Ferruccio Maltagliati

Biodiversity and adaptive mechanisms in brackish water fauna

A comparative analysis of estuaries, lagoons and coastal ponds focusing on population differentiation, and community structure is necessary to correctly address the issue of brackish water biology. Although the different biotopes all present similar features of environmental unpredictability and the common presence of the hypohalobic contingent (artenminimum), they each have their own characteristics, due to the evolution of peculiar balances in their relation to the sea on the one hand and inland waters on the other. In addition to euryhaline species, locally adapted populations of stenohaline species typical of marine habitats, as well as some recently introduced species, are also found. These species have given rise to euryhaline populations, reaching their maximum development in an optimal site. This situation occurs between basins with essentially similar ecological features and probably depends both on the different degree of adaptability of many species to a specific environmental parameter and the type of biocoenoses adjacent to the brackish basin. These populations possess genotypes allowing adaptation to brackish waters, which have resulted in the differentiation, through selection, of individuals capable of fine-grained perception of environmental unpredictability. Experimental works demonstrated the existence of genetically differentiated populations, or, ultimately, sibling species complexes, in several brackish species with broad geographical distribution and belonging to a wide range of taxonomic groups. The conceptions regarding the uniformity of brackish elements and the doubts concerning the existence of a specific brackish fauna come from the fact that attention generally focuses on species in the traditional meaning of the term, that is to say at the macrosystematic level. Comparative analyses of very fine morpho-physiological changes and genetic analyses result in a rather different picture, leading to the conclusion that in brackish waters a given species of marine origin often consists of many different forms at various levels of differentiation.

Detection of thermal pollution:variability of benthic communities at two different spatial scales in an area influenced by a coastal power station

Abstract The influence of a coastal power station thermal discharge on spatial variability of meiobenthic and macrobenthic community abundances in the Gulf of Follonica (Western Mediterranean) was investigated using Beyond BACI designs in September 1996. Analysis of benthic communities showed that heated effluent seemed not to influence assemblage structure or the spatial distribution of the study taxa. Abundance and variability of the benthic assemblages either did not exhibit significant differences between impact and control locations or the control locations were as different from each other as they were from the impacted location. We conclude that the assemblage abundances in the impacted location were within the range of spatial variability encountered naturally on the western side of the Gulf of Follonica. This research emphasises the importance of including more than one control in any study of a potential impact.

Animal-sediment relationships: Evaluating the 'Pearson-Rosenberg paradigm' in Mediterranean coastal lagoons

We investigated the applicability of the Pearson-Rosenberg (P-R) conceptual model describing a generalized pattern of response of benthic communities in relation to organic enrichment to Mediterranean Sea coastal lagoons. Consistent with P-R model predictions, benthic diversity and abundance showed two different peaks at low (>2.5-5 mg g(-1)) and high (>25-30 mg g(-1)) total organic carbon (TOC) ranges, respectively. We identified TOC thresholds indicating that risks of reduced benthic diversity should be relatively low at TOC valuesabout 28 mg g(-1), and intermediate at values in-between. Predictive ability within these ranges was high based on results of re-sampling simulation. While not a direct measure of causality, it is anticipated that these TOC thresholds should serve as a general screening-level indicator for evaluating the likelihood of reduced sediment quality and associated bioeffects in such eutrophic systems of the Mediterranean Sea.

Allozyme evidence of genetic differentiation between populations of Hediste diversicolor (Polychaeta: Nereididae) from the Western Mediterranean

The occurrence of genetic differentiation among western Mediterranean Hediste diversicolor (Polychaeta: Nereididae) populations was assessed by allozyme electrophoresis on cellulose acetate. Seventeen loci were analysed in four populations. The level of the genetic variability was markedly low (mean H L range: 0.014–0.034), but comparable to that of other brackish water nereidids. The values of Nei genetic distance index (D) confirm the existence of genetic differentiation between the geographically isolated populations at Venice, Elba, Navicelli and Serchio D range: 0.128–0.356). However, the two samples from Serchio and Navicelli, ~15 km apart, were not genetically different (D=0·00005). The level of genetic differentiation in H. diversicolor populations followed the isolation-by-distance model. Reduced gene flow among H. diversicolor populations may be explained by its limited dispersal capacity and the eco-physiological barriers that occur between different brackish habitats.

Small-scale morphological and genetic differentiation in the Mediterranean killifish Aphanius fasciatus (Cyprinodontidae) from a coastal brackish-water pond and an adjacent pool in northern Sardinia

Two samples of Aphanius fasciatuscollected in the Pilo pond (northern Sardinia, Italy) and in an adjacent pool of small surface area were analysed morphologically (235 individuals) and genetically (a subsample of 58 individuals). The aims of the present study were (i) to test the hypothesis that different predation pressures may be associated with morphological and/or genetic differences between samples from each habitat and (ii) to assess the level of divergence between the two populations. Morphological analysis was based on the relative size of fins because it has been shown to be associated with predation pressure. The relative caudal fin area (caudal fin area/total body surface) was smaller in specimens from the pool, in both males and females, whereas no differences were found for the dorsal and anal fin areas. Caudal fins with higher aspect ratio (fin depth/fin length) were found in fish from the pool but not in the pond, due to a higher fin depth. We hypothesised that specimens from the pool would show smaller caudal fin area, since they are subject to lower predation pressure. Random amplification of polymorphic DNA (RAPD) analysis revealed a relatively high degree of both within- and between-sample genetic heterogeneity. The pond and pool samples exhibited heterozygosities, which did not differ significantly by t-test. Between-sample genetic divergence was highlighted by the coancestry coefficient (h = 0.301 ± 0.059, P < 0.001) and analysis of molecular variance (AMOVA) (variance between sites = 41%, P < 0.001). Genetic divergence between sites with a relatively high genetic diversity within both samples suggested that the population in the pool did not originate from a single colonisation event with a small number of founders. The genetic divergence between the two populations is consistent with their differences in fin size.

Mitochondrial DNA reveals genetic structuring of Pinna nobilis across the Mediterranean Sea.

Pinna nobilis is the largest endemic Mediterranean marine bivalve. During past centuries, various human activities have promoted the regression of its populations. As a consequence of stringent standards of protection, demographic expansions are currently reported in many sites. The aim of this study was to provide the first large broad-scale insight into the genetic variability of P. nobilis in the area that encompasses the western Mediterranean, Ionian Sea, and Adriatic Sea marine ecoregions. To accomplish this objective twenty-five populations from this area were surveyed using two mitochondrial DNA markers (COI and 16S). Our dataset was then merged with those obtained in other studies for the Aegean and Tunisian populations (eastern Mediterranean), and statistical analyses (Bayesian model-based clustering, median-joining network, AMOVA, mismatch distribution, Tajima’s and Fu’s neutrality tests and Bayesian skyline plots) were performed. The results revealed genetic divergence among three distinguishable areas: (1) western Mediterranean and Ionian Sea; (2) Adriatic Sea; and (3) Aegean Sea and Tunisian coastal areas. From a conservational point of view, populations from the three genetically divergent groups found may be considered as different management units.

Variance estimate and taxonomic resolution: An analysis of macrobenthic spatial patterns at different scales in a Western Mediterranean coastal lagoon

The effects of taxonomic resolution on the variance estimates of macrobenthic assemblages were studied at four spatial scales in a Mediterranean coastal lagoon. The assemblages exhibited significant differences at all the investigated scales; however, spatial variability was mainly associated with the smallest and the largest scales. The decrease of taxonomic resolution (from species to family) was not related to a decrease of the overall variability and similar estimates of variance components were obtained using species and family resolution levels. The ordination models derived from species and family abundances were very similar both in terms of location and dispersion effect, while further aggregation to the class level began to alter the observed spatial patterns. In future studies aimed at assessing changes in the lagoon, resources derived from the cost reductions achieved using family level could be employed to plan more frequent surveys and/or to adopt complex spatial sampling designs with a high number of replicates.

Perspectives on the ecological assessment of transitional waters

Brackish water biotopes (lagoons, estuaries, salt marshes, and coastal ponds) constitute transitional waters systems, the main characteristic of which is the instability of chemical and physical parameters and characteristic bio-ecological aspects (Cognetti, 1994; Cognetti and Maltagliati, 2000; Bilton et al., 2002). European transitional waters include a large range of diversified ecosystems of very important scientific and economic value; very often they are threatened by the effect of multiple anthropogenic activities. Their conservation needs careful attention and specific actions based on appropriate biological and ecological knowledge. Furthermore, a concept that differentiates the conservation approach of many transitional environments, such as coastal lagoons and coastal ponds, from the other aquatic biotopes is their ‘‘anthropodependence”. In fact, natural ecological succession of lagoon ecosystems proceeds toward a number of changes to the final transformation into terrestrial ecosystems. The maintenance and conservation of lagoon environments requires, and has required since ancient times, periodic human intervention, especially as regards lagoon aquaculture. The levels of uncertainty about the mechanisms and processes occurring in transitional waters makes it difficult to translate the assessment and the conservation strategies into political recommendations because they greatly differ from general guidelines that are effective for other ecosystems. For instance, if we consider the problem of water eutrophication, it is often difficult to disentangle the contribution of pressure by human activities from natural causes. Hence, appropriate and specific methodologies are required for the assessment of the ecological status of transitional environments. These methodologies may greatly differ from those classically used in marine or freshwater ecosystem monitoring, as recommended by the EU Water Framework Directive (WFD, 2000/ 60/EC). In fact, the concept of ecological quality status (EQS), included in the WFD as a way to assess the ecological quality of aquatic environments, can be sometimes unsuitable when applied to transitional waters (Dauvin, 2007). Additionally, another difficulty depends on biogeogeographical differences of various European basins. Currently, many attempts are being made to adapt biotic indices to specific situations related to transitional waters within a restricted geographical region. For instance, Munari and Mistri (2007) proved the effectiveness of a biotic index that did not conform to the WFD in four Tyrrhenian lagoons. Nevertheless, the importance of WFD has been underlined by Borja (2005), who depicted WFD as an opportunity to develop, standardise and implement a unique European methodology for monitoring and assessment of the status of aquatic ecosystems. This point was discussed in an international congress within the American Society of

Genetic structure of Octopus vulgaris (Mollusca, Cephalopoda) from the Mediterranean Sea as revealed by a microsatellite locus

Abstract An investigation of the genetic variability of Octopus vulgaris, an intensively harvested species, was carried out using a mi crosatellite locus as genetic marker. Samples from one eastern At lantic and nine Mediterranean locations were analysed. In each population, the number of alleles at locus Ov06 varied from four to seven and was 21 overall. Observed and expected heterozy‐gosity values ranged from 0.310 to 0.655 and 0.506 to 0.841, re spectively. Permutation tests and the positive average value of FIS showed significant departures from the Hardy‐Weinberg equilibri um, due to a deficit of heterozygotes. FST showed high levels of genetic divergence among the populations. Genetic distance val ues ranged from 0.0004 to 7.1520. Isolation‐by‐distance was not evident either by the Mantel test or multidimensional scaling. Mi crosatellite results are consistent with a previous allozyme study, and suggest that the common octopus does not form a single panmictic unit in the Mediterranean. From a fishery perspective, this information leads to the conclusion that the management of O. vulgaris should be planned on a local level.

Genetic population structure of Neanthes succinea (Polychaeta: Nereididae)

Two samples of Neanthes succinea (Frey & Leuckart 1847) from the Mediterranean Sea were investigated. Twenty-one loci were analysed; seven of them were polymorphic in both populations. The level of heterozygosity was 2.2% and 4.4% in populations from the Tyrrhenian and Adriatic coasts respectively. The value of Neis genetic identity index (1=0.965), together with the mean F(IT) (=0.350), shows that the samples can be considered reproductively isolated populations. F-statistics indicate that ME-1 is the discriminant locus between populations.