Abstract ID
biodiv49
Type
Oral
Theme
biodiv
Full title
Assessing impacts of water-level regime on aquatic macroinvertebrates in the Okavango Delta
Abstract text
Aquatic macroinvertebrate diversity and community compositions are known to vary both spatially and
temporally in response to several environmental factors. Effective conservation of macroinvertebrates in the
Okavango Delta requires an in-depth understanding of their spatio-temporal variations and factors driving these
variations. In wetland systems hydroperiod (duration and quantity of surface water on a wetland) is one of the
major factors governing aquatic macroinvertebrate community structure, diversity and abundance. The
hydroperiod in the Okavango Delta is controlled by the seasonal flooding regime and to a lesser extent by local
precipitation. Hydroperiod gradients within the Okavango Delta are important for maintaining high
vegetation-habitat diversity. Aquatic macroinvertebrates were collected from over 100 sites in six areas
spanning several hydrological gradients in the Okavango Delta. The main criteria for the selection of sites was
to maximise the diversity of organisms collected with respect to flooding frequency, hydroperiod and habitats
across the Okavango Delta. At each site, sampling of assemblages was done on at least three vegetation types
for exactly two minutes using a scoop net. Habitats characterized include marginal vegetation (MV) in
channels, lagoons and backwaters, inundated floodplains, floating vegetation, submerged vegetation and
seasonally flooded pools. A total of 62 aquatic macroinvertebrate taxa were identified from this study. Our
results indicate that major significant drivers of aquatic macroinvertebrate variability in the Okavango Delta
include hydroperiod, seasonal flooding regime and habitat variability. Macroinvertebrate diversity within the
Delta tends to be high in sites with a relatively short hydroperiod, in seasonally inundated habitats especially
floodplains and during high water conditions. Since diversity of aquatic macroinvertebrates is highest during
high floods and on seasonal flood plains, any hydrological developments that may compromise the flooding
extent of the Okavango Delta system will impact on the diversity of aquatic macroinvertebrates and hence on
the general diversity of the Okavango Delta.
Submission date
2009-10-24
Keywords
aquatic macroinvertebrates, hydroperiod, Okavango, biodiversity
Will be submitting paper?
Yes