Artemis Nicolaidou

Assessment of distubance in Mediterranean lagoons: An evaluation of methods

A number of methods were applied to assess disturbance in macrozoobenthic communities in three Mediterranean lagoons with different levels of stress. Tsopeli, Ionian Sea, with no obvious source of stress, harbours a fauna typical of brackish-water lagoons. Vivari, Aegean Sea, also without apparent source of disturbance, is characterised by a few typical lagoonal species and some species characteristic of perturbation. Goro lagoon, in the northern Adriatic, is much larger and more open to the sea. At the centre of the lagoon, where anoxia is known to occur in the summer (“Goro polluted”), the fauna is dominated by species typical of disturbance and a few lagoonal species. A dredged area closer to the sea (“Goro dredged”) is totally dominated by species characteristic of disturbance. The species diversity in all lagoons ranges from low to very low. According to the distribution of individuals in geometric abundance classes, all the lagoons are characterised as stressed. The distribution of individuals in geometric size classes shows dominance of larger specimens in the least disturbed Tsopeli and exclusively small sizes in the greatly disturbed dredged area of Goro. The abundance/biomass comparison curves characterise Tsopeli as undisturbed, Vivari and Goro polluted stations as moderately disturbed and Goro dredged station as disturbed. The last two methods agree with the characterisation derived by examining the dominant species. It is concluded that methods based on size changes of the fauna are more sensitive than those based on relative abundance in assessing disturbance in coastal brackish-water lagoons.

Transfer of metal detoxification along marine food chains

It has been observed previously that the digestive gland of the carnivorous gastropod mollusc, Murex trunculus , does not accumulate metals which occur in high concentration in the digestive gland of its prey, the detritus-feeding gastropod, Cerithium vulgatum. It is proposed that mechanisms of metal detoxification which operate in C. vulgatum render metals biologically unavailable to M. trunculus. In the present work, this scheme is tested by feeding tissues containing detoxified metals from a gastropod, bivalve and barnacle to carnivorous gastropods. Metals in the prey are accumulated in insoluble granules in the digestive gland of the gastropod, kidney of the bivalve and gut connective tissue of the barnacle. These tissues are fed to the carnivores and the granules pass through the entire length of the gut. They are egested as clean preparations within the faecal pellets and they still contain the metals introduced by the tissues of the prey. This transfer of detoxification between species indicates that the food chain progression of material can result in the reduction of the bioavailability of metals. The observations are recorded by scanning electron microscopy and X-ray microanalysis.

Metals in sediment, seagrass and gastropods near a nickel smelter in Greece: Possible interactions☆

Accumulation of Cd, Co, Cr, Cu, Fe, Mn, Ni and Zn was studied in the sediments, Cymodocea nodosa leaves, roots and stems and in two gastropods from an area adjacent to a ferro-nickel smelting plant and a control site on the east coast of Greece. In the sediment, the metals, with the exception of Cu, have significantly higher concentrations in the polluted than in the clean site. There is a tendency for C. nodosa tissues in the polluted area to have higher concentrations of metals although the differences are not always statistically significant. Co, Mn, Ni and Zn are in higher concentrations in the leaves than in the other tissues, a trend more obvious in the polluted site. Concentrations of metals in the viscera of the gastropods Cerithium vulgatum and Monodonta mutabilis are higher than in the muscle (except for Cd) and significantly higher in the animals from the polluted site. It is suggested that Mn is taken up from the water by C. nodosa leaves, which in the form of detritus enter C. vulgatum. Mn concentrates in the viscera of C. vulgatum in the form of granules. Zn follows the same route with additional amounts being taken by C. vulgatum directly from the water.

Index of size distribution (ISD): a method of quality assessment for coastal lagoons

A new index was developed as a tool for quantifying the degree of disturbance in lagoons in order to meet the objective of Ecological Quality Status (EcoQ), using the zoobenthos quality element. The Index of Size distribution (ISD) is proposed to assess the ecological quality status of coastal lagoons. It represents the skewness of the distribution of individuals of a benthic community in geometric size (biomass) classes. The ISD was applied in three coastal lagoons with different levels of disturbance and classified them as of good, moderate and poor ecological quality. A scheme for the classification of EcoQ in lagoonal systems is presented. The index showed a strong relationship with the percentage of organic carbon in the sediment, as well as with the dissolved oxygen concentrations. ISD having the advantage of good discriminating power and not demanding high taxonomic resolution, could be a simple and promising tool to be further applied and tested in Mediterranean lagoons.

Variable transfer of detoxified metals from snails to hermit crabs in marine food chains

In any polluted marine environment, different invertebrate species contain markedly different concentrations of heavy metals. Primary producers take metals from seawater, but animals take additional metals from diets of animals, plants and detritus. Metals in a dietary organism of a food chain have varying reactivities and they follow different biochemical pathways. Excess metals are bound by ligands to form insoluble compounds within cytological compartments. These metabolic systems prevent the disruption of normal biochemical reactions by metals. The present work on Mediterranean invertebrates, initiated in Greece in 1993, used digestive glands from three species of marine snail,Monodonta mutabilis (Philippi),Cerithium vulgatum (Bruguière), andMurex trunculus (Linnaeus) as prey tissue, and hermit crabsClibanarius erythropus (Latreille) as predators; the digestive glands and faecal pellets from all animals were analysed by atomic absorption spectroscopy and x-ray microanalysis. Most metals detoxified by the snails are unavailable to the crabs and they pass straight through the gut and appear in the faecal pellets. This applies to significant proportions of the manganese, nickel, copper, zinc and silver which are bound electrostatically to phosphate or covalently to sulphur within membrane-bound intracellular compartments. Cadmium and chromium are transferred to the crabs. In digestive glands of snails, cadmium is bound to soluble highsulphur protein in the cytosol; the cytology of chromium in these animals is not known.

Inter-annual variability of soft bottom macrofaunal communities in two Ionian Sea lagoons

Inter-annual variation in the composition of the soft bottom macrobenthic communities of two undisturbed lagoons, in Amvrakikos Gulf, Ionian Sea, Greece, was investigated over three consecutive summers. The environmental parameters that showed the greatest variability were organic carbon of the sediment and salinity. The species found were typical of lagoonal systems, the most common and abundant of which were Abra ovata, Mytilaster minimus and, in the most enclosed areas, larvae of chironomids. Multivariate analysis registered community changes, which were mostly caused by changes in species dominance. Structural community characteristics such as number of species, number of individuals and diversity did not show significant differences among years except in the stations with least water exchange with the sea.

BIOREDUCTION OF ZINC AND MANGANESE ALONG A MOLLUSCAN FOOD CHAIN

Marine invertebrates accumulate and detoxify metals in intracellular phosphate granules in various tissues. These include the digestive gland of gastropods, kidney of bivalves and gut parenchymous tissue of barnacles (reviews-Nott, 1991; Viarengo and Nott, 1992). When these tissues are fed to carnivorous gastropods the granules pass through the gut and appear in the faecal pellets (Nott and Nicolaidou, 1990). Granules in the tissues of origin and in the faecal pellets have been examined in the scanning electron microscope and the elemental composition determined by X-ray microanalysis (Nott and Nicolaidou, 1990). These investigations have shown that in invertebrate tissues the granules consist of magnesium, phosphorus, potassium and calcium together with lesser amounts of sulphur and chlorine. After passage through the gut of a carnivorous gastropod the granules produce peaks for magnesium, calcium and phosphorus but not sulphur, chlorine and potassium. Further to this, granules which contain zinc and manganese in the winkle Littorina littorea, clam Chlamys opercularis and bar

Mediterranean pollution from a ferro-nickel smelter: differential uptake of metals by some gastropods

Abstract Cadmium, Co, Cr, Cu, Fe, Mn, Ni, and Zn were measured by atomic absorption spectroscopy in the digestive gland of the marine gastropods Cerithium vulgatum, Monodonta spp., Murex trunculus, Conus mediterraneus , and Patella coerulea , sampled during different seasons at four sites near a ferro-nickel smelting plant and two control sites on the east coast of Greece. Near the smelter there were higher concentrations of all metals in Cerithium (except Cu) and Murex , and of Ni and Co in Monodonta , compared with the control sites, which indicated that the plant contaminated the environment. The animals from the contaminated area showed marked differences in concentrations which were associated both with the genera and the sites, while there were no consistent seasonal variations.

Assessment of contaminant impacts in a semi-enclosed estuary (Amvrakikos Gulf, NW Greece): Bioenergetics and biochemical biomarkers in mussels

A combination of bioenergetics and biochemical biomarkers in mussels was applied to assess possible pollution impacts in a protected semi-enclosed estuary (Amvrakikos Gulf, NW Greece) that receives pesticide discharges through riverine transport. Scope for growth, a physiological condition index representing the energy budget of the organism, was applied to detect general stress effects on the health status of mussels. The low energy budgets of mussels revealed stress conditions and provided early warning signals of possible consequences at higher levels of biological organization. Biochemical markers of exposure confirmed a risk of pesticide contamination. Decreased acetylcholinesterase activities indicated exposure to organophosphate and carbamate pesticides. Responses of the antioxidant enzyme glutathione peroxidase suggested the presence of contaminants capable of reactive oxygen species production that could be related to organochlorine pesticide contamination in the area. On the other hand, metallothionein levels implied low metal contamination.

Metals in gastropods—metabolism and bioreduction

Abstract In marine gastropods, high concentrations of heavy metals can occur in the digestive gland. The metals are accumulated within intracellular mineralized granules as phosphates and within lysosomal residual bodies in association with sulphur. X-Ray microanalysis shows that in the phosphate granules, an increase in the quantity of metal is associated with a reduction in the magnesium/calcium ratio. However, analyses of the whole digestive gland by atomic absorption spectrometry show that an increase in the quantity of metal can be associated with an increase in the concentration of magnesium. To account for these changes, it is proposed that metals induce the formation of magnesium phosphate in the granules as a source of metal-binding ions. The excess magnesium is displaced from the phosphate granules by the metals and accumulated by the carbonate granules in the interstitial region of the gland. The intracellular metals are stored in a form which renders them unavailable to the general metabolic processes of the animal and also to a carnivore which eats the tissue. Thus, uptake by the first animal results in bioamplification but transfer to the second animal results in bioreduction.