IR Home
MEPS
Home
Editors
Forthcoming
Information
Subscribe
Journals
Home
MEPS
AME
CR
DAO
ESEP
Search
Subscribe
Book Series
EE Books
Top Books
ESEP Books
Order
EEIU Brochures
(pdf format)
Discussion Forums
Home
Research
Endangered Species Programs
Institutions
International Ecology Institute
Eco-Ethics International Union
Foundation
Otto Kinne Foundation
 | |
MEPS 239:57-68 (2002)
|
Abstract
|
Top-down regulation in ctenophore-copepod- ciliate-diatom-phytoflagellate communities in coastal waters: a mesocosm study
Edna Granéli1,*, Jefferson T. Turner2
1Department of Marine Sciences, University of Kalmar, 39182 Kalmar, Sweden
2Biology Department and School for Marine Science and Technology, University of Massachusetts, Dartmouth, North Dartmouth, Massachusetts 02747, USA
*E-mail: edna.graneli@hik.se
ABSTRACT: Interactions between the ctenophore Pleurobrachia pileus, copepods, ciliates and phytoplankton in a late spring natural plankton community were studied experimentally using mesocosms consisting of 300 l polyethene cylinders. Mesocosms
were filled with 90 µm filtered nutrient-enriched seawater from Gullmar Fjord on the Swedish Skagerrak coast. Mesozooplankton (primarily copepods and marine cladocerans) or ctenophores were added, either alone or in combination, to examine top-down
predation and grazing effects on phytoplankton abundance and composition. Predation impact of ctenophores on copepods appeared to be minimal in that it did not significantly decrease the biomass of the copepods until the last day of the experiment.
However, in the presence of ctenophores, ciliates increased compared to controls both with and without added zooplankton, suggesting that ctenophore predation on copepods reduced copepod predation on ciliates. In the absence of ctenophores, ciliates
declined precipitously, presumably due to copepod predation. This was particularly severe in treatments with zooplankton added at 10x the natural abundance but without ctenophores. Copepods heavily grazed on the diatom Skeletonema costatum, and
most phytoflagellates increased in mesocosms with copepod additions, suggesting that they were not substantially grazed by copepods. However, copepods did graze to some extent on larger dinoflagellates of the genus Gymnodinium/Karenia.
Ciliates were important phytoplankton grazers, especially of phytoflagellates and picoplankton. It appears that the primary top-down effect of ctenophore predation on copepods was to reduce copepod predation on ciliates, thereby increasing ciliate grazing
on the small flagellates that dominated the phytoplankton.
KEY WORDS: Ctenophore · Copepod · Ciliate · Diatom · Flagellate · Predation · Marine ecosystem · Mesocosm
Full text in pdf format
Published in MEPS Vol.
239
(2002) on August 23
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2002
|
