Shorter blooms expected with longer warm periods under climate change: an example from a shallow meso-eutrophic Mediterranean lake

AbstractSatellite data from the Climate Change Initiative (CCI) lakes project were used to examine the influence of climate on chlorophyll-a (Chl-a). Nonparametric multiplicative regression and machine learning were used to explain Chl-a concentration trend and dynamics. The main parameters of importance were seasonality, interannual variation, lake level, water temperature, the North Atlantic Oscillation, and antecedent rainfall. No evidence was found for an earlier onset of the summer phytoplankton bloom related to the earlier onset of warmer temperatures. Instead, a curvilinear relationship between Chl-a and the temperature length of season above 20°C (LOS) was found with longer periods of warmer temperature leading to blooms of shorter duration. We suggest that a longer period of warmer temperatures in the summer may result in earlier uptake of nutrients or increased calcite precipitation resulting in a shortening of the duration of phytoplankton blooms. The current scenario of increasing LOS of temperature with climate change may lead to an alteration of phytoplankton phenological cycles resulting in blooms of shorter duration in lakes where nutrients become limiting. Satellite-derived information on lake temperature and Chl-a concentration proved essential in detecting trends at appropriate resolution over time

Indici per la valutazione della qualit? ecologica dei laghi

Collection of methods to evaluate lake quality using biological element

The Diatomic Diversity of Two Mediterranean High-Elevation Lakes in the Sibillini Mountains National Park (Central Italy)

Temporary high-elevation lakes represent vulnerable and unstable environments strongly threatened by tourism, hydrogeological transformations and climate changes. In-depth scientific knowledge on these peculiar habitats is needed, on which to base integrated and sustainable management plans. Freshwater diatoms, thanks to their high diversity and their particular sensitivity to the water chemistry, can be considered powerful ecological indicators, as they are able to reflect environmental changes over time. The aim of the present study was to analyze the diatomic diversity of the Pilato and Palazzo Borghese lakes, two small temporary high-mountain basins, falling in a protected area within the Apennine mountains chain (central Italy). Diatoms data were collected, at the same time as 12 physicochemical parameters, through six microhabitat samplings, from 17 June to 30 August 2019. In both lakes, a total of 111 diatomic species and varieties were identified. The most species-rich genera were Gomphonema, Navicula, and Nitzschia. The Pilato Lake showed a diatomic community dominated by few species, favored by more stable and predictable environmental conditions than the Palazzo Borghese Lake, which hosted a more diversified community, guaranteed by greater spatial and temporal heterogeneity. Both lakes were characterized by the presence of diatomic species typical of good quality waters. The occurrence of numerous aerial species reflected adaptation strategies adopted to colonize environments subjected to extended drought periods. Endangered diatomic species of particular conservational interest were recorded, confirming the need to preserve their habitats

Mediterranean river biomonitoring in Central Italy: Diatom biodiversity and characterization of communities

Abstract In compliance with the European and Italian regulations, the Environmental Protection Agency of Umbria Region (ARPA Umbria) defined specific river monitoring programs and networks based on river type definition, human pressures and risk analysis. The Umbria Region lies in Central Italy and it can be split into three hydro-ecoregions belonging to the Mediterranean area. Data on diatom community composition were collected in five different Mediterranean macrotypes (M1-M5) throughout the diatom-based river monitoring network that is composed by 52 sampling stations in 36 watercourses. The main aim of this study was to characterise and to analyse diatom diversity across the different regional river macrotypes. Specifically, we investigated if: i) there were differences in species diversity (species richness and Shannon Index) among macrotypes; ii) there was difference in three water quality indexes (ICMi, IPS, and TI) among sites; and iii) there was a relationship between the observed ICMi, IPS and TI value and the diatom diversity. Two-hundred diatom species and varieties were identified, and the number of species per sampling station ranged from a minimum of 10 to a maximum of 38 species. The most frequent and abundant species were Amphora pediculus, Achnanthidium minutissimum, Navicula cryptotenella, Nitzschia dissipata, and each macrotype showed some peculiar species. The ecological status evaluation based on Intercalibration Common Metric Index (ICMi) classified 69% of the water bodies in high or good class. Significant differences in diversity and ICMi value among stream macrotypes were found, with M4 (small and medium mountain) and M5 (small, lowland, temporary) typologies showing the lowest species richness, and with M5 showing the lowest Shannon Index. Conversely, M2 (small and medium lowland) and M5 showed the highest ICMi value. Lastly, significant correlations between Shannon Index and the ICMi, IPS and TI indexes were found