C. Tolomio

Diatoms and dinoflagellates in Terra Nova Bay (Ross Sea-Antarctica) during austral summer 1990

During January/February 1990 the floristic composition and biomass of diatoms and dinoflagellates in Terra Nova Bay (Ross Sea) were investigated. The study area included eight stations, seven of which were inshore and one offshore. Of the 94 taxa identified, 58 were diatoms and 34 were dinoflagellates. Cell densities were higher in surface layers and particularly at two stations, one located at the centre of the bay, and the other to the south of the Terra Nova station. While density data showed that the diatoms predominated over the dinoflagellates and over Phaeocystis sp., the biomass values were largely made up of the dinoflagellates contribution.

Colonization by diatoms and antirheumatic activity of thermal mud.

We have identified diatoms among other thermophilic microorganisms as the main agents for the colonization of thermal mud resulting in a ‘maturation’ which renders the mud suitable to be used for mud‐pack treatment of osteoarthrosis patients. The main effects of the diatom growth are the progressive enrichment of mud extracts in chlorophyll a parallel to the building up of a sulfoglycolipid endowed with an anti‐inflammatory action. The sulfoglycolipid was also produced by diatoms isolated from the mud and cultivated in vitro. Copyright

RESULTATS PRELIMINAIRES SUR LES DIATOMEES BENTHIQUES DE SUBSTRATS MEUBLES DANS LA LAGUNE DE VENISE, ITALIE (MARS 1994–JANVIER 1995)

Research on samples from the Venice lagoon was carried out to determine a suitable method for the quali-quantitative evolution of diatoms living within the sediments. From March 1994 to March 1995, surface sediment samples were collected monthly from a station located in the southern basin of the lagoon. Samples were observed using both light and scanning electron microscope. A list of the taxa found during this research is reported; counts of diatoms present in a volume of sediment were also carried out. Values for cell numbers ranged from 0.2 × 106 to 1.8 × 106 cells/cm3; higher values were recorded in spring/summer and lower values in autumn/winter. Many species belonged to the nannophytobenthos (< 30 μm), which better adapted to move among the grains of sediment than larger species. Benthic taxa, belonging to the centric group of diatoms, were also found.

DISTRIBUTION DES DIATOMÉES BENTHIQUES DE SUBSTRATS MEUBLES DANS LE BASSIN SUD DE LA LAGUNE DE VENISE, ITALIE

The following work points out the results on the microalgae living in the sediments of three sampling stations located at a different distance from the opening of Chioggia harbour-channel (south basin of Venice lagoon). The three examinated areas are characterized by a different granulometry and are differently interested by the supplies of both sea and continental waters. The samplings were made seasonally (March, June, September, December) by taking samples of sediments, from which sub samples were obtained at several levels (0 cm, −6 cm, −12 cm). Besides the identification and the counting (cells mm−3) of the microalgae, almost all belonged to Diatoms, the chlorophyll a concentration as well as the quantity of organic matter and the biomass were determined. The obtained results demonstrated the role of the grain sizes of the solid matrix on the colonization by Diatoms; density values, ranged from 18 to 700 cells mm−3, were higher in the sediments having a reduced granulometry and characterized by high organic matter values. This is important for those species living in the sediments and able to survive in absence of light, using metabolic adaptations that allow the shift to a heterotrophic nutrition. The most important species were Achnanthes delicatula, Amphora exigua, Cocconeis molesta, C. scutellum, Navicula cryptocephala and N. cincta. The comparison among chlorophyll a concentrations as well as biomass values with density data seem to be very difficult to compare.

RECHERCHES SUR LE PERIPHYTON À DIATOMÉES DANS UN VIVIER DE LA LAGUNE DE VENISE (MAI 1984–MAI 1985)

In view of the important role played by the periphyton in the primary productivity of brackish environments, a research has been carried out on benthic diatoms colonizing artificial substrates. For this purpose, slides with different orientations (vertical or horizontal) were kept submerged for about 30 days in two stations of ‘Valle Doga’ (a Northern fish pond of the Venice Lagoon). Qualitative and quantitative (i.e. the cover estimated as cells.cm−2) analyses as well as evaluations of the biomass were made on the diatom populations. The more representative and constantly present forms were three species belonging to the genus Cocconeis (C. molesta, C. placentula, C. scutellum). Other species (Achnanthes exigua, Amphora exigua, A. veneta, Licmophora cf. biplacata, Navicula gracilis v. recurva, Synedra tabulata) were only sometimes abundant. This study, together with one of the phytoplankton carried out in the same period, provides knowledge about the trophic chain in these environments.

CONTRIBUTION A LA CONNAISSANCE DU PERIPHYTON DIATOMIQUE DES EAUX SAUMATRES DE LA VALLE SPARESERA (SUITE)

The present research continues the study of benthic diatoms colonizing artificial substrates kept submerged in brackish water. For this purpose samples from three stations of “Valle Sparesera” (an experimental fish pond of the Venice Lagoon) were studied. Periphyton and various environmental factors were measured. The results show that the genera fouling fresh substrata are abundant, especially where there is considerable water movement. This however does not correlate with data on populations per unit area. The most abundant and constantly present species were Amphora exigua, Synedra tabulata and two species belonging to the genus Cocconeis (C. molesta, C. scutellum). The position of vertical or horizontal exposed slides had no influence upon the quantity of periphyton. Comparison with the phyto-plankton carried out over the same period showed that, contrary to the usual situation, the highest development of phytoplankton occurs before that of benthic diatoms.

Fitoplancton e fitobentos lungo le coste calabro-campane (Mar Tirreno). Primo contributo

Abstract Phytoplankton and phytobenthos along the Calabrian and Campanian coasts (Tyrrhenian Sea). — This is the first contribution to the knowledge of the marine flora of the Gulf of Policastro and of the sorrounding zone. Planktonic and benthonic algae have been collected and are listed in this paper.

Phytoplankton and chemico-physical parameters of the Scardovari Lagoon (Po Delta, North Adriatic Sea) during 1991 and 1992.

Abstract During research directed towards the employment of the biological resources of the North Adriatic lagoons, from January 1991 to December 1992, in both tidal phases, a survey was carried out on the phytoplankton and the chemico-physical parameters of the Scardovari lagoon. Data analyses allowed two different areas to be distinguished: one inner, which was generally characterized by high phytoplanktonic densities (St. 3–4), the other outer, which was more influced by marine load (St. 1–2). Photosynthetic picoplankton was dominant in terms of cell number in most samples. Phytoplanktonic fraction >2 μm was represented mainly by diatoms, which showed the higher species number. During the sample observation, some dinoflagellates, considered toxic or potentially toxic, were found. Their presence was important because of their effect on the bivalve mollusc cultures.

Osservazioni sull'ambiente e tipologia estiva del fitoplancton e fitobentos lungo il litorale di Tropea (Calabria). Secondo contributo

Abstract Environment studies and summer typology of the phytoplankton and phytobenthos along the Tropea coast (Calabria). II.—In this work the results are related of a study on the sea environment and the planktonic and benthonic algae, which were collected along the coast between Capo Vaticano and Briatico (Calabria—Tyrrenian Sea). This study is the continuation of a previous research.