Etude des migrations nycthemerales du zooplancton dans un milieu marin peu profond
✍ Scribed by M. H. Daro
- Publisher
- Springer
- Year
- 1974
- Tongue
- English
- Weight
- 456 KB
- Volume
- 44
- Category
- Article
- ISSN
- 1573-5141
No coin nor oath required. For personal study only.
✦ Synopsis
The sluice-dock of Ostend, a shallow (1,5 m) marine biotope of 86 ha stays closed during some 6-7 months of the year and is not influenced by the tides .
During 24 h cycles the nycthemaral migrations of the zooplankton at 5 depths in a watercolumn of 1 meter were studied in relation to several environmental factors : water temperature, dissolved oxygen, pH and chlorophyl content .
The photosynthesis shows a minimum during the night and shows a maximum during the late afternoon, at which time the water-temperature is also maximal .
Holo-and meroplanktonic organisms migrate towards the surface around 3-5 o'clock a .m ., at which time the chlorophyl content is minimal, hence our hypothesis of nocturnal grazing, this phenomenon perhaps combined with a nocturnal division of phytoplankton cells .
Each observed species has its own characteristic behaviour in relation to its negative diurnal phototropism and its own diurnal bottomward migration speed .
A . INTRODUCTION
Les migrations verticales du zooplancton ont ete etudiees depuis longtemps et sont choses connues . BAINBRIDGE (1961) decrit le phenomene comme suit : une ascension se manifeste dans la fin de l'apres-midi ; elle est dirigee vers une source de lumiere d'intensite faiblissante . Ceci se continue toute la nuit durant. BORGOROV (1958) pense meme que les 3/4 du zooplancton effectuent des migrations journalieres . On distingue differentes migrations verticales du zooplancton .
Le zooplancton qui migre journellement et peut effectuer des distances de 2 a 600 m .