| For
decades Careel Bay has been an important site for coastal wetland
study and research by community groups as well as primary and
secondary school students and university lecturers and students.
Careel
Bay, on Pittwater, like the other few remaining estuarine wetland
areas in Sydney, is an environmentally sensitive and important
area which needs to be protected and managed. It contains a combination
of natural features rare in the Sydney
region, which provide habitat for some important marine life and
bird species.
Sedimentary
processes
Sedimentary processes in Careel Bay are influenced by the geological
history of the land mass, recent weather patterns, tide and human
activities. The Pittwater Council Careel
Bay Wetland Plan of Management 1998
emphasises the significance of the sedimentary processes and the
need to conserve geodiversity and natural systems within the Bay
as well as minimising the risk of pollution within the Bay.
Mangroves
and saltmarsh
Careel
Bay contains the largest stand of mangroves, one of the last remnants
of saltmarsh (an Endangered Ecological Community in NSW, and the
most extensive sea grass beds in Pittwater. These act together
as a silt-stabiliser and fish nursery and are essential to the
ecology of Pittwater and nearby coastal waters. These ecosystems
provide habitat for some unusual resident and visiting bird species.
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| Careel
Bay mangroves
(T.Wilson CEC) |
Bird species
Careel
Bay’s rich bird population includes White-bellied Sea Eagles and Whistling Kites nesting in trees on the hills above Pittwater,
Ospreys, Little Penguins from Lion Island, Cormorants, Pelicans and a pair of endangered Bush Stone Curlews.
Careel Bay is a stop-off site on the East-Asian/Australasian
Flyway for migratory wading birds, which arrive in spring from
their breeding grounds in Mongolia and Siberia.
Careel Bay has a combination of seagrass beds
and mudflats rich in marine life on which the birds feed, a sand
spit where they can roost at high tide and a stand of mangroves
which is also used as a roosting area.
The
migratory birds including Eastern Curlews, Whimbrels and Bar-tailed
Godwits spend the summer resting, moulting and feeding to build
up the fat reserves necessary for the long trip back to the northern
hemisphere where they breed.
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| Spoonbills
feeding |
Australia is committed to a number of international agreements
for the protection of these birds and their habitats. These agreements
include JAMBA (Japan-Australia Migratory Bird Agreement) and CAMBA
(China-Australia Migratory Bird Agreement).
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Pittwater’s Grassy Meadows
Pittwater
has nearly two square kilometres of native “grassland”, home to
some interesting animals, large and small.
In
wide expanses in Pittwater’s shallow bays and in narrow strips
along the steeper shore, grow the seagrasses. These are flowering
plants, like land grass in form, which need sunlight and grow
from rhizomes.
Three
species are found in Pittwater: Posidonia australis, Zostera
capricorni, and Halophila ovalis with a fourth Heterozostera
tasmanica recorded in deeper water of Careel Bay (HH & R 1974).
Posidonia
(Poseidon, Greek god of the sea), here close to its northern limit
of distribution, grows slowly, may not regenerate if damaged and
is difficult to restore once lost. It has wider, strap-like leaves
and usually grows in deeper water adjoining the Zostera, with
usually only its landward edge exposed by the lowest tides, while
the Zostera beds may be fully exposed at low tide. Both may produce
small flowers, the pollen carried by the current. Fruits of Posidonia
may be seen washed up on the tide line in early summer along the
shore of Careel Bay, a sign of the very good health (for the Sydney
region) of the Bay’s Posidonia (P.
Hutchings, pers comment, 2004)
Seagrasses
are vital as a fish habitat and fish nursery, and in filtering
sediment, stabilising the estuary floor and preventing shoreline
erosion. A fragile habitat, they are easily damaged by excess
water turbidity, or overgrowth of algae blocking light, and by
direct damage as by some boating activities and inappropriate
development. Previous large areas at the head of Pittwater have
been lost to reclamation and marinas. Many major estuaries in
NSW have lost up to two thirds of their seagrass beds in the past
30 to 40 years.
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Seagrass
food chain
Near
the tops of the seagrass food chain are the fishes, living in
the seagrass and moving out to adjoining areas with the tides.
The Careel Bay seagrass beds have recorded large numbers of young fish of commercially
important species e.g. trevally, bream, tarwhine, whiting and
leatherjackets which depend on shallow seagrass beds for their
early growth and survival, before moving out to other habitat.
Other fish such as mullet form an important part of the estuarine
food chain and channel the high organic production of the seagrass
and mangroves into larger commercial species.
Many
other different types of fish are found in the Careel Bay seagrasses. Recently a stingray probably a Brown (Estuary) Stingray
(Dasyatus fluviorum) approximately two metres long was
sighted resting quietly in the seagrass.
Common
Stingarees (Urolophus tesacea) small and with shorter tails
than Stingrays, are abundant in Careel Bay. Both are bottom dwellers and feeders, digging in the sand for invertebrates,
leaving shallow pits which can be seen over the sandflats at low
tide, and retreating into deeper water as the tide falls.
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Seahorses
and pipefish
Several
species of seahorses and pipefish (Syngnathidae) are also found
in seagrass. Both seahorses and pipefish have a small mouth at
the end of a tubular snout, and feed mostly on small crustaceans
on and among the seagrass blades. They have prehensile tails by
which they can anchor themselves to the vegetation. Their colouring
and shape (especially the pipefish which resembles a seagrass
blade) camouflage them among the seagrass.
In
Careel Bay there are abundant White’s Seahorses (Hippocampus whitei)
and Wide-bodied Pipefish (Stigmatophora nigra) The Spotted
Pipefish (Stigmatohora argus), Hairy Pipefish (Urocampus
carinirostris) and Large-bellied Seahorse (Hippocampus
abdominalis) have also been identified.
For
the protected Syngnathids, habitat degradation is a threat as
they mainly inhabit shallow coastal areas, which are highly influenced
by human activities including oil and sediment run-off and destruction
of sea-grass beds.
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| Oyster |
Spyrazus |
Orange
Shore Crab |
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The
vast proportion of the seagrass fauna is made up by the many species
of marine invertebrates – polychaete worms, bivalve molluscs,
and crabs in the mud, free-swimming animals such as prawns among
the leaves and on the leaves, tiny encrusting animals.
Other fish
and marine invertebrates at Careel Bay include:
- Eastern
Frogfish
- Eastern
Gobbleguts
- Cuttlefish
- Common
Sydney Ocotopus
- Feather
Duster Worm
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Soldier
crabs feeding on the Careel Bay mudflats |
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Noxious sea weed
Caulerpa taxifolia
was first noted in Pittwater at Careel Bay in December 2000. NSW Fisheries made several limited attempts to
control it between 2001 and 2003/4, but it has spread across in
front of the boatshed towards the proposed marina site and the
main seagrass beds.
The
problem with Caulerpa taxifolia:
- It
is fast growing but has a winter dormancy period.
- Fragments
can break off and start new colonies.
- It
can survive several days out of water in a damp situation.
- It
is found from very shallow water down to 20+ metres.
- It
is not eaten by most fish or invertebrates having a chemical
repellent.
- It
does not appear to provide a host surface for encrusting organisms
as (as seagrass does) and thus the habitat is reduced.
- It
is not as effective in silt-stabilising as is seagrass.
- If
it overruns seagrass it would disrupt the entire ecosystem.
- It
is present in a number of other NSW estuaries.
The
proposed Careel Bay marina development would facilitate the spreading of Caulerpa
taxifolia through the increase in the number and movement
of boats including big powerboats with large propellers and ability
to travel long distances.
In
1973, the Careel Bay mangroves and tidal flats were saved
from marina development by strong local protest and environmental
surveys. At that time an article in the Manly Daily stated, “only
continued vigilance and the determination of local residents will
prevent Careel Bay from going the way of all other similar inlets
on the eastern side of Pittwater.”
In
2005, the mangroves and tidal flats were again under threat, this
time by a Marina Development
Application proposed by Austral Monsoon Industries.
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