ESTUARIES IN SOUTH AFRICA

Main Page	General Information	Catchment Characteristics	Land and Estuary Uses	Water Quality
Threats	Hydrodynamics and mouth dynamics	Physical Features	Climate	References
GOURITZ ESTUARY: Ecology

	Flora
	Phytoplankton/Diatoms

	Algae
	Macroscopic algae (Porphyra capensis) are not abundant in the estuary, but occur on the rocky, eastern bank at the mouth. In 1987, no macrophytes were found within the estuary.Ref.1.
	Aquatic Vegetation

	Semi-aquatic Vegetation

	Terrestrial vegetation
	Two veld types of terrestrial vegetation were represented in the lower reaches of the Gourits River, namely the Coastal Renosterveld and the Coastal Macchia (Ref. 10).
	Eleven vegetation types have been identified (Ref.1.), namely:
	Arid scrub thicket : Dominant tree species are the Sideroxylon inerme and the Euclea racemosa. Sub-tropical thicket species include Rhus longispina and Scolopia zeyheri. Other locally conspicuous species are the white aloe and Euphorbia species.
	Renosterveld : The species composition is secondary in response to the impacts of fire and stock pressure and although considered to be relatively diverse, it is dominated by Elytropappus rhinocerotis. Other dominant genera include Eriocephalus, Anthospermum, Passerina, Relhania, Aspalathus, Helichrysum, Pteronia, Selago, Felicia and Hermania.
	Strandveld: The area consists of a mosaic of bushclumps, restios and shrubs, with a conspicuous graminoid and herbaceous ground layer (Ref. 1). The bushclumps are dominated by Sideroxylon inerme, Schotia afra and Pterocelastrus tricuspidatus (Ref. 1). The dominant restio species are Thamnochortus bachmannii, Chrysanthemoides monilifera and Phylica axillaries var. maritime (Ref. 1). The herbaceous ground layer comprises mainly Themeda triandra and Agathosma muirrii I(Ref. 1).
	Strandveld-thicket mosaic: The dominant woody species include Euclea racemosa, Sideroxylon inerme and Rhus longispina. The dominant shrub in the area is Zygophyllum morgsana. Two aloe species occur, namely Aloe ferox and A. arborescens (Ref. 1).
	Dune scrub: The dense scrub is dominated by Euclea racemosa, Tetragonia decumbens, Trachyandra divaricata, Salvia africana-lutea and Restio eleocharis (Ref. 1).
	Dune shrubland : Dominant shrub species include Myrica cordifolia, Chrysanthemoides monilifera and Stoebe plumosa. Common grasses are Ammophila arenaria, Ehrharta villosa and Senecio elegans (Ref. 1).
	Acacia cyclops thicket: Scattered clumps of the exotic species, Acacia cyclops occur. It can spread rapidly and should be eradicated (Ref. 1)
	Saltmarsh : The saltmarsh vegetation is not particularly well developed. Sarcocornia pillansiae is dominant on both banks at the mouth. Other species include Chenolea diffusa, Sporobolus virginicus, Juncus acutus, J. kraussii and Phragmites australis. Cotula coronipifolia and Triglochin species occur at the lower tidal levels, forming saltmarsh lawns.
	Dune thicket : A dune thicket of up to 3m occurred on the western bank of the estuary. The most conspicuous species are Sideroxylon inerme, Euclea racemosa, Pterocelastrus tricuspidatus and Clausena anisata (Ref. 1).
	Limestone fynbos: The most common protea species are Protea repens, P. susannae, and P. lanceolata, as well as Leucospermum praecox and Leucadendron galpinii. Heavy infestations of the exotic Acacia cyclops were evident in 1989 (Ref. 1).
	Secondary grassland: This secondary grassland use to be fynbos, but was converted by agriculture.
	Fauna
	Zooplankton
	In 1989 no data was available on zooplankton in this estuary (Ref. 1).
	Aquatic Invertebrates
	On the western bank, the aquatic invertebrates are dominated by the mud prawn, Upogebia, as well as at Steentjies-se-Gat. Bloodworms (Arenicola) were rare. Some Callianassa kraussii were also observed on the east bank, about 6,5km from the mouth (Ref. 1).
	Insects

	Fish
	Fresh water fish species recorded in 1943, included Cape galaxies (Galaxias zebratus), kurpur (Sandelia capensis), moggel (Labeo umbratus), and 3 barber species (Barbus asper, B. tenius and B. anoplus) (Ref.11).
	In 1957 Van Wyk (in litt.) reported the following marine fish species: Harders, kabeljou, white streenbras, elf and possibly leervis. Sea barbells (Galeichthys sp.) occur in the river.
	Amphibians and Reptiles
	Amongst the amphibians and reptiles, 11 species of amphibians, three species of tortoises, 26 species of snakes and 12 species of lizards, none of which are rare or endangered, were reported by several authors between 1943 and 1984.
	Birds
	The birds at the Gourits Estuary have been studied by several scientists. Summers et al. (Ref. 4) recorded 12 species (among a total bird count of 292 birds) of waders at the estuary mouth in 1976. In 1981 Underhill and Cooper reported a total of 1250 50 of 78 different species (Ref. 12).
	Mammals
	Few mammal species records are available. Only three species have actually been recorded, namely the Cape dassie, the Cape porcupine and the Cape mole-rat. A further 77 species may occur in this area, of which 8 species (Ref. 13) are rare or vulnerable.