engleski

Phytoplankton primary production and community respiration in the Nature Park Kopački rit (Croatia)

The paper presents the results of the phytoplankton primary production (gross and net), community respiration and specific rate of biomass production per unit of chlorophyll-a in Čonakut and Hulovo Channels and Lake Kopačko in 1984 and in Lake Sakadaš during 1988, 1990 and 2002, using the in situ light and dark bottle oxygen technique. All parameters of the primary production were characterized by high variability that was the consequence of the seasonal changes as well as differences in sampling dates. Areal net production and ammonium concentration were positively correlated (r = 0.502, P < 0.05, n = 28) in the shallow part of Kopački rit (Lake Kopačko and Čonakut and Hulovo Channels) and negatively correlated (r = -0.729, P < 0.05, n = 14) at Lake Sakadaš. Daily rates for areal NP were as high as 3 g C m-2 d-1 at Čonakut Channel. The lowest average values of areal NP were at lakes Sakadaš (0.61 g C m-2 d-1) and Kopačko (0.69 g C m-2 d-1), indicating mesoeutrophic conditions. In Lake Sakadaš, during the investigated period, respiration was generally higher than production, with the highest portion (70%) of community respiration in the gross production, indicating tendency towards heterotrophy. The highest values of assimilation ratio, as an index of the phytoplankton community nutrient status were determined in early spring, indicating favorable nutrient conditions for phytoplankton growth.

specific rate of biomass production; areal net production; P:R ratio; channels and lakes; Nature Park Kopački rit (Croatia)

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