|
Cabomba leaves
|
|
Cabomba flowers
|
The Problem
Cabomba (Cabomba caroliniana), or water fanwort, is
a fast-growing submerged aquatic weed that has the potential
to spread throughout the aquatic habitats of Australia. It
grows well in slow-moving water bodies, particularly where
nutrient concentrations are high. Cabomba prefers areas of
permanent standing water less than 3m deep and is often found
along the margins of lakes and reservoirs. However, it can
grow in deeper water.
The weed is easily recognised by its finely dissected underwater
leaves that are feathery or fan-like in appearance. The small
flowers (2cm diameter) have six white petals and yellow centres.
They often extend above the water's surface,
making weed infestations more visible during the summer months.
The submerged leaves of hornwort (Ceratophyllum demersum)
and water milfoil (Myriophyllum spp.) may be confused
with cabomba leaves, however neither of these plants produces
the showy emergent flowers of cabomba. Although cabomba produces
flowers, it does not produce seeds. Reproduction is entirely
vegetative and almost any fragment can grow into a new plant.
Cabomba originates from South America. It was brought into
Australia through the aquarium trade. The plant's tolerance
of fragmentation and ease of cultivation make it a desirable
aquarium plant. Cabomba was subsequently introduced into lakes
and streams accidentally through the dumping of aquarium water
and on purpose to enable cultivation for later collection
and sale.
|
Cabomba on boat trailer
|
|
|
Currently, cabomba is primarily found in rivers and dams
of coastal Queensland and New South Wales. However, isolated
populations occur from Darwin to Victoria. It is easily spread
across drainages on water craft, boat trailers and perhaps
by waterfowl. Cabomba is a declared weed throughout Australia
and it is illegal to propagate, move, or sell this noxious
plant.
Cabomba negatively effects the environment, recreational
activities, public safety, and water quality. The weed can
smother native submerged plants such as pondweeds (Potamogeton
spp.), stoneworts (Chara spp.), hornwort (Ceratophyllum
demersum), and water nymph (Najas tenuifolia).
Cabomba may also reduce germination of desirable native emergent
plants. Alteration of the flora has led to reduced populations
of platypus and water rats in northern Queensland. In southern
Queensland, cabomba appears to negatively effect populations
of the endangered Mary River cod.
The long stems of cabomba impede the movement of boats and
can get tangled in propellers, paddles, and fishing lines.
This makes many recreational activities less desirable in
areas infested with cabomba and thereby reduces tourism. In
addition, cabomba is a potential danger to swimmers who may
become entangled in the long stems. Cabomba also decreases
water quality for human consumption by tainting and discolouring
potable water supplies. It interferes with dam machinery,
such as valves, pumps, and aerators, with leads to increased
costs of maintenance.
|
Cabomba flowering in Lake MacDonald
Photo: Abyss diving
|
|
