Bio-optical characterization of selected cyanobacteria strains present in marine and freshwater ecosystems

Abstract

The optical properties, i.e., absorption and scattering spectra of ten strains of cyanobacteria from the Baltic Sea and Pomeranian lakes (<i>Aphanizomenon flos-aquae</i> KAC 15, <i>Microcystis aeruginosa</i> CCNP 1101, <i>Anabaena</i> sp. CCNP 1406, <i>Synechocystis salina</i> CCNP 1104, <i>Phormidium</i> sp. CCNP 1317, <i>Nodularia spumigena</i> CCNP 1401, <i>Synechococcus</i> sp. CCNP 1108, <i>Nostoc</i> sp. CCNP 1411, <i>Cyanobacterium</i> sp. CCNP 1105, <i>Pseudanabaena cf. galeata</i> CCNP 1312) grown under low light conditions were investigated. Moreover, the chlorophylls, carotenoids, and phycobilin composition as well as the size structure of chosen cyanobacteria were measured. Studied species revealed high diversity both in optical properties with the absorption spectra similarity index ranging from 0.67 to 0.94 and the pigment composition. The chlorophyll-specific absorption coefficient at 440 nm <i>a</i>_<i>ph</i> *(440) varied between 0.017 and 0.065 m² mg^-1. The influence of the package effect was only observed in the case of large filamentous cyanobacteria like <i>N. spumigena</i> or <i>Nostoc</i> sp. Interestingly, the package effect factor <i>Q</i>_<i>a</i> *(675) for large-celled <i>Anabaena</i> sp. was 0.92. Besides chlorophyll <i>a</i>, only echinenone, <i>β</i>-carotene, and phycocyanin were present in all analyzed cyanobacteria strains. Zeaxanthin, which is widely used as a marker pigment for cyanobacteria, was absent in the toxic <i>N. spumigena</i> and <i>Anabaena</i> sp., which are the species that occur in the Baltic Sea most frequently causing summer cyanobacterial blooms. The investigation also showed that the sample preservation technique can introduce some major errors within the absorption band affected by the phycocyanin absorption.