Water Quality Criteria 

Report of the 

National Technical Advisory Committee 

to the 

Secretary of the Interior 

APRIL 1, 1968 

WASHINGTON, D.C. 

FEDERAL WATER POLLUTION CONTROL ADMINISTRATION 
able to survive lower salinities than can their 

predators and disease-causing organisms. Hence, 

in some tidal tributaries, oysters thrive in regions 

where they arc sheltered from these pests by low 

salinity. Natural alterations in salinity distribution 

have been reportedly followed by increased mortality of oysters. It is clear that care must be 

exercised in the approval of engineering projects 

or industrial processes that will alter salinity regimes in tidal tributaries and lagoons and in their 

associated wetlands. 

Salinity patterns can be caused to vary from 

"'normal" by alterations in character of freshwater 

inflow and basin geometry. These are the same 

factors that produce changes in circulation. In fact, 

salinity alterations are precursors to changes in 

density currents. 

Recommendation: For the protection of estuarine 

organisms, no changes in channels, in the basin geometry of the area, or in fresh water inflow should be 

made that would cause permanent changes in isohaline 

patterns of more than ± 10 percent of the natural 

variation. 

Currents 

Despite their large volumes, tidal waters, especially those in tributaries of the seas, have special 

circulatory characteristics that may affect their 

ability to assimilate wastes. For example, tidal action slows the already slowed (due to lowered 

slope and resulting reduced speed of gravity-induced flow) seaward movement of water in tidal 

rivers and streams. This alternate up and down 

stream movement of the water in the freshwater 

portion of the tidal tributary is confounding 

enough in itself (Ketchum, 1950 and 1951; Stommcl, 1 953a, b) but in the estuarine reach, the area 

where sea salts are noticeable, further complexities often occur (Bowden, 1963; Hargis, 1965; 

Redfield, 1951 ). In horizontally and vertically 

stratified mixing estuaries, there are two streams. 

The upper stream, fresher and lighter, has a netflow downstream while the lower stream, saltier 

· and heavier, flows inward or upstream. Since 

these surface currents and bottom counter-currents often extend far to sea off the mouths of 

large tidal tributary or estuarine systems, as well as 

far upstream, significant upstream transport of materials in solution or suspension in the countercurrent can occur. These circulatory features are 

important in the life cycles of many estuarine 

species. For example, oyster and barnacle setting is 

related to tidal and nontidal currents (Barlow, 

1955; Bousfield, 1955; Emery and Stevenson, 

1957; Hargis, 1966; Ketchum, 1954; Pritchard, 

1953). Large disturbances of current patterns can 

68 

disrupt the life cycles of estuarine organisms. 

Hence, projects that alter current patterns should 

be carefully evaluated and controlled. 

It is possible to alter circulatory patterns in tidal 

tributaries by ( 1 ) changing the quantity, timing, 

and location of fresh water inflow, (2) changing 

the geometry of the basin. The former can be accomplished by construction and operation of reservoirs above or below the fall line (defined as the 

uppermost limit of ocean's tidal activity). The 

latter can be accomplished by shoreline or bottom 

modification; e.g., drainage, bulkheading and filling, channel dredging, and subaqueous spoil disposal or mining. Oyster harvesting practices have 

been known to produce marked changes in bottom geometry (Hargis, 1966) . 

Recommendation: In view of the requirements of 

estuarine organisms and the nature of marine waters, 

no changes in basin geometry or fresh water inflow 

should be made in tidal tributaries which will alter 

current patterns in such a way ns to cause adverse 

effects. 

pH 

Despite the great emphasis given to the importance of pH in the literature, little is known of its 

direct physiological effects on marine organisms. 

Its indirect effects, however, are extremely significant. Even a slight change in pH indicates that 

the buffering system inherent in sea water has been 

altered radically and that either a potential or 

actual carbon dioxide imbalance exists. This imbalance can be deleterious or disastrous to marine 

life. A second indirect effect is that pH can influence the toxicity of other materials. Cyanide and 

ammonia, discussed under "Toxicity," are outstanding examples of this kind of action. 

Recommendation: Materials that extend normal ranges 

of pH at any location by more than ± 0.1 pH unit 

should not be int1'oduced into snit water portions of 

tidal tributaries or coastal waters. At no time should 

the introduction of foreign materials cause the pH to 

be less than 6.7 or greater than 8.5. 

Temperature 

Temperature requirements of marine and estuarine organisms in the biota of a given region may 

vary widely. Therefore, if we arc to maintain temperature favorable to the biota, all important species, including the most sensitive, must be protected. It has been found that organisms in the 

intertidal zone vary considerably in their ability 

to withstand high temperatures. Those in the uppermost areas of the tidal zone generally can with-

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portions of the tidal zone and these in tum generally can withstand higher temperatures than the 

same species of animals living in the subtidal 

zones. In addition, when considering the coastline 

as a whole, we must recognize that there are various races within a given species. which may vary 

considerably in their environmental requirements, 

or in their ability to withstand extreme conditions. 

In our marine waters, there is a great mixture 

of species. Species typical of higher latitudes are 

found with species that are more abundant farther 

south. Tropical or subtropical species generally 

will spawn in the summer months. Species from the 

higher latitudes require low water temperature for 

spawning and the development of the young. Thus, 

they usually spawn in the winter months and temperatures at that time are critical. Any warming of 

the water during the cold weather or winter period could be disastrous from the standpoint of the 

elimination of the more northerly species. In some 

instances, a rise in winter temperatures of only 2 

or 3 F might be sufficient to prevent spawning and 

thus eliminate these specie$ from the biota. 

In the northern portions of the country there is 

generally a great range in natural temperatures. In 

southern areas, as we approach the tropics, we find 

smaller overall temperature ranges. In the tropics 

or subtropics, optimum temperatures for many 

forms arc only a few degrees lower than maximum 

lethal temperatures. Great care should be exercised, therefore, to prevent harmful increases in 

maximum summer temperatures in tropical areas. 

In general, temperatures in the marine waters 

do not change as rapidly nor do they have the 

overall range from extreme to extreme as they do 

in fresh waters. Marine and estuarine fishes, therefore, are less tolerant of temperature variation. 

They can accommodate somewhat, but overall 

temperature range and rate of change arc even 

more important here than they are in fresh waters. 

It has been observed that when surface water temperatures over the Georges Bank increased from 

46 to 68 F, the larval fish died at 65 F. It has been 

found that species in subtropical and tropical environments are living at temperatures that are only 

a few degrees less than their lethal temperatures. 

In the most northern forms, extensive variations 

in seasonal temperatures are a necessity for orderly 

development and growth. Spawning and development frequently occur at lower temperatures and 

the sexual products ripen on rising temperatures 

after a period of low temperatures. Temperatures 

above or below the optimum range may delay or 

speed up development. They may inhibit swimming ability and the effectiveness of food utilization may be decreased with increasing temperatures in the upper viable range. Fishes and other 

forms are also more susceptible to parasites and 

diseases at temperatures outside of their optimum 

range. In regard to rapid changes in temperature, 

it has been found that a drop in temperature from 

58 to 43 F kills sardines. Tolerable temperature 

minima vary with the population and its past temperature history. Kills have occurred off the Texas 

coast at 40 F whereas kills of the same species 

have occurred off Bermuda at a drop to 59 F. 

Many kills have occurred in nature due to unusually low temperatures. Kills also occur due to 

natural high temperatures. Yellowtail flounder and 

whiting larvae died when they drifted from an area 

of 44 F to one of 64 F. It has been reported that 

61 F is best for the developing of mackerel, but 

70 F is too high. These are merely illustrations of 

what might happen to species occurring in inshore 

waters. , 

It is apparent from the foregoing that data are 

very sparse on temperature requirements of marine 

and estuarine species. It is very difficult, therefore, 

to attempt to suggest temperature requirements 

for marine and estuarine forms. The difficulty is 

compounded by the great extent of the Nation's 

shorelines, the differing natural temperature variations from north to south, and the geographic overlapping of species native to different latitudes. 

Consideration must be given to maximum allowable temperatures for both the summer period and 

the winter period. 

In attempting to establish permissible levels of 

temperature increase in receiving waters due to 

heated waste discharges, precaution must be tak·en 

to prevent-

(a) excessive incremental increases above 

background values even though such incremental increases lie below maximum 

limits, and 

(b) exceeding maximum natural background 

limits.. 

Such precautions are necessary to prevent gradual net increases in background temperatures due 

to the continuously increasing volumes of heated 

wastes being discharged into receiving waters. 

The discharge of heated wastes into estuaries 

and other tidal tributaries must be managed so that 

no barrier to the movement or migration of fish 

and other aquatic life is created. 

Recommendation: In view of the requirements lfor 

the well-being and production of marine organisms, it 

is concluded that the discharge of any heated waste 

into any coastal or estuarine waters should be closely 

managed. Monthly means of the maximum daily temperatures recorded at the site in question and before 

69 
the addition of any heat of artificial origin should not 

be raised by more than 4 F during the fall, winter, and 

spring (September through May), or by more than 

1.5 F during the summer (June through August). 

North of Long Island and in the waters of the Pacific 

Northwest (north of California), summer limits apply 

July through September, and fall, winter, and spring 

limits apply October through June. The rate of temperature change should not exceed 1 F per hour except 

when due to natural phenomena. 

Suggested temperatures are to prevail outside of 

established mixing zones as discussed in the section on 

zones of passage. 

Dissolved oxygen 

Dissolved oxygen requirements of marine organisms are not as well known as those for freshwater 

forms. Studies have been made indicating that 

minimum dissolved oxygen concentrations of 0.75 

to 2.5 a(e required for test species to resist death 

for 24 hours. Most marine species died when the 

dissolved oxygen dropped below 1.25 mg/ 1 for a 

few hours. Reduced swimming speed and· changes 

in blood and serum constituents occurred at dissolved oxygen levels of 2.5 to 3 mg/1. It was 

found that DO levels between 5.3 and 8 mg/ 1 were 

satisfactory for survival and growth. Levels above 

17 mg/1, however, produced adverse effects. Large 

fluctuations in dissolved oxygen from 3 to 8 mg/1, 

diurnal or otherwise, produced significantly more 

physiological stress in fishes than fluctuations from 

3 to 6 mg/1. In tests made to date, it has been 

found that 5 to 8 mg/1 of DO is apparently sufficient for all species of fish for good growth and 

general well being. It is generally recognized that 

in deeper waters DO values are often considerably 

less than 5.0 mg/ 1. In estuaries where there is a 

reduction in salinity, levels may drop to as low as 

4 mg/1 at infrequent intervals and for limited periods of time. It is probable that many marine animals can live for long periods of time at much 

lower levels of DO. Experimental studies with 

freshwater organisms . have demonstrated, however that low concentrations of DO at which adult 

fish;s can live almost indefinitely, can inhibit feeding and growth. In determining DO requirements, 

it is essential to consider growth, reproduction, 

and other necessary life activities. 

Recommendation: For the protection of marine rc· 

sources, it is essential that oxygen levels shall be sufficient for survival, growth, reproduction, the general 

well-being, and the production of a suitable crop. To 

attain this objective, it is recommended that dissolved 

oxygen concentrations in coastal waters, estuaries, and 

tidal tributaries of the Nation, including Puerto Rico, 

Alaska and Hawaii, should be as follows: 

( 1) Surface dissolved oxygen concentrations in 

70 

coastal waters shall not be less than S.O mg/ 1, except 

when natural phenomena cause this value to be depressed. 

(2) Dissolved oxygen concentrations in estuaries 

and tidal tributaries shall not be less than 4.0 mg/1 

at any time or place except in dystrophic waters or 

where natural conditions ca\!se this value to be depressed. 

The committee would like to stress the fact that, due 

to a lack of fundamental information on the DO requirements of marine and estuarine organisms, these 

requirements arc tentative and should be changed when 

additional data indicate that they are inadequate. 

Crude oil and petroleum products 

The discharge of crude oil and petroleum products into estuarine and coastal waters presents special problems in water pollution abatement. Oils 

from different sources have highly diverse propertics and chemistry. Oils are relatively insoluble in 

sea and brackish waters and surface action spreads 

the oil in thin surface films of variable thickness, 

depending on the amount of oil present. Oil, when 

adsorbed on clay and other particles suspended in 

the water, forms large, heavy aggregates that sink 

to the bottom. Additional complications arise 

from the formation of emulsions in water, leaching of water soluble fractions, and coating and 

tainting of sedentary animals, rocks, and tidal 

flats. 

Principal sources of oil pollution are numerous. 

Listed in order of their destructiveness to ecosystems, they are: 

( 1 ) Sudden and uncontrolled discharge from 

. wells towards the end of drilling operation. 

(2) Escape from wrecked and submerged oil 

tankers. 

(3) Spillage of oil during loading and unloading operations, leaky barges, and accidents 

during transport.· 

( 4) Discharge of oil-contaminated ballast and 

bilge water into coastal areas and on the 

high seas. 

(5) Cleaning and flushing of oil tanks at sea. 

On the average, a ship's content of such 

wastes is estimated to contain 2 to 3 percent oil in 1,000 to 2,000 tons of waste. 

( 6) Spillage from various shore installations, 

refineries, railroads, city dumps, garages, 

and various industrial plants. 

Spillage From Wrecked Oil Tankers 

Even though wrecks of oil tankers along the 

Atlantic coast and subsequent spillage of oil into 

the sea have been reported several times, no thor-

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