|Biogeochemical cycling of sulfur and organic matter in
focuses on the role of microorganisms in the cycling of organic matter
and important elements such as sulfur and nitrogen in aquatic systems.
A major focus of
my research program is the biogeochemical cycling of dimethylsulfide (DMS)
and its precursor dimethylsulfoniopropionate (DMSP) in the marine
water column. We carry out this research in local waters but also on
oceanographic cruises all over the world. This field continues to broaden as we have discovered new and
important roles for DMSP and its degradation products in the marine
ecosystem. DMSP is
produced by many, but not all, marine algae who use it as an osmotic
solute and potentially an antioxidant. DMSP is degraded by microorganisms to volatile DMS which is a
major source of sulfur to the atmosphere. This input of DMS to the atmosphere significantly affects
atmospheric chemistry (especially the pH of precipitation) and also
the global climate system because DMS is oxidized to sulfate aerosols
(tiny crystals of salt). Sulfate
aerosols affect climate by directly reflecting solar radiation back to
space and by serving as cloud condensation nuclei, which in turn
affect how clouds reflect solar radiation.
Here are some
brief highlights of ongoing projects.
The role of DMSP
as an antioxidant in marine algae – With funding from the NSF
Biological Oceanography program we are testing the hypothesis that
DMSP and its degradation products are important scavengers of reactive
oxygen species in cells of marine algae. We are using pure cultures of marine phytoplankton as well as
natural populations in seawater to study the physiological responses
of the algae to oxidative stresses. One of the responses we are particularly interested in is the
algal degradation of DMSP to DMS, catalyzed by DMSP lyase enzymes. We are examining the activity and regulation of DMSP lyase in
the oxidative stress physiology of the phytoplankton. With separate funding from EPA we are also examining the
oxidative stress physiology of the marsh grass Spartina alterniflora,
another DMSP producer.
cycling of DMSP and DMS in the Ross Sea, Antarctica – The Ross Sea
experiences a spectacular bloom of phytoplankton beginning in the
austral spring and extending into the austral summer. This bloom is composed mainly of Phaeocystis antarctica, a
prymnesiophyte alga that produces large amounts of DMSP. Previous
studies have documented extremely high concentrations of DMS in the
Ross Sea, but no process studies have been carried out. With funding from the NSF Office of Polar Programs, we will be
using an experimental approach and field sampling to examine the
factors which control DMSP and DMS production in these icy cold
waters. The 35S-DMSP and 35S-DMS tracer methods that we have developed
provide us with powerful tools to study DMSP/DMS cycling processes
under extreme conditions. We
are particularly interested in the impact of solar radiation (both
visible and ultraviolet) on the algal and bacterial communities that
are responsible for cycling DMSP/DMS. Solar UV radiation is an important factor in the Ross Sea
during the early bloom development because this area is within the
Antarctic Ozone Hole. Several
cruises to Antarctic waters are planned for the coming years.
of the global DMS cycle – The biogeochemical cycle of DMS in the
ocean involves many different types of organisms (algae, bacteria,
viruses, grazers) interacting in a complex web of ecological,
processes, all of which depend greatly on the geophysical and
biophysical conditions experienced by the plankton community. In turn, DMS emissions to the atmosphere can have an enormous
impact on atmospheric chemistry and climate with potential for
feedbacks on the plankton communities that produce DMSP and DMS. We are funded by the NSF Biocomplexity program to work with
other DMS specialists, food web modelers and climate modelers to
advance understanding of how the DMS cycle functions and how it
responds to forcings such as temperature, visible light, ultraviolet
radiation, nutrients, water column mixing depths and other factors. In addition to laboratory components, this project has two
major field components. The
first will be a month-long cruise to the Sargasso Sea near the Bermuda
Atlantic Time Series (BATS) station to investigate the late summer
“DMS paradox”, a period of high DMS concentrations when plankton
biomass is extremely low. The
second field study will be an extended time series and experimental
investigation of DMS cycling in the productive waters near the
Antarctic Palmer Peninsula.
ecology and carbon cycling in estuaries - With funding from the US EPA we have been studying the trophic
dynamics in the microbial food web of Mobile Bay, a large shallow
estuary on the US Gulf Coast. We are measuring the biomass, production
and growth efficiency of bacteria in the estuary. Field and laboratory experiments are being carried out to test
how temporal and spatial variations in sediment resuspension and
riverine DOC inputs influence the role of bacteria the trophic
transfers within the Bay ecosystem. The trophic status of the Bay (heterotrophic
vs. autotrophic) is being assessed to determine how efficient the
system is at processing nutrients and carbon and in transferring
energy up to the fish forage base.
Zubkov, M, L. J.
Linn, R. Amann and R. P. Kiene. Temporal patterns of
biological dimethylsulfide (DMS) consumption during laboratory-induced
phytoplankton bloom cycles. Marine Ecology Progress Series. In
Harada, H, M-A.
Rouse, W. Sunda and R. P. Kiene. Latitudinal and vertical
distributions of particle-associated DMSP lyase activity in the
western North Atlantic Ocean. Can.
J. Fish. Aquat. Sci. In Press.
Malmstrom, R R., R.
P. Kiene and D. L. Kirchman. Identification and enumeration
of marine bacteria assimilating dimethylsulfoniopropionate (DMSP) in
the north Atlantic and Gulf of Mexico. Limnology and Oceanography. In Press.
Stets, E G, M. E.
Hines and R. P. Kiene. 2004. Thiol methylation
potential in anoxic, low pH wetland sediments and its relationship
dimethylsulfide production and organic carbon cycling. FEMS
Microbiology Ecology. 47: 1-11.
Toole, D.A., D. J. Kieber, R. P. Kiene, D. A. Siegel, and N.B.
Photolysis and the dimethylsulfide (DMS) summer paradox in the
Sargasso Sea. Limnol.
Oceanogr. 48: 1088-1100.
Moran, M. A., J.
M. González, and R. P. Kiene. 2003. Linking a bacterial taxon to organic sulfur cycling
in the sea: studies of the marine Roseobacter group. Geomicrobiology Journal. 20:
Sunda, W., D. J.
Kieber, R. P. Kiene and S. Huntsman. 2002. An
antioxidant function for DMSP in marine algae. Nature 418: 317-320.
Zubkov, M. V., B.
M. Fuchs, S. D. Archer, R. P. Kiene, R. Amann and P. H. Burkill.
2002. Rapid turnover of dissolved DMS and DMSP by defined
bacterioplankton communities in the stratified euphotic zone of the
North Sea. Deep-Sea Res.Part II. 49: 3017-3038.
Hines, M. E., K.
N. Duddleston and R. P. Kiene. 2001.
Carbon flow to acetate and C1 compounds in high latitude wetlands. Geophysical Res. Lett. 28: 4251-4254.
Zubkov, M, B. M.
Fuchs, S.D. Archer, R. P. Kiene, R. Amann and P. Burkhill.
2001. Linking the composition of bacterioplankton to rapid
turnover of dissolved dimethylsulphoniopropionate in an algal bloom in
the North Sea. Environ. Microbiol. 3: 304-311.
Kiene, R. P. and L. Linn. 2000. The fate of dissolved
dimethylsulfoniopropionate (DMSP) in seawater: Tracer studies using 35S-DMSP. Geochim. Cosmochim. Acta. 64:
Kiene, R. P. and L. J. Linn. 2000. Turnover of dissolved DMSP
and its relationship with bacterial production in the Gulf of Mexico. Limnol. Oceanogr. 45(4): 849-861.
R. P., L. J. Linn and J. A. Bruton. 2000. New and important
roles for DMSP in marine microbial communities. J. Sea Res. 43:
Kiene, R.P., P.T. Visscher, G.O. Kirst and M.D. Keller (Eds.). 1996.
Biological and Environmental Chemistry of DMSP and
related sulfonium compounds. Plenum Publishing Corp., New
Current Research Grants
Foundation – Polar Programs-Antarctic Biology and Medicine. Impact of solar radiation and nutrients on biogeochemical
cycling of DMSP and DMS in the Ross Sea, Antarctica. (with David Kieber, SUNY ESF).
Foundation – Biocomplexity in the Environment. Complex molecular to global interactions and feedbacks in the
marine DMS cycle. (with
Patricia Matrai, Bigelow Laboratory, and several other PI’s).
Foundation – Biological Oceanography. Production and dynamics of DMSP and related compounds in
response to oxidative stress in marine phytoplankton. (with David Kieber, SUNY ESF).
Foundation – Microbial genetics. A genomic approach t sulfur biotransformations in the ocean:
the genome sequence of a marine Roseobacter. $51,118, sub-contract
from Univ. Georgia, under grant to Mary Ann Moran.
Protection Agency – Alabama Center for Estuarine Studies. Oxidative
stress protection by dimethylsulfoniopropionate(DMSP) in Spartina
Daniel Husband (Ph.D.)
Daniela del Valle (M.S.)
Hyakubun Harada (Ph.D.)
Jody Bruton (Ph.D.)