| Abstract | We report here the results of two studies on the impact of climate change, particularly of warming, carried out in a lake (Lake Maggiore) where eutrophication and re-oligotrophication were previously analyzed. These studies allow validation of the hypothesis that global warming would produce eutrophication-like effects on plankton communities. They also provide an opportunity to assess the relationship between climate warming and trophic status, and to verify that the climatic signal is more evident in remote sites because it is not overwhelmed by the nutrient enrichment signal, that predominates in eutrophic systems. In systems for which longterm data allow for the definition of a baseline situation, the impact of exceptional meteorological conditions can be assessed, using a "quasi-experimental" approach, comparable, as for results, to in situ experiments. The following annual response to ambient temperature was mediated by trophic dynamics, but was generally an increase in the efficiency of the food chaine one year following warming events. During an exceptionally warm year, however, only the eutrophication-like effect on zooplankton, was apparent, as the population phenology was substantially different from that detected in more productive years. |
| Text | 218946 2008 Zooplankton Eutrophication Climate warming Trophodynamics Exergy Riscaldamento globale exergia, trofodinamica e zooplancton Manca M., Visconti A., de Bernardi R CNR ISE Verbania Pallanza We report here the results of two studies on the impact of climate change, particularly of warming, carried out in a lake Lake Maggiore where eutrophication and re oligotrophication were previously analyzed. These studies allow validation of the hypothesis that global warming would produce eutrophication like effects on plankton communities. They also provide an opportunity to assess the relationship between climate warming and trophic status, and to verify that the climatic signal is more evident in remote sites because it is not overwhelmed by the nutrient enrichment signal, that predominates in eutrophic systems. In systems for which longterm data allow for the definition of a baseline situation, the impact of exceptional meteorological conditions can be assessed, using a quasi experimental approach, comparable, as for results, to in situ experiments. The following annual response to ambient temperature was mediated by trophic dynamics, but was generally an increase in the efficiency of the food chaine one year following warming events. During an exceptionally warm year, however, only the eutrophication like effect on zooplankton, was apparent, as the population phenology was substantially different from that detected in more productive years. Vengono qui brevemente esposti i risultati di due ricerche condotte in un ambiente lacustre Lago Maggiore oggetto di monitoraggio durante la fase di eutrofizzazione e di quella, piu recente, di oligotrofizzazione, nel quale l impatto dei cambiamenti climatici, ed in particolare del riscaldamento globale, e stato documentato. Ricerche di questo tipo forniscono le informazioni necessarie per discutere la validita dell ipotesi secondo la quale gli effetti del riscaldamento sulle comunita planctoniche sarebbero pienamente sovrapponibili a quelli che si osservano con l eutrofizzazione, e di verificare se la risposta al riscaldamento non sia maggiore, e non solo maggiormente leggibile, in sistemi a bassa trofia e, piu in generale se, ed in che misura, essa possa dipendere dalle condizioni trofiche del sistema. Lo studio dell impatto del clima su ambienti oggetto di ricerche intensive consente, tra le altre cose, di distinguere l eccezione dalla regola, e di utilizzare i dati relativi ad anni eccezionali dal punto di vista meteo climatico come veri e propri esperimenti in situ. Le ricerche sul Lago Maggiore hanno evidenziato, da un lato, come la dipendenza dell efficienza della catena trofica pelagica dalla temperatura ambientale sia mediata per il tramite delle relazioni trofiche, e governata, quanto a tempi di risposta, dalla fauna ittica. Dall altro, hanno consentito di mettere in luce come la sovrapposizione tra riscaldamento ed eutrofizzazione sia in realta solo apparente, essendo la fenolo gia delle popolazioni zooplanctoniche sostanzialmente mutata, anche in questo caso per il tramite di meccanismi trofodinamici. 22 Published version Biologia Ambientale 2008_B0_021.pdf Articolo in rivista C.I.S.B.A. 1129 504X Biologia ambientale Biologia ambientale Biol. ambient. VISCONTI ANNA DE BERNARDI RICCARDO marinamarcella.manca MANCA MARINA MARCELLA DG.RSTL.094.009 Evoluzione della biodiversita e valutazione della banca degli stadi duraturi di organismi acquatici di laghi remoti |
