Abstracts Biological Sciences

The culture and biochemical analysis of some estuarine phytoplankton species

by Carole Lyle DeMort

The biochemical composition of ten species of estuarine phytoplankton was determined. Studies were made of their growth in various culture media and of their relative value as food for oyster larvae. Nine of the species were isolated from Yaquina Bay, Oregon. An attempt was made to select species which commonly occurred in the phytoplankton of the bay. The tenth species, Isochrysis galbana, was obtained from the Culture Collection of Algae at Indiana University. The ten organisms comprised three species of Chlorophyta, one species of Cryptophyta, and six species of Chrysophyta. The relative value of each species as food was determined using larvae of European and native oysters. Determinations were based on the mean length of larvae at the end of the feeding period. Isochrysis, known to be an excellent food source, was used as a standard for comparison with the Yaquina Bay isolates. Cylindrotheca gracilis, Navicula abscondita, and an unidentified centric diatom proved to be adequate food sources for the larvae. Comparison of total protein, carbohydrate, lipid, and pigment showed no differences that could be related to the taxonomy of the organisms. Total protein ranged from 313 μg/mg dry weight to 521 μg/mg. Total carbohydrate ranged from 78 to 316 μg/mg. Total lipid ranged from 53 to 202 μg/mg. Total pigment ranged from 11 to 40 μg/mg. The amino acid composition of the ten species was similar. The five most abundant amino acids were glutamic acid, alanine, glycine, aspartic acid, and leucine. Only Cryptomonas salina did not have leucine. Hydroxyproline was present only in Chlamydomonas palla. Ornithine was not present in Tetraselmis suecica, Prymnesium parvum, or the centric diatom. The three species of Chlorophyta contained chlorophylls a and b, beta carotene, lutein, neoxanthin, and violaxanthin. Cryptomonas salina contained chlorophylls a and c, alpha carotene, and three unidentified xanthophylls. The six species of Chrysophyta contained chlorophylls a and c, beta carotene, fucoxanthin, and diadinoxanthin. An unidentified xanthophyll was found in Cylindrotheca. Total chlorophyll and carotenoid, the ratio of chlorophyll a:b or c, and the ratio of carotenoid:chlorophyll were estimated for each species. Twenty-eight fatty acids were found in the ten species. The fatty acids common to all species were 14:0, 16:0, 16:1, 18:0, 18:1, and 18:2. The Chlorophyta were distinguished by a high content of linolenic acid, 18:3. The diatoms were distinguished by very low amounts of C₁₈ acids and a high proportion of 20:5. All species contained a high proportion of palmitic acid, 16:0. All species were grown in enriched seawater media and artificial seawater media, and a comparison was made of their growth in the different media. Growth curves in an enriched seawater medium were derived for each species. Detailed descriptions of the nine species isolated from Yaquina Bay are given.