THE IMPORTANCE OF DIATOM CELL SIZE IN COMMUNITY ANALYSIS¹

Abstract

The large variation in size and shape in diatoms is shown by morphometric measurements of 515 benthic and pelagic diatom species from the Baltic Sea area. The largest mean cell dimension (mostly the apical axis) varied between 4.2 and 653 μm, cell surface area between 55 and 344,000 μm2, and cell volume between 21 and 14.2 × 106μm3. The shape‐related index, length to width ratio, was between 1.0 and 63.3 and the shape‐ and size‐related index, surface area to volume ratio, was between 0.02 and 3.13. Diatom community analysis by multivariate statistics is usually based on counts of a fixed number of diatom valves with species scores irrespective of cell size. This procedure underestimates the large species for two reasons. First, the importance of a species with higher cell volume is usually larger in a community. Second, larger species usually have lower abundances and their occurrence in the diatom counts is stochastic. This article shows that co‐occurring small and large diatom species can respond very differently to environmental constraints. Large epiphytic diatoms responded most to macroalgal host species and small epiphytic diatoms most to environmental conditions at the sampling site. Large epilithic diatoms responded strongly to salinity, whereas small epilithic diatoms did so less clearly. The conclusion is that different scale‐dependent responses are possible within one data set. The results from the test data also show that important ecological information from diatom data can be missed when the large species are neglected or underestimated.

Environmental control of diatom community size structure varies across aquatic ecosystems

“…Area was used as a measure of diatom size because this is what can be reliably measured when looking at a sample under a microscope. It can be difficult to obtain all the dimensions required to estimate volume; in general, the largest axial dimension is highly correlated to cell volume (Snoeijs et al 2002).…”

An assessment of particulate organic carbon to thorium-234 ratios in the ocean and their impact on the application of 234Th as a POC flux proxy

“…All C / 234 Th versus size relationships that rely on V: SA are sensitive to particle shape, size and morphology. Cell-specific changes in V: SA during growth (Snoeijs et al, 2002) or seasonal progression of a biological community, that includes bacteria up to large cells and aggregates, impact the average V : SA relationship and would thus influence the C / 234 Th ratio. Conceptually, a change in C / 234 Th vs. size is important because sinking velocities are thought to be related to particle size and excess density (Smayda, 1970;Asper, 1987;Alldredge and Gotschalk, 1989).…”

Community structure and seasonal dynamics of diatom biofilms and associated grazers in intertidal mudflats

“…Likewise, the difference in size of the prevailing diatoms may be explained in terms of coping with the fluctuations in the environmental conditions in the Westerschelde. R-types, small and fast-growing species (Snoeijs et al 2002) using an abundance of available resources in early spring time, are assumed to be less specialised than K-types, large and slow-growing species, under the limited resources that prevail in summer time. Therefore, large species may respond negatively to fluctuations in the spring time and appear in summer under stable conditions.…”