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Flora |
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Phytoplankton/Diatoms |
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At
the time of survery, olive green water was recorded throughout the
estuary. This would suggest the presence of phytoplankton. (Ref
1) |
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Algae |
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Filamentous
algae were observed throughout the estuary during the ECRU
survey. With the strongly saline conditions in the lagoon in
March 1981, there had been considerable mortality of algae as
indicated by a strong smell of hydrogen sulphide. (R Stauth pers.
comm.) (Ref 1) |
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Aquatic
Vegetation |
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Beds
of aquatic grass Potamogeton pectinatus were present in the southern
channel about 2,5km from the mouth during the ECRU survey. This
aquatic macrophyte, which is intolerant of moderate salinities is
probably only able to survive in the Groen due to the moderating
influence of spring water on the salinity in the upper reaches.
(Ref 1) |
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The
kelp Ecklonia maxima occurs in the nearshore region on the shoreline
adjacent to the Groen mouth and kelp plants are washed up on the beach
in substantial numbers. (Ref 1) |
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Semi-aquatic
Vegetation |
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Sarcocornia natalense formed a carpet on
the northern bank near the mouth and Sarcocornia pillansii fringed the
bank and spread around the upper channels of the estuary.
The upper channels is also contained
small cyperaceae near the top and were fringed with Juncus
acutus. (Ref 1)
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Terrestrial
vegetation |
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This
region falls into Acocks Veld Type, Standveld Proper, which is an
open, semi-succulent scrub (Acocks 1975).
On the northern side of the mouth there
are extensive sand dunes stabilized to a large extent by the
vegetation, one of the dominant species being Eragrostis
cyperoides. Parts of the water surface were completely covered
by a yellow-green filamentous algae which formed a dense mat. (Ref 1)
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Eighteen
main vegetation mapping units were identified.
The Ruschia sp. Dwarf Shrubland had the
lowest cover with a total cover of on 1% while the Sarcocornia spp
Saltmarsh had the highest cover (100%). The average cover of the
vegetation appears to be between 30 and 40%. This low cover in
indicative of the arid environment. The vegetation mapping unit
with the highest species diversity was found on stable white sand just
above the rock front to the north of the mouth (Othonna sp./ limonium
equisetinum/Chrysocoma Dwarf Shrubland). This is probably a type
of Succulent Karoo, with 15 species being recorded here. (Ref 1)
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The
Eragrostis cyperoides Hummock Dune Grassland had the lowest species
diversity with only 1 species recorded. The 18 mapping units can
be considated intor four main plant formations: grassland, dwar
shrubland, low shrubland and saltmarsh. Of these the low
shrubland was the most extensive, covering an area of agou 68,50ha,
followed by dwarf shrubland (9,16ha), grassland (8,37ha) and saltmarsh
(6,03ha) out of the total area of 135,66ha studied. (Ref 1) |
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Fauna |
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Zooplankton |
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Aquatic
Invertebrates |
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Crumb-of-bread
sponge, Cape reef worm, Spiny lobster, Black mussel, Ribbed mussel,
Blue periwinkle, Periwinkles, Whelks, Limpets |
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Insects |
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Tenebrionid
beetles |
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Fish |
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Amphibians
and Reptiles |
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Tortoise |
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Birds |
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List
of birds found in the estuary (Ref 1) |
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Mammals |
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Cape
Wild Cat, Caracal, Striped Mouse (Ref 1) |
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