Uilkraals Situation Assessment - Anchor Environmental

3.4 VegetationThere are four main vegetation communities associated with the Uilkraals Estuary: macroalgae,submerged macrophytes, reeds and sedges, and salt marsh.Heydorn & Bickerton (1982) recorded 13 species of semi‐aquatic plants in and around theUilkraals Estuary. These included Crassula glomerata, Plantago carnosa, triglochin bulbosum,Scirpus littoralis, Sebaea minutiflora, Sebaea albens, Spergularia marginata, Cotula eckloniana,Chenolea diffusa, Samolus deis and Limonium scabrum.MacroalgaeMacroalgae can be indicative of water quality and nutrient enrichment. Macroalgae may beintertidal (intermittently exposed) or subtidal (continually submerged) and can be attached tohard or soft substrata or they may float (Adams et al. 1999). Opportunistic macroalgae arefound in temporary closed estuaries like the Uilkraals as they can tolerate fluctuating salinities.During a survey in 1981 the filamentous algae Enteromorpha and Cladophora were recorded inthe estuary and Ulva beds were present under the road bridge (Heydorn & Bickerton 1982).Enteromorpha and Cladorphora belong to the family Chlorophyta, and are often found toextend further into estuaries due to their salinity tolerance (Adams et al. 1999).Submerged macrophytesThe high macrophyte diversity in the Uilkraals Estuary is of conservation importance. Thereare approximately 2 ha of submerged macrophytes in the estuary, which provide an importanthabitat for invertebrates and juvenile fish. Submerged macrophytes are plants rooted in bothsoft subtidal and low intertidal substrata, which are completely submersed for most states ofthe tide (Adams et al. 1999). Submerged macrophyte beds support diverse and abundantinvertebrate and juvenile fish communities (Whitfield 1984, 1989). Primary productivity ofsubmerged macrophytes is high and on par with the most productive plant habitats in marineand terrestrial ecosystems (Day 1981, Fredette et al. 1990). Adams et al. (1999) found in salinewaters in the region, Zostera capensis is prevalent. Submerged macrophytes are important intheir provision of food for epifaunal and benthic invertebrate species as well as nursery areasfor juvenile fish through the provision of food, shelter and protection (Adams et al. 1999).Salt marshSalt marshes in estuaries are a source of primary production and provide habitat and food for avariety of faunal species (Adams et al. 2006). The degree of tidal flushing is important indetermining how much nutrients they release into the water column (Childers & Day 1990).An open mouth is important as this maintains the intertidal salt marsh community. Salt marshplants are distributed away from the water’s edge along an inundation gradient (Figure 13).Intertidal salt marsh occurs between the limits of the high and low tide ranges, while supratidalmarsh occurs above the intertidal zone and is only normally flooded during spring tide andUilkraals Estuary Situation Assessment23Anchor Environmental