Biodiversity
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Mangrove Cove
Mangrove Cove, also known as the Ethelton Mangroves, is located on the
upper reach of the Port Adelaide River in Port Adelaide, just north of the railway
bridge. It is a small remnant of a previously extensive fringe of mangrove
communities along the length of the Port Adelaide River.
The large residential development to the north of the Ethelton mangroves
(known as Newport Quays) led to the preparation of the Mangrove Cove
Management Plan (Delta 2005). The Plan's implementation by Council ensures
the ongoing management of the area as an ecological and community asset.
Threats to ecological values
Mangrove Cove is a very small reserve, surrounded by commercial and
industrial users, a railway line, a school, and residential development. There are
ongoing risks to the site from maritime and terrestrial invasive species of plants
and animals, illegal domestic and commercial dumping, stormwater run-off from
increased areas of sealed land surface in the residential subdivision, noise
intrusion from the railway, non-commercial bait digging, mangrove incursion,
and tidal or sea level changes.
Mangrove incursion (expansion inland) is identified as something that poses a
threat to mangrove habitat regeneration. Mangrove and saltmarsh habitats are
'seral' or 'change habitats', meaning their boundaries do not stay the same over
time, but change to reflect sea level (tidal) change and sediment supply,
therefore need space to regenerate.
The reasons for habitat change can be
quite complex, however the prime reason for mangrove expansion landward in
this case is likely to be relative sea level change. The relative sea level at Port
Adelaide has been changing rapidly. Reasons may include being in the graben
zone of the horst and graben formation that results from the Para Fault and
other local fault lines, oxidation and compression of underlying quaternary
coastal alluvial deposits, and actual sea level rise due to warming oceans. In
Mangrove Cove (and some parts around the Barker Inlet Wetlands) the
mangroves are expanding rapidly as there are currently mud-flats present,
however in the longer term it is predicted that there will be limited space for
mangrove regeneration due to reduced land availability. (P. Coleman & F.
Cook, 2009).
The Barker Inlet (particularly where saltmarsh is trapped between the
mangroves and the seawalls) has gradually been over run with mangroves
since the 1940s and now very little saltmarsh remains. A monoculture of
mangrove has lower biodiversity value than an area that includes both
mangroves and salt marsh. The obvious differences can be seen in vegetation
diversity and wader bird habitat, both of which are smaller in a mangrove
monoculture. In the case of Mangrove Cove, allowing such changes to occur
without an adaptive management response in place will result in the reduction in
biodiversity value (vegetation species diversity, mud flat in-fauna and wader bird
