CPR detects the red-tide dinoflagellate Noctiluca scintillans in the Southern Ocean for the first time
David J. McLeod, Gustaaf M. Hallegraeff, Graham W. Hosie and Anthony J. Richardson
Noctiluca scintillans is a red-tide forming,
heterotrophic dinoflagellate that was found for the first time in
the Southern Ocean (45°31´S 147°E) in December, 2010. The 'bloom'
of Noctiluca extended over 242 km and was detected during
a CPR transect conducted between Tasmania and Antarctica as part of
the Southern Ocean CPR (SO-CPR) and Australian CPR (AusCPR)
Surveys. This record of Noctiluca is the most southerly,
oceanic record globally and can be linked to the intensification of
the East Australian Current (EAC), a situation apparently caused by
altered circulation patterns associated with global warming.
The east coast of Australia has been recognised as a climate
change 'hotspot' and poleward migrations of a number of species in
the region have already been documented including phytoplankton,
zooplankton, invertebrates and coastal fish. On present evidence,
the current observation of Noctiluca in the Southern Ocean
is an extension of coastal Tasmanian populations. Sea surface
height and sea surface temperature data at the time indicated that
a warm-water eddy of the EAC extending to Tasmania and beyond
provided a potential vector for the transport of Noctiluca
offshore into a cool, oceanic environment not generally associated
with this organism. Noctiluca is thought to be a neritic
species with oceanic occurrences uncommon.
Noctiluca cells found in this study appeared 'healthy'
and 'well-fed', seemingly full of mainly diatom prey. This
indicates that despite their apparent unplanned venture into the
oceanic environment they were able to feed on Southern Ocean
productivity. Data from the same CPR transect showed that copepod
abundance was apparently limited by the presence of the
Noctiluca indicating potential competition for food. If
viable populations of Noctiluca become established in
the Southern Ocean in the future, there is likely to be additional
competition for phytoplankton with copepod grazers, with unknown
effects for the food web. Given predictions that the EAC is likely
to continue to strengthen and transport more warm water and eddies
further south there may be more frequent seeding of
Noctiluca into cooler waters in the future and
Noctiluca could well become resident in the Southern
Ocean.
The results of this finding have recently been published online in
the Journal of Plankton Research and can be found
at http://plankt.oxfordjournals.org/content/early/2012/02/01/plankt.fbr112.short?rss=1
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Apparent range extension of Noctiluca scintillans in
the Australian region, comparing distribution records in 1860-1950,
1980-1993 (expansion of blooms in Sydney region), 1994-2005 (range
extension into Tasmania), 2008 (first reports in Queensland,
Western Australia and South Australia) and 2010 (first report in
the Southern Ocean south of Tasmania). The legend shows number of
cells per 5 nautical mile segment. Grey circles represent records
of Noctiluca from AusCPR samples collected between
Melbourne and Adelaide in 2010 (data from www.imos.org.au/emii). Maps are reproduced from
Hallegraeff et al. (Hallegraeff et al., 2008).
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Chl a, sea surface temperature (°C), Noctiluca
scintillans abundance and total copepod abundance along a CPR
transect conducted south of Tasmania in December 2010.
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