State of the Bay Report 2010-Final - Anchor Environmental

40%, co-occurring with sponges especially around rock-depressions (Figure 9.5). The pulmonate
false-limpet Siphonaria serrata could also be found in these depressions. Other algae were primarily
crustose corallines. Animals included the cushion star Parvulastra (=Patiriella) exigua, the scavenging
whelk Burnupena spp. and B. glandula.
Oxystele variegata
Blue-green algae
Afrolittorina knysnaensis
Porphyra capensis
Figure 9.4. Top left to bottom right: High shores at Dive School, Iron Ore Jetty, Schaapen West with blue
green algal cover, and at Marcus Island.
With increasing wave activity, mid shores were characterized by sessile filter-feeders such as
the alien barnacle B. glandula and the alien Mediterranean mussel Mytilus galloprovincialis. At Iron
Ore Jetty in particular, mid-shore barnacle spread could exceed 80% (Figure 9.5). Mobile animals
included the limpets Scutellastra granularis, Siphonaria serrata, S. capensis, few O. variegata and A.
knysnaensis seeking shelter amongst the barnacles (Figure 9.5). Algal cover was generally low with
the exception of the exposed site Marcus Island where ephemeral algae (e.g. Ulva spp.) flourished
(Figure 9.5). Other seaweeds included P. capensis, Caulacanthus ustulatus, and various coralline
algae.
Differences among sites were most pronounced in the low-shore zone were differences in
wave action is most effective. Generally, species cover was for all sites greatest in the low shore, but
a clear trend of increasing cover with increasing wave force is also noticeable (e.g. from 25% at Jetty
to 97% cover at Marcus Island). Sheltered low-shores were seaweed dominated, particularly by the
red alga Gigartina polycarpa, the crustose coralline R. verrucosa and the green alga Ulva spp. Filterfeeders,
on the other hand, were rare with the occasional barnacle and/or mussel. Despite this low
State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 197