INVESTIGADORES
BALSEIRO Esteban Gabriel
artículos
Título:
The role of macroinvertebrates and fish in regulating the provision of refugia for zooplankton by macrophytes in a warm temperate shallow lake.
Autor/es:
GONZALEZ SAGRARIO M.A.; BALSEIRO, E.G.
Revista:
FRESHWATER BIOLOGY (PRINT)
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Año: 2010 vol. 55 p. 2155 - 2166
ISSN:
0046-5070
Resumen:
1. The zooplankton often undergoes diel
horizontal migration (DHM) from the open water
to the littoral of shallow lakes, thus
avoiding predators in the former. This behaviour has
functional impacts within the lake, as it
enhances zooplankton survival, increases their
control of phytoplankton and tends to
stabilise the clear water state. However, most of the
evidence supporting this migration pattern
comes from cold north temperate lakes, and
more evidence from tropical and subtropical
areas, as well as from southern temperate
areas, is needed.
2. We conducted a field study of the diel
horizontal and vertical migration of zooplankton,
and the horizontal distribution of
potential predatory macroinvertebrates and fish, over
two consecutive days in the summer in a
temperate lake in the southern hemisphere. We
took zooplankton samples at two depths, at
three sampling stations (inside beds of aquatic
macrophytes, at their edge and in open water)
along three transects running from the
centre of a bed of Ceratophyllum demersum to open water. At each sampling station, we
also
took samples of macroinvertebrates and fish
and measured physical and chemical
environmental variables.
3. Zooplankton (pelagic cladocerans,
calanoid copepods and rotifers) avoided the
shore, probably because of the greater risk
from predators there. Larger and more
vulnerable
cladocerans, such as Diaphanosoma brachyurum and Moina micrura, were
two to
four
times more abundant in open water than at the edge of or inside beds of
macrophytes,
respectively,
by both day and night. Less vulnerable zooplankton [i.e. of medium body size
(Ceriodaphnia dubia) or with the ability to
swim fast (calanoid copepods)] were distributed
evenly
between open water and the edge of the plant beds. Small zooplankton, Bosmina
huaronensis
and pelagic rotifers, showed an even
distribution among the three sampling
stations.
Accordingly, no DHM of zooplankton occurred, although larger organisms
migrated
vertically inside C. demersum stands.
4. Macrophytes contained high densities of
predatory macroinvertebrates and fish. The
predator
assemblage, composed of large-bodied macroinvertebrates (including odonates
and
shrimps) and small littoral fish, was permanently associated with submerged
macrophytes.
None of these groups moved outside the plant beds or changed their
population
structure (fish) over the diel cycle.
5.
Submerged macrophyte beds do not represent a refuge for zooplankton in lakes
where
predators are numerous among the plants, implying a weaker top-down control of
phytoplankton
biomass by zooplankton and, consequently, a more turbid lake. The
effectiveness
of macrophytes as a refuge for zooplankton depends on the associated
assemblage of predatory macroinvertebrates and fish among the plants.