Progressive increase of temperature and lower rainfall are some of the main climatic changes occurring in the Mediterranean areas. Consequently, lakes of these regions experience an altered hydrologic balance with large water level reductions and/or fluctuations within and between years. Knowledge on the effects of these water level changes on flora and fauna and the development of useful biological indicators are required to assess current condition and forecast future trends. Here, we present the case of a volcanic lake (Bracciano, Central Italy), one of the largest and deepest Italian lakes. The average air temperature in the Bracciano basin increased by 1.5 degrees over the last 30 years while rainfall showed a decreasing trend. Large fluctuations of the water level with annual means differing by more than 1 m occurred in the last 6 years. To infer the possible response of benthic invertebrates to those changes, we sampled the littoral zone in 2 different periods characterised by 'normal' (1998-1999) and 'reduced' (2003-2004) water level. Samples were collected every 2 months using a standard technique at several sites along the lake shore. Secchi transparency, TP and macrophyte abundance were also directly measured or obtained from competent authorities. Results show a reduction of aquatic vegetation coverage mainly at low depth ranges in years of reduced water level. Benthic invertebrates showed a decrease of taxonomic richness and numerical relative abundances, especially because of the marked reduction of all invertebrates strongly associated with macrophytes (mainly chironomids, oligochaetes, nematodes, water mites and gastropods). On the other hand there was an increase of microcrustaceans (cladocerans and copepods) which constituted at some sites as much as 90% of the total assemblage. The implications of those findings for the development of an indicator based on benthic invertebrates and possible effect of water fluctuations on the sublittoral and profundal fauna are also discussed.

Climate change effects on water level variation and the response of benthic invertebrates in a Mediterranean lake (Lake Bracciano, Central Italy) / Solimini, A. G.; Mastrantuono, Luciana; Nõges, P.; Bazzanti, Marcello. - (2005), p. 10. (Intervento presentato al convegno Internat. Workshop on Water level fluctuations in lacustrine systems and prospects of future climate change tenutosi a Costanza nel 11-13 dicembre 2005).

Climate change effects on water level variation and the response of benthic invertebrates in a Mediterranean lake (Lake Bracciano, Central Italy).

A. G. SOLIMINI;MASTRANTUONO, Luciana;BAZZANTI, Marcello
2005

Abstract

Progressive increase of temperature and lower rainfall are some of the main climatic changes occurring in the Mediterranean areas. Consequently, lakes of these regions experience an altered hydrologic balance with large water level reductions and/or fluctuations within and between years. Knowledge on the effects of these water level changes on flora and fauna and the development of useful biological indicators are required to assess current condition and forecast future trends. Here, we present the case of a volcanic lake (Bracciano, Central Italy), one of the largest and deepest Italian lakes. The average air temperature in the Bracciano basin increased by 1.5 degrees over the last 30 years while rainfall showed a decreasing trend. Large fluctuations of the water level with annual means differing by more than 1 m occurred in the last 6 years. To infer the possible response of benthic invertebrates to those changes, we sampled the littoral zone in 2 different periods characterised by 'normal' (1998-1999) and 'reduced' (2003-2004) water level. Samples were collected every 2 months using a standard technique at several sites along the lake shore. Secchi transparency, TP and macrophyte abundance were also directly measured or obtained from competent authorities. Results show a reduction of aquatic vegetation coverage mainly at low depth ranges in years of reduced water level. Benthic invertebrates showed a decrease of taxonomic richness and numerical relative abundances, especially because of the marked reduction of all invertebrates strongly associated with macrophytes (mainly chironomids, oligochaetes, nematodes, water mites and gastropods). On the other hand there was an increase of microcrustaceans (cladocerans and copepods) which constituted at some sites as much as 90% of the total assemblage. The implications of those findings for the development of an indicator based on benthic invertebrates and possible effect of water fluctuations on the sublittoral and profundal fauna are also discussed.
2005
Internat. Workshop on Water level fluctuations in lacustrine systems and prospects of future climate change
04 Pubblicazione in atti di convegno::04d Abstract in atti di convegno
Climate change effects on water level variation and the response of benthic invertebrates in a Mediterranean lake (Lake Bracciano, Central Italy) / Solimini, A. G.; Mastrantuono, Luciana; Nõges, P.; Bazzanti, Marcello. - (2005), p. 10. (Intervento presentato al convegno Internat. Workshop on Water level fluctuations in lacustrine systems and prospects of future climate change tenutosi a Costanza nel 11-13 dicembre 2005).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/235095
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