Trophic condition of the volcanic Lake Nemi (Central Italy): environmental factors and planktonic communities in a changing environment

Lake Nemi is an interesting case of anthropogenic overexploitation which has caused its progressive environmental deterioration in the past decades. On this lake historical data about the trophic situation are available from 1975 to 1984. The research performed in 2002-03, about ten years after the diversion of urban waste waters, concerned a biological investigation on the phyto- and zooplanktonic communities, integrated with a physico-chemical analysis. The aims of our study are to evaluate the current water quality of the lake and compare it with the water quality observed in 1982-1983, when all biotic and abiotic components indicated a heavily compromised hypereutrophic condition. The water quality data and the comparison with a previous study point out that the biological aspects have partially changed (increased number of Cyanobacteria and phytoplanktonic taxa, particularly Clorophyta and Dinophyta; zooplankton composition changed at a species level, with the appearance of taxa associated to light trophic conditions), and the physico-chemical conditions significantly improved. The mean transparency, dissolved oxygen, nutrients and chlorophyll-a concentrations have all improved. Mean annual temperature at different depths increased, probably due to differences in climatic period and the lowering of the lake surface level (from 32.5 to 27.5 m in 1982 and 2002, respectively). Our results indicate a general improving trend in water quality is taking place since the diversion of waste water discharges. The present abiotic characteristics of the lake allow the phytoplankton to distribute itself in the whole epilimnion, and the zooplankton in the whole water column. A possible further improvement is hypothesized, and the constraints represented by excessive water level lowering and water temperature increasing are also discussed

Brachytheca inopinata (Desmidiaceae, Zygnematophyceae), a new desmid from New Zealand

A new desmid species, Brachytheca inopinata Fumanti & Alfinito, is described from Lake Monowai, New Zealand, and the diagnosis of the genus Brachytheca is emended. The new species has cylindrical cells, about as long as broad, apical angles that are slightly rounded and a straight apex. The cell wall is smooth, with transverse rows of apical and subapical pores and without longitudinal grooves

Contribution to the knowledge of freshwater algae from Lake Hamun-i-Puzan (Iran).

54 species of algae belonging to 28 genera were recognized in the water samples collected in Hamun-i-Puzak Lake placed in Iranian Sistan Depressio

Diatoms from York, Sierra Leone (West Africa).

Twenty nine species and varieties of diatoms belonging to 12 different genera are recorded in water samples collected by prof. W. Rossi in a temporary swamp near York (Western Area) during a scientific expedition in Sierra Leone. Seven taxa are new records for Sierra Leone

DESMIDS FROM GUMA-VALLEY (SIERRA-LEONE, WEST AFRICA)

Twenty-two taxa of desmids are reported from a pool near Guma Valley (Sierra Leone). Six are new to the country. A new variety of Staurastrum hystrix (S. hystrix var. granulatum) is described

Benthic algal mats of some lakes of Inexpressible Island (northern Victoria Land, Antarctica)

Benthic algal mats from four lakes located on Inexpressible Island (northern Victoria Land, Antarctica) were studied, analysing their structure and Aoristic composition. Thirty taxa of algae were identified: 11 Cyanophyta, 15 Bacillariophyta and 4 Chlorophyta. The lake mats contained from 15 (lake C) to 26 species (lake D). The number of diatom frustules in the mats varied from 771 x 10(3) (lake C) to 9428 x 10(3) frustules g(-1) (lake B). In terms of floristic composition and macromorphology, these mats were observed to be very similar to moat mats described from Lake Gondwana (northern Victoria Land) and the Dry Valleys lakes of southern Victoria Land

The algal microflora of the salt works of Tarquinia (Italy)

The microflora and benthic microbial mats of the salt works of Tarquinia (Italy) are described. From 144 samples, 111 species and varieties of microalgae were identified. Diatoms prevailed up to 110‰. S. They were substituted by Cyanophyta at higher salinities. The microbial mats consisted of Cyanophyta, Beggiatoa spp., purple sulphur bacteria, and diatoms. Information on hypertonic resistance in some euryhaline species is given. © 1990 Kluwer Academic Publishers