deposition of zinc and cadmium by marine bacteria in estuarine sediments

Deposition of Zinc and Cadmium by Marine Bacteria in Estuarine SedimentsAuthor(s): C. J. McLerran and Charles W. HolmesSource: Limnology and Oceanography, Vol. 19, No. 6 (Nov., 1974), pp. 998-1001Published by: American Society of Limnology and OceanographyStable URL: http://www.jstor.org/stable/2834797 .

Accessed: 12/06/2014 16:04

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 91.229.229.212 on Thu, 12 Jun 2014 16:04:10 PMAll use subject to JSTOR Terms and Conditions

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

http://www.jstor.org/stable/2834797?origin=JSTOR-pdf

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


998 Notes

of pelagic zooplankton in lakes with varying trophy. Ekol. Pol., Ser. A 17: 663-708.

GOPHEN, M., B. Z. CAVARI, AND T. BERMAN. 1974. Zooplankton feeding on differentially labeled algae and bacteria. Nature (Lond.) 247: 393-394.

INFANTE, A. 1973. Untersuchungen fiber die Ausnutzbarkeit verschiedener Algen fur das Zooplankton. Arch. Hydrobiol. Suppl. 42(3), p. 340-405.

JONES, D. A., T. JAWED, AND P. TILY. 1972. The acceptance of artificial particles by planktonic crustacea. Chemosphere 1(3): 133-136.

LENARZ, H. 1972. Beitrage zu einer Revision

der 14C-Methode zur Messung der Primarpro- duktion in Binnengewassern. Diss. Albert- Ludwigs-Univ. Freiburg i. Br. 83 p.

MCQUEEN, D. J. 1970. Grazing rates and food selection in Diaptomus oregonensis (Copep- oda) from Marion Lake, British Columbia. J. Fish. Res. Bd. Can. 27: 13-20.

REEVE, M. R. 1963. The filter-feeding of Arte- mia. 2. In suspensions of various particles. J. Exp. Biol. 40: 207-214.

Submitted: 8 May 1973 Accepted: 1 March 1974

Deposition of zinc and cadmium by marine bacteria in estuarine sediments Abstract-Mixed cultures of marine bac-

teria isolated from the sediments of Corpus Christi Harbor were examined for their ability to assimilate or precipitate radioactive zinc and cadmium from solution. Test data indicate that during summer, when bacterial activity is at a maximum, the bacteria and their metabolic byproducts play a significant role in the removal of zinc and cadmium from seawater and their subsequent deposition in marine sediments.

Corpus Christi Bay and Harbor sediments contain anomalous levels of zinc and cadmium. Zinc concentrations range from a maximum of 11,000 ppm in the harbor to a minimum of 6 ppm in the bay 10 km from the harbor entrance, and cadmium ranges from 130 ppm to 0.1 ppm in the same locations (Holmes et al. 1974). As these elements pose a threat to marine organisms in the estuarine system (Petty- john 1972; IDOE 1972), and possibly to man, the pathways whereby they are trans- ported through the system should be under- stood.

One step in the cycle of zinc and cadmium through the estuarine system is movement from the water to the sediment. Many in- vestigators have stated that marine bacteria play an important part in the deposition of heavy metals in estuarine sediments (Pomeroy et al. 1966; Oppenheimer 1960; Lowman et al. 1971). However, little work has been done with bacterial isolates to examine their specific role in heavy-metal

assimilation and precipitation from seawater. This report presents preliminary data on the role of mixed bacterial cultures from Corpus Christi Harbor in the assimilation and precipitation of radioactively labeled zinc and cadmium.

Sediment samples were collected from the bottom of the harbor with a corer con- structed of polyvinylchloride (PVC) tubing fitted with a one-way valve and weighted with a cement block. The PVC core liners were capped and the samples refrigerated until examined, within 24 hr of collection. Bacterial populations in the sediment and water column were estimated by the minimum dilution plate-count method, using Difco 2216 marine agar.

For assimilation and precipitation studies, 1 g of samples (wet weight) were removed from the top 3 cm of the cores and diluted 1:5 in sterile phosphate-buffered saline (PBS). After thorough shaking, O.5-ml portions of the diluted samples were inoculated into 10-ml deeps of Difco 2216 E marine broth and incubated at 230C to culture aerobic chemoorganotrophic bacteria. After 72 hr of incubation, the cultures were passed to additional broth deeps. A direct microscopic count technique, using methy- lene blue stain and a Briteline hemacytom- eter was used to count the bacteria present in the second set of broth deeps at 72 hr postinoculation.

After the counts, 28 broth deeps were inoculated with 11 x 106 organisms each.



Notes 999

Table 1. Profile of bacterial counts in the water and sediments of Corpus Christi Harbor.

Depth Bacteria/ml*

Water surface 6.0 X 103 9 m 7.0 X 103 14 m 8.0 X 103 Sediment surface 1.9 X 106

* Heterotrophic-aerobic bacteria only.

To 12 cultures, 65Zn was added at a concentration of 0.5 /Ci ml-', and to 12 more deeps, 109Cd was added at a concentration of 0.5 /Ci ml-'. In each experiment, per- formed in duplicate, 2 tubes were used as uninoculated radioisotope controls, 2 tubes were used as inoculated controls without radioisotopes, and the remaining 12 tubes were used to establish the growth curve and measure radioisotope deposition.

After inoculation and the addition of the radioisotope, the cultures were incubated at 230C. At 24-hr intervals (144 hr total), 2 tubes each of the '09Cd-labeled cultures and the 65Zn-labeled cultures were examined for total number of bacteria and the amount of radioisotope assimilated or precipitated. The bacteria, precipitate, and supernatant fluids were separated by dif- ferential centrifugation. Microscopic exam- ination of the separated components showed that more than 90% of the bacteria were separated from the precipitate. The bacteria and precipitate were washed three times in PBS to remove all traces of broth and resuspended in 3 ml of PBS. The PBS wash was then added to the supernatant fluid. The separated components were examined for radioactivity in a 256-channel pulse-height analyzer using a 2 x 2 Nal well crystal. The bacteria were counted at each testing period by direct microscopy, and a growth curve was established.

In most marine environments, bacterial populations are highest in the first few centimeters of the sediment (Oppenheimer 1960). This was also true at our sampling site. Bacterial populations in the top 3 cm of sediment were several orders of magni- tude larger than those in the water column (Table 1). The counts given represent winter conditions when the water temper-

40

_ 30 PRECIPITATE-/'

O / 0 / x / X20 X. // U /

/

10/

// ,/'BACTERIA

24 48 72 96 120 144 TIME (HR)

Fig. 1. Removal of 65Zn from solution by a mixed culture of marine bacteria (CPM-counts per minute).

ature was about 12?C; under warmer conditions, each would probably be greater.

Gram stains of representative colonies and of broth cultures revealed a diverse bacterial flora. The predominant organisms were gram negative cocci, coccobacilli, and rods. Visible in smaller numbers were gram positive rods as well as spirochetal and vibrioid forms. No attempt was made at this point to identify the various species.

Bacteria grown in the broth deeps produced substantial quantities of hydrogen sulfide under aerobic and microaerophilic conditions. Hydrogen sulfide production was confirmed by inoculating the cultures into tubes of triple sugar iron (TSI) medium and observing them for 96 hr: precipitation of ferrous sulfide began about 48 hr after inoculation. The precipitate had the characteristic appearance and odor of the "black mud" common to many ocean floors (Stanier et al. 1965).

The growth curve for the mixed bacterial culture showed that exponential growth



1000 Notes

200 , 190

170 ,

150 /

130 /

100 f-PRECI PITATE X 90 /

t70 7 50 / BACTERIA

30 //

10

24 48 72 96 120 144 TIME (HR)

Fig. 2. Removal of '"Cd from solution by a mixed culture of marine bacteria (CPM-counts per minute).

began within 6 hr of inoculation and con- tinued until about 96 hr postinoculation. The maximum stationary phase was reached by 120 hr.

Of the 65Zn added to the cultures, about 85% was removed from solution by the bacteria in 120 hr. The zinc was removed in two ways. About 20% of the sedimented zinc was directly associated with the bacterial cells; we do not know whether it was actually assimilated by the bacteria or bound to the surface of the cells. About 80% of the sedimented zinc was removed from solution by precipitation (Fig. 1). Because of the large amounts of H2S produced by the bacteria, zinc probably precipitated as ZnS (Holmes et al. 1974) or as a coprecipitate with the FeS. Molybdenum has been shown to coprecipitate with FeS in estuarine conditions (Bertine 1970), and other transition elements such as Zn and Cd might react in the same manner.

The bacterial removal of cadmium from solution followed a pattern similar to that of zinc. About 70% of the 109Cd added to

the cultures was removed from solution in 120 hr. Figure 2 shows that the association of cadmium with the bacterial cells played a minor role in its sedimentation; this association reached a maximum at 48 hr postinoculation and then decreased slowly with time. Precipitation accounted for 85-90% of the sedimented cadmium. The cadmium, like the zinc, was probably precipitated as CdS or as a coprecipitate with the FeS.

The curves for the removal of 65Zn and 109Cd from solution closely parallel the bacterial growth curve. The data thus indicate that during periods of high metabolic activity, bacteria may play a significant if not dominant role in the transport of zinc and cadmium from seawater to sediment. Bacterial activity and H2S production in Corpus Christi Harbor are at a maximum during summer (McLerran unpublished data). As most zinc and cadmium deposition occurs in summer (Holmes et al. 1974), we believe that bacteria play a major role in the deposition of zinc and cadmium in this system.

We thank R. E. Hunter, S. M. Pier, and E. M. Davis for their helpful suggestions in the preparation of this report.

C. J. McLerran Charles W. Holmes

U.S. Geological Survey P.O. Box 6732 Corpus Christi, Texas 78411

References BERTINE, K. K. 1970. The marine geochemical

cycle of chromium and molybdenum. Ph.D. thesis, Yale Univ.

HOLMES, C. W., E. A. SLADE, AND C. J. McLER- RAN. 1974. Migration and redistribution of zinc and cadmium in a marine estuarine system. Environ. Sci. Technol. 8: 255-259.

INTERNATIONAL DECADE OF OCEAN EXPLORATION. 1972. Baseline studies of pollutants in the marine environment and research recommen- dations. Baseline Conf. 24-26 May 1972. 54 p.

LOWMAN, F. G., T. R. RICE, AND F. A. RicHARDs. 1971. Accumulation and redistribution of ra- dionuclides by marine organisms, p. 161-199. In Radioactivity in the marine environment. Nat. Acad. Sci.

OPPENHEIMER, C. H. 1960. Bacterial activity



Notes 1001

in sediments of shallow marine bays. Geo- chim. Cosmochim. Acta 19: 244-260.

PETTYJOHN, W. A. 1972. Trace elements and health, p. 244-251. In W. A. Pettyjohn [ed.], Water quality in a stressed environment. Burgess.

POMEROY, L. R., E. P. ODUM, R. E. JOHANNES, AND B. ROFFMAN. 1966. Flux of "2P and 65Zn through a salt-marsh ecosystem, p. 177-

188. In Disposal of radioactive wastes into seas, oceans and surface waters. IAEA.

STANIER, R. Y., M. DOUDOROFF, AND E. A. ADEL- BERG. 1965. The microbial world, 2nd ed. Prentice-Hall.

Submitted: 30 January 1974 Accepted: 31 May 1974

A large-volume interstitial water sediment squeezer for lake sediments' Abstract-An 800-cc interstitial water sed-

iment squeezer has been designed with all- Teflon surfaces. It is compact, light, highly portable, and made from readily available stock material. The cost is nominal.

Most interstitial water sediment squeezers have been designed for compact marine sediments with low water content collected in small diameter coring tubes. The gas pressure squeezers of Reeburgh (1967) and Presley et al. (1967) necessitate a relatively long period of squeezing per sample to obtain a working volume of water because of gas breakthrough and subsequent bypass. The piston squeezer of Siever (1962) is costly and not free from trace metal contamination due to interaction of the stain- less steel chamber with acidic or sulfide- rich waters. Kalil and Goldhaber (1973) designed a piston squeezer that appears highly suitable for compact marine sediments but not for unconsolidated lake sediments because of the method of core sectioning required.

Barnes (1973) has designed an in situ sampler for deep-sea sediments. Its maximum efficiency relies on a contrast in pressure between the sample chamber and the environment and thus it is unsuitable for shallow lacustrine sampling. Addition- ally, only one sample can be obtained at one core site.

The squeezer described here has several advantages for lake sediment-interstitial

'The work on which this report is based was supported entirely by funds provided by the Of- fice of Water Resources Research.

water studies. It is possible to squeeze a large volume of sample (as much as 800 cc). We used a 10-cm-ID corer (Davis and Doyle 1969). The squeezer can be cleaned and reloaded quickly and its light weight makes it highly portable. A relatively large volume of water is obtained in a short period of time (75 ml per 200 cc of sediment in 15 min). The sample does not come in contact with any metal, although this feature does not eliminate all possible contamination (Robertson 1968). Cost is relatively low (less than $100 in early 1974) because many parts are hard- ware stock and machining time is minimal: about 10 hr per squeezer, including assem- bly time. Detailed diagrams are shown in Figs. 1 and 2.

Four squeezers are mounted on a drilled plywood board which allows a 125-ml polyethylene bottle to be fitted underneath and wedged tightly against the drainage hole of the squeezer. The filter paper, gasket, and PVC cylinder are placed in position and the two springs are connected from the metal clamps on the cylinder to eyebolts on the mounting board to pre- vent any leakage of the sample before the top has been secured and the gasket seated. The sample is placed at the bottom of the cylinder, the piston is inserted as far as the air hole (the 0-rings have been lubricated with a small amount of silicon grease), and the top is bolted on. Pressure is applied steadily by periodically turning down the piston screw. Although there is a brief exposure to air during the loading of the cylinder, the large volume of sediment



deposition of zinc and cadmium by marine bacteria in estuarine sediments

Documents