FIGURE 3.1 Bacterial decomposition of organic matter in marine/estuarine sediments through a...

FIGURE 3.1 Bacterial decomposition of organic matter in marine/estuarine sediments through a sequence of terminal electron acceptors (e.g., O2, NO3

¯, MnO2, FeOOH, SO4¯, and CO2) and changing redox.

Source: Modified from Deming and Baross (1993).

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 3.2 Illustration of the simplest distribution pattern, in a one-dimensional, two end-member, steady-state system for a conservative constituent to change linearly with salinity. Source: From Wen et al. (1999).


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FIGURE 3.3 Processes critical in controlling the partitioning of chemical species in estuaries with particular emphasis on metals and hydrophobic organic micropollutants (HOMs). Source: Modified from Turner and Millward (2002).


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FIGURE 3.4 Conventional definition for dissolved materials shown as the fraction of total material that passes through a membrane filter with a nominal pore size of 0.45 μm. Source: From Wen et al. (1999).


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FIGURE 3.5 The most common kinetic model used to estimate rates of gas exchange across the atmosphere–water boundary is the stagnant film model. This model essentially has the following three regions of importance: (i) a well-mixed turbulent atmospheric zone (PG), (ii) a well-mixed thin-film liquid zone (PG), and (iii) a laminar zone (a and b) separating the two turbulent regions. The thin film is considered permanent with a thickness defined as z. Source: From Broecker and Peng (1974).


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FIGURE 3.6 A conceptual diagram showing that while the ETM roughly tracks the limit of salt, it was often decoupled from the salt front (defined here at the isohaline with a salinity of 1), due to a lag of ETM sediment resuspension/ transport from rapid meteorologically driven movement of the salt front. Source: From Sanford et al. (2001) with permission.


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FIGURE 3.7 Major sources of dissolved organic matter (DOM) to estuaries, primarily comprise riverine inputs, autochthonous production from algal and vascular plant sources, benthic fluxes, groundwater inputs, and exchange with adjacent coastal systems. Source: Modified from Hansell and Carlson (2002).


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FIGURE 3.8 Percent organic matter remaining during a 23-month decay experiment with S. alterniflora detritus. Source: Modified from Wilson et al. (1986).


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FIGURE 3.9 Pathways of the sum of all biochemical processes is called metabolism. It is differentiated as primary and secondary metabolism. Primary metabolism contains all pathways necessary to keep the cell alive,whereas in secondary metabolism, compounds are produced and broken down that are essential for the entire organism.


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FIGURE 3.10 Schematic of nitrogen sources and cycling in estuaries. These sources include a diverse group of diffuse point and nonpoint agricultural, urban, and rural sources (e.g., wastewater, industrial discharges, stormwater, and overflow discharges) across a broad spectrum of watersheds (e.g., urban, agricultural, and upland and lowland forests. Source: Modified from Paerl et al. (2002).


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FIGURE 3.11 Major processes involved in the biogeochemical cycling of N in estuaries and the coastal ocean: (i) biological N2-fixation (BNF), (ii) ammonia assimilation, (iii) nitrification, (iv) assimilatory NO3

¯reduction, (v) ammonification or N-remineralization, (vi) ammonium oxidation (speculative at this time), (vii) denitrification and dissimilatory NO3

¯reduction to NH4+, and (viii) assimilation of dissolved organic

nitrogen (DON). Source: Modified from Libes (1992).


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FIGURE 3.12 Fraction (%) of total N input from land and atmosphere that is denitrified in different estuaries as a function of residence time (months). Source: Modified from Nixon et al. (1996).


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FIGURE 3.13 Major pathways of the N cycle in sediments (a) and as a function of redox conditions in bottom waters and sediments (b). Both diffusive and advective processes strongly control the distribution of O and N compounds, which ultimately affect the coupling between nitrification and denitrification. Source: Modified from Jørgensen and Boudreau (2001).


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FIGURE 3.14 Relative abundance of these different dissolved inorganic P compounds as a function of pH in aquatic systems; H2PO4

¯ and HPO42¯ are the more common species in freshwater and seawater,

respectively. Source: Modified from Morel (1983).


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FIGURE 3.15 Negative correlations between dissolved inorganic phosphorus (μM) and oxygen (ml/l) concentrations in bottom waters of the Baltic Sea. Source: Modified from Conley (2002).


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FIGURE 3.16 Temporal variability of concentrations of DSi (μM) in Chesapeake Bay across a salinity gradient. Source: Modified from Conley and Malone (1992).


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FIGURE 3.17 Depth profile of the microzone of O2 and H2S at the sediment–water interface (ca. 1-2 mm) where Beggiatoa spp. and Thiovulum spp. thrive. Source: Modified from Jørgensen and Revsbech (1983).


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FIGURE 3.18 Percent particulate organic carbon (POC) and total suspended particulates (TSP) in the water column from three regions of the Sabine-Neches estuary, sampled from March 1992 to October 1993. Source: Modified from Bianchi et al. (1997).


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FIGURE 3.19 Concentrations of dissolved organic carbon (DOC) across a salinity gradient in six Texas estuaries in August and October. Source: Modified from Benoit et al. (1994).


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FIGURE 3.20 Down-core profiles of porewater dissolved organic carbon (DOC), C:N ratios, and total CO2 at three stations in Chesapeake Bay. Source: Modified from Burdige and Zheng (1998).


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FIGURE 3.1 Bacterial decomposition of organic matter in marine/estuarine sediments through a...

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