Manolis Tsapakis

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.

The composition and sources of PM2.5 organic aerosol in two urban areas of Chile

Fine particle (PM2.5) samples were collected, using a charcoal diffusion denuder, in two urban areas of Chile, Santiago and Temuco, during the winter and spring season of 1998.Molecular markers of the organic aerosol were determined using GC/MS.Diagnostic ratios and molecular tracers were used to investigate the origin of carbonaceous aerosols.As main sources, road and non-road engine emissions in Santiago, and wood burning in Temuco were identified.Cluster analysis was used to compare the chemical characteristics of carbonaceous aerosols between the two urban environments.Distinct differences between Santiago and Temuco samples were observed.High concentrations of isoprenoid (30–69 ng m � 3 ) and unresolved complex mixture (UCM) of hydrocarbons (839–1369 ng m � 3 ) were found in Santiago.High concentrations of polynuclear aromatic hydrocarbons (751 7304 ng m � 3 ) and their oxygenated derivatives (47 2n g m � 3 ), and of n-alk-1-enes (16713 ng m � 3 ) were observed in Temuco. r 2002 Elsevier Science Ltd.

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.

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. In the surface sediments under the farms (0 m distance from the edge of the cages) and in the immediate vicinity, the concentration levels of n-alkanes and PAHs were significantly higher than in the surrounding sediments in both sites. PAHs and n-alkanes individual component profiles of fish feed and sinking material were similar with the corresponding profiles of the sediment samples collected in the immediate vicinity around the cages. On a daily basis, the average PAH sedimentation fluxes under the cages was 24.4 microg m(-2) d(-1), which is considerably higher compared with the observed PAH sedimentary fluxes in the open eastern Mediterranean. Our results imply that fish farming is a significant source of these persistent organic pollutants (POPs) in the marine environment and therefore a likely change in the scale of production might introduce new sources of environmental risk. Further work is required in order to develop an appropriate monitoring system for the sustainable development of the aquaculture sector.

Aquatic Global Passive Sampling (AQUA-GAPS) Revisited: First Steps toward a Network of Networks for Monitoring Organic Contaminants in the Aquatic Environment

Organic contaminants, in particular persistent organic pollutants (POPs), adversely affect water quality and aquatic food webs across the globe. As of now, there is no globally consistent information available on concentrations of dissolved POPs in water bodies. The advance of passive sampling techniques has made it possible to establish a global monitoring program for these compounds in the waters of the world, which we call the Aquatic Global Passive Sampling (AQUA-GAPS) network. A recent expert meeting discussed the background, motivations, and strategic approaches of AQUA-GAPS, and its implementation as a network of networks for monitoring organic contaminants (e.g., POPs and others contaminants of concern). Initially, AQUA-GAPS will demonstrate its operating principle via two proof-of-concept studies focused on the detection of legacy and emerging POPs in freshwater and coastal marine sites using both polyethylene and silicone passive samplers. AQUA-GAPS is set up as a decentralized network, which is open to other participants from around the world to participate in deployments and to initiate new studies. In particular, participants are sought to initiate deployments and studies investigating the presence of legacy and emerging POPs in Africa, Central, and South America.

Saharan Dust Deposition Effects on the Microbial Food Web in the Eastern Mediterranean: A Study Based on a Mesocosm Experiment

The effect of episodicity of Saharan dust deposition on the pelagic microbial food web was studied in the oligotrophic Eastern Mediterranean by means of a mesocosm experiment in May 2014. Two different treatments in triplicates (addition of natural Saharan dust in a single-strong pulse or in three smaller consecutive doses of the same total quantity), and three unamended controls were employed; chemical and biological parameters were measured during a 10-day experiment. Temporal changes in primary (PP) and bacterial (BP) production, chlorophyll a (Chla) concentration and heterotrophic bacteria, Synechococcus and mesozooplankton abundance were studied. The results suggested that the auto- and hetero-trophic components of the food web (at least the prokaryotes) were enhanced by the dust addition (and by the nitrogen and phosphorus added through dust). Furthermore, a 1-day delay was observed for PP, BP and Chla increases when dust was added in three daily doses; however, the maximal values attained were similar in the two treatments. Although the effect was evident in the first osmotrophic level (phytoplankton and bacteria), it was lost further up the food web, masked under the impact of grazing exerted by predators such as heterotrophic flagellates, ciliates and dinoflagellates. This was partly proved by two dilution experiments. This study demonstrates the important role of atmospheric deposition and protist grazing when evaluating the effect on oligotrophic systems characterised by increased numbers of trophic levels.

Flow injection with on-line dilution and single particle inductively coupled plasma – mass spectrometry for monitoring silver nanoparticles in seawater and in marine microorganisms

Single particle inductively coupled plasma mass spectrometry (spICP-MS) is a unique tool for detecting silver nanoparticles in environmental samples at concentrations similar to those predicted in surface waters. In this study, we present a novel flow injection spICP-MS method configured to allow for rapid on-line dilution at the tip of a pneumatic nebulizer. Such a sample introduction system permits the detection and characterization of silver nanoparticles in seawater at low ng Ag per L concentrations. Dilution (up to 1/80) accounts for the minimization of seawater originating spectroscopic interferences for both silver isotopes, whereas signal suppression caused by the matrix is corrected by utilizing a freshly prepared seawater solution containing well characterized silver nanoparticles (matrix matching) in order to determine ionization and transport efficiencies. Furthermore, we present a novel, yet straightforward method for determining silver nanoparticles and dissolved silver in marine microorganisms and/or interacting with natural organic matter. This method is based on the ultrasonication of filters used for sieving 15 L of seawater, once they are immersed in deionized water. The purpose of this approach is to lyse microorganism cell membranes and thus liberate their silver content. Subsequent flow injection spICP-MS allows for the determination of the silver nanoparticles and dissolved silver bio-accumulated in marine biota and/or interacting with natural organic matter for two different filter size fractions (i.e. 0.2–2 μm and 2–5 μm). Application of these methodologies for studying seawater microcosm and mesocosm systems allowed for the detailed monitoring of the fate of silver nanoparticles in the marine environment.

The impact of silver nanoparticles on marine plankton dynamics: Dependence on coating, size and concentration

During this study, three microcosm experiments were carried out with natural coastal seawater, collected in the Eastern Mediterranean Sea, in order to assess the effect of silver nanoparticle (AgNP) exposure to natural plankton communities. The impact of coating (branched-polyethyleneimine: BPEI vs. poly-vinylpyrrolidone: PVP), size (40 vs. 60nm), concentration (200, 500, 2000, 5000 and 10,000ng Ag L-1) and silver form (dissolved Ag+ vs. AgNPs) were tested. The results of chlorophyll a concentration revealed that PVP AgNPs caused a higher toxicity than BPEI AgNPs, and this was possibly related to the measured higher dissolution rate. Additionally, toxicity of BPEI AgNPs was size-dependent, with 40 being more toxic than 60 nm AgNPs, which was nevertheless not seen clearly for PVP AgNPs. Interestingly, community composition altered in response to AgNP exposure: cyanobacterial abundance was negatively affected at concentrations ≥200ng Ag L-1, and dinoflagellate abundance and composition were altered at a 2000ng Ag L-1 concentration. Specifically, dinoflagellate (Gymnodinium, Prorocentrum and Gyrodinium) and diatom (Nitzschia, Navicula and Climacosphenia) genera either increased or decreased, highlighting taxa-specific effects, with some of them being able to tolerate, compensate or even benefit from AgNPs. Silver in either form (dissolved Ag+ or in NPs) caused almost identical results in the plankton community, further indicating that Ag+ release is the primary cause of AgNP toxicity. This study employed for the first time environmentally relevant AgNP concentrations (minimum 200ng Ag L-1) in natural seawater without pre-filtration steps and showed that community changes were driven by the exposure but were largely dependent on ambient physico-chemical characteristics and should be further investigated.

Arsenic speciation in fish from Greek coastal areas

Arsenic speciation analysis was conducted on fish samples (sardine and anchovy) collected from six areas along the Greek coastline, i.e. Artemisium Straits, Thermaikos Gulf, Amvrakikos Gulf, Strymonian Gulf, Thracian Sea, and Elefsina Gulf. Total arsenic levels ranging from 11.8 to 62.6mg As/kg dry weight were determined. Arsenobetaine, a non-toxic form of arsenic, was found to be the main arsenic species, present at 8.6 to 58.8mg As/kg dry weight, accounting for 67-95% of the total arsenic. Also detected in all fish samples was dimethylarsinic acid, although at considerably lower concentrations, ranging from 0.072-0.956mg As/kg dry weight. Monomethylarsonic acid was detected at low levels in all anchovy samples, and only in sardines from one area. Finally, inorganic arsenic in the form of arsenate was detected only in fish at one area, indicating the possible effect of an environmental parameter on its presence at detectable amounts. Statistical analysis revealed the environmental variables, such as salinity, total organic carbon and nitrogen, ammonium, phosphate, total phosphorus, dissolved oxygen and pressure index, are potentially correlated to As species concentrations. Furthermore, based on factor analysis, the biological parameters, such as fish weight, lipids, protein and ash content, that are correlated to As species concentrations of fish were also identified. The interrelationship of arsenobetaine and dimethylarsinic acid concentrations within each fish species was evaluated.