Title: Marine Environmental Chemistry
1Diversity and succession of marine
dinoflagellates over eight years from a
Portuguese upwelling systemDodge J.a, Icely J.
b,c, Legrand.C.d, Newton A.b
(alicely_at_mail.telepac.pt)
1. BACKGROUND METHODS
- Dinoflagellate succession was observed over
eight years (1994 2001) at Sagres, SW Portugal
(Fig.1). - An offshore long-line system for bivalve
aquaculture was selected for the sampling site
(white rectangle - in image of Cape St Vincent, Fig.1).
- 266 samples were collected by a 5 minute haul
with a 54 micron mesh plankton net, approximately
weekly - during the summer, and fortnightly during
the winter over the eight year period. - Samples were preserved with 5 formaldehyde
and examined by phase contrast and light
microcscopy. - Wherever possible a minumum of 200 cells were
identified to give species-frequency data. - The data is currently being analysed
statisticaly with PRIMER software package and
compared to other - environmental parameters, when they have been
measured over the eight years.
2. OBSERVATIONS
- 48 genera and 204 species of Dinophyceae were
identifieded over the eight year period. - The 42 species listed in Figure 2 were observed
in over fifty of the samples. The number of
samples - for each species are shown in brackets.
- There was no consistent pattern in the
succession of species from year to year. - However, it is probable that these patterns
will be clarified by relating the succession to
the wind and - temperature conditions along the
South-Western Iberian coast. - Figure 3 shows the typical wind (a) and
temperature (b) conditions along the Sagres
coast during - the summer (May September). Rapid reductions
in temperature (red arrows in Fig.b) reflect the - upwelling conditions induced by the prevailing
northerly winds (coloured vectors in 3a),
3 b
3 b
3. HARMFUL ALGAL BLOOMS (HAB)
- Algal blooms produced by some species of
dinoflagellates have important - consequences for the management of bivalve
aquaculture. - Principle Components Analysis (PCA in Fig. 4)
indicates that most of the species (see - list in Fig 4), with the potential to produce
toxins, occur during the summer (below the - line in Fig.4) or during the autumn ( above
the line in Fig.4). Statistical analysis also - shows an increase in HAB species in the latter
years of the study.
5. CONCLUSIONS
- The diversity of dinoflagellates at this one
site in Portugal is - striking. In a review of all the records for
Portuguese phyto- - plankton, Moita and Vilarinho (1999) recorded
67 genera and - 233 species of Dinophyceae from the south and
the south-west - of Portugal. However 70 species in this
current study are not - in this list
- The initial statistical analysis of this data
shows that there has - been an increase in the frequency of potential
HAB species - between 1994-2001.
N. scintillans
ACKNOWLEDGEMENTS This project was partially
funded by FCT project nº FCT-PRAXIS-MAR
1696-95. We also thank the aquaculture companies
Videsa, Aquasagres, and Ostracultura who have
encouraged and assisted with the sampling
programme.
REFERENCE Moita, M.T. and Vilarinho, M.G. 1999.
List of phytoplankton species in
Portugal seventy years of studies. Portugaliae
Acta Biológica, ser B-18
Mini-symposium Standards for the survey of and
analysis of plankton. SCOR working group 115.
Plymouth, UK, 19-20 May 2006