Abstract:established by the Italian law were not rare and they were found close to the mainland and the main river outflows. The comparison with previous data to update the knowledge on the trophic conditions of the lagoon showed that the overall trophic load is reducing. Only nitrate concentrations did not change.The seasonal samples allowed to confirm the above observations highlighting the behaviour of nutrients in relation to the weather conditions and to the primary producer fluctuations.
“…, Facca et al. , ARPAV, http://www.arpa.veneto.it), we found only one U. pertusa specimen (#LI8) in contrast to the high abundance of this species in the other areas. Recent studies suggest that U. pertusa is a new invasive species (Aguilar‐Rosas et al.…”
Ulva Linnaeus (Ulvophyceae, Ulvales) is a genus of green algae widespread in different aquatic environments. Members of this genus show a very simple morphology and a certain degree of phenotypic plasticity, heavily influenced by environmental conditions, making difficult the delineation of species by morphological features alone. Most studies dealing with Ulva biodiversity in Mediterranean waters have been based only on morphological characters and a modern taxonomic revision of this genus in the Mediterranean is not available. We report here the results of an investigation on the diversity of Ulva in the North Adriatic Sea based on molecular analyses. Collections from three areas, two of which subject to intense shipping traffic, were examined, as well as historical collections of Ulva stored in the Herbarium Patavinum of the University of Padova, Italy. Molecular analyses based on partial sequences of the rbcL and tufA genes revealed the presence of six different species, often with overlapping morphologies: U. californica Wille, U. flexuosa Wulfen, U. rigida C. Agardh, U. compressa Linnaeus, U. pertusa Kjellman, and one probable new taxon. U. californica is a new record for the Mediterranean and U. pertusa is a new record for the Adriatic. Partial sequences obtained from historical collections show that most of the old specimens are referable to U. rigida. No specimens referable to the two alien species were found among the old herbarium specimens. The results indicate that the number of introduced seaweed species and their impact on Mediterranean communities have been underestimated, due to the difficulties in species identification of morphologically simple taxa as Ulva.
“…, Facca et al. , ARPAV, http://www.arpa.veneto.it), we found only one U. pertusa specimen (#LI8) in contrast to the high abundance of this species in the other areas. Recent studies suggest that U. pertusa is a new invasive species (Aguilar‐Rosas et al.…”
Ulva Linnaeus (Ulvophyceae, Ulvales) is a genus of green algae widespread in different aquatic environments. Members of this genus show a very simple morphology and a certain degree of phenotypic plasticity, heavily influenced by environmental conditions, making difficult the delineation of species by morphological features alone. Most studies dealing with Ulva biodiversity in Mediterranean waters have been based only on morphological characters and a modern taxonomic revision of this genus in the Mediterranean is not available. We report here the results of an investigation on the diversity of Ulva in the North Adriatic Sea based on molecular analyses. Collections from three areas, two of which subject to intense shipping traffic, were examined, as well as historical collections of Ulva stored in the Herbarium Patavinum of the University of Padova, Italy. Molecular analyses based on partial sequences of the rbcL and tufA genes revealed the presence of six different species, often with overlapping morphologies: U. californica Wille, U. flexuosa Wulfen, U. rigida C. Agardh, U. compressa Linnaeus, U. pertusa Kjellman, and one probable new taxon. U. californica is a new record for the Mediterranean and U. pertusa is a new record for the Adriatic. Partial sequences obtained from historical collections show that most of the old specimens are referable to U. rigida. No specimens referable to the two alien species were found among the old herbarium specimens. The results indicate that the number of introduced seaweed species and their impact on Mediterranean communities have been underestimated, due to the difficulties in species identification of morphologically simple taxa as Ulva.
“…Concentrations of nutrients in the water column (reactive phosphorus, ammonium, nitrites, nitrates) and in the surface sediments (total nitrogen, inorganic, organic and total phosphorus, and inorganic, organic and total carbon) were determined along with the amount of fines in the sediments (sediment fraction <63 μm). Details for all of the procedures followed are reported in Facca, Pellegrino, Ceoldo, Tibaldo, and Sfriso (), Facca, Ceoldo, Pellegrino, and Sfriso (), Sfriso et al. ().…”
One of the main challenges to facilitate the classification of water bodies is to identify direct relationships between anthropogenic pressures and the behavior of biological organisms such as macrophytes in different environments including transitional areas. The investigation of many lagoons and ponds described here shows that macrophyte variables and the community composition have strong and univocal relationships with ecological parameters that are a measure of anthropogenic pressure on the ecological status of water bodies. The areas surveyed represent about 78% of the Italian transitional waters (169 sites sampled both in spring and fall). Anthropogenic impacts affect the availability of nutrients in the water column and surface sediments, causing changes in water transparency and phytoplankton concentration (as chlorophyll-a [Chl-a]) that act as the main drivers of variation for macrophyte assemblages, changing species dominance and the conditions that govern their presence or absence. The response of macrophytes to anthropogenic pressure is quite similar in all the examined transitional environments, even when the basin morphology, species richness and composition are different. Some taxa and species assemblages are so sensitive to environmental changes that monitoring them can be considered the most suitable and rapid method for assessing the quality of the environment they inhabit
“…Thus, although water quality in Tokyo Bay has improved, Ulva green tides have increased; the species responsible overwinters as unattached thalli drifting at the sediment surface of shallow waters 22 . The notorious Ulva blooms of Venice in the late 1980s, however, are no longer such a nuisance 23,24 , even though nutrient concentrations -in particular nitrate -have not significantly diminished in the subsequent decades 24 . As biomass accumulation is a function of the seed population multiplied by its growth rate, spreading seed banks of overwintering, free-floating strains of local Ulva could obviate the effects of reducing eutrophication because they are protected from the many Ulva grazers (such as snails and crustaceans) that live on the sea floor 25,26 .…”
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