Luciana Mastrantuono

Community structure of the zoobenthos associated with submerged macrophytes in the eutrophic Lake Nemi (Central Italy)

Abstract The study refers to the composition of the zoobenthos in submerged macrophytes in Lake Nemi, subject to an organic pollution caused mainly by domestic wastes. The fauna, sampled in five stations in the period 1981/82, was composed of 18 zoological groups, including 60 taxa. Cladocera, represented almost exclusively by the microfiltrator Chydorus sphaericus, constituted by far the dominant group in all stations. Oligochaeta, comprising 14 taxa, was the most diversified group and their maximum percentages ware found in the Genzano village discharge. Other detritivorous groups, such as Chironomidae and Ostracoda were also abundant, while Hydroida and some Cyclopidae were the most common predator organisms. Owing to the eutrophication process, we can observe: a) abundance of species having wide ecological valence; b) low diversification and reduced abundances in most of the zoological groups; c) prevalence of a detritus food chain.

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.

Long-term changes of zoobenthic fauna and submerged vegetation in the shallow Lake Monterosi (Italy)

Abstract Benthic invertebrates and aquatic vegetation were investigated in the volcanic Lake Monterosi with the aim to define the stage of development reached during progressive modifications which occurred in the shallow lake. Increasing trophy and introduction of an exotic plant ( Nelumbo nucifera ) were the key-factors responsible for the rapid qualitative reduction of the macrophyte population and its modification to non rooted plants ( Ceratophyllum demersum ). The invertebrate fauna associated with macrophytes was found to be abundant, diversified (83 taxa) and characterized by high diversity and presence of bioindicators of mesotrophy. Although the zoobenthic community appeared to be positively influenced by the macrophyte-dominated stage, some negative effects of Nelumbo -colonization on the invertebrate fauna indicated that further growth of this plant would cause a rapid change in the lake.

Relative impacts of morphological alteration to shorelines and eutrophication on littoral macroinvertebrates in Mediterranean lakes

Development of effective methods for assessing the ecological status of lakes based on littoral benthic fauna has been hampered by the lack of quantitative data on the relative impacts of key pressures on the benthic community. We used variance partitioning at 126 sites belonging to 14 natural Mediterranean lakes to analyze the pure and shared effects of eutrophication, morphological alterations, microhabitat type, lake morphometry and geographic position on the littoral macroinvertebrate community. The spatial arrangement of the sampling sites was responsible for 9.1% of the total variance in littoral benthic community composition, lake morphometry accounted for 4.3% of variation, and microhabitat type accounted for 3.9%. Communities appeared to be affected primarily by morphological alterations to lake shorelines, and their impact was 2.5 times as important as that of eutrophication. The structure of littoral benthic communities was governed by processes acting at several spatial scales from region to lake scale. Thus, several pressures and the various spatial scales at which these act should be taken into account when implementing methods of assessing lake ecological condition based on littoral benthic invertebrates. Region-specific methods for subalpine and volcanic lakes might enhance the validity of assessment of results of morphological alterations and improve management of those water resources.

Depth-related response of macroinvertebrates to the reversal of eutrophication in a Mediterranean lake: Implications for ecological assessment

A better management of nutrient inflows into lakes has led to an improvement in their conditions (i.e. reversal of eutrophication) and the effects of this on macroinvertebrate communities that inhabit different lake-depth zones is largely unknown. This paper reports a comparison of macroinvertebrate communities living in the eulittoral, infralittoral and sublittoral/profundal zones of Lake Nemi (Central Italy) before and after its natural recovery from eutrophication following the deviation of domestic wastewater. The infralittoral zone responded more rapidly than the other two depth-zones to the improved ecological conditions, as shown by larger differences in community composition between the two periods. In the eulittoral sand, the combined effects of hydromorphological pressures and reversal of eutrophication hindered the biotic response. In the eulittoral and infralittoral zones, typical taxa of mesotrophic waters appeared or increased their abundances after the eutrophication reversal. Benthic invertebrate response was slower in the sublittoral/profundal zone due to deoxygenation that continued to prevail in the deepest area of the lake during summer. However, both tolerant and more sensitive taxa were collected there for the first time. After the reversal of eutrophication, the percentage of molluscan+large crustaceans increased in the infralittoral zone, whereas the oligochaete/chironomid ratio decreased in both sublittoral/profundal and infralittoral zones. Functional feeding metrics (percentages of filter-feeders, collector-gatherers, miners and scrapers/grazers) differently tracked the reversal of eutrophication in the three depth-zones probably according to the effects of the reduction of nutrients on food-web structure influencing macroinvertebrates. Biological Monitoring Working Party (BMWP) and the Average Score Per Taxon (ASPT) seemed to respond to eutrophication reversal only in the sublittoral/profundal zone, where deoxygenation plays a major role as a structuring agent of the community. Our results suggest that the effects of reversal of eutrophication can be better assessed by examining the response of the communities belonging to each zone individually.

Hydrobiology and Fish biology

(1986). Hydrobiology and Fish biology. Bollettino di zoologia: Vol. 53, No. sup001, pp. 93-100.