TITLE:
Trophic Status of Shallow Lakes of La Pampa (Argentina) and Its Relation with the Land Use in the Basin and Nutrient Internal Load
AUTHORS:
Santiago A. Echaniz, Alicia M. Vignatti
KEYWORDS:
Eutrophication; Trophic State; Total Phosphorus; Shallow Lakes; Internal Load; Land Use
JOURNAL NAME:
Journal of Environmental Protection,
Vol.4 No.11A,
November
29,
2013
ABSTRACT:
Phosphorus and nitrogen are essential nutrients
for living organisms. Their concentration in the water of an aquatic ecosystem
is one of the factors responsible for the trophic status of the lake and is
related to the soils of the region and to the human activities carried out in
their basins. These nutrients are also found in the bottom sediments, where
they can either be retained or re-enter the water column. Since the information
about the concentrations of nutrients in the water of some lakes of La Pampa
(Argentina) is fragmentary, the aim of this study is to describe the trophic
status of some shallow lakes of the semiarid center of Argentina and analyze
its relation with the human activities in their basins, the concentrations of
nutrients and organic matter and particle size distribution of sediments. To
this end, we studied ten shallow lakes subjected to different anthropogenic
influences (agriculture,
agriculture and livestock and impacted by cities). All were hypertrophic and
the concentrations of total phosphorus and total nitrogen were among the
highest reported globally. Since some lakes had no fish, cladoceran grazing
(top-down effect) led them have reduced concentrations of phytoplankton
chlorophyll-a and high water
transparency. This relativizes the use of these parameters to determine the
trophic status. The
sediments of seven of the studied lakes were predominated by fine sands,
whereas three were predominated by silts. Nutrient and organic matter content
were high, with higher concentrations in lakes with prevalence of fine
particles. The reduced adsorption capacity of sediments, the resuspension by
wind, the anthropogenic input and the accumulation favored by the arheic
character of the basins would explain the high concentrations of nutrients in
the water of these Pampean environments.