Rapid barium removal in the Delaware estuary

Six profiles of dissolved barium covering the entire salinity range of the Delaware River and Bay estuary from March through September 1996 were collected and analyzed. The profiles are similar to one another in both shape and magnitude except for one attribute. A sudden ( 24 days), nearly complete ( 90%) removal of dissolved Ba in midestuary occurs in mid-May followed by an 80% recovery in early June. This removal appears to be temporally and spatially coupled to the end of the spring bloom. Based on such episodic behavior, and on recent work with flocculation of diatom exudates, we conclude that the Ba depletion is caused by barite precipitation in the estuary during the late stages of the bloom. This would imply that lower estuary and inner coastal margin sediments associated with eutrophic estuaries receive a seasonal pulse of barite. The suddenness of this event also implies that sedimentary barite is strongly influenced by high productivity events. Comparison of the riverine Ba concentration with the effective riverine end member after desorptive barium release yields an estimated 30 – 40 nM Ba available from the suspended sediments as they enter the estuary. This estimate is supported by excess barium in unfiltered samples over filtered samples taken from the river and also by calculations done elsewhere. Copyright © 1999 Elsevier Science Ltd compared Ba/Ca ratios and four other geochemical tracers in Pavona to sea-surface temperatures over a 47-year period and reached similar conclusions.

1. A rapid, nearly complete removal of dissolved Ba occurred in the midestuary region of the Delaware Bay in May 1996. Its spatial and temporal proximity to the removal of silicate and ammonium, along with a lack of any other known mechanism, leads us to conclude that barite precipitated in response to the death of the spring diatom bloom. 2. The recent discovery that TEP, comprised of highly sulfated Rapid barium removal in the Delaware estuary polysaccharides connected by coordinative cation bridges, is ubiquitous to the exhaustion of diatom blooms suggests that it would provide both parts of the “sulfate-rich microenvironment” theory of barite precipitation. First, it would supply a ready, concentrated source of sulfate for release upon biotic degradation. Second, it would provide a microenvironment where diffusion is restricted allowing a concentration gradient of sulfate (and perhaps barium) to be maintained relative to sea water. In addition, the siliceous detritus caught up in these biogenic flocs may provide nucleation sites for barite precipitation. 3. Extension of this postulated mechanism to oceanic systems suggests that a disproportionate amount of barite precipitation is associated with dense blooms and, as such, sedimentary biogenic barite should not be expected to mirror total primary productivity. It may thus be appropriate to apply some correction for “background” or “low-level” production when estimating paleoproductivity using sedimentary barite. 4. Three separate calculations spanning two studies indicate a steady supply of particle-bound Ba equivalent to 30 to 40 nM enter the estuary from suspended riverine particles by ion-exchange desorption. This amount appears to be consistent throughout the hydrograph and (with less certainty) from year to year. 5. Observation of the “low-salinity removal” below 0.5‰ indicates that any characterization of estuarine Ba requires sampling well up-river of the nominal fresh-water line in order to get a true value of riverine dissolved Ba. Failure to do so may result in an overestimate of the particulate load available for desorptive input. Acknowledgments—The authors thank the outstanding crew of the R/V Cape Henlopen and acknowledge their steadfast pursuit of excellence. We express our gratitude to Lee Karrh for nutrient and chlorophyll analyses, and to Dave Kirchman and Jon Sharp for providing space on their cruises. We also thank Hugh MacIntyre and Dave Hutchins for endless discussions and details regarding diatoms and bloom dynamics in the Delaware Bay. This work would not have been possible without Glen Shen, who generously provided the instrumentation to perform the Ba analyses and the salary for MBK. HAS is grateful to George Luther and John Wehmiller for the latitude to pursue this work while under their supervision toward other ends. The study benefited from the ideas of Tom Church, Rob Sherrell, and Miriam Bertram, and the manuscript from thoughtful and thorough reviews by Jim Bishop, Adina Paytan, and Tim Shaw. This work was supported financially by grant ATM-9002401 from the Atmospheric Sciences Program of the National Science Foundation (to G. Luther), grant EAR-9315052 from the Geology and Paleontology Program at the National Science Foundation (to J. Wehmiller), the College of Arts and Science at the University of Delaware, and grants ATM-9308300 and OCE-9158496 from the National Science Foundation (to G. Shen). REFERENCES Alldredge A. L. and Gotschalk C. C. (1989) Direct observations of the mass flocculation of diatom blooms: Characteristics, settling velocities and formation of diatom aggregates. Deep-sea Res. 36, 159 – 171. Alldredge A. L., Gotschalk C., Passow U., and Riebesell U. (1995) Mass aggregation of diatom blooms: Insights from a mesocosm study. Deep-sea Res. II 42, 9 –27. Alldredge A. L., Passow U., and Logan B. E. (1993) The abundance and significance of a class of large, transparent organic particles in the ocean. Deep-sea Res. I 40, 1131–1140. Bertram M. A. and Cowen J. P. (1997) Morphological and composi- tional evidence for biotic precipitation of marine barite. J. Marine Res. 55, 577–593. Bishop J. K. B. (1988) The barite– opal– organic carbon association in oceanic particulate matter. Nature 332, 341–343. Bowen H. M. J. (1979) Environmental Chemistry of the Elements. Academic. Brook A. J., Fotheringham A., Bradly J., and Jenkins A. (1980) Barium accumulation by desmids of the genus Closterium (Zygnemaphyceae). Br. Phycol. J. 15, 261–264. Bruland K. (1983) Trace elements in sea water. In Chemical Oceanography, Vol. 8, pp. 157–220. Academic. Carriker M. R., Swann C. P., Ewart J., and Counts C. L. III (1996) Ontogenetic trends of elements (Na to Sr) in prismatic shell of living Crassostrea virginica (Gmelin) grown in three ecologically dissimilar habitats for 28 weeks: A proton probe study. J. Exp. Marine Biol. Ecol. 201, 87–135. Carroll J., Falkner K. K., Brown E. T., and Moore W. S. (1993) The role of the Ganges–Brahmaputra mixing zone in supplying barium and 226Ra to the Bay of Bengal. Geochim. Cosmochim. Acta 57, 2981–2990. Chan L. H., Drummond D., Edmond J. M., and Grant B. (1977) On the barium data from the Atlantic GEOSECS expedition. Deep-sea Res. 24, 613– 649. Chow T. J. and Goldberg E. D. (1960) On the marine geochemistry of barium. Geochim. Cosmochim. Acta 20, 192–198. Church T. M. and Wolgemuth K. (1970) Marine barite saturation. Earth Planet. Sci. Lett. 15, 35– 44. Coffey M., Dehairs F., Luther G., Church T., and Jickells T. (1997) The behavior of dissolved barium in estuaries. Est. Coast. Shelf Sci. 45, 113–121. Dehairs F., Chesselet R., and Jedwab J. (1980) Discrete suspended particles of barite and the barium cycle in the open ocean. Earth Planet. Sci. Lett. 49, 528 –550. Dehairs F., Goeyens L., Stroobants N., Bernard P., Goyet C., Poisson A., and Chesselet R. (1990) On suspended barite and the oxygen minimum in the Southern Ocean. Global Biogeochem. Cycles 4, 85–102. Dehairs F., Lambert C. E., Chesselet R., and Risler N. (1987) The biological production of marine suspended barite and the barium cycle in the western Mediterranean Ocean. Biogeochemistry 4, 119 – 139. Dehairs F., Stroobants N., and Goeyens L. (1991) Suspended barite as a tracer of biological activity in the Southern Ocean. Marine Chem. 35, 399 – 410. Dunbar R. B. and Cole L. E. (1995) The tropical influence on global climate: Are surprises the rule? EOS: Trans. Am. Geophys. Union 76, 431. Dymond J., Suess E., and Lyle M. (1992) Barium in deep-sea sediment: A geochemical proxy for paleoproductivity. Paleoceanography 7, 163–181. Edmond J. M., Boyle E. D., Drummond D., Grant B., and Mislick T. (1978) Desorption of barium in the plume of the Zaire (Congo) River. Netherlands J. Sea Res. 12, 324 –328. Fenchel T. and Finlay B. J. (1984) Geotaxis in the ciliated protozoan Loxodes. J. Exp. Biol. 110, 17–33. Finlay B. J., Hetherington N. B., and Davison W. (1983) Active biological precipitation in lacustrine barium chemistry. Geochim. Cosmochim. Acta 47, 1325–1329. Fisher N. S. and Reinfelder J. R. (1995) The trophic transfer of metals in marine systems. In Metal Speciation and Bioavailability in Aquatic Systems. (ed. A. Tessier and D. R. Turner). J Wiley. Fisher N. S., Guillard R. R. L., and Bankston D. C. (1991) The accumulation of barium in marine phytoplankton grown in culture. J. Marine Res. 49, 339 –354. Francois R., Honjo S., Manganini S., and Ravizza G. (1995) Biogenic ¸ barium fluxes to the deep-sea: Implications for paleoproductivity reconstruction. Global Biogeochem. Cycles 9, 289 –303. Gingele F. and Dahmke A. (1994) Discrete barite particles and barium as tracers of paleoproductivity in South Atlantic Sediments. Paleoceanography 9, 151–168. Goldberg E. D. and Arrhenius G. O. S. (1958) Chemistry of Pacific pelagic sediments. Geochim. Cosmochim. Acta 13, 153–212. Hanor J. S. and Chan L.-H. (1977) Non-conservative behavior of H. A. Stecher III and M. B. Kogut barium during mixing of Mississippi River and Gulf of Mexico waters. Earth Planet. Sci. Lett. 37, 242–250. Hart S. R. and Cohen A. L. (1996) An ion probe study of annual cycles of Sr/Ca and other trace elements in corals. Geochim. Cosmochim. Acta 60, 3075–3084. Hart S. R., Cohen A. L., and Ramsay P. (1997) Microscale analysis of Sr/Ca and Ba/Ca in Porites. Proc. 8th Int. Coral Reef Symp. 2, 1707–1712. Ketchum B. H. (1952) The distribution of salinity in the estuary of the Delaware River. Woods Hole Oceanographic Institution, Rep. 52103. Kloareg B. and Quantrano R. S. (1988) Structure of the cell walls of marine algae and ecophysiological functions of the matrix polysaccharides. Oceanogr. Marine Biol. Annu. Rev. 26, 259 –315. Lea D. W. and Boyle E. A. (1989) Barium content of benthic foraminifera controlled by bottom-water composition. Nature 338, 751– 753. Lea D. W. and Boyle E. A. (1990a) A 210,000-year record of barium variability in the deep northwest Atlantic Ocean. Nature 347, 269 – 272. Lea D. W. and Boyle E. A. (1990b) Foraminiferal reconstruction of barium distributions in water masses of the glacial oceans. Paleoceanography 5, 719 –742. Lea D. W. and Boyle E. A. (1991) Barium in planktonic foraminifera. Geochim. Cosmochim. Acta 55, 3321–3331. Lea D. W., Shen G. T., and Boyle E. A. (1989) Coralline barium records temporal variability in equatorial Pacific upwelling. Nature 340, 373–376. Li Y.-H. and Chan L.-H. (1979) Desorption of Ba and 226Ra from river-borne sediments in the Hudson estuary. Earth Planet. Sci. Lett. 43, 343–350. Mopper K., Zhou J., Sri Ramana K., Passow U., Dam H. G., and Drapeau D. T. (1995) The role of surface-active carbohydrates in the flocculation of a diatom bloom in a mesocosm. Deep-sea Res. II 42, 47–73. Passow U. and Alldredge A. L. (1995) Aggregation of a diatom bloom in a mesocosm: The role of transparent exopolymer particles (TEP). Deep-sea Res. II 42, 99 –109. Passow U., Alldredge A. L., and Logan B. E. (1994) The role of particulate carbohydrate exudates in the flocculation of diatom blooms. Deep-sea Res. I 41, 335–357. Paytan A., Kastner M., and Chavez F. (1996) Glacial to interglacial fluctuations in productivity in the equatorial Pacific as indicated by marine barite. Science 274, 1355–1357.