ammonia determinations by two methods in the northeast equatorial pacific ocean

Ammonia Determinations by Two Methods in the Northeast Equatorial Pacific OceanAuthor(s): Jane J. MacIsaacSource: Limnology and Oceanography, Vol. 12, No. 3 (Jul., 1967), pp. 552-554Published by: American Society of Limnology and OceanographyStable URL: http://www.jstor.org/stable/2833353 .

Accessed: 16/06/2014 02:10

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

American Society of Limnology and Oceanography is collaborating with JSTOR to digitize, preserve andextend access to Limnology and Oceanography.

http://www.jstor.org

This content downloaded from 185.2.32.46 on Mon, 16 Jun 2014 02:10:49 AMAll use subject to JSTOR Terms and Conditions

http://www.jstor.org/action/showPublisher?publisherCode=limnoc

http://www.jstor.org/stable/2833353?origin=JSTOR-pdf

http://www.jstor.org/page/info/about/policies/terms.jsp


552 NOTES AND COMMENT

TABLE 1. Christmas Lake, 0630-0730 hours, 30 March 1963

Temperature (C) Lake Ice body

Lo- Water Body Max Bot- thick- temp ca- depth of near tom of ness 24 Mar tion (im) lake ice lake (cm) 1963

1 1.6 4.7 5.4 4.7 46 1.1 (16 Mar) 2 3.7 4.2 5.4 4.4 - 1.9 3 14.3 2.8 4.2 3.6 51 1.9 4 24.4 2.5 2.5 3.1 43 2.3

temperature of the lake in inverse propor- tion to depth, from less than IC to 3.6C. A distinct maximum had formed at loca- tions 1, 2, and 3, that was sufficiently persistent to be evident in early morning after a night of light freezing. Location 4 probably had had a small temperature maximum the previous day that had been destroyed by the cold night temperature.

Similar measurements were made also during March 1966 in Lotus Lake and in Lake Minnetonka, which are both in the vicinity of Christmas Lake.

Lotus Lake is about equal in area to Christmas Lake, but it is much shallower. Temperature behavior there was similar to that of Christmas Lake except that temperatures were generally higher. The last measurement in Lotus Lake (1630 hours on 16 March) recorded a maximum just beneath the ice of 6.1C, with 4C water below.

Lake Minnetonka is much larger than Christmas Lake, but it has similar depths (30 m max). The ice there was 14 cm thicker than that of Christmas Lake on

7 March and 11 cm thicker on 17 March. The lake body temperature throughout the observations was about O.1C less than that of Christmas Lake. The decrease of ice thickness during the observations was about 20 cm on Lake Minnetonka (18 cm in Christmas Lake). A thin layer of low hardness water formed beneath the ice, but a temperature higher than that of the water below did not develop, probably because of the greater absorption of solar radiation in the thicker ice.

Hutchinson (1957) has noted and ex- plained European observations of this phe- nomenon. His associate, U. M. Cowgill, observed similar temperature distributions in Linsley Pond, Connecticut, during win- ter of 1965-1966 (G. E. Hutchinson, personal communication).

Birge also observed a warm layer beneath the ice of Lake Mendota, Wisconsin, in 1898 and at intervals thereafter. He inferred its origin (Birge 1910) but later raised doubts about it (Neess and Bunge 1957).

HIBBERT HILL Department of Botany, University of Minnesota, Minneapolis 55455.

REFERENCES

BIRGE, E. A. 1910. On the apparent sinking of ice in lakes. Science, 31: 856-857.

HUTCHINSON, G. E. 1957. A treatise on limnology v. 1. Wiley, New York. 1015 p.

NnE:ss, J. C., AND W. W. BUNGE, JR. 1957. An unpublished manuscript of E. A. Birge on the temperature of Lake Mendota, part II. Trans. Wisconsin Acad. Sci., 47: 78-83.

AMMONIA DETERMINATIONS BY Two METHODS IN THE NORTHEAST EQUATORIAL PACIFIC OCEAN1

The methods available for determining ammonia concentrations in seawater are of limited usefulness at sea from aspects of either sensitivity or feasibility. The method developed by Richards and Kletsch (1964), in which ammonia is oxidized to nitrite with hypochlorite, is managed easily at

'This work was supported by National Science Foundation Grant GB-5532.

sea but simultaneously detects other labile nitrogen compounds susceptible to oxidation by hypochlorite, such as amino acids. Nitrogen measured by this method will be designated "oxidizable-N." For more precise ammonia-nitrogen determinations other methods must be used, and the extraction procedure of Prochazkova (1964) has proved surprisingly convenient aboard



NOTES AND COMMENT 553

TABLE 1. Comparison of euphotic zone ammonia values as measured in replicated determinations with the methods of Richards and Kletsch and of ProcMzkova

Light penetration depth (%)

100 50 25 10 1

(B/A) (B/A) (B/A) (B/A) (B/A) Station A* Bt X 100 A B X 100 A B X 100 A B X 100 A B X 100

642 1.28 0.25 20 2.22 0.28 13 1.48 0.35 24 2.36 0.30 13 0.78 0.23 30 643 4.92 0.32 6 1.13 0.31 27 1.08 0.16 15 0.98 0.29 30 1.00 0.37 37 644 0.72 0.23 32 0.90 0.30 33 0.88 0.20 23 1.32 0.24 18 0.38 0.19 50 645 0.66 0.25 38 0.72 0.25 35 0.86 0.30 35 0.76 0.31 41 0.40 0.11 28 651 0.84 0.19 23 1.74 0.22 13 1.48 0.55 37 0.66 0.58 88 0.62 0.61 100 651-a 1.50 0.22 15 2.34 0.27 12 2.23 0.28 13 0.37 0.12 32 - -

Mean 22 22 24 37 49 27t 36t

* (A) Richards and Kletsch method (in ,ug-at./liter). t (B) Prochazkova method (in ug-at./liter). : Mean, omitting value for station 651.

ship.2 Though this method is apparently specific for ammonia, certain ions and substances, including some labile nitrogen compounds, can interfere with the method to reduce its sensitivity. Both of these methods were used on Te Vega Cruise 13 in the northeast equatorial Pacific Ocean; from a comparison of the results, certain useful generalizations can be made con- cerning the proportions of ammonia-nitrogen and unspecified dissolved nitrogen in the water column.

The water samples were collected at stations lying along a line between Aca- pulco, Mexico, and the Galapagos Islands. A large-volume glass sampler was used to take water from the euphotic zone at depths determined with a submarine pho- tometer to represent 100, 50, 25, 10, and 1% of surface light penetration. Following this a Nansen cast was made to greater depths. Close estimates of the NH4+-N concentrations within the euphotic zone were of prime concern. Samples were analyzed in triplicate with the Prochaz-

2William Zoller at the Institute of Marine Sci- ence, University of Alaska, has modified the Pro- ch'azkova method: 1) before analysis, samples including blanks and standards are refrigerated so that their temperatures do not exceed 15C during the initial 5 min of the analytic procedure; 2) a 2-min extraction period is used; 3) as the organic phase is separated into test tubes, it is filtered through a cotton ball to remove any suspended matter.

kova method, and duplicate determinations were made with the Richards and Kletsch procedure. Samples from the Nansen casts ordinarily were analyzed according to Richards and Kletsch, but occasionally the extraction method was applied as well. Water from the hydro- cast was in such demand that it was usu- ally impossible to make more than a single determination of ammonia at each depth. All Richards and Kletsch measurements were corrected for ambient nitrite, as euphotic zone nitrite values are frequently significant in the region of the cruise track.

The standard deviation for each method was determined at sea with conditions identical to those under which determinations were made. With the Richards and Kletsch method, the standard deviation for nine seawater standards of 2.55 ug-at./liter was ?0.41 ,ug-at./liter. The standard deviation with the Prochazkova extraction technique for 10 seawater standards con- taining 0.40 ug-at./liter was ?0.10 ,ug- at./liter.

The distilled water available was con- taminated with ammonia so a true reagent blank could not be determined. Most of the blank value was assumed to be a result of water contamination in the reagent solutions. As a best estimate of the ammonia added with the reagents, samples of distilled water used in reagent solutions were analyzed for ammonia; the



554 NOTES AND COMMENT

TABLE 2. Comparison of ammonia values throughout the water column at Te Vega station 645 by single determinations with the methods of Richards and Kletsch and of Prochdzkova. 1%

light-penetration depth at 43 m

Depth (m) A* Bt

10 1.42 0.30 20 0.84 0.54 30 0.67 0.77 34 0.81 0.80 39 0.71 0.61 43 0.44 0.62 48 0.81 0.50 58 0.20 0.34

146 0.51 0.55 283 0.24 0.23 528 0.27 0.39

* (A) Richards and Kletsch method (in Ag-at./liter). t (B) Prochazkova method (in Ag-at./liter).

observed optical densities were considered to reflect the ammonia in the 50 ml of distilled water sample, plus that in the distilled water of the reagent solutions (approx 25 ml for either method). The observed optical densities were then reduced by two-thirds to give the blank values used. The blank values thus obtained (0.015-0.025 OD in a 1-cm cell for both methods) were quite consistent throughout the cruise.

Results from samples taken with the glass sampler are presented in Table 1. As one might expect, the Richards and Kletsch method gives higher values than that of Prochazkova. The NH4+-N plus oxidizable-N levels also show greater vari- ations than those of ammonia-nitrogen. Table 2 shows results typical of those obtained when single determinations with each method were made on Nansen cast samples. The ratio of NH4+-N to oxidizable-N varies, with the mean percentages of NH4+-N in the total nitrogen measured increasing with depth. Especially at depth, the precision of the single determinations is not great enough to allow calculation of meaningful fractions of ammonia in the total nitrogen measured, but differences between the two types of measurement become insignificant below the

euphotic zone. Thus, in this region about 25% of the nitrogen measured by the Richards and Kletsch procedure in the upper euphotic zone is due to ammonia- nitrogen, and this percentage increases such that below the euphotic zone the values obtained with this method very nearly represent ammonia-nitrogen concentrations.

Reduced sensitivity of the Prochazkov'a method would exaggerate these differences, and it is difficult to assess the influ- ence of interfering compounds. But if the presence of interfering agents can be esti- mated from the Richards and Kletsch determinations, the concentrations involved would not alter significantly the Prochazkovai values.

Although precise measurements of NH4+-N concentration are often necessary, the importance of other dissolved nitrogen sources such as those included in the Richards and Kletsch determination should be recognized. There is little doubt that phytoplankton is involved in the cycling of dissolved organic nitrogen. Dugdale and Goering (unpublished) have observed the uptake of 15N-labeled urea and glycine by phytoplankton in many regions; near Unimak Pass in the Aleutian Islands, D. M. Schell (personal communication) has found 15N in the dissolved organic fraction of labeled N03--N uptake experiments.

JANE J. MACISAAC3

Department of Oceanography, University of Hawaii, Honolulu.

REFERENCES

PROCHAZKOVA, L. 1964. Spectrophotometric determination of ammonia as rubazoic acid with bispyrazalone reagent. Anal. Chem., 36: 865-871.

RICHARDS, F. A., AND R. A. KLETSCH. 1964. The spectrophotometric determination of ammonia and labile amino compounds in fresh and seawater by oxidation to nitrite, p. 65- 81. In Y. Miyake and T. Koyama [eds.], Recent researches in the fields of hydro- sphere, atmosphere and nuclear geochem- istry. Maruzen Co., Tokyo.

3Present address: 4842 NE 43rd St., Seattle, Washington.



ammonia determinations by two methods in the northeast equatorial pacific ocean

Documents