Temporal and spatial patterns in the distribution and abundance of pico, nano and microphytoplankton in an upland lake

Abstract

SUMMARY. 1. An investigation of the seasonal and depth distribution of populations of autotrophic picoplankton (0.2–2 μm), nanophytoplankton (>2<20 μm) and larger microalgal plankton (>20μm) was carried out over 21/2 years, 1988–90, in Llyn Padarn, a mesotrophic upland lake in North Wales. 2. Cell numbers of picophytoplankton ranged from <102 to >106 cells cm−3. Maximum numbers of nanoplankton were c. 104 cells cm−3 and the greatest abundance of microalgal plankton, diatoms, reached 12 × 103 cells cm−3. 3. Three types of picoalgae were distinguished: coccoid to oval Synechococcus—Synechocystis, the rod‐shaped Synchecococcus capitatus Bailey‐Watts & Komárek and Chlorella minutissima Fott & Nováková, with maximum numbers of 1.2 × 106, 37.8 × 103 and 44.1 × 103 cells cm−3, respectively. 4. Picophytoplankton exhibited periods of exponential growth: the first in spring, and the second in August—September with an intervening population minimum in early to midsummer. Specific rates of population increase for picophytoplankton were low, with minimum apparent generation times of 3.8 days in summer 1989. 5. Nanophytoplankton included seven species of phytoflagellates and two non‐motile species. These algae were present for about 10 months in each year exhibiting a fluctuation in population density of 102−‐103 cells cm−3. 6. There were spring and autumn maxima in chlorophyll a concentrations in the lake water corresponding to the growth of planktonic diatoms. Maximum total biomass concentration was 35 mg m−3 chlorophyll a, whereas pico, nano and microphytoplankton had individual maxima of 7.7, 8.4 and 31.0 mg m−3 chlorophyll a, respectively. Picophytoplankton often contributed > 60% of the total algal chlorophyll a in the epilimnion. 7. The growth patterns and seasonal periodicities of the three size‐categories of planktonic algae in Llyn Padarn were distinct. Picophytoplankton persist throughout much of the year with periods of very low abundance, < 100 cells cm−3, occurring in winter and midsummer. Thus for much of the year, there was a large inoculum of these cells in the lake to initiate growth leading to the population maxima in spring and late summer. Nanoplankton populations, a diverse assemblage, fluctuated in numbers over the period February–November; no population decline in midsummer comparable to picophytoplankton was observed. The larger microphyloplankton exhibited classical seasonal periodicity, namely diatom growth in spring and late summer–autumn with growth of large‐celled chlorophytes in the intervening summer period.

Colonization dynamics of algae in small artificial ponds

“…growth rates of green algae are generally much higher than cyanophytes. Values of apparent generation times for Chlorella minutissima Fott and Nov6kov6 growing in eutrophic waters were 0.4-1.2 days and in nutrient-poor water 1.0 day (Happey-Wood 1985) compared with minimum generation times of 3.8-4.2 days for cyanobacterial picoplankton growing in a mesotrophic upland lake (Happey-Wood 1991). They demonstrated rapid growth of Scenedesmus proturbans at high light and maximum but much slower growth rates for Oscillatoria agardhii Gomont at low but optimum light intensities.…”

Production of new organic carbon and its distribution between autotrophic picoplankton, bacteria, extracellular organic carbon and phytoplankton in an upland lake

“…Plusssee is more eutrophic than Llyn Padam with maximum chlorophyll levels about four times greater than those of Llyn Padam, recorded in July compared with August or September in Padam (Happey-Wood, 1991), Additionally ^•*C production reached highest rates later in the year in Llyn Padam (Happey-Wood, 1993) than the July and August maxima of Plusssee (Sell & Overbeck, 1992).…”

“…1). Differences in numbers of autotrophic picoplankton between the two depths were not significant, and less than the counting error (Happey-Wood, 1991). Minute chlorophytes and some phycocyanincontaining blue-green algae (cyanobacteria) were dominant until early August.…”

“…Measurement of phytoplankton primary production was carried out in Llyn Padam, a mesotrophic lake in North Wales. The plankton population was separated into three cell size fractions: bacteria, autotrophic picoplankton and the plankton larger than 3M,m: the nano-and microphytoplankton combined Oohnson & Sieburth, 1979;Happey-Wood, 1991, 1993. From a knowledge of the heterotrophic activity of planktonic cells in different cell-size categories and the effidency of separation of bacteria and autotrophic picoplankton, it was possible to correct the estimations of autotrophic picoplankton primary production for bacterial uptake of '''C-labelied EOC derived from the entire phytoplankton community.…”

Vertical distribution of phototrophs in the pelagic zone of three small Lobelia lakes

“…Variation in the pelagic zone is noted with regard to both phytoplankton taxonomic composition and cell size. However, only a few studies have described the abundance, distribution, and composition of the entire phototrophic community in consideration of all taxonomic groups and size fractions (Happey-Wood 1991;Beaty and Parker 1996;Szeląg-Wasielewska 1997, 2003. Size structure is a particularly important parameter in the characterization of phototrophic communities; however, recently increasing attention is being paid to the importance of the smallest cells, namely phototrophic picoplankton, as significant contributors to phototrophic biomass (Weisse 1993, Stockner et al 2000.…”