The effects of light availability, in shallow, turbid waters: a mesocosm study

LLAMES M.E.; LAGOMARSINO L.; DIOVISALVI N.; FERMANI P.; TORREMORELL A.; PÉREZ G.; UNREIN F.; BUSTINGORRY J.F; ESCARAY R.; ZAGARESE H.

JOURNAL OF PLANKTON RESEARCH

Oxford University Press

Lugar: London; Año: 2009 vol. 31 p. 1517 - 1529

0142-7873

Abstract Seasonal patterns of water transparency in turbid Pampean lakes suggest that the amount of suspended particulates is highly influenced by incident solar radiation. However, the unequivocal identification of light as the major forcing variable is precluded due its co-variation with several potentially confounding variables. In order to specifically investigate the role of light, we performeda mesocosm (3000 L) experiment aimed at investigating the effects of different degrees of light availability on planktonic community structure and metabolism. The experimental setup successfully mimicked the light limiting conditions prevailing in Pampean turbid lakes. We used neutral density filters to obtain four light treatments, roughly covering the natural annual range of incident irradiances. Our results are consistent with field patterns and light-limitation theory: (i) light attenuation and (ii) primary production increased with light availability. In contrast, the abundance of most grazers displayed negative relationships with light availability. The decreases in the density of grazers could have resulted from changes in the nutritional value of the food. This possibility is also supported by (iii) decreases in seston P-content and (iv) increases in community respiration with increasing light availability.