PEREZ Alejandra patricia
Optical characteristics of shallow lakes from the Pampa and Patagonia regions of Argentina
GONZALO LUIS PÉREZ; ANA TORREMORELL; JORGE BUSTINGORRY; ROBERTO ESCARAY; ALEJANDRA PATRICIA PÉREZ; MARÍA DIÉGUEZ; HORACIO ZAGARESE
Lugar: Munich; Año: 2010 vol. 40 p. 30 - 39
Fifteen Argentinean shallow lakes from the Pampa plains and the Patagonian steppe were characterized using optical properties and water-quality parameters. In this set of lakes a wide range in water transparency descriptors was observed [kd PAR varied from 0.4 to 47 m-1, Secchi disk (Sd) from 0.07 to 12.00 m, and nephelometric turbidity (tn) from 0.5 to 114.7 NTU]. Among Pampean lakes, high turbid lakes presented significant higher kd PAR values (> 13 m-1) than clear vegetated ones (< 10 m-1), though clearest Patagonian lakes showed significant lower light attenuation (kd PAR < 2.5 m-1) (t-test, p < 0.005). Our estimations of light scattering were supported by the significant relationship funded between tn and Effler´s scattering coefficient estimate. Allowing for lakes with tn < 80 NTU we obtained a significant linear regression with a slope close to the unity (R2 = 0.94, p < 0.001, n = 9). The two most turbid lakes (turbidity > 100 NTU) departed from this relationship. Considering absorption and scattering processes, in Pampean lakes CDOM absorption and tn explained 94 % of the observed variation in kd PAR. In contrast in Patagonian lakes, CDOM alone explained 89% of kd PAR variability. Although we found significant relationships between kd, Sd and tn over the whole range of optical conditions, we noticed some caveats disparities between Sd, tn and light attenuation (e.g. Yalka and San Jorge lakes presented same tn value but differed in kd PAR of about 20 m-1). Our results showed that the direct measurement of kd with paired values of Sd and tn ,in addition with determination of the main absorbing components, are much more useful and precise way of describing underwater light availability and optical regimes than more common accesses based only on Sd or tn and water-quality parameters. These measurements could therefore improve our ability to understand, the conditions that regulate macrophyte vs. phytoplankton dominance, as well as other important management issues in shallow lakes.