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Verlorenvlei Estuary Management Plan
Part 5: Appendices
Sampling should be conducted at sstations distributed geographically along the entire estuary at
fixed intervals. A rough estimate for setting the distance between stations is to divide the length of
the estuary by 10 (i.e. if an estuary is 12 km long, the distance between stations should be about 1-2
km). Typically a representative number of stations for large estuaries are between 10 and 15.
Sampling stations should also be selected along cross sections. During each sampling survey, water
quality samples must also be taken in the river and in the near-shore marine waters (i.e. the water
sources).
Microalgae
Phytoplankton: To estimate phytoplankton biomass, collect duplicate samples for chlorophyll a at
the surface and 0.5 m depth intervals. Use a spectrophotometer for sample analysis before and
after acidification. Do cell counts (at 400 x magnification) on dominant phytoplankton species to
establish species distribution and composition, i.e. green algae, flagellates, dinoflagellates, diatoms
and blue-green algae. .
Benthic microalgae: Collect intertidal and subtidal benthic samples for chlorophyll a (biomass)
analysis. Collect 5 samples at each station. Analyse samples using a recognised technique, e.g.
HPLC.
Record the relative abundance of dominant algal groups, i.e. green algae, dinoflagellates,
diatoms and blue-green algae and identify the dominant species.
At each station also measure:
Water salinity and inorganic nutrients
Sediment particle size distribution and organic content
Light penetration PAR or Secchi disk).
Sampling should be conducted at 10 to 15 stations selected geographically along the entire length of
the estuary, covering the different salinity zone. Stations should preferably be set at fixed intervals.
A rough estimate for setting the distance between stations is to divide the length of the estuary by
10 (i.e. if an estuary is 30 km long, the distance between stations should be about 3 km).
Macrophytes
The following information needs to be captured from recent and any available historical aerial
photographs and ortho-photographs covering the entire estuary as defined by the geographical
boundaries:
Number of different habitats (plant community types;
Area covered by each plant habitat;
Historical change in area covered by plant habitat;
Extent of anthropogenic impacts (agriculture, flood plain development).
Field data need to be collected for ground truthing of aerial photographs:
Number of different plant habitats (plant community types;
Area covered by each plant habitat;
Species list for each plant habitat;and
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