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.

Abrupt tropical vegetation response to rapid climate changes.

Abstract: Identifying leads and lags between high- and low-latitude abrupt climate shifts is needed to understand where and how such events were triggered Vascular plant biomarkers preserved in Cariaco basin sediments reveal rapid vegetation changes in northern South America during the last deglaciation, 15,000 to 10,000 years ago Comparing the biomarker records to climate proxies from the same sediment core provides a precise measure of the relative timing of changes in different regions Abrupt deglacial climate shifts in tropical and high-latitude North Atlantic regions were synchronous, whereas changes in tropical vegetation consistently lagged climate shifts by several decades

Fluvial landscapes of the Harappan civilization

Abstract: The collapse of the Bronze Age Harappan, one of the earliest urban civilizations, remains an enigma. Urbanism flourished in the western region of the Indo-Gangetic Plain for approximately 600 y, but since approximately 3,900 y ago, the total settled area and settlement sizes declined, many sites were abandoned, and a significant shift in site numbers and density towards the east is recorded. We report morphologic and chronologic evidence indicating that fluvial landscapes in Harappan territory became remarkably stable during the late Holocene as aridification intensified in the region after approximately 5,000 BP. Upstream on the alluvial plain, the large Himalayan rivers in Punjab stopped incising, while downstream, sedimentation slowed on the distinctive mega-fluvial ridge, which the Indus built in Sindh. This fluvial quiescence suggests a gradual decrease in flood intensity that probably stimulated intensive agriculture initially and encouraged urbanization around 4,500 BP. However, further decline in monsoon precipitation led to conditions adverse to both inundation- and rain-based farming. Contrary to earlier assumptions that a large glacier-fed Himalayan river, identified by some with the mythical Sarasvati, watered the Harappan heartland on the interfluve between the Indus and Ganges basins, we show that only monsoonal-fed rivers were active there during the Holocene. As the monsoon weakened, monsoonal rivers gradually dried or became seasonal, affecting habitability along their courses. Hydroclimatic stress increased the vulnerability of agricultural production supporting Harappan urbanism, leading to settlement downsizing, diversification of crops, and a drastic increase in settlements in the moister monsoon regions of the upper Punjab, Haryana, and Uttar Pradesh.

Growth limitation of a coastal diatom by low zinc ion activity

Abstract: THE total zinc concentration in unpolluted marine waters has been reported to be in the 10−10 M range1. Such low concentration of an essential micronutrient suggests that the growth of some phytoplankton may be zinc limited. Of the trace metals necessary for phytoplankton growth, only iron has been considered a potential limiting micronutrient in the marine environment2,3. On the basis of laboratory work which focused mostly on copper, it is well known that the toxicity of a trace metal depends on its chemical speciation and can be related uniquely to its free ion activity4,5. However, it has not been established unequivocally that the availability of some metals may also be controlled by their free ion activities and may thus be depressed by organic complexation. Here we report laboratory experiments demonstrating that the zinc ion activity (rather than the total zinc concentration) can limit the growth rate of a coastal diatom Thalassiosira weissflogii (Grun. = T. fluviatalis Hust.) and that the limitation occurs at zinc ion activities which would be present in unpolluted seawater if any organic complexation of zinc were taking place.

Synchronous deglacial overturning and water mass source changes.

Abstract: Understanding changes in ocean circulation during the last deglaciation is crucial to unraveling the dynamics of glacial-interglacial and millennial climate shifts. We used neodymium isotope measurements on postdepositional iron-manganese oxide coatings precipitated on planktonic foraminifera to reconstruct changes in the bottom water source of the deep western North Atlantic at the Bermuda Rise. Comparison of our deep water source record with overturning strength proxies shows that both the deep water mass source and the overturning rate shifted rapidly and synchronously during the last deglacial transition. In contrast, any freshwater perturbation caused by Heinrich event 1 could have only affected shallow overturning. These findings show how changes in upper-ocean overturning associated with millennial-scale events differ from those associated with whole-ocean deglacial climate events.

Steady state growth and ammonium uptake of a fast‐growing marine diatom 1

Abstract: A fast-growing marine diatom Thalassiosira pseudonana (3H) was grown under NH4+-limited steady state conditions in continuous culture. Growth rate could not be described as a function of external or residual NH,+ because of analytical limitations in measuring NHd+ concentrations co.03 pg-atom N * liter -‘. Neither did the data fit the internal nutrient model of Droop because the washout growth rate (I;) under N limitation is substantially less than the maximum growth rate term used in the Droop expression (p). The ratio of the minimum (ka) to the maximum ( Qm) cell quota was the key term in determining the ratio fi:&, and hence the applicability of the Droop expression. For limiting nutrients such as vitamin Blz and P, @ - p, and the expression is applicable; but, when fi < pi, as for N and Si, the usefulness of the expression is diminished, and when p + 00, as for inorganic carbon, the Droop equation is completely invalid. In a general sense the usefulness of the Droop expression diminishes as the limiting nutrient:cell weight ratio increases. The generality of the concept of cell “shift UP, ” or increasing k, and p with increasing growth rate, is questioned as no evidence for this phenomenon was found in T. pseudonana. Moreover, the demonstration of discontinuities in kinetic curves of Q vs. /.L does not a priori imply that the coefficients kR and I; are variable.