This paper presents angular and spectral measurements of the functions that create a scattering matrix (Mtiller matrix). The investigations were carried out on monocultures of the unicellular phytoplankton ChZoreZEa vulgar-is, ChZoreZZu kesleri, and Chroococcus minor at scattering angles from 8" to 155" and at wavelengths of 488, 514, and 633 nm. Living cultures of phytoplankton as well as cultures treated chemically (boiled in 5% NaOH) and physically (ultrasound) were tested. These treatments alter the internal structures of the cells, and show that the altered structures modify the scattering matrix functional.

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Cyanobacteria, otherwise known as blue-green algae, are oxygenic, photosynthetic prokaryotes. They occur naturally in many fresh, marine and brackish waters worldwide and play an important role in global carbon and nitrogen cycles. In their long history, cyanobacteria have developed structures and mechanisms that enable them to survive and proliferate under different environmental conditions. In the Baltic Sea, the mass development of cyanobacteria is compounded by a high level of eutrophication. The dominant species in the Baltic, the filamentous Aphanizomenon flos-aquae and Nodularia spumigena, can fix dissolved atmospheric N 2 , as a result of which they can outcompete other phytoplankton organisms. Heterocystous, filamentous cyanobacteria also make a significant contribution The complete text of the paper is available at http://www.iopan.gda.pl/oceanologia/ 294 H. Mazur-Marzec, M. Pliński to the internal nutrient loading in the Baltic. The blooms of N. spumigena are of particular concern, as this cyanobacterium produces nodularin (NOD), a hepatotoxic peptide. The concentration of the toxin in the sea is regulated mainly by dilution with uncontaminated water, photolysis, sorption to sediments and microbial degradation. The transfer of the toxin in the Baltic trophic chain through zooplankton, mussels, fish and birds has been reported, but biodilution rather than bioconcentration has been observed. Cyanobacterial blooms are thought to pose a serious threat to the ecosystem. Their harmful effects are related to the occurrence of a high biomass, oxygen depletion, a reduction in biodiversity, and the production of toxic metabolites.

Laboratory measurements of light scattering on the axenic cultures of unicellular alga Chiorella vulgaris monoculture confirm the thesis of multi-level light scattering by the cell i. e. both by outer cell membrane and the internal structure of the cell, as well as by its molecular structures. In the measurements the technique of dynamic light scattering and the analyzis by the regulation method was used indicate that the light scattering phenomenon is affected by particles of sizes corresponding either to overall dimensions of the cell or to the dimensions of its internal structures. A correlation was found between the suggested sizes and the stage of physiological evolution of the culture. The measurements of 10 functions constituting the elements of the scattering matrix for an alive Chiorella vulgaris culture and cultures with internal cell structures modified by chemical and mechanical agents evidence that the internal structures of cells play an important role in the interaction of phytoplankton and light.