Microalgal biovolume is commonly calculated to assess the relative abundance (as biomass or carbon) of co‐occurring algae varying in shape and/or size. However, a standardized set of equations for biovolume calculations from microscopically measured linear dimensions that includes the entire range of microalgal shapes is not available yet. In comparison with automated methods, the use of microscopical measurements allows high taxonomic resolution, up to the species level, and has fewer sources of error. We present a set of geometric shapes and mathematical equations for calculating biovolumes of >850 pelagic and benthic marine and freshwater microalgal genera. The equations are designed to minimize the effort of microscopic measurement. The similarities and differences between our proposal for standardization and previously published proposals are discussed and recommendations for quality standards given.

No abstract

The long-term (22 yr) record of primary production in Lake Kinneret, Israel, has been examined, together with chlorophyll and microscopically determined algal biomass, in order to discern whether there have been any significant changes in these parameters during this period. During the period 1972 through 1993, annual averages have ranged from 1,223 to 2,3 11 mg C m-2 d-l for primary production, from 127 to 246 mg m-2 for chlorophyll, and from 39.3 to 98.5 g m 2 for algal wet weight. The annual peak of these parameters was in April-May. Over 22 yr, variability in primary productivity was more closely related to changes in chlorophyll than to changes in algal biomass. No evidence was found for consistently increasing long-term trends in primary production, chlorophyll concentrations, or algal wet weight biomass from 1972-1993. Although the annual and semiannual averages of algal biomass were significantly higher in the past 11 yr than those in the previous decade, this pattern could arise from a long-term cyclical but self-compensating trend. The extended record indicates that despite population growth and intense economic development around the lake and in its catchment area, there has been no extreme eutrophication of Lake Kinneret from 1972 to 1993. We suggest that this relative resiliency of the Kinneret ecosystem is due to high ambient levels of alkalinity, calcium, and pH in the lake water acting to limit phosphorus availability, which in turn restricts the outgrowth of phytoplankton.

Annually, during the months January to June, a heavy bloom of the dinoflagellate Peridinium cinctum fa westii occurs in warm (13–30° C), monomictic Lake Kinneret, Israel. The rates of carbon assimilation, determined with 14C, were not exceptionally high, but algal biomass and chlorophyll concentrations measured during the bloom season were among the highest recorded for the trophogenic zone of any natural water body. Effective utilization of environmental conditions by the motile Peridinium, which dominates the phytoplankton assemblage and is only slightly grazed, may partly explain the large standing crops. During the bloom, physiological activities are minimal (low assimilation numbers, activity coefficients, and specific growth rates); conversely, high values for these parameters occur in late summer and fall (when Chlorophyta predominate) and at the start of the bloom. The patterns of algal behavior in Lake Kinneret may have general implications for understanding the role of phytoplankton in warm eutrophic ecosystems.

No abstract