Angelo G. Solimini

Developing a multimetric index of ecological integrity based on macroinvertebrates of mountain ponds in central Italy

The lack of biological systems for the assessment of ecological quality specific to mountain ponds prevents the effective management of these natural resources. In this article we develop an index based on macroinvertebrates sensitive to the gradient of nutrient enrichment. With this aim, we sampled 31 ponds along a gradient of trophy and with similar geomorphological characteristics and watershed use in protected areas of the central Apennines. A bioassessment protocol was adopted to collect and process benthic samples and key-associated physical, chemical, and biological variables during the summer growth season of 1998. We collected 61 genera of macroinvertebrates belonging to 31 families. We calculated 31 macroinvertebrate metrics based on selected and total taxa richness, richness of some key groups, abundance, functional groups and tolerance to organic pollution. The gradient of trophy was quantified with summer concentrations of chlorophyllxa0a. We followed a stepwise procedure to evaluate the effectiveness of a given metric for use in the multimetric index. Those were the pollution tolerance metric ASPT, three metrics based on taxonomic richness (the richness of macroinvertebrate genera, the richness of chironomid taxa, and the percentage of total richness composed by Ephemeroptera, Odonata, and Trichoptera), two metrics based on FFG attributes (richness of collector gatherer taxa and richness of scraper taxa) and the habit-based metric richness of burrowers. The 95th percentile of each metric distribution among all ponds was trisected for metric scoring. The final Pond Macroinvertebrate Integrity Index ranged from 7 to 35 and had a good correlation (R2xa0=xa00.71) with the original gradient of environmental degradation.

Performance of different biotic indices and sampling methods in assessing water quality in the lowland stretch of the Tiber River

The lowland stretches of rivers are usually the ones where a macroinvertebrate species collection is more difficult to obtain because of the depth and turbidity of the water. Since the choice of the index and of the specific sampling technique is critical for the final result, there is a strong interest into setting up reliable methods for assessing the biological water quality. The aim of this paper is to elucidate the performances of four biotic indices and the influence of four sampling methods on the water quality assessment of a deep and turbid stretch of a river. We collected macroinvertebrates seasonally at 10 sampling sites along the final stretch of the Tiber River using four sampling methods (including hand net, wood and plastic artificial substrates). At the same time, chemical, physical, and bacteriological variables were recorded monthly along the same river stretch. Considering those variables, sampling sites were grouped into three clusters with different water quality, using the chronological clustering method. The same result was obtained from macroinvertebrate data using the same method. We then examined the ability of four biotic indices widely used in Italy to discriminate between the three clusters. The indices are: BMWP’ (British Monitoring Working Party, modified for Spain), ASPT (Average Score Per Taxon, modified for Spain), EBI (Extended Biotic Index) and IBE (Indice Biotico Esteso). BMWP’ and ASPT’ showed the best results. BMWP’ and ASPT’ scores — but not those of EBI and IBE — were sensitive to the different sampling methods utilised. We concluded that in this type of river stretch, BMWP’ and ASPT’ could be more useful than EBI and IBE although the relative efficiency of the chosen sampling method should be taken into account.

Temporal pattern of macroinvertebrate diversity and production in a new man made shallow lake

The construction of an aquatic system to recycle the wastewater coming from an experimental aquaculture plant provided the opportunity to follow the evolution of structural and functional properties of a community in a new eutrophic shallow lake. Specific aims of this study were to describe the temporal patterns of diversity and production of the macroinvertebrate assemblage in different habitats. The benthic assemblage was sampled monthly for 3 years starting 1 month after pond filling. Each month, replicate samples of invertebrates were collected with quantitative methods from 3 habitats: unvegetated bottom, submerged vegetation and emergent vegetation of the littoral zone. We collected a total of 48 macroinvertebrate taxa belonging to 38 families. The number of taxa increased rapidly during the first phase of colonization (93% of taxa were already recorded within 14 months from pond filling) and then slowly decreased through the next 2 years. Diversity pattern through time was not consistent among habitats, being higher in the unvegetated bottom during the first year and on the submerged vegetation and the littoral vegetation in subsequent years. Slopes of rank-abundance curves showed differences among years and habitats, even though all habitats showed a trend towards the increase of the relative dominance of few taxa (e.g. diminishing of slopes). Macroinvertebrate production changed with time and was different among habitats. The development of submerged and emergent macrophytes greatly increased not only the diversity, but also the production of the whole macroinvertebrate assemblage. %

Size structure of benthic invertebrate assemblages in a Mediterranean river

We examined the temporal, longitudinal, and among-substrate variation of the size structure of the invertebrate assemblage in a Mediterranenan river (Aniene River, central Italy). Sampling was conducted with quantitative methods on different substrates every 2 mo at 2 sites for 1 y and at 9 additional sites in spring 1997. Water-quality variables, periphyton standing crop, and physical characteristics of sites were also recorded. The Aniene River showed large longitudinal changes in overall physical features, periphyton biomass, and water quality that were reflected in dramatic changes of the taxonomic composition of the invertebrate assemblage. Insects were numerically dominant in the upper reach and codominant with gastropods in the middle reach, whereas oligochaetes, crustaceans, and chironomids were predominant in the lower and polluted reach. Despite these changes, the shape of the size structure of the invertebrate assemblage was similar among sites, dates, and substrates, with limited departures from the average size spectrum. Body mass alone accounted for the largest part of the variance of the abundance per size class (48%) whereas date, site, and substrate accounted for an additional 13%. These data support early observations of size spectrum invariance from North American streams and rivers, reinforcing the view that size-dependent processes may structure lotic benthic assemblages.

Sieve retention probabilities of stream benthic invertebrates

Abstract Replicate samples of cobbles and loose inorganic and organic matter collected from 3 stream-riffle sites with different periphyton communities were passed through a geometric series of 9 sieves (0.063–16 mm mesh) to quantify sieve retention probabilities of benthic invertebrates. Sieves retained all organisms with a body length >10× the mesh size. Logistic regression models were estimated to describe retention probabilities as functions of body length and mesh size. Retention probability functions differed slightly but significantly among sites, operators, and taxa. Retention probabilities were higher for samples containing filamentous algae, which entangled invertebrates. Size distributions of straight, elongate invertebrates (e.g., oligochaetes, midge larvae) retained by sieves were more variable than distributions of more spherical organisms (e.g., gastropods). On average, the 1-mm sieve retained >90% of invertebrate biomass but <33% of individuals retained by a 63-μm sieve. Size distribution of organisms retained by coarse sieves (≥1 mm), combined with logistic functions predicting retention probability, can be used to describe abundance, biomass, and size distribution of organisms retained by fine sieves. These results suggest that unbiased descriptions of benthic communities can be obtained with relatively little effort by using a minimum sieve mesh size of 1 mm.

Nutrient and chlorophyll a temporal patterns in eutrophic mountain ponds with contrasting macrophyte coverage.

In shallow lakes, macrophytes have important effects on food webs, community structure and nutrient dynamics. For this reason they play a significant role in the restoration of degraded systems. Particularly when present with large coverage, they establish mechanisms favoring low phytoplankton biomass and a decrease of nutrient concentration in the water column. Even if these effects are documented from a number of systems, little evidence comes from shallow mountain lakes. In this study, we report temporal patterns of phytoplanktonic chlorophyll a and nutrient concentration in six eutrophic mountain ponds showing contrasting macrophyte coverage. Six ponds, situated in the Italian Apennines at altitudes ranging from 1164 to 1604xa0m, were monitored from March to November 1997. Four subsurface water samples were collected at each pond on every visit and analysed for chlorophyll a and nutrients following standard methods. Ponds were divided into two groups: vegetated (VP) and unvegetated (UP) according to their summer macrophyte coverage (respectively >xa030% and <xa030% of pond area). A nested ANOVA was used to detect macrophyte coverage, season and date (nested within season) effect on phytoplanktonic chlorophyll a concentration, dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP). Chlorophyll a was affected by coverage (P < 0.01) and by season (P < 0.05). In both groups chlorophyllxa0a concentration increased from spring to summer, but differences were higher in UP than in VP. DIN was affected by coverage and season but temporal pattern was not consistent among UP and VP (interaction among coverage and season was significant, P < 0.01). SRP was not affected by coverage (P = 0.158) and season (P = 0.169). Our results on mountain ponds are consistent with those of similar lowland systems. We conclude that managing the presence of macrophytes can be an effective tool for the restoration of eutrophic shallow lakes also in mountain areas.

Performance of different biotic indices and sampling techniques for the assessement of water quality in the lowland stretch of the river Tiber.

The lowland stretches of rivers are usually the ones where a macroinvertebrate species collection is more difficult to obtain because of the depth and turbidity of the water. Since the choice of the index and of the specific sampling technique is critical for the final result, there is a strong interest into setting up reliable methods for assessing the biological water quality. The aim of this paper is to elucidate the performances of four biotic indices and the influence of four sampling methods on the water quality assessment of a deep and turbid stretch of a river. We collected macroinvertebrates seasonally at 10 sampling sites along the final stretch of the Tiber River using four sampling methods (including hand net, wood and plastic artificial substrates). At the same time, chemical, physical, and bacteriological variables were recorded monthly along the same river stretch. Considering those variables, sampling sites were grouped into three clusters with different water quality, using the chronological clustering method. The same result was obtained from macroinvertebrate data using the same method. We then examined the ability of four biotic indices widely used in Italy to discriminate between the three clusters. The indices are: BMWP (British Monitoring Working Party, modified for Spain), ASPT (Average Score Per Taxon, modified for Spain), EBI (Extended Biotic Index) and IBE (Indice Biotico Esteso). BMWP and ASPT showed the best results. BMWP and ASPT scores – but not those of EBI and IBE – were sensitive to the different sampling methods utilised. We concluded that in this type of river stretch, BMWP and ASPT could be more useful than EBI and IBE although the relative efficiency of the chosen sampling method should be taken into account.

Selecting macroinvertebrate taxa and metrics to assess eutrophication in different depth zones of Mediterranean lakes

In this paper we investigate the response of macroinvertebrates and several metrics based on their presence/absence to eutrophication in some Mediterranean lakes of the volcanic district of Italy. A large dataset was assembled from previous studies comprising presence/absence of macroinvertebrate data from 185 sites located in three different depth zones (sandy eulittoral, vegetated infralittoral and sublittoral /profundal zone) of five lakes sampled between 1976 to 2004. Lakes were assigned to trophic categories based on total phosphorus and Secchi depth annual means. For each depth zone, species composition and richness-based metrics were compared between the different lake trophic categories. Results showed that species composition differed among lake zones and, in each depth zone, among sites belonging to lakes of different trophic state. Using a cut off value of 60 %, 23 taxa in the eulittoral, 31 in the infralittoral and 14 in the sublittoral/profundal were selected by the SIMPER routine as indicators of different trophic categories. The metric based on molluscan and large crustacean taxa was significantly higher in oligotrophic sites compared to eutrophic ones in all the three benthic zones, whereas the BMWP and ASPT scores and total taxa richness correctly differentiated between sites of different lake trophic category only in the sublittoral/profundal zone. We conclude that eutrophication pressures could be assessed by the use of certain richness-based metrics not only in the sublittoral/profundal but also in the sandy eulittoral and vegetated infralittoral zones.

Species distribution and habitat features in lentic Odonata

Abstract The relationships between species assemblages and pond characteristics were investigated in a well preserved Mediterranean coastal woodland. Data on adult abundance were collected fortnightly. Pond area and depth, shade, riparian vegetation, presence of four classes of aquatic plants, presence of fish and both the distances from pond to pond and from pond to sea were considered as pond features. Results showed the presence of 23 Odonata species on 23 ponds. A Mantel test showed that the matrices of pond to pond topographic distances and that of pond to pond faunistic similarity were independent, which supports the hypothesis that the adult Odonata actively choose their breeding site. A stepwise multiple regression showed that only pond size, minimum water level and riparian vegetation had significant effects (all positive) on the total number of Odonata species in each pond. On the other hand, a canonical correspondence analysis showed that the composition of Odonata species assemblages was sensitive to almost all variables. From the point of view of Odonata conservation, both the moderate effect of Gambusia hol‐brooki and the positive effect of the riparian vegetation on the number of Odonata species appear particularly interesting for restoring or creating Odonata habitats.

Plant-associated invertebrates and hydrological balance in the large volcanic Lake Bracciano (Central Italy) during two years with different water levels

Lakes in the Mediterranean region experience an altered hydrological balance with large water level reductions and/or fluctuations within and between years. To date, little is known about the reaction of invertebrate assemblages inhabiting the littoral zone to water level changes in natural lakes. Here, we present the case of the volcanic Lake Bracciano, one of the largest and deepest Italian lakes. We compared the numerical composition and taxonomic richness of plant-associated invertebrate assemblages sampled from three sites and three depth ranges (0–4xa0m, 4–8xa0m and 8–15xa0m) between years with different water levels. Using historical data, we built a hydrological balance model to assess the role of different water budget components on the water levels. The hydrological balance showed that the volume of water currently abstracted for human use exceeds the potential changes caused by the projected warming of climate and decreasing amount of precipitation by nearly an order of magnitude. In a low water level year, littoral macrophytes and invertebrate assemblages exhibited qualitative and quantitative differences at all sampling sites and depths. The invertebrate assemblage showed a reduced taxonomic richness and lower numerical abundance of the more sessile forms (water mites, gastropods, nematodes, naidid oligochaetes), which feed directly on living plants or epiphytic algae, and an increase of more mobile and/or detritivore taxa.