Silica production in the Sargasso Sea during spring 1989

Abstract

Profiles of silicic acid, chlorophyll a, biogenic silica, and lithogenic silica concentrations and the rate of sllica production were obtained from 7 depths in the upper 100 to 200 m at 8 stations in the western Sargasso Sea between May 7 and 18. 1989 Stations were distnbuted from the southern edge of the Gulf Stream to about 400 km south of Bermuda An additional set of profiles was obtained at Stn S near Bermuda on March 28 1989 Sillcic acid concentrations in the euphotic zone xvere generally between 0 6 and 0 9 pM Blogenic sillca concentrations ranged from 7 to 1400 nmol S1 1-' with concentratlons c 5 0 nmol S1 1-' being typical of stations south of 35" N well away from the Gulf Stream and its eddies Specific production rates of biogenic silica (V, were in the same range as those reported for the picophytoplankton In the Sargasso Sea s u g g e s t~n g that diatoms can gioxv as fast as the more numerous plcophytoplankton in oligotrophic oceans Subsurface maxima in biogenic silica concentration, chlorophyll biomass and silica production rates were observed neai the top of the nitracl~ne at 7 of the 9 stations Integrated silica production rates between the surface and the 0 1 % light depth were generally betxveen 0 2 and 0 7 inmol Si m -d-l with an aveiage of 47 % of that production occurring within the nitracline If diatoms taking up silicic acid xvithin the nitracline also ut~lize nitrate, they may account for between 0 56 and 0 84 m01 C m-' yr.' of nexv production lvhich is 16 to 24 % of the estimated annual total new production for the region)

Revisiting silicon budgets at a tropical continental shelf: Silica standing stocks in sponges surpass those in diatoms

“…Such a sponge dominance cannot be attributed to impoverished environments in terms of either nutrients or phytoplankton. Both silicate and plankton bSi concentrations fell within the range of values measured for other nonoligotrophic, subtropical, and temperate coastal zones lacking large river plumes (Ragueneau et al 2005) and were notably higher than those typically recorded from offshore subtropical systems (Brzezinski and Kosman 1996;Sarmiento and Gruber 2006). The portion of the Mesoamerican shelf we studied was relatively shallow, favoring a low contribution of diatoms to the regional budget.…”

Deep silicon maxima in the stratified oligotrophic Mediterranean Sea

“…Nonetheless, the DSM is a feature that has been observed in several other oceanic systems worldwide in recent years, in the oligotrophic environment of the Sargasso Sea (Brzezinski and Kosman;, Krause et al, 2009a and gyres of the Equatorial and Central North Pacific (Blain et al, 1997;Brzezinski et al, 1998;Scharek et al, 1999, Dore et al, 2008. This feature has also been recurrently observed in the Southern Ocean but with often much higher biogenic silica concentrations (Quéguiner, 2001;Leblanc et al, 2002;Quéguiner and Brzezinski, 2002;Beucher et al, 2004;Mosseri et al, 2008).…”

Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps

“…Krause et al (2008) measured bSiO 2 silica production rates during this study using the 32 Si tracer and incubation method described by Brzezinski and Phillips (1997) and Brzezinski et al (2001). Depth integrated (0 -140 m) bSiO 2 production rates averaged 1.03 ± 0.96 (n = 17) and 2.28 ± 2.06 (n = 9) mmol Si m -2 d -1 for the West and East Transects, respectively, a substantial increase over previous Sargasso Sea measurements (Brzezinski and Kosman, 1996;Brzezinski and Nelson, 1995;Nelson and Brzezinski, 1997). For example, Nelson and Brzezinski (1997) in a three year study (1992)(1993)(1994) at BATS.…”