FIGURE 5.1 Examples of submersed vascular plants that occur in estuarine systems: (a) Myriophyllum
spicatum (photo: O. Pedersen), (b) Stuckenia pectinata (photo: O. Pedersen), and (c) Vallisneria americana
(photo: Seafavorites.com) are freshwater plants that are able to tolerate low salinities (<15), while (d)
Thalassia testudinum (photo: O. Pedersen), (e) Zostera marina (photo: P.B. Christensen; NERI), and (f)
Halophila ovalis (photo: P. Lavery) are seagrasses that thrive in full-strength seawater.
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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
FIGURE 5.2 One of the most serious physiological challenges for submersed vascular plants is to supply
rhizomes and roots with sufficient oxygen to support aerobic metabolism and prevent invasion of anaerobic
metabolites from the sediment. The figure shows how internal plant oxygen and gaseous sulfide, measured
with microelectrodes, interact over a diel cycle in a T. testudinum bed in Florida Bay, USA, during a seagrass
die-off period. The oxygen within the plant meristem changed from supersaturation (i.e., above the oxygen
partial pressure of the atmosphere indicated by the stippled line) during daytime to very low levels at night,
when water column oxygen content was low. When plant oxygen is low, poisonous sulfide can invade from
the sediment into the plant as seen shortly after midnight on this occasion. Source: Redrawn after Borum et
al. (2005).
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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
FIGURE 5.3 The probability of finding eelgrass at a cover (in % of bottom area) of greater than 0, greater
than 2, greater than 25, greater than 50 and, greater than 75% at different depth intervals and as functions of
light availability (in % of surface photon flux density, PFD), wave exposure (in relative units determined by
fetch, wind direction and velocity, and water depth; Krause-Jensen et al., 2003) and salinity.
Source:
Redrawn after Krause-Jensen et al. (2003).
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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
FIGURE 5.4 Frequency distribution of biomass and production compiled for a large number of seagrass
species. Redrawn after Duarte and Chiscano (1999).
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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
FIGURE 5.5 Colonization depth for seagrass communities distributed worldwide versus light attenuation
coefficient reflecting water turbidity. The relationship is described by the equation log(Zc) = 0.26 – 1.07 · log(k),
where Zc is the colonization depth and k is the light attenuation coefficient. Redrawn after Duarte (1991).
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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
FIGURE 5.6 Temperature dependency of light saturated net photosynthesis for eelgrass collected in winter
(February), spring (April), and late summer (August). Optimum temperature for light saturated net
photosynthesis varied from 20 to 25°C depending on the season. Source: Redrawn after Staehr and Borum
(2011).
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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
FIGURE 5.7 Net photosynthetic rates relative to maximum net photosynthesis of two macroalgae species:
Ulva lactuca and Saccharina latissima (formerly Laminaria saccharina) and two seagrass species:
T. testudinum and Z. marina at normal seawater pH but varying availability of inorganic carbon (DIC in mM).
Normal (1) and double (2) seawater DIC levels are indicated on the x-axis. Redrawn after Beer and Koch
(1996).
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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
FIGURE 5.8 Ratio between current velocity measured inside and outside an eelgrass bed during periods
with different aboveground biomass. The ratio between current velocities clearly declined with increasing
biomass, reflecting the damping effect of the canopy. Redrawn after Hasegawa et al. (2008).
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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
FIGURE 5.9 Maps of (a) turbidity and (b) oxygen saturation created from measurements across and outside
a robust bed of S. pectinata (sago pondweed) in Chesapeake Bay. The solid black line represents the
perimeter of the bed, while the dotted area represents land. Turbidity was measured in NTUs (nephalometric
turbidity units), a relative measure of underwater light transmission. The maps show a reduction in turbidity
and increase in oxygen saturation with distance into the plant stand, which reflects the substantial impact
submersed plant beds can have onwater quality in shallow environments. Source: Redrawn after Gruber and
Kemp (2011).
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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
FIGURE 5.10 Sediment profiles of dissolved ammonium in vegetated sites consisting of mixtures of
Z. marina and H. wrightii (closed circles) and unvegetated sites (open circles). Error bars are the standard
error. The higher level of porewater ammonium in the seagrass bed reflects the retention and recycling of
organic matter produced by the community or trapped from sources outside the plant bed. Source: Redrawn
after Kenworthy et al. (1982).
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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
FIGURE 5.11 The abundance of the diving duck, Redhead (in % of the total count for North American
breeding grounds), resting during winter in upper Chesapeake Bay versus the relative abundance of
submersed vascular plants at upper Bay sites. The number of resting Redheads correlated well with plant
abundance during the period from 1961 to 1975. With gradually decreasing plant abundance up through the
1960s and 1970s, Redhead abundance declined in this area and the ducks moved to areas with eelgrass
further south in Chesapeake Bay. Source: Redrawn after Kemp et al. (1984).
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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
FIGURE 5.12 Abundance (number of individuals per meter square) and species richness (number of
species) of finfish from May through September at an unvegetated and a vegetated site in the Choptank
River, Chesapeake Bay. In the vegetated area, finfish were more abundant and more species were found
compared to those in the unvegetated area, especially in August and September. Redrawn after Kemp et al.
(1984).
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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
FIGURE 5.13 Decadal trends in gains and losses of seagrass beds recorded world wide. (a) Decadal gains
and losses of area covered by seagrass and (b) number of sites where changes (decreasing, increasing, or
no change) have been recorded. The records show higher areal losses relative to gains and a relatively
larger number of sites exhibiting decreases than increases of seagrass area since the 1950s. Redrawn after
Waycott et al. (2009).
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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