Biogeochemical cycles

An existing model of C and N dynamics in soils was supplemented with a plant growth submodel and cropping practice routines (fertilization, irrigation, tillage, crop rotation, and manure amendments) to study the biogeochemistry of soil carbon in arable lands. The new model was validated against field results for short-term (1-9 years) decomposition experiments, the seasonal pattern of soil CO2 respiration, and long-term (100 years) soil carbon storage dynamics. A series of sensitivity runs investigated the impact of varying agricultural practices on soil organic carbon (SOC) sequestration. The tests were simulated for corn (maize) plots over a range of soil and climate conditions typical of the United States. The largest carbon sequestration occurred with manure additions; the results were very sensitive to soil texture (more clay led to greater sequestration). Increased N fertilization generally enhanced carbon sequestration, but the results were sensitive to soil texture, initial soil carbon content, and annual precipitation. Reduced tillage also generally (but not always) increased SOC content, though the results were very sensitive to soil texture, initial SOC content, and annual precipitation. A series of long-term simulations investigated the SOC equilibrium for various agricultural practices, soil and climate conditions, and crop rotations. Equilibrium SOC content increased with decreasing temperatures, increasing clay content, enhanced N fertilization, manure amendments, and crops with higher residue yield. Time to equilibrium appears to be one hundred to several hundred years. In all cases, equilibration time was longer for increasing SOC content than for decreasing SOC content. Efforts to enhance carbon sequestration in agricultural soils would do well to focus on those specific areas and agricultural practices with the greatest potential for increasing soil carbon content.

Environmental Context. The fate and behaviour of trace pollutants are very strongly modified, and usually dominated, by their physical and chemical interactions with naturally occurring aquatic colloids (defined as solid phase material with one dimension between 1 nm and 1 µm). This review summarises the area and key advances in the field of natural aquatic colloids, including technique development and quantification of colloidal structure and interactions with pollutants.The review also discusses areas in which significant advances are likely to be made or are needed and, as such, provides a framework for further work in the next few years.

Archaea constitute a considerable fraction of the microbial biomass on Earth. Like Bacteria they have evolved a variety of energy metabolisms using organic and/or inorganic electron donors and acceptors, and many of them are able to fix carbon from inorganic sources. Archaea thus play crucial roles in the Earth's global geochemical cycles and influence greenhouse gas emissions. Methanogenesis and anaerobic methane oxidation are important steps in the carbon cycle; both are performed exclusively by anaerobic archaea. Oxidation of ammonia to nitrite is performed by Thaumarchaeota. They represent the only archaeal group that resides in large numbers in the global aerobic terrestrial and marine environments on Earth. Sulfur-dependent archaea are confined mostly to hot environments, but metal leaching by acidophiles and reduction of sulfate by anaerobic, nonthermophilic methane oxidizers have a potential impact on the environment. The metabolisms of a large number of archaea, in particular those dominating the subsurface, remain to be explored. 437 Annu. Rev. Microbiol. 2013.67:437-457. Downloaded from www.annualreviews.org by University of Vienna -Main Library and Archive Services on 09/12/13. For personal use only.

Environmental context. On a global scale, soils store more carbon than plants or the atmosphere. The cycling of this vast reservoir of reduced carbon is closely tied to variations in environmental conditions, but robust predictions of climate-carbon cycle feedbacks are hampered by a lack of mechanistic knowledge regarding the sensitivity of organic matter decomposition to rising temperatures. This text provides a critical discussion of the practice to conceptualise parts of soil organic matter as intrinsically resistant to decomposition or 'recalcitrant'.

Environmental context. Trafficked streets are air pollution hot spots where people experience high exposure to hazardous pollutants. Although monitoring networks provide crucial information about measured pollutant levels, the measurements are resource demanding and thus can be performed at only few selected sites. Fast and easily applied street pollution models are therefore necessary tools to provide information about the loadings in streets without measurement activities. We evaluate the Operational Street Pollution Model, one of the most commonly applied models in air pollution management and research worldwide.

Environmental context. Recent developments in nanotechnology have focussed towards innovation and usage of multifunctional and superior hybrid nanomaterials. Possible exposure of these novel nanohybrids can lead to unpredicted environmental fate, transport, transformation and toxicity scenarios. Environmentally relevant emerging properties and potential environmental implications of these newer materials need to be systematically studied to prevent harmful effects towards the aquatic environment and ecology.

From his boyhood in southwestern Minnesota to his pathbreaking scientific investigation of a bog lake north of Minneapolis, Raymond Lindeman was passionate about learning how the natural world works. Science allowed one to “see and try to understand the majestic symmetry of the universe” while serving humanity, he wrote as a high school senior applying for college. In 1935, a year before Lindeman began drawing samples from Cedar Bog Lake for his graduate research, the British ecologist Arthur Tansley coined the term “ecosystem.” It was Lindeman, however, who gave birth to ecosystems ecology with his landmark paper “The Trophic-Dynamic Aspect of Ecology” published in the journal Ecology shortly after his death in 1942 at age twenty-seven. In the paper, a young mind born of the tall grass prairie joined in a single system the length of food chains, the efficiency of trophic transfers, the rates of primary productivity, energy values for losses due to respiration, predation, and decomposition, and the role of bacteria and microorganisms in cycling dead organic matter. Lindeman was able to look beyond ecosystem relationships and perceive the underlying thermodynamics of ecosystem behavior. He calculated how energy derived from the sun flows and dissipates as heat through successive layers of ever-more complex life forms in the ecological food pyramid, with life in each ascending layer using energy more efficiently. More than seven decades after its publication Lindeman’s paper continues to be listed among essential readings in natural resource and wildlife management and in ecosystem conservation.

ABSTRACT:
There is a known bias in C/N, d13C and d15N values of organic matter (OM) due to pre-analysis acid treatment methods. We report here, for the first time, the results of a pre-analysis acid treatment method comparison of measured C/N, d13C and d15N values in bulk OM from a sedimentary sequence of samples to illustrate this bias. Here we show that acid treatment significantly reduces the accuracy (between method biases) and precision (within method bias) of C/N, d13C and d15N values of OM, suggesting a differential response of sample OM between methods and sample horizons, and in some cases inefficient removal of inorganic carbon. We show that different methods can significantly influence environmental interpretation in some of our sample horizons (i.e. interpretation of aquatic vs. terrestrial OM source; C3 vs. C4 vegetation). Specifically, there are unpredictable and non-linear differences between methods for C/N values in the range of ~ 1 – 100; d13C values in the range of 0.2 – 6.8 ‰ and; d15Nvalues in the range of 0.3 – 0.7 ‰. Importantly, these ranges are mostly much greater than the instrument precision (defined as the standard deviation of replicate analysis of standard reference materials; for this study, ± 0.5 for C/N values, ± 0.1 ‰ for d13C values and; ± 0.1 ‰ for d15N). The accuracy and precision of measured C/N, d13C and d15N values of bulk OM is not just dependent upon environmental variability, but on acid pre-treatment, residual inorganic carbon and organic matter state and composition. Collectively, this makes the correlation between samples prepared in different ways, including those from down core reconstructions, highly questionable.

Keywords: C/N ratios, δ13C, δ15N, organic matter; pre-analysis acid treatment methods, environmental interpretation, palaeoclimate.

The systematic literature search on the fertility rate was performed on articles from the Web of Science compiled by the Institute of Scientific Information (ISI) to provide major publication characteristics. All articles related to Fertility from year 1980 to 2011 were analyzed with the bibliometric approach using non-parametrics techniques. Total Citation, Citation per year and Cited References were significantly different between the 80’s, 90’s and 2000’s, with more than a 100% increase in the number of publication. The association between number of authors and citation per year were significantly weak. Number of publication in a journal posed a poor negative association with the citation per year. Similarity between Authors Keyword and KeyWords Plus® do not promote the increase in citation per year. The author’s affiliation and country of publication would be an interesting exploration for future fertility research. The bibiliometric analyses on Fertility is rather new and vital...

We invite systematic consideration of the metaphors of cycles and circulation as a long-term theme in the history of the life and environmental sciences and medicine. Ubiquitous in ancient religious and philosophical traditions, especially in representing the seasons and the motions of celestial bodies, circles once symbolized perfection. Over the centuries, cyclic images in western medicine, natural philosophy, natural history and eventually biology gained independence from cosmology and theology and came to depend less on strictly circular forms. As potent ‘canonical icons’, cycles also interacted with representations of linear and irreversible change, including arrows, arcs, scales, series and trees, as in theories of the Earth and of evolution. In modern times, life cycles and reproductive cycles have often been held to characterize life, in some cases especially female life, while human efforts selectively to foster and disrupt these cycles have harnessed their productivity in ...

We invite systematic consideration of the metaphors of cycles and circulation as a long-term theme in the history of the life and environmental sciences and medicine. Ubiquitous in ancient religious and philosophical traditions, especially in representing the seasons and the motions of celestial bodies, circles once symbolized perfection. Over the centuries cyclic images in western medicine,
natural philosophy, natural history and eventually biology gained independence
from cosmology and theology and came to depend less on strictly circular forms.
As potent ‘canonical icons’, cycles also interacted with representations of linear and
irreversible change, including arrows, arcs, scales, series and trees, as in theories
of the Earth and of evolution. In modern times life cycles and reproductive cycles
have often been held to characterize life, in some cases especially female life, while
human efforts selectively to foster and disrupt these cycles have harnessed their productivity
in medicine and agriculture. But strong cyclic metaphors have continued to
link physiology and climatology, medicine and economics, and biology and manufacturing,
notably through the relations between land, food and population. From the
grand nineteenth-century transformations of matter to systems ecology, the circulation
of molecules through organic and inorganic compartments has posed the problem
of maintaining identity in the face of flux and highlights the seductive ability of
cyclic schemes to imply closure where no original state was in fact restored. More
concerted attention to cycles and circulation will enrich analyses of the power of
metaphors to naturalize understandings of life and their shaping by practical interests
and political imaginations.

La desertificación humana de territorios con recursos limitados es un problema recurrente
en las sociedades avanzadas; dicha desertificación no necesariamente conlleva una
paralela desertización de tales territorios, si no que generalmente sucede al contrario,
dado que disminuyen la presión antropozoógena sobre los mismos. Sin embargo, los
discursos de las ciencias sociales (aunque bien intencionados) suelen conducir a
enfrentamientos dialécticos sin dar respuestas operativas. Por ejemplo, se ha considerado
históricamente, hasta la inclusión de España y Portugal en la Unión Europa, que la desigual
distribución de la tierra (latifundios, base de las dehesas y montados) del Oeste ibérico
era la causa última de su nulo desarrollo; tras la incorporación de estos dos países en la U.
E., sorprendentemente las dehesas y los montados se consideran patrimonio a conservar
debido a su “gran diversidad”. Tal salto cualitativo sólo es explicable si se analizan los
intereses (de diferente índole) ocultos tras los discursos. Así, el mantenimiento de las
explotaciones del Oeste ibérico sólo es posible por las generosas ayudas comunitarias que
suponen, aproximadamente, un cuarto de los beneficios obtenidos. A pesar de que estas
ayudas van en función del número de hectáreas (beneficiándose principalmente los
grandes terratenientes) paradójicamente se denuncia agriamente que las ayudas al
desempleo de los jornaleros (desposeídos del sistema) son la razón de que no haya un salto
económico cualitativo. Otras ayudas comunitarias se otorgan en base a las cabezas de
ganado, lo que conlleva a un aumento artificial de la carga ganadera sobre los escasos
recursos de las dehesas o montados, ocasionando signos de desertización o erosión que,
con la desertificación humana, se habían reducido en el pasado. Ello es otra paradoja
evidente; si la ganadería no es rentable no puede ser una solución la incentivación de la
sobreexplotación (no sólo por la aparición de un producto excedentario por caro, si no por
las consecuencias ambientales incluso a corto plazo).
Por tanto, para la gestión apropiada de las dehesas o montados se necesita tener una
sólida base científica desposeída indiscutiblemente de carga ideológica; esta base sólo es
posible si se disponen datos fiables y contrastados, capaces de establecer relaciones entre
todas las partes del sistema. Una buena herramienta para sistematizar este proceso es el
empleo de la Biogeoquímica.
Consideremos que la Tierra se diferencia de Marte por la existencia del llamado efecto
invernadero (ahora tan maldecido) y por la acumulación de energía potencial en la
superficie terrestre (Edafoesfera), principalmente, en forma de “humus” englobado
dentro de lo que se entiende como materia orgánica del suelo (MOS). Por tanto, un índice
de potencialidad de los ecosistemas terrestres es la presencia de tal compartimento de
energía potencial, ya sea como índice de biodiversidad ora de fertilidad (productividad);
por ello, es posible sea el mejor índice biogeoquímico, aunque limitado por su lenta
respuesta a los impactos. Un vistazo somero al Oeste ibérico muestra suelos de colores pardos a rojizos claros (según
la intensidad de erosión pretérita), índice de su escaso contenido en MOS; si a ello unimos
una general escasez de profundidad edáfica, la conclusión es que su producción no puede
ser nada más que limitada y, consecuentemente, que basar el desarrollo regional en el
rubro agroganadero es inviable (sin subvenciones). La causa de ello es la mala distribución
de las lluvias, concomitante al clima mediterráneo: Llueve cuando no se necesita (con
lixiviación y pérdida de bioelementos) y hay sequía cuando más se necesita (escasa
producción, escaso retorno de carbono al suelo, escaso contenido de MOS).
La única solución a esta situación no es otra que imitar a los climas continentales y hacer
“llover” en verano; esto es, implementar el riego (tecnología importada con la cultura
árabe). La aplicación del riego no sólo asegura la producción si no que va más allá desde el
punto de vista ambiental: Incrementa efectiva y automáticamente los contenidos de MOS
con una mínima gestión adecuada. Este aumento de MOS ocasiona espectaculares mejoras
de las propiedades físicas (v. g., estructura) y, también, de las condiciones fisicoquímicas
(v. g., capacidad de intercambio catiónico) edáficas, incentivando la actividad biológica
(tanto para bien, como para mal). Sin embargo, esta solución se encuentra con las
limitantes de la disponibilidad de agua, del coste de su transporte y de las condiciones
geomorfológicas, no siendo menores, por ejemplo, la profundidad y pedregosidad
edáficas.
Un ejemplo claro de que el aumento de pluviometría invernal que, en la práctica,
aumenta los contenidos de MOS (hecho muy interesante para la captura de C) no conlleva
paradójicamente al aumento de la producción se ha demostrado en los sistemas forestales
(Montes bajos de Quercus pyrenaica) de la vertiente Norte de la Sierra de Gata (Oeste
español). Dicho exceso de agua invernal (régimen percolativo) sólo ocasiona acidificación
del medio (limitando la actividad microbiana) y, por ende, conlleva a una pobreza de
nutrientes. Por ello, los rebollares bajo pluviometría cercana a los 800 mm a-1 son significativamente más productivos (> 4,0 Mg MS ha-1 a-1; DAP > 3,0 mm a-1) que aquellos que superan los 1000 mm a-1 de lluvia (< 2,5 Mg MS ha-1 a-1; DAP ~ 2,5 mm a-1).

Coastal wetlands, such as mangroves, seagrass beds, and salt marshes, are highly threatened by increasing anthropic pressures, including chemical pollution. Persistent organic pollutants (POPs) have attracted attention in these particularly vulnerable ecosystems, due to their bioaccumulative, pervasive, and ecotoxic behavior. This article reviews and summarizes available information regarding current levels, biogeochemical cycling, and effects of POPs on coastal wetlands. Sediment POP levels were compared with international quality guidelines, revealing many areas where compounds could cause damage to biota. Despite this, toxicological studies on some coastal wetland plants and microorganisms showed a high tolerance to those levels. These taxonomic groups are likely to play a key role in the cycling of the POPs, with an active role in their accumulation, immobilization, and degradation. Toxicity and biogeochemical processes varied markedly along three main axes; namely species, environmental conditions, and type of pollutant. While more focused research on newly and unintentionally produced POPs is needed, mainly in salt marshes and seagrass beds, with the information available so far, the environmental behavior, spatial distribution, and toxicity level of the studied POPs showed similar patterns across the three studied ecosystems.

Microbialites are rock-like underwater structures that look like reefs
but are made entirely of millions of microbes. These structures
are very ancient and can be found in di􀀀erent environments on
every continent on Earth. Mexico has many microbialite reefs,
in desert valleys, crater-lakes, and coastal lagoons. Science helps
us to understand the microbes that build microbialites, to know
whether the same kinds of microbes make up microbialites in
di􀀀erent regions of the world, and to figure out how the microbes
organize into microbialites. Many things are damaging microbialites
in Mexico, including poorly planned development, pollution from
lack of sewage treatment, too much water usage, and the fertilizers
used for agriculture. Policies that regulate development are urgently
needed to help save these diverse and ancient microbial reefs.

Nitrogen loss from applied fertilizer can be a significant environmental quality issue if NO3 moves to surface or ground water. The Iowa nutrient reduction strategy science assessment identified winter cereal rye (Secale cereal L.) cover crop as a practice that can significantly reduce N and P loss (41% NO3-N and 21% P reduction) from corn (Zea mays L.) and soybean [Glycine max. (L.) Merr.] fields. Cereal rye, when used as a cover crop, through its fibrous root system is able to explore the soil and use residual NO3N. In order to further understand the effectiveness of rye as a cover crop for scavenging and recycling N, there is a need to understand the amount of root/shoot biomass and N and carbon (C) partitioning between roots and shoots at the time of rye termination. This study was conducted at the Climate and Corn-Based Cropping Systems Coordinated Agricultural Project (CSCAP) cover crop site, located at the Ag. Engineering and Agronomy Research Farm, Iowa State University near...

Results of analysis of hydrochemical characteristics (main elements of nutrient and carbon cycles) spatial distribution in the Blue Bay waters based on the expeditionary research (carried out by Marine Hydrophysical Institute in 2002 – 2014) data are represented. It is shown that this area and the oceanographic platform located in its southwestern part constitute a convenient ground for synchronous remote and sub-satellite studies of natural oceanographic processes and impact of coastal anthropogenic sources of pollution. Introduction. The entire shelf part of the Black Sea (regardless of the fact which country an economic zone belongs to) is a water area exposed to constant and intensive anthropogenic impact. River runoff control, water exchange violation due to construction of different onshore facilities (e.g. piers), pollution and eutrophication, which arise from the insufficiently treated sewage waters and polluted river water discharge, are the factors of negative effect on co...

Bioturbation, the biogenic modification of sediments through particle reworking and burrow ventilation, is a key mediator of many important geochemical processes in marine systems. In situ quantification of bioturbation can be achieved in a myriad of ways, requiring expert knowledge, technology, and resources not always available, and not feasible in some settings. Where dedicated research programmes do not exist, a practical alternative is the adoption of a trait-based approach to estimate community bioturbation potential (BP c ). This index can be calculated from inventories of species, abundance and biomass data (routinely available for many systems), and a functional classification of organism traits associated with sediment mixing (less available). Presently, however, there is no agreed standard categorization for the reworking mode and mobility of benthic species. Based on information from the literature and expert opinion, we provide a functional classification for 1033 benthic invertebrate species from the northwest European continental shelf, as a tool to enable the standardized calculation of BP c in the region. Future uses of this classification table will increase the comparability and utility of large-scale assessments of ecosystem processes and functioning influenced by bioturbation (e.g., to support legislation). The key strengths, assumptions, and limitations of BP c as a metric are critically reviewed, offering guidelines for its calculation and application.

L’Istituto di Scienze Marine (ISMAR)-Sede di Bologna coordina da oltre 15 anni progetti multidisciplinari in Antartide, con l’obiettivo di valutare meccanismi ed effetti delle principali variazioni climatiche attraverso lo studio dei cicli biogeochimici dei maggiori elementi presenti nelle acque marine. I progetti sono basati sul fatto che comprendere i processi biogeochimici attuali sia la chiave per interpretare i processi del passato e che questa conoscenza sia utile per valutare le evoluzioni future. L’Antartide è un’area preferenziale dove svolgere questa attività essendo molto sensibile alle variazioni climatiche che
rimangono registrate nei sedimenti marini in maniera particolarmente marcata. Tuttavia, parecchie incertezze rimangono in particolare riguardo i modelli ecologici e la comprensione del comportamento della calotta glaciale Antartica durante il Quaternario, a causa della mancanza di inequivocabili dati geologici e di accurato controllo cronologico degli eventi. Queste incertezze influenzano la nostra capacità di predire la futura dinamica climatica dell’Antartide e quindi anche del clima globale. Le ricerche sono state condotte in collaborazione con altre sedi di ISMAR, Università e altri Enti di Ricerca.

We invite systematic consideration of the metaphors of cycles and circulation as a long-term theme in the history of the life and environmental sciences and medicine. Ubiquitous in ancient religious and philosophical traditions, especially in representing the seasons and the motions of celestial bodies, circles once symbolized perfection. Over the centuries cyclic images in western medicine, natural philosophy, natural history and eventually biology gained independence from cosmology and theology and came to depend less on strictly circular forms. As potent ‘canonical icons’, cycles also interacted with representations of linear and irreversible change, including arrows, arcs, scales, series and trees, as in theories of the Earth and of evolution. In modern times life cycles and reproductive cycles have often been held to characterize life, in some cases especially female life, while human efforts selectively to foster and disrupt these cycles have harnessed their productivity in me...

The effect of alternative harvesting practices on long-term ecosystem productivity and carbon sequestration was investigated with the ecosystem simulation model, FORECAST. Three tree species, white spruce (Picea glauca), trembling aspen (Populus tremuloides), and lodgepole pine (Pinus contorta var. latifolia), were each used in combination with different rotation lengths. An additional run was conducted to investigate the effect of nitrogen addition to aspen. Results were also compared with a natural disturbance scenario in which a mixedwood stand composed of all three species was subjected to a catastrophic wildfire, on a 150-year fire cycle. All simulations included an understory grass competitor, Calamagrostis canadensis, and the total simulation length for each scenario was 300 years. Carbon stored in soil represented a large, relatively stable pool and showed only minor long-term responses to harvesting activities. Tree biomass and litter pools, in contrast, fluctuated widely in concert with the harvest cycle. Calamagrostis was relatively unimportant as a carbon pool. Total ecosystem carbon increased with rotation length regardless of species, and this was attributable largely to changes in the live biomass pool. A 150-year pine, and a 200-year spruce rotation, were the only scenarios in which average total carbon storage exceeded that in the natural disturbance scenario. For equivalent rotation lengths, total carbon storage was the greatest in aspen, followed by pine and spruce, respectively. Application of nitrogen fertilizer to aspen increased average total carbon storage by 9%. This increase was attributable primarily to the storage in wood products and live biomass pools. The proportion of total carbon stored in the soil pool decreased as harvest frequency declined (i.e., at longer rotation lengths), while the proportion stored in litter pools was roughly equivalent among all scenarios. However, there was a consistent decline in soil carbon across the 300-year simulation period for managed stands. The natural disturbance scenario, in contrast, showed an increase in soil carbon over the same period. Species-specific biomass accumulation rates (an index of ecosystem productivity) were maximal in the shortest rotations for aspen, but in mid-length rotations for pine and spruce. Short rotation scenarios showed a marked drop in site productivity over subsequent rotations. The application of nitrogen fertilizer reduced the relative drop in site productivity for aspen. Our results suggest a trade-off between ecosystem storage capacity and timber production. By selecting the appropriate tree species and rotation length, however, it is possible to either balance these competing demands, or favour one value versus the other.

Environmental Context. The composition of calcium carbonate in annual skeletal growth bands reflects the environmental conditions in which coral grows, enabling their use as long-term bio-monitors and archives of environmental conditions. Such archives will provide a baseline against which recent and future pollutant levels can be compared.

The observations of the terrestrial surface by means of satellite remote sensing, have the potential of being used to characterize processes occurring on the soil-vegetation-atmosphere system. Data acquired from different view angles are an additional source of information with respect to those offered for spectral, spatial and temporal variations detected with this kind of instruments. One of the applications where the use of this fourth source of information has become relevant is land cover classification. To explore its usefulness, a number of approaches have been proposed based on linear kernel-driven models, unfortunately no significant contribution on the associated parameters of the models to classify land cover has been reported. On this work two issues are investigated: (1) the fitness of the Uni-Parametric BRDF model to data acquired by the POLDER-1 sensor and (2) the contribution of multiple view angle observations to the land cover classification problem using the aforementioned model. Although correlation levels between the measurements of the POLDER-1 sensor and those by the model under consideration are greater than 97%, no evidence was found related to the improvement of land cover classification by using multiple view angle data. These results are in agreement with the need to define new classification systems based on variables that may be inferred through the observations acquired by a satellite remote sensors reported by other researchers.

Environmental context. Eutrophication can lead to the production of harmful algal blooms and is one of the world's most serious water quality issues. Phosphorus is potentially the limiting macro-nutrient in fresh, estuarine and some marine waters. Consequently, it plays a crucial role in determining the ecological status of many aquatic ecosystems. Considerable effort has been invested in monitoring dissolved reactive phosphorus and total phosphorus in the water column, but less is known about the speciation of phosphorus, particularly in the sediment. This compartment is an important and dynamic reservoir of phosphorus and a potential long-term source of phosphorus release to the water column by the sediment-water interface. This paper investigates the solid-phase speciation and reorganisation of phosphorus within the sediments of a shallow lake system in south-east Australia (the Gippsland Lakes) which suffers from recurring harmful algae blooms. Various strategies are proposed to determine the minimum realistic timescale required to deplete the sediment of labile and reactive phosphorus species.

Diatoms and dinoflagellates are major bloomforming
phytoplankton groups competing for resources in
the oceans and coastal seas. Recent evidence suggests that
their competition is significantly affected by climatic factors
under ongoing change, modifying especially the conditions
for cold-water, spring bloom communities in temperate
and Arctic regions. We investigated the effects of phytoplankton
community composition on spring bloom carbon
flows and nutrient stoichiometry in multiyear mesocosm
experiments. Comparison of differing communities showed
that community structure significantly affected C accumulation
parameters, with highest particulate organic carbon
(POC) buildup and dissolved organic carbon (DOC) release
in diatom-dominated communities. In terms of inorganic nutrient
drawdown and bloom accumulation phase, the dominating
groups behaved as functional surrogates. Dominance
patterns, however, significantly affected C : N : P : Chl a ratios
over the whole bloom event: when diatoms were dominant,
these ratios increased compared to dinoflagellate dominance
or mixed communities. Diatom-dominated communities
sequestered carbon up to 3.6-fold higher than the expectation
based on the Redfield ratio, and 2-fold higher compared
to dinoflagellate dominance. To our knowledge, this is
the first experimental report of consequences of climatically
driven shifts in phytoplankton dominance patterns for carbon
sequestration and related biogeochemical cycles in coastal
seas. Our results also highlight the need for remote sensing
technologies with taxonomical resolution, as the C : Chl a ratio
was strongly dependent on community composition and
bloom stage. Climate-driven changes in phytoplankton dominance
patterns will have far-reaching consequences for major
biogeochemical cycles and need to be considered in climate
change scenarios for marine systems.

Environmental contextPerfluoroalkyl compounds are organic contaminants that exhibit strong resistance to chemical- and microbial-degradation. As partitioning between solid and aqueous phases is expected to control the transport of perfluoroalkyl compounds, we studied the molecular mechanisms of their adsorption–desorption at a representative Fe oxide surface using in situ molecular spectroscopy. The results provide valuable information on the types of bonds formed, and enable a better understanding of the transport and fate of these organic contaminants in natural environments. The kinetics and mechanisms of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) adsorption to nanoparticulate hematite (α-Fe2O3) from aqueous solutions were examined using in situ, flow-through attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. Results indicate that both PFOA and PFOS molecules are retained at the hydrophilic hematite surface and the adsorptio...

The potential nutrient return in a chestnut coppice (Castanea sativa Miller) over a period of 3 years (1991)(1992)(1993)(1994) has been established and compared with the returns found in four deciduous oak (Quercus pyrenaica Wild.) forests (1990)(1991)(1992)(1993) located in the Sierra de Gata mountains (central Spanish system). A convergence of abscission phenology patterns was observed among the different ecosystems studied, together with a delay in leaf fall at the warmest plot. This similarity is logical since the plots harbour the same deciduous species which are, however, subjected to climatological variations. The chestnut coppice was found to be more productive than the oak forests, the amounts of leaves, branches, flowers and total litterfall being significantly greater. Statistical analysis showed a highly significant correlation between the chestnut coppice and the oak forest aboveground production, ranging between 0.82 and 0.96 for the leaves and between 0.72 and 0.89 for the total litter. In general, the leaf organs of the chestnut trees showed a higher concentration of bioelements than the oaks, with N and Ca predominant in the buds, Ca and Zn in the branches, K in the fruits, and above all Fe and Cu in the other plant remains. In all the forests studied, the potential nutrient supply fluctuated over the years and depended strongly on phenological factors; above all it was found to be governed by the leaves, which contributed most to the return of mineral nutrients to the soil. The most marked potential nutrient return through the oak aerial organs occurred on the plot with the lowest rainfall, particularly with respect to P and Ca. Considering all the forest plots, the general sequence of the amount of bioelements returning with the litterfall to the soil was as follows:

Metabolism provides a basis for using first principles of physics, chemistry, and biology to link the biology of individual organisms to the ecology of populations, communities, and ecosystems. Metabolic rate, the rate at which organisms take up, transform, and expend energy and materials, is the most fundamental biological rate. We have developed a quantitative theory for how metabolic rate varies with body size and temperature. Metabolic theory predicts how metabolic rate, by setting the rates of resource uptake from the environment and resource allocation to survival, growth, and reproduction, controls ecological processes at all levels of organization from individuals to the biosphere. Examples include: (1) life history attributes, including development rate, mortality rate, age at maturity, life span, and population growth rate; (2) population interactions, including carrying capacity, rates of competition and predation, and patterns of species diversity; and (3) ecosystem processes, including rates of biomass production and respiration and patterns of trophic dynamics.

Windthrows change forest structure and species composition in Central Amazon forests. However, the effects of widespread tree mortality associated with wind-disturbances on soil properties have not yet been described. In this study, we investigated short-term effects (seven years after disturbance) of a windthrow event on soil carbon stocks and concentrations in a Central Amazon terra firme forest. The soil carbon stock (averaged over a 0–30 cm depth profile) in disturbed plots (61.4 ± 4.18 Mg ha−1, mean ± standard error) was marginally higher (p = 0.009) than that from undisturbed plots (47.7 ± 6.95 Mg ha−1). The soil organic carbon concentration in disturbed plots (2.0 ± 0.08 %) was significantly higher (p < 0.001) than that from undisturbed plots (1.36 ± 0.12 %). Moreover, soil carbon stocks were positively correlated with soil clay content (r = 0.575 and p = 0.019) and with tree mortality intensity (r = 0.493 and p = 0.045). Our results indicate that large inputs of plant litter associated with large windthrow events cause a short-term increase in soil carbon content, and the degree of increase is related to soil clay content and tree mortality intensity. Higher nutrient availability in soils from large canopy gaps created by wind disturbance may increase vegetation resilience and favor forest recovery.

Earth’s land cover has been extensively transformed over time due to both human activities and natural causes. Previous global studies have focused on developing spatial and temporal patterns of dominant human land-use activities (e.g., cropland, pastureland, urban land, wood harvest). Process-based modeling studies adopt different strategies to estimate the changes in land cover by using these land-use data sets in combination with a potential vegetation map, and subsequently use this information for impact assessments. However, due to unaccounted changes in land cover (resulting from both indirect anthropogenic and natural causes), heterogeneity in land-use/cover (LUC) conversions among grid cells, even for the same land use activity, and uncertainty associated with potential vegetation mapping and historical estimates of human land use result in land cover estimates that are substantially different compared to results acquired from remote sensing observations. Here, we present a method to implicitly account for the differences arising from these uncertainties in order to provide historical estimates of land cover that are consistent with satellite estimates for recent years. Due to uncertainty in historical agricultural land use, we use three widely accepted global estimates of cropland and pastureland in combination with common wood harvest and urban land data sets to generate three distinct estimates of historical land-cover change and underlying LUC conversions. Hence, these distinct historical reconstructions offer a wide range of plausible regional estimates of uncertainty and the extent to which different ecosystems have undergone changes. The annual land cover maps and LUC conversion maps are reported at 0.5° 0.5° resolution and describe the area of 28 land- cover types and respective underlying land-use transitions. The reconstructed data sets are relevant for studies addressing the impact of land-cover change on biogeo- physics, biogeochemistry, water cycle, and global climate.

The data can be downloaded from: http://www.atmos.illinois.edu/~meiyapp2/datasets.htm

The significance of freshwaters as key players in the global budget of both carbon dioxide and methane has recently been highlighted. In particular, rivers clearly do not act simply as inert conduits merely piping carbon from catchment to coast, but, on the whole, their metabolic activity transforms a considerable fraction of the carbon that they convey. In addition, nitrogen is cycled, sometimes in tight unison with carbon, with appreciable amounts being ‘denitrified’ between catchment and coast. However, shortfalls in our knowledge about the significance of exchange and interaction between rivers and their catchments, particularly the significance of interactions mediated through hyporheic sediments, are still apparent. From humble beginnings of quantifying the consumption of oxygen by small samples of gravel, to an integrated measurement of reach scale transformations of carbon and nitrogen, our understanding of the cycling of these two macro elements in rivers has improved markedly in the past few decades. However, recent discoveries of novel metabolic pathways in both the nitrogen and carbon cycle across a spectrum of aquatic ecosystems, highlights the need for new directions and a truly multidisciplinary approach to quantifying the flux of carbon and nitrogen through rivers.

We measured the effect of elevated atmospheric CO2 on atmospheric nitrogen (N2) fixation for the tree species Alnus glutinosa growing in monoculture or in mixture with the non-N2-fixing tree species Betula pendula and Fagus sylvatica. We addressed the hypotheses that 1: N2 fixation in A. glutinosa will increase in response to increased atmospheric CO2 concentrations, when growing in monoculture, 2: the impact of elevated CO2 on N2 fixation in A. glutinosa is the same in mixture and in monoculture and 3: the impacts of elevated CO2 on N cycling will be evident in a decrease in leaf δ15N and in the soil-leaf enrichment factor (EF), and that these impacts will not differ between mixed and single species stands. Trees were grown in a forest plantation on former agricultural fields for 4 growing seasons, after which the trees were on average 3.8 m tall and canopy closure had occurred. Atmospheric CO2 concentrations were maintained at either ambient or elevated (by 200 ppm) concentrations using a free-air CO2 enrichment (FACE) system. Leaf δ15N was measured and used to estimate the amount (Ndfa) and proportion (%Ndfa) of N derived from atmospheric fixation. On average 62% of the N in A. glutinosa leaves was from fixation. %Ndfa and Ndfa for A. glutinosa trees in monoculture did not increase under elevated CO2, despite higher growth rates. However, N2 fixation did increase for trees growing in mixture, despite the absence of significant growth stimulation. There was evidence that fixed N2 was transferred from A. glutinosa to F. sylvatica and B. pendula, but no evidence that this affected their CO2 response. This study shows that N2 fixation in A. glutinosa may be higher in a future elevated CO2 world, but that this effect will only occur where the trees are growing in mixed species stands.

Environmental context Novel technology is used to examine oil contaminated soil to better understand this longstanding problem. The data indicate that oil forms a non-discriminant layer over all the soil components, which in their natural state would be exposed to water, and that it retains certain polar compounds while contributing other oil contaminants to the surrounding porewater and groundwater. Such molecular level information helps to better understand the reoccurrence of hydrophobicity in remediated soil, and could lead to novel clean-up methods. Comprehensive multiphase (CMP) NMR spectroscopy is a novel NMR technology introduced in 2012. CMP NMR spectroscopy permits the analysis of solid, gel and liquid phases in unaltered natural samples. Here the technology is applied to control and oil contaminated soils to understand the molecular processes that give rise to non-wettable soils. 13C solid-state NMR spectroscopy is found to be excellent for studying the bulk rigid compone...

Volcanic lakes are characterized by physicochemical favorable conditions for the development of reservoirs of C-bearing greenhouse gases that can be dispersed to air during occasional rollover events. By combining a microbiological and geochemical approach, we showed that the chemistry of the CO2- and CH4-rich gas reservoir hosted within the meromictic Lake Averno (Campi Flegrei, southern Italy) are related to the microbial niche differentiation along the vertical water column. The simultaneous occurrence of diverse functional groups of microbes operating under different conditions suggests that these habitats harbor complex microbial consortia that impact on the production and consumption of greenhouse gases. In the epilimnion, the activity of aerobic methanotrophic bacteria and photosynthetic biota, together with CO2 dissolution at relatively high pH, enhanced CO2- and CH4 consumption, which also occurred in the hypolimnion. Moreover, results from computations carried out to evalu...

Larval chironomids (mostly Chironomus tenuistylus) were collected from the sediments of five small forest lakes in southern Finland during summer 2002. Carbon and nitrogen isotope ratios of larvae were determined by isotope ratio mass spectrometry. Isotope ratio variability among 23 individuals from one lake was appreciable, with d 13 C showing a range spanning 1.6‰ and d 15 N values a range spanning 5.6‰. Between the lakes, larvae showed considerable variation in d 13 C with values as low as-55‰. d 15 N values were strongly correlated with d 13 C values. The 13 C-depletion found in the benthic chironomid larvae correlated with that found previously in zooplankton from the same lakes. It is argued that the low d 13 C values are most likely attributable to incorporation of carbon from biogenic methane, and that methane production can therefore make an important contribution to benthic as well as to pelagic food webs in these small forest lakes.

Biomass burning has a significant impact on global atmospheric chemistry since it provides large sources of carbon monoxide, nitrogen oxides, and hydrocarbons, primarily in the tropics [Crutzen et al., 1979. These gases are precursors of tropospheric ozone and influence the chemistry of the OH radical . Two notable components of biomass burning are the incineration of wood, charcoal and agricultural waste as household fuel, and the combustion of crop residue in open fields. As the developing world population continues to rise, the contributions from these types of biomass burning increase [Woods and Hall, 1994: hereafter referenced as WH94]. A quantitative description of the spatial distribution of biofuel and open field burning is required in order to assess the impact of this burning on the budgets of trace gases.

The BIODEP model in terms of atmosphere–lake interactions was developed. The model was applied to an oligotrophic, dimictic high altitude lake (Lake Redo, Pyrenees) for a range of polychlorinated biphenyl (PCB) congeners. High altitude lakes, which receive their contaminant inputs uniquely from the atmosphere through long-range atmospheric transport, provide ideal controlled environments for the study of the interactions between atmospheric depositional and water column biogeochemical processes. The BIODEP model was able to predict dissolved water concentrations and PCB accumulation in the lake sediment within a factor of 2. This shows that the BIODEP model captures the essential processes driving the sink of POPs in high altitude lakes and that POP occurrence in the lake is driven by direct atmospheric inputs with limited influence from the watershed. An important seasonal variability in water column concentrations is predicted which should have important implications in sampling strategies. Furthermore, it is shown that diffusive air–water exchange dominated the PCB dynamics in the lake, especially for the less chlorinated biphenyls.

The aim of the present study was to determine the distribution of per-and polyfluoroalkyl substances (PFASs) in three-egg clutches of Audouin's gull (Larus audouinii) breeding in Ebro Delta's colony according to the laying order (a, b and c eggs). Five PFASs were analyzed in 30 eggs (yolk and albumen separately), corresponding to 10 three-egg clutches. Carbon and nitrogen stable isotopes were measured as dietary tracers. PFASs were not detected in albumen. In egg yolks, perfluorooctane sulfonate (PFOS) was the main compound detected followed by perfluorononanoic acid (PFNA), perfluorohexane sulfonate (PFHS) and perfluorooctanoic acid (PFOA). Perfluorooctane sulfonate (PFBS) was not detected. Mean RPFASs for aeggs was of 236 ± 57 ng g À1 yolk wet weight (ww), for b-eggs was of 140 ± 56 ng g À1 yolk ww and for c-eggs, 133 ± 54 ng g À1 yolk ww. PFOS concentration decreased according to the laying order of the eggs, showing significant differences between consecutive eggs. In addition, significant correlation (r 2 s = 0.7-0.9) was observed for PFOS concentration within the eggs from the same clutch. No relationship was found between PFOS levels and stable isotopes signatures.

We invite systematic consideration of the metaphors of cycles and circulation as a long-term theme in the history of the life and environmental sciences and medicine. Ubiquitous in ancient religious and philosophical traditions, especially in representing the seasons and the motions of celestial bodies, circles once symbolized perfection. Over the centuries cyclic images in western medicine, natural philosophy, natural history and eventually biology gained independence from cosmology and theology and came to depend less on strictly circular forms. As potent ‘canonical icons’, cycles also interacted with representations of linear and irreversible change, including arrows, arcs, scales, series and trees, as in theories of the Earth and of evolution. In modern times life cycles and reproductive cycles have often been held to characterize life, in some cases especially female life, while human efforts selectively to foster and disrupt these cycles have harnessed their productivity in me...