Seasonal variation in the plankton of Porto Novo Waters (India)

Summary

The seasonal variations of marine (collected at the ten fathom line-Station A) and estuarine (collected at the Mouth of the Vellar estuary-Station I) plankton of Porto Novo (India) are described, covering the period 1960–63. The biological, temporal and numerical variations of phytoplankton and zooplankton are described for the two stations. The succession of species was more or less similar at both stations, but certain forms like colonial Radiolaria, Scyphomedusae, Anthozoa, trochophore of Sipunculids, Stomatopod larvae and Protochordate larvae were relatively more confined to Station A, and crustacean larvae other than Stomatopods Actinotrocha larva, fish eggs and larvae were relatively more confined to Station I.

The Diatom main peak was about June–July at Station A and about May–July at Station I. The Diatom peak was generally heralded with the appearance of Coscinodiscus. Noticluca usually showed three spurts- mainly two distict ones about May–June and August. The third development was only during certain years and not so intensive. Copepods showed two peaks generally during June–July after few days of the Diatom bloom, and during October–November following the first monsoon rains.

The peaks of Diatoms, Peridinians, Noctiluca, Molluscan larvae and Tunicate larvae were more marked at Station A than at Station I. A rich and varied zooplankton was observed about February at Station A. The appearance of salps at Station A seems in a way to be related to salinity, when the salinity values were between 28.89–34.55‰, the salps appearing more with a fall in salinity. Similarly at Station I, Creseis acicula, Prawn larvae and fish larvae seem to be associated with a sudden fall in temperature and salinity when the monsoon rains start, at Station I.

The numerical relationship of plankton at Station A was generally inverse between phyto- and zooplankton and this was generally parallel at Station I.

Sumario

La variación estacional del plancton marino (collectado en la ‘ten fathom line’estacción A) y estuarino (Mouth of the Vellar estuary) és descrita para el período 1960–63. Las variaciones biológicas, temporales y numéricas del fitoplancton y del zooplancton son descritas para las dos estacciones. La succesión de especies fué más o menos comparable en las dos estacciones; algunas formas como colonial radiolaria, scyphomedusae, anthozoa, trochophore y sipunculids, stomatopod larvae, y protochordate larvae fuéron confinadas a la estacción A, y otras como crustacean larvae, Actinotrocha larva, peces ‘eggs y larvae’ confinades a la estacción I.

El maximum para las diatomeas ocurrió en Junio–Julio en la estacción A,y Mayo–Junio en la estación I. Las diatomeas están representadas principalmente por el génere Coscinodiscus antes del maximum. El maximum para Noctiluca fue observado en Mayo–Junio y en Agosto. Los copepodes presentaran dos períodos de maximum Junio–Julio despues del maximum de las diatomeas y en Octubre–Noviembre. El maximum de las diatomeas, peridianians, Noctiluca, molluscan larvae y tunicate larvae en la estacción A fué mas distincto que en la estacción en el estuario. El zooplancton se mostró rico y variado en Febrero en la estacción A.

La presencia de salpas en la estacción A parace ser relacionada en ciertos aspectos con la diminuición de la salinidad cuando esta fué 28.89–34.55‰. Por la misma forma la presencia de Creseis acicula, prawn larvae, peces ‘eggs y larvae’ parace ser relacionada con diminuición de salinidad y temperatura del agua durante Octobre–Noviembre–Deciembre en la estacción I. Las relaciones numéricas del plancton indican que en la estacción A fueran contrarias y en la estacción I paralelas.