First assessment of the macrozoobenthic community of Ragogna lake

Amelmann V.(1), Piazza G.(2), Incerti G.(1), Panico S.(1), D’Aietti A.(2), Macor A.(2), Rancati R.(2), Sinesi S.(2), Virgilio D.(2), Zanut E.(2), Zorza R.(2), Bressan E.(2) & Zanello A.(2)
(1) University of Udine, Department of Agrifood, Environmental and Animal Sciences, Via delle Scienze 206, 33100 Udine, Italy (2) ARPA FVG (Regional Agency for Environmental Protection Friuli Venezia-Giulia), Via Cairoli 14, 33057 Palmanova (UD), Italy

According to the WFD 2000/60/EC, implemented in Italy by Legislative Decree n. 152/06, the definition of the environmental status of surface waters is necessary to implement measures of water bodies protection. The ecological status of a lake is evaluated using Biological Quality Elements (QBE). Among QBEs, benthic macroinvertebrates are recommended due to their known responses to different environmental drivers. However, benthic macroinvertebrates are commonly used as indicators of the biological condition for rivers, while their use in small lakes is much less studied. The aim of this work was to provide a first detailed overview of the macrozoobenthic community of the Ragogna lake (San Daniele, Udine) the only example of morainic lake in Friuli Venezia Giulia, based on fieldwork carried out by ARPA FVG in 2017 and 2022. The biodiversity of this community was described in terms of composition, density and species richness and the community structure was explored with techniques of multivariate analysis and inferential statistics. Results showed that the composition dynamics and changes in population density mostly rely on the sampling year and season. The concentration of dissolved oxygen plays the main role in selecting the presence and abundance of the different taxa. Differently, species richness is substantially unaffected by seasonal dynamics across the whole observation period. The first application of the Benthic Quality Index for Italian Lakes (BQIES) to the Ragogna Lake classified its ecological status as "bad", as related to the lake eutrophication. A comparison of this study outcomes with those carried out on the same typology lakes in NW Italy (AL5 - Shallow and stratified subalpine lakes) showed similar BQIES values due to the perilacual conditions, in addition to the biotic and abiotic characteristics of the lakes.

Keywords: Ecological status, benthic macroinvertebrates, biodiversity, Ragogna lake, eutrophication

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