Lake Kinneret: A seasonal mode1 for carbon flux through the planktonic biota

Abstract

Carbon standing stock distribution in the cuphotic zone of Lake Kinneret and the immediate fate of primary-produced carbon arc very different during late winter-early spring (with the occurrence of the annual dinollagellate bloom) than they are in late summer (when nanophytoplankton are the dominant primary producers). We used a linear programming model to construct balanced carbon flow charts for these two seasons based on measured primary productivity; on carbon standing stocks of algae, bacteria, flagellates, ciliates, cladocerans, rotifers, and fish; and on data on turnover times, respiration, and grazing rates obtained in 1989. The charts were compiled to fit as closely as possible all obscrvcd and inferred estimates of carbon fluxes while simultaneously ensuring that mass balance and key biological constraints were maintained for each of the 10 compartments representing the principal biota of the Kinneret food web. We used the model to examine the extent to which individual intercompartmental flux rates were free to vary while the mass-balance and biological constraints were enforced. The model was also capable of generating different yet feasible flow-chart scenarios; it thus proved useful in suggesting alternative hypotheses concerning the role of the microbial food web in the euphotic waters of Lake Kinneret.A major aim of both theoretical and applied aquatic research has long been to understand the patterns of flow of carbon and other elcments through the pelagic biota in lakes and seas. Within the last decade it has become increasingly evident that the complex communities of microbial organisms in the pelagic zone in both marine and freshwater environments play a key role in processing and transferring carbon, nitrogen, and phosphorus from primary producers to metazoan plankton and fish (Pomeroy 1974;Azam et al. 1983; Berman 1990). Much debate has been generated concerning the function of microbial food webs as Acknowledgments WC are indebted to B. Azoulai, K. D. Hambright, M. Gophen, G. Nahum, 0. Hadas, U. Pollinghcr, Y. 2. Yacobi, and T. Zohary for data, discussion, and dissent. We are grateful for the comments of two rcvicwcrs that enabled us to improve and revise the original version of the paper.

Gross growth efficiencies of protozoan and metazoan zooplankton and their dependence on food concentration, predator‐prey weight ratio, and taxonomic group

“…This generalization has been (possibly uncritically) applied by, among others, Fasham (1985) using a protozoan GGE of 40% vs. a metazoan GGE of 15%; Vkzina and Platt (1988) lo-60 vs. O-40%; Weisse et al (1990), 40 vs. 25%; Nielsen and Kiorboe (1991), 40 vs. 33%; Leakey et al (1992), 40 vs. 25%; Lignell et al (1993), 40-50 vs. 25%; Nielsen et al (1993), 40 vs. 33%; and Stone et al (1993), 40-50 vs. 20%. The assumed taxon specificity is the only generalization on GGE of planktonic organisms used in these models.…”

Trophic Structure and Carbon Flow Dynamics in the Pelagic Community of a Large Lake

“…A number of investigations on carbon (e) cycling in pelagic ecosystems focused on the role of the microbialloop (e.g., Ducklow et al (1986), Jackson and Eldridge (1992), and Stone et al (1993». The present case study from large and deep Lake Constance aims to contribute to this partially controversial issue by evaluating separately the contribution of the microbial community to the nutrition of large zooplankton (i.e., the link-sink issue), and to the overall C flow dynamics. This is done by aggregating all species from the entire food web into two separate chains, one based directly on phytoplankton (calIed grazing chain in the following), and one relying energetically on dead organic maUer taken up by osmotrophic bacteria (detritus chain).…”

Examination of the role of the microbial loop in regulating lake nutrient stoichiometry and phytoplankton dynamics

“…The latter refers to the dynamics of the heterotrophic bacteria and the microzooplankton grazers (defined here as size less than 125 µm that account for rotifers, ciliates and juvenile macrograzers; Thatcher et al, 1993) -often termed the "microbial loop". This has been shown to play an important role in shaping carbon fluxes in lakes and in enhancing nutrient cycling at the base of food webs (Gaedke et al, 2002), including in Lake Kinneret which is the focus in this study (Stone et al, 1993;Hart et al, 2000;Hambright et al, 2007;Berman et al, 2010).…”

“…It is well established that microzooplankton can transfer energy and nutrients via bacterial grazing to higher trophic levels due to their small size and high mass-specific grazing rates (Hart et al, 2000;Loladze et al, 2000), thereby playing an important role in carbon and nutrient recycling (Stone et al, 1993;Dolan, 1997;Hambright et al, 2007). In turn, larger zooplankton grazing on microzooplankton further provide organic matter for bacterial growth through excretion of nutrient rich organic compounds (DOM) and fecal pellet production (POM) (Peduzzi and Herndl, 1992).…”

“…Initially, a steady-state C flux model was developed to examine C cycling through the planktonic biota, including consideration of the microbial loop (Stone et al, 1993;Hart et al, 2000). A one-dimensional (1-D) coupled hydrodynamic-ecosystem model (DYRESM-CAEDYM) was presented by Bruce et al (2006), which focused specifically on the zooplankton dynamics and their contribution to nutrient recycling.…”