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Coastal zooplankton communities of south eastern Tasmania


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Cazassus, F 2004 , 'Coastal zooplankton communities of south eastern Tasmania', Research Master thesis, University of Tasmania.

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The spatial variations of zooplankton communities (i.e. dispersion and retention) between
an inshore embayment and an adjacent offshore coastal site were investigated. Water
enters the bay by its northern shore and circulates through it in a clockwise direction
during an outgoing tide and an anticlockwise direction during an incoming tide.
Distribution of some species, such as Calanus australis, Temora turbinata, Noctiluca
scintillans, Podon sp, Penilia sp., showed a retention time in the bay of around 4 to 6
weeks. Although there is clear evidence that mixing occurred between the bay and the
channel via a complex combination of winds and tides, and no barrier or gradient could
be identified, some species were found only in the bay: examples are Oikopleura sp.,
crustacean larvae, Clausocalanus ingens, and Oithona sp., which were retained in the bay
probably through a combination of behavioural strategies e.g. vertical migration or
selective predation. Some oceanic species even maintained their position outside the bay
(Labidocera cervi), and were not found inshore.
Temporal and spatial variations of the surface zooplanktonic and neustonic
communities of the south east coastal waters of Tasmania were studied. Data on the
neuston in Australia are scarce and distribution atld life history of most of these species
are poorly known. Pontella novaezelandiae (Pontellidae, Copepoda) (Farran 1929) was
recorded for the first time in Tasmanian waters. Fifteen specimens were encountered
during summer 2000-01, whereas the previous records in the region were mostly in
autumn-winter off the North Island, New Zealand. In vitro observations of another
neustonic species, Labidocera cervi (Pontellidae, Copepoda) (Kramer, 1895), revealed
some diel migration patterns. Adults live within the surface 10 em layer during daylight
and spread throughout the water column just after dusk, and juveniles spend most of their
time at the surface, day or night. Some observations on the life history and ecology of
these two neustonic species are described.
The data obtained during 2000-01 sampling season were compared with earlier
data from 1971-73 sampled in nearby coastal waters. At the same site, using the same
methodology, two distinct communities were obtained in 1971-73 and 2000-01. The
importance of Antarctic and subantarctic species is greatly reduced compared to 1971-73
and the abundance of subtropical species has increased. These observations are supported
by changes in sea surface temperature and salinity off this coast during the last 45 years.
Changes in the zooplankton community cannot be explained by the ENSO cycle. These
changes are consistent with a regime shift that has been described in the North Pacific.

Item Type: Thesis - Research Master
Authors/Creators:Cazassus, F
Copyright Holders: The Author
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Copyright 2004 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

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