State of the Bay Report 2011-Final.pdf - Anchor Environmental

State of Saldanha Bay & Langebaan Lagoon 2011
Intertidal invertebrates
Scutellastra cochlear surrounded
by encrusting coralline
Mussel patches with secondary algae
growth
Aulacomya ater
Figure 8.7.
From top left clockwise: Scutellastra cochlear patch in association with ‘pink’ encrusting
coralline algae on a low shore boulder at Lynch Point; overview of the low shore at North
Bay showing kelp growing in the infratidal; Aulacomya ater patch at the low shore at
Marcus Island; overview of the low shore at Marcus Island.
With a further increase in wave action, the low intertidal became progressively
dominated by sessile filter-feeders, particularly M. galloprovincialis with up to 40% cover at North
Bay (Figure 8.7). At Marcus Island, the indigenous ribbed mussel Aulacomya ater occurred in
patches and could locally be more dominant than M. galloprovincialis (Figure 8.7). This is in stark
contrast to the mid shore, which is clearly dominated by the alien mussel and also to earlier years,
where the alien mussel was the characterizing mussel species at this site (Robinson et al. 2007).
Barnacle presence was largely restricted to secondary growth of Notomegabalanus algicola on
mussel shells. Mobile fauna was characterized by dense patches of Scutellastra cochlear as well
as S. barbara, S. granularis and the kelp-trapping S. argenvillei, Cymbula granatina, C. miniata and
Fissurella mutabilis. The predatory whelks Burnupena spp. and Nucella cingulata were found
hidden in the mussel matrix, feeding on mussels. Encrusting and, to a lesser degree, articulated
corallines were the main algae species. Foliose seaweeds were represented by Champia
lumbricalis and Plocamium spp., which are typical for wave swept shores, and minor cover of
Sarcothalia stiriata, Ulva spp., red turf, and Laminaria pallida at the infratidal fringe (Figure 8.7).
In S. cochlear patches, narrow gardens of fast-growing, fine red algae (e.g. Gelidium micropterum,
G. pristiodes, Herposiphonia heringii) fringed larger individuals; the gardens serve as food source
and are territorially defended and fertilized by the limpets (Figure 8.7).
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