Deep-Sea Res-earch, Vol. 34, Nos 5/6, pp. 1007-1026. 1987. 0198~)149/87 $3.00 + 0.00 Printed in Great Britain. © 1987Pergamon Journals 1 td. Verification of flux measurements made with in s#u benthic chambers ALLAN H. DEVOI.* (Received 15 October 1985; in rel,'isedlorm 16 May 1986: acc¢Tm'd 10 Jtdv 1986) Abstract--Exchange of solutes between the sediments and overlying water was measured in situ at two locations where the overlying waters were devoid of dissolved oxygen (Skan Bay, Alaska and the Tres Marias depression on the Mexican continental shell). Measurements were made with a tripod capable of collecting eight sequential samples for analysis of dissolved gases and ions. The tripod also permitted tracer injection and the rctrieval of scdimcnts underlying the llux chambers. Because of the absence of oxygen, sediments from these areas dM not contain benthic faunal populations, and it was possible to compare the benthic fluxes measured with thc tripod with those calculated from pore water proliles. For solutes for which exchange was not limited b~, resistance in the diffuse sublayer (alkalinity, St(OH)4, NH~, and PO:] ), the 1 1 tripod-measured fluxes agreed with those calculated from pore water gtadicnts to within 25%. Benthic boundary layer thickness within the chambers as calculated from the initial rate of radiotracer uptake (tritiated water) varied from 405 to 605 p.m in stirred chambers. Measurcd rates of N()~ uptake were concordant with a boundary htyer thickness of 60~1 r, tln. INTRODUCTION I~r is becoming increasingly clear that solute exchange across the sediment-water interface is an important process in regulating the water colunm distributions and global cycles of many elements (ANDEaSEN and MALAtIOI=F, 1977; NIXON et al., 1980; ZHrZs- ('ttEL, 1980; CODISPOTI and CttRISTENSEN, 1985; JONES and MURRAY, 1985). It is also becoming clear that estimates of benthic fluxes derived from pore water profiles can be significantly in error due to enhanced exchange resulting from the activities of benthic organisms tALLER, 1981t; McCAFFREY et al., 1980; ALLER et al., 1985). The magnitude of this flux enhancement will be greater in continental shelf and slope sediments, where benthic infaunal populations are greater than in the open ocean. To determine rates of benthic solute exchange, oceanographers frequently turn to direct incubation of sediments and their overlying waters, either on deck or in sittt. Of primary concern with shipboard incubations, especially of samples from the deep sea, is the effect of decompression (SMITII, 1978: S,~lml and ItlNGA, 1983). To date most in sittt benthic flux measurements have been made in shallow waters where divers can place the chambers (McCAFFREY et al., 1980; Ntxo.x et al., 198t); ELDVRHEII~ et al., 1981; CALLI-'NI)AR and HAMMOND, 1982; FISlIER et al., 1982; EMERSON el al., 1984: Gat't-Bt~Land MARTENS, 1984; RUTGEt~SVAN DER LOk:H: et al., 1984; and others). Flux chambers have also been deployed in the deep sea (HINoA et al., 1979: SxllTtl et al., 1983: SA~TSC~U el al., 1984; BERELSON and HAMMOND, 1986). Despite the increasing use of benthic flux :': School of Oceanography, WB-10, University of Washington, Seattle, WA 98195. U.S.A. 1007