Saronicos Gulf Research Articles

Occurrence and Distribution of Polycyclic Aromatic Hydrocarbons in the Marine Surface Microlayer of an Industrialized Coastal Area in the Eastern Mediterranean

Concentrations of dissolved and particulate polycyclic aromatic hydrocarbons (PAHs) were determined seasonally in sea surface microlayer (SML) and sub-surface water (SSW) within the Saronicos Gulf, Greece, close to a highly industrialized coastal zone. For the 16 US EPA priority PAHs, the sum of dissolved PAHs (∑dPAHs) concentrations ranged from 40.4 to 237 ng L−1 in SML, 22.8–180 ng L−1 in SSW0.2, whereas the corresponding concentrations in suspended particulate matter (∑pPAHs) were 30.8 to 177 ng L−1 and 36.8–171 ng L−1, respectively. The enrichment factor (EF) for dissolved ∑dPAHs varied from 0.9 to 2.1 with a mean value of 1.5 (n = 10) being statistically significantly greater than unity, whereas for particulate ∑pPAHs, no enrichment of the SML was reported. Enrichment factors of 5–6 ring PAHs were higher near the industrial zone. The possible sources, fate, and toxicity of PAHs are also discussed.

Risk assessment of oil spill accidents

<div> <p>The objective of this study is to present an integrated stochastic approach for quantifying the risk of oil spill in marine waters and adjacent coasts. This was achieved via the effective cooperation between the National Technical University of Athens (NTUA) and the Bogazici University (BU) within the framework of a bilateral joint research project. The proposed methodology integrates four models: (1) a physics-based hydrodynamic model (HYM) which computes the spatial distribution of surface water currents as the main driving force for oil transport, (2) an expert-based accident assessment model (<st1:stockticker w:st="on">AAM</st1:stockticker>) to compute the frequency, location and characteristics of expected oil spills, (3) a physics-based oil spill model (<st1:stockticker w:st="on">OSM</st1:stockticker>) which computes the propagation and fate of the oil slick, and (4) an expert-based impact assessment model (IAM) to compute the distribution of coastal impact due to oil contamination. The model is applied to two pilot areas: the Saronicos Gulf, Greece and Izmir Bay, Turkey. The flow fields in these areas were determined by the HYM for a large number of wind scenarios, based on which the transport and weathering of an oil slick were computed by the <st1:stockticker w:st="on">OSM</st1:stockticker>. The most probable oil spill locations were identified by <st1:stockticker w:st="on">AAM</st1:stockticker> based on the bathymetry, the maritime traffic and the currents. Finally, the IAM was applied to draw Coastal Oil Impact Maps in the regions of interest. Emphasis was placed on the presentation of the risk of oil reaching the coastline. Environmental sensitivity and economic importance were taken into account by assigning index values to all coastal cells. </p> </div> <p> </p>

Experimental study of cadmium bioaccumulation in three Mediterranean marine bivalve species: correlation with selected biomarkers

AbstractAn ecotoxicological study is presented, in which three marine bivalve species (Mytilus galloprovincialis, Callista chione, and Venus verrucosa) living in different habitats were studied for Cd bioaccumulation, under laboratory conditions. The bivalves, originating from a relatively polluted marine area of Greece (Saronicos Gulf), were exposed to 0.5 mg Cd L–1 seawater (4.4 μmol Cd L–1 seawater) for 5, 10, 15, and 20 days. Control animals were kept in metal-free seawater as well. Three or four different parts of the organisms (gills, mantle, body, digestive system) were examined for the bioaccumulation of Cd, as well as the levels of three biomarkers (metallothioneins, acetylcholinesterase, lipid peroxidation). A depuration experiment was also carried out. During the experiment, the initial levels of Cd in the control animal tissues either decreased or remained constant and low. The organisms exhibited different behavior regarding Cd bioconcentration and biomarker responses as well as tissue distribution of Cd. After the depuration period, significant amounts of Cd remained in the organisms’ tissues, much higher than the respective levels in control animals.

The Distribution of Copper in Saronicos Gulf after the Operation of the Wastewater Treatment Plant of Psitalia

The establishment of the Wastewater Treatment Plant of Athens is considered as the main factor contributing to the improvement of water quality and recovery of the marine ecosystem in Saronicos gulf as it removes significant percentage of pollutants entering the gulf, including heavy metals. The comparison of concentrations of dissolved and particulate copper during 1993, 1994 (before the operation of the plant) and 1998, 1999 and 2000 (after the beginning of the operation) revealed that some changes in the distribution of copper occurred because of this major change concerning the pollution sources of the gulf. The effects are both direct, like the increased concentrations in the sediments near Psitalia and the slight decrease of mean values of dissolved copper and indirect, associated with the decrease of dissolved oxygen in the deep water of the western basin, i.e. the decrease of dissolved copper in this layer and the increase of copper concentrations in surface sediments. The general conclusion of this study is that the overall picture of copper pollution of the gulf has differentiated but not radically changed.

The sensitivity of mussel-watch programmes to detect temporal trends in the bio-availability of metals. A case study of the Saronicos Gulf of Greece

Statistical power analysis has been used to determine the sensitivity of the mussel-watch programme in Hellenic seas, with particular focus placed on the data obtained for metal content in mussels from the Saronicos Gulf during the period 1985-1997. Sample collection was carried out quarterly. Soft tissues of 60-100 similarly sized mussels (Mytilus galloprovincialis) were pooled into six composite samples and analysed by Atomic Absorption Spectroscopy (AAS). The study concludes that the resolution of monitoring programmes employed thus far is sufficiently high to detect temporal trends related to changes in contaminant levels caused either by drastic environmental control (such as those imposed on point-source pollutants) or by sudden increases in contaminant load. However, the detection of more subtle trends, which may be expected in the near future as a result of global pollution-control policies, is likely to require the adoption of much more sensitive programmes. In addition, the review of up-to-date knowledge on metal biology in mussels suggests that factors related to growth and reproduction should be taken into account to remarkably increase the resolution of mussel-watch programmes. Indicative maximum values for components of error to be complied with during routine monitoring are suggested.

Influences on the Distribution of Marine Debris on the Seafloor of Shallow Coastal Areas in Greece (Eastern Mediterranean)

The abundance and composition of marine benthic debris was investigated in shallow coastal areas of Greece (eastern Mediterranean). The mean total density of marine debris in the areas surveyed was 15 items per 1000 m2 and ranged from 0 to 251 items per 1000 m2, with plastics dominating. Much higher marine debris densities were found in this study than those found in most studies surveying the continental shelf or the deep seafloor, indicating that pollution with marine debris is more intense in coastal areas. Greater abundance of marine debris was found in bays than in open areas. Artisanal fishing activities were found to significantly contribute to marine pollution with debris. In the Saronicos Gulf, a densely populated and highly industrialized area, the abundance of marine debris was higher than the rest of the Greek areas surveyed.

Marine eutrophication: a proposed data analysis procedure for assessing spatial trends.

A methodology for the discrimination of the different trophic levels at a spatial scale in the marine environment is proposed using spatial analysis methods and non-parametric statistics. Phytoplankton cell number, being a representative parameter to express trophic trends in the marine ecosystem is selected for the methodology development; Saronicos Gulf, Greece is used for the case study. The proposed stepwise methodology includes interpolation for assessing the spatial distribution of phytoplankton cell number, division of the Gulf into a number of quadrates, development of a scale characterising trophic levels and finally characterisation of the trophic state of each quadrate using non-parametric statistics. The advantages of this methodology and the potential applications in coastal management studies are also discussed.

Categorical mapping of marine eutrophication based on ecological indices

The present work is concerned with the development of methodological procedures for studying the spatial distribution of eutrophication in the marine environment. Seven ecological indices ( S, number of phytoplankton species; N, total number of individuals; D Mg, Margalef’s index; D Mn, Menhinick’s index; D Od, Odum’s species per thousand individuals; H′, Shannon’s Diversity index; E, Evenness index), based on phytoplankton community data collected from Saronicos Gulf, Greece were used for describing the eutrophication state of the sea environment. A representation of the spatial distribution for each ecological index was developed using the Inverse Distance Weighted (IDW) interpolation method. A eutrophication scale for each index was also developed for indicating four different trophic levels in the marine environment (eutrophic, upper-mesotrophic, lower-mesotrophic, oligotrophic); categorization of the interpolated values of each index resulted in a clear illustration of these trophic levels on seven thematic maps. Two methodological procedures were finally applied for synthesizing the information of these thematic maps. The purpose was the development of a final map illustrating the spatial distribution of eutrophication in the study area. The first procedure was based on the integration of unsupervised and supervised classification methods, widely used in the field of remote sensing, while the second one on the overlay technique, simply carried out within the frame of a Geographical Information System (GIS). The hybrid unsupervised/supervised classification method can assess the optimal number of classes in which data values from simultaneously considered parameters could be allocated, while the overlay technique is an additive procedure not taking into account existing trends in the dataset. The advantages and disadvantages of each procedure are further discussed.

Evaluation of the impact from the discharge of treated sewage on the south-east Saronicos Gulf through mathematical water quality modelling

The paper presents the results of a study of the impact caused by the discharge of treated sewage from the south-west Attiki area to the south-east coast of the Saronicos Gulf. The study involved the application of a eutrophication-dissolved oxygen model which, following validation on the basis of field measurements, was applied to predict the impact of three different biological treatment configurations, with and without nutrients removal, as well as three alternative disposal sites on the quality of the receiving waters. The simulation results show that nitrogen is the limiting nutrient and that its removal during treatment results in a substantial improvement of the quality of the recipient. The disposal site is a critical factor in the case of a biological treatment scheme exhibiting carbon removal, but it is of limited importance in the case of treatment systems with nitrogen removal.

Evaluation of the impact from the discharge of treated sewage on the south-east saronicos Gulf through mathematical water quality modelling

The paper presents the results of a study of the impact caused by the discharge of treated sewage from the south-west Attiki area to the south-east coast of the Saronicos Gulf. The study involved the application of a eutrophication-dissolved oxygen model which, following validation on the basis of field measurements, was applied to predict the impact of three different biological treatment configurations, with and without nutrients removal, as well as three alternative disposal sites on the quality of the receiving waters. The simulation results show that nitrogen is the limiting nutrient and that its removal during treatment results in a substantial improvement of the quality of the recipient. The disposal site is a critical factor in the case of a biological treatment scheme exhibiting carbon removal, but it is of limited importance in the case of treatment systems with nitrogen removal.

Effects of formaldehyde preservation on biometrical characters, biomass and biochemical composition ofAcartia clausi (Copepoda, Calanoida)

The effects of formaldehyde preservation on biometrical characters, biomass and biochemical composition of the marine copepodAcartia clausi were studied using the relevant values of fresh unpreserved animals as reference.Acartia were collected in the southern parts of Saronicos Gulf in early May (16.5°C) and late June (21°C). Formalin was found to cause significant shrinkage of cephalothorax length, abdomen length and total length. The sex of individuals, as well as the temperature of seawater at the time of collection seem to influence dimensional losses. Females and animals collected at 16.5°C presented heavier losses. Dry weight is drastically reduced after formaldehyde preservation. Final losses are more severe for females and animals collected at 21°C. Two of the measured biochemical constituents, carbohydrates and neutral lipids, seem to be unaffected by formaldehyde. DNA and RNA although initially affected seem to be stabilized towards the end of the experimental period (30 days). The other biochemical parameters, viz proteins, total lipids and sugars, are profoundly affected by preservation.

The Effect of Temperature, Salinity and Diet On Final Size of Female Tisbe Holothuriae (Copepoda, Harpacticoida)

[Tisbe holothuriae was collected from the Saronicos Gulf (Greece) and cultured in the laboratory at various conditions. Growth of females reared under 12 combinations of temperature (14-24°C) and salinity (26-44%o) and 7 different diets was evaluated. Adult female body length increased slightly with salinity and decreased greatly with temperature, with a maximum value (1.096 mm) at 14°C and 38‰. There were no apparent interactions between these factors. Length is related to temperature and salinity by the following equation, L = 1.39 + 0.0255 - 0.0003S2 - 0.071T + 0.0009T2 + 0.00005ST. There were no significant differences in length of adult females as a result of testing 7 different diets. Significant differences in length were found between the instars on successive days of development, except between the 4th and 5th day, when nauplii were transformed to copepodites., Tisbe holothuriae was collected from the Saronicos Gulf (Greece) and cultured in the laboratory at various conditions. Growth of females reared under 12 combinations of temperature (14-24°C) and salinity (26-44%o) and 7 different diets was evaluated. Adult female body length increased slightly with salinity and decreased greatly with temperature, with a maximum value (1.096 mm) at 14°C and 38‰. There were no apparent interactions between these factors. Length is related to temperature and salinity by the following equation, L = 1.39 + 0.0255 - 0.0003S2 - 0.071T + 0.0009T2 + 0.00005ST. There were no significant differences in length of adult females as a result of testing 7 different diets. Significant differences in length were found between the instars on successive days of development, except between the 4th and 5th day, when nauplii were transformed to copepodites.]

Structure and properties of the attractor of a marine dynamical system

We investigate the properties of a marine dynamical system by means of time series of the sea-level height at four locations in the Saronicos Gulf in the Aegean Sea, Greece. In order to characterize the dynamics, we estimate the dimension of the underlying system attractor, and we compute its Lyapunov exponents. Dimension estimates indicate that the dynamics can be explained by a low-dimensional deterministic dynamical system. Lyapunov exponent estimates further substantiate the above conclusion, while at the same time, indicate that the dynamical system is a rather nonuniform chaotic one.

Field and Bioassay Studies on the Vitamin B12-Phytoplankton-Nutrient Relationships

The seasonal relationships of vitamin B 12 , phytoplankton and nutrients were investigated by field and bioassay experiments in the Saronicos Gulf, Aegean Sea (Eastern Mediterranean Sea). The field data demonstrated a statistically significant negative relationship of vitamin B 12 with Chl α, diatoms, flagellates, phosphate and total inorganic nitrogen. The bioassay experiments were performed using Pavlova lutheri as a test organism and examined the combined effect of nutrients and vitamin B 12 on growth. The results supported the hypothesis that in the area of study vitamin B 12 might not be a limiting factor for phytoplanktonic algae but it certainly stimulates growth through a multiple nutritional mechanism

Temperature, salinity and light induced variations on larval survival and sex ratio of Tisbe holothuriae Humes (Copepoda: Harpacticoida)

Tisbe holothuriae was collected from the Saronicos Gulf of Greece (38%.) and reared under laboratory conditions. The effects of temperature (14, 19, 24 °C), salinity (26, 32, 38, 44%., for each tested temperature), two modalities of light: photoperiod (LD 24:0, 18:6, 12:12, 6:18, 0:24 h), spectral composition (blue, green and red wavelengths) on mortality during larval development and sex ratio of adults were studied. Survival and proportion of females decrease as temperature declines from medium levels (19°C) and salinity from normal levels (38%.). The effects of low temperatures and salinities appear to be pronounced on both parameters studied. Multiple regression analysis proved the quadratic and linear effects of temperature to be more important factors affecting the time required for the death of 50% of the initial nauplii than those of salinity. The linear effect of salinity is a more important factor affecting the sex ratio than temperature. Continuous illumination and long-day photoperiod significantly reduce the larval survival and the proportion of females. Red and green wavelengths markedly increase the percentage mortality. Spectral composition seems not to influence sex ratio.

Seasonal and Spatial Distribution of Vitamin B12 in a Coastal Area of Eastern Mediterranean Sea

AbstractThe seasonal and spatial distribution of vitamin B12 was investigated in Eastern Mediterranean (Saronicos Gulf, Aegean Sea). Vitamin B12 concentration had an annual range 0.12–7.93 ng. 1−1 and an annual mean 1.88 ng. 1−1. The statistical analysis of data indicated significant seasonal and regional variations of vitamin B12 in this area and an inverse relationship of this vitamin with chl a. The results showed that the Eastern Mediterranean Sea contains less vitamin B12 than the Western Mediterranean Sea.

Biochemical composition ofTisbe holothuriae(Copepoda: harpacticoida) and its differentiation in relation to developmental stages

Abstract Tisbe holothuriae Humes were collected from the Saronicos Gulf (Greece) and cultured under laboratory conditions. Dry weight, protein, lipid, carbohydrate and RNAwere determined for various life stages by means of a micro-analytical scheme. In adult females without egg sacs, the proportion of protein, lipid, carbohydrate and RNA (as a percentage of dry weight) was 71.2, 9.7, 2.3 and 1.0, respectively. After the formation of egg sacs, all the above main components increased slightly. The results are discussed in relation to the potential use of the species as live feed for fish larvae and fry.

A possible method for evaluating oligotrophy and eutrophication based on nutrient concentration scales

A statistical analysis of inorganic nutrient data (P-PO 4, N-NO 3, N-NO 2, N-NH 3) has been made for scaling aquatic systems into oligotrophic, mesotrophic and eutrophic water types. The data derived from: (a) inshore and offshore waters of Saronicos Gulf and (b) from nearshore and offshore waters of the Island of Rhodes, Aegean Sea. The procedure followed was the application of the frequency distribution analysis to transformed data and development of nutrient concentration scales on the basis of probabilistic parameters. This procedure might be used to make predictions related to forecasting and evaluation of water quality standards.

Treatment and Disposal Scheme for the Sewage of Athens

ABSTRACTThe sewage from the Greater Athens area is discharged without treatment to the nearby Saronicos Gulf. Recently the Greek government decided to implement an appropriate treatment and disposal scheme, on the basis of a study of the hydrodynamic behaviour of the Gulf and the fate of the discharged pollutants. The study was conducted with the aid of suitable hydrodynamic and water quality models for a number of alternative treatment schemes, ranging from primary treatment to biological treatment with seasonal nitrogen removal, combined with outfalls of different lengths. The results indicate that, although none of the examined schemes will lead to an immediate substantial impact, the scheme that includes biological treatment with seasonal nitrogen removal can eliminate the danger of serious ecological disturbances at a reasonable cost.

Effects of seven diets on the population dynamics of laboratory culturedTisbe holothuriae Humes (Copepoda, Harpacticoida)

The harpacticoid copepodTisbe holothuriae was collected from Saronicos Gulf (Greece) and reared under constant laboratory conditions. In order to study the effects of food on the population dynamics, seven diets were tested: the seaweedUlva; five artificial compound feeds: the liquid Fryfood® (Waterlife), a powder ofMytilus, yeast, soya andSpirulina, respectively; and a mixed diet consisting ofUlva and Fryfood. The life cycle parameters (mortality, sex ratio, generation time, offspring production) were measured, and the demographic variables [mean generation time (T), net reproductive rate (Ro), and intrinsic rate of natural increase (rm)] were determined. As to their efficiency regarding population dynamics, the diets ranked as follows: (1)Ulva+Fryfood, (2),Ulva, (3) Fryfood, (4)Mytilus, (5) soya, (6) yeast, and (7)Spirulina. In this order they cause a progressive increase of both larval mortality and generation time, a progressive decrease of sex ratio, number of offspring per egg sac, number of egg sacs per female and, consequently, of Ro and rm. The observed differences between diets were most pronounced with respect to offspring production. Of the compound diets, those containing animal extracts were more efficient than those containing vegetable materials.Ulva plays an important role in the nutrition ofT. holothuriae, favouring offspring production as well as larval survival, development and pigmentation.Ulva in combination with Fryfood led to a greater copepodid survival and offspring production. This mixed diet proved to be the most favourable for rearing the Greek population oft. holothuriae, resulting in an efficient intrinsic rate of natural increase (rm=0.304) of the population.