), respectively, from winter to spring. In addition, the bacterial secondary production to primary production (BSP:PP) ratio decreased from 3.7 to 0.2 in Reloncaví Fjord, suggesting a transition from microbial to classical pelagic food webs. The higher solar radiation and extended photoperiod of springtime promoted the growth of diatoms in a nutrient-replete water column. Allochthonous (river discharge) and autochthonous (phytoplankton exudates) organic matter maintained high year-round bacteria biomass and secondary production. In spring, grazing pressure from zooplankton on the microplankton (largely diatoms) resulted in the relative dominance of the classical food web, with increased export production of zooplankton faecal pellets and ungrazed diatoms. Conversely, in winter, zooplankton grazing, mainly on nanoplankton, resulted in a relative dominance of the microbial loop with lower export production than found in spring. Carbon fluxes and fjord-system functioning are highly variable on a seasonal basis, and both the multivorous trophic webs and the carbon export were more uncoupled from local PP than coastal areas.
Arzul, G., Seguel, M., and Clément, A. 2001. Effect of marine animal excretions on differential growth of phytoplankton species. -ICES Journal of Marine Science, 58: 386-390.Five phytoplankton species were cultivated in the presence of different marine animal excretions, and growth rates were compared. Growth of Chaetoceros gracilis was stimulated by excretion from the oyster (Crassostrea gigas) and inhibited by excretion from the sea bass (Dicentrarchus labrax). Growth of Heterosigma akashiwo was stimulated by excreta from the mussel (Mytilus chilensis) inhibited by excreta from sea bass and salmon (Salmo salar), and unaffected by oyster excretions. Growth of Gymnodinium mikimotoi was also inhibited by excreta from sea bass and unaffected by oyster excreta. Growth of Alexandrium catenella and A. minutum was not affected by animal excreta under our experimental conditions. The results indicate that the organic components of dissolved excreta were responsible for the observed effects: stimulators when excreted by shellfish, and inhibitors when excreted by finfish.
International Council for the Exploration of the Sea
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.