Deep-Sea Research II 48 (2001) 1405}1447 Overview of the US JGOFS Bermuda Atlantic Time-series Study (BATS): a decade-scale look at ocean biology and biogeochemistry Deborah K. Steinberg*, Craig A. Carlson, Nicholas R. Bates, Rodney J. Johnson, Anthony F. Michaels, Anthony H. Knap Bermuda Biological Station for Research, Inc., Ferry Reach, St. George's GE01, Bermuda USC Wrigley Institute for Environmental Studies, University of Southern California, Los Angeles, CA 90089, USA Abstract The Bermuda Atlantic Time-series Study (BATS) commenced monthly sampling in October 1988 as part of the US Joint Global Ocean Flux Study (JGOFS) program. The goals of the US JGOFS time-series research are to better understand the basic processes that control ocean biogeochemistry on seasonal to decadaltime-scales,determinetheroleoftheoceansintheglobalcarbonbudget,andultimatelyimproveour ability to predict the e!ects of climate change on ecosystems. The BATS program samples the ocean on abiweeklytomonthlybasis,astrategythatresolvesmajorseasonalpatternsandinterannualvariability.The corecruiseslast4}5dduringwhichhydrography,nutrients,particle #ux,pigmentsandprimaryproduction, bacterioplankton abundance and production, and often complementary ancillary measurements are made. This overview focuses on patterns in ocean biology and biogeochemistry over a decade at the BATS site, concentrating on seasonal and interannual changes in community structure, and the physical forcing and other factors controlling the temporal dynamics. Signi"cant seasonal and interannual variability in phyto- plankton and bacterioplankton production, biomass, and community structure exists at BATS. No strong relationship exists between primary production and particle #ux during the 10yr record, with the relation- ship slightly improved by applying an arti"cial lag of 1 week between production and #ux. The prokaryotic picoplankton regularly dominate the phytoplankton community; diatom blooms are rare but occur period- icallyintheBATStimeseries.TheincreaseinChl a concentrationsduringbloomperiodsisduetoincreases bymostofthetaxapresent,ratherthanbyanysinglegroup,andthereisseasonalsuccessionofphytoplank- ton. The bacterioplankton often dominate the living biomass, indicating the potential to consume large amounts of carbon and play a major ecological role within the microbial food web. Bacterial biomass, production, and speci"c growth rates are highest during summer. Size structure and composition of the * Correspondingauthor.Presentaddress:VirginiaInstituteofMarineScience,CollegeofWilliamandMary,P.O.Box 1346, Gloucester Pt, VA 23062, USA. Fax: #1-804-684-7293. E-mail address: debbies@vims.edu (D.K. Steinberg). 0967-0645/01/$-see front matter  2001 Published by Elsevier Science Ltd. PII:S0967-0645(00)00148-X