Chironomid populations (Insecta-Diptera) are considered particularly relevant in freshwater environments because they are widely distributed and they are important components of the benthic food chain. Tolerant species present high densities under eutrophic conditions. In recent years, Lake Trasimeno (Central Italy) has been affected by massive chironomid swarms. Lake Trasimeno is the largest Italian shallow lake (max depth 6 m) and the fourth largest Italian lake in surface. Aim of the study was to monitor the littoral chironomid populations of Lake Trasimeno. From October 2005 to September 2013, about 13000 chironomid larvae, sampled along the littoral of Lake Trasimeno (Castiglione del Lago), have been examined. Samplings of substrate have been carried out with a hand-dredge (14x8 cm) for low profundity, along a sector of 350 m at about 1.5 m depth, and each monthly investigation consisted of at least 30 samples of substrate. The survey in the ten years of study (46 monthly investigations) revealed the presence of 14 taxa (average of about 9 taxa), of these the most abundant were: Polypedilum (32.5%), Chironomus plumosus (17.5%) Cladotanytarsus (13.7%) and Stictochironomus (12.1%). These taxa presented an average density respectively of 238.47 n/m2, 127.61 n/m2, 101.65 n/m2 and 91.96 n/m2. Overall the average density of chironomids was of 740.87 n/m2 (43.7%), while oligochaetes had an average density of 873.93 n/m2 (54.9%). Thus, these two groups represented about the 99% of the whole macroinvertebrate community of the littoral station of Lake Trasimeno. The Shannon Index (H) applied to the littoral chironomid community amounted to an average of 1.33, while the Equitability Index to 0.62. Therefore, chironomids concur as determinant to the biodiversity and productivity of the ecosystem of Lake Trasimeno. In conclusion, this study provided further support for the application of chironomids, as biological indicators, in monitoring programs for the aquatic ecosystem management.
Monitoring of the littoral chironomid populations of Lake Trasimeno (2005-2013)
PALLOTTINI, MATTEO;GORETTI, Enzo
2014
Abstract
Chironomid populations (Insecta-Diptera) are considered particularly relevant in freshwater environments because they are widely distributed and they are important components of the benthic food chain. Tolerant species present high densities under eutrophic conditions. In recent years, Lake Trasimeno (Central Italy) has been affected by massive chironomid swarms. Lake Trasimeno is the largest Italian shallow lake (max depth 6 m) and the fourth largest Italian lake in surface. Aim of the study was to monitor the littoral chironomid populations of Lake Trasimeno. From October 2005 to September 2013, about 13000 chironomid larvae, sampled along the littoral of Lake Trasimeno (Castiglione del Lago), have been examined. Samplings of substrate have been carried out with a hand-dredge (14x8 cm) for low profundity, along a sector of 350 m at about 1.5 m depth, and each monthly investigation consisted of at least 30 samples of substrate. The survey in the ten years of study (46 monthly investigations) revealed the presence of 14 taxa (average of about 9 taxa), of these the most abundant were: Polypedilum (32.5%), Chironomus plumosus (17.5%) Cladotanytarsus (13.7%) and Stictochironomus (12.1%). These taxa presented an average density respectively of 238.47 n/m2, 127.61 n/m2, 101.65 n/m2 and 91.96 n/m2. Overall the average density of chironomids was of 740.87 n/m2 (43.7%), while oligochaetes had an average density of 873.93 n/m2 (54.9%). Thus, these two groups represented about the 99% of the whole macroinvertebrate community of the littoral station of Lake Trasimeno. The Shannon Index (H) applied to the littoral chironomid community amounted to an average of 1.33, while the Equitability Index to 0.62. Therefore, chironomids concur as determinant to the biodiversity and productivity of the ecosystem of Lake Trasimeno. In conclusion, this study provided further support for the application of chironomids, as biological indicators, in monitoring programs for the aquatic ecosystem management.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
