Phytoplankton assemblages in Lake Orta: has functional structure recovered in one of the largest acidic lakes in the world?

Lake Orta (Northern Italy) became one of the world\u27s largest acidic lakes, following industrial pollution, beginning in the late 1920s. Prior to pollution, Lake Orta supported a rich and diversified phytoplankton community dominated by diatoms, cyanobacteria and dinoflagellates. Their taxonomic composition was comparable to that of the nearby Lake Maggiore, which provides a useful reference comparison. After pollution, Lake Orta was so acidic and contaminated with trace metals that only a few tolerant phytoplankton species persisted, supplemented by sudden and short living outbursts of occasional colonists. The lake was limed in 1989-1990. This has permitted the gradual recovery of its chemistry and biology, and many phytoplankton species that inhabit Lake Maggiore are now re-appearing in Lake Orta. I tested the two hypotheses that Lakes Orta and Maggiore would now have a similar phytoplankton taxonomic assemblages, and similar diversity of functional groups given their similar morphometry, physical features and trophic states. The two hypotheses were tested by comparing the phytoplankton assemblages of lakes Maggiore and Orta for the first 10 years after liming, i.e. 1990 to 2001. Phytoplankton was classified according the Reynolds\u27 Morpho Functional Groups and five diversity indices were calculated (S, number of units; H, Shannon-Wiener; E, evenness; D, dominance; J, equitability). SHE analysis (an analysis of diversity changes based on the relationship among species richness (S), H Index (H) and evenness (E)) was also carried out, in order to compare the long term trend of both functional groups and taxa biodiversity. Both taxonomic and the functional composition differed in the two lakes, likely because chemical quality have played a role in taxaselection. Moreover, it was quite clear that, during the first post-liming decade, Lake Orta\u27s phytoplankton was characterized by low diversity and evenness and by marked year-to-year fluctuations. However, SHE analysis showed that the colonization rate was higher in Lake Orta than in Lake Maggiore, and that the environmental modifications caused by the liming were opening new ecological niches, allowing some colonists to thrive in the changing, albeit still unusual chemical environment of the lake

Lake Orta 25 years after the liming intervention: what phytoplankton assemblages could tell us about the recovery of the largest acidic lake in the world

Lake Orta (N. Italy) became the world\u27s largest acidic lake, after a dramatic industrial pollution, dating back to the late 1920. The lake was limed in 1989-1990: since then, a recovery of the chemical and biological conditions gradually took place. Concerning phytoplankton, the gradual decrease of the chlorophytes and the noticeable increase of the diatoms, reappearing in the pelagic phytoplankton after decades, were the most outstanding features of the post-liming assemblages. However, the most recent study, carried out in 2001, pointed out that, comparing the assemblages of lakes Orta and Maggiore, the complete recovery was not yet reached. In particular, a decadal comparison (1990-2001) beetwen the two ecosystems, shows that, although the taxa number increased in Lake Orta after the liming, some differences in terms of functional diversity are clear. Since 2011 detailed taxonomic analyses are lacking. However, between 2005 and 2013 bsome samples analysed in both lakes, using in vivo fluorimetry, show that the dominance of chlorophytes is still a distinctive trait of Lake Orta, although the importance of the diatoms is now greater than in previous years and their dynamics is following a pattern comparable with that observed in Lake Maggiore

Ricerche sull\u27evoluzione del Lago Maggiore. Aspetti limnologici. Programma triennale 2013-2015. Campagna 2013

Not availableRicerche sull\u27evoluzione del Lago Maggiore. Aspetti limnologici. Programma triennale 2013-2015. Campagna 201

Struttura dei popolamenti fitoplanctonici

Not availableStruttura e studio della distribuzione orizzontale dei popolamenti fitoplanctonici; Variazioni della biomassa algale; Variazioni della distribuzione spaziale dei popolamenti fitoplanctonic

Lago Maggiore oligotrophication as seen from the long-term evolution of its phytoplankton taxonomic size structure

Due to the rapid and common deterioration of aquatic ecosystems, scientists and environmental protection organizations acutely need means capable of producing quantitative estimates for structural deformations of natural communities. Recently, very common biomass size spectra ignore community taxonomic composition, i.e., one of the most important kinds of biological information. Therefore, another very old, but rare in planktonology, method - the traditional taxonomic size spectrum (TTSS) - can be helpful. TTSS, a specific form of size-frequency distribution of taxonomic units, reveals repeating patterns of deep subalpine Lago Maggiore (Italy) phytoplankton taxonomic structure. The general TTSS pattern was safeguarded during 22 annual cycles (1984-2005), when many principal environmental characteristics were changed considerably during the lake oligotrophication. At the same time, the fine structure deformations of this pattern helped us divide the total oligotrophication process into several stages characterized by notable changes of TTSS peaks\u27 proportions. These peak-height alterations were caused by pronounced changes in the species list and overall taxonomic diversity of the lake phytoplankton. The average cell volume decline was found. It was significantly correlated with the total phosphorus descending trend. This cell volume decline was produced by the addition of numerous species into the medium-and-small size fractions. Typical patterns of the stable and transitory stages were differentiated, which could be valuable for environmental protection and diagnostic applications. The central peak height difference between the stable and the transitory periods was statistically significant. Oligotrophication process decomposition into several more homogenous groups of years was supported by quantitative estimators produced by hierarchical cluster analysis. The highest level of the similarity measure (Pearson r) in pairs of annual TTSS was close to the respective estimates found for other lakes. Concomitantly, its minimal level, produced by a specific pair of abnormal years at the beginning and end of the studied process, was found previously only for pairs taken from two different ecosystems (Lakes Kinneret and Tahoe). This way, TTSS can be applied as a quantitative analysis means of the integral natural community structural evolution. Such tools are acutely needed for environmental management, monitoring, and theoretical ecology

Analisi comparativa in termini di system-gate equivalenti fra diverse tecnologie FPGA utilizzando un processore FFT come riferimento

Analisi comparativa in termini di system-gate equivalenti fra diverse tecnologie FPGA utilizzando un processore FFT come riferiment

Long-term research to understand impact of perturbations on lakes: the example of Lake Maggiore

Perturbations linked to the direct and indirect impacts of human activities during the so-called Anthropocene, affect the structure and functioning of lake ecosystems to varying degrees. To understand the patterns and mechanisms of these anthropogenic effects and the extent to which they may drive irreversible changes in ecosystem services, long-term research is required. Studies on the long-term dynamics of plankton may be particularly useful for large and deep lakes whose overall productivity is dominated by pelagic processes. In the open-waters of such lakes, planktonic organisms link and interact with both abiotic and biotic compartments. Here we will analyze 60 years of data on the plankton of the large, deep, subalpine, Lake Maggiore, tracing changes in the pelagic food web which occurred during different phases of the lake\u27s recent evolution. We will document short- to- medium response times by different trophic levels, from microbes, to primary producers and secondary consumers. We will revisit results of past studies based on contemporary and paleolimnological studies and present new analyses to: i) identify any tipping points of the lake trophic evolution, ii) discern effects of recent climatic change, iii) quantify whether inter-annual variability has changed perhaps in responses to changes in thermal stratification regime and warming. By supplementing structural with functional descriptions of long term changes in phyto- and zooplankton communities, we aim to test competing mechanisms underpinning the decade-scale changes we observed

Functional classification of phytoplankton: materials and methods for developing non-taxonomic quality indices

No abstract availableTra le maggiori difficolt? nell\u27utilizzo degli indici biotici basati sulla composizione in specie delle comunit? fitoplanctoniche, vi ? quella di classificare correttamente, dal punto di vista tassonomico, gli organismi rinvenuti. Per superare, almeno in parte, questa difficolt?, ? possibile ricorrere ad una classificazione su base morfo-funzionale, invece che tassonomica. La classificazione funzionale si fonda sulla relazione che lega le propriet? morfologiche e fisiologiche delle cellule algali alla loro risposta ai gradienti dei parametri ambientali: in teoria, dunque, ? possibile sviluppare indici di qualit? per la classificazione dei corpi idrici, basati su una classificazione morfo-funzionale degli organismi fitoplanctonici. Nella presentazione viene spiegato come si ? arrivati a sviluppare un indice di qualit? morfo-funzionale e come quest\u27ultimo abbia una performance comparabile a quelle di indici tradizionali, basati sulla classificazione tassonomica. Infine, vengono illustrati recenti sviluppi sullo studio delle relazioni tra alcuni tratti funzionali del fitoplancton lacustre e la composizione delle comunit? a scala europea

Phytoplankton configuration in six deep lakes in the peri-Alpine region: are the key drivers related to eutrophication and climate?

The aim of this study was to draw a general picture of the phytoplankton community in peri-Alpine lakes, including for the first time a broad data set of six deep peri-Alpine lakes, belonging to the same geographical region. The objective was to define the main key drivers that influence the phytoplankton community composition in this particular vulnerable region, for which the impacts of climate change have been demonstrated to be stronger than on a global average. The phytoplankton was investigated with a particular focus on cyanobacteria and using a classification approach based on morpho-functional groups. We hypothesized that phytoplankton in peri-Alpine lakes is mainly driven by nutrient loads as well as by water temperatures, variables that are strongly influenced by climate change and eutrophication. Though different phytoplankton configurations among lakes were partly due to their geographical (altitude) position, assemblages were mostly linked to temperature and nutrients. Furthermore, the results confirmed the significant role of the spring fertilization on the seasonal phytoplankton development. Cyanobacteria were related to the increasing annual average of air and water temperature gradient and therefore might become more important under future warming scenario. Air temperatures have a significant impact on water temperature in the uppermost meters of the water column, with a stronger influence on warmer lake