Effect of food acclimation on assimilation efficiency of <i>Calanus pacificus</i>1

Landry, Michael R.; Hassett, R. P.; Fagerness, V.; Downs, Jan N.; Lorenzen, Carl J.

doi:10.4319/lo.1984.29.2.0361

Cited by 95 publications

(54 citation statements)

References 2 publications

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“…Conover (1978) reported a mean zooplankton assimilation efficiency of 70 ± 30%, which was based on several hundreds of measurements. However, there is some evidence that copepod assimilation efficiency decreases with food concentration (Gaudy 1974, Landry et al 1984, and that it can be much lower (10 to 20%) than the 70% mean at high food concentrations (Gaudy 1974). Assimilation efficiency decreased with food concentration when copepods fed on the diatom and the autotrophic dinoflagellate, but this was not clear for the other diets, particularly for the flagellate and the scuticociliate (Fig.…”

Section: Defecation Rate Gut Passage Time and Assimilation Efficiencmentioning

confidence: 80%

Coupling of ingestion and defecation as a function of diet in the calanoid copepod Acartia tonsa

Beşiktepe¹,

Dam

2002

Mar. Ecol. Prog. Ser.

157

129

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ABSTRACT:The relationship between the rates of ingestion and defecation of the calanoid copepod Acartia tonsa was examined in laboratory experiments with different diets: the diatom Thalassiosira weissflogii, the autotrophic dinoflagellate Prorocentrum minimum, the heterotrophic dinoflagellate Oxyrrhis sp., the flagellate Dunaliella tertiolecta, and the bacterivorous scuticociliate Uronema sp. Experiments were run typically using between 6 and 8 concentrations ranging from 10 to 1150 µg C l -1. Both diet and food concentration had significant effects on ingestion rate, pellet production rates and pellet volume. Ingestion and pellet production rates increased curvilinearly with food concentration. Copepods achieved the highest pellet production rates, the largest pellets and the shortest estimated gut passage times with the diatom diet. For all diets, gut passage time decreased with food concentration in the range 0 to ca. 250 µg C l -1 , but little thereafter. In addition, for all diets, but most obviously in the case of the diatom, pellet volume increased curvilinearly with food concentration. Maximum pellet volume was achieved at food concentrations ranging from 50 to 150 µg C l -1. The defecation and ingestion rates were best correlated when the copepods fed on the diatom and the autotrophic dinoflagellate. Likewise, a decrease in estimated assimilation efficiency with increasing food concentration was apparent only for these 2 diets. This latter pattern is primarily due to an increase in pellet production rate, instead of pellet volume, relative to ingestion rate at the high food concentrations. We conclude that a diatom diet is the most likely one to result in attributes that enhance zooplankton-mediated export flux: high fecal pellet production rates, large pellet size and relatively low assimilation efficiency.

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Section: Defecation Rate Gut Passage Time and Assimilation Efficiencmentioning

confidence: 80%

Coupling of ingestion and defecation as a function of diet in the calanoid copepod Acartia tonsa

Beşiktepe¹,

Dam

2002

Mar. Ecol. Prog. Ser.

157

129

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“…Selective removal of N relative to OC has been noted in previous feeding studies (e.g. Landry et al 1984;Hassett and Landry 1988) and during early degradation in the water columns and surficial sediments of Dabob Bay and Saanich Inlet (Hedges et al 1988b; Cowie et al 1992).…”

Section: Dietmentioning

confidence: 94%

Digestion and alteration of the biochemical constituents of a diatom (Thalassiosira weisflogii) ingested by an herbivorous zooplankton (Calanus pacificus)

Cowie

Hedges

1996

Limnology & Oceanography

129

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A laboratory experiment was conducted in which 14C-labeled diatoms (Thalassisora weissflogii) were fed to an herbivorous copepod zooplankton (Calanus pacz$cus). Digestion efficiencies, as defined by changes in concentration relative to biogenic silica from the diet to fecal pellets, were calculated for 14C, organic carbon, nitrogen, and chlorophyll-type pigments as well as proteins (as amino acids) and polysaccharides (as aldoses).The majority of organic material ingested (~65% of all components except pigments, 30%) was digested. Digestion efficiencies were similar to reactivity patterns observed in previous studies of the same organisms (total N > organic C > total chlorophyll-type pigments). Polysaccharides and particularly amino acids were clearly important nutrients for copepods. However, together with chlorophyll-type pigments, these biochemicals accounted for only 57% of organic C in the diatom and only 35% in fecal pellets. Although lipids represented some fraction of the uncharacterized materials, an important, relatively stable diatom component remained unidentified and apparently was concentrated in the fecal pellets.Individual amino acids and especially aldoses were digested to differing degrees, apparently due to preferential digestion of intracellular materials with concomitant preservation of cell-wall polymers in the fecal pellets. Overall, egested materials were dramatically altered in composition relative to the diet. Digestion efficiencies for all components were similar in magnitude and pattern to reactivities observed in temperate coastal sites in which diatoms and copepods are important contributors to plankton populations and sinking particle fluxes.Understanding the fate of phytoplanktonic organic material (OM) during digestion by herbivorous zooplankton is important from both biological and geochemical standpoints. Studies in the open ocean have demonstrated that

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“…Dietary net phytoplankton N is apportioned between fecal pellet egestion (25%), dissolved N excretion (34%), and production (4 1 %)-the percent-ages representing means calculated from Corner et al (1965) Abou Debs (1984) Landry et al (1984) and Kiorboe et al (1985) for a herbivorous diet. Ingested microzooplankton N was partitioned according to Corner et al (1976) for nauplii-fed Calanus between egestion (10%) excretion of dissolved N (39%) and production (5 1%).…”

Section: Notesmentioning

confidence: 99%

Size-fractionated measurements of nitrogen uptake in aged upwelled waters: Implications for pelagic food webs

Probyn

1990

Limnol. Oceanogr.

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Uptake of NO3−, NH4+, and urea was measured for the 200–20‐, 20–2‐, and <2‐µm size classes within the chlorophyll maximum layer in the Benguela upwelling system. Picoplankton and nanoplankton dominated in terms of biomass and activity both inshore and offshore. Net plankton N uptake declined drastically at night, whereas the smaller size classes maintained rates close to daytime levels. There was some evidence for N resource partitioning. Reduced N generally made up a higher proportion of the total N uptake by nanoplankton and picoplankton (for both size classes, mean = 94%) than by net plankton (mean = 63%). The contribution of nanoplankton and picoplankton NH4+ uptake always exceeded 50% of the total primary N production. In a regeneration‐based model with small cells dominating primary production it is conservatively estimated that carnivory on microzooplankton can contribute 14% toward the production of an omnivorous mesozooplankton assemblage.

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Effect of food acclimation on assimilation efficiency of Calanus pacificus1

Cited by 95 publications

References 2 publications

Coupling of ingestion and defecation as a function of diet in the calanoid copepod Acartia tonsa

Coupling of ingestion and defecation as a function of diet in the calanoid copepod Acartia tonsa

Digestion and alteration of the biochemical constituents of a diatom (Thalassiosira weisflogii) ingested by an herbivorous zooplankton (Calanus pacificus)

Size-fractionated measurements of nitrogen uptake in aged upwelled waters: Implications for pelagic food webs

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