title: Bloom-forming cyanobacteria support copepod reproduction and development in the Baltic Sea.
abstract: It is commonly accepted that summer cyanobacterial blooms cannot be efficiently utilized by grazers due to low nutritional quality and production of toxins; however the evidence for such effects in situ is often contradictory. Using field and experimental observations on Baltic copepods and bloom-forming diazotrophic filamentous cyanobacteria, we show that cyanobacteria may in fact support zooplankton production during summer. To highlight this side of zooplankton-cyanobacteria interactions, we conducted: (1) a field survey investigating linkages between cyanobacteria, reproduction and growth indices in the copepod Acartia tonsa; (2) an experiment testing relationships between ingestion of the cyanobacterium Nodularia spumigena (measured by molecular diet analysis) and organismal responses (oxidative balance, reproduction and development) in the copepod A. bifilosa; and (3) an analysis of long term (1999-2009) data testing relationships between cyanobacteria and growth indices in nauplii of the copepods, Acartia spp. and Eurytemora affinis, in a coastal area of the northern Baltic proper. In the field survey, N. spumigena had positive effects on copepod egg production and egg viability, effectively increasing their viable egg production. By contrast, Aphanizomenon sp. showed a negative relationship with egg viability yet no significant effect on the viable egg production. In the experiment, ingestion of N. spumigena mixed with green algae Brachiomonas submarina had significant positive effects on copepod oxidative balance, egg viability and development of early nauplial stages, whereas egg production was negatively affected. Finally, the long term data analysis identified cyanobacteria as a significant positive predictor for the nauplial growth in Acartia spp. and E. affinis. Taken together, these results suggest that bloom forming diazotrophic cyanobacteria contribute to feeding and reproduction of zooplankton during summer and create a favorable growth environment for the copepod nauplii.
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Hedvig
authors.initials: H
authors.lastname: Hogfors
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Nisha H
authors.initials: NH
authors.lastname: Motwani
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Susanna
authors.initials: S
authors.lastname: Hajdu
authors.affiliation: IMDEA Agua, Alcalá de Henares, Madrid, Spain.
authors.forename: Rehab
authors.initials: R
authors.lastname: El-Shehawy
authors.affiliation: Calluna AB, Stockholm, Sweden.
authors.forename: Towe
authors.initials: T
authors.lastname: Holmborn
authors.affiliation: ARONIA Coastal Zone Research Team, Novia University of Applied Sciences & Åbo Akademi University, Ekenäs, Finland; Tvärminne Zoological Station, University of Helsinki, Hangö, Finland.
authors.forename: Anu
authors.initials: A
authors.lastname: Vehmaa
authors.affiliation: ARONIA Coastal Zone Research Team, Novia University of Applied Sciences & Åbo Akademi University, Ekenäs, Finland.
authors.forename: Jonna
authors.initials: J
authors.lastname: Engström-Öst
authors.affiliation: ARONIA Coastal Zone Research Team, Novia University of Applied Sciences & Åbo Akademi University, Ekenäs, Finland; Tvärminne Zoological Station, University of Helsinki, Hangö, Finland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Brutemark
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden; Department of Applied Environmental Science, Stockholm University, Stockholm, Sweden.
authors.forename: Elena
authors.initials: E
authors.lastname: Gorokhova
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D033342:Copepoda / Q000254:growth & development / Q000502:physiology*; D000458:Cyanobacteria / Q000502:physiology*; D003625:Data Collection; D005068:Eutrophication; D056084:Genetic Fitness; D007753:Laboratories; D012098:Reproduction; D013997:Time Factors