An invasive herbivorous fish (Siganus rivulatus) influences both benthic and planktonic microbes through defecation and nutrient excretion

Arthur Escalas, Amandine Avouac, Jonathan Belmaker, Thierry Bouvier, Valentin Clédassou, Franck Ferraton, Fabien Rieuvilleneuve, Gil Rilov, Anna Rovirosa Mulet, Daphna Shapiro Goldberg, Sébastien Villéger

Research output: Contribution to journalArticlepeer-review


Direct and indirect impacts by invasive animals on plants and other animals through predation and competition have been evidenced in many ecosystems. For instance, the rabbitfish Siganus rivulatus, originating from the Red Sea, is now the most abundant species in costal habitats of South-Eastern Mediterranean Sea where it overgrazes algae. However, little is known about its impacts on microbes through release of metabolic wastes and feces. We used a mesocosm experiment to test the effect of S. rivulatus on planktonic and benthic microbial communities. Excretion of dissolved nutrients by fish resulted in higher concentrations of dissolved inorganic nitrogen (NH4, NO2/NO3). This increase in availability of N was associated with higher N content in macroalgae, higher biomass of phytoplankton, higher abundance of bacterioplankton and shift in the structure of planktonic bacterial communities. The feces released mostly under the shelters where the fish rest at night, led to significant increases in diversity of sediment bacterial communities and shifts in their structure. The impact of S. rivulatus on planktonic microbes was related to the indirect bottom-up effect induced by excreted dissolved nutrients while its effect on benthic microbes was due to the direct release of both organic matter and microbes present in feces. Overall, this first evidence of the impacts of invasive species on planktonic and benthic microbes highlights that ongoing changes in fish biodiversity could have ecosystem-wide consequences.

Original languageEnglish
Article number156207
JournalScience of the Total Environment
Issue numberPt 3
StatePublished - 10 Sep 2022
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2022 Elsevier B.V.


  • Animals
  • Defecation
  • Ecosystem
  • Fishes
  • Mediterranean Sea
  • Nutrients
  • Plankton


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