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

State of Saldanha Bay & Langebaan Lagoon 2011
Background to monitoring
environment. They are particularly sensitive to changes in sediment composition (e.g. particle size,
organic content and heavy metal concentrations) and water quality.
Rocky intertidal: Rocky intertidal invertebrates are also mostly short lived organisms (1-3
years) and as such are good indicators of short to medium term changes in the environment (months
to years). Rocky intertidal communities are susceptible to invasion by exotic species (e.g.
Mediterranean mussel), deterioration in water quality (e.g. nutrient enrichment), structural
modification of the intertidal zone (e.g. causeway construction) and human disturbance resulting
from trampling and harvesting (e.g. bait collecting).
Fish: Fish are mostly longer lived animals (3-10 years +) and as such are good indicators of
medium to long term changes in the health of the environment. They are particularly sensitive to
changes in water quality, changes in their food supply (e.g. benthic macrofauna) and fishing
pressure.
Birds: Birds are mostly long lived animals (6-15 years +) and as such are good indicators of
long term changes in the health of the environment. They are particularly susceptible to disturbance
by human presence and infrastructural development (e.g. housing development), and changes in
food supply (e.g. pelagic fish and intertidal invertebrates).
Alien species: A large number of alien marine species have been recorded as introduced to
southern African waters. South Africa has at least 85 confirmed alien species, some of which are
considered invasive, including the Mediterranean mussel Mytilus galloprovincialis, the European
green crab Carcinus maenas, and the barnacle Balanus glandula. Most of the introduced species in
South Africa have been found in sheltered areas such as harbours, and are believed to have been
introduced through shipping activities, mostly ballast water. Ballast water tends to be loaded in
sheltered harbours, thus the species that are transported often originate from these habitats and
have a difficult time adapting to the more exposed sections of the southern African coastline, but
are easily able to gain a foothold in sheltered bays such as Saldanha Bay.
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