Ioannis Karakassis

Will the Oceans Help Feed Humanity

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.

Natural vs. mariculture induced variability in nutrients and plankton in the eastern Mediterranean

The water column in three Mediterranean fish farms was investigated in terms of physical, chemical and biological characteristics. A significant increase in concentrations of phosphate and ammonium was detected within the cages over the control site in one of the farms but without any significant effect on chlorophyll concentration. Analysis of variation within the data set identified location and season as the major factors of variability in most of the variables examined except phosphate and ammonium for which variability induced by fish farming seemed to be of major importance. Plankton abundance for the major taxonomic groups (diatoms, flagellates, dinoflagellates and ciliates), microplankton species diversity and community structure were also determined by the effects of season and location rather than by fish farming.

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. The effects of fish farming on P. oceanica meadows are diverse and complex and detected through various metrics and indicators. A safety distance of 400 m is suggested for management of P. oceanica near fish farms followed by establishment of permanent seagrass plots revisited annually for monitoring the health of the meadows.

Evaluation of atmospheric transport as a nonpoint source of polycyclic aromatic hydrocarbons in marine sediments of the Eastern Mediterranean

Coastal marine sediment, air and seawater samples were collected at six sampling stations in the Eastern Mediterranean Sea distant from pollutant point sources. All sediment samples were analyzed to determine polycyclic aromatic hydrocarbon (PAH), black carbon (BC) and organic carbon (OC) contents. The PAH contents of gaseous and seawater samples of the study were determined in order to evaluate the role of air–sea exchange as PAH nonpoint source to the marine sediments. The average concentration of the total PAHs (∑PAHs) in the sediments varied from 2.2 to 1056.2 ng g−1 dry weight. The average BC and OC contents varied from 0.3 to 5.6 and from 2.9 to 21.4 mg g−1 dry weight, respectively. ∑PAH concentration in the marine atmosphere varied from 20.0 to 83.2 ng m−3. Air–water exchange flux (FA–W) estimation has indicated air transport as a significant source of PAHs to pristine marine sediments of Eastern Mediterranean. In addition, the significant correlation between the PAHs and the organic and soot carbon content further suggests the importance of atmospheric input of PAHs to the sediments.

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. They ranked samples from best to worst condition and classified samples into four condition (quality) categories. Site rankings were highly correlated among experts, regardless of whether they were assessing samples from their home region. There was also good agreement on condition category, though agreement was better for samples at extremes of the disturbance gradient. The absence of regional bias suggests that expert judgment is a viable means for establishing a uniform scale to calibrate indices consistently across geographic regions.

Aquaculture in the Ecosystem

Foreword Fish farm wastes in the ecosystem Paul Tett Monitoring of environmental impacts of marine aquaculture Marianne Holmer, Pia Kupka Hansen, Ioannis Karakassis, Joseph A Borgh and Patrick J Schembri Aquaculture and coastal space management in Europe: an ecological perspective Tim Dempster and Pablo Sanchez-Jerez Detrimental genetic effects of interactions between reared strains and wild populations of marine and anadromous fish and invertebrate species T.F. Cross, G. Burnell, J. Coughlan, S. Culloty, E. Dillane, P. McGinnity and E. Rogan Non-native Aquaculture Species Releases: Implications for Aquatic Ecosystems Elizabeth J. Cook, Gail Ashton, Marnie Campbell, Ashley Coutts, Stephan Gollasch, Chad Hewitt, Hui Liu, Dan Minchin, Gregory Ruiz and Richard Shucksmith Safe and nutritious aquaculture produce: Benefits and risks of alternative sustainable aquafeeds J. Gordon Bell and Rune Waagbo NGO approaches to minimizing the impacts of aquaculture: a review Katherine Bostick Aquaculture in the coastal zone: pressures, interactions and externalities David Whitmarsh and Maria Giovanna Palmieri Future trends in aquaculture: Productivity growth and increased production Frank Asche, Kristin H. Roll and Sigbjorn Tveteras Status and future perspectives of marine aquaculture Yngvar Olsen, Oddmund Otterstad and Carlos M. Duarte Epilogue

Heavy metals, trace elements and sediment geochemistry at four Mediterranean fish farms

Trace element concentrations in sediment were investigated at four fish farms in the Eastern Mediterranean Sea. Fish farms effects were negligible beyond 25-50 m from the edge of the cages. Based on elemental distribution, sediments from the farms were separated into coarse oxidized and silty reduced ones. Fish feed is richer in P, Zn and Cd than reference and impacted stations. Comparison among impacted stations and the respective reference stations shows that, in anoxic sediments, all elements had higher concentrations at the impacted stations than at reference stations while in oxic sediments, many elemental concentrations were lower at impacted stations than at reference stations. The behavior of elements and therefore their distribution is affected by changes in sediment grain size, organic content and redox regime. Elements in sediments around fish farms can be clustered into five groups according to these environmental variables. In silty and anoxic sediments, element concentrations were higher than in coarse and oxic ones. Several approaches were used to assess potential sediment toxicity (enrichment factors, geoaccumulation indices, contamination factors) as well as to assess the potential danger to aquatic life (Sediment Quality Guidelines, SQG). Cu, Zn and Fe can cause from threshold to extreme effects on aquatic life in anoxic, fine-grained sediments and As can cause threshold effects in all types of sediment around fish farms. Other elements (Cr, Pb, Mn) can also cause unwanted effects when compounded with elevated background levels.

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. High shoot mortality rates were recorded near the cages, up to 20 times greater than at control sites. Recruitment rates increased in variability but could not compensate mortality, leading to rapid seagrass decline within the first 100 m from cages. Seagrass mortality increased with total sedimentation rates (K=0.55, p<0.0002), and with organic matter (K=0.50, p=0.001), total nitrogen (K=0.46, p=0.002) and total phosphorus (K=0.56, p<3.10(-5)) inputs. P. oceanica decline accelerated above a phosphorus loading threshold of 50mg m(-2)day(-1). Phosphorus benthic sedimentation rate seems a powerful predictor of seagrass mortality from fish farming. Coupling direct measurements of benthic sedimentation rates with dynamics of key benthic species is proposed as an efficient strategy to predict fish farm impacts to benthic communities.

Analysing the impact of bottom trawls on sedimentary seabeds with sediment profile imagery

Abstract Sediment profile imagery (SPI) was evaluated for the assessment of otter trawling impacts on the seabed. This technique allows the imaging of the topmost sediment layers in profile, including the sediment–water interface. Two areas in the Aegean Sea were investigated in time series, each with control and impact areas: a commercial fishing lane with soft sediments at approximately 200 m depth and an experimentally trawled lane with harder maerly sediments at approximately 80 m depth. In total, 158 images were taken at the deep ground and 124 at the shallow ground. A number of measurements were taken from each image, leading to estimates of comparative penetration and small-scale seabed surface roughness. In addition, a large number of surface and subsurface attributes were noted in the images to form the basis of a multivariate analysis. Results indicated that penetration and roughness by themselves were not very good indicators, although roughness was a better indicator particularly in coarse sediments. The major reason for this is that the measurements alone (in particular roughness) do not distinguish between biological and anthropogenic disturbance. The multivariate analysis combining the measurements with the attributes was a good indicator in investigating trawling impacts in coarse sediments, where the lack of good penetration can be compensated by the view over the sediment surface, where more attribute-type data can be gathered. The SPI sampling window gives a relatively small imaged sample in comparison to other imaging techniques (side scan sonar, video, etc.) and in a heterogeneous environment, the more the replicates, the more reliable the method will be. A tiered imaging approach is recommended where more than one methodology is used.

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. 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.