Nitrogen fixation and release of fixed nitrogen by Trichodesmium spp. in the Gulf of Mexico

During a 3‐yr study in the Gulf of Mexico, we measured dinitrogen (N2) fixation and nitrogen (N) release by Trichodesmium and compared these rates with water column N demand and the estimated N necessary to support blooms of Karenia brevis, a toxic dinoflagellate that severely affects the West Florida shelf. Net and gross N2 fixation rates were compared in simultaneous incubations using δ15N2 uptake and acetylene reduction, respectively. The difference between net and gross N2 fixation is assumed to be an approximation of the rate of N release. Results demonstrate that Trichodesmium in the Gulf of Mexico are fixing N2 at high rates and that an average of 52% of this recently fixed N2 is rapidly released. Calculations suggest that observed densities of Trichodesmium can provide enough N to support moderately sized K. brevis blooms. Based on other studies where δ15N2 and acetylene reduction were compared directly, it appears that N release from Trichodesmium is common but varies in magnitude among environments. In addition, carbon (C) and N‐based doubling times for Trichodesmium vary among studies and environments. Comparing gross N2 fixation and C fixation directly, C‐based doubling times exceeded N‐based doubling times, which suggests an imbalance in elemental turnover or a failure to fully quantify Trichodesmium N use

WIGGLE-MATCHING USING KNOWN-AGE PINE FROM JERMYN STREET, LONDON

A slice of pine from the period covered by single-year calibration data (Stuiver 1993) was selected to serve as part of the quality assurance procedures of the English Heritage radiocarbon dating program. following successful wiggle-matching, of (14)C measurements from structural 15th century English oak timbers (Hamilton et al. 2007). The timber selected was a roofing element front it house on Jermyn Street, central London, demonstrated by dendrochronology to have been felled in AD 1670. Eighteen single-ring samples were dated by the (14)C laboratories at Groningen, Oxford, and SUERC: each laboratory was sent a random selection of 6 samples. This approach was intended to mimic the mix of samples and relative ages incorporated into Bayesian chronological models during the project research. This paper presents the results of this study.</p

When and Why? The Chronology and Context of Flint Mining at Grime’s Graves, Norfolk, England

New radiocarbon dating and chronological modelling have refined understanding of the character and circumstances of flint mining at Grime’s Graves through time. The deepest, most complex galleried shafts were worked probably from the third quarter of the 27th century cal BC and are amongst the earliest on the site. Their use ended in the decades around 2400 cal BC, although the use of simple, shallow pits in the west of the site continued for perhaps another three centuries. The final use of galleried shafts coincides with the first evidence of Beaker pottery and copper metallurgy in Britain. After a gap of around half a millennium, flint mining at Grime’s Graves briefly resumed, probably from the middle of the 16th century cal BC to the middle of the 15th. These ‘primitive’ pits, as they were termed in the inter-war period, were worked using bone tools that can be paralleled in Early Bronze Age copper mines. Finally, the scale and intensity of Middle Bronze Age middening on the site is revealed, as it occurred over a period of probably no more than a few decades in the 14th century cal BC. The possibility of connections between metalworking at Grime’s Graves at this time and contemporary deposition of bronzes in the nearby Fens is discussed

Drosophila Hsc70-4 Is Critical for Neurotransmitter Exocytosis In Vivo

AbstractPrevious in vitro studies of cysteine-string protein (CSP) imply a potential role for the clathrin-uncoating ATPase Hsc70 in exocytosis. We show that hypomorphic mutations in Drosophila Hsc70-4 (Hsc4) impair nerve-evoked neurotransmitter release, but not synaptic vesicle recycling in vivo. The loss of release can be restored by increasing external or internal Ca2+ and is caused by a reduced Ca2+ sensitivity of exocytosis downstream of Ca2+ entry. Hsc4 and CSP are likely to act in common pathways, as indicated by their in vitro protein interaction, the similar loss of evoked release in individual and double mutants, and genetic interactions causing a loss of release in trans-heterozygous hsc4-csp double mutants. We suggest that Hsc4 and CSP cooperatively augment the probability of release by increasing the Ca2+ sensitivity of vesicle fusion

MOLECULAR APPROACHES FOR IN SITU IDENTIFCIATION OF NITRATE UTILIZATION BY MARINE BACTERIA AND PHYTOPLANKTON

Traditionally, the importance of inorganic nitrogen (N) for the nutrition and growth of marine phytoplankton has been recognized, while inorganic N utilization by bacteria has received less attention. Likewise, organic N has been thought to be important for heterotrophic organisms but not for phytoplankton. However, accumulating evidence suggests that bacteria compete with phytoplankton for nitrate (NO3-) and other N species. The consequences of this competition may have a profound effect on the flux of N, and therefore carbon (C), in ocean margins. Because it has been difficult to differentiate between N uptake by heterotrophic bacterioplankton versus autotrophic phytoplankton, the processes that control N utilization, and the consequences of these competitive interactions, have traditionally been difficult to study. Significant bacterial utilization of DIN may have a profound effect on the flux of N and C in the water column because sinks for dissolved N that do not incorporate inorganic C represent mechanisms that reduce the atmospheric CO2 drawdown via the ?biological pump? and limit the flux of POC from the euphotic zone. This project was active over the period of 1998-2007 with support from the DOE Biotechnology Investigations ? Ocean Margins Program (BI-OMP). Over this period we developed a tool kit of molecular methods (PCR, RT-PCR, Q-PCR, QRT-PCR, and TRFLP) and combined isotope mass spectrometry and flow-cytometric approaches that allow selective isolation, characterization, and study of the diversity and genetic expression (mRNA) of the structural gene responsible for the assimilation of NO3- by heterotrophic bacteria (nasA). As a result of these studies we discovered that bacteria capable of assimilating NO3- are ubiquitous in marine waters, that the nasA gene is expressed in these environments, that heterotrophic bacteria can account for a significant fraction of total DIN uptake in different ocean margin systems, that the expression of nasA is differentially regulated in genetically distinct NO3- assimilating bacteria, and that the best predictors of nasA gene expression are either NO3- concentration or NO3- uptake rates. These studies provide convincing evidence of the importance of bacterial utilization of NO3-, insight into controlling processes, and provide a rich dataset that are being used to develop linked C and N modeling components necessary to evaluate the significance of bacterial DIN utilization to global C cycling. Furthermore, as a result of BI-OMP funding we made exciting strides towards institutionalizing a research and education based collaboration between the Skidaway Institute of Oceanography (SkIO) and Savannah State University (SSU), an historically black university within the University System of Georgia with undergraduate and now graduate programs in marine science. The BI-OMP program, in addition to supporting undergraduate (24) graduate (10) and postdoctoral (2) students, contributed to the development of a new graduate program in Marine Sciences at SSU that remains an important legacy of this project. The long-term goals of these collaborations are to increase the capacity for marine biotechnology research and to increase representation of minorities in marine, environmental and biotechnological sciences

The end of the world, or just 'goodbye to all that'? Contextualising the red deer heap from Links of Noltland, Westray, within late 3rd-millennium cal BC Orkney

As part of a major international research project, The Times of Their Lives, a programme of radiocarbon dating and Bayesian modelling was undertaken to refine the chronology of activities in one small but important part of the extensive Late Neolithic and Bronze Age settlement on Links of Noltland on the island of Westray, Orkney. The selected area (Trench D) is well known for having produced, next to a wall, the remains of a heap of at least 15 red deer carcasses, on top of which had been placed a large cod, a gannet’s wing along with part of a greater black-backed gull, and a pair of large antlers. This remarkable deposit had been preceded by, and was followed by, periods of cultivation and the deposition of domestic refuse. Refined date estimates have been produced, based on 18 radiocarbon determinations obtained from 16 samples from Trench D (including nine newly obtained dates, three from individual deer in the heap). These clarify when, during this long sequence of activities, the deer were heaped up: probably in the 22nd century cal bc, around the same time as Beaker pottery was deposited elsewhere on the Links. This allows comparison between the dated activities in this part of the site with activity elsewhere on the Links and also with other episodes of deer deposition in 3rd-millennium cal bc Orkney. It encourages exploration of the possible reasons for what appears to be a remarkable act of structured deposition. The significance of an earlier, much larger scale deposit featuring cattle remains at Ness of Brodgar is discussed in exploring the nature of Orcadian society and practices during the second half of the 3rd millennium cal bc

The chronology of Glastonbury Lake Village

The Glastonbury Lake Village in Somerset, UK, is made up of 90 mounds comprising 40 roundhouses. Excavations between 1892 and 1907 revealed Iron Age structural and material remains unparalleled in Western Europe. The settlement's exact chronology, however, has remained uncertain. Here, the authors present a programme of radiocarbon and dendrochronological dating and chronological modelling on samples from recent excavations. The results indicate that the site was founded in the early second century cal BC, with the last structures being built just over a century later. This new, robust chronology can be used to date a wide range of associated material culture, and complements chronologies established for other Iron Age sites

Understanding Middle Neolithic food and farming in and around the Stonehenge World Heritage Site: an integrated approach

Little synthesis of evidence for Middle Neolithic food and farming in Wiltshire, particularly in and around the Stonehenge World Heritage Site (WHS) has been possible, until now, due to a paucity of assemblages. The excavation of a cluster of five Middle Neolithic pits and an inhumation burial at West Amesbury Farm (WAF) has prompted a review of our understanding of pit sites of this period from the county. Bioarchaeological assemblages are used to investigate evidence for the consumption of animal and plant-based foods, and for agricultural and pastoral farming. For the first time Middle Neolithic zooarchaeological evidence, including strontium isotope data, is considered alongside archaeobotanical data, and radiocarbon dating. The absence of cultivated plants from WAF and contemporary sites in the county is consistent with the hypothesis that the reduction in cereal cultivation and greater reliance of wild plants witnessed in the later part of the Neolithic in southern England began in the Middle Neolithic. The zooarchaeological evidence from the same sites demonstrates that the shift away from cereal cultivation may be concurrent with, rather than earlier than, an increase in the relative proportion of deposited pig bones relative to cattle. Both cattle and pigs deposited in pits at WAF have strontium and sulphur isotope values consistent with the local biosphere, and therefore were potentially raised in the area. Zooarchaeological data from WAF compliments that from human dental calculus and lipid residues in associated Peterborough Ware pottery that local cattle husbandry included exploitation of dairy. It also highlights the presence of consistent food preparation methods between pits as seen through butchery practice. The faunal and archaeobotanical remains from contemporary pit deposits suggest that similar farming and subsistence strategies can be proposed across the county, though with some inter-site variation in deposition. Together these excavated pit sites are likely to represent only a sample of those present in the area. Application of a similar integrated approach to material from other Middle Neolithic pits holds potential for better understanding of food and farming in this previously neglected period