The differentiating effect of macrophytes on zooplankton composition in five eutrophic shallow ponds of the Woluwe river, Brussels.

Stijn Van Onsem, Ludwig Triest

Research output: Chapter in Book/Report/Conference proceedingMeeting abstract (Book)Research

Abstract

Shallow, nutrient-rich ponds are either in a clear or a turbid water state, depending on abiotic conditions and the interactions between the organisms present. Macrophytes play a key role in maintaining the clear water state, thanks to a series of feedback mechanisms, one of which is the control of phytoplankton by large zooplankton that finds shelter in the vegetation. In many studies, only the pelagic (open water) zone of ponds is sampled, so there is not much information available about the possible effect of different macrophytic vegetations on the zooplankton communities. The main objective of the current study is the determination of the relation between vegetation type and the densities and community structure of the zooplankton associated with vegetated habitats. Five vegetated ponds in the Woluwe valley were monitored monthly from July till October 2005.
Only those vegetated habitats that made up a significant part of each pond were considered. Environmental parameters (vegetation biomass and cover, water depth, nutrient concentrations,...) were measured and different zooplankton samples were collected within the vegetated zones or in the open water.
Three potentially influencing factors were considered: the habitat type (seven macrophyte species or combinations of species, and open water), the between-month variation (a part of the seasonal evolution) and the between-pond variation. To test for which of these factors differences in the zooplankton communities were most pronounced, the absolute and relative abundances were compared and multivariate analyses (PCA and cluster analyses) were performed. An RDA was undertaken to correlate zooplankton subgroups with environmental variables. Also, Shannon-Wiener diversity indices were calculated for each habitat type.
Zooplankton density as well as taxon composition varied between the different habitats. One pond (Grote Mellaertsvijver) contained high densities of small, pelagic zooplankton (mainly rotifers) as a result of its turbid character. Relative abundance comparison, PCA and cluster analyses revealed higher affinity of zooplankton between habitats within the same pond than between habitats of the same macrophytic species in different ponds. There was considerable between-month variation, with Daphnia populations increasing in autumn. Shannon-Wiener indices of total zooplankton were lowest in structurally open habitats, and higher in the denser vegetation.
Possible explanations for the high within-pond similarity are: the influence of dominant (with respect to cover) macrophytic species; the homogenizing effect of high flushing rates; and the determination of the zooplankton communities by local (i.e. characteristic for one pond) environmental conditions.
Future studies should focus on rarer zooplankton taxa in order to reveal typical associations with macrophyte species, irrespective of the location of these macrophytes.
Original languageEnglish
Title of host publicationPlant conservation in theory and practice
PublisherRoyal Botanical Society of Belgium
Pages33-33
Number of pages1
Publication statusPublished - 23 Nov 2007
EventFinds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet - Stockholm, Sweden
Duration: 21 Sep 200925 Sep 2009

Publication series

NameYoung Botanists' Day

Conference

ConferenceFinds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet
CountrySweden
CityStockholm
Period21/09/0925/09/09

Keywords

  • macrophytes
  • zooplankton
  • shallow eutrophic ponds

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