Estudio de la biomasa y diversidad del fitoplancton de la laguna Paiva, Corrientes (Argentina)

ZALOCAR DE DOMITROVIC, Y.; CASCO, S.L.; ASSELBORN, V.M.

PHYSIS B

Asociación Argentina de Ciencias Naturales

Lugar: Buenos Aires (Argentina); Año: 1998 vol. 55 p. 1 - 13

Species composition, biomass and diversity of the phytoplankton in the Paiva pond (27º 29’S; 58º 45’W) were studied from April 1995 to March 1996. One or two samples were taken monthly in the limnetic and in the littoral area. Cell counts were done by the Utermöhl method (1958). Phytoplankton biomass varied among 0.22 and 17.8 mm3.m-2 with a mean value of 2.46 (±4.4) mm3.m-2. The population density oscillated among 72255 and 1.3x106 ind.cm-2 (x= 374958±311665). Chlorophyll a content ranged between 0.3 and 9 µg.L-1 reflecting the annual variation of phytoplankton biomass. Chlorophyta and Cryptophyceae they were the dominant groups during the year contributing until 67 and 85% of the total of biomass, respectively. Chlorella vulgaris, C. elipsoidea, Ankyra judayi, Monoraphidium arcuatum, Botryococcus braunii, Cryptomonas erosa, C. ovata and C. rostratiformis. The Cyanophyta, third group in importance prevailed during the months warmest of the year contributed until 60% being Anabaena perturbata the dominant algae. Other groups of algae they did not surpass 24% of total biomass. Phytoplankton density diversity varied among 1.4 and 3.6 bits.ind-1. Biomass diversity varied among 0.3 and 2.6 bits.µm-3, with similar variations in the depths of the pond. The highest diversity was always founded in the littoral zone. C-Estrategist, with a high SA/V ratios prevailed in density (Chlorella vulgaris, C. elipsoidea, Ankyra judayi, Monoraphidium arcuatum, Cryptomonas erosa, C. ovata and C. rostratiformis) while S-Strategist (with a low SA/V ratios) such as Botryococcus braunii prevailed in biomass durin the greater part of the year. The phytoplankton no present vertical stratification given the scarce depth of the pond. The horizontal variation of their concentration, biomass and specific composition was not uniform and would be conditioned by the presence and percentage of coverage of littoral vegetation.