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.

Models on the Slope of, and Biomass Flow up, the Biomass Size Spectrum

1987 ◽  
Vol 44 (S2) ◽  
pp. s136-s140 ◽  
Author(s):  
Uwe Borgmann
Keyword(s):  
Somatic Growth ◽  
Production Data ◽  
Food Chains ◽  
Size Spectrum ◽  
Allometric Relationship ◽  
Complex Models ◽  
Simple Equations ◽  
Growth And Reproduction ◽  
Biomass Size Spectrum ◽  
Number Of Authors

A comparison is made between the different models of the biomass size spectrum proposed by a number of authors. Though superficially dissimilar, the models are all mathematically compatible if the differences in their underlying assumptions are taken into account. The simplest model does not consider the complexities of food webs over food chains, somatic growth, or the continuous nature of the size spectrum. Comparison with the more complex models, however, shows that these omissions do not seriously affect the slope of the size spectrum. For example, one model predicts that the effects of somatic growth and reproduction cancel if cohort biomasses remain relatively constant as the cohorts mature. If growth rate is related to body size in an allometric relationship and reproduction is ignored, then another model gives a slightly different slope (higher by roughly 0.03). If the same assumptions are used in both models, however, they give compatible results. Some simple equations are suggested for routine application in size spectrum analysis of biomass and production data.

scholarly journals A modified niche model for generating food webs with stage-structured consumers: The stabilizing effects of life-history stages on complex food webs

2021 ◽  
Author(s):  
Etsuko Nonaka ◽  
Anna Kuparinen
Keyword(s):  
Life History ◽  
Food Web ◽  
Food Webs ◽  
Stage Structure ◽  
Niche Overlap ◽  
Life History Stage ◽  
Bioenergetic Model ◽  
Niche Model ◽  
Life History Stages ◽  
Growth And Reproduction

1. Almost all organisms grow in size during their lifetime and switch diets, trophic positions, and interacting partners as they grow. Such ontogenetic development introduces life-history stages and flows of biomass between the stages through growth and reproduction. However, current research on complex food webs rarely considers life-history stages. The few previously proposed methods do not take full advantage of the existing food web structural models that can produce realistic food web topologies. 2. We extended the niche model by Williams & Martinez (2000) to generate food webs that included trophic species with a life-history stage structure. Our method aggregated trophic species based on niche overlap to form a life-history structured population; therefore, it largely preserved the topological structure of food webs generated by the niche model. We applied the theory of allometric predator-prey body mass ratio and parameterized an allometric bioenergetic model augmented with biomass flow between stages via growth and reproduction to study the effects of a stage structure on the stability of food webs. 3. When life-history stages were linked via growth and reproduction, fewer food webs persisted while persisting food webs tended to retain more trophic species. Topological differences between persisting linked and unlinked food webs were small to modest. Temporal variability of biomass dynamics and slopes of biomass spectra were lower in the linked food webs than the unlinked ones, suggesting that a life-history stage structure enhanced stability of complex food webs. 4. Our results suggest a positive relationship between the complexity and stability of complex food webs. A life-history stage structure in food webs may play important roles in dynamics of and diversity in food webs.

Effects of Ocean Acidification on Pelagic Organisms and Ecosystems

2011 ◽  
Author(s):  
Ulf Riebesell ◽  
Philippe D. Tortell
Keyword(s):  
Ocean Acidification ◽  
Food Web ◽  
Food Webs ◽  
Spatial Scales ◽  
Scale Up ◽  
Carbonate System ◽  
Marine Food Web ◽  
Pelagic Food Webs ◽  
Carbon Pump ◽  
Marine Food

Over the past decade there has been rapidly growing interest in the potential effects of ocean acidification and perturbations of the carbonate system on marine organisms. While early studies focused on a handful of phytoplankton and calcifying invertebrates, an increasing number of investigators have begun to examine the sensitivity to ocean acidification of various planktonic and benthic organisms across the marine food web. Several excellent review articles have recently summarized the rapidly expanding literature on this topic (Fabry et al. 2008; Doney et al. 2009 ; Joint et al. 2011). The focus of this chapter is on the potential ecosystem-level effects of ocean acidification. Starting with a brief review of the basic physical, chemical, and biological processes which structure pelagic marine ecosystems, the chapter explores how organismal responses to perturbations of the carbonate system could scale up in both time and space to affect ecosystem functions and biogeochemical processes. As with many chapters in this volume, and indeed much of the ocean acidification literature at present, our review raises more questions than it answers. It is hoped that these questions will prove useful for articulating and addressing key areas of future research. Complexity in marine pelagic food webs results from the interactions of multiple trophic levels across a range of temporal and spatial scales. The traditional view of marine food webs (Steele 1974) involved a relatively short trophic system in which large phytoplankton (e.g. net plankton such as diatoms) were grazed by a variety of mesozooplankton (e.g. copepods), which were in turn consumed by second-level predators, including many economically important fish and invertebrate species. This ‘classic’ marine food web is typical of high-productivity regions such as coastal upwelling regimes (Lassiter et al. 2006). A characteristic feature of these systems is a strong decoupling between primary production and grazing, which results from the different metabolic rates of consumers and producers and, in many cases, ontogenetic and seasonal delays in the emergence of feeding predators. The uncoupling between phytoplankton and their consumers leads to significant export of organic material out of the euphotic zone, the so-called biological carbon pump (discussed further below).

Stable carbon isotopes as pelagic food web tracers in adjacent shelf and slope regions off British Columbia, Canada

1999 ◽  
Vol 56 (12) ◽  
pp. 2477-2486 ◽  
Author(s):  
R Ian Perry ◽  
Peter A Thompson ◽  
David L Mackas ◽  
Paul J Harrison ◽  
Douglas R Yelland
Keyword(s):  
British Columbia ◽  
Food Web ◽  
Food Webs ◽  
Stable Carbon Isotopes ◽  
Water Mass ◽  
Larval Fish ◽  
Deep Ocean ◽  
Food Web Interactions ◽  
Deep Ocean Water ◽  
Pelagic Food Webs

Surveys were conducted in spring 1992 to examine the use of 13C/12C ratios to differentiate pelagic food webs and to trace food web interactions between adjacent continental shelf and slope/deep ocean environments off southwestern British Columbia, Canada. Salinity was used to define shelf or slope/deep ocean water masses and their productivity conditions because eddies and meanders at the shelf break were observed to draw water off the shelf. The 13C/12C ratio of plankton was related to the mean upper layer (0-50 m) salinity. 13C abundance was enriched (relative to 12C) in the shelf water mass compared with the slope water mass. This enrichment persisted up the food web from particulate organic matter through three size-classes of zooplankton to larval fish. The cross-shelf spatial scale separating these food webs, as determined from spatial semivariograms of 13C/12C and the upper layer mean salinity, was 40-45 km, similar to the Rossby radius for eddies at this location (50 km). Larval fish may provide a means to monitor exchanges of plankton between geographically adjacent food webs if time scales for incorporation of new isotope signatures from diets into tissues are determined.

Changes in the δ13C of pelagic food webs: the influence of lake area and trophic status on the isotopic signature of whitefish (Coregonus lavaretus)

2004 ◽  
Vol 61 (8) ◽  
pp. 1485-1492 ◽  
Author(s):  
Marie-Elodie Perga ◽  
Daniel Gerdeaux
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Status ◽  
Dissolved Inorganic Carbon ◽  
Alpine Lakes ◽  
Coregonus Lavaretus ◽  
Lake Area ◽  
Pelagic Food Web ◽  
Pelagic Food Webs ◽  
Lake Size

We investigated the relationships between the pattern of variation of δ13C in pelagic food webs and various morphologic and trophic characteristics of peri-alpine lakes. We used the δ13C of whitefish (Coregonus lavaretus), a long-lived zooplanktivorous fish, to assess the isotope ratio of dissolved inorganic carbon (DIC) at the origin of the pelagic food web. The δ13C of DIC depends on its origin, which may be the atmosphere or the mineralization of organic matter. A synchronic study of 22 peri-alpine lakes shows that the surface area of the lake accounts for much of the variability of the δ13C in pelagic food webs (r2 = 0.76). The δ13C increases with lake size, which suggests that the origin of the DIC integrated into the pelagic food web depends on lake size. To differentiate the influence of trophic status from morphological effects, a diachronic study was performed on the δ13C of fish scales collected over the 20-year re-oligotrophication of Lake Geneva. The δ13C of whitefish increased with phosphorus concentration (r2 = 0.71). This pattern is related to the growing demand for atmospheric DIC as primary production increases.

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

scholarly journals Landscape heterogeneity buffers biodiversity of simulated meta-food-webs under global change through rescue and drainage effects

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Remo Ryser ◽  
Myriam R. Hirt ◽  
Johanna Häussler ◽  
Dominique Gravel ◽  
Ulrich Brose
Keyword(s):  
Habitat Fragmentation ◽  
Food Web ◽  
Food Webs ◽  
Landscape Heterogeneity ◽  
Landscape Connectivity ◽  
Biodiversity Loss ◽  
Mechanistic Explanation ◽  
Population Densities ◽  
Rescue Effect ◽  
Drainage Effect

AbstractHabitat fragmentation and eutrophication have strong impacts on biodiversity. Metacommunity research demonstrated that reduction in landscape connectivity may cause biodiversity loss in fragmented landscapes. Food-web research addressed how eutrophication can cause local biodiversity declines. However, there is very limited understanding of their cumulative impacts as they could amplify or cancel each other. Our simulations of meta-food-webs show that dispersal and trophic processes interact through two complementary mechanisms. First, the ‘rescue effect’ maintains local biodiversity by rapid recolonization after a local crash in population densities. Second, the ‘drainage effect’ stabilizes biodiversity by preventing overshooting of population densities on eutrophic patches. In complex food webs on large spatial networks of habitat patches, these effects yield systematically higher biodiversity in heterogeneous than in homogeneous landscapes. Our meta-food-web approach reveals a strong interaction between habitat fragmentation and eutrophication and provides a mechanistic explanation of how landscape heterogeneity promotes biodiversity.

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