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"Moore, Mark"
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Global analysis of ocean phytoplankton nutrient limitation reveals high prevalence of co-limitation
Nutrient availability limits phytoplankton growth throughout much of the global ocean. Here we synthesize available experimental data to identify three dominant nutrient limitation regimes: nitrogen is limiting in the stratified subtropical gyres and in the summertime Arctic Ocean, iron is most commonly limiting in upwelling regions, and both nutrients are frequently co-limiting in regions in between the nitrogen and iron limited systems. Manganese can be co-limiting with iron in parts of the Southern Ocean, whilst phosphate and cobalt can be co-/serially limiting in some settings. Overall, an analysis of experimental responses showed that phytoplankton net growth can be significantly enhanced through increasing the number of different nutrients supplied, regardless of latitude, temperature, or trophic status, implying surface seawaters are often approaching nutrient co-limitation. Assessments of nutrient deficiency based on seawater nutrient concentrations and nutrient stress diagnosed via molecular biomarkers showed good agreement with experimentally-assessed nutrient limitation, validating conceptual and theoretical links between nutrient stoichiometry and microbial ecophysiology.
Nutrient limitation is a key constraint on ocean productivity. Here, by analysing a compilation of field experiments spanning the global ocean, this study shows that increasing the number of different nutrients supplied significantly increases net phytoplankton growth, suggesting multiple nutrients are often approaching co-limiting levels.
Journal Article
Public Value Accounting: Establishing the Philosophical Basis
Questions of how best to define the ends, justify the means, and measure the performance of governments have preoccupied political economists for centuries. Recently, the concept of public value—defined in terms of the many dimensions of value that a democratic public might want to see produced by and reflected in the performance of government—has been proposed as an alternative approach. This article develops three philosophical claims central to the practice of public value accounting: (1) when the collectively owned assets of government are being deployed, the appropriate arbiter of public value is the collectively defined values of a \"public\" called into existence and made articulate through the quite imperfect processes of democratic governance; (2) the collectively owned assets include not only government money but also the authority of the state; (3) the normative framework for assessing the value of government production relies on both utilitarian and deontological philosophical frameworks.
Journal Article
Experimental Insights into the Cognitive Significance of Early Stone Tools
Stone-flaking technology is the most enduring evidence for the evolving cognitive abilities of our early ancestors. Flake-making was mastered by African hominins ~3.3 ma, followed by the appearance of handaxes ~1.75 ma and complex stone reduction strategies by ~1.6 ma. Handaxes are stones flaked on two opposed faces ('bifacially'), creating a robust, sharp-edged tool, and complex reduction strategies are reflected in strategic prior flaking to prepare or 'predetermine' the nature of a later flake removal that served as a tool blank. These technologies are interpreted as major milestones in hominin evolution that reflect the development of higher-order cognitive abilities, and the presence and nature of these technologies are used to track movements of early hominin species or 'cultures' in the archaeological record. However, the warranting argument that certain variations in stone tool morphologies are caused by differences in cognitive abilities relies on analogy with technical replications by skilled modern stoneworkers, and this raises the possibility that researchers are projecting modern approaches to technical problems onto our non-modern hominin ancestors. Here we present the results of novel experiments that randomise flake removal and disrupt the modern stoneworker's inclination to use higher-order reasoning to guide the stone reduction process. Although our protocols prevented goal-directed replication of stone tool types, the experimental assemblage is morphologically standardised and includes handaxe-like 'protobifaces' and cores with apparently 'predetermined' flake removals. This shows that the geometrical constraints of fracture mechanics can give rise to what appear to be highly-designed stoneworking products and techniques when multiple flakes are removed randomly from a stone core.
Journal Article
The unsentimental education
\"Spinning off from Bill Willingham's FABLES saga! Peter Piper. Bo Peep. Connor Wolf. As members of the elite network of agents known as the Shadow Players, these three legendary Fables share a single purpose: to protect the newly merged magical and mundane worlds from all threats. But what happens when the greatest threat of all comes from within? Bobby Speckland may look like any other Texas high school student, but as the first Mundy to gain magical abilities in the post-Everafter world, he's also a sorcerer of incredible power. So when a trio of bullied teens take over their school using stolen Fable weapons and unleash the Lone Star State's supernatural shock troops to consolidate their coup d'âecole, it's up to Bobby to find a way to bring them down--by any means necessary. For the three veteran agents and their volatile young ally, the deadliest class of all time is now in session. Will it prove to be a learning experience? Or will the Fable and Mundy worlds both discover that school is out--forever?\"-- Provided by publisher.
Book
The Importance of Atmospheric Deposition for Ocean Productivity
Dust is produced primarily in desert regions and transported long distances through the atmosphere to the oceans. Upon deposition of dust, its dissolution can provide an important source of a range of nutrients, particularly iron, to microbes living in open ocean surface waters. The dust supply is greatest nearest to deserts, hence in the Northern Hemisphere. The Southern Ocean region is farthest from these dust sources and shows clear evidence that phytoplankton primary production is limited, at least in part, by the rate of supply of iron. Iron is also essential for nitrogen fixation. In regions of high atmospheric iron supply, such as the tropical North Atlantic, stimulation of nitrogen fixation drives the phytoplankton population toward a state in which phosphorus supply rates limit primary production. Atmospheric deposition is also an important source of nitrogen to the low latitude ocean, where it stimulates primary production. In this review we consider the sources, transport, and deposition of atmospheric dust iron and nitrogen to the oceans and their impacts on plankton systems. In conclusion, we suggest key areas for future research.
Journal Article
Nutrient co-limitation at the boundary of an oceanic gyre
Nutrient amendment experiments at the boundary of the South Atlantic gyre reveal extensive regions in which nitrogen and iron are co-limiting, with other micronutrients also approaching co-deficiency; such limitations potentially increase phytoplankton community diversity.
Moderating marine micronutrients
Whether micronutrient co-limitation is pervasive in the ocean and whether it affects phytoplankton growth and productivity is poorly understood. Through a series of large-scale nutrient amendment experiments at the eastern boundary of the South Atlantic gyre, Thomas Browning and colleagues report extensive regions in which nitrogen and iron are co-limiting, with near co-deficiency of the trace metal cobalt and vitamin B
12
. These findings suggest that nitrogen–iron co-limitation is pervasive in the ocean and potentially increases phytoplankton community diversity.
Nutrient limitation of oceanic primary production exerts a fundamental control on marine food webs and the flux of carbon into the deep ocean
1
. The extensive boundaries of the oligotrophic sub-tropical gyres collectively define the most extreme transition in ocean productivity, but little is known about nutrient limitation in these zones
1
,
2
,
3
,
4
. Here we present the results of full-factorial nutrient amendment experiments conducted at the eastern boundary of the South Atlantic gyre. We find extensive regions in which the addition of nitrogen or iron individually resulted in no significant phytoplankton growth over 48 hours. However, the addition of both nitrogen and iron increased concentrations of chlorophyll
a
by up to approximately 40-fold, led to diatom proliferation, and reduced community diversity. Once nitrogen–iron co-limitation had been alleviated, the addition of cobalt or cobalt-containing vitamin B
12
could further enhance chlorophyll
a
yields by up to threefold. Our results suggest that nitrogen–iron co-limitation is pervasive in the ocean, with other micronutrients also approaching co-deficiency. Such multi-nutrient limitations potentially increase phytoplankton community diversity.
Journal Article