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2 Polish Journal of Ecology

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Factors controlling pelagic production and respiration in a shallow polymictic lake

Wielgat-Rychter M., Rychter K., Ficek D.

Polish Journal of Ecology

2010

Vol. 58, nr 2

379-385

Shallow lakes, defined as 'nonstratifying', polymictic water bodies are usually eutrophic and highly productive, and more turbid than deeper lakes due to bottom sediment resuspension. Gross primary production (GPP) and total planktonic community respiration (TCR) were measured in a very shallow (on average 1.2 m deep) and large (area 25 km2), polymictic, eutrophic Lake Gardno (Baltic coastal lake, Northern Poland) with the light-and-dark bottle method. The aim was to compare GPP to TCR ratio in the pelagic zone in a course of a year and identify factors governing these processes. Identified factors governing GPP were light conditions and temperature, with Q[10] = 2.23 in the 2-24.5[degrees]C temperature range, whereas TCR was driven by water temperature (Q[10] = 2.15 in the same temperature range) and by organic matter content in water. TCR was correlated with total suspended matter (effect of bottom sediment resuspension due to wind action in a very shallow lake), however not with chlorophyll content. During two-year measurement period (years 2006 and 2007), annual GPP amounted to 402 and 471 g C m[^-2], and TCR amounted to 192 and 223 g C m[^-2] respectively. Lake Gardno pelagic system seemed to be net autotrophic on annual basis; GPP to TCR ratio = 2.1. Part of the organic matter produced in pelagial is probably deposited in bottom sediments decomposed there. Wind induced resuspension increases matter content in water (measured here as TSM content) and thus contributes to pelagic respiration processes (TCR).

Planktonic ciliates in the coastal medium-size river : diversity and productivity

Rychter K.

Polish Journal of Ecology

2009

Vol. 57, nr 3

503-512

Annual changes in abundance, biomass, and taxonomic composition of potamoplanktonic ciliates were assessed in the 139 km long, coastal (Baltic coast) river (the Słupia River, Northern Poland) having mean annual flow - 18 m[^3] s[^-1] and flowing through several natural lakes and reservoirs. The samples were taken from one site, once a week from December 2005 to December 2006, then concentrated by sedimentation and counted and measured under an inverted microscope. Ciliate production was assessed with relevant published formulas. Mean annual abundance and biomass amounted to 6448 cells l[^-1] and 6.60 [my]g C l[^-1], respectively. During the year two distinct peaks of biomass were observed: a spring peak in April and May, and a winter one in December. Spring peak was formed by prostomatids and oligotrichs, whereas winter one by peritrichs. Three aforementioned orders contributed altogether to 64% of abundance and 82% of ciliate biomass. Prevalence of prostomatids seemed to be characteristic for the studied river. Most of ciliates were surprisingly small, fraction below 20 [my]m contributed 77% of the mean annual abundance. Domination of small ciliates indicated high mean annual potential growth rates ranging from 0.6 d[^-1] to 0.7d[^-1]. The river is characterised by a narrow variability of the water level and numerous through-flow lakes. As a result ciliate community in the river resembled communities encountered in lakes - free-swimming organisms dominated and sessile forms and those detached from sediments contributed not more than one fifth of ciliate biomass.