INVESTIGADORES
ROSSO Juan Jose
artículos
Título:
Trophic interactions in shallow lakes of the Pampa plain (Argentina) and their effects on water transparency during two cold seasons of contrasting fish abundance
Autor/es:
SOSNOVSKY, ALEJANDRO; ROSSO, JUAN JOSE; QUIRÓS, ROLANDO
Revista:
Limnetica
Editorial:
Asociación Ibérica de Limnología
Referencias:
Lugar: Barcelona; Año: 2010 vol. 29 p. 233 - 246
ISSN:
0213-8409
Resumen:
Trophic cascade interactions in shallow lakes have been studied extensively in the north temperate region, mainly during the summer period. However, much less research on this topic has been undertaken in warmer regions during the winter period. The aim of the present work was to study trophic cascade interactions and their effect on water transparency in small lakes from the Pampean plain (Argentina) during the cold season. In addition, we examined whether low fish abundance would allow the appearance of key zooplankton genera such as Daphnia. Seven shallow lakes were studied during the autumn-winter period of the years 2000 and 2001. The dominance of the main primary producers varied between lakes. While five lakes were turbid, dominated by phytoplankton, two lakes were clear, dominated by macrophytes. In the autumn of 2000, fish were removed from six of these lakes. By the following year, the fish community had recovered naturally in these lakes. In the phytoplankton dominated lakes both zooplankton biomass and size were higher during the low fish abundance period. Moreover, large Daphnia were present, contributing to the decrease in algal biomass per unit of nutrients. Thus, it has the potential to increase water transparency in these lakes. On the other hand, in the vegetated lakes zooplankton biomass was low and large Daphnia was scarce, probably because of the presence of macroinvertebrate predators. In spite of this, water transparency was high in these ecosystems. From our results, we conclude that trophic interactions probably play a fundamental role in the determination of zooplankton structure and biomass in the small temperate warm lakes of the Pampean plain, even during the cold season of the year. Moreover, the effects of fish would reach the lowest levels of the trophic chain, affecting water transparency. However, water transparency might be influenced by other factors as well. It would be naturally elevated in the presence of macrophytes, and would also be greatly affected by the hydrology of the region.