Biological Science 2nd Edition Man 2005
Bascompte, in, 2009 OutlookFood web models can be seen both as an idealized representation of ecosystem complexity and as a source of information for the patterns we observe in natural systems. Food web models can be used as tools to investigate the properties of a system and its dynamics.
In the future, combining experiments with theoretical approaches will provide even more useful information on the underlying mechanisms driving marine ecosystem dynamics and linking food web dynamics with ocean’s biogeochemical cycles and climate change. Food web models can be used to address a community-wide approach to a growing set of problems observed in marine systems for which management solutions have not been clearly identified. In the marine environment these include depleted stocks of fish, declining marine mammal populations, receding ice cover, and changing pH (oceanic acidification). Taking responsibility for the multiple human contributions in each case is crucial to dealing with the complexity of problems through management. We can use empirical information and patterns that emerge from food web analysis as guidance for estimates of what is sustainable – exemplified by what is called in fisheries policy as the ‘ecologically allowable take’ (EAT). Finally, the analysis of ecological food webs in marine systems needs to be linked to management issues that require social and economic involvement.
Food web properties were consistent across all fragmented islands for five of the six sampling dates. Heavy flooding in October 2005 due to extensive rainfall in that month (see Fig. 3 ) led to widespread simplification of island food webs in December 2005. Many of the islands closest to the mainland had recovered in complexity by February 2006, but the islands farthest from the mainland remained species depauperate, with implications for food web structure. The species richness ( F 1,14 = 5.94, p = 0.030; see Fig.
5A and Table 4) and mean food chain length ( F 1,14 = 7.64, p = 0.015; see Fig. 5B and Table 4) of the island food webs decreased with increasing distance from the mainland in February 2006, when the proportion of basal species also increased with distance from the mainland ( F 1,14 = 5.66, p = 0.032; see Fig.
5C and Table 4). Comparing the nearest and furthest islands from the mainland clearly highlights this disparity in food web structure in February 2006 (see Fig. Food web properties for these two islands through time are also listed in Table 5. Note that no relationship was found between island area and any of the food web properties under investigation ( p 0.14; see Table 4). RVDistance from the mainlandIsland areaFPabr 2Fpabr 2S5.940.03015.077− 0.270.61112.113− 0.04430.019L2.500.13727.967− 0.440.51622.133− 0.15400.031L/S0.940.3481.898− 0.590.4571.773− 0.00810.040C3.370.0880.1170.000.9630.1490.00000.000SWTL7.640.0151.926− 0.390.5441.737− 0.00270.027B5.660.0320.2460.620.4430.3530.00230.043I2.650.1260.230− 0.390.1440.193− 0.00350.146T1.620.2240.524− 0.400.5350.4540.00120.028F and p values of the linear regressions are shown, along with intercepts ( a), slopes ( b), and r 2 values. Significant p values are highlighted in bold.
DateDistance (m)SLL/SCSWTLBITFeb 02.20.082.10.220.300.48Apr 82.00.112.00.210.260.53Jun 52.40.121.90.260.370.37Aug 51.80.131.80.290.140.57Dec 12.20.161.80.290.210.50Feb 62.30.072.30.150.300.55Feb 272.40.082.10.190.340.47Apr 272.40.072.10.140.250.61Jun 201.50.121.60.460.080.46Aug 211.90.121.80.310.190.50Dec 2.20.191.30.670.000.33Feb 232.60.092.30.180.290.54The month of sampling is given, along with the distance from the mainland in metres. S, number of species; L, number of trophic links; L/S, linkage density; C, directed connectance; SWTL, mean short-weighted trophic level; B, proportion of basal species; I, proportion of intermediate species; T, proportion of top species. Polovina, in, 2001 Food Web DynamicsFood webs of ocean gyres are altered by a range of factors, including fishing and variations in physical forcing resulting from climate fluctuations. The relationship between climate variation and ecosystem dynamics has been a focus of considerable research.
Changes in abundance of organisms at many trophic levels have been documented to vary coherently with various atmospheric indices, including the Aleutian Low in the Pacific and the North Atlantic Oscillation in the Atlantic. For example, in the North Pacific subarctic gyre, changes in the fishery catches of all species of salmon vary on timescales of decades, coherent with the intensity of the Aleutian Low Pressure System. While the link between the atmosphere and salmon productivity has not been resolved, a number of hypotheses suggest that changes in salmon carrying capacity result from changes in physical forcing that impact productivity at the bottom of the food web and propagate up the food web to salmon.
A change in the energy flow through the food web from the bottom up in response to climate variation is typical of many relationships described between climate and food web dynamics in ocean gyres.Fisheries in ocean gyres typically impact food webs through removals at top or mid-trophic levels. For example, longline or troll fisheries target apex predators including tunas, swordfish, marlins, and salmon, although some mid-trophic level species including squid can also be the target species. By-catch and incidental catches in ocean gyre fisheries also include apex species including sharks and protected species such as seabirds, marine mammals, and sea turtles. Data on the responses of oceanic gyre food webs to fishing are generally limited to harvested species, so the food web impacts at lower trophic levels are not documented. However, a dynamic ecosystem model has been used to investigate possible impacts and has found no evidence that the removal of any single high trophic level species significantly altered the food web. The lack of a keystone species appears to be due to a high degree of diet overlap among the high trophic level species.
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Fisheries in oceanic gyres alter the food web by reducing biomass at the top of the food web. When this reduction becomes substantial, it may result in some increase in biomass at mid-trophic levels. Food Web MetricDefinitionConnectance ( C)Number of links ( L)/number of species ( S) 2. The proportion of potential trophic links that do occur ( Warren, 1994)Linkage densityL/ S. Number of links per taxon.
Evaluating food webs constructed from a set of crops on unseen data from a different crop was done by repeatedly constructing food webs from all crops data, excluding test data from a particular crop ‘c’ and measuring the predictive accuracy on these test data. Figure 4.13A and B shows predictive accuracies of Vortis species-based and functional food webs on different crops. The average predictive accuracies (the proportions of correctly predicted left-out test examples) are reported with standard errors associated with each point. Due to different default accuracies for different crops, the learning curves start from different levels of accuracies. However, the overall increase in the average accuracies (when 0–100% of the training examples are provided) is around 16 for crops M and S and around 18 for crops W and B in the species-based food webs and around 16 for crops S and W and around 20 for crops M and B in the functional food webs. By averaging the predictive accuracies over different crops, we get overall predictive accuracies for species and functional food webs, as shown in Fig.
According to this figure, in all cases the predictive accuracies were significantly higher than the default accuracy of the majority class (55.6% for Vortis data). Learning curves for Vortis probabilistic food webs: (A) species food web and (B) functional food web on different crops; (C) overall species and functional food webs.Predictive accuracies for the functional food webs were the same or higher than their species-based counterpart, particularly at low to medium size of training examples. This suggests that the functional food webs are at least as accurate as their species-based counterpart, despite being much more compact. The apparent decline in the predictive accuracy for the functional food webs after the 50% point could be related to overfitting the training data.
Figure 4.14A–C shows similar learning curves for pitfall food webs and compare predictive accuracies of species and functional food webs when different percentage of the training data is provided. As shown in the graphs, the differences between the default accuracies for different crops are less than those from Vortis data, which makes the comparison easier. As for the Vortis data, the food web tested on crop B appear to have the highest overall increase in the predictive accuracies, both in the species-based and functional food webs ( Fig. 4.14A and B). Figure 4.14C suggests that the pitfall functional food webs closely follow their species-based counterpart, confirming what was observed for Vortis food webs, that is, functional food webs can accurately estimate species-based food webs.
Learning curves for pitfall probabilistic food webs: (A) species food web and (B) functional food web on different crops; (C) overall species and functional food webs.A comparison between Figs. 4.13A and 4.14A shows that the pitfall food webs have a higher overall increase in predictive accuracy (19 vs. 16), which suggest a relatively higher accuracy for pitfall food webs. Meador, in, 2008 Trophic TransferFood web transfer of PAH metabolites is another area that has received little attention.
Because many species can metabolize PAHs, it is generally assumed that trophic transfer and biomagnification (an increase in tissue concentration over two or more trophic levels) of these compounds is not important for food webs. Trophic transfer and biomagnification of PAHs is not expected for food webs involving vertebrates; however, species from the lower trophic levels that are not able to effectively metabolize these compounds may exhibit food web transfer if vertebrates are not involved. Even though parent PAHs may not be biomagnified, prey species may contain high levels of metabolites that could be accumulated by predators. A few studies have found that fish accumulate PAH metabolites after ingesting invertebrates that had metabolized these compounds. Because these metabolites can be very toxic, additional research examining bioaccumulation of PAH metabolites from ingested prey is very important for a complete understanding of trophic transfer and the potential for toxic effects. Strong, in, 2008Food webs make up all of ecological nature.
Because of their complex nature, food webs are usually simplified for analysis by ecologists. Some simplifications yield simple unbranched food chains, others yield interconnected chains, and yet others yield more complex food webs (which are still much less complex than all species and links found in the web in nature).
Every food web and chain has as its backbone, transfer of energy to consumers from producers; this is the bottom-up force. Some but not all webs and chains have opposite top-down effects, which attenuate and change bottom-up forces. Top-down effects are best understood in light of how they change bottom-up effects in food chains and webs. Decomposition is a food web process that often lacks top-down forces because the organisms that break down dead plant and animal material usually do not affect its supply rate. Perhaps the best-known example of strong top-down effects is the trophic cascade in lakes, while a well-researched example of the absence of top-down effects is to be found in the food webs of the aphids living in trees.
The lion’s share of net primary productivity on Earth becomes detritus. Detritivory can contribute substantially to the structure and dynamics of ocean food webs, as seen in arctic near-shore ecosystems and in those of the vast abyssal plains on continental margins in the oceans. The complex interplay of top-down and bottom-up forces is only beginning to be revealed by ecological science in the open ocean at a time when heavy fishing is beginning to alter these systems. Schematic view of top-down control of phytoplankton abundance in eutrophic lakes. Effect of manipulation of zooplanktivorous fish biomass (left) as compared to an unmanipulated food web.Scientific background. Food webs are either regulated by resources (‘bottom-up’) or by predation (‘top-down’). A strong reduction of the biomass of zooplanktivorous fish such as roach ( Rutilus rutilus L.) is often followed by an increase in the abundance and size of zooplankton (predominantly Daphnia species).
This increases the grazing pressure on phytoplankton and potentially leads to the top-down control of phytoplankton biomass, in which case the water becomes clear and extreme values of oxygen and pH are avoided ( Figure 9). A reduced biomass of planktivorous fish may also reduce nutrient recycling rates. The success of food web manipulation may therefore also be triggered by bottom-up forces. Benthivorous fish such as bream ( Abramis brama L.) or common carp ( Cyprinus carpio L.) exert bottom-up effects on water quality as they increase sediment resuspension, water turbidity, and internal nutrient loading. The removal of benthivorous fish may therefore also strongly determine the success of a food web manipulation. Top-down control of phytoplankton biomass was found to occur in shallow lakes and in deep lakes of slightly eutrophic or mesotrophic state.
It is unlikely in eutrophic or hypertrophic deep lakes. The substantially higher success rates of food web manipulations in shallow – as opposed to stratified – lakes can be attributed to positive feedback mechanisms triggered by the recovery of submerged macrophytes ( Figure 2).Techniques. A reduction of the biomass of zooplanktivorous and benthivorous fish can be reached by stocking with piscivorous fish such as pike ( Esox lucius L.), pike-perch ( Sander lucioperca L.), or perch ( Perca fluviatilis L.). A direct reduction can also be achieved by poisoning, fish removal by conventional fishery techniques, or a temporary drainage of the lake. An appropriate balance between piscivorous, planktivorous, and benthivorous fishes is required for long-lasting success of food web manipulations. The average success rate is 60%.
Strongest effects of food web manipulations are predicted when both fish and nutrients are altered. Experience has shown that lake water quality can only be improved by food web manipulation if annual loading is lower than 0.6–0.8 g of total P m −2 of lake surface area, or the in-lake P concentration is lower than 100 μg l −1 in shallow lakes. The complexity of lake food webs, however, makes scientifically sound predictions of success rather difficult.
Gobas, in, 2008Food-web bioaccumulation models are scientific instruments that describe much of our current understanding of the relationship between chemical concentrations in abiotic media (such as water, sediments, soils, and air) and biological organisms of food webs. They can be used to assess the ecotoxicological risks of chemical contamination and to develop clean-up and remediation goals for contaminated ecosystems that meet expectations of ‘acceptable’ risk. To advance the models and to apply the models in a responsible fashion, it is important to be familiar with the main principles included in the modeling philosophy and to recognize the strengths and limitations of the application of the model. This article provides a summary of the key principles of current food-web bioaccumulation models for organic compounds and discusses the application of the model to conduct ecotoxicological risk assessments for contaminants.
Directions for further reading and access to some current models are also presented. Dodds, Matt R. Whiles, in, 2010 Theoretical Community Ecology and Aquatic Food WebsLake food webs are well characterized and have been analyzed by theoretical community ecologists in attempts to describe general patterns ( Pimm, 1982). General questions that have been asked include the following: What limits the length of food chains? Are complex systems more or less stable? How interconnected are large food webs?
Does aggregation of species into trophic groups alter the results obtained from analyses of food webs? How variable are food webs over space and time? Can state changes (regime shifts) be predicted?It is not clear what limits the lengths of aquatic food chains.
The length of the food chain is of particular importance when determining biomagnification of lipid-soluble pollutants. General analyses suggest that the amount of primary production at the base of the food chain is not a good indicator of food chain length (Briand and Cohen, 1990); but these analyses are not necessarily consistent with the idea that energy is lost at each tropic level. However, at least one study suggests that trophic transfer of energy in the Okefenokee Swamp may be very efficient (Patten, 1993), so our concepts of food web efficiency and how it should link to the number of trophic levels may need to accommodate situations with high energy transfer efficiencies.
Groundwaters in which the number of large animals is physically limited by their ability to move through aquifers typically have short food chains. Marine pelagic food chains are considerably longer than most pelagic freshwater chains. It has been suggested that stream food webs tend to be short but wider relative to those of lakes (i.e., with more species as primary consumers). Large rivers and lakes tend to have similar food web structure ( Briand, 1985). Movement of energy in freshwater ecosystems will be discussed in more detail in Chapter 24.The relationship between food web stability and complexity is also unclear.
Early ecologists viewed simple systems as less stable ( MacArthur, 1955; Elton, 1958). Mathematical analyses of simple linear models of randomly assembled “communities” then suggested decreased stability with more interacting species ( May, 1972).
Since then, empirical ( Frank and McNaughton, 1991) and modeling ( Dodds and Henebry, 1996) approaches have suggested that increased diversity begets greater stability. We are not aware of any data from aquatic systems that can resolve the controversy regarding food web complexity and stability.The degree of connectivity (the number of links per species) and how it changes with community size are also controversial. It has been suggested that connectivity increases as food webs become more complex (Havens, 1992), but this analysis is controversial ( Martinez, 1993; Havens, 1993). Interesting results have been obtained that indicate that the proportion of species in each trophic category does not change with food web size (Havens, 1992).
However, even this idea of constant proportions of species at each trophic level independent of food web size has been demonstrated to be false in one stream community ( Tavares-Cromar and Williams, 1996). As a convenience, scientists conducting community analyses of food webs lump organisms into trophic categories. For example, in benthic food webs, one of the primary food sources is often detritus. In reality, detritus is a complex microbial and invertebrate community associated with decaying organic material. Analysis of a highly resolved food web from Little Rock Lake, Wisconsin ( Fig 22.8), suggests that lumping or aggregation of food webs into functional groups strongly influences properties such as the proportion of species at each trophic level and the connectivity of the food webs ( Martinez, 1991).
The food web of Little Rock Lake as described by Martinez (1991). Producers are on the bottom ring, consumers above. Species are indicated by the balls, and the sticks connecting the balls indicate which species below are being eaten. Note some of the consumers have loops to themselves representing cannibalism.
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(Image produced with FoodWeb3D, written by R.J. Williams and provided by the Pacific Ecoinformatics and Computational Ecology Lab; www.foodwebs.org; Yoon et al., 2004).Food webs can have variable structure over space and time. Descriptive characteristics of a detritus-based food web varied over time where the food web was more or less complex across seasons depending on the life cycle of the benthic invertebrates ( Tavares-Cromar and Williams, 1996).
Temporal variation in stream food webs has been linked to seasonal hydraulic cycles ( Power et al., 1995). Spatial variation also has clear effects, and benthic and pelagic food webs in lakes are distinct ( Havens et al., 1996a), pools and riffles in streams contain different organisms, and there are strong effects of water depth on species composition in wetlands.
The Encyclopedia of Food Sciences and Nutrition, Second Edition is an extensively revised, expanded and updated version of the successful eight-volume Encyclopedia of Food Science, Food Technology and Nutrition (1993).Comprising ten volumes, this new edition provides a comprehensive coverage of the fields of food science, food technology, and nutrition. Every article is thorough in its coverage, the writing is succinct and straightforward, and the work presents the reader with the best available summary and conclusions on each topic. Easy to use, meticulously organized, and written from a truly international perspective, the Encyclopedia is an invaluable reference tool. An essential item on the bookshelf for every scientist or writer working in the fields of food and nutrition. Key Features.
Caballero is Professor of International Health at the Bloomberg School of Public Health, and Professor of Pediatrics at the School of Medicine, Johns Hopkins University. He has over 20 years of experience as a scholar, researcher and leader in the area of child health and nutrition. He obtained his MD from the University of Buenos Aires and his PhD (in neuroendocrine regulation) from MIT. He started his faculty career at Harvard Medical School, and moved to Johns Hopkins in 1990 to found the Center for Human Nutrition.Dr. Caballero is a recognized expert on the nutritional needs of children and adults, and on nutrient requirements in undernourished populations. For the past 10 years, he has focused on the problem of childhood obesity in the US and in developing countries, and explored the impact of dietary transition and globalization on health indicators. He is an active participant in key scientific committees advising the US government on issues of diet and health, including the Dietary Reference Intakes (DRI) Committee, the Expert Panel on Macronutrient Requirements, and the Food and Nutrition Board of the Institute of Medicine, National Academy of Sciences.
He was a member of the Dietary Guidelines for Americans Advisory Committee, and is currently a member of the Scientific Advisory Board of the Food and Drug Administration (FDA) and of the International Life Sciences Institute (ILSI).Dr. Caballero is an active leader in the area of global health, specifically on diet, lifestyle and disease risk. He is Chairman of the Board of the Pan American Health and Education Foundation, in Washington, D.C., and member of the Board of Directors of the International Nutrition Foundation, in Boston, MA. He is a member of the Steering Committee of the Centers of Excellence Network of the Global Health Initiative, National Institutes of Health. Recent awards include the Ancel Keys Prize for achievements in international public health and the Thompson-Beaudette Lectureship from Rutgers University. In 2011 he was named to the Spanish Academy of Nutritional Sciences.Dr. Caballero is the author of over 150 scientific publications.
He is the Editor-in-Chief of the Encyclopedia of Food Sciences and Nutrition, a 10-volume work on food production, consumption and biological effects. He is also Editor-in-Chief of the Encyclopedia of Human Nutrition, which received the Book of the Year Award from the British Medical Association. His Guide to Dietary Supplements summarizes the current scientific basis for the use of mineral and vitamin supplements. His book The Nutrition Transition: Diet and Disease in the Developing World explored the impact of demographic and economic development on diet- and lifestyle-related diseases in developing countries. His book Obesity in China summarizes research conducted in rural and urban China to track the impact of socioeconomic development on health outcomes. He is also co-editor of the most widely used textbook in human nutrition, Modern Nutrition in Health and Disease.
Fidel Toldra holds a PhD in Chemistry (1984) and is Research Professor at the Instituto de Agroquimica y Tecnologia de Alimentos (CSIC) located in Paterna (Valencia, Spain) where he leaders the group on Biochemistry, technology and innovation of meat and meat products. He was a Fulbright postdoctoral scholar at Purdue University (West Lafayette, Indiana, 1985-86) and visiting scientist at the University of Wisconsin (Madison, Wisconsin, 1991 and 1995), and the Institute of Food Research (Bristol, UK, 1987). Toldra has filed 11 patents, published over 285 manuscripts in scientific journals and 125 chapters of books.
He holds in 2017 an h index of 49.His research interests are focused on food biochemistry and the development of new analytical methodologies, focusing on the improvement of quality, safety, nutrition and health of foods of animal origin, especially meat and meat products.Prof. Toldra is the European Editor of Trends in Food Science and Technology (2005-current) and Associate Editor of Meat Science (2014-current); he was Editor-in-Chief of Current Nutrition & Food Science and section Editor of the Journal of Muscle Foods. He is a member of the Editorial Boards of Food Chemistry, Current Opinion in Food Science, Journal of Food Engineering, Food Analytical Methods, Journal of Food and Nutrition Research, Recent Patents in Agriculture, Food and Nutrition, The Open Nutrition Journal, Food Science & Nutrition, International Journal of Molecular Sciences and Food Science & Human Wellness. He has edited/Co-edited more than 40 books for known publishers (CRC Press, Springer, Wiley-Blackwell, Academic Press and Elsevier). He is one of the 3 Editors-in-Chief of the Encyclopedia of Food and Health, published in September 2015 by Academic Press/Elsevier.Prof. Toldra has received the Iber Award on Food and Cardiovascular Diseases, the 2001 Danone Institute Award in Food, Nutrition and Health, the 2002 International Prize for Meat Science and Technology given by the International Meat Secretariat, the 2002 GEA award on R+D activity in agro-food, the 2010 Distinguished Research Award and the 2014 Meat processing Award, both of the American Meat Science Association and the 2015 Dupont Science Award. He is a Fellow of the International Academy of Food Science and Technology (IAFOST) and a Fellow of the Institute of Food Technologists (IFT).Prof.
Toldra served at Panels on Food Additives and on Flavorings, enzymes, processing aids and food contact materials of the European Food Safety Authority (EFSA, 2003-15) and Chairman of the Working groups on Irradiation (2009-10), Processing Aids (2011-14) and Enzymes (2010-15). In 2008-09 he joined the FAO/WHO group of experts to evaluate chlorine-based disinfectants in the processing of foods.
PRAISE FOR THE FIRT EDITION:'There is new material and updated material that makes the second edition a useful replacement for the first edition.Recommended, possibly for high school, but definitely for college/university libraries.' - E-STREAMS (April 2005)'This Encyclopedia includes over 1,000 articles covering all areas of food science and nutrition.' -CAB Abstracts 2004'This is my 125th book review for FOOD TECHNOLOGY and this is indeed the jewel in the crown, the biggest and best work I've commented on so far.Frankly, I'm impressed. I could not find a concept or word that was not listed.' -Manfred Kroger, Penn State University in FOOD TECHNOLOGY'.this is an excellent reference work, comprehensive and comprehensible.a work to be recommended'-FOOD CHEMISTRY'.with almost 5,000 pages of text it is hard not to find what you want in this absolutely brilliant encyclopaedia.'
-BRITISH NUTRITION FOUNDATION.