H. KALCHEVA1, L. NIKOLOVA2, D. TERZIYSKI2, A. STOEVA2 and R. KALCHEV1
1Institute of Zoology, Bulgarian Academy of Sciences, , BG - 113 Sofia, Bulgaria
2Institute of Fisheries and Aquaculture, BG - 4000 Plovdiv, Bulgaria
This study investigates dynamics of bacterioplankton in four carp fish ponds in Bulgaria during June-September period in 2005. Plankton gross primary production (GPP), chlorophyll a, phaeopigments, nutrients and environmental physico-chemical variables were registered simultaneously. The aim was to search for differences between treated and non-treated with organic manure ponds by comparing bacterioplankton abundance and in its relationships between the above listed variables on one hand, and numbers, biomass or percentages of bacterial morphological groups on the other by means of statistical analyses. The differences between bacterioplankton numbers of manured and non-manured ponds although insignificant, were close to the significance border. The bacterial biomass of control ponds tended to be higher during the first half of the experiment while during the second the tendency reversed. Oxygen saturation was the major environmental factor with significant influence on both number and biomass of bacteria in seasonal aspect. There were a positive relation (R=0.495, P=0.0046) of oxygen saturation to the number of free-living cocci - the most numerous part of bacterioplankton community, and a negative one (R=-0.519, P=0.0023) to on detritus attached bacteria. Free-living rods were weakly influenced by oxygen saturation. GPP was positively related to abundance while hydraulic retention time (RT) to biomass of free-living bacterioplankton. The temporal variations of factors mentioned above (GPP and RT) had opposite effects on development of bacteria attached on detritus. Chlorophyll a and nutrients (phosphorus, nitrogen) did not correlate to the development of bacteria neither in spatial nor in temporal aspect.
Abbreviations: BSS - Bulgarian state standard, GPP - gross primary production, HNF - heterotrophic nanoflagellates, N – inorganic soluble nitrogen, P – phosphate phosphorus (soluble reactive phosphorus) RDA - redundancy analysis, RP - Pearson parametric correlation, RT - hydraulic retention time.