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Benthic Microalgae (=
microphytobenthus) are microscopic single celled algae (diatoms
and dinoflagellates) and cyanobacteria that inhabit the top 0-3
cm of aquatic sediments. Benthic microalgae biomass is detected
and quantified by sediment chlorophyll a analysis. A comprehensive
survey of chlorophyll a content of Moreton Bay sediments
has shown that Benthic microalgae are ubiquitous, although concentrations
vary greatly. Benthic microalgae biomass is highly variable and
ranged from 1 - 120 mg chl a m-2 and was influenced
by water depth and turbidity.
Ecological significance of benthic microalgae
Benthic microalgae (BMA) are ecologically significant in coastal
marine environments from corals reefs to estuaries. They are a major
food source for benthic feeders such as prawns and other crustaceans,
bivalves and polychaete worms. Suspension feeders, such as polychaete
worms and oysters, may also graze on them when they are resuspended
into the water column due to current or tides BMA excrete polysaccharides
which bind the sediment and minimise the influence of overlying
water movements. This results in an increase in sediment stability
reducing the potential for sediment erosion and resuspension. BMA
communities also modify nutrient exchange, particularly nitrogen,
between the water column and sediments and hence may play an important
role in regulating water quality. Despite these crucial ecological
roles, BMA communities in Moreton Bay remain relatively unstudied.
Clearly, they are a component of the marine flora which requires
further research and understanding.
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