State of the Bay Report 2010-Final - Anchor Environmental

the species associated with it (Siebert and Branch 2005, Angel et al. 2006). The long-term effects of
the loss of seagrass at Klein Oesterwal, and to lesser degree at Bottelary and the Central banks, are
not yet fully understood. However, studies suggest that the reduced seagrass bed coverage and the
associated changes to macro-invertebrates may have cascading effects on higher trophic levels
(Whitfield et al. 1989, Orth et al. 2006). Alterations to fish species diversity and abundance, and
changes in the numbers of water birds that forage or are closely linked to seagrass beds may be seen
in Langebaan Lagoon as a result of the loss of seagrass beds (Whitfield et al. 1989, Orth et al. 2006).
The loss of seagrass beds from Langebaan Lagoon is a strong indicator that the ecosystem is
undergoing a shift, most likely due to anthropogenic disturbances. It is critical that this habitat and
the communities associated with it be monitored in future as further reductions are certain to have
long term implications, not only for the invertebrate fauna but also for species of higher trophic
levels.
Figure 7.2. Width of the Zostera beds and density of Siphonia at Klein Oesterwal and Bottelary in
Langebaan Lagoon, 1972-2006.
State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 150