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.

SAR11 marine bacteria require exogenous reduced sulphur for growth

Abstract: An intriguing example of genome reduction has been found in SAR11 marine bacteria, the ubiquitous clade with the smallest known genome of all free-living heterotrophic cells. 'Normal' marine aerobic bacteria are known to use assimilatory sulphate reduction to acquire sulphur from the environment. But Candidatus Pelagibacter ubique, and other SAR11 microbes, are deficient in this key metabolic pathway. Instead they rely on reduced sulphur compounds in the environment. This identifies compounds such as DMSP and methionine as essential growth requirements for these large plankton populations, a potentially important factor in microbial population dynamics in the oceans. Marine aerobic bacteria are known to use assimilatory sulphate reduction to acquire sulphur from the environment. The abundant and ubiquitous SAR11 clade is shown to be deficient in this pathway and instead to rely on reduced sulphur components such as DMSP for growth. Sulphur is a universally required cell nutrient found in two amino acids and other small organic molecules. All aerobic marine bacteria are known to use assimilatory sulphate reduction to supply sulphur for biosynthesis, although many can assimilate sulphur from organic compounds that contain reduced sulphur atoms1,2,3. An analysis of three complete ‘Candidatus Pelagibacter ubique’ genomes, and public ocean metagenomic data sets, suggested that members of the ubiquitous and abundant SAR11 alphaproteobacterial clade are deficient in assimilatory sulphate reduction genes. Here we show that SAR11 requires exogenous sources of reduced sulphur, such as methionine or 3-dimethylsulphoniopropionate (DMSP) for growth. Titrations of the algal osmolyte DMSP in seawater medium containing all other macronutrients in excess showed that 1.5 × 108 SAR11 cells are produced per nanomole of DMSP. Although it has been shown that other marine alphaproteobacteria use sulphur from DMSP in preference to sulphate1,2, our results indicate that ‘Cand. P. ubique’ relies exclusively on reduced sulphur compounds that originate from other plankton.

Orientation by means of long range acoustic signaling in baleen whales

Abstract: With very few exceptions, whales are social animals. Even though they may be widely dispersed at some seasons, most species congregate in herds during some portion of the year. As a general rule, small, toothed whales form the largest herds, which frequently contain hundreds, and exceptionally tens of thousands, of animals, whereas the much larger baleen whales, when found in herds at all, most often travel in bands of less than 20 animals, with only occasional reports of herds of up to 1,000 animals or more.’ There has been considerable speculation on the functional significance of herd behavior in whales, but it seems unlikely that we will get any closer to understanding the role of herd behavior until we know more about what constitutes a herd. In general usage, the word “herd” seems to mean a group of animals that are in close enough proximity to offer visible evidence to an observer (usually on the deck of a boat) that their behavior is linked (i.e., they are swimming in the same direction, or breathing in rough synchrony, or feeding in the same area or resting together, and so on). But this is a visual judgment of what may be principally an acoustic phenomenon, and therefore is more than likely to be inappropriate. Since sound is conducted in the ocean so well and light so poorly, a functional social group of whales may be held together by sound rather than sight and may stretch far beyond the horizon visible from a boat, or even from an airplane, and what appears to be a lone individual may in fact be an animal traveling in company with one or many companions some miles away-by our definition, a whale in acoustic contact with another whale is not alone. This paper is concerned with baleen whales. Baleen whales are reticent laboratory subjects. In the absence of direct experimental evidence we might be able to get some idea of how far apart they can be and still be in acoustic contact by calculating how far their sounds might travel before being lost in the background noise of the ocean. Such calculations, while based in part on measured values, are also based on assumptions and remain theoretical. However, because of the exponential nature of acoustic phenomena, they are probably not entirely misleading. In this paper we will try to show what kind of useful range at least one sound made by one baleen whale species, the fin whale (Balaenoptera physalus) , might have and will suggest that its function includes long range signaling. We have chosen fin whales because they make exceptionally loud, low frequency sounds that have been the object of considerable study in recent years. It must be borne in mind throughout this paper that we are nor postulating meaningful communication of complex information among distant whales. Our remarks are concerned solely with simple signaling of place, for purposes of closing range and nothing more-in human terms, a message containing no more information than “there is a fin whale here.” Our thesis is that fin whales, and Rockefeller University and The New York Zoological Society, New York, N . Y .

Global sea-level budget 1993 - present

Abstract: Global mean sea level is an integral of changes occurring in the climate system in response to unforced climate variability as well as natural and anthropogenic forcing factors. Its temporal evolution allows detecting changes (e.g., acceleration) in one or more components. Study of the sea level budget provides constraints on missing or poorly known contributions, such as the unsurveyed deep ocean or the still uncertain land water component. In the context of the World Climate Research Programme Grand Challenge entitled “Regional Sea Level and Coastal Impacts”, an international effort involving the sea level community worldwide has been recently initiated with the objective of assessing the various data sets used to estimate components of the sea level budget during the altimetry era (1993 to present). These data sets are based on the combination of a broad range of space-based and in situ observations, model estimates and algorithms. Evaluating their quality, quantifying uncertainties and identifying sources of discrepancies between component estimates is extremely useful for various applications in climate research. This effort involves several tens of scientists from about fifty research teams/institutions worldwide (www.wcrp-climate.org/grand-challenges/gc-sea- level). The results presented in this paper are a synthesis of the first assessment performed during 2017-2018. We present estimates of the altimetry-based global mean sea level (average rate of 3.1 +/- 0.3 mm/yr and acceleration of 0.1 mm/yr2 over 1993-present), as well as of the different components of the sea level budget (http://doi.org/10.17882/54854). We further examine closure of the sea level budget, comparing the observed global mean sea level with the sum of components. Ocean thermal expansion, glaciers, Greenland and Antarctica contribute by 42%, 21%, 15% and 8% to the global mean sea level over the 1993-present. We also study the sea level budget over 2005-present, using GRACE-based ocean mass estimates instead of sum of individual mass components. Results show closure of the sea level budget within 0.3 mm/yr. Substantial uncertainty remains for the land water storage component, as shown in examining individual mass contributions to sea level.

Bloom dynamics of toxic Alexandrium species in the northeastern U.S

Abstract: Coastal waters of the northeastern U.S. are subject to recurrent outbreaks of paralytic shellfish poisoning (PSP) caused by toxic dinoflagellates in the genus Alexandrium. PSP is not uniform across the large region, but instead reflects Alexandrium growth and toxin accumulation in five separate habitats or zones defined by circulation patterns and the discontinuous distribution of the dinoflagellates. Each of these habitats has a unique set of environmental and oceanographic forcings that determine the timing and extent of bloom development and transport and that regulate the extent of genetic exchange with adjacent populations. Several habitats (e.g. the southwestern Gulf of Maine, Massachusetts Bay, and Georges Bank) are linked hydrographically and may share the same Alexandrium population via large-scale transport in a. coastal current, whereas the other two habitats (eastern Maine and southern salt ponds-embayments) seem to be isolated and have little or no hydrographic or genetic linkage to adjacent regions during bloom seasons. My paper provides an overview of the regional ecology and oceanography of Alexandrium through a focus on these five subpopulations. Issues that relate to PSP and Alexandrium dynamics throughout the world are highlighted, including species dispersal, the role of cysts and “initiation zones” in bloom development, and the influence of large- and small-scale hydrography on population development and transport. The ability of Alexandrium to colonize multiple habitats and to persist over a large region is emphasized in recognition of the adaptability and resilience of this important organism.

Seasonality in the supply of sediment to the deep Sargasso Sea and implications for the rapid transfer of matter to the deep ocean

Abstract: The flux of particles approaching the sea floor near Bermuda has been sampled by sediment trap nearly continuously for more than two years. The trap was placed at a depth of 3200 m, 1000 m above the bottom, and samples were recovered at two-month intervals. All major components of the sediment (biogenic carbonate and silicate, and organic matter) and a minor, presumably aeolian, clay component, as well as all size fractions (after sieving) were delivered in seasonally fluctuating amounts. The flux variations appear closely tied to the annual cycle of primary production in the surface water, which in the Sargasso Sea peaks in early spring and reaches a low in late fall. The total particulate flux varied by a factor of three (20 to 60 mg m−2 d−1), but some components varied by more than an order of magnitude. The close synchroneity between surface production and deep-water arrival of even fine particles, which presumably sink as components of larger aggregates, indicates extremely rapid settling of the bulk of the sediment. The evidence that even the flux of inorganic particles varies in phase with the primary production cycle suggests that an efficient mechanism exists for rapid removal from the mixed layer and transfer to deep water of many chemicals, including pollutants, which are associated with, or scavenged by, biogenic and aeolian particles.