Effects of toxic cyanobacteria on a plankton assemblage: Community development during decay of Nodularia spumigena

Jonna Engström-Öst*, Marja Koski, Katrin Schmidt, Markku Viitasalo, Sigrún H. Jónasdóttir, Marjaana Kokkonen, Sari Repka, Kaarina Sivonen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We studied the development of the plankton community in an artificially created toxic Nodularia spumigena bloom during a 2 wk enclosure study at the SW coast of Finland in the Baltic Sea. We measured bacterial abundance, dominant phytoplankton groups and ciliates, as well as concentrations of phytoplankton pigments, fatty acids, nodularin, protein and nutrients. A high POC:chl a (<10 μm) ratio (427 ± 185), a decrease in the polyunsaturated:total fatty acid ratio (from 0.4 to 0.2), and a reduction in cyanobacteria filament length indicated decay of N. spumigena during the course of the experiment. Along with cyanobacterial decay, high concentrations of ammonium (last day: 2.7 ± 2.0 μmol l-1), nitrate (0.1 ± 0.01 μmol l-1), and orgamc nutrients were released into the water, whereas chl a and the cyanobacterial pigments, echinenone and zeaxanthin, decreased. Nodularin was found in the mesocosms during the whole experiment. A strong increase in filamentous bacteria was detected by the middle of the experiment, most likely indicating a response to grazing pressure. Two ciliate species, Mesodinium rubrum and Urotricha sp., decreased dramatically during the experiment, probably due to predation by the increasing mesozooplankton community. The ciliate Euplotes sp. flourished in the bags and was best suited to escape predation due to its protecting lorica and its surface affinity. No direct harmful effects of the cyano-bacteria on the microorganisms could be documented. We conclude that these blooms provide a potential food source for the heterotrophic food chain, from bacteria, flagellates and ciliates to crustacean zooplankton, and possibly fish.

Original languageEnglish
Pages (from-to)1-14
Number of pages14
JournalMarine Ecology Progress Series
Volume232
DOIs
Publication statusPublished - 3 May 2002
Externally publishedYes

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Ecology

Keywords

  • Bacteria
  • Ciliates
  • Decay
  • Fatty acids
  • Nodularia spumigena
  • Nodularin

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