Coast & Estuaries
Page 209
shading the seagrass leaves from sunlight, further contributing to their loss.
Ambient water quality monitoring may detect elevated nutrients, particularly in
close proximity to the discharge, but may not detect any significantly elevated
nutrients in other areas which lead to damage of ecosystems. Other factors,
such as turbidity, suspended solids and colour (coloured dissolved organic
carbon) affect the transmission of light, which also hinders the growth of
seagrasses (EPA, 2008: Port Waterways Water Quality Improvement Plan).
The propagation of nuisance algae (particulary
Ulva
sea lettuce), algal blooms
and epiphytic growth (parasitic plants growing on other plants) on seagrass, is a
result of nutrient enrichment. To date there has been no quantitative data
collected on plant biomass although the level of chlorophyll (a) is used as a
general indicator of primary productivity. The role of macro-algae will be
addressed in the further development of the EPA decision support system as
part of the Port Waterways Water Quality Improvement Program (DSS) (WQIP
EPA, 2008).
The Port Adelaide Waste Water Treatment Plant sludge outfall operated for 15
years and was located in the north Lefevre Peninsula in close proximately to a
365 ha area of sea grass loss.
Before the sludge discharges commenced at Port Adelaide there was about
70% cover of
Posidonia
sea grass in the area. Within two years it had reduced
to zero. That continued for the duration of the15 years the outfall was open
(South Australian Museum, 2008).
