Production Of Particulate Organic Matter Research Articles

Ontogcnetic vertical migration in Sebastolobus altivelis as a mechanism for transport of particulate organic matter at continental slope depths

Ontogenetic vertical migration by a demersal fish inhabiting the continental slope off central California was studied as a mechanism for coupling transport of particulate matter between surface waters and the bathyal sea floor. We conducted a 1‐yr survey of Sebastolobus altivelis, a dominant demersal fish, over much of its depth range (400–1,600 m), with a camera sled and bottom trawl. This scorpaenid spawns gelatinous masses of eggs which float to the surface. After hatching, S. altivelis has a protracted pelagic phase and settles as a benthic juvenile at a length of ∼55 mm. We determined the production of particulate organic matter (POM) in masses of eggs as a measure of the passive upward flux of POM, and the recruitment of POM by settling juveniles as a measure of active transport back to the sea floor. Upward and downward fluxes of particulate organic carbon (POC) associated with planktonic development and ontogenetic migration of S. altivelis were 4.1–5.8 and 3.0–5.5 mg C m−2 yr−1. These upward and downward fluxes are lower by factors of ∼10 and ∼104 than the reported passive upward and downward fluxes measured with particulate interceptor traps in the eastern North Pacific. These data suggest that at bathyal depths, it is unlikely that vertical ontogenetic migrations contribute >1% to the POC flux reaching the deep‐sea floor. The upward flux of POC as buoyant eggs could represent, however, a significant portion of the total upward flux.

Vertical flux and biogeochemical turnover regulate nutrient limitation of net organic production in the North Pacific Gyre

Water samples collected at a station in the North Pacific Gyre near Hawaii precisely define the temporal average vertical profile of dissolved inorganic and organic N and P (DON and DOP). DON and DOP concentrations decrease with depth. As shown by other studies, the regression of NO3− (with or without NH4−) vs. PO43− yields an approximately Redfield slope and a negative nitrogen intercept. If DON and DOP are included in the regression equation, the intercept approaches 0.Vertical flux ratios of dissolved materials are calculated with a one‐dimensional diffusion model. Downward mixing of DON offsets about 6% of the upward NO3− flux; downward DOP mixing offsets only about 4% of the upward PO43− flux. Net production of particulate organic matter in the euphotic zone is N limited because of slow biochemical turnover of dissolved organic N relative to that of dissolved organic P and to downward mixing.

RELEASE OF DISSOLVED ORGANIC MATTER BY MARINE PHYTOPLANKTON IN COASTAL AND OFFSHORE AREAS OF THE NORTHEAST PACIFIC OCEAN1

The rate of release of dissolved organic matter during phytoplankton photosynthesis was measured in eutrophic and oligotrophic areas of the Northeast Pacific Ocean. A method using liquid scintillation counting techniques is described that allows sample preparation to be done simply and accurately at sea. The absolute amounts of dissolved organic matter release were generally greatest near the surface and in eutrophic waters, but relative to total production were greatest in oligotrophic areas. A close correlation was found between the production of particulate organic matter and the release of dissolved organic matter.