Effects of Copepod Grazing on Two Natural Phytoplankton Populations
01 Aug 1970-Wsq: Women's Studies Quarterly (NRC Research Press Ottawa, Canada)-Vol. 27, Iss: 8, pp 1395-1403
TL;DR: A comparison of estimates of mean summer primary production at the depths of maximum photosynthesis and daily zooplankton food intake suggested that, at those depths, zoopLankton in Bras d'Or Lake consumed all the average daily production whereas 66% was removed in Morrison's Pond.
Abstract: Feeding and filtration rates of four species of copepods (Pseudocalanus minutus, Temora longicornis, Oithona similis, and Acartia tonsa) from Bras d'Or Lake and Morrison's Pond, Cape Breton Island,...
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TL;DR: It is proposed that future research might profitably be directed toward the question of how the pelagic environment selects for life histories and morphologies of organisms under conditions when resource availability and predation are both significant structural buttresses.
Abstract: This paper explores the notion that the theoretical basis for contemporary research concerning the structure and function of marine pelagic ecosystems is self-limiting. While some findings such as the microbial food web have extended our knowledge of the biological components of the upper water column and their relationships to fluxes of materials and energy, they have not advanced our understanding of why specific pelagic forms occur in time and space, and why only some attain dominant status and contribute the bulk of biogenic fluxes emanating from the mixed layer. It is argued here that a major impediment to improved conceptual models is the historic focus on resource-driven or 'bottom-up' factors as being the dominant variables structuring planktonic ecosystems. Evidence is presented that predation or 'top-down' trophic effects may be equally important in specifying the occurrence of particular taxa, the biomass within adjacent trophic levels, and the morphology of dominant herbivores and carnivores. It is suggested that key species, because of unique combinations of life history strategies, metabolic demands, and physiological performance, may exert a dominant role in the extent to which predatory interactions cascade through pelagic food webs. There is considerable evidence of evolution of predation avoidance strategies among phytoplankton and zooplankton. It is proposed that future research might profitably be directed toward the question of how the pelagic environment selects for life histories and morphologies of organisms under conditions when resource availability and predation are both significant structural buttresses. Methodological approaches should include detailed studies of dominant key taxa from different environments, with the goal of identifying the critical aspects of life history, behavior, or morphology which account for their success.
640 citations
TL;DR: The notion that the relationshp between feeding and production in copepods is driven by clletary diversity is derived in part from a recent recognition of the diversity of microplanktonic organisms that potentially or actually contribute to the diet.
Abstract: A review of the literature (ca 1900 to 1992) on copepod feeding indicates that combinations of stochashc and deterministic processes result in behaviors, or feeding strategies, that optirnize nutritional gain from the food environment, and further, that strategies change in response to environmental variability. Because the diet is the product of a feeding strategy, one may gain insight into the ways in which copepods respond to their food environments by measuring their diets. Investigations of the hnks between copepod feeding and production suggest that dietary diversity is often a key to the procurement of a nutritionally complete ration, and the optimization of secondary production within constraints dictated by the physical environment. The ability to eat different kinds of foods (ornnivory) and the tendency to include a variety of foods in the daily ration may enhance the probabhty of obtaining a nutritionally complete ration in variable, nutritionally dilute, food environments. The notion that the relationshp between feeding and production in copepods is driven by clletary diversity is derived in part from a recent recognition of the diversity of microplanktonic organisms that potentially or actually contribute to the diet. Further, the concept is consistent with current trophic dynamic models in which food webs are envisioned as complex interwoven systems rather than short, simple chains.
545 citations
Cites background from "Effects of Copepod Grazing on Two N..."
...…with particle concentration, the initial slope of the relationship being affected by particle size or biomass (Mullin 1963, Parsons et al. 1967, Hargrave & Geen 1970, Frost 1972, 1977, Nival & Nival 1973, 1976, Mullln et al. 1975, Reeve & Walter 1977, Bartram 1980, Poulet & Marsot 1980, but…...
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TL;DR: These mechanisms are enumerated and awareness of these mechanisms and their interrelationships will provide insights for those investigating the efficiency of various modes of filter feeding and the mechanisms of size-selective suspension feeding.
Abstract: We enumerate the five basic mechanisms by which any biological or manmade filter can remove particles from a fluid. These mechanisms are: (1) direct interception, (2) inertial impaction, (3) gravitational deposition, (4) motile-particle deposition, and (5) electrostatic attraction. For these mechanisms we present dimensionless indexes that indicate which measurable characteristics of the filter, the particles, and the flow affect the intensity of particle capture. By comparing the magnitudes of these indexes it is possible to determine the main mechanism a filter is using to capture particles. Awareness of these mechanisms and their interrelationships will provide insights for those investigating the efficiency of various modes of filter feeding and the mechanisms of size-selective suspension feeding.
472 citations
01 Jan 1989
TL;DR: In addition, the influence of zooplankton on algal succession is not limited to their selective effect on the algal numbers, but also indirectly with phytoplankon by making some nutrients more available to them as discussed by the authors.
Abstract: At times, freshwater zooplankton consume phytoplankton populations at rates similar to or faster than that at which they are growing (Hargrave and Geen, 1970; Gulati, 1975; Horn, 1981; Persson, 1985; Borsheim and Anderson, 1987). Such high losses certainly must help direct seasonal succession as they force a subset of algal species to suffer high mortality rates. Some studies have concluded that losses in general (Kalff and Knoechel, 1978; Reynolds, et al., 1982) and grazing losses in particular (Porter, 1973, 1976, 1977; Lynch and Shapiro, 1981; Crumpton and Wetzel, 1982; Kerfoot, 1987) are important in seasonal succession. In addition, the influence of zooplankton on algal succession is not limited to their selective effect on algal numbers. Zooplankton also interact indirectly with phytoplankton by making some nutrients more available to them (Gliwicz, 1975; Lehman, 1980a, b; Redfield, 1980; Lehman and Scavia, 1982; Sterner, 1986a). Zooplankton thus act not only as predators in the classic sense, but they also have an effect on the competition among algae (Elser et al., 1988).
387 citations
TL;DR: Multiple regression analysis of published zooplankton filtering and feeding rates yielded separate regression equations for cladocerans, marine Calanoid copepods, and all zoopLankton, which suggest possible mechanisms of feeding limitation and provide a heuristic framework for the design of experimental analyses of zoopalankton feeding in marine and freshwater systems.
Abstract: Multiple regression analysis of published zooplankton filtering and feeding rates yielded separate regression equations for cladocerans, marine Calanoid copepods, and all zooplankton. Ingestion rate was found to increase significantly with animal size, food concentration, and temperature. Filtering rate also increased with animal size and temperature, but declined as food concentration increased. The analysis suggests a difference in particle size preference between cladocerans and copepods. Experimental conditions such as crowding and duration also significantly affected filtering and feeding rates. The regression models allow examination of differences and similarities among zooplankton taxa, functional response, particle size selection, energy allocation, and threshold food concentration. The statistical models describe suspension feeding more precisely than either average literature values or verbal descriptions of trend. The results also suggest possible mechanisms of feeding limitation and provide a heuristic framework for the design of experimental analyses of zooplankton feeding in marine and freshwater systems.
362 citations
References
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TL;DR: The view that the feeding activity of Calanus is automatic filtering is favored by these experiments, and approximately one-half the organic nitrogen content of Nitzschia is in a form available to Calanus.
Abstract: (1) The filtering rate of Calanus finmarchicus on the diatom, Nitzschia closterium, was measured under different conditions of diatom concentration, light and temperature, by observing the reduction in concentration of the diatoms. Change in diatom concentration had no effect on the rate of filtration. There was some evidence of a diurnal feeding rhythm with greater activity at night. Feeding was most rapid at 8° C., slower at 13° and 3°.(2) Studies on the growth of Calanus supplied with different concentrations of diatoms indicated that the food requirement is less than has been calculated from oxygen consumption measurements. This is also borne out by comparing the amount of particulate organic matter in the sea with the rate of feeding measured in the laboratory.(3) The view that the feeding activity of Calanus is automatic filtering is favored by these experiments.(4) Approximately one-half the organic nitrogen content of Nitzschia is in a form available to Calanus.(5) These results are correlated wit...
72 citations