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

State of Saldanha Bay & Langebaan Lagoon 2011
Background to monitoring
Aside from monitoring concentrations of contaminant levels in water, sediments, and biota,
it is also possible, and often more instructive, to examine the species composition of the biota at a
particular site or in a particular environment to ascertain the level of health of the system. Some
species are more tolerant of certain types of pollution than others. Indeed, some organisms are
extremely sensitive to disturbance and disappear before contaminant concentrations can even be
detected reliably whereas others proliferate even under the most noxious conditions. Such highly
tolerant and intolerant organisms are often termed biological indicators as they indicate the
existence or concentration of a particular contaminant or contaminants simply by their presence or
absence in a particular site, especially if this changes over time. Changes in community composition
(defined as the relative abundance or biomass of all species) at a particular site can thus indicate a
change in environmental conditions. This may be reflected simply as: (a) an overall
increase/decrease in biomass or abundance of all species, (b) as a change in community structure
and/or overall biomass/abundance but where the suite of species present remain unchanged, or (c)
as a change in species and community structure and/or a change in overall biomass/abundance
(Figure 2.1). Monitoring abundance or biomass of a range of different organisms from different
environments and taxonomic groups with different longevities, including for example invertebrates,
fish and birds, offers the most comprehensive perspective on change in environmental health
spanning months, years and decades.
The various methods for monitoring environmental health all have advantages and
disadvantages. A comprehensive monitoring programme typically requires that a variety of
parameters be monitored covering water, sediment, biota and community health indices.
2.3 Indicators of environmental health and status in Saldanha Bay and
Langebaan Lagoon
For the requirements of the Saldanha Bay and Langebaan Lagoon State of the Bay monitoring
programme a ranking system has been devised that incorporates both the drivers of changes (i.e.
activities and discharges that affect environmental health) and a range of different measures of
ecosystem health from contaminant concentrations in seawater to change in species composition of
a range of different organisms (Figure 2.1 and Table 2.1). Collectively these parameters provide a
comprehensive picture of the State of the Bay and also a baseline against which future
environmental change can be measured. Each of the threats and environmental parameters
incorporated within the ranking system was allocated a health category depending on the ecological
status and management requirements in particular areas of Saldanha Bay and Langebaan Lagoon.
An overall Desired Health category is also proposed for each environmental parameter in each area,
which should serve as a target to be achieved or maintained through management intervention.
Various physical, chemical and biological factors influence the overall health of the
environment. Environmental parameters or indices were selected that can be used to represent the
broader health of the environment and are feasible to measure, both temporally and spatially. The
following environmental parameters or indices are reported on:
Activities and discharges affecting the environment: Certain activities (e.g. shipping and
small vessel traffic, the mere presence of people and their pets, trampling) can cause disturbance in
the environment especially to sensitive species, that, along with discharges to the marine
environment (e.g. effluent from fish factories, treated sewage, and ballast water discharged by
ships) can lead to degradation of the environment through loss of species (i.e. loss of biodiversity),
or increases in the abundance of pest species (e.g. red tides), or the introduction of alien species.
Monitoring activity patterns and levels of discharges can provide insight into the reasons for any
observed deterioration in ecosystem health and can help in formulating solutions for addressing
negative trends.
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