Short-term analysis of the phytoplankton structure and dynamics in two ponds with distinct trophic states from Cierva Point (maritime Antarctica)

ALLENDE, L.; MATALONI, G.

POLAR BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2013 vol. 36 p. 629 - 644

0722-4060

Phytoplankton communities dominating Musgosand Papu´a ponds with differing trophic states were sampledover 3 days enabling the detection of the physiological andpopulation responses of microalgae to short-scale changes inbiotic and abiotic factors, rather than frequently analyzedchanges in community composition responses to long-scaleenvironmental changes. We hypothesized that both environmentsundergoing diel changes would be dominated byphytoplankton with generalist strategies, while communitystructure would be mostly dictated by the trophic state ofeach water body. The phytoplankton biovolumes of bothponds were strongly dominated by euplanktonic nanoflagellatedChlorophyta, while phycocyanin-rich picocyanobacteriadominated the picophytoplankton. Parallel dielcycles of air and water temperatures were more pronouncedon a sunny, warm day which prompted algal photosynthesis,revealed by strong increases in dissolved oxygen andpH. Nutrient and phytoplanktonic chlorophyll a confirmedthe hypertrophic condition of Papu´a pond. This accountedfor the distinct community composition encountered ineach pond, which remained stable throughout the study,as revealed by the SIMI index. The inverse relationshipbetween the chl a/abundance ratio and the abundances ofdominant species together with varying net growth rates (k0)showed algal reproduction, yet densities remained ratherstable in both cases. In Musgos pond, fluctuations in k0 forsmall and median ciliates shadowed those of pico- andnanophytoplankton, respectively, strongly suggesting thatthey can control algal growth in these 2-level trophic chains.