Abstract
Net remineralization rates of organic matter and bacterial growth rates were observed in dark-bottle incubation experiments conducted in July–August and February with water samples collected from sites in the Mississippi River plume of the Gulf of Mexico. Our objectives were to measure site-specific degradation rates of labile dissolved and particulate organic matter, quantify the potential importance of bacteria in these processes, and examine the kinetics of degradation over time. Unfiltered samples, and samples treated to remove (or dilute out) particles larger than bacteria, were enclosed in 9-1 bottles and incubated in the dark for 3–5 d. Respiration rates and inorganic compound accumulation rates were higher in summer than in winter and were highest in unfiltered surface samples at sites of intermediate salinities where phytoplankton were most abundant. The ratio of ammonium accumulation to oxygen removal in summer experiments suggested that the mineralized organic material resembled “Redfield” stoichiometry. Chemical fluxes were greater in bottles containing large (>1–3 μm) particles than in the bottles with these particles removed, but bacterial activities were generally similar in both treatments. These results suggest that particle consumers were an important component of total organic matter degradation. However, these experiments may have underestimated natural bacterial degradation rates because the absence of light could affect the production of labile organic substrates by phytoplankton. In agreement, with this hypothesis, bacterial growth rates tended to decrease over time in summer in surface plume waters where phytoplankton were abundant. In conjunction with other data, our results indicate that heterotrophic processes in the water column are spatially and temporally dependent on phytoplankton production.
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Literature Cited
Benner, R., G. Chin-Leo, W. Gardner, B. Eadie, andJ. Cotner. 1992. The fates and effects of riverine and shelf-derived DOM on Mississippi plume/Gulf shelf processes, p. 84–94.In Nutrient Enhanced Coastal Ocean Productivity. Publication number TAMU-SG-90-109, Sea Grant Program, Texas A&M University, Galveston, Texas.
Benner, R. andM. Strom. 1993. A critical evaluation of the analytical blank associated with DOC measurements by high-temperature catalytic oxidation.Marine Chemistry 41:1–3.
Carrit, D. E. andJ. H. Carpenter. 1966. Comparison and evaluation of currently employed modifications of the Winkler method for determining dissolved oxygen in sea water. A NASCO report.Journal of Marine Research 24:286–318.
Chin-Leo, C. andR. Benner. 1992. Enhanced bacterioplankton production and respiration at intermediate salinities in the Mississippi River plume.Marine Ecology Progress Series 87: 87–103.
Chin-Leo, G. andD. L. Kirchman. 1988. Estimating bacterial production in marine waters from the simultaneous incorporation of thymidine and leucine.Applied and Environmental Microbiology 54:1934–1939.
Chin-Leo, G. andD. L. Kirchman. 1990. Unbalanced growth in natural assemblages of marine bacterioplankton.Marine Ecology Progress Series 61:1–8.
Cole, J. J., S. Findlay, andM. L. Pace. 1988. Bacterial production in fresh and saltwater ecosystems: A cross-system overview.Marine Ecology Progress Series 43:1–10.
Cole, J. J., G. E. Likens, andD. L. Strayer. 1982. Photosynthetically produced dissolved organic carbon: An important carbon source for planktonic bacteria.Limnology and Oceanography 27:1080–1090.
Cotner, J. B. andW. S. Garner. 1993. Heterotrophic bacterial mediation of ammonium and dissolved free amino acid fluxes in the Mississippi River Plume.Marine Ecology Progress Series 93:75–87.
Dagg, M. J. andP. Ortner. 1992. Mesozooplankton grazing and the fate of carbon in the northern Gulf of Mexico, p. 117–121.In Nutrient Enhanced Coastal Ocean Productivity. Publication number TAMU-SG-92-109. Sea Grant Program, Texas A&M University, Galveston, Texas.
Dagg, M. J., P. B. Ortner, andF. Al-Yamani. 1987. Winter-time distribution and abundance of copepod nauplii in the northern Gulf of Mexico.Fisheries Bulletin, United States 86:319–330.
Ertel, J. R., J. I. Hedges, A. H. Devol, J. E. Richey, andM. N. G. Ribeiro. 1986. Dissolved humic substances of the Amazon River system.Limnology and Oceanography 31:739–754.
Fahnenstiel, G. L., M. Marcovitz, M. J. McMcormick, D. G. Redalje, S. E. Lohrenz, H. Carrick, andM. J. Dagg. 1992. High growth and microzooplankton-grazing loss rates for phytoplankton populations from the Mississippi plume region, p. 111–116.In Nutrient Enhanced Coastal Ocean Productivity. Publication number TAMU-SG-92-109, Sea Grant Program, Texas A&M University, Galveston, Texas.
Ferguson, R. L., E. N. Buckley, andA. V. Palumbo. 1984. Response of marine bacterioplankton to differential filtration and confinement.Applied and Environmental Microbiology 47: 49–55.
Findlay, S., M. L. Pace, D. Lints, andK. Howe. 1992. Bacterial metabolism of organic carbon in the tidal freshwater Hudson estuary.Marine Ecology Progress Series 89:147–153.
Friederich, G. E., P. Sherman, andL. A. Codispoti. 1984. A high precision automated Winkler titration based on an HP-85 computer, a simple colorimeter, and an inexpensive electrochemical Report No. 42. Bigelow Laboratory for Ocean Science. Westbooth Bay Harbor, Maine.
Fuhrman, J. A. andT. M. Bell. 1985. Biological considerations in the measurement of dissolved free amino acids in seawater and implications for chemical and microbiological studies.Marine Ecology Progress Series 25:13–21.
Gardner, W. S. 1978. Microfluorometric method to measure ammonium in natural waters.Limnology and Oceanography 23: 1069–1072.
Gardner, W. S., J. F. Chandler, andG. A. Laird. 1989. Organic nitrogen mineralization and substrate limitation of bacteria in Lake Michigan.Limnology and Oceanography 34:478–485.
Gardner, W. S., J. F. Chandler, G. A. Laird, andH. J. Carrick. 1987. Sources and fate of dissolved free amino acids in epilimnetic Lake Michigan water.Limnology and Oceanography 32: 1353–1362.
Gardner, W. S., J. B. Cotner, Jr., andL. R. Herche. 1993. Chromatographic measurement of nitrogen mineralization rates in marine coastal waters with15N.Marine Ecology Progress Series 93:65–73.
Gardner, W. S. andP. A. St. John 1991. High-performance liquid chromatographic method to determine ammonium ion and primary amines in seawater.Analytical Chemistry 63: 537–540.
Goldman, J. C., D. A. Caron, andM. R. Dennett. 1987. Regulation of gross growth efficiency and ammonium regeneration in bacteria by substrate C∶N ratio.Limnology and Oceanography 32:1239–1252.
Grill, E. V. andF. A. Richards. 1964. Nutrient regeneration from phytoplankton decomposing in sea water.Journal of Marine Research 22:51–69.
Harper, D. E., Jr.,L. D. McKinney, R. R. Salzer, andR. J. Case. 1981. The occurrence of hypoxic bottom water off the upper Texas coast and its effect on the benthic biota.Contributions in Marine Science 24:53–79.
Harrison, W. G. 1978. Experimental measurements of nitrogen remineralization in coastal waters.Limnology and Oceanography 23:684–694.
Jahnke, R. A., S. R. Emerson, andJ. W. Murray. 1982. A model of oxygen reduction, denitrification, and organic matter mineralization in marine sediments.Limnology and Oceanography 27:610–623.
Keil, R. G. andD. L. Kirchman. 1991. Contribution of dissolved free amino acids and ammonium to the nitrogen requirements of heterotrophic bacterioplankton.Marine Ecology Progress Series 73:1–10.
Kirchman, D. L., Y. Suzuki, C. Garside, andH. W. Ducklow. 1991. High turnover rates of dissolved organic carbon during a spring phytoplankton bloom.Nature 352:612–614.
Kirchman, D. L., R. G. Keil, andP. A. Wheeler. 1989. Carbon limitations of ammonium uptake by heterotrophic bacteria in the subarctic Pacific.Limnology and Oceanography 35:1258–1266.
Kroopnick, P. 1974. The dissolved O2−CO2−13C system in the eastern Pacific.Deep-Sea Research 21:211–227.
Lohrenz, S. E., M. J. Dagg, andT. Whitledge. 1990. Enhanced primary production at the plume/oceanic interface of the Mississippi River.Continental Shelf Research 10:639–664.
Lohrenz, S. E., D. G. Redalje, G. L. Fahnenstiel, andG. A. Lang. 1992. Regulation and distribution of primary production in the northern Gulf of Mexico, p. 95–104.In Nutrient Enhanced Coastal Ocean Productivity. Publication number TAMU-SG-92-109, Sea Grant Program, Texas A&M University, Galveston, Texas.
Pavela, J. S., J. L. Ross, andM. E. Chittenden, Jr. 1983. Sharp reductions in abundance of fishes and benthic macroinvertebrates in the Gulf of Mexico off Texas associated with hypoxia.Northeast Gulf Science 6:167–173.
Porter, K. G. andY. S. Feig. 1980. The use of DAPI for identifying an counting aquatic microflora.Limnology and Oceanography 25:943–948.
Rabalais, N. M., R. E. Turner, andW. J. Wiseman, Jr. 1992. Distribution and characteristics of hypoxia on the Louisiana shelf in 1990 and 1991, p. 15–20.In Nutrient Enhanced Coastal Ocean Productivity. Publication number TAMU-SG-92-109, Sea Grant Program, Texas A&M University, Galveston, Texas.
Rabalais, N. M., R. E. Turner, W. J. Wiseman, Jr., and D. F. Boesch. 1991. A brief summary of hypoxia on the northern Gulf of Mexico continental shelf. 1985–1988, p. 35–47.In R. V. Tyson and T. H. Pearson (eds.), Modern and Ancient Continental Shelf Anoxia. Geological Society Special Publication No. 58. London.
Riley, G. A. 1937. The significance of the Mississippi River drainage for biological conditions in the northern Gulf of Mexico.Journal of Marine Research 1:60–74.
Sharp, J. H. 1983. The distribution of inorganic nitrogen and dissolved and particulate organic nitrogen in the sea, p. 1–35.In E. J. Carpenter and D. G. Capone (eds.), Nitrogen in the Marine Environment. Academic Press, New York.
Simon, M. andF. Azam. 1989. Protein content and protein synthesis rates of planktonic marine bacteria.Marine Ecology Progress Series 51:201–213.
Sklar, F. H. andR. E. Turner. 1981. Characteristics of phytoplankton production off Barataria Bay in an area influenced by the Mississippi River.Contributions in Marine Science 24:93–106.
Turner, R. E. andR. L. Allen. 1982. Bottom water oxygen concentration in the Mississippi River Delta Bight.Contributions in Marine Science 25:161–172.
Turner, R. E. andN. N. Rabalais. 1991. Changes in Mississippi River water quality this century.Bioscience 41:140–147.
von Brand, T., N. W. Rakestraw, andC. E. Renn. 1937. The experimental decomposition of nitrogenous organic matter in seawater.Biological Bulletin of Woods Hole 72:165–175.
Von Brand, T., N. W. Rakestraw, andW. J. Zabor. 1942. Decomposition and regeneration of nitrogenous organic matter in sea water. V. Factors influencing the length of the cycle; Observations upon the gaseous and dissolved organic nitrogen.Biological Bulletin of Woods Hole 83:273–282.
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Gardner, W.S., Cotner, J.B., Eadie, B.J. et al. Mineralization of organic material and bacterial dynamics in Mississippi River plume water. Estuaries 17, 816–828 (1994). https://doi.org/10.2307/1352750
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DOI: https://doi.org/10.2307/1352750