JPR Advance Access originally published online on August 20, 2004
Journal of Plankton Research 2004 26(12):1429-1439; doi:10.1093/plankt/fbh131
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Journal of Plankton Research Vol. 26 No. 12 © Oxford University Press 2004; all rights reserved
Seasonal variations of bacterial abundance and biomass and their relation to phytoplankton in the hypertrophic tropical lagoon Ciénaga Grande de Santa Marta, Colombia
1 Leibniz-Institut für Meereswissenschaften an der Universität Kiel (IFM-GEOMAR), Düsternbrooker WEG 20, D-24105 Kiel, Germany and 2 Instituto de Investigaciones Marinas y Costeras (INVEMAR), APTO Aereo 10016, Santa Marta, Colombia
* Corresponding Author: kgocke{at}ifm-geomar.de
Received April 16, 2004; accepted in principle June 2, 2004; accepted for publication July 27, 2004; published online August 20, 2004
The seasonal development of bacteria was studied in the hypertrophic coastal lagoon Ciénaga Grande de Santa Marta (Caribbean coast of Colombia). This large but only 1.5 m deep lagoon is subject to strong seasonal variations of salinity from almost fully marine (April/May) to brackish conditions in October/November. Chlorophyll ranged from 6 to 182 µg L–1, and gross primary production amounted to 1690 g C m–2 per year. Total bacterial number (TBN) ranged from 6.5 to 90.5 x 109 cells L–1 and bacterial biomass (BBM) from 77 to 1542 µg C L–1, which are among the highest ever reported for natural coastal waters. Neither TBN nor BBM varied significantly with salinity, phytoplankton or seston concentrations. Only the bacterial mean cell volume showed a significant relation to salinity, being highest (0.066 µm3) during the period of increasing and lowest (0.032 µm3) during decreasing salinity. Bacterial protein accounted for 24% (19–26%) and phytoplankton protein for 57% (53–71%) of total seston protein. The ratio (annual mean) of bacterial carbon to phytoplankton carbon was 0.44 (range 0.04–1.43). At low phytoplankton abundance [chlorophyll a (Chl a) < 25 µg L–1], bacterial carbon was almost equal to phytoplankton biomass (i.e. the mean ratio was 1.04). In contrast, at Chl a > 100 µg L–1, BBM was low compared to phytoplankton biomass (the mean ratio was 0.16). In general, BBM varied less than phytoplankton biomass. Most probably, the missing correlation between bacterial and phytoplankton variables was due to (i) organic material partly derived from allochthonous sources serving as food resource for bacteria and (ii) a strong resuspension of bacteria from the sediment caused by frequent wind-induced mixing of the very shallow lagoon.