96-hour TLm and the application factor do not, in fact, 

 cause decreases in productivity of the test species dur- 

 ing its life history. 



Monitoring the Marine Environment: The chief 

 problem in monitoring the marine habitat for pol- 

 lution lies in the fact that the discharge of toxic 

 materials may be intermittent. This is not neces- 

 sarily true, but it means that water samples col- 

 lected periodically reflect only the conditions at 

 the time they were collected. Significantly higher or 

 lower levels of pollution may have existed between 

 sample collections. A second major factor for con- 

 sideration is that trace amounts of pollutants or 

 effluent mixtures toxic to the biota may not be 

 readily susceptible to chemical analysis. For these 

 reasons, the analysis of resident biota for abnor- 

 mal changes offers a better tool for interpreting 

 environmental fluctuations. 



Mollusks are being collected for analysis at 

 monthly intervals in estuaries on both the Atlantic 

 and Pacific coasts (Butler, 1966 a, b). Analysis 

 of resident populations by electron capture, gas 

 chromatographic techniques reveal changes in 

 residues of 11 of the more common organochloride 

 pesticides which oysters, mussels, and some spe- 

 cies of clams readily store. These methods are use- 

 ful for rapid surveys of recent pollution. By appro- 

 priate spacing of samples in time and location, it 

 has been possible to pinpoint sources of pollution. 



It is suggested that a monitoring system of this 

 type, appropriately expanded to include fish and 

 plankton, would quickly identify areas where pol- 

 lution problems exist. Suitable analytical tech- 

 niques are available to make these samples equally 

 useful for the identification of pollution by heavy 

 metals and other toxic substances. 



Monitoring for the presence of organophosphor- 

 ous materials is feasible, but less specific for indi- 

 vidual toxic compounds. This group of pesticides 

 exerts its toxic effect on living systems by inhibiting 

 the enzyme acetylcholinesterase, which is essential 

 to conduction in nerve fibers. The nervous tissue of 

 fish and some invertebrates, appropriately ana- 

 lyzed, reveals whether the organism has been ex- 

 posed to organophosphorous materials within the 

 past 2 to 4 weeks (Holland, et al., 1967). Identifi- 

 cation of such changes can be made before toxi- 

 cant levels are high enough to cause serious 

 mortalities. 



A particularly efficient nonspecific method for 

 monitoring changes in the estuarine habitat is 

 based on the periodic collection of sedentary ani- 

 mals and plants which have attached themselves to 

 artificial cultch plates. Squares of asbestos cement 

 boards placed in strategic locations will be utilized 

 by resident biota as a habitat. At 30-day or shorter 



intervals these plates can be changed, the orga- 

 nisms enumerated, volumetrically measured or 

 chemically assayed, and an index of their relative 

 abundance obtained (Butler, 1954). 



Such plates have been maintained for nearly 20 

 years at one laboratory in Florida (Butler, 1965), 

 and they supply detailed information on the rela- 

 tive productivity of the environment in relation to 

 hydrologic changes. They will be equally useful as 

 monitors of newly introduced pollutants in this 

 area. The monitoring method of choice — and there 

 are others besides the ones suggested — will depend 

 on the specific environment and the animals of 

 particular interest. No one method will be adequate 

 and a combination of methods should provide the 

 most information in the shortest time period. 



Pesticides: Pesticides may be described as na- 

 tural and synthetic materials used to control un- 

 wanted or noxious animals and plants. They exert 

 their effect as contact or systemic poisons, as repel- 

 lents, or in some cases as attractants. It is conveni- 

 ent to classify them according to their major usage 

 such as fungicides, herbicides, insecticides, fumi- 

 gants, and rodenticides. Although data are not 

 available as to the total amount of pesticides used 

 in the United States, total production figures (in- 

 cluding exports) show that more than 875 million 

 pounds were produced in 1965. This represents an 

 increase of approximately 10 percent over 1964, 

 and more than a fivefold increase in the past two 

 decades. In recent years, the use of herbicides has 

 increased relatively more rapidly than that of other 

 pesticides. In 1964, more than 100 million acres of 

 the continental United States were treated with 

 some kind of pesticide. The trend in pesticide pro- 

 duction is towards the manufacture of more granu- 

 lar formulations. This physical adsorption of the 

 pesticide on clay particles makes possible better 

 control during application and should result in less 

 dissipation of the chemical into atmosphere and 

 into nontarget areas. 



Despite better control of pesticide applications, 

 their dispersal in drainage systems and possible 

 eventual accumulation in estuaries makes our 

 coastal fisheries especially vulnerable to their toxic 

 effects. Estuarine oyster populations, juvenile 

 shrimp, crab, and menhaden, for example, all 

 occupy the habitat where fresh and salt water mix 

 and where deposition of river silt with its load of 

 adsorbed pollutants takes place. Laboratory tests 

 show that these economically important animals 

 are especially sensitive to the toxic effects of low 

 levels of pesticides. Oysters, for example, will exist 

 in the presence of DDT at levels as high as 0-1 

 mg/1 in the environment. But at levels 1,000 times 

 less (0.1 /xg/1), oyster growth or production 



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