Marcello Bazzanti

Factors Affecting Macroinvertebrate Communities in Astatic Ponds in Central Italy

ABSTRACT Twenty astatic ponds near Rome were studied in order to define the relationships between physicochemical variables and macroinvertebrate communities. The main abiotic factor differentiating the ponds was the annual hydrologic cycle. Depth, surface area, and sand percentages in the sediment were higher in permanent ponds, whereas silt+clay content was higher in temporary ones. No difference was recorded in pH, conductivity and oxygen content in the water or organic matter in the sediments between the two pond types. Three main ecological assemblages were distinguished: a) generalist taxa common to both pond types; b) taxa associated with and adapted to temporary ponds; and c) taxa which seemed to prefer permanent ponds. Overall, there was no relationship between number of taxa and surface area, except for Odonata and aquatic macrophytes. A positive correlation was observed between number of macrophyte species and macroinvertebrate taxa richness, and particularly of odonates and chironomids, suggesting that an increase in aquatic vegetation species leads to an increase in microhabitats and suitable food, substrate, and/or refuge from predators. Odonata seemed also to prefer more stable and sunny ponds.

Macrophyte diversity and physico-chemical characteristics of Tyrrhenian coast ponds in central Italy: implications for conservation

Awareness of pond conservation value is growing all over Europe. Ponds are recognized as important ecosystems supporting large numbers of species and several rare and threatened aquatic plants, macroinvertebrates and amphibians. Notwithstanding ponds, particularly temporary ones, are still neglected in Italy. There are some gaps in our understanding of the macrophyte ecology and the conservation value of Mediterranean small still waters. Therefore, this study investigated the macrophyte communities and physico-chemical characteristics of 8 permanent and 13 temporary ponds along the Tyrrhenian coast near Rome, with the aim to relate the distribution of aquatic plants to environmental variables, and to define the botanical conservation value of ponds. Throughout the study period (Spring 2002), Principal Component Analysis performed on abiotic variables clearly discriminated temporary ponds, smaller and more eutrophic, from permanent ponds, larger and with higher pH and oxygen concentration. A total of 73 macrophyte taxa were collected in the study ponds. Temporary waters hosted a smaller number of plant species than permanent ones. Besides hydroperiod length, the environmental factors related to plant richness were maximum depth, surface area, dissolved oxygen and nitrogen concentration in the water. Moreover, the Non-metric Multidimensional Scaling showed a high dissimilarity in the taxonomic composition of aquatic plants between temporary and permanent ponds. The former contained more annual fast-growing species (Callitriche sp. pl. and Ranunculus sp. pl.), while in the latter species with long life-cycles (i.e. Potamogeton sp. pl.) were more abundant. Our results highlighted that temporary and permanent ponds in central Italy have different macrophyte assemblages, with aquatic species (including some of conservation interest at regional scale) exclusively found in each pond type. This suggested that both type of ponds could give an irreplaceable contribution to the conservation of aquatic plant diversity of these freshwater ecosystems.

Chironomids (Diptera: Chironomidae) from Three Temporary Ponds of Different Wet Phase Duration in Central Italy

ABSTRACT A one year-study on three temporary ponds in Central Italy examined relationships between the composition and structure of chironomid communities and some environmental variables. The three ponds showed differences in wet phase duration, dissolved oxygen content, and sediment organic matter. In the pond with longer aquatic phase and lower oxygen content a dominance of Chironominae (mainly Chironomus thummi gr. and C. plumosus gr.) and Tanypodinae (mainly Psectrotanypus varius) was recorded, whereas in the pool with shorter habitat duration and higher oxygen content, Orthocladiinae [mainly Psectrocladius (Allopsectrocladius) spp. and Cricotopus sylvestris] were dominant. The pond with an intermediate wet phase length showed some characteristics common to the other two ponds. The preferences of chironomids for ponds of different habitat duration can probably be ascribed to their larval size and strategies to survive in ephemeral waters. A more detailed analysis of chironomids of the pond with longe...

Biological traits of European pond macroinvertebrates

Whilst biological traits of river macroinvertebrates show unimodal responses to geographic changes in habitat conditions in Europe, we still do not know whether spatial turnover of species result in distinct combinations of biological traits for pond macroinvertebrates. Here, we used data on the occurrence of 204 macroinvertebrate taxa in 120 ponds from four biogeographic regions of Europe, to compare their biological traits. The Mediterranean, Atlantic, Alpine, and Continental regions have specific climate, vegetation and geology. Only two taxa were exclusively found in the Alpine and Continental regions, while 28 and 34 taxa were exclusively recorded in the Atlantic and Mediterranean regions, respectively. Invertebrates in the Mediterranean region allocated much energy to reproduction and resistance forms. Most Mediterranean invertebrate species had narrow thermal ranges. In Continental areas, invertebrates allocated lesser energy to reproduction and dispersal, and organisms were short lived with high diversity of feeding groups. These characteristics suggest higher resilience. The main difference between ponds in the Alpine and Atlantic regions was their elevation. Alpine conditions necessitate specific adaptations related to rapid temperature fluctuations, and low nutrient concentrations. Even if our samples did not cover the full range of pond conditions across Europe, our analyses suggest that changes in community composition have important impacts on pond ecosystem functions. Consistent information on a larger set of ponds across Europe would be much needed, but their low accessibility (unpublished data and/or not disclosed by authors) remains problematic. There is still, therefore, a pressing need for the incorporation of high quality data sets into a standardized database so that they can be further analyzed in an integrated European-wide manner.

Profundal macrobenthos structure as a measure of long-term environmental stress in a polluted lake

Profundal macrobenthic community in a polluted lake (Lake Nemi, Italy) was analyzed in three distinct surveys from 1976 to 1984, in order to define long-term changes in environmental conditions of sediments. Profundal macrobenthos was mainly composed of Oligochaeta. Only a few Chironomidae and a few other taxa were characteristically found in the superior zone. The long-term stress, due to persistent hypolimnetic O2 deficit, caused progressive simplification of the total community structure. This leads to a high faunal similarity among stations at different depths. The temporal trend of the community structure parameters and the significant role of some taxa (Potamothrix heuscheri, Procladius and Chaoborus flavicans) in the eutrophication process of the lake are also discussed.

Macroinvertebrates and environmental factors of some temporary and permanent ponds in Italy

Temporary and permanent ponds provide suitable habitats for a very wide range of aquatic plant and invertebrate species, often including endangered and/or nationally rare ones (BIGGS er al. 1994). However, these types of freshwaters have tended to disappear due to changes in land use and building development, with a serious loss of local biological diversity. In particular, species having specific biotope preferences are threatened by increasing landscape disturbance and fragmentation. For these reasons, scientific interese in these small freshwater bodies has increased over the past decade, with an increasing focus on their classification, conservation and management (GROWNS er al. 1992, VERDONSCHOT 1992, BIGGS et al. 1994, COLLINSON et al. 1995).

Ecological Requirements of Chironomids (Diptera: Chironomidae) on the Soft Bottom of the River Arrone, Central Italy

ABSTRACT The distribution and abundance of soft bottom chironomids in an organically polluted lowland river of Central Italy were investigated relative to correlations with physicochemical parameters of the water and sediments. Chironomus were the dominant tribe in the river with the highest density at the most polluted stations. Chironomus riparius showed the highest annual mean densities at the very highly polluted station, where it was the dominant species in late spring and summer. At the same station, Micropsectra sp., Polypedilum breviantennatum, Cryptochironomus sp., Harnischia sp. and Cricotopus bicinctus replaced C. riparius in winter, when the environmental conditions improved slightly. Densities of all the above mentioned taxa generally showed a positive correlation with the orthophosphate and BOD5 contents and a negative correlation with the oxygen content. C. riparius, Micropsectra sp. and Harnischia sp. preferred fine sediments (silt/clay and very fine sand) with high organic matter content, whereas P. breviantennatum was mostly confined to sandy stations. Robackia demejerei, Acalcarella sp., Rheosmittia spinicornis and Paracladopelma cloris group were present and/or abundant exclusively at unstable sandy stations with summer regulation of the water. Principal Component Analyses based on chironomid densities seems to provide an integrated response to the effects of both physical (hydraulic stress and granulometric composition of the sediment) and chemical characteristics (organic pollution) of the river.

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.

Functional Feeding and Habit Organization of Macroinvertebrate Communities in Permanent and Temporary Ponds in Central Italy

ABSTRACT The organization of functional feeding groups and habits of the invertebrate macrofauna was studied in twenty temporary and permanent ponds located in a natural reserve near Rome in order to complete the knowledge of the most relevant ecological aspects of this community, which was recently analyzed from a taxonomic perspective. Collector-gatherers, predators, sprawlers + climbers, and burrowers dominated in the ponds. Few differences between temporary and permanent ponds were evident in functional feeding groups and habits. Only collector-filterers (bivalves and some chironomids) seemed to be negatively influenced by drought, as they were more abundant in the permanent ponds. Scrapers appeared to be negatively influenced by tree cover and positively by conductivity and macrophyte cover. The abundances of sprawlers and climbers were negatively influenced by tree cover and positively by macrophyte cover, whereas swimmers and divers were positively influenced by pond depth.

Seasonal changes of the profundal macrobenthic community in a polluted lake

Late summer and winter structures of the profundal macrobenthos in a polluted lake (Lake Nemi, Central Italy) were compared to verify the relative differences in the faunal structure and the magnitude of the winter recovery of this community. Densities of Oligochaetes and Chironomids did not vary significantly from summer to winter, the latter not showing any recolonization of the profundal zone. Structure and diversity of the total fauna, and Oligochaete/Chironomid ratio were very similar in the two periods. Our results suggest that in a severely polluted lake, with a strong and lasting oxygen deficit in the hypolimnic zone, a lack of recovery of profundal macrobenthos may be expected in improved environmental winter conditions.