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
HOLGAT RIVER ESTUARY: Ecology

	Flora
	Phytoplankton/Diatoms
	At the time of the ECRU survey, the water in the trench contained blue-green and filamentous algae (Chaetomorpha). Associated with the filamentous algae were many pennate diatoms. (Ref 1)
	Algae

	Aquatic Vegetation
	There was no evidence of aquatic vegetation in the lower reaches of the riverbed at the time of the ECRU survey. In the sea, kelp Ecklonia maxima was dominant. Other algae present were Gigatina radula, Aeodes orbitosa, Porphyra capensis and coralline aglae. (Ref 1)
	Semi-aquatic Vegetation
	Sarcocorna pillansii was present between the water trench and the beach at the time of the ECRU survey. (Ref 1)
	Terrestrial vegetation
	Contribution by Miss R Parsons, Botanical Research Institute, and Miss A le Roux, C.P.A Department of Nature and Environmental Conservation.) This area fall into Acock's Veld Type 34 (b) Strandveld Proper, which has many variations and can best be described here as an open, semi-succulent scrub (Acocks 1975) (Ref 1)
	All the vegetation was low, with a maximum height of 1,0m and an average height of 0,5m. Another common feature throughout is the leaf succulence, and adaptation frequently found in arid environments. The Sarcocornia pillansii Saltmarsh has the highest cover (80%) and the lowest species diversity. The Salsola sp. cf. zeyheri/Zygophyllum sp. cf. tuberculata/Lycium sp. (Le Roux and Parsons) Low Shrubland has the highest species diversity with 9 species recorded. (Ref 1)
	The vegetation for the areas studied is similar and the six vegetation mapping units can be consolidated into two main plant formations viz. saltmarsh and low shrubland (0,25 - 1,0m). The low shrubland is the most expensive, covering an area of about 28ha² and the saltmarsh an area of about 0,4ha, out of the total of 34 ha studied. (Ref 1)
	Fauna
	Zooplankton
	At the time of the ECRU survey, plankton sampling in the trench revealed the presence of large numbers of harpacticoid copepods, of which nearly half were in an ovigerous condition. Small white nematodes and cronomid larvae were also present. (Ref 1)
	Aquatic Invertebrates
	Cape Reef worm, rock lobster, ribbed mussel, black mussel, limpets, periwinkle, snail, whelk
	Insects
	Large number of kelp flies
	Fish
	White Steenbras, Galjoen, Hottentot, Kabeljou and mullet
	Amphibians and Reptiles

	Birds
	During the ECRU survey, the following species were noted: White-breasted Cormorant Grey Heron White-fronted Sandplover Sanderling Southern Black-backed gull Cape Wagtail Three-banded Sandplover Double-banded Sandgrouse Red-capped Lark Familiar Chat Cape Bunting (Ref 1)
	Mammals
	At the time of the ECRU survey, the tracks of a felid (probably the African Wild Cat, Felis libyca) as well as steenbok (Raphicerus campestris), were noted at the mouth of the estuary. Surface tunnels indicated the occurrence of a mole or a mole rat species.
	Black-backed Jackal (Canis mesomelas) are present in the vicinity of the Holgat as noted when a lactating female was killed by a shepherd at the time of the ECRU survey.
	The records of Stuart et al (1980) indicate that the Cape Fur Seal and the Black-backed Jackal have been recorded in the vicinity of the mouth of the Holgat. (Ref1)