Phytoplankton phenology in the global ocean

In recent years, phytoplankton phenology has been proposed as an indicator to monitor systematically the state of the pelagic ecosystem and to detect changes triggered by perturbation of the environmental conditions. Here we describe the phenology of phytoplankton growth for the world ocean using remote-sensing ocean colour data, and analyse its variability between 1998 and 2007. Generally, the tropics and subtropics present long growing period (≈15-20 weeks) of low amplitude (<0.5 mg Chl m⁻³), whereas the high-latitudes show short growing period (<10 weeks) of high amplitude (up to 7 mg Chl m⁻³). Statistical analyses suggest a close coupling between the development of the growing period and the seasonal increase in insolation in the North Atlantic and Southern Ocean. In the tropics and subtropics, variability in light is low, and the growing period is controlled by nutrient supply occurring when mixing increases. Large interannual variability in the duration of the growing period is observed over the decade 1998-2007, with positive anomalies following the major 1997-1998 El Niño-La Niña events, and generally negative anomalies from 2003 to 2007. Warmer Sea-Surface Temperature (SST) over the duration of the growing period is associated with longer duration at high-latitudes indicating an extension of the growing period over summer months. The opposite is observed in the tropics and subtropics, where the duration is shorter when the SST is warmer, indicating increased stratification. Positive phases of North Atlantic Oscillation and Southern Annular Mode and negative phases of Multivariate El Niño-Southern Oscillation index (El Niño conditions), associated with enhanced water mixing and nutrients supply, generally sustain longer growth. On the basis of the results, perspectives are drawn on the utility of phenology as an organising principle for the analysis of pelagic ecosystem.     

Role of coral reefs in global ocean production

Coral reefs cover some 600 thousand square kilometres of the earth's surface (0.17% of the ocean surface). First order estimates show coral reefs to contribute about 0.05% of the estimated net CO₂ fixation rate of the global oceans. Gross CO₂ fixation is relatively high (of the order 700×10¹² g C year^-1), but most of this material is recycled within the reefs. Excess (net) production of organic material (E) is much smaller, of the order 20×10¹² g C year^-1. We estimate that 3×10¹² g C year^-1 (15% ofE) is buried in reef structure, 2×10¹² g C year^-1 (10% ofE) is available for sustained human harvest, and the remaining 75% ofE is available for export from coral reefs to adjacent areas. Comparison of estimates for net production by reefs and their surrounding oceans indicates that the excess production by coral reefs is similar to new production in the photic zone of oligotrophic oceans. Consequently, estimates for global ocean production should as a first approximation include reefal areas with the surrounding ocean when assigning average net production rates. While there are significant uncertainties in these numbers, it can be concluded that organic production by reefs plays a relatively minor role in the global scale of fluxes and storage of elements. In comparison, the companion process of biologically-mediated inorganic carbon precipitation represents a major role for reefs. While reef production does respond on local scales to variation in ocean climate, neither the absolute rates nor the amount accumulated into organic pools appear to be either sensitive indicators or accurate recorders of climatic change in most reef systems. Similarly, the productivity of most reefs should be little affected by currently predicted environmental changes resulting from the Greenhouse effect.Authorship sequence does not imply seniority, it is deliberately alphabetical     

Soil respiration and the global carbon cycle

Soil respiration is the primary path by which CO₂fixed by land plants returns to the atmosphere. Estimated at approximately 75 × 10¹⁵gC/yr, this large natural flux is likely to increase due changes in the Earth's condition. The objective of this paper is to provide a brief scientific review for policymakers who are concerned that changes in soil respiration may contribute to the rise in CO₂in Earth's atmosphere. Rising concentrations of CO₂in the atmosphere will increase the flux of CO₂from soils, while simultaneously leaving a greater store of carbon in the soil. Traditional tillage cultivation and rising temperature increase the flux of CO₂from soils without increasing the stock of soil organic matter. Increasing deposition of nitrogen from the atmosphere may lead to the sequestration of carbon in vegetation and soils. The response of the land biosphere to simultaneous changes in all of these factors is unknown, but a large increase in the soil carbon pool seems unlikely to moderate the rise in atmospheric CO₂during the next century.     

The relationship between community respiration and ETS activity in the ocean

We have studied the relationship between community respiration(R) and enzymatic activity of the electron transport system(ETS) in upper ocean microbial communities (<225 µm)from different oceanic regions. In all except one of the regions,R and ETS were significantly positive correlated. This supportsthe hypothesis that ETS can be widely used to estimate planktonrespiration in natural marine communities (Packard, T.T., Adv.Aquat Microbiol, 3,207–261, 1985). A regression equationwas obtained between all the R and ETS data studied, to deriverespiration from ETS activity. This equation yields a mean errorin the prediction of ±34%, similar to the errors obtainedapplying the equations at each area, but lower than the errorobtained when using the mean R:ETS ratio to determine respiration(±45%). Our results suggest that the use of the ETS-Ralgorithm, along with measurements of ETS activity in seawater,facilitates the estimation of seawater respiratory oxygen consumptionon the mesoscale. This means that by using this approach onecould extend our knowledge of oceanic respiration over largetemporal and spatial scales, and begin to use respiration, notonly productivity, in addressing carbon balance problems inthe upper ocean.     

DMS dynamics in the most oligotrophic subtropical zones of the global ocean

The influences of physico-chemical and biological processes on dimethylsulfide (DMS) dynamics in the most oligotrophic subtropical zones of the global ocean were investigated. As metrics for the dynamics of DMS and the so-called ‘summer DMS paradox’ of elevated summer concentrations when surface chlorophyll a (Chl) and particulate organic carbon (POC) levels are lowest, we used the DMS-to-Chl and DMS-to-POC ratios in the context of three independent and complementary approaches. Firstly, field observations of environmental variables (such as the solar radiation dose, phosphorus limitation of phytoplankton and bacterial growth) were used alongside discrete DMS, Chl and POC estimates extracted from global climatologies (i.e., a ‘station based’ approach). We then used monthly climatological data for DMS, Chl, and POC averaged over the biogeographic province wherein a given oligotrophic subtropical zone resides (i.e., a ‘province based’ approach). Finally we employed sensitivity experiments with a new DMS module coupled to the ocean general circulation and biogeochemistry model PISCES to examine the influence of various processes in governing DMS dynamics in oligotrophic regions (i.e., a ‘model based’ approach). We find that the ‘station based’ and ‘province based’ approaches yield markedly different results. Interestingly, the ‘province based’ approach suggests the presence of a ‘summer DMS paradox’ in most all of the oligotrophic regions we studied. In contrast, the ‘station based’ approach suggests that the ‘summer DMS paradox’ is only present in the Sargasso Sea and eastern Mediterranean. Overall, we found the regional differences in the absolute and relative concentrations of DMS between 5 of the most oligotrophic regions of the world’s oceans were better accounted for by their nutrient dynamics (specifically phosphorus limitation) than by physical factors often invoked, e.g., the solar radiation dose. Our ‘model based’ experiments suggest that it is the limitation of phytoplankton/bacterial production and bacterial consumption of DMS by pervasive phosphorus limitation that is responsible for the ‘summer DMS paradox’.     

A global risk assessment for the success of bird introductions

1.  Concern over the impact of invasive species has led to the development of risk assessment methodologies to identify potential invaders and prevent future ecological and economic problems. However, developing a risk assessment tool is challenging because of the difficulties of accurately predicting the outcome of species introductions.
2.  In this study, we develop a global risk assessment for birds. We integrate two approaches, generalized linear mixed models (GLMM) and hierarchical tree models, to help identify those introductions with the highest risk of establishment success.
3.  Past work has shown that the number of individuals released is the main factor influencing establishment success in animals, a conclusion that was supported in our analyses. Establishment success was also higher for species with broader ecological niches and larger brains relative to body size. These features should increase the likelihood of finding an appropriate niche in the region of introduction.
4.  The GLMM and tree model predicted the probability of establishment success of birds in Europe and Australia with high accuracy (over 80% of introductions correctly classified). This highlights that establishment risk can be reasonably assessed with information on general habitat use, brain size and the size of the founder population. When compared with an alternative risk assessment tool based on a qualitative ranking, our quantitative approaches achieved higher accuracy with less information.
5.   Synthesis and applications. Quantitative risk assessments based on traits related to establishment success are difficult but feasible, providing a useful tool for guiding preventive polices aimed at mitigating the impact of invasive species.     

A global assessment of freshwater fish introductions in mediterranean-climate regions

Mediterranean-climate regions (med-regions) are global hotspots of endemism facing mounting environmental threats associated with human-related activities, including the ecological impacts associated with non-native species introductions. We review freshwater fish introductions across med-regions to evaluate the influences of non-native fishes on the biogeography of taxonomic and functional diversity. Our synthesis revealed that 136 freshwater fish species (26 families, 13 orders) have been introduced into med-regions globally. These introductions, and local extirpations, have increased taxonomic and functional faunal similarity among regions by an average of 7.5% (4.6–11.4%; Jaccard) and 7.2% (1.4–14.0%; Bray–Curtis), respectively. Faunal homogenisation was highest in Chile and the western Med Basin, whereas sw Cape and the Aegean Sea drainages showed slight differentiation (decrease in faunal similarity) over time. At present, fish faunas of different med-regions have widespread species in common (e.g. Gambusia holbrooki, Cyprinus carpio, Oncorhynchus mykiss, Carassius auratus, and Micropterus salmoides) which are typically large-bodied, non-migratory, have higher physiological tolerance, and display fast population growth rates. Our findings suggest that intentional and accidental introductions of freshwater fish have dissolved dispersal barriers and significantly changed the present-day biogeography of med-regions across the globe. Conservation challenges in med-regions include understanding the ecosystem consequences of non-native species introductions at macro-ecological scales.     

Analysis of the global ocean sampling (GOS) project for trends in iron uptake by surface ocean microbes

Microbial metagenomes are DNA samples of the most abundant, and therefore most successful organisms at the sampling time and location for a given cell size range. The study of microbial communities via their DNA content has revolutionized our understanding of microbial ecology and evolution. Iron availability is a critical resource that limits microbial communities' growth in many oceanic areas. Here, we built a database of 2319 sequences, corresponding to 140 gene families of iron metabolism with a large phylogenetic spread, to explore the microbial strategies of iron acquisition in the ocean's bacterial community. We estimate iron metabolism strategies from metagenome gene content and investigate whether their prevalence varies with dissolved iron concentrations obtained from a biogeochemical model. We show significant quantitative and qualitative variations in iron metabolism pathways, with a higher proportion of iron metabolism genes in low iron environments. We found a striking difference between coastal and open ocean sites regarding Fe(2+) versus Fe(3+) uptake gene prevalence. We also show that non-specific siderophore uptake increases in low iron open ocean environments, suggesting bacteria may acquire iron from natural siderophore-like organic complexes. Despite the lack of knowledge of iron uptake mechanisms in most marine microorganisms, our approach provides insights into how the iron metabolic pathways of microbial communities may vary with seawater iron concentrations.     

Re-examination of global emerging patterns of ocean DMS concentration

During the last decade the number of seawater dimethylsulfide (DMS) concentration measurements has increased substantially. The importance this gas, emitted from the ocean to the atmosphere, may have in the cloud microphysics and hence in the Earth albedo and radiation budget, makes it necessary to accurately reproduce the global distribution. Recently, the monthly global DMS climatology has been updated taking advantage of the threefold increased size and better resolved distribution of the observations available in the DMS database. Here, the emerging patterns found with the previous versions of the database and climatology are explored with the updated versions. The statistical relationships between the seasonalities of DMS concentrations and other variables are re-examined. The positive correlation previously found between surface seawater DMS and the daily-averaged climatological solar radiation dose in the upper mixed layer of the open ocean is confirmed with both the updated DMS database and climatology. Re-examination of the latitudinal match-mismatch between the seasonalities of DMS and phytoplankton, represented by the chlorophyll a concentration, reveals that they are highly positively correlated in latitudes higher than 40°, but anti-correlated in the 20°–40° latitudinal bands of both hemispheres. Overall, these global emerging patterns provide key information to further understanding the factors that control the emission of volatile sulfur from the ocean. The large uncertainties associated with the methodologies used in global computations, however, call for caution in using these emerging patterns as predictive tools, and prompt to the design of time series and process-oriented studies aimed at testing the validity of the observed relationships.     

Assessing the contribution of foraminiferan protists to global ocean carbonate production

Larger symbiont-bearing foraminifera are prominent and important producers of calcium carbonate in modern tropical environments. With an estimated production of at least 130 million tons of CaCO(3) per year, they contribute almost 5% of the annual present-day carbonate production in the world's reef and shelf areas (0-200 m) and approximately 2.5% of the CaCO(3) of all oceans. Together with non-symbiont-bearing smaller foraminifera, all benthic foraminifera are estimated to annually produce 200 million tons of calcium carbonate worldwide. The majority of foraminiferal calcite in modern oceans is produced by planktic foraminifera. With an estimated annual production of at least 1.2 billion tons, planktic foraminifera contribute more than 21% of the annual global ocean carbonate production. Total CaCO(3) of benthic and planktic foraminifera together amounts to 1.4 billion tons of calcium carbonate per year. This accounts to almost 25% of the present-day carbonate production of the oceans, and highlights the importance of foraminifera within the CaCO(3) budget of the world's oceans.     

Soil respiration of forest ecosystems in Japan and global implications

Within terrestrial ecosystems, soil respiration is one of the largest carbon flux components. We discuss the factors controlling soil respiration, while focusing on research conducted at the Takayama Experimental Site. Soil respiration was affected by soil temperature, soil moisture, rainfall events, typhoons, and root respiration. We consider the temporal and spatial variability of soil respiration at the Takayama Experimental Site and review the variability of annual soil respiration in Japanese forests. In the 26 compiled studies, the values of annual soil respiration ranged from 203 to 1,290 g C m⁻² year⁻¹, with a mean value of 669 g C m⁻² year⁻¹ (SD=264, CV=40). We note the need for more studies and data synthesis for the accurate prediction of soil respiration and soil carbon dynamics in Japanese forests. Finally, several methods for measuring soil respiration rates are compared and the implications of soil respiration rates for global climate change are discussed.     

An estimate of global primary production in the ocean from satellite radiometer data

An estimate of global net primary production in the ocean hasbeen computed from the monthly mean near-surface chlorophyllfields for 1979–1986 obtained by the Nimbus 7 CZCS radiometer.Our model required information about the subsurface distributionof chlorophyll, the parameters of the photosynthesis-light relationship,the sun angle and cloudiness. The computations were partitionedamong 57 biogeochemical provinces that were specified from regionaloceanography and by examination of the chlorophyll fields. Makingdifferent assumptions about the overestimation of chlorophyllby the CZCS in turbid coastal areas, the global net primaryproduction from phytoplankton is given as 45–50 Gt C year^–1.This may be compared with current published estimates for landplants of 45–68 Gt C year^–1 and for coastal vegetationof 1.9 Gt C year^–1.     

Life cycle assessment of ocean energy technologies

Purpose

Oceans offer a vast amount of renewable energy. Tidal and wave energy devices are currently the most advanced conduits of ocean energy. To date, only a few life cycle assessments for ocean energy have been carried out for ocean energy. This study analyses ocean energy devices, including all technologies currently being proposed, in order to gain a better understanding of their environmental impacts and explore how they can contribute to a more sustainable energy supply.

Methods

The study followed the methodology of life cycle assessment including all life cycle steps from cradle to grave. The various types of device were assessed, on the basis of a functional unit of 1 kWh of electricity delivered to the grid. The impact categories investigated were based on the ILCD recommendations. The life cycle models were set up using detailed technical information on the components and structure of around 180 ocean energy devices from an in-house database.

Results and discussion

The design of ocean energy devices still varies considerably, and their weight ranges from 190 to 1270 t, depending on device type. Environmental impacts are closely linked to material inputs and are caused mainly by mooring and foundations and structural components, while impacts from assembly, installation and use are insignificant for all device types. Total greenhouse gas emissions of ocean energy devices range from about 15 to 105 g CO₂-eq. kWh^?1. Average global warming potential for all device types is 53?±?29 g CO₂-eq. kWh^?1. The results of this study are comparable with those of other studies and confirm that the environmental impacts of ocean energy devices are comparable with those of other renewable technologies and can contribute to a more sustainable energy supply.

Conclusions

Ocean energy devices are still at an early stage of development compared with other renewable energy technologies. Their environmental impacts can be further reduced by technology improvements already being pursued by developers (e.g. increased efficiency and reliability). Future life cycle assessment studies should assess whole ocean energy arrays or ocean energy farms.

     

Mycorrhizal respiration: implications for global scaling relationships

Most plant species form mycorrhizas, yet these are neglected by plant physiologists. One consequence of this neglect is reduced ability to predict plant respiration, because respiration rate (R) in mycorrhizal roots might be higher than in non-mycorrhizal roots owing to increased substrate availability associated with enhanced nutrient uptake, coupled with increased respiratory product demand. Other predictions include that mycorrhizal colonization will affect scaling of R with tissue nitrogen concentrations; that mycorrhizal and non-mycorrhizal root R differ in their response to nutrient supply; and that the impact of colonization on R is related to fungal biomass. Failure to examine properly the role of colonization in determining root R means that current interpretations of root and soil respiration data might be flawed.     

Distribution patterns of mesozooplankton biomass in the North Sea

During spring 1986 and winter 1987, zooplankton samples were collected over the entire North Sea by means of a multi-closing net-system. Before taxonomic treatment, wet weight estimates and carbon content conversions were carried out. From this data set, 4 962 522 tons zooplankton biomass (dry weight) were estimated for the whole North Sea during the spring survey. High biomasses (more than 100 mg C/m³) were located in areas between the Orkneys and the Shetlands, off the mouth of the Firth of Forth, the Channel and the river Rhine. Considerable zooplankton biomass was also found parallel to the Danish west coast. Furthermore, a narrow tongue of high biomass (partly greater than 200 mg C/m³) intruded from the north, between 1 °E and 4 °E, into the northern North Sea, turning to the east at 56°N, and continuing into deeper water layers to form a left turning “helix” of high biomass in the central part of the North Sea. During the winter survey the carbon content of the zooplankton stock was a factor 10 lower than in summer. Altogether, 519340 tons of zooplankton biomass (dry weight) were estimated in winter. Centres of relatively high biomass were located off the mouth of the rivers Rhine, Weser and Elbe and off the British east coast moving in a cyclic way across the Dogger Bank into the central North Sea. A further maximum of zooplankton abundance was found in the Skagerrak region. However, an intrusion of zooplankton from the shelf edge into the North Sea was not observed in winter. A qualitative analysis of species composition showed that small copepods dominated the zooplankton in the southern and eastern North Sea. The “eddy” of high biomass in the northern North Sea observed in spring, however, was mostly shaped by the large copepodCalanus finmarchicus (70–90%). The distribution of zooplankton biomass in the North Sea is discussed in relation to the hydrographic conditions and to the biology of the dominant species.     

A global life cycle assessment for primary zinc production

Purpose

The purpose of this study was to update the average environmental impacts of global primary zinc production using a life cycle assessment (LCA) approach. This study represents the latest contribution from zinc producers, which historically established the first life cycle inventory for primary zinc production in 1998 (Western Europe) and the first global LCA-based cradle-to-gate study for zinc concentrate and special high-grade zinc (SHG; 99.99 %) in 2009. Improvements from the previous studies were realized through expanded geographical scope and range of production technologies.

Methods

The product system under study (SHG zinc) was characterized by collecting primary data for the relevant production processes, including zinc ore mining and concentration, transportation of the zinc concentrate, and zinc concentrate smelting. This data was modeled in GaBi 6 and complemented with background data from the GaBi 2013 databases to create the cradle-to-gate LCA model. Allocation was used to distribute the inputs and outputs among the various co-products produced during the production process, with mass of metal content being the preferred allocation approach, when applicable.

Results and discussion

In total, this global study includes primary data from 24 mines and 18 smelters, which cover 4.7?×?10⁶ MT of zinc concentrate and 3.4?×?10⁶ MT of SHG zinc, representing 36 and 27 % of global production, respectively. While the LCA model generated a full life cycle inventory, selected impact categories and indicators are reported in this article (global warming potential, acidification potential, eutrophication potential, photochemical ozone creation potential, ozone creation potential, and primary energy demand). The results show that SHG zinc has a primary energy demand of 37,500 MJ/t and a climate change impact of 2600 kg CO₂-eq./t. Across all impact categories and indicators reported here, around 65 % of the burden are associated with smelting, 30 % with mining and concentration, and 5 % with transportation of the concentrate. Sensitivity analyses were carried out for the allocation method (total mass versus mass of metal content) and transportation of zinc concentrate.

Conclusions

This study generated updated LCA information for the global production of SHG zinc, in line with the metal industry’s current harmonization efforts. Through the provision of unit process information for zinc concentrate and SHG zinc production, greater transparency is achieved. Technological and temporal representativeness was deemed to be high. Geographical representativeness, however, was found to be moderate to low. Future studies should focus on increasing company participation from underrepresented regions.

     

A crustal scarcity indicator for long-term global elemental resource assessment in LCA

The International Journal of Life Cycle Assessment - How to assess impacts of mineral resources is much discussed in life cycle assessment (LCA). We see a need for, and a lack of, a mineral...     

The use of mesenchymal stem cells in tissue engineering: A global assessment

Mesenchymal stem cells (MSCs) are of great interest to both clinicians and researchers for their great potential to enhance tissue engineering. Their ease of isolation, manipulability and potential for differentiation are specifically what have made them so attractive. These multipotent cells have been found to differentiate into cartilage, bone, fat, muscle, tendon, skin, hematopoietic-supporting stroma and neural tissue. Their diverse in vivo distribution includes bone marrow, adipose, periosteum, synovial membrane, skeletal muscle, dermis, pericytes, blood, trabecular bone, human umbilical cord, lung, dental pulp and periodontal ligament. Despite their frequent use in research, no standardized criteria exist for the identification of mesenchymal stem cells; The International Society for Cellular Therapy has sought to change this with a set of guidelines elucidating the major surface markers found on these cells. While many studies have shown MSCs to be just as effective as unipotent cells for certain types of tissue regeneration, limitations do exist due to their immunosuppressive properties. This paper serves as a review pertaining to these issues, as well as others related to the use of MSCs in tissue engineering.Key words: mesenchymal stem cells, tissue engineering, regenerative medicine