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The article presents a study in which diagnostic and mechanistic models are used to show that a combination of Southern Ocean biological uptake and reversible scavenging of zinc onto sinking particles causes zinc deficiencies observed throughout the low-latitude ocean.

The article discusses research investigating increasing anthropogenic nitrogen (N) in the North Pacific Ocean (NPO). Topics include anthropogenic emissions of reactive N from northeastern Asia and the subsequent atmospheric N deposition (AND) over regions of the NPO, the rate of increase of excess N relative to phosphate (P), which was the highest in the vicinity of the Asian source continent, and the impact of increased N in the upper NPO on primary production in this N-limited region.

The article focuses on research into chemical cues from coral reefs that could limit reef recovery. It states that when seaweeds become abundant the recovery of corals is suppressed unless herbivory fish return. It mentions that juvenile corals and fishes are repelled by chemical cues from seaweed-dominated corals which are fished but are attracted to corals where fishing is prohibited. It talks about methods of managing degraded reefs to attract recruiting corals and fishes.

Earth's climate underwent a fundamental change between 1250 and 700 thousand years ago, the mid-Pleistocene transition (MPT), when the dominant periodicity of climate cycles changed from 41 thousand to 100 thousand years in the absence of substantial change in orbital forcing. Over this time, an increase occurred in the amplitude of change of deep-ocean foraminiferal oxygen isotopic ratios, traditionally interpreted as defining the main rhythm of ice ages although containing large effects of changes in deep-ocean temperature. We have separated the effects of decreasing temperature and increasing global ice volume on oxygen isotope ratios. Our results suggest that the MPT was initiated by an abrupt increase in Antarctic ice volume 900 thousand years ago. We see no evidence of a pattern of gradual cooling, but near-freezing temperatures occur at every glacial maximum. [ABSTRACT FROM AUTHOR]

Fundamental thermodynamics and climate models suggest that dry regions will become drier and wet regions will become wetter in response to warming. Efforts to detect this long-term response in sparse surface observations of rainfall and evaporation remain ambiguous. We show that ocean salinity patterns express an identifiable fingerprint of an intensifying water cycle. Our 50-year observed global surface salinity changes, combined with changes from global climate models, present robust evidence of an intensified global water cycle at a rate of 8 ± 5% per degree of surface warming. This rate is double the response projected by current-generation climate models and suggests that a substantial (16 to 24%) intensification of the global water cycle will occur in a future 2° to 3° warmer world. [ABSTRACT FROM AUTHOR]

The ocean is an important global source of nitrous oxide (N2O), a greenhouse gas that contributes to stratospheric ozone destruction. Bacterial nitrification and denitrification are thought to be the primary sources of marine N2O, but the isotopic signatures of N2O produced by these processes are not consistent with the marine contribution to the global N2O budget. Based on enrichment cultures, we report that archaeal ammonia oxidation also produces N2O. Natural-abundance stable isotope measurements indicate that the produced N2O had bulk δ15N and δ18O values higher than observed for ammonia-oxidizing bacteria but similar to the δ15N and δ18O values attributed to the oceanic N2O source to the atmosphere. Our results suggest that ammonia-oxidizing archaea may be largely responsible for the oceanic N2O source. [ABSTRACT FROM AUTHOR]

Nitrogen cycling is normally thought to dominate the biogeochemistry and microbial ecology of oxygen-minimum zones in marine environments. Through a combination of molecular techniques and process rate measurements, we showed that both sulfate reduction and sulfide oxidation contribute to energy flux and elemental cycling in oxygen-free waters off the coast of northern Chile. These processes may have been overlooked because in nature, the sulfide produced by sulfate reduction immediately oxidizes back to sulfate. This cryptic sulfur cycle is linked to anammox and other nitrogen cycling processes, suggesting that it may influence biogeochemical cycling in the global ocean. [ABSTRACT FROM AUTHOR]

Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in mercury and persistent organic pollutants. Most of these perturbations, tied either directly or indirectly to human fossil fuel combustion, fertilizer use, and industrial activity, are projected to grow in coming decades, resulting in increasing negative impacts on ocean biota and marine resources. [ABSTRACT FROM AUTHOR]

The Ediacaran Period (635 to 542 million years ago) was a time of fundamental environmental and evolutionary change, culminating in the first appearance of macroscopic animals. Here, we present a detailed spatial and temporal record of Ediacaran ocean chemistry for the Doushantuo Formation in the Nanhua Basin, South China. We find evidence for a metastable zone of euxinic (anoxic and sulfidic) waters impinging on the continental shelf and sandwiched within ferruginous [Fe(ll)-enriched] deep waters. A stratified ocean with coeval oxic, sulfidic, and ferruginous zones, favored by overall low oceanic sulfate concentrations, was maintained dynamically throughout the Ediacaran Period. Our model reconciles seemingly conflicting geochemical redox conditions proposed previously for Ediacaran deep oceans and helps to explain the patchy temporal record of early metazoan fossils. [ABSTRACT FROM AUTHOR]

Proxies for past seawater chemistry, such as Mg/Ca and Sr/Ca ratios, provide a record of the dynamic exchanges of elements between the solid Earth, the atmosphere, and the hydrosphere and the evolving influence of life. We estimated past oceanic Mg/Ca and Sr/Ca ratios from suites of 1.6- to 170-million-year-old calcium carbonate veins that had precipitated from seawater-derived fluids in ocean ridge flank basalts. Our data indicate that before the Neogene, oceanic Mg/Ca and Sr/Ca ratios were lower than in the modern ocean. Decreased ocean spreading since the Cretaceous and the resulting slow reduction in ocean crustal hydrothermal exchange throughout the early Tertiary may explain the recent rise in these ratios. [ABSTRACT FROM AUTHOR]

Iron speciation data for the late Archean Mount McRae Shale provide evidence for a euxinic (anoxic and sulfidic) water column 2.5 billion years ago. Sulfur isotope data compiled from the same stratigraphic section suggest that euxinic conditions were stimulated by an increase in oceanic sulfate concentrations resulting from weathering of continental sulfide minerals exposed to an atmosphere with trace amounts of photosynthetically produced oxygen. Variability in local organic matter flux likely confined euxinic conditions to midportions of the water column on the basin margin. These findings indicate that euxinic conditions may have been common on a variety of spatial and temporal scales both before and immediately after the Paleoproterozoic rise in atmospheric oxygen, hinting at previously unexplored texture and variability in deep ocean chemistry during Earth's early history. [ABSTRACT FROM AUTHOR]

Oceanic production of calcium carbonate is conventionally attributed to marine plankton (coccolithophores and foraminifera). Here we report that marine fish produce precipitated carbonates within their intestines and excrete these at high rates. When combined with estimates of global fish biomass, this suggests that marine fish contribute 3 to 15% of total oceanic carbonate production. Fish carbonates have a higher magnesium content and solubility than traditional sources, yielding faster dissolution with depth. This may explain up to a quarter of the increase in titratable alkalinity within 1000 meters of the ocean surface, a controversial phenomenon that has puzzled oceaffographers for decades. We also predict that fish carbonate production may rise in response to future environmental changes in carbon dioxide, and thus become an increasingly important component of the inorganic carbon cycle. [ABSTRACT FROM AUTHOR]

Fixed nitrogen (N) is a limiting nutrient for algae in the low-latitude ocean, and its oceanic inventory may have been higher during ice ages, thus helping to lower atmospheric CO2 during those intervals. In organic matter within planktonic foraminifera shells in Caribbean Sea sediments, we found that the 15N/14N ratio from the last ice age is higher than that from the current interglacial, indicating a higher nitrate 15N/14N ratio in the Caribbean thermocline. This change and other species-specific differences are best explained by less N fixation in the Atlantic during the last ice age. The fixation decrease was most likely a response to a known ice age reduction in ocean N loss, and it would have worked to balance the ocean N budget and to curb ice age--interglacial change in the N inventory. [ABSTRACT FROM AUTHOR]

Degradation of marine organic carbon provides a major source of atmospheric carbon dioxide, whereas preservation in sediments results in accumulation of oxygen. These processes involve the slow decay of chemically recalcitrant compounds and physical protection. To assess the importance of physical protection, we constructed a reaction-diffusion model in which organic matter differs only in its accessibility to microbial degradation but not its intrinsic reactivity. The model predicts that organic matter decays logarithmically with time t and that decay rates decrease approximately as 0.2 × t-1 until burial. Analyses of sediment-core data are consistent with these predictions. [ABSTRACT FROM AUTHOR]

Focuses on spectral analyses of the late Oligocene and early Miocene climate and ocean carbon chemistry from two deep-sea cores recovered in the western equatorial Atlantic. Calibrated proxy records of Oligocene and Miocene lithologic cycles; Nature of the high-frequency signals in the isotope records; Orbital anomaly hypothesis.

The article reports on the reliance of ocean scientists on the seawater reference samples from the laboratory of marine chemist Andrew Dickson at the Scripps Institution of Oceanography. Topics discussed include the use of these samples in measuring seawater alkalinity and tracking of carbon dioxide emissions in the ocean, among others, the possible impact of the retirement plans of Dickson on his laboratory, and the significant contributions of Dickson to marine chemistry.

Biologically available nitrogen limits photosynthesis in much of the world ocean. Organic matter (OM) stoichiometry had been thought to control the balance between the two major nitrogen removal pathways--denitrification and anammox--but the expected proportion of 30% anammox derived from mean oceanic OM is rarely observed in the environment. With incubations designed to directly test the effects of stoichiometry, however, we showed that the ratio of anammox to denitrification depends on the stoichiometry of OM supply, as predicted. Furthermore, observed rates of nitrogen loss increase with the magnitude of OM supply. The variable ratios between denitrification and anammox previously observed in the ocean are thus attributable to localized variations in OM quality and quantity and do not necessitate a revision to the global nitrogen cycle. [ABSTRACT FROM AUTHOR]

Fluid inclusion data suggest that the composition of major elements in seawater changes slowly over geological time scales. This view contrasts with high-resolution isotope data that imply more rapid fluctuations of seawater chemistry. We used a non-steady-state box model of the global sulfur cycle to show that the global γ34S record can be explained by variable marine sulfate concentrations triggered by basin-scale evaporite precipitation and dissolution. The record is characterized by long phases of stasis, punctuated by short intervals of rapid change. Sulfate concentrations affect several important biological processes, including carbonate mineralogy, microbially mediated organic matter remineralization, sedimentary phosphorous regeneration, nitrogen fixation, and sulfate aerosol formation. These changes are likely to affect ocean productivity, the global carbon cycle, and climate. [ABSTRACT FROM AUTHOR]

Presents information on a study which investigated isotopic evidence for variations in the marine calcium cycle over the Cenozoic period. Methodology of the study; Results and discussion on the study.

Information about the Third International Symposium on the Ocean in a High-CO2 World on the challenges in assessing the responses of fisheries and other marine life to ocean acidification from rising carbon dioxide (CO2) emissions is presented. Topics include the biological implications of chemical changes in the ocean, the limitations in understanding them, and methods for evaluating acidification's potential impact on ocean ecosystems.

The article discusses a report within the issue regarding an analysis of the microbial cycling of nitrogen and sulfur in the oxygen minimum zone (OMZ) in the offshore waters of northern Chile. According to researchers, the results of the study suggest that the working hypotheses used by scientists to study microbial interactions and processes of stratified marine water columns has overlooked the contribution of the "cryptic" microbial sulfur cycle. An overview of the strategy used by bacterial communities, such as the nitrate-reducing Thioploca species, in oxygen-depleted water columns to link nitrogen and sulfur cycles in the ocean are presented.

The article discusses the unprecedented environmental impact of ocean acidification on the marine ecosystems as a result of human behavior. According to the author, the alteration of the ocean's pH as a result of carbon dioxide (CO2) emissions will have long-lasting and damaging effects to marine ecosystems. An overview of ocean chemistry, including the chemical reaction of dissolved CO2 in sea water, is presented. Also discussed is the physiological, ecological, and environmental effects of ocean acidification on marine organisms, including the loss of mass in plankton with calcareous skeletons.

The article discusses the role of nitrous oxide in global climate change and terrestrial and marine factors that may exacerbate the atmospheric concentration of nitrous oxide. Terrestrial nitrous oxide emissions are related to human activities while marine emissions are linked more specifically to eutrophication and ocean warming and acidification. A critical factor in ocean-based production of nitrous oxide is said to be the concentration of dissolved oxygen in seawater. At low oxygen concentrations, a process called nitrifier denitrification boosts the production of nitrous oxide.

The article discusses research reconstructing past seawater chemistry in an effort to gain insight into the driving forces behind long-term climate change. According to the author, an ocean's chemical composition is determined by rivers, submarine hot springs, and ocean sediments that add and remove elements from seawater. Scientists are able to tell how active oceanic sources and sinks are through the abundance of certain elements which maintain a near constant ratio to salinity. Topics include an overview of a report within the issue that addresses the problem of finding reliable archives of seawater chemistry through the measurement of calcium ratios, such as magnesium (Mg)/calcium (Ca), recovered from ocean crust beneath sediments and its implication for climate change.

The article discusses how anthropogenic influences on marine chemistry will lead to an expansion of oceanic dead zones. Higher levels of marine carbon dioxide are resulting from the combustion of fossil fuels. This process induces acidification of the ocean water. Additionally, mid-water oxygen concentrations decline due to lower sea-surface oxygen concentrations, lowered ventilation from ocean warming, and local eutrophication events. Ocean scientists fix the potential for marine aerobic life to a minimum dissolved oxygen concentration. A concentration below this level leads to these dead zones, wherein respiration is limited and efforts for maintaining life are maximized.

The article discusses research that investigates a physiological pathway that is common to all marine bony fish and significantly contributes to the marine inorganic carbon cycle. First clued in by physiological aspects of toadfish (Opsanus beta), the researchers observed pellets in the species' gut that are a metastable form of calcite containing large amounts of magnesium. They further modeled the size, composition, and abundance of marine fish across the global ocean using satellite-derived estimates of primary productivity from phytoplankton and the conversion of organic matter from one tropic level in the food chain to another.

The article discusses research that provides an approach for characterizing the history of the oceanic nitrogen cycle and the ways in which new nitrogen supports primary production by measuring the nitrogen isotopic composition of the shells of planktonic foraminifera. New nitrogen refers to the method by which the coupling between the nitrogen and carbon cycles is quantified. This study is intended to shed light on the ambiguous ways in which new nitrogen is supplied to nutrient-poor oceanic regions and to supplement stoichiometric research on the link between new nitrogen and denitrification. Results are gleaned from the Last Glacial Maximum to the present.

Iron fertilization of the ocean is a potential strategy to remove carbon dioxide from the atmosphere. But this strategy has generated much debate among ocean and climate scientists. To assess whether iron fertilization has potential as an effective sequestration strategy, one needs to measure the ratio ofiron added to the amount of carbon sequestered to the deep ocean in field studies. In the Southern Ocean, there have been three open-ocean iron-enrichment experiments. All three produced increases in biomass and associated decreases in dissolvedinorganic carbon and macronutrients. These experiments allow an initial assessment of the export efficiency and the size of ocean area affected, both of which are needed to determine whether iron fertilization can be an effective mitigation strategy.

The article discusses a study in a 2011 issue of the journal “Coral Reefs,” by Crook and colleagues investigating the long-term responses of corals to low carbonate saturation conditions by studying the marine biology of locations with low carbonate and hydrogen-ion concentrations, called ojos.

The article discusses the prospective effect of global warming on phytoplankton in ocean water affected by sea ice meltwater and river runoff. The authors predict that the smallest phytoplankton cells in the Arctic Ocean will thrive while larger ones will not. It notes ocean stratification conditions and chemistry that will change with global warming. The authors compare and contrast upper-ocean bacterio-plankton, picophytoplankton, and larger nanoplankton and their responses to ocean temperature changes. Biomass in the forms of chlorophyll and fucoxanthin is discussed.

This article presents information on an assumption related to the new production and export production, which is used in many studies of marine chemistry. The equating of new production to export production is a common assumption in many studies of marine chemistry. This assumption has allowed numerous estimates of the hard-to-measure quantity of export production to be made, using the more easily measured new production. Researchers investigated the strength of this assumption for annually integrated new and export production in the central Californian marine upwelling system, using an Eddy-resolving, coupled physical-ecosystem-biogeochemical model. They find that new and export production can decouple on a local scale, because of horizontal transport by persistent meso- and submesoscale circulation patterns, as well as by offshore flow caused by Ekman transport. Thus, although these results do not pertain to global estimates over long periods of time, they do illustrate that the concept of the equality of new and export production has to be used with care, particularly over short spatial and temporal scales.

Discusses the influence of the carbonate ion content of seawater on the atmosphere and ocean. Properties of the atmosphere and ocean that were influenced by the content; Comparison of the size distribution of calcium carbonate grains in marine sediments from a site on the Ontong Java Plateau in the western equatorial Pacific to similar measurements made in the Equatorial Atlantic; Comparison results.