Plankton diversity and dynamics in a polluted eutrophic lake, Ranchi
B. Mukherjee*, M. Nivedita and D. Mukherjee
Section of Environmental Biology, P.G. Department
of Zoology, Ranchi
College, Ranchi - 834 008, India
(Received: May 01, 2009; Revised received: October 16, 2009;
Accepted: February 27, 2010)
Abstract: The
species diversity of a cultural eutrophic lake at Ranchi
was studied in relation to external variables (forcing functions) and internal
or state variables. The lake receives daily detergent inputs in the form of
washings of a variety of objects. A model was constructed for the estimation of
detergent inputs from the increase in the phosphate concentration, and from
changes in the concentration of inorganic carbon. Nutrients such as inorganic
carbon, nitrates, phosphates, sulphates were found to
be high in contrast to natural unpolluted systems. The DOM, COD
and BOD were also found to be high suggesting organic pollution of the system
with an organic carbon load of 5.4 m moles l-1. The growth and
development of the plankton constituents was studied in this regime. The
natural planktonic rhythm was found to be modified by
the polluted condition existing in the lake.?
The phytoplankton exhibited four peaks in March, May, August, and
November while, the zooplankton showed three peaks in February, July and October.
The abundance of zooplankton during the annual cycle oscillated with that of
the phytoplankton. There was much more evenness in the zooplankton population
in comparison to the phytoplankton. Analysis of both, the zooplankton as well
as the phytoplankton population was done using the Bray-Curtis dissimilarity
index, importance value index and Shannon-Weaver diversity index. The
importance value index was found to provide a better evaluation of the plankton
community than the diversity index. The phytoplankton population showed no
correlation with nutrient availability as indicated by the
correlation-regression analysis and the planktonic
rhythm was not in tune with normal unpolluted conditions. The lake was
classified as meso-polysaprobic using biological and
chemical indices (Pantle and Buck index:3.5, BOD:60; DOM:9.3 and COD:130).
Key words: Blooms,
Cluster analysis, Eutrophic, Importance value index,
Species diversity, Saprobity, Ranchi lake
PDF of full length paper is available online
Copyright ? 2010 Triveni
Enterprises. All rights reserved. No
part of the Journal can be reproduced in any form without prior
permission. Responsibility regarding the authenticity of the data, and the
acceptability of the conclusions enforced or derived, rest completely with the
author(s).
