3.1. Epifaunal Community Structure
Grazing invertebrates comprised 53% m-2 of total
epifauna recorded in seagrass beds in Langebaan Lagoon (Table 3.1). This
group was dominated by the generalist microgastropod Assiminea
globulus (31.45% m-2) and the pulmonate limpetSiphonaria compressa (16.12% m-2). The keyhole
limpet Fissurella mutabilis was only found in beds in the low
shore zone comprising 3.26% m-2 of total epifaunal
abundance (Table 3.1). Seagrass beds also supported 43.45%
m-2 of predatory species, mainly the non-native
anemone, Sargartia ornata (43.38% m-2).
Dominant at sites closer to the lagoon mouth, this species was generally
found in spring and autumn. In its native habitat (Mediterranean and
Western Europe), S. ornata attaches to kelps and rocky shores,
however in Langebaan Lagoon it is found among Zostera shoots
attached to loose rocks and feeds mainly on amphipods and polychaetes
(Robinson & Swart, 2015).
The hermit crab, Diogenes brevirostris had a dual function as
grazer and deposit feeder and comprised 2.67% of total abundance. A
small percentage (0.83%) of suspension feeding organisms was also
encountered, the most abundant being a solitary ascidian, Pyura
stolonifera (0.4%), found mainly growing in sediment between seagrass
shoots (Table 3.1).