Particle-Size-Conversion Efficiency and Total Animal Production in Pelagic Ecosystems

1982 ◽  
Vol 39 (5) ◽  
pp. 668-674 ◽  
Author(s):  
Uwe Borgmann
Keyword(s):  
Particle Size ◽  
Conversion Efficiency ◽  
Animal Production ◽  
Size Spectrum ◽  
Fish Production ◽  
Pelagic Ecosystem ◽  
Simple Equations ◽  
Zooplankton Production ◽  
Pelagic Ecosystems

A method is described for defining conversion efficiency in pelagic ecosystems on the basis of particle size, rather than trophic level, this permits calculation of a size-corrected biomass function which can be used to describe total animal production by taking into account biomass losses resulting from carnivorous feeding in multitrophic level systems. This, in turn, permits the determination of potential fish production, for any given size fish, from experimental data on zooplankton production using simple equations. Little knowledge of trophic interactions is required. The potential fish production resulting from microzooplankton production in the Burlington Canal is calculated. Keywords: conversion efficiency, production, pelagic ecosystem, particle-size spectrum

Particle-Size-Conversion Efficiency and Contaminant Concentrations in Lake Ontario Biota

1983 ◽  
Vol 40 (3) ◽  
pp. 328-336 ◽  
Author(s):  
Uwe Borgmann ◽  
D. M. Whittle
Keyword(s):  
Particle Size ◽  
Body Size ◽  
Conversion Efficiency ◽  
Food Chain ◽  
Lake Ontario ◽  
Dry Weight ◽  
Growth Efficiency ◽  
Fish Production ◽  
The Relationship ◽  
Zooplankton Production

The particle-size-conversion efficiency (log food consumption/production divided by log predator prey size ratio) is shown to be directly related to the relationship between the concentration of persistent contaminants accumulated primarily through the food chain and body size for organisms in pelagic ecosystems. The difference between particle-size-conversion efficiency for biomass and that for the contaminant gives the slope of the relationship between log contaminant concentration and log body size. This provides a useful theoretical framework for analyzing contaminant concentrations in aquatic biota without the need for specifying trophic level but still incorporating the idea of food chain accumulation. Concentrations of PCB, DDT, and mercury were examined in aquatic organisms from Lake Ontario, ranging in size from zooplankton to large salmonids (a 108 -fold range in dry weight). The slope of the double log plot of concentration versus weight varied from 0.20 to 0.22 for PCB and DDT and was approximately equal to 0.13 for mercury. This indicates that mercury is accumulated less efficiently through the food chain than PCB or DDT. After correcting for incomplete uptake and retention of the contaminant, an estimate of particle-size-conversion efficiency for biomass of about 0.26 was obtained, which agrees reasonably well with previous estimates obtained from growth efficiency experiments and analysis of particle-size spectra. These calculations indicate that potential fish production in Lake Ontario is ~ 120-fold lower than zooplankton production (for fish averaging 108-fold larger in body size as compared to zooplankton).Key words: particle-size-conversion efficiency, PCB, DDT, mercury, zooplankton production, fish production

Effect of Somatic Growth and Reproduction on Biomass Transfer up Pelagic Food Webs as Calculated from Particle-Size-Conversion Efficiency

1983 ◽  
Vol 40 (11) ◽  
pp. 2010-2018 ◽  
Author(s):  
Uwe Borgmann
Keyword(s):  
Particle Size ◽  
Food Web ◽  
Food Webs ◽  
Conversion Efficiency ◽  
Somatic Growth ◽  
Mysis Relicta ◽  
Biomass Transfer ◽  
Pelagic Food Webs ◽  
Simple Equations ◽  
Growth And Reproduction

Biomass or energy transfer up pelagic food webs to larger sized organisms is a function of (1) direct trophic level transfer through predation, (2) somatic growth, a process that augments biomass transfer through predation, and (3) reproduction, which impedes biomass transfer by moving biomass down the food web to smaller sizes. By assuming that particle-size-conversion efficiency (log (food consumed/biomass produced)/log (predator–prey size ratio)) is relatively constant, I derive simple equations to calculate the effect of somatic growth and reproduction on biomass transfer up the food web. This defines the conditions under which somatic growth and reproduction can be ignored and biomass flow can be calculated from predation alone, using a previously developed model. When these conditions are not met, the effect of somatic growth and reproduction can be calculated from data on cohort growth and mortality rates. It is not necessary to identify the food of any species. This eliminates one of the problems often encountered when modeling food webs. I have applied these equations to production of Mysis relicta. If the estimates of Mysis abundance and growth rates are correct, then size-corrected production is about 25% greater for this species when somatic growth is accounted for in the calculations. This is because mortality of young Mysis appears to be low and most production occurs during somatic growth and not during reproduction.

Particle-size-conversion Efficiency, Invertebrate Production, and Potential Fish Production in Lake Ontario

1994 ◽  
Vol 51 (3) ◽  
pp. 693-700 ◽  
Author(s):  
U. Borgmann ◽  
D. M. Whittle
Keyword(s):  
Particle Size ◽  
Body Size ◽  
Conversion Efficiency ◽  
Lake Trout ◽  
Lake Ontario ◽  
Contaminant Concentration ◽  
Fish Production ◽  
Rainbow Smelt ◽  
Pelagic Species ◽  
Size Relationship

The relationships between body size and p,p′-DDE and total PCB concentration in Zooplankton, mysids, amphipods, slimy sculpin (Cottus cognatus), rainbow smelt (Osmerus mordax), alewife (Alosa pseudo-harengus), and lake trout (Salvelinus namayeush) in Lake Ontario were determined for samples collected from 1989 to 1992. Amphipods, and to a lesser extent sculpins, had higher DDE and PCB concentrations than predicted from the contaminant concentration – body size relationship for the pelagic species. PCB, but not DDE, concentrations in Zooplankton were also abnormally high. For the pelagic species, excluding PCB concentrations in Zooplankton, the log contaminant concentration – log body size relationship had a slope of 0.23 (95% confidence limits = ±0.014). Combined with revised estimates of the efficiency of contaminant retention from one body size to another (ε′ = 0.05–0.10), the revised estimate of particle-size-conversion efficiency (ε) for Lake Ontario falls between 0.27 and 0.35. Recent estimates of invertebrate (Zooplankton, mysid, and amphipod) annual production average 18 g/m2 (dry weight) with upper and lower limit estimates of 14–27 g/m2. Using ε to extrapolate from invertebrate to fish production results in estimates of mean potential fish production in Lake Ontario of 1–7 kg/ha (wet weight), as compared with previously published estimates of 6 and 14 kg/ha.

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