Search

Few major groups of cyanophytes contribute significantly to the productivity of oceanic oligotrophic ecosystem: unicellular Synechococcus spp., and filamentous nitrogen-fixing Trichodesmium and Richelia species occur as abundant populations in open seas and oceans. In addition, oceanic eutrophic waters support the development of massive summer-blooms of Nodularia, Aphanizomenon and Anabaena in the Baltic Sea. The importance of the planktic cyanophytes as primary producers and their contribution to the input of new fixed nitrogen in the euphotic zone is underlined.

The dominant algae colonizing hypogean sites are usually epilithic cyanophytes which are often associated with chlorophytes and diatoms, and sometimes mosses. High relative humidity and extremely low photon fluxes characterize the environment in which a prevalence of shade-adapted species is supposed. The interactions with the substrate and the light adaptation of the algae encountered is discussed also in relation to biodeterioration processes. The taxa occurring in hypogea are reported in comparison with cave vegetation. The phototrophic communities support the growth of abundant bacterial populations.

A strain of the alga Spermatozopsis acidophila from highly acidic environments in the solfatara at Pisciarelli (Naples, Italy) has been studied from the ecological, physiological, morphological and ultrastructural points of view.Its pH optimum (1.0) and its upper limit of pH (1.8) are the lowest recorded for any algal species.Our ultrastructural investigation has confirmed that it belongs to the family Poly-blepharidaceae (Volvocales). A conspicuously developed chloroplast was noted, along with a remarkable quantity of microtubules and E. R. cisternae.

Epilithic species of heterocystous cyanobacteria were isolated from Roman hypogea, grown at low photon flux densities and morphologically characterized. Determination of photosynthesis versus irradiance curves and nitrogen fixation activities on three of these strains, showed that their photosynthetic efficiency was low but sufficient to sustain nitrogen fixation.