Marine Chemistry in the Coastal Environment - ACS Publications

41 Gross Analyses of Organic Matter in Seawater: Why,

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How, and from Where J O N A T H A N H . SHARP College of Marine Studies, University of Delaware, Lewes, Del. 19958

The approach i n this paper i s somewhat simplistic but i t seems desirable to f i r s t attain a f a i r l y broad knowledge on the scope of marine organic matter before dealing somewhat blindly with the more esoteric or chemically specific aspects. Undoubtedly one needs considerably more information about marine organic matter to better understand a number of areas i n chemical oceanography. In this symposium, Millero, Kester. and Wood have stated i n their papers that one needs to learn more about organic-inorganic interactions before f u l l y describing ion speciation i n coastal waters. Both Jewett and Brinkman have mentioned the problems of misinterpretation of trace metal analyses due to differences between freely ionized and organically-complexed metals. In discussing estuarine nutrient budgets, Yentsch and McCarthy have emphasized the importance of organic matter. Clearly, there i s no question of the mandate for considerable research i n the f i e l d of marine organic chemistry. In recent years, there has been much activity by workers attempting to measure certain specific pollutants i n seawater such as DDT, PCB's, and o i l hydrocarbons. However, as Table I shows, very l i t t l e i s known about the total organic pool i n seawater. The total organic pool as referenced here does not include v o l a t i l e organic matter, but as Sackett has demonstrated in this symposium, gaseous hydrocarbons are found i n f a i r l y low concentrât ions and the most abundant of the gases, methane, would contribute only about 0.03 \ig C'l (11, 12). Thus, the vast majority of the organic pool i s not easily characterized from our present analyses of specific compounds. On the other hand, better than 99% of the total inorganic pool can be characterized with eleven f a i r l y invariant constituents (13). A l l the organic constituents l i s t e d i n Table I are quite v a r i able and yet they only make up about 10% of the total. So, i n contrast to inorganic chemistry, studies of organic chemistry i n seawater must deal with a whole, of which at least 90% i s qualitatively unknown and the remainer i s at best quite variable. 682

Church; Marine Chemistry in the Coastal Environment ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

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Table I. Representative values for specific organic compounds measured i n seawater. Values are taken from l i s t e d references as approximate averages for surface oceanic or not heavily polluted coastal waters and are l i s t e d i n terms of carbon. Concentration Compound (as yg C - l " Reference Total organic pool 1 1500 Glucose 2 50 Free amino acids 30 3 Total hydrocarbons 30 4 Free fatty acids 5 15 Urea 6 10 Glycolic acid 10 7 Creatine 2 8 Vitamins 0.01 9 Chlorinated hydrocarbons 10 0.01


1

The study of organic matter i n the sea i s very d i f f i c u l t , for the possible array of constituents i s enormous. One need only look into the f i e l d of petrogenesis (14) to see how complex natural organic deposits can be. Recent studies of organic products i n l i v i n g marine organisms (15) also i l l u s t r a t e s the multitudinous compounds and complicated nature of the problem. In addition to the contribution by marine organisms as they go through d e t r i t a l avenues, excretion of bioactive compounds (16) by healthy organisms presents many interesting constituents "to" the sea. The scope of this symposium i s the coastal environment while the majority of pertinent research i n marine organic chemistry has been pursued i n oceanic waters. However, the coastal environment i s enough similar to the open ocean that a study of organic chemistry i n the former i s l i k e an oceanic study with most tools being more easily applied. A basic c r i t e r i o n for this statement and the ensuing discussion i s that a l l organic matter i n the sea should originate from plant production. In the oceanic environment, a l l production takes place i n about a 100 meter thick surface veneer (the photic zone) and then by gravity and the food web i t f a l l s out i n ever diminishing quantities so that the deep sea contains relatively old organic matter i n f a i r l y constant and low level proportions. Moving inshore from this environment, one finds that the photic zone production i s greater and that the deep water i s shallower (containing younger, less constant, and higher levels of organi c matter). Additionally, one finds an increasing influence of terriginous input of organic matter as one approaches land. I refer only to plant production (organic matter of animal origin i s , of course, indirectly from plant production) and do not include anthropogenic organic matter. I do this for three reasons. F i r s t , man's introduction of organic matter into the



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sea on a global basis i s s t i l l probably relatively small compared to that from plant origin. Second, this introduction i s an inconstant unnatural perturbation to the natural processes of production and subsequent breakdown of marine organic matter. And third, to assess this perturbation one must be able to f i r s t describe the natural processes. I do not intend to understate the capability of Homo sapiens to drastically alter his environment; but, i n the area of marine organic chemistry, his potent i a l has not yet been f u l l y achieved. With the above statements i n mind, one can see some of the design needed for the analytical methods. I f analyses can be used of sufficient sensitivity and thoroughness for deep ocean work, the same methods should be adequate i n coastal waters. In the latter case, we expect to find organic matter i n larger quantities and of younger age (thus, presumably less d i f f i c u l t to measure i n destructive analyses). Changes i n other chemical concentrations, such as lower t o t a l salt content and higher proportions of some soluble inorganic constituents, should not greatly alter efficacy of the desired methods. In upper estuaries approaching fresh water, some methods may have to be s l i g h t l y altered. Also, the increased sediment loading i n coastal waters as well as higher organic contents often requires the use of smaller sample sizes than when working i n oceanic waters. Therefore, i n the following discussion I use an oceanic viewpoint both for recommended methodology and for interpretation of the environment. Why Gross Organic Analyses Assuming an oceanic viewpoint, one can see that the vast majority of organic matter i n the sea i s not within l i v i n g organisms. The average organic content i n surface waters i s about 1.5 mg carbon per l i t e r with deep water values being less than 1 mg C 1 ~ * (1). The average concentration of l i v i n g organi c matter i s somewhat d i f f i c u l t to assess. In surface waters, organic matter large enough to be c l a s s i f i e d as particulate makes up about 1 to 7% of the total organic carbon while i n deep waters this i s usually smaller than 1% (17). Essentially a l l l i v i n g organisms f a l l within this category and estimates of l i v i n g organic matter show i t to be about 10-80% of the p a r t i culate matter i n surface waters and less than 10% i n deep waters (18). Thus, i n the oceanic environment, l i v i n g organisms probably account for anywhere from less than 0.1% up to 5% of the total organic matter. Moving nearshore, the particulate fraction accounts for a greater portion of the total organic pool (17) and probably the " l i v i n g fraction" i s also larger. Nonetheless, the majority of organic matter i n the marine environment i s non-living .



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A point i n discussing gross organic analyses i s the overall global balance of elements. Garrels and co-workers (19, 20) calculate that there i s a net flux of organic carbon from land to sea for burial i n sediments. In a similar fashion, phosphorous and nitrogen pass through the hydrosphere en route to sediments (21). As inorganic ions, they are fixed biologically and are ultimatelly carried to sediments for burial i n organic form. Thus, organic carbon, nitrogen, and phosphorous measurements are important i n studies of elemental fluxes from inorganic dissolved form into sediments. These constituents can be especially important when viewing coastal waters as a corridor between the land and the deep sea. Much of this d e t r i t a l organic matter i s important through regenerative cycles as inorganic nitrogen and phosphorous plant nutrients; this regeneration controls subsurface oxygen content (22). Rates of organic degradation are not directly measurable tErough simple s t a t i c measurements and considerable effort has been expended to indirectly measure organic u t i l i z a t i o n i n the sea (23, 24, 25). One can see easily that such estimates are made d i f f i c u l t by the fact that both the organic substrates and the organisms effecting the degrading vary from sample to sample. Thus, an attempt i s made to measure a rate for which variations occur due to both substrates and to biochemical reaction mechanisms. Observations of differences i n oxygen content of water samples can be indicative of organic degradation, but without further inputs, quantification i s not feasible. In waste water analysis, oxygen demand has long been used as an indirect measure of organic loading. The standard biochemical oxygen demand (BOD) i s a measure of bacterial use of oxygen i n a five-day incubation (26). In the standard procedure (26) i t i s recommended to seed samples with sewage bacteria when necessary and to detoxify samples when necessary. Comparisons of BOD to total organic carbon analyses have been shown to be poor (27). Clearly, application of this measure to coastal marine chemistry adds very l i t t l e to our knowledge. It does not t e l l us anything about the total organic content, but only about that which i s degraded under contrived arbitrary conditions. Another standard waste water method i s chemical oxygen demand (COD), which i s the indirect measure of oxygen u t i l i z a t i o n by degradation of organic matter i n a sulfuric acid-dichromate reflux (26). Comparison of COD to total organic carbon showed poor agreement (28) and the authors of the comparison p a r t i a l l y attributed the poor agreement to the differing oxidation states of the organic matter. This i s a good point and one that also applies to BOD analyses. An additional fault with the COD method i s that the reflux method i s probably not an exhaustive oxidation, for evolution of total organic carbon methods shows an interesting history of increasingly stronger oxidizing agents being applied (29). Indeed, recent estimates suggest that wet chemical oxidation methods are not sufficient for total dégrada-



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tion of organic matter i n seawater (1,30). These points summarized are: 1. Even though a l l the organic matter i n the sea has plant production as i t s origin, the majority of i t i s i n a non-living d e t r i t a l form; 2. Global elemental balances show a flux of carbon, nitrogen, and phosphorous into the sea from land through organic compounds; 3. Much of the organic matter i s important i n the inorganic n u t r i ent and oxygen cycles ; 4. Currently employed indirect estimates (BOD and COD) of organic loading would be inadequate parameters for marine waters. Thus, the answer to the question i n the heading i s that gross organic analyses can be valuable tools i n understanding biologically-mediated element cycles. How To Measure Measurements of organic matter i n seawater are usually preceeded by separation of suspended matter from the sample and then individual measurements of this "particulate organic matter" and the resultant f i l t r a t e or "dissolved organic matter". These divisions are quite arbitrary, but rather practical; they are discussed further below. Two types of samples result : dried particulate matter and seawater· The particulate fraction i s usually deposited on an "organic-free" microporous glass fiber or s i l v e r membrane f i l t e r . Usually several hundred to several thousand m i l l i l i t e r s must be f i l t e r e d i n the preliminary step for sufficient particulate sample to analyze, while the f i l t r a t e samples usually are done on aliquots of 5-10 m i l l i l i t e r s or less. The methods given here are this author s estimate of the best routine ones for present-day use, and none are as good as could be hoped for i n the future. For the descriptions, the samples on f i l t e r s w i l l be referred to as "particulate" and those that consist of unfiltered seawater w i l l be referred to as " t o t a l " . When total organic analysis i s made on a f i l t r a t e , i t f i t s the much used category of "dissolved" organic matter. 1

A. Total organic carbon. Two recent papers describe high temperature combustion methods for total organic carbon (1, 30). Neither method i s yet at the routine stage, so the best routine method i s a wet chemical one (31) i n i t s modified form (1). Comparison of this modified method with the high temperature one for oceanic samples (1) shows the least difference for surface waters. Therefore, this method i s probably f a i r l y accurate for nearshore waters. In the method, inorganic carbon i s purged from the sample, the sample i s sealed i n an ampoule with K2S2O3, and the CO2 from the oxidation i s later measured i n a non-dispersive infrared analyzer. B. Total organic nitrogen. The simplest and best method i s that of Armstrong, Williams, and Strickland (32) as described by Strickland and Parsons (33). In i t , the organic nitrogen i s


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degraded i n solution to nitrate by short-wave ultraviolet l i g h t . Then the nitrate i s reduced to n i t r i t e by a cadmium-copper amalgam and the resultant n i t r i t e i s read colorimetrically. With i n i t i a l nitrate, n i t r i t e , and ammonium concentrations, organic nitrogen can be calculated. C. Total organic phosphorous. A method using oxidation by B^^Og has been proposed (34) and i s used i n some laboratories. THe method suggested here Ts preferred because i t seems a b i t easier to perform especially when coupled with the organic nitrogen method. It i s the same method as the nitrogen one (32, 33) except that the f i n a l readout i s phosphate and correction i s made for i n i t i a l phosphate content. D. Particulate carbon and nitrogen. These two constituents can be analyzed simultaneously making the suggested method superior to most previous independent ones. Several workers have described variations of this method, the one cited (35) i s s l i g h t l y revised with one instrument while two other instruments can also be used (36, 37) and are used i n several laboratories. The method uses a commercial carbon-hydrogen-nitrogen analyzer which has a high temperature combustion step and a thermal conductivity gas chromatograph. E. Particulate phosphorous. This method i s again essent i a l l y that of Armstrong et. a l . (32) as used for particulate matter by Perry and Eppley (38). In i t , the f i l t e r i s placed i n d i s t i l l e d water for the ultraviolet exposure and phosphate analysis. From Where The t i t l e of this section i s meant to be somewhat of a double entendre referring both to the sources of the organic matter i n the seawater and the type of sample on which to do analyses. It was stated i n i t i a l l y that essentially a l l organic matter i n the sea comes from plant production. This being the case» one would expect to find a high concentration of organic matter at the time of high plant production and indeed this does occur (39) . In fact, there i s the contention that active healthy phytoplankton excrete directly into the sea a s i g n i f i can portion of their photoassimilated carbon (40). Proponents of this theory point out that the relative amount of phytoplankton excretion i s less i n coastal than i n oceanic waters (41). The case for extensive phytoplankton excretion i s possibly overstated and circumstantial, being largely based upon experimental artifacts.(42). In l i e u of this source, probably most of the organic matter comes from post-flowering plant production and from inefficiency i n food-chain transfer. A thought-provoking suggestion, made to me several years ago by Dr. Gordon A.



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Riley, i s that zooplankton when feeding upon phytoplankton must cause a good deal of the phytoplankton c e l l fluids to s p i l l out into the seawater. As an analogy, one can visualize a child eating a juicy piece of f r u i t . As Duursma suggested (39), probably post-flowering plankton populations contribute considerable amounts of organic matter to the sea. It i s convenient, and necessary for understanding dynamic processes, to visualize the oceanic environment i n a steady state (43). However, much of the organic matter may come from sporadic plankton blooms. Anyone working i n the open sea i s impressed by both the normal paucity of l i f e and the extensiveness of blooms. In the central gyre of the North Pacific Ocean, I worked with other researchers on samples taken from the end of a diatom bloom. A description of the phytoplankton population has been published (44) and additional publications are pending. An interesting observation from this occurrence was that a large population of the diatom appeared to be localized immediately above the temporary thermocline at about 45 meters and that the c e l l s did not appear to be very active physiologically. The horizontal extent of this population was probably only several square kilometers. Oxygen anomalies of similar geographical proportions have recently been documented (45) and they may not be uncommon phenomena. So, bloom conditions may be a cause of sporadic injections of organic matter i n the oceanic environment as they have been shown to be i n nearshore waters (39). Since these sporadic injections probably are a major source of organic matter, sampling on broad time and space scales i s necessary to obtain a representative picture of the environment. D e t r i t a l organic matter from higher plants i s known to be of utmost importance to salt-marsh food chains (46) and would seem also to be important i n general organic phosphorous cycling i n estuaries (47). How much organic matter reaches coastal waters from marsh grasses i s not known, but i t could be appreciable. To get some feeling for this, one can compare data from estuarine and oceanic waters. It i s d i f f i c u l t to get truely representative data for the comparison, but an attempt i s made here by using data from the mouth of the Patuxent River i n the Chesapeake Bay (48) and the Pacific Ocean off California (49). These two sources were chosen because they have similar data l i s t i n g s . Table II shows the comparisons, and although the exercise i s somewhat superficial, several interesting points are illustrated. F i r s t , the estuary i s richer i n a l l six organic classes than is the ocean. Second, the enrichment of estuary over ocean i s far more profound i n the particulate than i n the dissolved classes . Both these observations meet with logical explanations since the estuary serves as a greater source for the constituents and because as the water passes from the estuary to the ocean, the particulate matter w i l l tend to settle out.



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Table I I . Comparison of Estuarine and Oceanic Waters. Estuarine values from Flemer et a l . (48) and oceanic ones from Holm-Hansen et a l . (49). Micrograms per l i t e r Estuarine/ Oceanic Oceanic Estuarine Class 3.6 800 2900 Dissolved organic carbon 2.8 100 280 Dissolved organic nitrogen 1.7 15 25 Dissolved organic phosphorous 13 150 2000 Particulate organic carbon 11 25 280 Particulate organic nitrogen 10 4 40 Particulate organic phosphorous\ One would expect similar trends with inorganic constituents and that this i s the case can be illustrated with data from Kester (50). Ratios of estuarine to oceanic concentrations of iron are calculated i n the dissolved form at 30 and the p a r t i culate form at 1700. The considerably larger ratios for iron than for the gross organic constituents suggests that iron has a large estuarine source and solely a sink i n the ocean. In contrast, the organics additionally have a secondary source i n the oceanic environment through autochthonous production. This p a r t i a l l y vindicates the prior claim that anthropogenic i n f l u ences are not yet very impressive i n the form of gross organic matter. A third observation from Table II i s the trend shown with both the dissolved and particulate classes of decreasing enrichment i n going from carbon to nitrogen to phosphorous. This observation i s interesting i n that i t i l l u s t r a t e s how gross organic analyses can lead toward important qualitative understandings. Going from estuarine waters seaward, the sources of new organic matter w i l l decrease since both higher productivity and allochthonous inputs pertain to the nearshore waters. Biological breakdown i n this same geographic excursion w i l l tend to leave a greater proportion of the organic matter at sea older and thus further from i t s source on a time axis. As we might expect, the observation of qualitative d i f fer ences evident i n the above comparison therefore suggests d i f f e r e n t i a l l a b i l i t y of organic compounds containing carbon, nitrogen, and phosphorous, with compounds containing the latter two elements being less resistant. Another way of viewing this d i f f e r e n t i a l degradation i s by looking at oceanic depth p r o f i l e s , since surface waters are the source areas for organic matter which when transferred to deeper waters shows increasing degradation. Using cytochemi c a l staining techniques, i t has been shown that particulate matter contains a smaller proportion of protein i n deeper waters as compared to shallow ones (29). In this same fashion, GorHbn (51) finds that carbon to nitrogen ratios i n particulate matter increase with depth; see


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Table III· This trend suggests that nitrogen-containing compounds are generally more l a b i l e than non-nitrogenous ones.


Table III. Atomic carbon to nitrogen ratios as a function of depth. Data from Gordon (51). Depth Interval 0-250 meters 250-500 500-1000 1000-2000 2000-3000 3000-4000

Atomic C/N 8.7 11.3 11.1 14.4 15.7 17.7

A third way of imposing a time-dependent axis on organic degradation i s by looking at size classes. The rationale i n this case i s that increasingly greater proportions of the organic matter represent more non-living detritus as one looks at smaller and smaller particle sizes u n t i l ultimately the size class i s below the minimal size of any l i v i n g c e l l . This i s illustrated i n Table IV where the size column represents a downward trend from practically pure l i v i n g proteinaceous matter to an old d e t r i t a l organic residue.

Table IV. Atomic carbon to nitrogen ratios as a function of particle size. Data from Sharp and Renger (52). Size class Greater than Greater than Greater than Greater than Greater than Greater than Greater than Greater than Greater than

505 microns 308 microns 183 microns 101 microns 35 microns 20 microns 1 micron 0.003 micron 0.0012 micron

Atomic C/N 3.9 4.7 5.8 6.8 7.4 8.0 8.8 18.2 18.6

The size-class approach brings up an interesting point. As mentioned e a r l i e r , the cutoff between particulate and dissolved organic matter i s an arbitrary and functional one. I t has a long history (53) and the concept of particulate organic matter has been very valuable (54). However, the a r t i f i c i a l nature of the particulate-dissolvecTcutoff must not be forgotten and i t should be appreciated that i n nature probably a continuum of of particle sizes exists. This i s i l l u s t r a t e d i n Figure 1 which was



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constructed from carbon analyses done on various size classes. Samples i n the particulate classes (greater than 1 ym) were ultimately analyzed on f i l t e r s after prior screening according to various mesh sizes. Samples i n the less than 1 ym classes were analyzed as total organic samples after prior f i l t r a t i o n through u l t r a f i l t r a t i o n membranes. The continuum of sizes of organic matter i l l u s t r a t e s the a r t i f i c i a l i t y of the particulatedissolved cutoff. Not only i s the routine particulate class not a discrete category, but also much of the dissolved class i s probably not really i n solution. The latter observation has lead to the contention that organic matter between 0.001 and 1 ym i n size should be called c o l l o i d a l (17). This c o l l o i d a l size class i s far larger than the particulate one and i t s distribution i n the sea i s apparently unlike that of the particulate class as shown i n Figure 2. In addition to the importance of the c o l l o i dal size class, the accessibility of this class v i a u l t r a f i l tration membranes makes study of i t very desirable. Using an approach similar to that used for organic carbon, Sharp and Renger (52) found a somewhat similar continuous size spectrum for organic" nitrogen, although the quantitative nature of the curve i s somewhat different from that of carbon. Protein analyses were run on the retained c o l l o i d a l organic matter, and the protein expressed i n light of the total organic nitrogen spectrum. In this manner, i t was found that approximately 30 percent of the total organic nitrogen i n the oceanic North Pacific photic zone can be accounted for as protein (or, com bined amino acids). This i s shown i n Table V as are some carbon data. From this table, protein could also account for more than a third of the c o l l o i d a l organic carbon and for about 7 percent of the t o t a l organic carbon. Table V. Organic carbon and nitrogen from surface oceanic waters. Data from Sharp and Renger (52). Size Class Total Particulate Colloidal Colloidal protein 1. 2.

yg C-Γ" 1270 31, 216^ 85

1

ug N - l " 85 3.6 40 25

1

% total C

% total Ν

2.4 17 6.7

4.1 47 29

Calculated as 17% total carbon from Figure 1. Calculated from protein nitrogen using a weight ratio for C/N of 3.4-value for albumin (55).

This last point takes one back to Table I where a l l the l i s t e d specific compounds summed account for only 10% of the t o t a l organic carbon. So, by using gross organic analyses of size classes, one can begin to find qualitative information about significant portions of the total organic pool that were other-



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Limnology and Oceanography

Figure 1. Organic carbon in the North Atlantic Ocean as a function of size class. The apparent particle size classes are determined by various mesh plankton netting an ultrafiltration membranes. The ordinate is a cumulative percentage of the total organic carbon (17).

Limnology and Oceanography

Figure 2. Depth distribution in the North Atlantic Ocean of size classes of organic carbon. Total organic carbon (TOTAL), particulate organic carbon (0.8), and two size groups of colloidal organic carbon (0.008 and 0.025) are plotted (17).


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wise not yet classified on a molecular basis. To readdress the questions "from where": 1. The organic matter comes from plant production and largely v i a residual d e t r i t a l avenues; 2. Samples taken i n comparative sequences over geographic or size spectra can begin to provide information on the chemical nature of marine organic matter and i t s fate i n the ocean. Abstract The meanings of indirect measurements of COD and BOD and of direct measurements of particulate organic carbon, nitrogen, and phosphorous, and dissolved organic carbon, nitrogen, and phosphorous are discussed. Methods for these analyses are included i n the discussion. The common division between "particulate" and "dissolved" organics is challenged as a some what misleading arbitrary concept. A popular consideration among marine scientists i s that active healthy phytoplankton excrete appreciable amounts of organics into seawater. This i s disputed and the importance of post-flowering plankton popula tions and macrophytic plant detritus are considered. Literature Cited (1) Sharp, J. H. Total organic carbon in seawater. Comparison of measurements using persulfate oxidation and high tem perature combustion. Mar. Chem. (1973) 1:211-229. (2) Vaccaro, R. F., S. E. Hicks, H. W. Jannasch and F. G. Carey. The occurrence and role of glucose in seawater. Limnol. Oceanogr. (1968) 13:356-360. (3) Clark, Μ. Ε., G. A. Jackson and W. J. North. Dissolved free amino acids in southern California coastal waters. Limnol. Oceanogr. (1972) 17:749-758. (4) Barbier, M., D. Joly, A. Saliot and D. Tourres. Hydrocarbons from seawater. Deep Sea Res. (1973) 20:305-314. (5) Treguer, P., P. LeCorre and P. Courlot. A method for deter mination of the total dissolved free fatty-acid content of seawater. J. Mar. Biol. Assoc. U. K. (1972) 52:1045-1055. (6) Remsen, C. C. The distribution of urea in coastal and ocean ic waters. Limnol. Oceanogr. (1971) 16:732-740. (7) Shah, Ν. M. and R. T. Wright. The occurrence of glycolic acid in seawater. Mar. Biol. (1974) 24:121-124. (8) Whittledge, T. E. and R. C. Dugdale. Creatine in seawater. Limnol. Oceanogr. (1972) 17:304-314. (9) Provasoli, L. and A. F. Carlucci. Vitamins and growth reg ulators. In: W. D. P. Stewart-ed. "Algal Physiology and Biochemistry", pp. 741-787. University of California Press (Berkeley). 1974. (10) Risebrough, R. W. Chlorinated hydrocarbons. In: D. W. Hood ed. "Impingement of Man on the Oceans" pp. 259-286. WileyInterscience. 1971.



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(11) Sackett, W. M. and J. M. Brooks. Origin and distribution of low molecular weight hydrocarbons in Gulf of Mexico Coastal Waters. In: T. M. Church-ed. "Marine Chemistry in the Coastal Environment". American Chemical Society. 1975. (Paper 17, this volume). (12) Seller, W. and V. Schmidt. Dissolved non-conservative gases in seawater. In: E. D. Goldberg-ed. "The Sea". Vol. 5. Interscience (New York). pp. 219-243. 1974. (13) Culkin, F. The major constituents of seawater. In: J. P. Riley and G. Skirrow-eds. "Chemical Oceanography" Vol. 1. pp. 121-161. Academic Press. 1965. (14) Yen, T. F. Genesis and degradation of petroleum hydro carbons in the marine environment. In: T. M. Church-ed. "Marine Chemistry in the Coastal Environment". American Chemical Society. 1975. (paper 18, this volume). (15) Faulkner, D. J. and R. J. Anderson. Natural products chemistry of the marine environment. In: E. D. Goldberged. "The Sea". Vol. 5. pp. 679-714. Interscience. 1974. (16) Padilla, G. M. and D. F. Martin. Toxins and bioactive com pounds in the marine environment. In: T. M. Church-ed. "Marine Chemistry in the Coastal Environment". American Chemical Society. 1975. (Paper 40, this volume). (17) Sharp, J. H. Size classes of organic carbon in seawater. Limnol. Oceanogr. (1973) 18:441-447. (18) Hobbie, J. Ε., O. Holm-Hansen, T. T. Packard, L. R. Pomeroy, R. W. Sheldon, J. P. Thomas and W. J. Wiebe. A study of the distribution and activity of microorganisms in ocean water. Limnol. Oceanogr. (1972) 17:544-555. (19) Garrels, R. M. and F. T. Mackenzie. A quantitative model for the sedimentary rock cycle. Mar. Chem. (1972) 1:27-41. (20) Garrels, R. M. and E. A. Perry. Cycling of carbon, sulfur, and oxygen through geologic time. In: E. D. Goldberg-ed. "The Sea". Vol. 5 pp.303-336. Interscience. 1974. (21) Deevey, E. S. Biogeochemis try of lakes: major substances. In: G. E. Likens-ed. "Nutrients and Entrophication: the Limiting Nutrient Controversy", pp. 14-20. American Society of Limnology and Oceanography. 1972. (22) Redfield, A. C., Β. H. Ketchum and F. A. Richards. The in fluence of organisms on the composition of seawater. In: M. N. Hill-ed. "The Sea". Vol. 2. pp. 26-77. Interscience (New York). 1963. (23) Andrews, P. and P. J. L.Williams. Heterotrophic utiliza tion of dissolved organic compounds in the sea. III. Measurement of the oxidation rates and concentrations of glucose and amino acids in seawater. JMBAUK (1971) 51:111125. (24) Strickland, J. D. H. Microbial activity in aquatic environ ments. Symp. Soc. Gen. Microbiol. (1971) 21:231-253. (25) Azam, F. and O. Holm-Hansen. Use of tritated substrates in the study of heterotrophy in seawater. Mar. Biol. (1973)



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23:191-196. (26) APHA, AWWA, AND WPCF. "Standard Methods for the Examination of Water and Wastewater" Thirteenth Edition, pp. 489-499. Amer. Public Health Assoc. (Ν. Y.) 1971. (27) Takahashi, Y., R. T. Moore and R. J. Joyce. Direct deter mination of organic carbon in water by reductive pyrolysis. Amer. Laboratory (1972) 4:31-38. (28) Stenger, V. A. and C. E. Van Hall. Analyses of municipal and chemical wastewaters by an instrumental method for COD determination. J. Wat. Pol. Contr. Fed. (1968) 40: 1755-1763. (29) Sharp. J. H. The formation of particulate organic matter in seawater. Ph.D. dissertation (1972) Dalhousie University. Halifax, N. S. pp. 142. (30) Gordon, D, C. Jr. and W. H. Sutcliffe, Jr. A new dry combustion method for the simultaneous determination of total organic carbon and nitrogen in seawater. Mar. Chem. (1973) 1:231-244. (31) Menzel, D. W. and R. F. Vaccaro. The measurement of dis solved and particulate carbon in seawater. Limnol. Ocean ogr. (1964)9.:138-142. (32) Armstrong, F. A. J., P. M. Williams and J. D. H. Strickland. Photo-oxidation of organic matter in seawater by ultra violet radiation, analytical and other applications. Nature (1966) 211:481-483. (33) Strickland, J. D. H. and T. R. Parsons. "A Practical Hand book of Seawater Analysis." 310 pp. 2nd Edition. Fish. Res. Brd. Can., Bull. 167 (1972). (34) Menzel, D. W. and N. Corwin. The measurement of total phosphorous in seawater based on the liberation of origanically bound fractions by persulfate oxidation, limnol. Oceanogr. (1965) 10:280-282. (35) Sharp, J. H. Improved analysis for "particulate" organic carbon and nitrogen from seawater. Limnol. Oceanogr. (1974) 19:984-989. (36) Gordon, D. C., Jr. and W. H. Sutcliffe, Jr. Filtration of seawater using silver filters for particulate nitrogen and carbon analysis. Limnol. Oceanogr. (1974) 19:989-993. (37) Pella, E. and B. Colombo. Study of carbon, hydrogen, and nitrogen determination by combustion gas-chromatography. Mikrochim. Acta. (Wien) (1973):697-719. (38) Perry, M. J. and R. W. Eppley. Dynamics of phosphorous cycling in the euphotic waters of the central North Pacific Ocean. Deep Sea Res. (1975) 22 (in press). (39) Duursma, Ε. K. The production of dissolved organic matter in the sea, as related to the primary gross production of organic matter. Neth. J. Sea Res. (1963) 2:85-94. (40) Fogg, G. E. The extracellular products of algae. Oceanogr. Mar. Biol. Ann. Rev. (1966) 4:195-212. (41) Thomas, J. P. Release of dissolved organic matter from


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