Papers by Ioannis Karakassis
Frontiers in Marine Science, Jan 4, 2023
In addition to food supply, there is a growing recognition of the wider ecosystem benefits of Int... more In addition to food supply, there is a growing recognition of the wider ecosystem benefits of Integrated Multitrophic Aquaculture (IMTA) systems in coastal waters, including regulating services such as carbon sequestration and nutrient remediation. The water trophic status and the co-cultured species combinations affect IMTA productivity. In this study, we examined the ability of different combinations of IMTA organisms to remediate nutrients and the economic/environmental gain for reducing the environmental footprint in potential IMTA systems of the eastern Mediterranean. The results showed that the co-cultivation of organisms can reduce the negative effects on the marine environment of a fish farm both on the water column and the sediment. Meso-and eutrophic water states do not show a high variation in terms of foot print mitigation, with all three of the co-cultivated organisms to perform well. In oligotrophic waters, the obligatory absence of mussels reduces the effectiveness of the IMTA system. As expected, larger-sized IMTA systems have higher production rates and as a result higher percentage of nutrient removal. Finally, bivalve harvesting helps to remove the carbon that is trapped in their shells, contributing to the mitigation of processes related to climate change, such as the acidification of the oceans.
Development of monitoring techniques and models for the assessment of the environmental impact of fish cages in the Eastern Mediterranean
Uriarte A. (ed.), Basurco B. (ed.). Environmental impact assessment of Mediterranean aquaculture ... more Uriarte A. (ed.), Basurco B. (ed.). Environmental impact assessment of Mediterranean aquaculture farms Zaragoza : CIHEAM Cahiers Options Méditerranéennes; n. 55 2001 pages 201-203 Article available on lin e / Article dispon ible en lign e à l'adresse :
State-of-the-art review. WP 2 final report
MERAMOD (version 1.4). Model for predicting the effects of Mediterranean fish farms. EU Project Q5RS-2000-31779
Uriarte A. (ed.), Basurco B. (ed.). Environmental impact assessment of Mediterranean aquaculture ... more Uriarte A. (ed.), Basurco B. (ed.). Environmental impact assessment of Mediterranean aquaculture farms Zaragoza : CIHEAM Cahiers Options Méditerranéennes; n. 55 2001 pages 201-203 Article available on lin e / Article dispon ible en lign e à l'adresse :
Preliminary results on oxygen, carbon and nutrient fluxes in a Posidonia oceanica meadow, impacted by fish farm effluents
メソコスム実験における底生遠洋系生物の結合:遅延堆積物応答とレジームシフト【Powered by NICT】
Science of The Total Environment, 2017
Frontiers in Marine Science, Oct 12, 2021
Marine Environmental Research, Feb 1, 2019
A bathymetric transect in the north coast of Crete first studied in 1989, was revisited 24 years ... more A bathymetric transect in the north coast of Crete first studied in 1989, was revisited 24 years later. Identical sampling design, season, techniques and protocols were followed in both studies in order to minimize bias in the long-term comparisons. This comprehensive macrofaunal dataset (4 stations, 2 sampling seasons, 7 replicates in each
Ices Journal of Marine Science, Nov 23, 2018
Fisheries have global socioeconomic and ecological effects. Long-term ecological studies could be... more Fisheries have global socioeconomic and ecological effects. Long-term ecological studies could be beneficial to ecosystem approach management and biodiversity conservation, however, they are rare. In this study, the impacts of bottom trawling on a traditional fishing ground in the Eastern Mediterranean were addressed and an improvement in diversity metrics and ecological quality status were detected and ascribed to the Greek economic crisis. After 18 years, there was a modest increase in species richness, total abundance, and ecological status in the unaffected zone and more pronounced improvement in the trawled zone pointing at a possible link to a decrease in fishing effort. This upturn emphasized the strong link between financial activities and ecology. The present study underlines the multiple and variable effects of economy not only on countries and citizens but also on the environment and ecosystem conservation and management.
Biogeosciences discussions, Mar 9, 2012
The aim of this work was to study the role of the seagrass Posidonia oceanica on the cycling of a... more The aim of this work was to study the role of the seagrass Posidonia oceanica on the cycling of a wide set of trace elements (Ag,
Marine Ecology Progress Series, Apr 30, 2009
The pan-European MacroBen database was used to compare the AZTI Marine Biotic Index (AMBI) and th... more The pan-European MacroBen database was used to compare the AZTI Marine Biotic Index (AMBI) and the Benthic Quality Index (BQI ES), 2 biotic indices which rely on 2 distinct assessments of species sensitivity/tolerance (i.e. AMBI EG and BQI E[S 50 ] 0.05) and which up to now have only been compared on restricted data sets. A total of 12 409 stations were selected from the database. This subset (indicator database) was later divided into 4 marine and 1 estuarine subareas. We computed E(S 50) 0.05 in 643 taxa, which accounted for 91.8% of the total abundances in the whole marine indicator database. AMBI EG and E(S 50) 0.05 correlated poorly. Marked heterogeneities in E(S 50) 0.05 between the marine and estuarine North Sea and between the 4 marine subareas suggest that sensitivity/tolerance levels vary among geographical areas. High values of AMBI were always associated with low values of BQI ES , which underlines the coherence of these 2 indices in identifying stations with a bad ecological status (ES). Conversely, low values of AMBI were sometimes associated with low values of BQI ES resulting in the attribution of a good ES by AMBI and a bad ES by BQI ES. This was caused by the dominance of species classified as sensitive by AMBI and tolerant by BQI ES. Some of these species are known to be sensitive to natural disturbance, which highlights the tendency of BQI ES to automatically classify dominant species as tolerant. Both indices thus present weaknesses in their way of assessing sensitivity/tolerance levels (i.e. existence of a single sensitivity/tolerance list for AMBI and the tight relationship between dominance and tolerance for BQI ES). Future studies should focus on the (1) clarification of the sensitivity/tolerance levels of the species identified as problematic, and (2) assessment of the relationships between AMBI EG and E(S 50) 0.05 within and between combinations of geographical areas and habitats.
Meramed: Developing monitoring guidlines and modelling tools for environmental effects from Mediterranean aquaculture
Functional adaptations of benthic communities to organic matter enrichment at the edge of an allowable zone of effect (AZE)
Estuarine, Coastal and Shelf Science, 2021
Abstract In a changing environment, it is important to understand the contribution of faunal and ... more Abstract 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.
Frontiers in Marine Science, 2020
Excessive primary productivity due to nutrient inputs is a potential problem in coastal areas whe... more Excessive primary productivity due to nutrient inputs is a potential problem in coastal areas when resulting in high organic matter sedimentation rates. Microphytobenthos and heterotrophic bacteria are two components of the benthic ecosystem that contribute to nutrient cycling and decomposition of organic matter. In this context, the effects of nutrient addition and the associated in situ produced organic matter on microphytobenthos community composition and benthic bacterial viability were assessed in a mesocosm experiment for 58 days. The experimental setup included triplicate mesocosms filled with sediment and water under three levels of nutrient addition ("control," "low," and "high"). Benthic algal community composition was assessed using chemotaxonomy and bacterial viability was estimated using flow cytometry and a double-staining protocol. Multivariate analysis detected a significant effect of treatment and time on microphytobenthic community composition indicating a difference between control and low mesocosms and also between low and high treatments at Days 12 and 24 of the experiment. Nonetheless, microphytobenthos implied high resistance and redundancy of benthic algae to disturbance as all three treatments showed no significant difference in community structure between Days 0 and 58. Bacterial viability responded quickly to the high nutrient addition and was significantly lower than in the "control" and "low" treatments at Days 6 and 12. Both pelagic and benthic environmental variables were correlated to these changes in benthic community.
Marine Environmental Research, 2018
Marine habitat assessment using indicator species through Species Distribution Modeling (SDM) was... more 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. The C. gibba model successfully predicted the occurrence of this species in areas with increased physical disturbance driven by chlorophyll a concentration, whereas the habitat map for F. hyalinus showed an increased probability of occurrence in chlorophyll-poor areas, affected mainly by salinity. We advocate the use of C. gibba as a proxy for eutrophication and the incorporation of this species in monitoring studies through SDM methods. For the Mediterranean Sea we suggest the use of F. hyalinus in SDM as an indicator of environmental stability and a possible forecasting tool for salinity fluctuations.
Frontiers in Marine Science, 2017
A benthic-pelagic mesocosm experiment was performed to study how the benthic macrofaunal communit... more A benthic-pelagic mesocosm experiment was performed to study how the benthic macrofaunal community responds to a eutrophication gradient. The novel experimental setup allowed the induction of an eutrophication gradient in the water column and the detailed documentation of the response of the benthos in terms of biodiversity and ecosystem processes. Nine mesocosms were deployed in the facilities of the Hellenic Center for Marine Research in Crete in the eastern Mediterranean. The mesocosms were 4 m deep, contained 1.5 m 3 coastal water, and included 85 liters of undisturbed sediment at the bottom. No water or sediment exchange was allowed. The experimental design included a Control and two eutrophication levels (Low and High) for the 58-day duration of the experiment. Macrofaunal samples were collected at the end of the experiment from each mesocosm and compared to the ones collected at the beginning of the experiment from the sediment collection area. Results show that the High eutrophication treatment differed significantly from the Control and Low treatments in terms of macrofaunal species composition, diversity, ecological status and ecosystem processes. The increased availability of organic matter in the sediment caused differences in macrofaunal community structure by favoring deposit-feeding species with high bioturbation ability, which significantly increased their abundance. The increased bioturbation potential of the new community combined with the high organic matter consumption contributed to the oxygenation of the sediment within the mesocosm, preventing the creation of hypoxic conditions in the sediment and maintaining ecosystem health despite the highly eutrophic conditions and significant changes in sediment geochemical variables. In the oligotrophic eastern Mediterranean, healthy benthic ecosystems may use existing ecosystem processes to "buffer" the negative effects caused by eutrophication.
Frontiers in Marine Science
Benthic–pelagic coupling studies have shown that the response of the benthic system to eutrophica... more Benthic–pelagic coupling studies have shown that the response of the benthic system to eutrophication is subject to complex nonlinear dynamics with specific thresholds beyond which abrupt changes in the response of the ecosystem occur and time lags between inputs and responses. The “HYPOXIA: Benthic–pelagic coupling and regime shifts” project aimed to investigate how nutrient input in the water column results in ecological processes of eutrophication, which may lead to significant, irreversible changes in the eastern Mediterranean marine ecosystems within a short period of time. The project included analysis of historical water and benthic data, field sampling, and mesocosm experiments. From the project results, it can be concluded that nutrient inputs are quickly capitalized by small phytoplankton species in the water column resulting in the bloom of specific species with high nutrient uptake capabilities. When Eutrophic Index values (calculated using nutrient and chlorophyll-a con...
Science of The Total Environment, Sep 1, 2020
Beta diversity metrics detect large-scale macrobenthic community shifts. • Species replacement is... more 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.
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Papers by Ioannis Karakassis