FIGURE 16.1 A simple food chain with three trophic levels illustrated using energy systems language...

FIGURE 16.1 A simple food chain with three trophic levels illustrated using energy systems language (e.g., Odum, 967; Odum, 1971). Arrows indicate transfer of matter or energy. Circles indicate inputs, which could include matter, such or nutrients, or energy. A ‘‘bullet’’ symbol indicates a primary producer, whereas hexagons indicate consumers. Horizontal lines (i.e., electrical ‘‘ground’’ symbols) indicate energy dissipation or recycling.

ESTUARINE ECOLOGY, Second Edition. John W. Day JR, Byron C. Crump, W. Michael Kemp, and Alejandro Yánez-Arancibia. Copyright © 2013 by Wiley-Blackwell. All rights reserved

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FIGURE 16.2 Energy flow in the North Sea food web (Steele, 1974) illustrating the complexity of a more realistic, but still simple, food web aggregated by ecological function rather than taxonomy. Some predators (e.g., demersal fish) consume prey from several prey groups. Similarly, some groups (e.g., pelagic herbivores, macrobenthos) are consumed by several different consumers. Source: Redrawn based on Ulanowicz and Kemp (1979).


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FIGURE 16.3 Estuarine species belonging to several trophic guilds. (a) The polychaete worm Nereis succinea is a generalist benthic deposit feeder that consumes small organisms near the sediment surface. (b) Bay anchovy (Anchoa mitchilli) is a small planktivore. (c) Atlantic menhaden (Brevoortia tyrannus) is a suspension feeding fish that consumes plankton. (d) The blue crab (Callinectes sapidus) is a benthic predator.


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FIGURE 16.4 A small purse seine vessel encircled a school of Gulf menhaden (Brevoortia patronus) near Pascagoula, Mississippi in June 1968. Source: Photo by R. K. Brigham, US National Oceanic and Atmospheric Administration.


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FIGURE 16.5 Ecological trophic pyramids of biomass and energy flow (i.e., production at each trophic level). P = primary producers, C1 = first consumers (herbivores), C2 = second consumers (first carnivores), S = saprotrophs (detritivores, feeding on detritus or dead organic matter). Note the convention of placing primary producers as the bottom block of the pyramid and top carnivores as the highest block. Source: Redrawn from Odum (1971).


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FIGURE 16.6 The effective food chain for the North Sea food web network (Steele, 1974) depicted in Figure 16.2. Flows, which in this case are energy flows in kilocalories per square meter per year, are apportioned to integer trophic levels following the method of Ulanowicz and Kemp (1979). Flows from an integer trophic level to the next indicate upward transfer of energy within the food web.Flows to ‘‘ground’’ are defined as in Figure 16.1, where respiration is combined with flows to detritus and loss from the food web. Additional flows can be included in the effective food chain to explicitly represent the return of detritus to the food web. Upward arrows represent the yield to humans at each effective trophic level. Not surprisingly, the largest yield to humans occurs via the shortest and most efficient trophic pathway (boxes 1–3), which in this example is primary producers→pelagic herbivores→pelagic fish (Fig. 16.2).


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FIGURE 16.7 Trophic spectra for the most important consumer species of Lake Pontchartrain, indicating the feeding habits of each of the consumer species listed across the top. As an example, the bivalve Rangia cuneata, in the first column, largely consumes organic detritus, plus some phytoplankton. In contrast, Caranx hippos, a marine fish in the jack family, consumes fish almost exclusively. Micropogonias undulatus, or Atlantic croaker, has more varied food habits than either of these species, consuming a mixture of fish, small benthic (‘‘bottom’’) animals, zooplankton, and organic detritus. Source: Redrawn from Darnell (1961).


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FIGURE 16.8 A normalized biomass size spectrum for fish captured in the Chesapeake Bay. The graph depicts the abundance of fish within size ranges normalized by the width of the size range. The normalized spectrum is characterized as having two distinct trophic groups,which appear as ‘‘domes.’’ The first dome corresponds to bay anchovy (Anchoa mitchilli), the dominant zooplanktivore, and the second dome corresponds to the larger piscivores such as striped bass (Morone saxatilis). Bay anchovy account for a significant fraction of the diet of the piscivores. Source: Redrawn from Jung and Houde (2005).


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FIGURE 16.9 The cnidarian Chrysaora quinquecirrha occurs in many estuaries. Source: Photo by Anastasia Shesterinina.


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FIGURE 16.10 Mechanisms of trophic transfers from seagrass meadows to adjacent coastal habitats in (a) tropical and (b) temperate regions. Source: Modified from Heck et al. (2008).


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FIGURE 16.11 Relationship between log(body size at maturity) and log(P/B) (annual production/biomass) for a variety of functional groups of species. The equation for the solid regression line is log(P/B) = −0.19−0.27 log(M). Dashed lines indicate 50% and 200% of the predicted P/B. Body size is converted to energy content (i.e., caloric) equivalents. The relationship spans 5 orders of magnitude in body size.MR refers to the mean range in P/B for 16 species with multiple observations. Source: Redrawn from Banse and Mosher (1980).


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FIGURE 16.12 Results of an experiment following incorporation of lipid biomarkers in a food chain. In each of the three treatments, North Sea cod larvae were fed copepod nauplii hatched from adult copepods raised on (i) the diatom Skeletonema costatum, (ii) the flagellate Heterocapsa triquetra, or (iii) a 50 : 50 mixture of each. The lipid tracer index is the ratio of abundance in the cod larvae of two specific lipid markers. Source: Modified from St. John and Lund (1996).


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FIGURE 16.13 Graph illustrating the use of stable nitrogen and sulfur data from biota collected near Sapelo Island, Georgia, to evaluate the organic matter sources for the food web. In this case, stable isotope data exclude upland plants as an important source of the food web. Source: Redrawn from Peterson and Howarth (1987).


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FIGURE 16.14 The relationship between 15N and trophic level in the food web of Georges Bank. Later research revealed that the ‘‘piscivore’’ with particularly low 15N consumes lower trophic level prey, consistent with the stable isotope results. POM, particulate organic matter. Source: Redrawn from Fry (1988).


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FIGURE 16.15 A simple hypothetical carbon food web for an estuary. Inputs, outputs, respirations, and internal flows have units of grams of carbon per square meter per year. Major components are primary producers (e.g., phytoplankton), grazers (e.g., copepods) feeding on a mixture of phytoplankton and heterotrophic microplankton, carnivores (organisms feeding on zooplankton or small benthic species) and detritivores. Bacteria are represented as a subcomponent of the detritus pool, returning biomass produced back to detritus.


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FIGURE 16.16 The effective food chain obtained by projecting the food web in Fig. 16.15 into a chain of ‘‘canonical trophic levels.’’ Flows to detritus are collected in a detritus compartment (labeled ‘‘D’’) and assigned a trophic level of 1. Exports from trophic level 3 and 4 total to 15, the export from compartment 3 (carnivores), revealing the ‘‘apportionment’’ of activity between trophic level 3 and 4. The effective trophic level for carnivores is 3.13 because most of the export is at trophic level 3.


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FIGURE 16.1 A simple food chain with three trophic levels illustrated using energy systems language...

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