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.

Measurement of visible light absorption by particulate matter in the ocean1

Abstract: For the measurement of visible light absorption by particles in sea water, optical arrangements have been devised where scattered light is integrated and the photodetector “sees” mostly diffused light. High spectral resolution has been obtained by removing particulate matter from sea water using a membrane filter and scanning the filter against an unused filter as the reference blank in the Cary spectrophotometer. In this fashion spectral curves for particulate matter in the oceans have been obtained. These curves show pigment banding in the upper 100 m of water characteristic of absorption by chloroplastic pigments. Below this depth the absorption of particulate matter is characterized by a gradual increasing attenuation from long to short wavelengths. Optical density ratios of chloroplastic pigment bands seen in the particulate matter of the upper 100 m suggest the presence of absorbing components not generally seen in algal cultures. Differential filtration through graded filter sizes (5.0 µ-0.3 µ) followed by the spectral scanning of filters, shows that practically all of the chloroplastic pigments are retained by the 5.0 µ filter. Particles passing this filter show little selective attenuation of visible wavelengths. The nature of sea water particulate matter is discussed in terms of its absorbing characteristics as well as the significance to phytoplankton ecology.

Assessment of a δ15N Isotopic Method to Indicate Anthropogenic Eutrophication in Aquatic Ecosystems

Abstract: Increased anthropogenic delivery of nutrients to water bodies, both freshwater and estuarine, has caused detrimental changes in habitat, food web structure, and nutrient cycling. Nitrogen-stable isotopes may be suitable indicators of such increased nutrient delivery. In this study, we looked at the differences in response of macrophyte delta15N values to anthropogenic N across different taxonomic groups and geographic regions to test a stable isotopic method for detecting anthropogenic impacts. Macrophyte delta15N values increased with wastewater input and water-column dissolved inorganic nitrogen (DIN) concentration. When macrophytes were divided into macroalgae and plants, they responded similarly to increases in wastewater N, although macroalgae was a more reliable indicator of both wastewater inputs and water-column DIN concentrations. Smooth cordgrass (Spartina alterniflora Loisel.) Delta15N increased uniformly with wastewater inputs across a geographic range. We used the relationship derived between S. alterniflora and relative wastewater load to predict wastewater loads in locations lacking quantitative land use data. The predictions matched well with known qualitative information, proving the use of a stable isotopic method for predicting wastewater input.

Microbially mediated cerium oxidation in sea water

Abstract: REDOX processes influence the geochemistry of many elements in the ocean, but attributing the distribution of these elements in the water column and sediments to specific redox processes is difficult because they are also influenced by non-redox processes and by other inputs that are poorly constrained. Cerium provides an opportunity to study redox processes in the ocean1–5 because its redox chemistry leads to its enrichment or depletion ('cerium anomalies') with respect to its lanthanide neighbours. A detailed understanding of Ce geochemistry is lacking, however, because of the paucity of knowledge of the redox rates and mechanisms in natural waters. Here I report measurements of Ce(III) oxidation rates using radiotracers in seawater samples collected in the Sargasso Sea and in Vineyard Sound, Massachussetts, which are much faster than previous, indirect estimates1. The data indicate that the negative Ce anomaly in sea water is the result of microbial oxidation followed by preferential scavenging of Ce(IV); no abiotic oxidation was detectable. This suggests that inhibition by sunlight of microbial oxidation and scavenging of Ce and Mn contribute to the pronounced surface maxima observed for these elements.