Environmental changes affecting light climate in oligotrophic mountain lakes: the Deep Chlorophyll Maxima as a sensitive variable
BEATRIZ MODENUTTI; ESTEBAN BALSEIRO; MARCELA BASTIDAS NAVARRO; MARÍA SOL SOUZA; CECILIA LASPOUMADERES; FLORENCIA CUASSOLO
BIRKHAUSER VERLAG AG
Lugar: BASEL; Año: 2013 vol. 75 p. 361 - 361
North Patagonian Andean lakes from Argentina are high light/low nutrient environments that during summer stratification exhibit the development of a Deep Chlorophyll Maxima (DCM) at the metalimnetic layers, near 1% of surface PAR irradiance. Here, we analyse if the position of DCM change as a consequence of long time effect (global warming: glacial clay input) and short time effect (eruption: volcanic ashes). We perform different field studies: 1- an intrannual analysis of six lakes from different basins including the data of the 2011 volcanic eruption that cause an unexpected variation in water transparency, and 2- an intralascustrine analysis in which we compared different stations in a transparency gradient of Lake Mascardi, caused by glacial clay input in one end of the gradient. In these analyses we documented changes in the DCM depth and their relationship with different parameters. DCM development was not observed in coincidence with thermocline depth nor with nutrient distribution. In all cases, the only significant variables were Kd 320 nm and Kd PAR. Indeed, our study showed that suspended particles (glacial clay and volcanic ashes) may play a crucial role in transparent lakes impacting lake features as phototrophic biomass distribution along the water column. The increase of suspended solid coming either from glacial clay or from volcanic ashes produced a comparable effect provoking a decrease in light and a consequently upper location in DCM development. Thus, DCM development was a very sensitive feature to global changes as increase in temperature, that cause glacier recession, or regional changes caused by volcanic eruptions.