Managing Wastewater in Coastal Urban Areas (1993) / Chapter Skim
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A THE ROLE OF NUTRIENTS IN COASTAL WATERS
A THE ROLE OF NUTRIENTS IN COASTAL WATERS
Pages 177-202
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From page 177... ...
Coastal waters receive large amounts of nutrients from wastewater treatment plants and nonpoint sources. In particular, estuaries receive more nutrient inputs per unit surface area than any other type of ecosystem.
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From page 178... ...
This section first briefly discusses the negative effects of eutrophication and nuisance algal blooms in coastal marine ecosystems. It then reviews in more detail the controls on eutrophication; discusses the issue of whether nitrogen or phosphorus is more limiting to eutrophication; presents doseresponse information, which relates nitrogen to algal biomass and production; and reviews the information on controls of nuisance algal blooms.
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From page 179... ...
Of more concern in most estuaries and coastal marine ecosystems is the oxygen consumption that results from the decomposition of the excess phytoplankton production characteristic of eutrophication (Officer et al. 1984, Larsson et al.
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From page 180... ...
1991) , although the occurrence of unusual nuisance algal blooms in 1985 and 1986 greatly reduced the abundance of seagrass beds near Long Island (Dennison et al.
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From page 181... ...
Nuisance Algal Blooms Blooms of nuisance algae are characterized by very high abundances of one overwhelmingly dominant species in the phytoplankton. These blooms often result in noticeable color and are popularly named by this color: red tides, green tides, and brown tides.
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From page 182... ...
CONTROLS ON EUTROPHICATION AND NUISANCE BLOOMS IN COASTAL WATERS Nutrient Limitation Nutrients are elements essential for plant growth, such as nitrogen, phosphorus, silica, and sulfur. Phytoplankton production in most coastal marine ecosystems and estuaries is nutrient limited, and increased nutrient inputs lead to higher production and eutrophication (Ryther and Dunstan 1971; Graneli 1978, 1981, 1984; McComb et al.
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From page 183... ...
Nitrogen Versus Phosphorus Limitation Nitrogen is the element usually limiting to primary production by phytoplankton in most estuaries and coastal seas of the temperate zone (Ryther and Dunstan 1971; Vince and Valiela 1973; Smayda 1974; Norin 1977; Graneli 1978, 1981, 1984; Boynton et al. 1982; Nixon and Pilson 1983; Valiela 1984; D'Elia et al.
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From page 184... ...
Kaneohe Bay23078 Long Island Sound40067 Chesapeake Bay51033 Apalachicola Bay5602 Barataria Bay570<1 Patuxent Estuary60048 Potomac Estuary81048 Pamlico Estuary860<1 Narragansett Bay95041 Mobile Bay1,2807 Delaware Bay1,30050 Raritan Bay1,46086 South San Francisco Bay1,600~100 North San Francisco Bay2,01045 New York Bay31,90082 various estuaries and may be a more controllable input than those from agriculture and other nonpoint sources (Table A.1, Nixon and Pilson 1983~. That nitrogen limits primary production in most temperate-zone estuaries and coastal seas was much debated throughout the 1980s (D'Elia 1987, Howarth 1988, Nixon 1992~.
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From page 185... ...
What differences in biogeochemical cycles lead toward nitrogen limitation in temperate coastal marine ecosystems and toward phosphorus limitation in temperate lakes? At least three factors appear important (Figure A.1~: the ratio of nitrogen to phosphorus in nutrient inputs to estuaries is 1 Ni trogen Fixation ?
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From page 186... ...
estuaries and coastal seas are below this ratio, while nutrient inputs to temperate lakes tend to have higher N:P ratios (Jaworski 1981, Kelly and Levin 1986, NOAA/EPA 19881. This difference in ratios probably reflects the relative importance of sewage, which tends to have a low N:P ratio, as a nutrient source to coastal waters.
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From page 187... ...
1987, Paerl and Carlton 1988~; greater grazing pressure on cyanobacteria in marine systems (Vitousek and Howarth 1991~; and a lower light availability in estuaries and coastal waters due to higher turbidity and/or deeper mixed layers (Howarth and Marino 1990, Vitousek and Howarth 1991~. As noted above, many tropical estuaries and coastal systems may be phosphorus limited (Smith 1984, Smith and Atkinson 1984~.
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From page 188... ...
_ 8. ·9 .10 13 · ·11 S 14 12 1 1 1 1 1 0 10 20 30 40 50 Nitrogen Loading, g N m~2 yr~1 FIGURE A.2a Regression plot relating nitrogen loadings to annual phytoplankton production in a variety of estuarine ecosystems: 1, Chesapeake Bay, 2)
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From page 189... ...
are also correlated with inputs of dissolved inorganic nitrogen to various estuarine and coastal marine ecosystems (Nixon and Pilson 19831. Figure A.4a shows the relationship between annual inputs of dissolved inorganic nitrogen per unit volume and the average annual abundance of chlorophyll for a variety of estuaries.
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From page 190... ...
~3 64 ·. 8 9 · .7 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1o2 1 1 1 1 1 1 1 1 10 103 DIN Input, m mol m~3 y~1 104 FIGURE A.3 Annual measurements of primary production as a function of the estimated annual input of dissolved inorganic nitrogen (DIN)
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From page 191... ...
Q v __ T - , ~. 1 1 1 I: FIGURE A.4a Annual average concentration of chlorophyll compared to inorganic nitrogen inputs in a variety of natural estuaries and in experimental mesocosms at the Marine Ecosystem Research Laboratory, University of Rhode Island.
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From page 192... ...
Note that numerical models of the Chesapeake Bay suggest that current nitrogen loadings need to be reduced by 40 percent to eliminate anoxia there (Butt 1992~; this reduction corresponds to a decrease in nitrogen inputs from 510 mmol m~2 yearn (Nixon and Pilson 1983, and TableA.l) to some 300 mmol m~2 yearn or within the range suggested by Jaworski (1981)
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From page 193... ...
, and the reduction of nutrient loadings and the opening of a channel to increase water exchange between the bay and ocean have greatly reduced these blooms (Ryther 1989~. Also, nuisance algal blooms are much more likely to occur in nutrient-rich estuarine waters than in more coastal or shelf waters (Cosper 1991, Prego 1992~.
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From page 194... ...
In many temperate estuaries and coastal seas, nitrogen is the primary nutrient of concern leading to increased eutrophication. Phosphorus controls eutrophication in some coastal marine ecosystems, at least during some seasons, and may be the primarily controlling element in tropical seas.
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From page 195... ...
1989. Toxic algal blooms and red tides: A global perspective.
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From page 196... ...
1987. Recurrent and persistent "brown tide" blooms perturb coastal marine ecosystem.
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From page 197... ...
1990. Nutrient limitation of primary production in the Baltic Sea area.
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From page 198... ...
1983. The decline of submerged vascular plants in upper Chesapeake Bay: Summary of results concerning possible causes.
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From page 199... ...
1983. Nitrogen in estuarine and coastal marine ecosystems.
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From page 200... ...
1987. Limitation of N2 fixation in coastal marine waters: Relative importance of molybdenum, iron, phosphorous, and organic matter availability.
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From page 201... ...
In Novel Phytoplankton Blooms: Causes and Impacts of Recurrent Brown Tides and Other Unusual Blooms. Lecture Notes on Coastal and Estuarine Studies, E.M.
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From page 202... ...
Bascom, ed. Long Beach, CA: Southern California Coastal Water Research Project.
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