Contribution
Coincident zooplankton and phytoplankton diel migrations in a high mountain lake (La Caldera, Sierra Nevada, Spain)
Carrillo, P.; Sanchez-Castillo, P.; Cruz-Pizarro, L.
Archiv für Hydrobiologie Volume 122 Number 1 (1991), p. 57 - 67
41 références bibliographiques
publié: Aug 28, 1991
DOI: 10.1127/archiv-hydrobiol/122/1991/57
ArtNo. ESP141012201003, Prix: 29.00 €
Abstract
The high mountain lake, La Caldera, because of its morphometric, physico-chemical and biological characteristics, provides exceptionally favourable conditions to perform research on diel vertical migration patterns, particularly of phytoflagellates. Data from a 24 hour sampling program have revealed zooplankton to show, as a whole, a definite nocturnal migration, comparable to that previously described (Cruz-Pizarro, 1978, 1981; Carrillo et al., 1989). Within the phytoplankton, non-motile and close to neutrally buoyant species (mainly Cyanarcus sp.) showed a limited daily vertical movement remaining, for most of the cycle, at the upper/intermediate layers. These species were used as a reference against which to evaluate the vertical distribution of flagellates which, despite minor specific differences, exhibited a common pattern of migration (exemplified by that of Chromulina nevadensis) involving an evening upward movement and a return downward one after dawn, both roughly coinciding with the highest values of the relative rate of change in light. Zooplankton grazing might account for much of the observed day-night differences in biomass (and density) of motile algal species. Recruitments from narrow but unsampled water layers (such as the neuston) might also contribute to explain the unrealistic computed net growth rates for C. nevadensis in the early morning. Light is probably the stimulus for the algal movement. The possibility of exploiting rich nutrient micropatchiness generated by zooplankton excretion should be able to explain its adaptive value, as other major proposed hypotheses can be discounted in this particular environment.
Mots-clefs
phytoflagellates • physico-chemical • neuston • La Caldera • Spain