repartition spatio-temporelle de zooplancton dans la baie de tulear Sud-ouest de Madagascar)

Abstract

The study of the abundance, time and spatial distribution of Zooplankton and its
importance for the marine environment was carried out in the Bay of Tuléar (Southernwestern
of Madagascar) from January to December 2004.
During this study, 72 samples of sea water are observed and 193 species of
Zooplankton are recorded which are divided into two great groups:
- Microzooplancton which is composed by unicellular (Foraminifera, Acantharia, the
Radiolarian ones and Tintinnida) and
- Macrozooplancton which is composed by multicellular: Scyphozoa, Annélida polycheta,
the Copepod, Mysidacea, Chaétognatha, Appendicularia and of the planktonic larvae.
In the whole bay, the population of zooplankton is dominated especially by the
Copepod, Tintinnida and planktonic larvae with proportions respectively: 33, 31 and 14%
in species and 61%, 20 and 12% in a number. Other groups even if they are presents have
relatively small proportions.
The zooplankton exists in the bay during whole year. However, it is more
abundant and more diversified in hot season (from November to April with an average
density of 2,66 x 105 individuals /l of sea water and 193 species) than in fresh season (from
May to October, average density: 0,973 x 105 individuals/l of sea water and 170 species).
Some species such as Tntinnopsis cylindrica (Tintinnides) and Calanus minor
(Copepod) are observed in the bay during whole year. On the other hand, others like
Tintinnidium neapolitanum (Tintinnides), Isochaeta ovalis (Copepoda) are recorded only
during a hot season.
Concerning the spatial distribution, we could have proved that Zooplankton could
be observed in a sea water closed to the littoral as well as in the lagoon of the great reef of
Tuléar.