Summary of Abstract Submission

Abstract Submission No. IO50-09-0058PresentationPoster

THE GRAZING IMPACT OF NOCTILUCA AND COPEPODS ON THE PHYTOPLANKTON COMMUNITY IN THE NUTRIENT ENRICHED MUD BANK WATERS OFF ALAPPUZHA, SOUTHWEST COAST OF INDIA.

Arunpandi. N*1, Jyothibabu. R1, Jagadeesan. L1, Madhu, N.V. 1, Karnan. C1

1 CSIR-National Institute of Oceanography, India

ABSTRACT :

Recent literature indicates the possible role of Noctiluca, an organism earlier considered as an autotroph, in controlling the phytoplankton community in nutrient-enriched conditions. Oceanographic observations in the past have records of abundant Noctiluca population along the west coast of India during the peak/late Southwest Monsoon (SWM). Here, we present the results of a pilot experimental study carried out to understand the grazing impact of Noctiluca and an omnivore copepod assemblage on the phytoplankton community inhabiting the nutrient-enriched mudbank waters off Alappuzha, on the south-west coast of India. The experimental samples were collected during mid-July 2014 as the part of a CSIR NIO field sampling exercise to study the mudbank process. The phytoplankton biomass (chlorophyll a) in the experimental water sample was exceptional (10.17 mg.m-3) due to the large abundance of Fragilaria and Coscinodiscus. Grazing of Noctiluca and copepods were measured using food removal experimental setups for different size fractions of phytoplankton. The phytoplankton and grazer abundance in the experiment was maintained roughly similar to the natural levels. The grazing of Noctiluca and copepods were found to be 45.56 2.14 % and 23.57 1.42 % of the total phytoplankton biomass production in the experimental setup. Noctiluca showed higher food preference for larger phytoplankton (>20m), whereas copepods preferred nano-phytoplankton cells (2 - 20m). The study points the dominant role of Noctiluca as a grazer of large phytoplankton community along the west coast of India during peak/late SWM.