Motility of Daphnia spinulata as affected by solar radiation throughout a year cycle in mid latitudes of Patagonia

J GONCALVES, RODRIGO; S BARBIERI, ELENA; VIRGINIA ESTELA VILLAFAÑE; WALTER HELBLING, E

PHOTOCHEMISTRY AND PHOTOBIOLOGY

Año: 2007 vol. 83 p. 824 - 832

0031-8655

During an annual cycle, Daphnia spinulata collected from aplankton community of Patagonia was exposed outdoors toassess the impact of recently received solar radiation on motility(i.e. swimming speed and gravitaxis). Individual values of theseparameters were obtained by video recordings and imageanalysis at different time intervals during the day. Initialswimming speed varied throughout the year, and changes inspeed during exposure were not significantly affected by anywaveband used in our experimental design (i.e. PAB, 280–700 nm; PA, 320–700 nm; and P, 400–700 nm). Overall, most ofthe individuals swam downwards, regardless of the radiationtreatment imposed to the samples. We found that multifactorinteractions (i.e. not a single parameter explained more than40% of the observed variability) explained most of our observationson motility parameters. These factors include not onlysolar radiation, but other physical (underwater radiation fieldand wind intensity) and biological parameters (food availability,presence of predators and congeners). Our findings indicate thatthe plankton dynamics in the study site is likely to be governedby a sum of factors which must be taken into account whenconsidering solar radiation effects on aquatic ecosystems.