Protozoa associated with leaf litter degradation in Coringa mangrove forest, Kakinada Bay, east coast of India

Abstract

Observations (1995-’96) on mangrove leaf litter revealed a variety of microorganisms dominated by bacteria (5 types), 12 species of flagellates, 2 sarcodines, 17 ciliates, 2 suctorids and 2 sessile ciliates besides several diatoms, nematodes and nauplii. Overall, bacteria outnumbered (4.59 x 10⁵ no. g^-1 dry weight) all others constituting 80-90% of the population followed by flagellates (4.8%), ciliates (4.4%) and, sessile ciliates (0.2%). <i>Chromulina</i> sp., <i>Spumella socialis</i> and <i>Euglena acus</i> (flagellates), <i>Cyclidium</i> sp., <i>Prorodon</i> sp., <i>Euplotoides aediculatus</i> and <i>Zoothamnium</i> sp. (ciliates) were relatively dominant (mean density 4,331 individuals l^–1) in the litter collected from <i>Avicennia</i> plot. Flagellates, <i>Astasia</i> sp., <i>Heteronema</i> sp. and<i> Paranema</i> sp. and, ciliates, <i>Prorodon </i>sp<i>., Holosticha </i>sp. and<i> E. aediculatus</i> were, however, more common in <i>Excoecaria </i>(mean density 3719 individuals l^–1). <i>In situ </i>experiments on leaf decay showed that the entire process lasted 12-18 days in summer and 26-32 days during monsoon. Bacteria were the first to settle, followed by nanoflagellates (2-20 <img src='/image/spc_char/micro.gif'>m), microciliates (20-100 <img src='/image/spc_char/micro.gif'>m), macrociliates (100-200 <img src='/image/spc_char/micro.gif'>m) and sessile ciliates. Nematodes indicated culmination. Bacterial (mean) biomass registered highest value (6.43x10^-3 mgC g^-1) within 24 hours but decreased (3.1x10^-6 mgC g^-1)by day-3 to 5. Mean flagellate biomass peaked (32.6 mgC g^-1) by day-2 and microciliates (92 mgC g^-1) by day-5 in summer and (47mgC g^-1) by day-24 during monsoon. Macrociliates registered highest biomass (168.4mgC g ^–1) by day-6 in summer but lagged behind until day-26 to day-30 (154mgC g ^–1) during monsoon. A distinct prey predator relationship, direct dependence of ciliate species on nanoflagellate and bacterial populations as well as, a well marked microbial community succession were evident.