Phytoplankton of the reservoirs of Central and North Patagonia
Casco, María A; Labollita, Héctor A.; Cano, María G.
The basins of the Limay, Neuquén, and Negro rivers comprise the greatest hydrographic system developed in its entirety in Argentina. The reservoirs constructed in this basin are distinguished by their numbers, dimensions and unitary system of management. Within the framework of environmental-monitoring programs carried out from 1977 to the present, 394 species were identified in these systems. Only 30 taxa were common to all the reservoirs. Some of the dominant taxa were: Anabaena spp. (toxic complex), Ceratium hirundinella,Gymnodinium sp., Asterionella formosa, Aulacoseira ambigua var. ambigua f. spiralis, Aulacoseira pseudogranulata, Aulacoseira subarctica, and Stephanodiscus niagarae. Chlorophyta and Chrysophyta were the algal groups with the highest species richness. The Cyanobacteria played a significant role, and so, two agendas for monitoring algal blooms were developed in the basin: (a) at one sampling station on the Limay River (near Arroyito Reservoir), (b) in the Mari Menuco reservoirs of the Neuquén River. Anabaena spp. (toxic complex) was seen to exhibit the greatest abundance between the spring, the summer, and the beginning of the autumn. Another reservoir that has been the object of limnological investigations since 1990 is the Florentino Ameghino, situated within the eastern-central region on the Chubut River. The centric diatoms – principally Aulacoseira granulata, Stephanodiscus sp., and Cyclotella sp. were the best represented in this reservoir. The phytoplankton was composed of species characteristic of mesotrophic to eutrophic lakes.