2 research outputs found
Stoichiometry of the degradation of dissolved and particulate biogenic organic matter in the NW Iberian upwelling
The average composition of the dissolved and particulate products of early
degradation of marine phytoplankton has been established for the first time in a coastal
upwelling system using a mixing analysis along isopycnal surfaces combined with a
stoichiometric model. About 17â18% of the mineralized organic matter is derived
from the decomposition of organic particulates, and 16â35% is from the dissolved
organic matter. The remaining 50â70% is derived probably from large fast sinking
particles. On average, the mineralized material on large particles has the closest
composition to the Redfield formula. The ratio of dissolved saccharides to dissolved
organic matter respiration is >40% higher than expected from a material of Redfield
composition. Finally, the ratio of lipid to particulate organic matter respiration is >80%
larger than expected from a material of Redfield composition. Regarding the
decomposition of hard structures, biogenic silica dissolves predominantly in the inner
shelf, where organic carbon oxidation is more intense, and diatom deposition occurs
preferentially
Formation of the Alboran oxygen minimum zone
8 pĂĄginas, 6 figuras, 1 tabla.The enhanced oxygen minimum in the western Alboran Sea is the result of a chain of
processes starting with nutrient injection into the inflowing Atlantic water at the Strait of
Gibraltar. These nutrients originate in the outflowing Levantine Intermediate Water, outflowing
Mediterranean deep water, and inflowing North Atlantic Central Water (from 200 m). They are
injected into the inflowing Atlantic surface water by strong mixing at the eastern end of the Strait.
They move with Atlantic surface waters along the Spanish coast, mix with nutrients upwelling in
the northwestern Alboran Sea and stimulate phytoplankton productivity. The organic matter
produced by this mechanism is transported both with the anticyclonically flowing waters of the
AIboran gyre and with the waters that converge at the center of the gyre. Sedimentation in this
convergence zone helps to deliver this organic matter to the Levantine Intermediate Water where
bacteria metabolize it to CO2 at the expense of the existing oxygen. This mechanism develops the
most intense oxygen minimum zone in the Mediterranean Sea.This work was supported by ONR contract N00014-85-C-0230, NSF grants OCE 8316610
and INT 8212505 (to TYP), CNRS GRECO 24 (to HJM), and a fellowship from the U.S.-Spain
Joint Committee for Scientific Cooperation (to RM). This is Bigelow Laboratory for Ocean Science
Contribution No. 86034.Peer reviewe