Giuseppe Crosa

Water quality as a determinant of the composition of fish parasite communities

To investigate the relationship between fish parasite communities and water quality level, metazoan parasites were examined in 157 specimens of chub (Leuciscus cephalus L.), sampled in four lowland water courses (northern Italy): Ticino river (unpolluted), Naviglio Pavese Canal (slightly polluted), Lambro river near the Merone village (polluted) and near Monza (severely polluted). Dactylogyrus vistulae, Paradiplozoon ergensi, Bucephalus polymorphus, Acanthocephalus anguillae and larval stages of Tylodelphys clavata were found in all the sampled sites. The distribution of Lamproglena pulchella and Pomphorhynchus laevis was limited to the unpolluted and slightly polluted river sectors, while Asymphylodora tincae, glochidia, along with larval stages of Diplostomum spathaceum, were absent in the severely polluted site. The variability of the calculated infection indices (prevalence, mean abundance and mean intensity), the degree of interactivity among parasites, as well as parameters of species richness and diversity suggest that the structure of parasite communities are affected by the water contamination level.

Eutrophication management in surface waters using lanthanum modified bentonite: a review

This paper reviews the scientific knowledge on the use of a lanthanum modified bentonite (LMB) to manage eutrophication in surface water. The LMB has been applied in around 200 environments worldwide and it has undergone extensive testing at laboratory, mesocosm, and whole lake scales. The available data underline a high efficiency for phosphorus binding. This efficiency can be limited by the presence of humic substances and competing oxyanions. Lanthanum concentrations detected during a LMB application are generally below acute toxicological threshold of different organisms, except in low alkalinity waters. To date there are no indications for long-term negative effects on LMB treated ecosystems, but issues related to La accumulation, increase of suspended solids and drastic resources depletion still need to be explored, in particular for sediment dwelling organisms. Application of LMB in saline waters need a careful risk evaluation due to potential lanthanum release.

Monogenoids from Freshwater Fish in Italy, with Comments on Alien Species

Abstract Sixteen species of both native and alien fish were collected and examined for monogenoids from September 2001 to March 2004 in bodies of water located within fishing areas of the Po River (northern Italy). A checklist of monogenoids was compiled and integrated with literature reports of Italian monogenoids, updating the number of known Italian freshwater monogenoids to 35, with 15 new host or locality records (or both). Parasitological data of monogenoids on native and alien demonstrate the ability of alien monogenoids to colonize native hosts. The process of invasion of nonnative monogenoids in Italy started about 30 yr ago and is still ongoing: 17 of the 35 monogenoids now present in Italian freshwaters are considered alien (5 species of monogenoids arrived in Italy from America, 11 from Central Europe, and 1 from Eurasia), 2 are considered native, and the remaining 16 are considered of unknown origin because of our limited knowledge concerning the original distribution of monogenoids.

The invasive crayfish Orconectes limosus in Lake Varese: estimating abundance and population size structure in the context of habitat and methodological constraints

Abstract Invasive alien species (IAS) potentially may alter all levels of the ecological organization of aquatic water bodies. Therefore, in the context of the EU Water Framework Directive, they represent a significant pressure that should be considered in the assessment of the ecological status of a water body and in the formation of restorative programs. A study was carried out to examine different sampling techniques and to assess the current population structure and the differences in spatial distribution of the alien crayfish Orconectes limosus at four sites in Lake Varese (Northern Italy). Three methods were used to assess the crayfish population: mark-recapture, catch per unit effort during night-time snorkelling and quadrat sampling. For the mark-recapture exercise the ventral somites of crayfish were marked using visible implant elastomer tags. A laboratory experiment was used to verify the effectiveness of elastomer tags for the species prior to their use in the field. Crayfish were more abundant at sites characterized by stone substrate than at sites dominated by macrophytes. Hydromorphological alteration of the shoreline (quantified using the newly developed lake habitat survey methodology) at one site appeared to promote the establishment of alien crayfish. Crayfish caught by snorkeling in open water led to an underestimation of the smallest size-classes compared with underwater quadrats. Underwater quadrats on stone substrates provide a quantitative estimation of abundance and size-structure allowing the comparisons of crayfish populations from different lakes. This method could be applied to assess the extent of pressure resulting from alien crayfish under the Water Framework Directive. Crayfish biomass was found to be 82.9% of other macroinvertebrates indicating their importance in the structure and functioning of the lake ecosystem. The presence of a second alien species of crayfish, Procambarus clarkii, was recorded for the first time in the lake.

A northern Italian shallow lake as a case study for eutrophication control

Lake Varese (northern Italy) has shown deterioration in water quality since the 1960s and, as a result of the long duration of direct discharge of untreated sewage into the lake, it was classified as being hypertrophic. To recover the lake water quality, a series of externally and internally remedial actions were implemented in subsequent years. The applied sewage collecting system induced a reduction of the external P loads from 50 t P year−1 to 16t P year−1 and the weighted mean annual TP concentration decreased from 352 μg P l−1 to 85 μg P l−1, typical of eutrophic conditions. The hypolimnetic water withdrawals, adopted in the years 2000–2003, allowed a reduction of the internal P loads of about 3–5 t P. In the same years, 500t O2 were injected at depths of 4.5–8 m during the summer months. In spite of these internal remedial actions, no significant reduction of the weighted mean annual concentration of the TP could be observed, and during the summer stratification period no significant reduction of the volumes of anoxic water and of the duration of the anoxia were detected. The anoxic conditions are still the prevailing force driving the lake P-budget, maintaining the lake in eutrophic status.

Lesser Flamingo Phoeniconaias minor as a nomadic species in African shallow alkaline lakes and pans: Genetic structure and future perspectives

The Lesser Flamingo Phoeniconaias minor is a nomadic species, which inhabits shallow alkaline lakes and pans in sub-Saharan Africa and southern Asia. The extent of genetic diversity and the degree of differentiation within and among populations are important factors to determine in order to help manage and conserve the species, categorised as Near Threatened by the IUCN. This study provides an assessment of the population structure of the two largest African populations of P. minor by genotyping six microsatellite loci from 30 individuals sampled on Lake Bogoria (Kenya) and 11 individuals from Makgadikgadi Sua Pan (Botswana). The alleles detected per locus ranged from four to 13. The Lake Bogoria population harboured 15 specific alleles, whereas the Makgadikgadi Sua Pan population only six alleles. Moderate genetic diversity (He = 0.64–0.69) was comparable with populations that have not suffered from demographic bottlenecks or inbreeding. The populations are genetically similar with little differentiation (FST and RST not significantly different from zero). Small but continuous gene flow (the estimated average number of individuals exchanged is 3–4 per generation) was found, probably reflecting the birds nomadic behaviour and the natural presence of temporary shallow waters between the two sampled populations. The results suggest that inbreeding effects at present are unlikely, and hence that the loss and/or degradation of its specialised habitat remains the primary concern for the species’ continued survival.

Lesser Flamingo Phoenicopterus minor populations in eastern and southern Africa are not genetically isolated

A preliminary analysis of the phylogeographic pattern of the two main African populations of Lesser Flamingo Phoenicopterus minor from East and southern Africa was carried out to evaluate possible gene flow. A fragment of mitochondrial DNA encoding the NADH dehydrogenase subunit 2 gene (ND2) was sequenced in 27 specimens from these two populations and 11 haplotypes were identified. The phylogenetic analyses, based both on distance and parsimonious methods (neighbour joining and maximum parsimony), showed a homogeneous clade with a low level of genetic distance (0.26% ± 0.12 SD), which was also evidenced by the minimum spanning network method. The mismatch distribution analysis suggested a sudden demographic expansion from a single ancestral population. This latter result is also reinforced by the presence of few ancestral haplotypes, by the high level of haplotype diversity (0.83) and the low level of nucleotide diversity (0.0015–0.0017). These data support the belief of field ornithologists for restricted interchange between the two populations determined by the geographical distance between the two populations and lack of any observations of movement between them, but with evidence of changes in each populations numbers, giving the concept of a permeable geographic barrier.

Morphological and genetic characterization of Sardinian trout Salmo cettii Rafinesque, 1810 and their conservation implications

AbstractThe morphological and genetic structure of Western Mediterranean trout Salmo cettii inhabiting basins in Sardinia was completed to assist the design of its conservation programmes. Genetic analysis of protein-coding LDH-C1 plus sequencing mitochondrial control region gene and analyses of morphological characters described 253 specimens from seven localities in two basins in Southwest Sardinia. Nuclear and mitochondrial analyses revealed all of the fish were pure-bred native S. cettii, with no introgression from allochthonous S. trutta. The novel 18 mtDNA control region haplotypes were clustered in an ‘insular’ clade, strictly related to the Adriatic haplogroup, and depicted a radial network around two ancestral haplotypes. Completion of discriminant analysis using data on body pigmentation and quantitative morphologic parameters revealed three phenotypic groups within the fish. Each population and phenotype, characterised by high values of nucleotide and haplotype diversity, were not genetically differentiated and not geographically structured according to the two hydrological basins. Geometric morphometric analysis, based on 15 landmarkers, revealed pronounced and highly significant differences in body shape morphology between populations, suggesting S. cettii is locally adapting to extreme environmental conditions and so future management plans for these populations should treat the two basins as distinct morphological units.

Local versus longitudinal biological variability in a high gradient stream

An examination was made of the integration of local biological variation within the longitudinal profile of a stream due to patchy hydraulic patterns. Invertebrates were collected monthly in pool, run and riffle biotopes at five sites on a 20-km mountain stream in Northern Italy, running from 1050 to 235 m a.s.l., and showing a good biological status. About 26 000 individuals belonging to 60 different insect taxa were collected and variation in their distribution and abundance were analysed by Principal Component Analysis. The results provide evidence on pool-riffle biological differences and a discussion is included on the taxa unique to each hydraulic habitat. The pool biotope shows a relatively high insect diversity, but separation of biotopes with high current velocity into riffles and runs did not provide further insight on the patterns of insect distribution. Variation in insect taxonomic structure near the mid-point of the stream longitudinal profile was representative of the total longitudinal variation. This suggests that hydraulically fragmented habitats at one particular site can provide information on invertebrate structure that can be extrapolated to sites upstream and downstream of the sampled site.

Long-term assessment of insecticides treatments in West Africa: aquatic entomofauna

For the control of the Onchocerca volvulus vector in West Africa, up to 18,000 km of rivers from 1975 and up to 50,000 km from 1989 had been partly sprayed weekly with insecticides as part of the Onchocerciasis Control Programme (OCP). To evaluate the possible short-term and long-term effects of the application of insecticides on the non-target fauna, an aquatic monitoring programme was set up during the initial phase of the programme. By analysing the invertebrate data, which were collected using various sampling strategies from four different countries between 1977 and 1996, this paper evaluates the long-term changes of the invertebrate populations with respect to their taxonomic composition as well as their trophic structures. The discussed results of the applied numerical analysis strategy suggest that neither the taxonomic nor the trophic structures are greatly altered from the range of biological, flow-related variation that normally occurs in the studied river systems. This allows us to conclude that the biological variation found here is ecologically acceptable.