Food network unfolding: An extension of trophic dynamics for application to natural ecosystems

Higashi, Masahiko; Burns, Thomas P.; Patten, Bernard C.

doi:10.1016/s0022-5193(89)80132-8

Cited by 44 publications

(31 citation statements)

References 19 publications

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“…For nitrogen for instance, an Ulva can take up nitrate coming directly from a tributary, but also ammonia excreted by zooplankton, having grazed phytoplankton grown on the nitrate coming from this tributary, or nitrate issued from the slow remineralization of dead ulvae buried in sediment, etc. In an attempt at a theoretical unfolding of food web networks, Higashi et al (1989) introduced the notion of utilization coefficient n ij as the total portion of the steady-state flow through compartment j that is ultimately experienced by consumer i. On the basis of a matrix approach of steady flows through a food web having possible recirculation paths, the Higashi et al trophic network analysis aims at the same objective as our technique, but in pure biological food webs, free from physical constraints caused by their environment (e.g., transport by geophysical fluids) and considered at equilibrium.…”

Section: Discussionmentioning

confidence: 99%

A new numerical technique for tracking chemical species in a multi‐source, coastal ecosystem, applied to nitrogen causing Ulva blooms in the Bay of Brest (France)

Ménesguen

Cugier

Leblond

2006

Limnology & Oceanography

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A new numerical technique is presented that allows the tracking of any chemical element from any source in a simulated foodweb, for instance assessing the proportion of these sources (river loadings, sea entrances, point sources) in the algal diet for the limiting nutrient. An application is shown for nitrogen in an Ulva bloom occurring in a shallow embayment connected with a strongly tidally stirred ecosystem with various sources of inorganic nitrogen, the Bay of Brest, Brittany, France. In a first step, a biogeochemical three-dimensional model was developed to simulate growth and erosion-transport-deposition of free-floating ulvae; this model was able to converge on a realistic distribution of Ulva deposits after a few months, even though it was initialized with a strongly unrealistic distribution of settled ulvae. In a second step, and unfortunately for recovery plans, the tracking technique, applied in this model to all the nitrogen sources entering the bay, revealed that the small, nitrate-polluted rivers flowing directly into the eutrophicated area had a negligible effect, whereas more distant but stronger sources, a big river and a big urban sewage plant, even after dilution, accounted for about 50% and 20%, respectively, of the algal nitrogen content during summer. Despite its high N flux, open ocean contributes only 15% to Ulva growth. The suppression of only one of the main nitrogen sources would not significantly decrease the Ulva bloom, because of the high nitrogen surplus present in the site. The remaining sources would still saturate the needs of the maximum Ulva biomass the site is able to produce. The tracking technique, however, shows that the N turnover in Ulva is only 4 months. Thus, improvements would occur within a year following large N reductions.

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Section: Discussionmentioning

confidence: 99%

A new numerical technique for tracking chemical species in a multi‐source, coastal ecosystem, applied to nitrogen causing Ulva blooms in the Bay of Brest (France)

Ménesguen

Cugier

Leblond

2006

Limnology & Oceanography

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“…(2) While behaviorally there may be top predators, functionally there is no top as far as energy flow is concerned, only continuous dissipative paths reaching as a limit process beyond the level of n-trophic steps (Higashi et al, 1988;Whipple, 1998). (3) Detritus is not a disconnected, infinite-source, basal compartment but receives input from the rest of the ecological community.…”

Section: Discussionmentioning

confidence: 99%

Cyclic energy pathways in ecological food webs

Fath

Halnes

2007

Ecological Modelling

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Detritus Energy flowFood webs Network analysisTrophic dynamics a b s t r a c t Standard ecology textbooks typically maintain that nutrients cycle, but energy flows in unidirectional chains. However, here we use a new metric that allows for the identification and quantification of cyclic energy pathways. Some of these important pathways occur due to the contribution of dead organic matter to detrital pools and those organisms that feed on them, reintroducing some of that energy back into the food web. Recognition of these cyclic energy pathways profoundly impacts many aspects of ecology such as trophic levels, control, and the importance of indirect effects. Network analysis, specifically the maximum eigenvalue of the connectance matrix, is used to identify both the presence and strength of these structural cycles.

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“…The main difference between the three methods lies in that in the C algorithm TP is computed using only trophic links; the other two make use also of non‐trophic flows (i.e. detrital pathways; Ulanowicz and Kemp 1979, Higashi et al 1989, Whipple and Patten 1993, Whipple 1998). In the C algorithm, TP is the weighted average length of all the loopless pathways from the primary source of energy to any species.…”

Section: Methodsmentioning

confidence: 99%

“…An organism j feeding on this species would thus receive an amount of energy from i h and another from i c so that it would be partially primary carnivore and partially secondary carnivore. By keeping track of these successive fractions throughout the web one can unfold the original networks in multiple linear trophic pathways, each one representing a particular chain of transfers that a unit of energy experiences in the ecosystem (Higashi et al 1989).…”

Section: Methodsmentioning

confidence: 99%

Using trophic hierarchy to understand food web structure

Scotti¹,

Bondavalli²,

Bodini³

et al. 2009

Oikos

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Link arrangement in food webs is determined by the species’ feeding habits. This work investigates whether food web topology is organized in a gradient of trophic positions from producers to consumers. To this end, we analyzed 26 food webs for which the consumption rate of each species was specified. We computed the trophic positions and the link densities of all species in the food webs. Link density measures how much each species contributes to the distribution of energy in the system. It is expressed as the number of links species establish with other nodes, weighted by their magnitude. We computed these two metrics using various formulations developed in the ecological network analysis framework. Results show a positive correlation between trophic position and link density across all the systems, regardless the specific formulas used to measure the two quantities. We performed the same analysis on the corresponding binary matrices (i.e. removing information about rates). In addition, we investigated the relation between trophic position and link density in: a) simulated binary webs with same connectance as the original ones; b) weighted webs with constant topology but randomized link strengths and c) weighted webs with constant connectance where both topology and link strengths are randomized. The correlation between the two indices attenuates, vanishes or becomes negative in the case of binary food webs and simulated data (weighted and unweighted). According to our analysis, link density in food webs decreases with trophic position so that it is greatly reduced toward the top of the trophic hierarchy. This outcome, that seems to challenge previous conclusions based on null models, strongly depends on link quantification. Including interaction strengths may improve substantially our understanding of food web organization, and possibly contradict results based on the analysis of binary webs.

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Food network unfolding: An extension of trophic dynamics for application to natural ecosystems

Cited by 44 publications

References 19 publications

A new numerical technique for tracking chemical species in a multi‐source, coastal ecosystem, applied to nitrogen causing Ulva blooms in the Bay of Brest (France)

A new numerical technique for tracking chemical species in a multi‐source, coastal ecosystem, applied to nitrogen causing Ulva blooms in the Bay of Brest (France)

Cyclic energy pathways in ecological food webs

Using trophic hierarchy to understand food web structure

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