytobenthos.
Will the Oceans Help Feed Humanity? Duarte, Carlos M; Holmer, Marianne; Olsen, Yngvar ...
Bioscience,
12/2009, Letnik:
59, Številka:
11
Journal Article
Recenzirano
Constraints on the availability of freshwater and land plants and animals to feed the 9.2 billion humans projected to inhabit Earth by 2050 can be overcome by enhancing the contribution the ocean ...makes to food production. Catches from ocean fisheries are unlikely to recover without adequate conservation measures, so the greater contribution of the oceans to feeding humanity must be derived largely from mariculture. For the effort to be successful, mariculture must close the production cycle to abandon its current dependence on fisheries catches; enhance the production of edible macroalgae and filter-feeder organisms; minimize environmental impacts; and increase integration with food production on land, transferring water-intensive components of the human diet (i.e., production of animal protein) to the ocean. Accommodating these changes will enable the oceans to become a major source of food, which we believe will constitute the next food revolution in human history.
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. Our results showed that samples from silty sediments in the vicinity of fish farms have higher TOC and TON values, higher oxygen consumption, higher PO
4 release and lower benthic diversity. In this context muddy sites are more likely to be identified as impacted/critical, than coarse sediment ones.
The Mediterranean is a miniature of the world with 22 countries sharing the its coastline. In the past few decades aquaculture production in Mediterranean showed an increasing trend but brought with ...it several environmental and socio-economic issues. In order to establish sustainable development, the Mediterranean aquaculture sector has adopted integrated management plans. Within this framework, our aim was to evaluate the state of the Mediterranean aquaculture industry with respect to sustainable growth, focusing mostly on the spatial scale. We used the evaluation framework for ICZM proposed by Billé (2007) that takes into consideration how multiple policies can be accountable for sustainable management practices. In order to identify the different management regimes and trends in the area, satellite images were processed as a diagnostic tool to locate and analyse the characteristics of the Mediterranean fish farms in cages over time. Google Earth historical images were used to map the characteristics of the Mediterranean fish farms in three different periods between 2006 and 2017. The average coastal surface occupied by the fish cages in the Mediterranean was 0.01%; only two countries currently exceed this percentage due to having a large number of cages (Turkey and Greece) and five others due to their limited coastline. In total, 15,499 cages were counted in recent years in the Mediterranean area, 46.5% of them belonging to larger cluster aggregations. Over time, square steel cages have been gradually replaced by larger and technically more advanced circular cages that significantly increased the finfish production rates. To understand the level of integration done by Mediterranean aquaculture we examined four dimensions of aquaculture issues: (i) policy and management; (ii) environment; (iii) economy - industry and (iv) social. State-of-the-art aquaculture policy and management systems were integrated in national legislations, boosting the production, ensuring at the same time better environmental quality from and for the aquaculture. Despite these positive results for the Mediterranean aquaculture industry, other factors, such as social issues related with the general bad image of aquaculture and the conflicts with local stakeholders, seem to inhibit the further development of aquaculture production. Thus, studies like this can identify factors that have favoured the expansion of aquaculture but also the evolving needs of the stakeholders in the context of changing market and social conditions.
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•An integrated coastal zone management (ICZM) evaluation methodology was used to examine the state of Mediterranean marine fish farms in cages towards sustainability.•Google Earth historical images were used to map the characteristics of the Mediterranean fish farms in three different periods between 2006 and 2017.•There are considerable differences between these time periods regarding the spatial and technical characteristics of the fish farming industry in the Mediterranean.•15,499 fish farm cages were counted, which occupy only 0.01% surface of the Mediterranean coastal belt.•The use of the evaluation tool showed that there is a high integration of sustainability principles in the Mediterranean fish farm management practices.
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. Even though changes in α-diversity were different at each site, we observed across the sites a common change pattern accounting for most of the community variation for five of the most abundant bacterial groups: a decrease in the abundance of the Pelagibacteraceae and SAR86 and an increase in the abundance of the Alteromonadaceae, Rhodobacteraceae, and Cryomorphaceae in the impacted sites. The abundances of the groups that increased and decreased in the impacted sites were significantly correlated (positively and negatively, respectively) with the total heterotrophic bacterial counts and the concentrations of dissolved organic carbon and/or dissolved nitrogen and chlorophyll α, indicating that the common change pattern was associated with nutrient enrichment. Our results provide an in situ indication concerning the association of specific bacterioplankton groups with nutrient enrichment. These groups could potentially be used as indicators for nutrient enrichment if the pattern is confirmed over a broader spatial and temporal scale by future studies.
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., 2021, year of sampling) and past (reconstructed period 2012–2020) accumulation of TEs using the living compartments (leaf blades, sheaths, rhizomes, roots, epiphytes) and the dead sheaths, respectively. We also assessed possible seagrass degradation by reconstructing past rhizome production.
P
.
oceanica rhizome
production at the ‘Cage’ stations was up to 50% lower than at the ‘Control’ stations. Most TE concentrations were higher at ‘Cage’ stations, but the differences often depended on the seagrass living compartment. Significant differentiation between ‘Cage’ and ‘Control’ stations was observed based on the TE concentrations of the dead sheaths during 2012–2020. The contamination level at the ‘Cage’ stations was mostly moderate in Site 1 and low in Site 2, during the reconstructed period, while an increasing contamination trend was found for certain potential phytotoxic TEs (As, Cu, Cd, Mo, V). Our results emphasize the need for the aquaculture industry to work towards a more ecologically aware approach.
As part of an EU funded 7th Framework project, Prevent Escape, a programme of research was undertaken to document the extent, size and knowledge of the causes of escapes from marine fin fish farms in ...Europe over a three year period. Escape incidents were identified and assessed through questionnaires across the 6 countries (Ireland, UK, Norway, Spain, Greece, and Malta), and other data supplied by the Norwegian Fisheries Directorate and the Scottish Aquaculture Research Forum. A total of 8,922,863 fish were reported to have escaped from 242 incidents. Of these over 5 million occurred in two catastrophic escape incidents. Sea bream accounted for the highest number of escapes at 76.7% followed by Atlantic salmon at 9.2%. Of the 113 Atlantic salmon escape events, almost 75% were due to structure failure or operational error. Almost 50% of cod escape incidents were due to biological causes e.g. biting of nets. The nominal costs of escapes as calculated by value at point of first sale were very substantial, estimated at approximately €47.5 million per annum on average over the study period. Of this €42.8 million was for annual cost of losses of sea bass and sea bream in the Mediterranean and €4.7 million for losses of salmon in northern Europe.
•The extent of fish farm escapes is described over a three year period across a range of offshore fish farming operations in the Atlantic and Mediterranean.•The causes of the escape events are identified and assessed.•The costs of the escape incidents to fin fish aquaculture are quantified in monetary terms for the first time.
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