Coast & Estuaries
Page 198
a major role in the balance between erosion and deposition of sediments along
the coast and create clearer water (DEH, 2006).
Recent studies have also shown that mangrove areas have a greater carbon
sequestration capacity than rainforests, and their protection and expansion can
play a role in mitigating climate change. They may also have the potential to
generate carbon offsets.
The Dolphin Sanctuary
South Australia is home to the common bottlenose dolphin, the indo-pacific
bottlenose dolphin and the short-beaked common dolphin. The indo-pacific
bottlenose dolphin is the resident species of the Port Adelaide River and Barker
Inlet.
In June 2005 the
Adelaide Dolphin Sanctuary Act 2005
was proclaimed. The
object of the Act is to protect the dolphins and their habitat. The legislation sets
out the boundary of the Sanctuary (Figure 55, page 223) and arrangements for
the management of the species in this area. The Act required a Management
Plan to be developed within the first twelve months of the Act's operation.
The
Adelaide Dolphin Sanctuary Management Plan
(DEH 2008a) has identified
several water quality issues of concern within the Sanctuary boundaries in the
southern parts of the study area. Turbidity of the overlying waters is known to
impact the health of seagrass meadows. The turbidity is sourced from
suspended sediment in stormwater discharge and also from picoplankton
blooms that occur in the Sanctuary as a result of eutrophication (high nutrient
levels) from the wastewater treatment discharges at Bolivar.
Death of seagrass beds has occurred widely in the area between St Kilda and
Port Gawler. Where the meadows have died, wave action has increased,
eroding the beds, deepening the offshore area and changing the size
distribution of the sediments. Rectifying the causes of this turbidity is a high
priority action in the
Port
Waterways Water Quality Improvement Plan
, the
Adelaide
Coastal Water Quality Improvement Plan, and the Adelaide Living
Beaches Strategy.
Until late in the 20th century, the coastal dumping of toxic wastes was controlled
relatively poorly. As a result, the Barker Inlet environment was the recipient of a
variety of metal and organic pollutants, which have been deposited in the tidal
flats and seagrass meadows, and generally become attached to sediments at
the floor of the sea. Very little is known, quantitatively, about toxin release from
sediments.
Water Quality
The Port River–Barker Inlet system is of major ecological importance,
supporting commercial and recreational fisheries, resident bottlenose dolphins
