Woods Hole Oceanographic Institution

About: Woods Hole Oceanographic Institution is a nonprofit organization based out in Falmouth, Massachusetts, United States. It is known for research contribution in the topics: Population & Mantle (geology). The organization has 5685 authors who have published 18396 publications receiving 1202050 citations. The organization is also known as: WHOI.

Geochemical perspectives on coral mineralization

Abstract: Corals open an exceptional window into many phenomena of geological, geochemical, climatic, and paleontological interest. From the Paleozoic to the present, corals provide some of the finest high-resolution archives of marine conditions. Corals are likewise exceptional for chronometric purposes, and even the terrestrial 14C timescale has now been calibrated against coral 230Th/234U. Corals also represent a testing ground for basic ideas about mineralogy and geochemistry. The shapes, sizes, and organization of skeletal crystals have been attributed to factors as diverse as mineral supersaturation levels and organic mediation of crystal growth. The coupling between calcification and photosynthesis in symbiotic corals is likewise attributed to everything from photosynthetic alkalinization of the water, to efforts by the coral to prevent photosynthetic alkalinization. Corals also leave a significant geochemical imprint on the oceans. Their aragonite skeletons accept about 10 times more strontium than does calcite, hence the proportion of marine aragonite precipitation affects the oceanic chemical balance. Biological carbonates represent the biosphere’s largest carbon reservoir, hence calcareous organisms affect the ocean’s pH, CO2 content, and ultimately global temperatures through the greenhouse gas connection. Finally, corals present some geochemical puzzles for ecology and conservation. How do symbiotic corals obtain nutrients in some of the most nutrient deficient parts of the planet? Are global geochemical changes partially responsible for the widespread declines in coral reefs during recent decades? We will address many of these issues, but will concentrate on coral skeletal structure and calcification mechanism. These topics bear most directly on the biomineralization process and generally affect the choice of skeletal materials and analytical techniques used in geochemical investigations. The coral reef is probably the planet’s most spectacular biomineralization product. These grand and complex ecosystems build on the accumulated skeletal debris of countless generations of organisms, especially calcareous algae and symbiotic …

Homogenization of potential vorticity in planetary gyres

Abstract: The mean circulation of planetary fluids tends to develop uniform potential vorticity q in regions where closed time-mean streamlines or closed isolines of mean potential vorticity exist. This state is established in statistically steady flows by geostrophic turbulence or by wave-induced potential-vorticity flux. At the outer edge of the closed contours the expelled gradients of q are concentrated. Beyond this transition lies motionless fluid, or a different flow regime in which the planetary gradient of q may be dominant. The homogenized regions occur where direct forcing by external stress or heating within the closed isoline is negligible, upon the potential-density surface under consideration. In the stably stratified ocean such regions are found at depths greater than those of direct wind-induced stress or penetrative cooling. In ‘channel’ models of the atmosphere we again find constant q when mesoscale eddies cause the dominant potential-vorticity flux. In the real atmosphere the results here can apply only where internal heating is negligible. The derivations given here build upon the Prandtl–Batchelor theorem, which applies to non-rotating, steady two-dimensional flow. Supporting evidence is found in numerical circulation models and oceanic observations.

Sulfate reduction in a New England salt marsh1

Abstract: Sulfate reduction rates were measured for 2 years in the peat of a salt mars by a radiotracer technique. Rates are high throughout the peat, from the surface to more than 20 cm deep. The integrated annual rate is about 75 mol SO/sub 4//sup 2 -/.m/sup -2/.yr/sup -1/, the highest yet reported for any natural ecosystem. Sulfate reduction accounts for the consumption of 1800 g org-C.m/sup -2/.yr/sup -1/, about equal to net primary production in the marsh. Respiration using other electron acceptors (such as oxygen or nitrate) is much less important. Sulfate reduction rates in the peat of the salt marsh are probably high for at least three reasons: the belowground production of Spartina alterniflora provides a large, annual input of organic substrates over a depth of some 20 cm; sulfate is rapidly resupplied to the peat in infiltrating tidal waters, so that sulfate depletion never limits the rate of reduction; and sulfide concentrations remain below toxic levels. The stable pyrite (FeS/sub 2/) is a major end product of sulfate reduction in the marsh peat while iron monosulfide (FeS) is not. If the incorporation of /sup 35/S into pyrite were not measured, the (/sup 35/S)SO/sub 4//sup 2 -/ reduction measurements more » would greatly underestimate the true rate of sulfate reduction. Pyrite acts largely as a temporary store of reduced sulfur, with seasonal changes in its concentration. « less

A kinetic approach to the effect of temperature on algal growth1

Abstract: A simple model incorporates the combined effects of temperature and nutrient limitation on the growth rate of algae. The temperature function is described by the Arrhenius equation and the nutrient relationship with the Monod model. The Arrhenius equation is inserted into the Monod model for the maximum growth rate µ, so that the growth rate is described by the product of temperature and nutrient expressions. The utility of the Arrhenius equation in describing the effect of temperature on µ for phytoplankton is tested with data from the literature on continuous culture experiments with freshwater and marine algae; the Arrhenius model describes the relationship between µ and temperature extremely well. Several restrictions to widespread use of the model limit its application to laboratory studies, but its general concepts may apply to natural water situations.