Interspecific differences in the effect of fish on marine microbial plankton

Type Article
Date 2019
Language English
Author(s) Villeger Sebastien1, Fouilland Eric1, Argenty Jeremy1, Bouvier Corinne1, Carre Claire1, Bouvier Thierry1
Affiliation(s) 1 : Univ Montpellier, CNRS, MARBEC, Ifremer,IRD, F-34095 Montpellier, France.
Source Aquatic Microbial Ecology (0948-3055) (Inter-research), 2019 , Vol. 82 , N. 3 , P. 289-298
DOI 10.3354/ame01897
Keyword(s) Marine fish, Nutrient excretion, Protozooplankton, Phytoplankton, Bacteria
Abstract

The productivity of most marine ecosystems is limited by the availability of dissolved nitrogen (N) and phosphorus (P). Nutrient recycling is therefore a key process for ecosystem functioning. Fish recycle nutrients through the excretion of ammonia and phosphate and can influence the abundance and community structure of primary producers such as phytoplankton. However, the effect of fish on other plankton compartments, and whether all fish species have similar effects, is largely unknown. We used a tank experiment to test how 2 Mediterranean fish species, gilthead seabream Sparus aurata and golden mullet Chelon auratus, with distinctly different N and P excretion rates, can affect the abundance and community structure of 3 plankton compartments: phytoplankton, bacterioplankton, and microzooplankton. We found that the nutrients released by seabream (whose excreta had an N:P molar ratio greater than the Redfield ratio of 16:1) induced a substantial increase in the abundance of all plankton compartments. In addition, with seabream, the relative abundance of diatoms in the phytoplankton communities increased. However, no significant change was observed with mullet, which had a low excreta N:P molar ratio, suggesting that the growth of microbial plankton was limited by the availability of N. Our results demonstrate that nutrient excretion by fish affects the microbial food web through a species-specific bottom-up effect on the total abundance and community structure of the phytoplankton, bacterioplankton, and microzooplankton communities.

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