Angeler DG

Life-cycle studies and culture experiments for identification of doubtful volvocacean organisms - observations on Pandorina and Eudorina
HYDROBIOLOGIA 370: 269-275 1998

Abstract:
Traditionally, the volvocacean genera Pandorina and Eudorina are distinguished by vegetative morphology: Eudorina has hollow coenobia with loosely arranged spherical to ovoid cells, whereas Pandorina coenobia are compact with pear- to keystoneshaped cells contiguous in the centre. However, sometimes intermediate forms are found which cannot be identified to genus by traditional morphological characters. Especially the degree of compactness of Pandorina coenobia may be highly variable. Such abberant forms must be taken into culture in order to establish their identity, by studying (1) their lift: cycles, both sexual and asexual processes, and (2) the influence of varied culture conditions (temperature, daylenght, nutrients) on their morphology. In these ways, the taxonomic position may be clarified.

Cvijan M, Lausevic R

The significance of green algae in Vlasinsko Jezero reservoir phytoplankton (Serbia)
BIOLOGIA 53 (4): 519-527 AUG 1998

Abstract:
The paper highlights the importance of green algae in phytoplankton community formation and primary production of the dimictic, mesotrophic Vlasinsko Jezero reservoir. Green algae from plankton samples are presented by 87 taxa, with predominance of desmids. The highest floristical diversity has been established in the shallow bays and between aquatic macrophytes, especially in the southern part of the reservoir at the edge of peat bog. In the terms of biomass, green algae play the most important role in building up phytoplankton community. Chlorophyll-a maxima corresponded with the development of Chlorophyta populations composed mainly of Planktosphaeria sp., Eudorina elegans and Pandorina morum.

Ott I, Laugaste R

Organic matter and the composition of Volvocales and Chlorococcales in Estonian small lakes
BIOLOGIA 53 (4): 529-535 AUG 1998

Abstract:
The limnological data gathered mainly between 1951 and 1995 were summarized from the point of view of relationships between organic substances and chlorococcalean and volvocalean species in summer. During the last forty years the role of Chlorococcales (including the biomass values) rose in all lake groups as well as the content of organic compounds. Chlorococcales and Volvocales are especially important (abundance and number of species) in the investigated lakes where the amount of easily degradable allochthonous organic compounds has risen. Simple correlations between the different characteristics of organic compounds, biomass, and the number of species are generally weak. Correlations are stronger with BOD values. Heavy allochthonous organic load from different sources may cause water bloom by Chlorococcales and Volvocales. The highest Values were recorded from Lake Harku in Tallinn because of sewage water from the city (biomass 46.1 g/m(3), Scenedesmus quadricauda (TURPIN) BREB. sensu CHODAT, Pediastrum boryanum (TURPIN) MENEGHINI; Partsi Kortsijarv (dairy industry, 32.1 g/m(3), Tetraedron minimum (A. BRAUN) HANSG., Scenedesmus quadricauda); Kooraste Linajarv (flax retting, 15 g/m(3), Dictyosphaerium pulchellum Wood); L. Ruusmae (manure, 14.5 g/m(3), Coelastrum microporum NAGELI and Eudorina elegans EHRENB.). The most common alga in the lakes with a high content of easily degradable organic matter is Phacotus coccifer KORSHIKOV. In some cases, allochthonous DOM could be the factor that control the development of phytoplankton. During the last four decades the number of species and abundance of Volvocales and Chlorococcales has increased, and lakes have become more similar to ponds and sewage treatment pools.

Schagerl M, Angeler DG

The distribution of the xanthophyll loroxanthin and its systematic significance in the colonial Volvocales (Chlorophyta)
PHYCOLOGIA 37 (2): 79-83 MAR 1998

Abstract:
The distribution of the xanthophyll loroxanthin [(3R,3'R,6'R)- beta,epsilon-carotene-3,19,3'-triol] within colonial volvocalean families was analyzed by reversed-phase high pressure Liquid chromatography (rP-HPLC). The results demonstrate that loroxanthin is a physiological marker delineating the families Tetrabaenaceae Nozaki et Itoh and Goniaceae (Pascher) Pascher. Thus loroxanthin may be considered to be of systematic significance within the Volvocales, and its use as a marker supports recent ideas on phylogenetic relationships. Within the Volvocaceae Ehrenberg, its infraspecific disjunct distribution indicates that it is not useful systematically in this family and that it varies even within a morphologically defined species. The pattern of loroxanthin distribution was compared with molecular data and traditional characters.