Anastasios Eleftheriou

Annelid fauna of a Mediterranean lagoon (Gialova Lagoon, south-west Greece): community structure in a severely fluctuating environment

The annelid community of a shallow Mediterranean lagoon (Gialova Lagoon, Ionian Sea) was studied on a seasonal basis. Out of the 39 species identified eight are reported for the first time from the central Mediterranean. The dominant species were the polychaetes Capitella capitata , Neodexiospira pseudocorrugata , Malacoceros fuliginosus , Perinereis cultrifera , Hediste diversicolor , Heteromastus filiformis and the oligochaete Limnodriloides maslinicensis . Uni- and multivariate methods were employed to study the community structure. The coenocline observed is strongly related to the degree of isolation; its main features (i.e. number of species, density, geometric abundance and size-classes) in space and time are presented and discussed in detail. The distribution pattern of the annelid community has been found to be governed by a different set of environmental factors in each season. Although this narrow lagoonal habitat suffers severe dystrophic episodes it manages to recover, demonstrating a seasonal community pattern.

Deep sea molluscan fauna of the Cretan Sea (Eastern Mediterranean): Faunal, ecological and zoogeographical remarks

The deep sea molluscan fauna of the Cretan Sea (Eastern Mediterranean) was investigated from living material collected by the R/Vs“AEGAEO” and“PHILIA” cruises in the framework of the MTP/MAST EU research programme CINCS, carried out by the I.M.B.C. Examination of the deep sea benthos, with particular reference to the phylum Mollusca, over a grid of stations from depths between 40 and 1570 m, revealed the presence in the area of a diverse fauna consisting of 147 species belonging to 6 different classes. Large numbers of species (44) are new elements of the molluscan fauna of the Cretan Sea while another 4 species (1 Polyplacophora, 2 Gastropoda, and 1 Bivalvia) have not been reported so far from the Aegean or the Eastern Mediterranean. The majority of the species exhibit a wide bathymétrie distribution, from the continental shelf region to the bathyal slope, and only a few species are considered as deep sea species (reported only from the latter). The faunal composition of the collected material from the studied area (in depths over 200 m) clearly demonstrates the presence in the Cretan Sea of theAbra longicallus-association, already reported in other deep basins of the Mediterranean where similar research has been carried out. However, the presence of the bivalveNuculoma aegeensis even in the shallow waters of the continental shelf strengthens the opinion of other authors (Janssen 1989;Dounas &Koukouras 1992) that theNuculoma aegeensis “facies” of the above association is not found as deep asdi Geronimo (1974) had claimed (1500 m). Most of the deep sea mollusc species collected from the Cretan Sea are distributed from the Mediterranean to the Atlanto-Mediterranean and Boreal province while no species with an Indo-Pacific origin (Lessepsian immigrants) were found. Taking into consideration results of studies on the molluscan fauna from shallow waters of the Cretan Sea (Koutsoubas et al. 1992) it can be concluded that this part of the Mediterranean could not be considered as an impoverished system, as it hosts a rather enriched and diverse molluscan fauna numbering more than 400 species.KurzfassungDie Tiefwasser-Mollusken-Fauna aus dem Kretischen Meer (östliches Mittelmeer) wurde anhand von lebendem Material ausgewertet, das während der R/Vs“AEGAEO” und“PHILIA” Fahrten gesammelt wurde, und zwar im Rahmen des MTP/MAST EU Forschungsprojektes CINCS, durchgeführt vom I.M.B.C. Die Untersuchung des Tiefwasser-Benthos, mit besonderem Schwerpunkt auf dem Stamm der Mollusken, zeigte entlang einer Reihe von Stationen, im Tiefenbereich zwischen 40 und 1570 m, die Anwesenheit einer mannigfaltigen Fauna, bestehend aus 147 Arten, die zu 6 verschiedenen Klassen gehören. Eine bedeutende Anzahl von Arten (44) stellt im Kretischen Meer neue Elemente der Mollusken-Fauna dar, während 4 weitere Arten (1 Polyplacophora, 2 Gastropoda, und 1 Bivalvia) noch nicht vom Agäischen oder östlichen Mittelmeer gemeldet worden sind. Die Mehrheit der Arten zeigte eine breite bathymetrische Verteilung vom Kontinentalschelf bis zum bathyalen Abhang, und nur wenige zählen zu den Tiefwasserformen (gemeldet im bathyalen Abhang). Die faunistische Zusammensetzung des gesammelten Materials in der untersuchten Region (in Tiefen über 200 m) demonstriert deutlich das Vorhandensein derAbra longicallus-Assoziation im Kretischen Meer, wie sie schon bei ähnlichen Untersuchungen in anderen Tiefseebecken des Mittelmeeres beschrieben worden ist. Die Präsenz jedoch der bivalvenNuculoma aegeensis, sogar in den flachen Gewässern des Kontinentalschelfs, bekräftigt die Meinung anderer Autoren (Janssen 1989;Dounas &Koukouras 1992), daß dieNuculoma aegeensis “Fazies” der oberen Assoziation nicht so tief gefunden werden wiedi Geronimo (1974) behauptet hat (1500 m). Die meisten Tiefwasser-Mollusken-Arten, die im Kretischen Meer gesammelt wurden, sind von der Mediterranen bis zur Atlanto-Mediterranen und der borealen Provinz verbreitet, während keine Arten Indo-Pazifischen Ursprungs (Lessepsian immigrants) gefunden wurden. Unter Berücksichtigung der Ergebnisse von Studien über die Mollusken-Fauna der flachen Gewässer des Kretischen Meeres (Koutsoubas et al. 1992), könnte man daraufschließen, daß das Kretische Meer, eine eher reiche und mannigfaltige Mollusken-Fauna mit mehr als 400 Arten beherbergt.

Estimating lagoonal biodiversity in Greece: comparison of rapid assessment techniques

An attempt is made to compare the results of different rapid biodiversity assessment techniques at the pan-Mediterranean, sectorial and local levels. A uniform multivariate pattern exists at the pan-Mediterranean and national (sectorial) levels: lagoons can be different when they host only a few species, but as species numbers increase, lagoons become homogenous in composition. Multivariate techniques cannot distinguish anthropogenically-impacted lagoons from those, which are naturally disturbed. In the pan-Mediterranean context it is the higher taxonomic levels, but in the national and local context it is the most abundant macrobenthic groups (polychaetes, molluscs and crustaceans) and meiobenthos which provide patterns closest to that derived from the species level. Taxonomic distinctness indices applied to polychaete and mollusc inventories provide meaningful results at most levels and scales of observation. These indices seem to be robust enough to discriminate anthropogenically impacted from naturally disturbed lagoons.

Mediterranean lagoons revisited: weakness and efficiency of the rapid biodiversity assessment techniques in a severely fluctuating environment

The purpose of this paper is to test the performance of rapid biodiversity assessment techniques in the lagoonal environment at the pan-Mediterranean scale. The multivariate techniques can produce patterns of lagoonal biodiversity along the Mediterranean. Additionally, it is shown that the polychaete inventory can preferably be used rather than the aggregation of information at the family level for the purposes of rapid biodiversity assessment. These techniques, however, appear to be weak for the environmental assessment because they cannot detect differences between the naturally disturbed and the anthropogenically impacted lagoons. Both taxonomic distinctness indices are found to be robust in providing meaningful results for rapid biodiversity/environmental assessment when the crustacean inventory and the polychaete and molluscan ones are used for the estimation of the average taxonomic distinctness and of the variation in taxonomic distinctness values, correspondingly. Conversely, information on the distribution of the macrofaunal species to the Mediterranean lagoons appears to be inadequate for the needs of such rapid biodiversity assessment at a regional scale. It is suggested that information on ecological convergence of the macrofaunal species would probably provide biodiversity indices with additional power, at least in the lagoonal environment.

Interrelationships of bacteria, meiofauna and macrofauna in a Mediterranean sedimentary beach (Maremma Park, NW Italy)

Collelungo beach (Maremma Park, NW Italy), was sampled quantitatively for macrofauna, meiofauna and bacteria in May 2003; several physicochemical variables and variables associated with food availability and sediment structure were also measured. Replicated samples were collected from three sites representing natural conditions, an erosion regime, and the influence of the Ombrone River, respectively, as well as from four stations each located in the surf and sublittoral zones. Both uni- and multivariate techniques were used to assess the benthic community structure and the associated environmental variables. Different diversity indices revealed no pattern; in contrast, multivariate techniques applied on the macrobenthic fauna and the polychaete taxocommunity distinguished between the sites located in natural and eroding conditions from the one located nearby the discharges of the Ombrone river. Τhe community patterns deriving from meio- and macrofauna are clearly divergent. The overall benthic faunal community appears to be influenced by both groups of organisms. The patterns of the meio- and macrofaunal communities seem to be affected synergistically by a number of environmental variables, in accordance with the multicausal environmental severity hypothesis. Meiofaunal patterns are more often correlated with bacteria and the protein concentration than are macrofaunal patterns, indicating a potential utilization of bacteria as a food source by the meiofaunal organisms. Total bacterial numbers are associated with the macrofaunal pattern under the erosion regime, probably as a consequence of competition for food between macrofauna and meiofauna.

A new apparatus for the direct measurement of otter trawling effects on the epibenthic and hyperbenthic macrofauna

A towed trawl simulator sledge (TTSS2) for collecting quantitatively small macrobenthic animals disturbed by the passage of otter trawl groundrope typical of the local fishery is described and illustrated. The TTSS2 was towed from a surface vessel at a speed within the range of commercial trawls, incorporating three sampling nets that open and close by means of an electro-mechanical system. An odometer in contact with the seabed provided a continuous record of the trawled ground. The degree of efficiency of the TTSS2-by means of the attached groundrope that stirs up the surface of the bottom ahead of the nets- was tested in the northern continental shelf of Crete (eastern Mediterranean). Additional trials with a much heavier groundrope were also performed. Analysis and comparison of TTSS2 samples with endobenthic, hyperbenthic and planktonic samples collected by means of conventional sampling gears indicate the presence of a well-defined and distinct fauna in the plume of resuspended sediment behind the groundrope.