In memory of Oscar Ravera

Oscar Ravera was one of the most lively and active protagonists in the field of ecology. A man of great culture, Oscar had a genuine interest in knowledge, an interest fed by his insatiable childlike curiosity. Arriving young, at Pallanza, he found fertile ground to develop his passion for aquatic ecology, a passion that led both to important scientific achievements, and to very large-scale initiatives..

Selectivity of plankton nets over mesozooplankton taxa: implications for abundance, biomass and diversity estimation

The importance of the smaller copepod species is often underestimated as a result of the use of standard 200 μm mesh size nets, even though the small copepods probably represent the dominant component of the mesozooplankton community. Although the inadequacy of relatively coarse nets in providing reliable descriptions of the mesozooplankton assemblage is increasingly welldocumented, such nets continue to be commonly used. A major reason for this unwillingness to break with tradition is the belief that samples remain comparable even though the absolute values are biased. A one-year study of the abundance and size distribution of zooplankton collected in the Venice Lagoon using an 80 μm mesh size net showed an overwhelming abundance of small taxa. These data were used to derive estimates of the mesh selection effects of standard WP-2 nets on zooplankton abundance and biomass. Only 11% of numbers and 54% of biomass of lagoon zooplankton are likely to be caught with standard WP-2 nets. A comparison of seasonal changes in diversity, estimated from the fine and coarse datasets, confirmed that retention efficiency is seasonally dependent, which results in serious implications when extrapolating temporal patterns in community structure from WP-2 mesozooplankton counts

Seasonal variations in population dynamics and biomass of two Unio pictorum mancus (Mollusca, Unionidae) populations from two lakes of different trophic state

Samples of Unio pictorum mancus collected monthly from spring 2003 to summer 2004 in the meso-oligotrophic Lake Maggiore and the eutrophic Lake Candia were compared to evaluate the influence of lake trophic conditions on mussel populations. Shell form, maximum age (8 years) and percentage of organic matter in the shell and soft tissues were similar in both lakes. However, comparisons between same size classes revealed that mussels from Lake Maggiore were generally older, their shells heavier and their soft tissues lighter than those from Lake Candia. Recruitment occurred in both populations in June-July. The frequency distributions of adult mussels (>30 mm) and their soft tissues and shell biomasses in all size classes (range = 2 mm) were normal, but the curves of the mussels from Lake Candia were flat in comparison to those of mussels from Lake Maggiore. The median body size of Lake Maggiore mussels was 58 mm, while that of the Lake Candia population was 72 mm. During the study period the population density of each lake was fairly constant, whereas the population structure, and consequently the biomass, showed seasonal variations. The greatest differences were found between population density and shell and tissue biomass of the two populations, which were respectively 46.86 ind. m-2; 408 g d.w. m-2 and 38.67 g d.w. m-2 in Lake Maggiore, and 6.93 ind. m-2; 92.29 g d.w. m-2 and 14.04 g d.w. m-2 in Lake Candia. These values testify to the phenotypical plasticity of Unio pictorum mancus in relation to environmental characteristics, without excluding a possible genetic influence as a result of geographical isolation and the respective selection mechanisms. The influence exerted by the lake trophic level and by the physical environment on some population characteristics is discussed

When and how? Freshwater mussel recolonization in Lake Orta

Thanks to a video posted on a social network, live mussels of Unio elongatulus, have been recorded from Lake Orta (Italy) over one century after the last (and only) report. With its long and well documented history of pollution, Lake Orta offers the opportunity to document the post-extirpation recovery of freshwater unionid mussels. This case evidences that recovery/recolonization is possible despite a high devastation in the past, and permits to evaluate how fast recolonization may occur, in which way, and in what conditions. The answer to the \u27how fast\u27 was sought by estimating the age of the larger and seemingly older individuals of the population. To address the \u27in which way\u27 we compared the haplotypes of Lake Orta specimens of Unio elongatulus (the only species present) with those of surrounding populations. We concluded that, since Lake Orta lacks a direct connection with the putative source populations, colonizing mussels were almost certainly transported by fish carrying glochidia that were used for lake restocking after liming. Data from the long-term monitoring of water chemistry and sediments have allowed defining what conditions proved to be suitable for survival making possible the start of mussels recovery. But not only water and sediment quality matters for mussels recovery, which was delayed by nearly ten years after the reappearance of fish. This delay reflects the need of the whole trophic chain to be reestablished to allow the survival of the suitable and healthy host-fish populations necessary for mussels reproduction

Discrimination of freshwater fish species by Matrix-Assisted Laser Desorption/Ionization- Time Of Flight Mass Spectrometry (MALDI-TOF MS): a pilot study

In this study we discriminate three freshwater fish species (the shad Alosa agone Scopoli 1786, the whitefish Coregonus macrophthalmus N?sslin1882 and the roach Rutilus rutilus Linnaeus 1758) by Matrix-Assisted Laser Desorption/Ionization- Time Of Flight Mass Spectrometry (MALDI-TOF MS) using both muscle and liver tissues. The technology enables to analyze tissues after a simple single-step extraction procedure without any further purification. The molecular profile of muscle tissues showed the most intense peaks at m/z range of 11,354.0 (?2.0 SD) Da, 3508.5 (?1.5 SD) Da and 8567.2 (?1.1 SD) Da for the shad, the whitefish and the roach respectively. The molecular profiles of liver tissues exhibit most of the highest peak intensities in the range between 2000 and 6000 m/z values. The roach shows the clearest pattern with high intensities detected at mass ranges between 3000 and 3550 Da with maxima at m/z 3035.2 (?0.2) Da and 3468.7 (?0.3) Da. The shad shows a shared high peak at m/z 3429.0 (?0.3) Da. The whitefish shows a group of major peaks in the m/z range of 3000-3700 Da with the highest being at 3635 (?0.3) Da. The overall signal pattern generated is highly specific for each species and, according to cluster analyses based on the total number of peaks, we could discriminate the three species

Seasonal variations in metal content of two Unio pictorum mancus (Mollusca, Unionidae) populations from two lakes of different trophic state

To assess the impact of lake trophy on trace element accumulation by Unio pictorum mancus, a population from the mesooligotrophic Lake Maggiore was compared with a population from the eutrophic Lake Candia. The element content in soft tissue and shell biomass, the seasonal variations of element concentrations in soft tissues and shell, and the relationship between element concentrations in the water and those in the tissues were estimated in pursuit of this objective. Thirteen mussel samplings were performed in Lake Maggiore between May 2003 and September 2004 and in Lake Candia between June 2003 and August 2004. Filtered water samples were collected seasonally. Water, shell and soft tissue samples were analysed by ICP-OES and ICP-MS for the measurement of following elements: Zn, Cu, Fe, Mn, Ni, As, Pb, Co, Cr, Mo, V, Cd, Be and Ca. The element concentrations in the mussel tissues and shell from Lake Maggiore were higher than those from Lake Candia. Due to the higher population density and higher element concentrations in the mussels of Lake Maggiore, the element content in the biomass per m2 in this lake far exceeded that in Lake Candia

The role of social networks and citizen science in environmental research: the unexpected revival of freshwater mussels in Lake Orta

Social networks are increasingly used for many conservation and environmental educational purposes. The usefulness for ecological studies is exemplified by the casual discovery of the recovery of freshwater mussels in Lake Orta. Mussels were extirpated by severe industrial pollution soon after 1926 and over the following decades their recovery was prevented by acidification and increase of metal concentrations. Even after the improvement of water conditions obtained by limning, the lack of mussels was taken for granted based on the legacy effects of accumulated toxins in the sediments, and on the limited potential for most extirpated species of mussels to naturally recolonize. The probability of mussel\u27s recovery in Lake Orta was considered poor also for the apparent lack of access to restocking populations, which is essential to start the natural recolonization of an area. Because of the assumption that mussels were absent and of the difficulties of locating mussels their recolonization went unnoticed for about 15 years. Only in 2014 the casual discovery of mussels in Lake Orta was made possible thanks to an amateur video posted on YouTube and delivered to one of us through Facebook: this highlights once more the potential role of social networks for conservation and environmental issues. Freshwater mussels are challenging to locate because they are often rare, spatially clustered, and difficult to detect. The recolonization of Lake Orta went unnoticed probably due to the limited extent of the colonized area, low density and, at least initially, the small size of individuals. In such cases the contribution of citizen science can be crucial to provide the reporting even of small populations present in restricted areas and/or not easily accessible. An extensive search along the lake perimeter is being performed through the volunteer collaboration of local SCUBA divers and an online survey through social networks

Potential of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the identification of freshwater zooplankton: a pilot study with three Eudiaptomus (Copepoda: Diaptomidae) species

The accurate identification of individuals in zooplankton samples is a crucial step in many plankton studies. Up to now, this has been done primarily by microscopic analysis of morphological characters, and new molecular methodologies are still relatively rarely applied. Another promising technology is matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), which has had a major impact in applied and systematic microbiology, where it is used for routine high throughput identification of bacteria and fungi. For the present study, we developed a protocol for the rapid acquisition of mass spectra from whole individual copepods. The final protocol enabled us to obtain mass spectra with more than 100 distinct peaks in the mass range of 2000-20 000 Da. A comparison of the mass spectra of three species of Eudiaptomus showed that they could all be clearly discriminated, whereas the mass spectra of different developmental stages and sexes of each particular species were highly similar. Further, a discrimination of con-specific individuals from different habitats was achieved, at least partly, even without extensive optimization of the analytical and statistical procedures. These results indicate the feasibility of identifying copepods by a rapid and simple MALDI-TOF MS analysis, e.g. for population ecology studie

Seasonal variations in population dynamics and biomass of two Unio pictorum mancus (Mollusca, Unionidae) populations from two lakes of different trophic state

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An Introduction to the Project BLASCO - Blending LAboratory and Satellite techniques for detecting CyanObacteria

Algal blooms can have an impact on health care costs, on the costs associated with the treatment of water intended for human consumption and on the tourism industry. The implementation of early warning systems would reduce these costs and the efforts needed to face and control the harmful effects of an algal bloom. A system for monitoring the quality of the waters, which operates on a large scale and at high frequency, would allow to keep under control the evolution of a bloom. The observation by satellite allows such a monitoring: in particular, the project is focused on the development of techniques for the analysis of satellite images, in order to detect the specific phytoplankton species potentially responsible for bloom formation in lakes. To reach this goal, it is necessary to analyse the spectral response characteristic of cyanobacteria and to develop algorithms to be applied to the analysis of satellite images. New calibration algorithms for the interpretation of satellite images will be obtained in lab experiments, using algal cultures. The developed algorithms will be tested through the analysis of remote sensing images, with particular attention to the bloom events occurring in the lakes of Lombardy and Piedmont. Field data on water optical properties and phytoplankton samples will be also collected. Moreover, different approaches will be applied and compared to quantify the amount of cyanobacteria (HPLC, counting, in vivo fluorimetry, spectroradiometry). Among the main results there will be the creation of a dataset of spectral signatures of some cyanobacteria taxa, as well as the development of calibration curves for the qualitative and quantitative estimation of the blooms. In general, we expect that it will be possible to distinguish, in natural conditions, the spectral signatures of cyanobacteria, even at low concentrations and within mixed populations of phytoplankton