Food Chain Efficiency Research Articles

Modeling and analysis of ecosystem dynamics based on the Lotka-Volterra model

In this paper, the ecological dynamics of sea lamprey populations were explored using the Lotka-Volterra model. Its ecosystem dynamics were also modeled. The analysis showed that changes in the sex ratio of sea lampreys can lead to a decrease in the abundance of other species within a certain range. Thus, changes in sex ratio affect the abundance of other species in the larger ecosystem. In addition, the study assessed the strengths and weaknesses associated with sea lamprey populations through iterative modeling. Six advantages (growth rate, environmental adaptation, importance in the food chain, ecosystem contribution, predation control, and reproductive efficiency) and four disadvantages (environmental stress, risk of overfishing, threats to reproduction, and threats to predation) were assessed in terms of population stability, reproductive fitness, and ecological impact. The results showed that when sex ratios were equal, the greatest advantage was predation control and the greatest disadvantage was overfishing risk. When males were dominant, the greatest advantage was adaptability, while the greatest disadvantage was predation threat.

Big data in the food supply chain: a literature review

The emergence of big data (BD) offers new opportunities for food businesses to address emerging risks and operational challenges. BD denotes the integration and analysis of multiple data sets, which are inherently complex, voluminous and are often of inadequate quality and structure. While BD is a well-established method in supply chain management, academic research on its application in the food ecosystem is still lagging. To fill this knowledge gap and capture the latest developments in this field, a systematic literature review was performed. Forty-one papers were selected and thoroughly examined and analysed to identify the enablers of BD in the food supply chain. The review primarily attempted to obtain an answer to the following research question: “What are the possibilities of leveraging big data in the food supply chain?“ Six significant benefits of applying BD in the food industry were identified, namely, the extraction of valuable knowledge and insights, decision-making support, improvement of food chain efficiencies, reliable forecasting, waste minimization, and food safety. Finally, some challenges and future research directions were outlined.

The Green Bay saga: Environmental change, scientific investigation, and watershed management

Abstract The Green Bay watershed, draining a total area of approximately 40,468 km2, comprises about a third of the Lake Michigan drainage. In the early years, fur trade was the dominant economic activity within the watershed. Later, when timber harvesting, papermaking, and agriculture came on the scene in the 19th and early 20th centuries, major environmental changes occurred in a relatively short period of time. Nutrient and sediment loadings, accompanied by organic wastes from sawmills and paper mills, resulted in a pollutant overload in the Fox River and in the eutrophication of the waters of lower Green Bay. Citizen complaints about these severely degraded conditions initiated a period of scientific investigation. Starting slowly with a few studies and surveys in the first half of the 20th century, serious investigatory work began at mid-century with support from the University of Wisconsin Sea Grant Institute. Examples of topics that have been investigated since then with support from numerous sources are: biological oxygen demand (BOD), phosphorus and total suspended solids loads, trophic status and food chain efficiencies, coastal wetland characterization, dynamics of the benthic layer, algae and abiotic solids, phosphorus cycling and mass balance, PCBs, seasonal hypoxia, and climate change impacts. These studies have provided the scientific foundation for government-led programs such as the Green Bay Remedial Action Program, the PCB clean-up program, and the TMDL program. Progress has been made—reduction in BOD is an example—but a fuller rehabilitation of this large-scale ecosystem remains an elusive goal. The saga goes on.

Predominant Non-additive Effects of Multiple Stressors on Autotroph C:N:P Ratios Propagate in Freshwater and Marine Food Webs

A continuing challenge for scientists is to understand how multiple interactive stressor factors affect biological interactions, and subsequently, ecosystems–in ways not easily predicted by single factor studies. In this review, we have compiled and analyzed available research on how multiple stressor pairs composed of temperature (T), light (L), ultraviolet radiation (UVR), nutrients (Nut), carbon dioxide (CO2), dissolved organic carbon (DOC), and salinity (S) impact the stoichiometry of autotrophs which in turn shapes the nature of their ecological interactions within lower trophic levels in streams, lakes and oceans. Our analysis from 66 studies with 320 observations of 11 stressor pairs, demonstrated that non-additive responses predominate across aquatic ecosystems and their net interactive effect depends on the stressor pair at play. Across systems, there was a prevalence of antagonism in freshwater (60–67% vs. 47% in marine systems) compared to marine systems where synergism was more common (49% vs. 33–40% in freshwaters). While the lack of data impeded comparisons among all of the paired stressors, we found pronounced system differences for the L × Nut interactions. For this interaction, our data for C:P and N:P is consistent with the initial hypothesis that the interaction was primarily synergistic in the oceans, but not for C:N. Our study found a wide range of variability in the net effects of the interactions in freshwater systems, with some observations supporting antagonism, and others synergism. Our results suggest that the nature of the stressor pairs interactions on C:N:P ratios regulates the “continuum” commensalistic-competitive-predatory relationship between algae and bacteria and the food chain efficiency at the algae-herbivore interface. Overall, the scarce number of studies with even more fewer replications in each study that are available for freshwater systems have prevented a more detailed, insightful analysis. Our findings highlighting the preponderance of antagonistic and synergistic effects of stressor interactions in aquatic ecosystems—effects that play key roles in the functioning of feedback loops in the biosphere—also stress the need for further studies evaluating the interactive effects of multiple stressors in a rapidly changing world facing a confluence of tipping points.

Bioethanol potential from miscanthus with low ILUC risk in the province of Lublin, Poland

AbstractIncreasing production of biofuels has led to concerns about indirect land‐use change (ILUC). So far, significant efforts have been made to assess potential ILUC effects. But limited attention has been paid to strategies for reducing the extent of ILUC and controlling the type of LUC. This case study assesses five key ILUC mitigation measures to quantify the low‐ILUC‐risk production potential of miscanthus‐based bioethanol in Lublin province (Poland) in 2020. In 2020, a total area of 196 to 818 thousand hectare of agricultural land could be made available for biomass production by realizing above‐baseline yield developments (95–413 thousand ha), increased food chain efficiencies (9–30 thousand ha) and biofuel feedstock production on underutilized lands (92–375 thousand ha). However, a maximum 203–269 thousand hectare is considered legally available (not protected) and biophysically suitable for miscanthus production. The resulting low‐ILUC‐risk bioethanol production potential ranges from 12 to 35 PJ per year. The potential from this region alone is higher than the national Polish target for second‐generation bioethanol consumption of 9 PJ in 2020. Although the sustainable implementation potential may be lower, the province of Lublin could play a key role in achieving this target. This study shows that the mitigation or prevention of ILUC from bioenergy is only possible when an integrated perspective is adopted on the agricultural and bioenergy sectors. Governance and policies on planning and implementing ILUC mitigation are considered vital for realizing a significant bioenergy potential with low ILUC risk. One important aspect in this regard is monitoring the risk of ILUC and the implementation of ILUC mitigation measures. Key parameters for monitoring are land use, land cover and crop yields.

Mechanisms of compensatory dynamics in zooplankton and maintenance of food chain efficiency under toxicant stress.

Communities with species that are tolerant to environmental stresses may be able to maintain the ecosystem functions under the stress, because the tolerant species can compensate for the loss of sensitive species. In this study, we focused on the food chain efficiency (FCE), the trophic transfer across three trophic levels, as an important process for ecosystem function, and examined the conditions under which such compensation could occur with aquarium experiments using an insecticide (methomyl) as the stressor. Our aquariums included one of two pairs of insecticide-tolerant and insecticide-sensitive cladoceran species, and a fish as the predator. The response of FCE to the insecticide stress, as indicated by the fish biomass production, depended on the zooplankton species combinations. FCE and total zooplankton biomass were maintained in the pair in which the compensatory changes of species abundances were clear, whereas they decreased in the pair in which the compensatory changes were not clear. This indicated the compensatory dynamics in the zooplankton community responsible for the observed resistance to the stress. We inferred the driving factors for the compensatory dynamics and the community resistance with respect to species traits of ecological importance, and concluded that a dissimilarity between species as regards the tolerance trait and a clear trade-off between the tolerance and the competitive ability was required to drive the compensatory dynamics, and a similarity or a superiority of the tolerant species as regards the functional effect trait (the predator avoidance and the reproductive potential) were required to maintain FCE.

Effects of light, nutrients, and food chain length on trophic efficiencies in simple stoichiometric aquatic food chain models

Ecological trophic transfer efficiencies can provide meaningful measures of ecosystem function. Light levels, nutrient availability, and food chain length impact ecological interactions and can cause elemental imbalances between trophic levels which may lead to stoichiometric constraints on food chain efficiencies. Despite the important role that the chemical composition of primary producers and food quality plays in determining consumer productivity, most food chain models used to evaluate trophic transfer efficiencies neglect stoichiometric constraints. This study presents simple stoichiometric models of two and three trophic levels and investigates the effects of light and nutrient availability on ecological transfer efficiencies. The models predict that food chain efficiency is reduced when consumers are nutrient limited. Nutrient levels such that the primary producer and consumer have similar stoichiometric compositions provide conditions for high food chain efficiency. In fixed low nutrient environments, food chain efficiency is highest in light level conditions such that the primary producer and consumer have similar stoichiometric compositions. In fixed high nutrient environments, food chain efficiency is highest for intermediately low light levels such that the phosphorus:carbon ratio of the primary producer is higher than the phosphorus:carbon ratio of the consumer. Food chain efficiency is lower in tritrophic food chains than ditrophic food chains and consumer efficiency is lower in the presence of predation constraints. It is essential for future models to consider light and nutrient availability and the consequential stoichiometric constraints when predicting how energy and elements transfer across trophic levels and up food chains.

Light and nutrients regulate energy transfer through benthic and pelagic food chains

The amount of energy flowing to top trophic levels depends on primary production and the efficiency at which it is converted to production at each trophic level. In aquatic systems, algal production is often limited by light and nutrients, and the nutritional quality of algae depends on the relative balance of these two resources. In this study, we used a mesocosm experiment to examine how light and nutrient variation affected food chain efficiency (FCE, defined as the proportion of primary production converted to top trophic level production), using a food web with benthic and pelagic food chains. We also related variation in benthic and pelagic efficiencies to the nutritional quality of primary producers, i.e. carbon:nitrogen:phosphorus stoichiometry. As predicted, pelagic and benthic FCEs were highest under low light/high nutrient conditions, the treatment with the best algal food quality, i.e. the lowest C:nutrient ratios. Pelagic FCE and pelagic herbivore efficiency (HEP) were more responsive than benthic FCE to variation in light and nutrients. Furthermore, pelagic FCE and HEP were highly correlated with algal C:P, suggesting ‘carryover effects’ of algal food quality on carnivores (larval fish) via effects on herbivore (zooplankton) quality. Benthic (tadpole) production was primarily explained by primary production rate, suggesting food quantity rather than quality drives their production. However, benthic FCE was also highest at low light/high nutrients and was significantly correlated with food quality. The stronger effect of food quality in mediating pelagic compared to benthic efficiencies, is consistent with differences in the stoichiometric mismatches between algae and consumers. Pelagic FCE and HEP were more likely to be P‐limited, whereas benthic FCE was more likely N‐limited. This study is the first to examine both pelagic and benthic FCE within the same system, and highlights the importance of differential consumer needs in determining how food quality affects energy transfer efficiency.

Functional traits of herbivores and food chain efficiency in a simple aquatic community model

Large-bodied zooplankton play important roles in the flow of nutrients and energy along the food chain in freshwater ecosystems. However, the importance of functional traits of zooplankton in trophic flow is not well understood. We used the minimal food-chain model, which includes producers (algae), first-order consumers (grazer zooplankton), and secondary consumers (fish), to reveal which functional traits of phyto- or zooplankton affect one of the most important ecosystem processes for functioning, the trophic transfer efficiency (TTE) across three trophic levels. Numerical simulations indicated that, regardless of the level of nutrient loading and the fish density, the conversion coefficient of grazer zooplankton was one of the most important and general factors for determining TTE. The antipredator defense and maximum grazing rate of zooplankton greatly affected TTE, but the effect depended on the level of nutrient loading and the fish density. For an ecosystem that had high nutrient loading and high fish density and in which the zooplankton density was regulated by the top-down effect, antipredator defense and maximum grazing enhanced TTE. Opposite relationships were observed for other states of the ecosystem. In general, those functional traits of the first-order consumers that affected vertical ecological interaction were important for trophic flow in the ecosystem, whereas the sensitivity of trophic flow to these traits depended largely on whether the zooplankton were regulated by the bottom-up or the top-down effect.

Food Retailing and Consumer Food Prices in Slovenia

This article focuses on agro-food chains and agro-food consumer prices in Slovenia considering its European Union (EU) membership. As the Slovenian agro-food markets were distorted prior to the EU accession with some agro-food prices that were greater than comparable EU prices, the empirical results confirm that with the EU membership Slovenian real agro-food consumer prices have largely adjusted downward. Besides policy changes, internalization of retailing and distribution chains by entries of supermarkets and hypermarkets have had impacts on market structures and rationalization of marketing activities. Supermarkets and hypermarkets are taking over a substantial proportion of retail trade in agro-food products with implications on increasing food chain efficiency by squeezing structures in consumer prices, as well as farmers, processors, and marketing margins for main agro-food staples. After the greater price adjustment changes that occurred by the EU membership, some stabilizations in agro-food markets is occurring, but at different levels of real consumer and producer prices and marketing margins. This implies that agro-food markets in the new EU member states are becoming much more integrated into internationally competitive markets, where pricing, sales promotion issues, and branding are taking an important role in the market segmentation of agro-food products.

Light, nutrients, and food-chain length constrain planktonic energy transfer efficiency across multiple trophic levels

The efficiency of energy transfer through food chains [food chain efficiency (FCE)] is an important ecosystem function. It has been hypothesized that FCE across multiple trophic levels is constrained by the efficiency at which herbivores use plant energy, which depends on plant nutritional quality. Furthermore, the number of trophic levels may also constrain FCE, because herbivores are less efficient in using plant production when they are constrained by carnivores. These hypotheses have not been tested experimentally in food chains with 3 or more trophic levels. In a field experiment manipulating light, nutrients, and food-chain length, we show that FCE is constrained by algal food quality and food-chain length. FCE across 3 trophic levels (phytoplankton to carnivorous fish) was highest under low light and high nutrients, where algal quality was best as indicated by taxonomic composition and nutrient stoichiometry. In 3-level systems, FCE was constrained by the efficiency at which both herbivores and carnivores converted food into production; a strong nutrient effect on carnivore efficiency suggests a carryover effect of algal quality across 3 trophic levels. Energy transfer efficiency from algae to herbivores was also higher in 2-level systems (without carnivores) than in 3-level systems. Our results support the hypothesis that FCE is strongly constrained by light, nutrients, and food-chain length and suggest that carryover effects across multiple trophic levels are important. Because many environmental perturbations affect light, nutrients, and food-chain length, and many ecological services are mediated by FCE, it will be important to apply these findings to various ecosystem types.

Relationships between hydrography, phytoplankton production, biomass, cell size and species composition, and copepod production in the southern Benguela upwelling system in April 1988

Hydrography and plankton were sampled along a cross-shelf transect off the Olifants River. South Africa, in April 1988, during a relaxation phase of upwelling. Chlorophyll concentrations were similar across the shelf, 3–5 μg chl a·ℓ−1. Midshelf, c. 80 per cent of the chlorophyll a was in cells > 10 μm, but nearshore 90 per cent was in cells < 10 μm. Large cells (diatoms) dominated midshelf waters and small cells (flagellates) nearshore waters. Smaller copepods (Paracalanus parvus, Ctenocalanus vanus, Centropages brachiatus and Oithona spp.) were most abundant shorewards of the 130 m isobath; larger ones (Calanus australis and Rhincalanus nasutus) were most abundant farther offshore. Calanoides carinatus was equally abundant at all stations. Primary production averaged 2,4 g C·m−2·day−1 at the large-cell stations and 1,5 g C·m−2·day−1 at the small-cell stations. In all, 69 and 29 per cent of the production was in the > 10 μm size fraction and 15 and 48 per cent in the fraction <2 μm at the large- and small-cell stations respectively. Rates of egg production of female C. australis, C. carinatus, C. brachiatus and P. parvus averaged 43 per cent of maximum at the large-cell stations but only 8 per cent of maximum at the small-cell stations. Growth rates of small juvenile copepods (<5–10 μg dry mass) were at their maximum, but those of larger individuals were less than maximum, suggesting food-limitation of growth. Rates of copepod production were similar in both water types, 4,1 and 3,6 mg C·m−3·day−1. Food-chain efficiency (FCE), the ratio of secondary to primary production, ranged from 3,5 to 12,5 per cent. Copepods consumed 12–42 per cent of the primary production. The FCE and the absolute proportion of phytoplankton consumed were dependent upon which sizes of phytoplankton were assumed eaten by the grazers.

Energy and protein balances in traditional livestock systems and ranching in eastern Botswana

Gross energy and crude protein balances of cattle in traditional systems and ranching in eastern Botswana have been estimated. The calculations show that ranching is more productive on a per animal basis while traditional systems are more productive on a per hectare basis. Ranching appears to be more efficient than traditional systems in terms of animal gross energy produced per unit of gross energy used for maintenance. Traditional systems, on the other hand, appear to be more efficient in terms of animal gross energy produced per unit of plant energy produced, and in terms of food chain efficiency. The same conclusions were drawn when crude protein balances were considered. The risk of pasture degradation might be greater at the higher stocking rates found in traditional systems, and feed shortages might occur more often, but lower stocking rates and ranch-type changes in product allocation in these systems would most probably lead to lower productivity per hectare. Consequently, this would lead to lower food production and less employment on a national scale. A socio-economic analysis at a national level is urgently needed to be able to weigh the advantages and disadvantages of the development of ranching at the cost of traditional systems.

Laboratory studies of the effect of predation on production and the production:biomass ratio of the opportunistic polychaete Capitella capitata (Type I)

The effect of simulated predation upon the secondary production and P:B (production:biomass) ratio of the polychaete Capitella capitata (Type I) was estimated from laboratory studies. The first method (the maximum sustainable yield, MSY, method) summed net increases in biomass of each population over time with biomass exploited by predation. In the specific growth-rate method, experimentally determined specific-growth rates were applied to changes in size classes and standing stock over time, providing another estimate of production for comparison to the MSY method. Predation had a pronounced effect on the magnitude of production, standing stocks, and hence the P:B ratio causing a fourfold difference in P:B ratios between the controls (P:B=4.9) and the 23% wk-1 predation rate (P:B=19.6). Production reached a high of 87 g ash-free dry wt m-2 yr-1 in the highest predation treatment (23% wk-1). An estimate of the number of individuals recruited in each population showed that predation caused an increase in population turnover rate. Gross ecological efficiency (calories of food ingested by the predator/calories of food consumed by the prey) and food-chain efficiency (calories of prey ingested by the predator/calories of food supplied to the prey) were 7.4 and 5.8% respectively, for the 23% wk-1 predation treatment.

DIMENSIONING OF A MASS ALGAL CULTURE FACILITY FOR THE TEMPERATE ZONE NURSERY CULTURE OF BIVALVE MOLLUSCS

ABSTRACTAquacultural Research Corporation (ARC) has operated a continuous mass algal culture facility for the nursery culture of the hard clam (Mercenaria mercenaria) for twenty years. Procedures have been developed for the mass culture of selected species of microalgae that are of proven nutritional value for rearing bivalve spat. Within the past three years a 60% increase in algal yield has been achieved by selection of small centric diatoms for mass culture and by empirical determination of optimum depths and seasonal dilution rates for the light limited 40 m3 continuous cultures. Cell densities of the diatoms Thalassiosira pseudonana (3H) and Skeletonema sp. have averaged over 109 cells/liter from March through November. The algal pond surface area necessary to support a hypothetical nursery with a monthly average clam biomass of 8 kg dry meat weight (ca 13 × lo6 clam seed) was calculated for latitude 41°N during the four seasons of the year. These calculations were based on 1982–1983 algal yields and an assumed food chain efficiency of 10%. The required minimum algal pond surface area ranged from 192 m2 in summer to 750 m2 in winter. The current ARC nursery operation is compared with this hypothetical model. Costs of nursery seed production and a proposed strategy for minimizing the seasonal algal areal requirements of a temperate zone bivalve nursery are discussed.

Bivalve production and food chain efficiency in an experimental nursery system

An experiment was performed to assess the productivity, food chain efficiency and nitrogen conversion efficiency of a semi-closed nursery system for bivalve spat held in upwelling columns. Algal blooms were encouraged by nutrient enrichment of onshore tanks and maintained for short periods under grazing pressure from bivalves.

Feed conversion efficiency and the efficiency of the UK food chain

The efficiency of transfer of food energy across various components of the human food chain is calculated for the UK. The processing and presentation stages have overall efficiencies of transfer of 0·75 and 0·93, respectively, with foods of animal origin mainly showing higher efficiencies of transfer through these processes. The efficiency of agriculture, related to a hypothetical maximum potential biomass production, is 0·026, with relatively lower efficiencies for the livestock industries. Yields of food energy from crops and livestock in the UK are calculated as 33 and 4 GJ per hectare, respectively. The factors affecting animal feed conversion efficiency are examined and it is shown that there is a potential conflict between high animal feed conversion and overall food chain efficiency. The consequences of this conflict—and possibilities for optimisation—are examined in terms of a simple resource allocation model.

Detritus in the Lake Ecosystem

Present views of the roles of detritus are not consistent with the ecosystem concept, and result in an underestimation of the importance of carbon and energy pathways involving detritus. Nonpredatory losses from a plant-herbivore transfer, particularly as dissolved organic matter and egestion, may be greater than the amount of material and energy transmitted up the grazer food chain. Ecosystem efficiencies are significantly higher than Lindeman (food chain) efficiencies. Benthic anaerobic metabolism (CO2 production) is greater than benthic oxygen uptake estimates indicate, and the energy-rich intermediate products which undergo deferred respiration (O2 uptake) far from their origin may create redox gradients, drive chemosynthesis, and subsidize bacterial photosynthesis in the water column. Thus, aquatic detrital material, particulate and dissolved, and its metabolism create a dynamic structure in lake sediments and water somewhat analogous to the trophic-dynamic aspect of the biota. However, detrital-dynamic structure in lakes is not simply an alternative mode of support for biota, but is a major factor in the entrainment of abiotic substances which subsidizes the biota.

Biomass production in mass cultures of marine phytoplankton at varying temperatures

Natural populations of marine phytoplankton obtained from a large outdoor pond were grown on waste water-sea water mixtures in laboratory continuous cultures in the temperature range 5–33 °C. Virtually all of the influent inorganic nitrogen (14.0 mg l −1) was assimilated at every temperature tested. There was, however, a distinct change in dominant species with temperature: below 19.8 °C Phaeodactylum tricornutum was dominant, at 27 °C Nilzschia sp. was the main species, and as the temperature increased above 27 °C a blue-green alga, Oscillatoria sp., became increasingly dominant. There is some indication that the excellent growth of P. tricornutum below 10 °C was related to a dramatic increase in the nutrient content per cell as the temperature decreased. Thus at low temperatures reduced division rates are compensated for by increased nutrient uptake rates. It follows that there is a transfer of phytoplankton protein from numerous small cells at intermediate temperatures to large cells that are reduced in numbers at lower temperatures but which represent the same total organic matter. The effect of this phenomenon on annual food chain efficiencies in both controlled and natural marine ecosystems is unknown.

Water availability and its influence on the structure and dynamics of a savannah large mammal community

SummaryThe Amboseli ecosystem is in a semi‐arid savannah environment in which water availability is highly seasonal, a feature which has an important bearing on the structure and efficiency of the large mammal community.Data are presented to show that the seasonal movements, a wet season dispersal and dry season concentration of water‐dependent species (obligate drinkers) can be related to the seasonality of rainfall and water availability, but that similar patterns do not prevail in the water‐independent species.Evidence suggests that water availability is a crucial parameter in calculating the carrying capacity of a range, and that the duration of ephemeral supplies, which reflect rainfall seasonality, evapotranspiration, and soil water storage capacity, is equally important. A simplified model is presented which calculates the carrying capacity of water‐bound communities–taking into account these two limiting factors.There appears to be a physiological barrier to a heavy utilization of the low water content grasses beyond reach of the water‐dependent species, since most water‐independent species select high water content browse in order to maintain a positive water balance. Significantly, while the water‐independent community is almost exclusively composed of browsers, most water‐dependent species are grazers. The biomass density of large mammals beyond 15 km from water, a radius which encloses 99‐5% of the biomass of water‐dependent species, is extremely low compared to areas within 10 km of water.As a consequence of the physiological barrier to a heavy utilization of low water content forage in water‐deficient areas, the food chain efficiencies are appreciably lower than those with permanent water sources. Livestock development programmes have long appreciated this constraint and employed water development schemes to increase range‐carrying capacity.Seasonality in the movement patterns of Amboseli is compared to other large mammal communities and management implications are discussed.