During summer 1987, a series of experiments was performed in conjunction with monitoring of in situ plankton dynamics in nutrient-deficient Castle Lake, California. These factorial manipulations of nutrients and zooplankton were designed to separate the direct (grazing mortality) and indirect (stimulation of algal growth by nutrient recycling) effects of grazers on both species-specific phytoplankton dynamics, as well as aggregate properties such as total biomass, productivity, and biomass turnover. Grazing loss rates differed significantly among algal species with the mean grazing loss rate suffered by an algal species a negative function of cell or colony size. Stimulation of division rates in the presence of zooplankton (compared to an unenriched treatment lacking zooplankton) was commonly observed. Nutrient and grazer treatments also had significant impacts on algal biomass (indicated by chlorophyll concentration), productivity (PPR), and PPR/chlorophyll, and significant nutrient-grazer interactions were frequently observed. Species-specific algal responses to grazers were aggregated across the phytoplankton by weighting species-specific parameters by the contribution of each species to total community biomass in order to provide community-wide estimates of the importance of direct and indirect effects on algal dynamics. Finally, linkages between population-level responses and aggregate properties were demonstrated by examining relationships between total phytoplankton biovolume concentration and chlorophyll concentration in various treatments, by comparing community-wide grazing rates estimated from aggregated species-specific grazing rates and from changes in chlorophyll growth rates, and by relating the aggregated degree of species-specific growth stimulation to stimulation of biomass turnover. These results indicate that phytoplankton responses to grazers in Castle Lake reflect a mix of direct and indirect effects that varies considerably both between species and through time during the stratified season.
Ecology publishes articles that report on the basic elements of ecological research. Emphasis is placed on concise, clear articles documenting important ecological phenomena. The journal publishes a broad array of research that includes a rapidly expanding envelope of subject matter, techniques, approaches, and concepts: paleoecology through present-day phenomena; evolutionary, population, physiological, community, and ecosystem ecology, as well as biogeochemistry; inclusive of descriptive, comparative, experimental, mathematical, statistical, and interdisciplinary approaches.
Wiley is a global provider of content and content-enabled workflow solutions in areas of scientific, technical, medical, and scholarly research; professional development; and education. Our core businesses produce scientific, technical, medical, and scholarly journals, reference works, books, database services, and advertising; professional books, subscription products, certification and training services and online applications; and education content and services including integrated online teaching and learning resources for undergraduate and graduate students and lifelong learners. Founded in 1807, John Wiley & Sons, Inc. has been a valued source of information and understanding for more than 200 years, helping people around the world meet their needs and fulfill their aspirations. Wiley has published the works of more than 450 Nobel laureates in all categories: Literature, Economics, Physiology or Medicine, Physics, Chemistry, and Peace. Wiley has partnerships with many of the world’s leading societies and publishes over 1,500 peer-reviewed journals and 1,500+ new books annually in print and online, as well as databases, major reference works and laboratory protocols in STMS subjects. With a growing open access offering, Wiley is committed to the widest possible dissemination of and access to the content we publish and supports all sustainable models of access. Our online platform, Wiley Online Library (wileyonlinelibrary.com) is one of the world’s most extensive multidisciplinary collections of online resources, covering life, health, social and physical sciences, and humanities.
This item is part of a JSTOR Collection.
For terms and use, please refer to our
Ecology
© 1992 Wiley