The compensation depth ([Z.sub.c]), defined as the depth at which gross photosynthetic carbon fixation balances phytoplankton respiratory losses over one day, representing the lower boundary of the euphotic zone (Falkowski & Raven, 2007), was calculated via the expression:
6 Latitude ([degrees]N) 21.50 21.50 Longitude ([degrees]W) 92.50 92.25 Profile time (GMT-6, h:min) 11:39 13:36 Total depth (m) 264 74 Euphotic layer thickness (m) 90 70 Average extinction coefficient (k) 0.23 0.16 Incident irradiance [E.sub.0], ([micro]mol [m.sup.-2] [s.sup.-1]) 272.40 175 Compensation depth, [Z.sub.c] (m) 8.58 10.97 Critical depth [Z.sub.cr] (m) 9.54 13.64 Mixed layer (m) 15 20 Integrated chlorophyll (mg [m.sup.-2]) 2.70 1.70 Maximum chlorophyll depth (m) 76 58 Chlorophyll at the maximum (mg [m.sup.-3]) 0.20 0.40 Irradiance at chlorophyll maximum (%) 1.60 3.60 Upwelling radiance ([L.sub.u](chla) (nE [m.sup.-2] [s.sup.-1] [str.sup.-1]) at 2.80 0.31 the chlorophyll maximum The temperature at the chlorophyll maximum ([degrees]C) 22 22 St.
During much of the Cretaceous time, sea level was at its high level coupled with shoaling of carbonate compensation depth
; however the latest Cretaceous oceans were having relatively shallow carbonate compensation depth
(Thierstein, 1979; Arthur et al., 1985) because of the water stratification.
Backman, "Late Cenozoic carbonate accumulation and the history of the carbonate compensation depth in the western equatorial Indian Ocean," in Proceedings of the ODP (Ocean Drilling Program), Scientific Results, Leg115, College Station, TX, R.
Hempel, "Cenozoic carbonate accumulation and compensation depth changes in the Indian Ocean," in Synthesis of Results from Scientific Drilling in the Indian Ocean, R.
"The overall balance of these processes is reflected in the deep ocean's carbonate compensation depth, the CCD," the MARUM scientist continues.
Today, the Pacific carbonate compensation depth is at 4.5 km.
All five samples were taken from places under the compensation depth
situated around 4200 m in this part of the Pacific Ocean.