Carla Rita Ferrari

Abundance and chemical characterization of extracellular carbohydrates released by the marine diatom Cylindrotheca fusiformis under N- and P-limitation

The effect of P- and N-depletion on the production and molecular-level composition of extracellular carbohydrates released by the diatom Cylindrotheca fusiformis was examined in axenic batch cultures. Inorganic phosphorus depletion caused a higher release of organic carbon per cell compared to nutrient-replete and nitrogen-limited conditions. Gas-chromatographic analysis of the monosaccharide composition of the dissolved fraction showed galactose to be the major component of the exopolymers (33 – 42%). In the P-limited treatment, an increase of galactose content and a decrease of glucose was found, while the composition of the remaining saccharides was almost unaffected. The results point out the relevance of phosphorus limitation not only in causing an increase in total exopolysaccharide production, but also in affecting the neutral aldose composition of the dissolved carbohydrates released by C. fusiformis, with heteropolysaccharides being more abundant than glucan. The overall sugar composition of the exopolymers released under the most severe P-depletion was similar to that of natural mucilage samples collected in the Northern Adriatic Sea during the Summer 2000 event of massive aggregation.

Mucilages in Italian seas: the Adriatic and Tyrrhenian Seas, 1988–1991

Abstract Mucilage events, i.e. the accumulation of a gelatinous material at and below the water surface during summer months, have been known to occur at irregular intervals in the Northern Adriatic Sea for over 200 years, but events of the severity of those of 1872 and 1905 were less noted later in this century. The phenomenon reappeared in 1988 and in the years that followed. In 1991 it was also noted in the Tyrrhenian Sea. Our studies cover the events of 1988–1991 in the Northwest Adriatic and some aspects of the Tyrrhenian Sea. The results presented in this paper provide additional insight into the problem. In general, it can be stated that while we have a fair understanding of the phenomenological and dynamic aspects, and of the environmental consequences of the events, we know little about the causal factors which trigger and maintain the process.

Eutrophy and dystrophy in the Goro Lagoon (Italy)

The eutrophication of the lagoon systems in the coastal areas of the Northwest Adriatic Sea has caused serious damage not only to the ecosystem but also to the economy based on the tourist and fishing industries. This work presents the results of a study on the Goro Cove carried out during 1987-1988. An analysis of the data shows that the high trophic level and the consequent dystrophies (anoxia of the waters) are caused by the large amount of nutrients carried into the lagoon by the Po and Burana-Volano rivers

Organic aggregates formed by benthopleustophyte brown alga Acinetospora crinita (Acinetosporaceae, Ectocarpales)

This work presents the elemental, polysaccharide, and fatty acid compositions of benthic aggregates formed by the filamentous brown alga Acinetospora crinita, which are widely spread on the rocky bottoms of the Mediterranean Sea. The aggregates can be characterized as mineralized centers in which regeneration of nutrients and recycling of dissolved organic matter actively occur and favor the development of an abundant phytoplankton community. Analyses of the stable isotopes of C and N display their marine origin and could provide evidence of the processes that occur inside/outside of the aggregates. The monosaccharide compositions of Adriatic and Tyrrhenian mucilages produced by brown alga A. crinita were quite similar. In particular, the Adriatic sample compositions resembled the average composition of the Tyrrhenian high molecular weight exopolymers, and the observed differences could be ascribed to different degradation stages. The fatty acid patterns found for the aggregates were similar to those observed in the isolated A. crinita algae with variable contributions from embedded diatom species. The bacterial contribution to the fatty acid pool was quite low, most likely due to the known poor conditions for their heterotrophic growth.