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Ocean production and trophic transfer rates, including Net Community Production (NCP), Net Primary Production (NPP), Gross Oxygen Production (GOP), and microzooplankton grazing rates are key metrics for understanding marine ecosystem dynamics and impacts on biogeochemical cycles. Because of its temperate location and high dynamic range of environmental conditions and long-term human utilization, the long-term ecological research site in the coastal Northeastern U.S. Shelf (NES) of the Northwestern Atlantic Ocean offers an ideal opportunity to understand how productivity shifts in response to changes in planktonic community composition. While small phytoplankton usually dominate in the NES waters during the summer, a bloom of the large diatom genus Hemiaulus, with N2 fixing symbionts, was observed in the mid-shelf region during the summer of 2019. NCP was 2.5 to 9 times higher when Hemiaulus dominated compared to NCP throughout the same geographic area during the summers of 2020--2022. The Hemiaulus bloom in summer 2019 also coincided with higher trophic transfer efficiency from phytoplankton to microzooplankton, higher GOP and NPP, and higher sea surface temperatures than summers 2020-2022. This study shows that the presence of an atypical phytoplankton community that alters the typical size distribution of the primary producers can greatly influence productivity and trophic transfer, highlighting the dynamic nature of the coastal ocean. Notably, summer 2018 NCP levels were also high although no atypical phytoplankton community was present. A better understanding of the dynamics of the NES in terms of biological productivity is of primary importance, especially in the context of changing environmental conditions due to climate processes. [ABSTRACT FROM AUTHOR]

Estimates of marine net primary production (NPP) commonly rely on limited in situ 14C incubations or satellite‐based algorithms mainly constrained to the surface ocean. Here we combine data from biogeochemical Argo floats with a carbon‐based productivity model (CbPM) to compute vertically resolved estimates of NPP. Inferred NPP profiles derived by informing the CbPM with float‐based, depth‐resolved, bio‐optical data are able to qualitatively reproduce the vertical structure in NPP inferred from in situ 14C incubations at various ocean regions. At station ALOHA, float‐based estimates agree within uncertainty with productivity observations at depth, but underestimate surface NPP. We test the ability of the CbPM to infer the depth‐resolved structure in NPP from bio‐optical properties in the mixed layer, in similar fashion as how remote sensing algorithms of ocean productivity operate. In Southern Ocean waters, the depth‐reconstructing implementation of the CbPM overestimates phytoplankton division rates and Chl:C below the mixed layer, resulting in artificially high subsurface NPP when compared with the fully float‐informed implementation of the model. The CbPM subsurface extrapolation of phytoplankton Chl, Chl:C, division rates, and NPP improves by accounting for deep nutrient (iron) stress impacts on photoacclimation in the Southern Ocean. This improvement is also observed in vertically integrated NPP, where the mean bias between model implementations in depth‐integrated productivity south of 30°S is reduced by 62% when account for deep iron limitation. Our results demonstrate that profiling data from biogeochemical Argo floats can serve to inform regional adjustments that lead to the improvement of marine productivity algorithms. Plain Language Summary: The oceanic production of organic carbon by photosynthesis is a key process that regulates marine food‐webs and the planet's climate. This production takes place not only at the surface of the ocean, but also in the subsurface, where it is difficult for ocean‐viewing satellites to retrieve accurate information. In this work, we combine information on water column biogeochemical properties collected by bio‐optical sensors on autonomous profiling floats with a mathematical model to estimate biological primary production throughout the water column. Our results show that this combination of model and float data can reproduce depth profiles of productivity observed in various ocean regions. We also test the ability of the model to infer subsurface productivity in Southern Ocean waters based on information of averaged biogeochemical properties in the surface ocean mixed layer alone. We find that the model improves the estimation of subsurface productivity when accounting for the limiting effect of scarce nutrients in Antarctic waters, such as iron. Our results provide confidence in the combination of float data and existing models to describe the vertical structure in marine biological productivity, and guide the improvement of productivity algorithms in specific regions of the global ocean. Key Points: Net primary production (NPP) estimates from the float‐informed carbon‐based productivity model (CbPM) can reproduce the vertical structure in 14C‐based productivity observed in various ocean regionsAccounting for deep iron limitation improves the reconstruction of depth‐resolved biomass and productivity by the CbPM in the Southern OceanThe inclusion of deep iron limitation potentially reduces the bias in Southern Ocean estimates of depth‐integrated NPP by 62% [ABSTRACT FROM AUTHOR]

Drought, as an intermittent disturbance of the water cycle, profoundly impacts the terrestrial ecosystem. Recovery time (RT) of an ecosystem from drought is an important indicator of assessing drought impacts and ecosystem resilience, yet the spatiotemporal pattern of ecosystem postdrought RT remains controversial in existing studies. Here we investigate the spatiotemporal pattern of postdrought RT across global terrestrial ecosystems using two observation‐based gross primary productivity (GPP) data sets: direct flux‐site observations and gridded estimates by upscaling flux‐site observations using machine‐learning approach. For droughts that occur on average once every 5.2 years, the RT typically ranges between 2 and 8 months, with a global mean RT of ∼6 months. Spatially, both GPP data sets show a significant bilinear relationship between RT and moisture gradient, and that ecosystems in arid and humid regions tend to recover from drought more rapidly than semi‐arid/sub‐humid ecosystems. Additionally, forests show an overall longer RT than shrublands and grasslands. Temporally, global ecosystem RT shows a slight yet significant increasing trend (0.032 months yr−1) during 1982–2010, which is partly caused by the increasing drought for the same period. However, the observed patterns of RT across global bio‐climatic zones are not captured by the state‐of‐the‐art land surface models, which exhibit a shorter RT in semi‐arid/sub‐humid ecosystems but longer RT in arid/humid regions, and a larger increasing trend of RT over time (0.069 months yr−1). Our findings provide crucial insights into ecosystem vulnerability to sub‐decadal stress events and ecosystem recovery trajectories among diverse bio‐climatic regions and highlight potential model deficiencies that should be accounted for in future model developments. Plain Language Summary: Recovery time (RT) of an ecosystem from drought is an important indicator of assessing drought impacts and ecosystem resilience. Here we investigate the spatiotemporal pattern of postdrought RT across global terrestrial ecosystems using two observation‐based gross primary productivity (GPP) data sets. Our results show that ecosystems in arid and humid regions tend to recover from drought more rapidly than semi‐arid/sub‐humid ecosystems. Unfortunately, this observed spatial pattern can hardly be captured by the state‐of‐the‐art LSMs, implying the lack of crucial representations of the physiological mechanisms driving diverse drought recovery features. In addition, we find a slight increase in global ecosystem RT throughout 1982–2010, which is partly caused by the increasing drought for the same period. Our findings provide crucial insights into ecosystem vulnerability to droughts and ecosystem recovery trajectories among diverse bio‐climatic regions and highlight potential model deficiencies that should be accounted for in future model developments. Key Points: Arid and humid ecosystems exhibit a relatively more rapid recovery after droughtPostdrought recovery time (RT) shows an increasing trend over the past three decadesPatterns of observed postdrought RT are not captured by ecosystem models [ABSTRACT FROM AUTHOR]

Temperature sensitivity of phytoplankton growth rate is crucial for predicting the effect of global warming on oceanic primary productivity and the efficiency of the biological carbon pump. To investigate how nutrient availability affects the temperature sensitivity of phytoplankton growth, we estimated the activation energy (Ea) of two dominant picocyanobacteria (Prochlorococcus and Synechococcus) in the subtropical northwest Pacific using short-term temperature modulated dilution experiments. We also conducted a meta-analysis on a compiled dataset of picocyanobacteria growth rate estimated by the dilution technique. Our results revealed that the Ea of Synechococcus growth rate under in situ nutrient conditions was lower than under nutrient-replete conditions. The growth response of Synechococcus to warming could, therefore, be weaker under nutrient-limiting conditions than in nutrient-replete waters. In contrast, Ea values of Prochlorococcus growth rate showed no difference between the two nutrient supply scenarios. We also found that the reduced Ea of Synechococcus growth was most likely related to the increasing trend of the half-saturation constants for growth with increasing temperature. The temperature sensitivity of half-saturation constants and the level of nutrient limitation can counteract the response of Synechococcus growth rate to increasing temperature. Our results highlight the importance of considering nutrient availability when evaluating the responses of phytoplankton growth and primary production to climate warming, especially in the oligotrophic ocean. [ABSTRACT FROM AUTHOR]

The accumulation of carbon of organic matter by forest phytocenoses during photosynthesis is their most important function, mitigating climate change on the Earth. The literature provides data that the territory of the Russian Federation is a large sink of atmospheric carbon. However, the estimates of the sink, as well as the values ​​of the net primary production (NPP) of forest ecosystems, vary widely. This paper presents materials describing the net carbon production of phytomass in pine forests of different types of growing conditions in the northern and middle taiga of the Komi Republic. Premature, mature, and old-growth pine forests of green moss, lichen, and sphagnum types have been studied at forest stations. The carbon sequestration by the forest stand is assessed by biological productivity using sample trees. The regression equations for the dependence of the increments of individual organs of a sample tree on the stem diameter at a height of 1.3 m are composed. A statistically significant relationship is found between these parameters, characterized by high trend approximation values ​​varying from 0.44 to 0.99 (at 95% significance level). It is calculated that, under the conditions of the European Russian northeast, the NPP of carbon in pine phytocenoses varies within the range of 1.9–4.5 t C ha–1 year–1. It is established that the tree stand accounts for 32–73% of the total NPP. With increasing soil moisture and moving northward, the participation of plants in the ground vegetation increases in the total NPP. It is noted that a significant part of the NPP of carbon of the tree layer of pine forests is formed by the photosynthetic apparatus and the stem wood. Based on these data, the conversion relations between NPP and wood volume/carbon stock in the stand for pine forests of the northern and middle taiga are derived. [ABSTRACT FROM AUTHOR]

The fixation of inorganic carbon species like CO 2 to more reduced organic forms is one of the most fundamental processes of life as we know it. Although several carbon fixation pathways are known to exist, on Earth today nearly all global carbon fixation is driven by the Calvin cycle in oxygenic photosynthetic plants, algae, and Cyanobacteria. At other times in Earth history, other organisms utilizing different carbon fixation pathways may have played relatively larger roles, with this balance shifting over geological time as the environmental context of life has changed and evolutionary innovations accumulated. Among the most dramatic changes that our planet and the biosphere have undergone are those surrounding the rise of O 2 in our atmosphere—first during the Great Oxygenation Event at ∼2.3 Ga, and perhaps again during Neoproterozoic or Paleozoic time. These oxygenation events likely represent major step changes in the tempo and mode of biological productivity as a result of the increased productivity of oxygenic photosynthesis and the introduction of O 2 into geochemical and biological systems, and likely involved shifts in the relative contribution of different carbon fixation pathways. Here, we review what is known from both the rock record and comparative biology about the evolution of carbon fixation pathways, their contributions to primary productivity through time, and their relationship to the evolving oxygenation state of the fluid Earth following the evolution and expansion of oxygenic photosynthesis. Image 1 • There are several carbon fixation pathways that have evolved. • Pathways responsible for bulk primary productivity have changed over time. • It is important to distinguish between stem and crown group lineages. [ABSTRACT FROM AUTHOR]

Modelling forest biomass sensitive to climate change is fulfilled at the levels as forest stands and singletrees, but mostly on a local or regional level, often without regard to the age, morphology of the forest stands and species composition. With this, it does not provide additive component composition, according to which the total of biomass components (stems, branches, needles, and roots), obtained by component equations, would be equal to the value of the biomass obtained by the general equation. The influence of climate change on the biomass of a tree species in the format of additive models for transcontinental hydrothermal gradients has not yet been studied. In the present study, the first attempt is made to model changes in the additive component composition of the stand biomass and NPP of two-needled pines along Trans-Eurasian hydrothermal gradients. In the process of modelling the database of pine stand biomass in a number of 2460 sample plots with the definitions of biomass and 760 plots with the definitions of biomass and annual NPP compiled by the authors, is used. [ABSTRACT FROM AUTHOR]

Enclosed seas are suitable for bivalve farming due to high primary production, which provides food sources. The impact of oyster farming on the biological productivity of lower trophic levels was evaluated in Hiroshima Bay. The area-weighted mean primary production in the estuary (northeastern bay; NB) was 1.1 to 2.1 times higher than that of the offshore area (southwestern bay; SB) in all four seasons. In contrast, the area-weighted mean secondary production by net zooplankton in the NB was lower than that of the SB, except in August. The area-weighted mean secondary production by oysters in the NB was 2.2 to 2.8 times higher than that of the SB in all four seasons, and exhibited a similar spatial pattern to that of the primary production. The primary production was more efficiently utilized and transferred to secondary producers in the SB (16.7% on average) than in the NB (9.4% on average). This study provides guidance for oyster farming in Japan. [ABSTRACT FROM AUTHOR]

In situ oxygen tracers (triple oxygen isotope and oxygen/argon ratios) were used to evaluate meridional trends in surface biological production and export efficiency across ~8000 km of the tropical and subtropical South Atlantic in March-May 2013. We used observations of picophytoplankton, nanophytoplankton, and microphytoplankton to evaluate community structure and diversity and assessed the relationships of these characteristics with production, export efficiency, and particulate organic carbon (POC) fluxes. Rates of productivity were relatively uniform along most of the transect with net community production (NCP) between 0 and 10 mmol O2 m−2 d−1, gross primary production (GPP) between 40 and 100 mmol O2 m−2 d−1, and NCP/GPP, a measure of export efficiency, ranging from 0.1 to 0.2 (0.05-0.1 in carbon units). However, notable exceptions to this basin-scale homogeneity included two locations with highly enhanced NCP and export efficiency compared to surrounding regions. Export of POC and particulate nitrogen, derived from sediment traps, correlated with GPP across the transect, over which the surface community was dominated numerically by picophytoplankton. NCP, however, did not correlate with POC flux; the mean difference between NCP and POC flux was similar to published estimates of dissolved organic carbon export from the surface ocean. The interrelated rates of production presented in this work contribute to the understanding, building on the framework of better-studied ocean basins, of how carbon is biologically transported between the atmosphere and the deep ocean. [ABSTRACT FROM AUTHOR]

The ocean off the Baja California Peninsula (Mexico) has been affected by interannual processes. Some of these processes have produced changes in oceanic circulation and the atmosphere, which have been reflected in the structure of the water column. Stratification, defined as the amount of energy needed to mix water throughout the water column, determines nutrient availability in the euphotic zone for phytoplankton growth. The aim of this study is to describe and relate the interannual variations of phytoplankton production and biomass with changes in the structure of the water column. To this end we analyzed time series (1997-2016) for integrated Chlorophyll a, integrated primary production, pycnocline depth, mixed layer depth, and stratification indices along line 100 of the Investigaciones Mexicanas de la Corriente de California (IMECOCAL) program. The results showed 2 periods of high stratification and a decrease in phytoplankton production and biomass off Baja California, corresponding to the intrusion of subarctic water and El Niño 2015-2016. Finally, by using generalized additive models, we related 2 photosynthethic parameters-maximum photosynthetic rate and maximum light utilization coefficient-with water stratification. These relationships explained interannual variations in phytoplankton production in terms of water column stratification. The time series and the analysis reported here for IMECOCAL line 100 could be used to extrapolate the effects of interannual physical processes on phytoplankton in other zones off the Baja California peninsula. [ABSTRACT FROM AUTHOR]

In our recent study in Global Change Biology (Li et al.,), we examined the relationship between solar‐induced chlorophyll fluorescence (SIF) measured from the Orbiting Carbon Observatory‐2 (OCO‐2) and gross primary productivity (GPP) derived from eddy covariance flux towers across the globe, and we discovered that there is a nearly universal relationship between SIF and GPP across a wide variety of biomes. This finding reveals the tremendous potential of SIF for accurately mapping terrestrial photosynthesis globally. [ABSTRACT FROM AUTHOR]

Multi-proxy biomarker measurements were applied on two sediment cores (PS51/154, PS51/159) to reconstruct sea ice cover (IP 25 ), biological production (brassicasterol, dinosterol) and river run-off (campesterol, β-sitosterol) in the western Laptev Sea over the last ∼17 ka with unprecedented temporal resolution. The absence of IP 25 from 17.2 to 15.5 ka, in combination with minimum concentration of phytoplankton biomarkers, suggests that the western Laptev Sea shelf was mostly covered with permanent sea ice. Very minor river run-off and restricted biological production occurred during this cold interval. From ∼16 ka until 7.5 ka, a long-term decrease of terrigenous (riverine) organic matter and a coeval increase of marine organic matter reflect the gradual establishment of fully marine conditions in the western Laptev Sea, caused by the onset of the post-glacial transgression. Intensified river run-off and reduced sea ice cover characterized the time interval between 15.2 and 12.9 ka, including the Bølling/Allerød warm period (14.7–12.9 ka). Prominent peaks of the DIP 25 Index coinciding with maximum abundances of subpolar foraminifers, are interpreted as pulses of Atlantic water inflow on the western Laptev Sea shelf. After the warm period, a sudden return to severe sea ice conditions with strongest ice-coverage between 11.9 and 11 ka coincided with the Younger Dryas (12.9–11.6 ka). At the onset of the Younger Dryas, a distinct alteration of the ecosystem (reflected in a distinct drop in terrigenous and phytoplankton biomarkers) was detected. During the last 7 ka, the sea ice proxies reflect a cooling of the Laptev Sea spring/summer season. This cooling trend was superimposed by a short-term variability in sea ice coverage, probably representing Bond cycles (1500 ± 500 ka) that are related to solar activity changes. Hence, atmospheric circulation changes were apparently able to affect the sea ice conditions on the Laptev Sea shelf under modern sea level conditions. [ABSTRACT FROM AUTHOR]

A dynamic mass-balance model has been presented for the biotic energy flux in the ecosystem of the Boguchanskoe Reservoir (Angara River, Irkutsk oblast). It has been revealed that this model is controlled by the small number of input parameters and is intended for prediction of the biomass and annual production of primary producers, reducers, and consumers from various orders, including fish. The model algorithm has been described. [ABSTRACT FROM AUTHOR]

We show in the present study that variations in the rates of survival and recruitment of the agile gracile opossum ( Gracilinanus agilis) are predominantly influenced by its life history instead of the variation in primary productivity that is common in the Brazilian Cerrado. For 5 years we monitored a population of G. agilis in a riparian forest running through the Cerrado and assessed the relationship between survival and breeding season, as well as the relationship between recruitment and seasons (dry and rainy). We also tested for a relationship between these rates and variations in primary productivity. The survival of males was better predicted by reproductive season than primary productivity and survival decreased after the reproductive season. Females showed a similar pattern. Our data show the reproduction of G. agilis is seasonal, with recruitment in the rainy season. The demographic analysis made in the present study suggests the adoption of a semelparous strategy in this species. [ABSTRACT FROM AUTHOR]

In recent years, droughts have frequently hit China's terrestrial ecosystems. How these droughts affected carbon sequestration by China's terrestrial ecosystems is still unclear. In this study, the process-based Boreal Ecosystem Productivity Simulator (BEPS) model, driven by remotely sensed vegetation parameters, was employed to assess the effects of droughts on net ecosystem productivity (NEP) of terrestrial ecosystems in China for the period from 2000 to 2011. Different categories of droughts, as indicated by a standard precipitation index (SPI), extensively hit terrestrial ecosystems in China, particularly in 2001, 2006, 2009 and 2011. The national total NEP exhibited a slight decline of -11.3 TgCyr-2 during the study period, mainly due to large reductions of NEP in typical drought-hit years 2001, 2006, 2009 and 2011, ranging from 61.1 TgCyr-1 to 168.8 TgCyr-1. National and regional total NEP anomalies were correlated with corresponding annual mean SPI, especially in Northwest China, North China, Central China, and Southwest China. In drought years, the reductions of NEP might be caused by a larger decrease in gross primary productivity (GPP) than in respiration (RE) (2001 and 2011), a decrease in GPP and an increase in RE (2009), or a larger increase in RE than in GPP (2006). Droughts had lagged effects of up to 3-6 months on NEP due to different reactions of GPP and RE to droughts. In east humid and warm parts of China, droughts have predominant and short-term lagged influences on NEP. In western cold and arid regions, the effects of droughts on NEP were relatively weaker and might last for a longer period of time. [ABSTRACT FROM AUTHOR]

Environmental change strongly affects primary productivity of ecosystems via modifying bottom-up and top-down regulation of primary producers. Here we present a novel approach to quantify the relative importance of regulating factors in natural systems over various time scales: we calculated daily effect sizes of major factors affecting phytoplankton growth during the spring bloom period during almost three decades of lake oligotrophication using numerical experiments with a data based simulation model. We show that with oligotrophication the regulation of spring phytoplankton shifts from primarily top-down to bottom-up, and that the changes in regulation are non-linearly related to the nutrient (phosphorus) concentrations. Our findings indicate that long-term changes in top-down regulation cannot be understood without considering multiple herbivore taxa, here, microzooplankton (ciliates) and mesozooplankton (daphnids). We further demonstrate that bottom-up and top-down regulation are not independent from each other and that their interaction is time-scale dependent. [ABSTRACT FROM AUTHOR]

Archaeologists interested in explaining changes in artifact morphology over long time periods have found it useful to create models in which the only source of change is random and unintentional copying error, or 'cultural mutation'. These models can be used as null hypotheses against which to detect non-random processes such as cultural selection or biased transmission. One proposed cultural mutation model is the accumulated copying error model, where individuals attempt to copy the size of another individual's artifact exactly but make small random errors due to physiological limits on the accuracy of their perception. Here, we first derive the model within an explicit mathematical framework, generating the predictions that multiple independently-evolving artifact chains should diverge over time such that their between-chain variance increases while the mean artifact size remains constant. We then present the first experimental test of this model in which 200 participants, split into 20 transmission chains, were asked to faithfully copy the size of the previous participant's handaxe image on an iPad. The experimental findings supported the model's prediction that between-chain variance should increase over time and did so in a manner quantitatively in line with the model. However, when the initial size of the image that the participants resized was larger than the size of the image they were copying, subjects tended to increase the size of the image, resulting in the mean size increasing rather than staying constant. This suggests that items of material culture formed by reductive vs. additive processes may mutate differently when individuals attempt to replicate faithfully the size of previously-produced artifacts. Finally, we show that a dataset of 2601 Acheulean handaxes shows less variation than predicted given our empirically measured copying error variance, suggesting that other processes counteracted the variation in handaxe size generated by perceptual cultural mutation. [ABSTRACT FROM AUTHOR]

To date, no direct measurements of primary production were taken in the Amundsen Sea, which is one of the highest primary productivity regions in the Antarctic. Phytoplankton carbon and nitrogen uptake experiments were conducted at 16 selected stations using a C-N dual isotope tracer technique. We found no statistically significant depletions of major inorganic nutrients (nitrate + nitrite, ammonium, and silicate) although the concentrations of these nutrients were markedly reduced in the surface layer of the polynya stations where large celled phytoplankton (>20 μm) predominated (ca. 64 %). The average chl- a concentration was significantly higher at polynya stations than at non-polynya stations ( p < 0.01). Average daily carbon and nitrogen uptake rates by phytoplankton at polynya stations were 2.2 g C m day (SD = ±1.4 g C m day) and 0.9 g N m day (SD = ±0.2 g N m day), respectively, about 5-10 times higher than those at non-polynya stations. These ranges are as high as those in the Ross Sea, which has the highest productivity among polynyas in the Antarctic Ocean. The unique productivity patterns in the Amundsen Sea are likely due to differences in iron limitation, phytoplankton productivity, the timing of phytoplankton growing season, or a combination of these factors. [ABSTRACT FROM AUTHOR]

The radiation use efficiency (RUE) model is one of the most used tools to generate large spatial and temporal scale net primary productivity (NPP) estimations by remote sensing. It involves two key issues to make accurate estimations of NPP: the estimation of the fraction of photosynthetically active radiation (PAR) intercepted by vegetation (fPAR) and the estimation of the plant RUE. The objectives of this work were to quantify the above-ground RUE under optimal water and nutrient conditions in two C3 and one C4 grass species and to analyse the effect of restrictions in these factors upon RUE by comparing both metabolic pathways. Grasses were cultivated from seeds and four treatments combining contrasting availabilities of water and nutrients were applied. RUE values were calculated from measurements of the incoming PAR, fPAR and productivity. In each of the species, plants with sufficient water and nutrients showed the highest RUE (2.61-3.52 g MJ−1), whereas those with deficiencies in both resources presented the lowest RUE (1.15-2.39 g MJ−1). Cynodon dactylon (C4) was the species with higher value of RUE and no significant differences were detected between treatments. However, no significant differences were detected between C. dactylon and D. glomerata under no stress treatment (N1W1) and between C. dactylon and L. perenne under water stress treatment (N1W0). RUE values of Dactylis glomerata (C3) diminished if only one of the two stress factors was presented, while Lolium perenne (C3) only when both stress factors were present. The decreases under stress treatments were between 35% and 60% compared with the no stress treatment. When regional NPP is estimated it is therefore important to take into account the decrease in the RUE, especially in areas under severe stress. [ABSTRACT FROM AUTHOR]

The primary productivity of the river River Kharashrota (Orissa) has been analysed both spatially and seasonally. The maximum GPP was noted during summer season and minimum in rainy season at all the six stations. The annual average GPP varied from 0.075±0.009 gC.m-3.h-1 to 0.938±0.103 gC.m-3.h-1.The NPP value varied from 0.012±0.001 gC.m-3.h-1 to 0.832±0.081 gC.m-3.h-1 and exhibited an increasing trend from the month of September to February. The community respiration (CR) ranged from 0.026±0.002 gC.m-3.h-1 to 0.496±0.043 gC.m-3.h-1 and exhibited a systematic seasonal pattern with maximum and minimum value during summer and winter respectively at all the stations. The correlation of NPP, GPP and CR with some of the physico-chemical parameters has also been established. [ABSTRACT FROM AUTHOR]

Abstract: Net primary productivity (NPP) estimation is an important study field of global change and terrestrial ecosystem. Here, we present an integrated modeling system for NPP estimation. It''s brings together remote sensing, GIS and an ecosystem estimation model without requiring users to have any knowledge of any other specific software. The benefit of the system is that it provides complete spatial coverage and high temporal resolution, versus plot samples from which it may be difficult to provide an overall assessment for large-scale study. Recent advances in serviceoriented architectures are allowing us to share of model results by geospatial services and create distributed applications needed for the collaborative research. Multi-layer approaches allow the system more flexible and easy to extend. A preliminary system was carried out for monitoring the dynamic changes of terrestrial ecosystem NPP in China. State-of-the art processing algorithms was developed based on an improved CASA ecosystem model. And then, the NPP time-series of Chinese terrestrial vegetation is built. The System is capable of querying, retrieving, and visualizing datasets with heterogeneous formats. The results show that the average NPP and total NPP for the study area in 2006 were 298.9 gC m-2 yr-1 and 2.839 Pg C respectively. The modeled results illustrate a high degree of spatial and temporal heterogeneity. [Copyright &y& Elsevier]

Prochlorococcus contributes significantly to ocean primary productivity. The link between primary productivity and iron in specific ocean regions is well established and iron limitation of Prochlorococcus cell division rates in these regions has been shown. However, the extent of ecotypic variation in iron metabolism among Prochlorococcus and the molecular basis for differences is not understood. Here, we examine the growth and transcriptional response of Prochlorococcus strains, MED4 and MIT9313, to changing iron concentrations. During steady state, MIT9313 sustains growth at an order-of-magnitude lower iron concentration than MED4. To explore this difference, we measured the whole-genome transcriptional response of each strain to abrupt iron starvation and rescue. Only four of the 1159 orthologs of MED4 and MIT9313 were differentially expressed in response to iron in both strains. However, in each strain, the expression of over a hundred additional genes changed, many of which are in labile genomic regions, suggesting a role for lateral gene transfer in establishing diversity of iron metabolism among Prochlorococcus. Furthermore, we found that MED4 lacks three genes near the iron-deficiency-induced gene (idiA) that are present and induced by iron stress in MIT9313. These genes are interesting targets for studying the adaptation of natural Prochlorococcus assemblages to local iron conditions as they show more diversity than other genomic regions in environmental metagenomic databases. [ABSTRACT FROM AUTHOR]

The article focuses on the relationship between photochemical reflectance index (PRI) and light use efficiency (LUE) for global monitoring of plant primary productivity from space. It notes that the relationship of PRI with LUE is reinforced by the fact that PRI measures the relative reflectance on either side of the green reflectance hump of the ecosystems. It explores the consistency between PI and LUE and the calculations involved during environmental monitoring.

Using long-term (22 years) measurements from a young and an old-growth subtropical forest in southern China, we found that both forests accumulated carbon from 1982 to 2004, with the mean carbon accumulation rate at 227 ± 59 g C m year for young forest and 115 ± 89 g C m year for the old-growth forest. Allocation of the accumulated carbon was quite different between these two forests: the young forest accumulated a significant amount of carbon in plant live biomass, whereas the old-growth forest accumulated a significant amount of carbon in the soil. From 1982 to 2004, net primary productivity (NPP) increased for the young forest, and did not change significantly for the old-growth forest. The increase in NPP of the young forest resulted from recruitment of some dominant tree species characteristic of the subtropical mature forest in the region and an increase in tree density; decline of NPP of the old-growth forest was caused by increased mortality of the dominant trees. [ABSTRACT FROM AUTHOR]

Abstract: The High Nutrient Low Chlorophyll (HNLC) Southern Ocean plays a key role in regulating the biological pump and the global carbon cycle. Here we examine the efficacy of stable cadmium (Cd) isotope fractionation for detecting differences in biological productivity between regions. Our results show strong meridional Cd isotope and concentration gradients modulated by the Antarctic Fronts, with a clear biogeochemical divide located near 56°S. The coincidence of the Cd isotope divide with the Southern Boundary of the Antarctic Circumpolar Current (ACC),together with evidence for northward advection of the Cd signal in the ACC, demonstrate that Cd isotopes trace surface ocean circulation regimes. The relationships between Cd isotope ratios and concentrations display two negative correlations, separating the ACC and Weddell Gyre into two distinct Cd isoscapes. These arrays are consistent with Rayleigh fractionation and imply a doubling of the isotope effect due to biological consumption of Cd during water transport from the Weddell Gyre into the ACC. The increase in magnitude of Cd isotope fractionation can be accounted for by differences in the phytoplankton biomass, community composition, and their physiological uptake mechanisms in the Weddell Gyre and ACC, thus linking Cd isotope fractionation to primary production and the global carbon cycle. [Copyright &y& Elsevier]

The idea that species diversity can influence ecosystem functioning has been controversial and its importance relative to compositional effects hotly debated. Unfortunately, assessing the relative importance of different explanatory variables in complex linear models is not simple. In this paper we assess the relative importance of species richness and species composition in a multilevel model analysis of net aboveground biomass production in grassland biodiversity experiments by estimating variance components for all explanatory variables. We compare the variance components using a recently introduced graphical Bayesian ANOVA. We show that while the use of test statistics and the R2 gives contradictory assessments, the variance components analysis reveals that species richness and composition are of roughly similar importance for primary productivity in grassland biodiversity experiments. [ABSTRACT FROM AUTHOR]

Foraminiferal data were obtained from 66 samples of box cores on the southeastern Brazilian upper margin (between 23.8°-25.9°S and 42.8°-46.13°W) to evaluate the benthic foraminiferal fauna distribution and its relation to some selected abiotic parameters. We focused on areas with different primary production regimes on the southern Brazilian margin, which is generally considered as an oligotrophic region. The total density ( D), richness ( R), mean diversity ( $$ \overline{{H^{\prime } }} $$), average living depth (ALD) and percentages of specimens of different microhabitats (epifauna, shallow infauna, intermediate infauna and deep infauna) were analyzed. The dominant species identified were Uvigerina spp. , Globocassidulina subglobosa, Bulimina marginata, Adercotryma wrighti, Islandiella norcrossi, Rhizammina spp. and Brizalina sp .. We also established a set of mathematical functions for analyzing the vertical foraminiferal distribution patterns, providing a quantitative tool that allows correlating the microfaunal density distributions with abiotic factors. In general, the cores that fit with pure exponential decaying functions were related to the oligotrophic conditions prevalent on the Brazilian margin and to the flow of the Brazilian Current (BC). Different foraminiferal responses were identified in cores located in higher productivity zones, such as the northern and the southern region of the study area, where high percentages of infauna were encountered in these cores, and the functions used to fit these profiles differ appreciably from a pure exponential function, as a response of the significant living fauna in deeper layers of the sediment. One of the main factors supporting the different foraminiferal assemblage responses may be related to the differences in primary productivity of the water column and, consequently, in the estimated carbon flux to the sea floor. Nevertheless, also bottom water velocities, substrate type and water depth need to be considered. [ABSTRACT FROM AUTHOR]

During the last decade, global tidal models have spectacularly improved. However, they still have difficulties in resolving tides over continental shelves and near coastlines. This study of tidal propagation from the continental shelf to the North Patagonia Gulfs of Argentina applies a set of three nested high resolution models based on the Hamburg shelf ocean model (HamSOM), where particular attention was paid to the bathymetry and the coast line. The study is complemented by the use of all the tidal gauge and tidal current observations available. Simulations display good agreement with observations, permitting the construction of higher resolution and more reliable cotidal and corange charts. The tidal regime in the area is essentially semidiurnal and dominated by M2. This constituent propagates northward as a Kelvin wave and reaches the gulfs from the south. In their interior an important amplification is observed. Tidal currents are large at the mouths of the gulfs, and weaken toward their interior. The nonlinear transfer of energy from the semidiurnal to higher order harmonics was analyzed. This can be very important in the interior of the gulfs, particularly in Nuevo Gulf and in the northwestern San Matías Gulf, close to San Antonio. Energy flux and energy dissipation by bottom friction has been computed and indicate that this region dissipates 17% of the total energy dissipated on the Patagonian Shelf which, in turn, is one of the most dissipative areas of the world ocean. The Simpson-Hunter parameter computed from the simulations shows that in the mouth of the gulfs, particularly in San Matías and east of the Península de Valdés, the tides are energetic enough to overcome stratification and produce tidal fronts. The locations where tidal fronts are located are highly consistent with results from sea surface temperature and primary productivity data analyzed by other authors. [ABSTRACT FROM AUTHOR]

Using estimates of the primary production required (PPR) to support fisheries catches (a measure of the footprint of fishing), we analyzed the geographical expansion of the global marine fisheries from 1950 to 2005. We used multiple threshold levels of PPR as percentage of local primary production to define 'fisheries exploitation' and applied them to the global dataset of spatially-explicit marine fisheries catches. This approach enabled us to assign exploitation status across a 0.5° latitude/longitude ocean grid system and trace the change in their status over the 56-year time period. This result highlights the global scale expansion in marine fisheries, from the coastal waters off North Atlantic and West Pacific to the waters in the Southern Hemisphere and into the high seas. The southward expansion of fisheries occurred at a rate of almost one degree latitude per year, with the greatest period of expansion occurring in the 1980s and early 1990s. By the mid 1990s, a third of the world's ocean, and two-thirds of continental shelves, were exploited at a level where PPR of fisheries exceed 10% of PP, leaving only unproductive waters of high seas, and relatively inaccessible waters in the Arctic and Antarctic as the last remaining 'frontiers.' The growth in marine fisheries catches for more than half a century was only made possible through exploitation of new fishing grounds. Their rapidly diminishing number indicates a global limit to growth and highlights the urgent need for a transition to sustainable fishing through reduction of PPR. [ABSTRACT FROM AUTHOR]

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Plant-based defence mutualisms utilize plant morphology to reduce the performance of plant parasites through their natural enemies. Leaf domatia primarily occur in the axials of secondary veins and are often inhabited by microbivorous and predaceous mites which often increase plant growth rates and reproductive success by controlling plant pests. Our study investigated if domatia investment is limited by plant primary productivity. To our knowledge no studies have tested if foliar domatia are resource-limited. We tested our hypothesis using the genus Coprosma (Rubiaceae), conducting correlative field surveys and manipulative experiments measuring domatia production in new leaves along temperature, nutrient and irradiance gradients. Field surveys indicated a strong positive association between leaf area, the number of secondary veins, and domatia per leaf. The number of potential sites for domatia is underutilised, with leaves on selected Coprosma species having on average 47 to 72% of the 'maximum' number of available sites where domatia could occur. Foliar carbon was positively associated with domatia investment. Coprosma plants held under elevated night-time temperatures showed a 34-91% decrease in daily carbon gain, a 38% decrease in domatia per leaf mass, and a positive relationship between domatia investment and integrated daily carbon gain. Under irradiance and nutrient stress, our data indicated evidence of a positive relationship between domatia investment and foliar carbon. We found a significant negative association between relative investment in domatia produced and investment in new leaf biomass. Our findings suggest investment in foliar domatia is limited by primary productivity. We propose that domatia are discretionary goods and not intrinsic structures produced automatically on leaves that mites utilize. We suggest that plants have the ability to regulate domatia formation during leaf ontogeny, with investment controlled by resource availability and some intrinsic allocation mechanism to defence. [ABSTRACT FROM AUTHOR]

Phosphorus cycling between components of the ecosystem of the hypertrophic Lake Swarzędzkie was studied in 2000-2003. The results of this study revealed considerable seasonal variation in phosphorus cycling. The main sources of phosphorus load in winter were the tributaries, whereas in summer internal loading prevailed. However, the most effective source of SRP (soluble reactive phosphorus) for phytoplankton primary production in summer was its excretion by organisms from the microbial loop. The share of this source in the total phosphorus pool was 38%, whereas internal loading contributed 23.7%, external loading 16.3%, and regeneration by metazooplankton 22%. This exerted a significant influence on the functioning of the whole lake ecosystem. Limiting both external and internal phosphorus loading is recommended to facilitate water quality improvement in the lake. [ABSTRACT FROM AUTHOR]

Abstract: In order to understand the oceanographic changes before the Guadalupian–Lopingian (Permian) boundary mass extinction event, we investigated the isotopic compositions of the inorganic carbon and the oxygen (δ 13Ccarb and δ 18Ocarb) of the Guadalupian (Middle Permian) shallow marine carbonates deposited on a seamount-top in the superocean Panthalassa. The drilled samples were obtained at Kaerimizu in the Akiyoshi area, SW Japan. We focused on the Roadian-Wordian (Middle Guadalupian) interval that spans over 7 fusuline zones; i.e. the Parafusulina kaerimizuensis Zone (Pk Z.), Afghanella ozawai Zone (Ao Z.), Neoschwagerina craticulifera robusta Zone (Ncr Z.), Verbeekina verbeeki – Afghanella schenki Zone (Vv – As Z.), Neoschwageina fusifor m is Zone (Nf Z.), Verbeekina verbeeki Zone (Vv Z.), and Colania douvillei Zone (Cd Z.), in ascending order. Analytical results showed that the δ 13Ccarb values stayed almost constant around +3.0‰ PDB in the Pk Z., Ao Z. and the lower half of the Ncr Z., and those in the upper-section gradually decreased down to −2.0‰, of which the lowest was found in the Cd Z. We statistically extracted the samples with presumably better preserved δ 13Ccarb values in the Kaerimizu section ranged between +0.5 and +4.0‰ with average values of δ 13Ccarb of +2.7±1.0‰, on the basis of δ 13Ccarb–δ 18Ocarb characterization. This interval shows a monotonous decrease in δ 13Ccarb values from ca +4.0‰ to +2.0‰. This indicates that the primary productivity might be generally high in the Wordian mid-oceanic domain but slightly declined in the Late Wordian. The studied Early-Middle Guadalupian interval is chemostratigraphically correlated with the other mid-Pansalassan paleo-atoll limestone e.g. Iwato Formation in Japan, suggesting that the relatively high δ 13Ccarb (over +3.0‰) of seawater predominated in shallow mid-superocean during the middle Middle Permian. [Copyright &y& Elsevier]

We investigated the effect of elevated [CO2] (700 μmol mol−1), elevated temperature (+2 °C above ambient) and decreased soil water availability on net photosynthesis ( Anet) and water relations of one-year old potted loblolly pine ( Pinus taeda L.) seedlings grown in treatment chambers with high fertility at three sites along a north-south transect covering a large portion of the species native range. At each location (Blairsville, Athens and Tifton, GA) we constructed four treatment chambers and randomly assigned each chamber one of four treatments: ambient [CO2] and ambient temperature, elevated [CO2] and ambient temperature, ambient [CO2] and elevated temperature, or elevated [CO2] and elevated temperature. Within each chamber half of the seedlings were well watered and half received much less water (1/4 that of the well watered). Measurements of net photosynthesis ( Anet), stomatal conductance ( gs), leaf water potential and leaf fluorescence were made in June and September, 2008. We observed a significant increase in Anet in response to elevated [CO2] regardless of site or temperature treatment in June and September. An increase in air temperature of over 2 °C had no significant effect on Anet at any of the sites in June or September despite over a 6 °C difference in mean annual temperature between the sites. Decreased water availability significantly reduced Anet in all treatments at each site in June. The effects of elevated [CO2] and temperature on gs followed a similar trend. The temperature, [CO2] and water treatments did not significantly affect leaf water potential or chlorophyll fluorescence. Our findings suggest that predicted increases in [CO2] will significantly increase Anet, while predicted increases in air temperature will have little effect on Anet across the native range of loblolly pine. Potential decreases in precipitation will likely cause a significant reduction in Anet, though this may be mitigated by increased [CO2]. [ABSTRACT FROM AUTHOR]

Primary production at Antarctic coastal sites is contributed from sea ice algae, phytoplankton and benthic algae. Oxygen microelectrodes were used to estimate sea ice and benthic primary production at several sites around Casey, a coastal area in eastern Antarctica. Maximum oxygen export from sea ice was 0.95 mmol O2 m−2 h−1 (~11.7 mg C m−2 h−1) while from the sediment it was 6.08 mmol O2 m−2 h−1 (~70.8 mg C m−2 h−1). When the ice was present O2 export from the benthos was either low or negative. Sea ice algae assimilation rates were up to 3.77 mg C (mg Chl- a)−1 h−1 while those from the benthos were up to 1.53 mg C (mg Chl- a)−1 h−1. The contribution of the major components of primary productivity was assessed using fluorometric techniques. When the ice was present approximately 55–65% of total daily primary production occurred in the sea ice with the remainder unequally partitioned between the sediment and the water column. When the ice was absent, the benthos contributed nearly 90% of the primary production. [ABSTRACT FROM AUTHOR]

Many recent field experiments have examined plant responses to global change factors such as climate warming, elevated atmospheric CO2, increased nitrogen addition or altered precipitation simulated at the plot level, yet the mechanisms underlying these responses can be difficult to isolate. One concern has been that the infrastructure used in these experiments can restrict the access of influential herbivores, detritivores or pollinators to the plots, and the absence of these animals is confounded with the treatment effects. However, in this paper we describe why free access by animals to experimental plots does not ensure realistic animal densities in response to global change treatments. On the contrary, much like moths swarm around streetlamps, animals that prefer the local conditions in treated plots may congregate at artificially high densities, or conversely, those that are repelled by the treatments may choose to avoid them. Therefore, animal densities or herbivore damage in the plots of global change experiments may grossly exaggerate or underestimate the contributions of animals to primary productivity or plant species composition under future environmental conditions. We describe how these potential animal congregation and avoidance artifacts may have been overlooked in the interpretation of results from many plot-level global change field experiments. We also provide suggestions for how to best interpret the results of these experiments and how to isolate the effects of animal density artifacts. [ABSTRACT FROM AUTHOR]

In the Southern Ocean, mixing and upwelling in the presence of heat and freshwater surface fluxes transform subpycnocline water to lighter densities as part of the upward branch of the Meridional Overturning Circulation (MOC). One hypothesized impact of this transformation is the restoration of nutrients to the global pycnocline, without which biological productivity at low latitudes would be catastrophically reduced. Here we use a novel set of modeling experiments to explore the causes and consequences of the Southern Ocean nutrient return pathway. Specifically, we quantify the contribution to global productivity of nutrients that rise from the ocean interior in the Southern Ocean, the northern high latitudes, and by mixing across the low latitude pycnocline. In addition, we evaluate how the strength of the Southern Ocean winds and the parameterizations of subgridscale processes change the dominant nutrient return pathways in the ocean. Our results suggest that nutrients upwelled from the deep ocean in the Antarctic Circumpolar Current and subducted in Subantartic Mode Water support between 33 and 75% of global primary productivity between 30° S and 30° N. The high end of this range results from an ocean model in which the MOC is driven primarily by wind-induced Southern Ocean upwelling, a configuration favored due to its fidelity to tracer data, while the low end results from an MOC driven by high diapycnal diffusivity in the pycnocline. In all models, the high preformed nutrients subducted in the SAMW layer are converted rapidly (in less than 40 years) to remineralized nutrients, explaining previous modeling results that showed little influence of the drawdown of SAMW surface nutrients on atmospheric carbon concentrations. [ABSTRACT FROM AUTHOR]

Black carbon (BC) is an important pool of the global C cycle, because it cycles much more slowly than others and may even be managed for C sequestration. Using stable isotope techniques, we investigated the fate of BC applied to a savanna Oxisol in Colombia at rates of 0, 11.6, 23.2 and 116.1 t BC ha−1, as well as its effect on non-BC soil organic C. During the rainy seasons of 2005 and 2006, soil respiration was measured using soda lime traps, particulate and dissolved organic C (POC and DOC) moving by saturated flow was sampled continuously at 0.15 and 0.3 m, and soil was sampled to 2.0 m. Black C was found below the application depth of 0–0.1 m in the 0.15–0.3 m depth interval, with migration rates of 52.4±14.5, 51.8±18.5 and 378.7±196.9 kg C ha−1 yr−1 (±SE) where 11.6, 23.2 and 116.1 t BC ha−1, respectively, had been applied. Over 2 years after application, 2.2% of BC applied at 23.2 t BC ha−1 was lost by respiration, and an even smaller fraction of 1% was mobilized by percolating water. Carbon from BC moved to a greater extent as DOC than POC. The largest flux of BC from the field (20–53% of applied BC) was not accounted for by our measurements and is assumed to have occurred by surface runoff during intense rain events. Black C caused a 189% increase in aboveground biomass production measured 5 months after application (2.4–4.5 t additional dry biomass ha−1 where BC was applied), and this resulted in greater amounts of non-BC being respired, leached and found in soil for the duration of the experiment. These increases can be quantitatively explained by estimates of greater belowground net primary productivity with BC addition. [ABSTRACT FROM AUTHOR]

Recent studies have suggested that gross primary production (GPP) of terrestrial vegetation can be estimated directly with the satellite-based Enhanced Vegetation Index (EVI). However, the reported EVI–GPP relationships showed wide variability, with the regression functions showing widely scattered data. In the present study, we examined the possible reasons for this variability in the EVI–GPP relationship using daily EVI values from satellite and field measurements and daily flux-based GPP in a cool-temperate deciduous broad-leaved forest in Japan. The variability appears to be caused by noise due to cloud contamination in the satellite data as well as the different seasonality of EVI and GPP, especially during the leaf-expansion period. Our findings indicate that improvement of cloud screening and consideration of the leaf-expansion period are critical when applying the EVI–GPP relationship. [ABSTRACT FROM AUTHOR]

Global warming is predicted to alter the ocean's biological productivity. But how will we recognise the impacts of climate change on ocean productivity? The most comprehensive information available on the global distribution of ocean productivity comes from satellite ocean colour data. Now that over ten years of SeaWiFS data have accumulated, can we begin to detect and attribute global warming trends in productivity? Here we compare recent trends in SeaWiFS data to longer-term records from three biogeo-chemical models (GFDL, IPSL and NCAR). We find that detection of real trends in the satellite data is confounded by the relatively short time series and large interannual and decadal variability in productivity. Thus, recent observed changes in chlorophyll, primary production and the size of the oligotrophic gyres cannot be unequivocally attributed to the impact of global warming. Instead, our analyses suggest that a time series of ~40 yr length is needed to distinguish a global warming trend from natural variability. Analysis of modelled chlorophyll and primary production from 2001-2100 suggests that, on average, the global warming trend will not be unambiguously separable from decadal variability until ~2055. Because the magnitude of natural variability in chlorophyll and primary production is larger than, or similar to, the global warming trend, a consistent, decades-long data record must be established if the impact of climate change on ocean productivity is to be definitively detected. [ABSTRACT FROM AUTHOR]

Abstract: Saanich Inlet is a highly productive temperate fjord with the capability to record inter-annual patterns of water-column primary production in undisturbed laminated sediments. We investigated spatial and temporal variations in primary productivity, total and size-fractionated phytoplankton chl a, dissolved nutrients, temperature and salinity at the head and mouth of Saanich Inlet from May 2005 to November 2006. New primary productivity was also measured from May to October 2006. During the growing season (spring, summer and fall), primary productivity was 1.5 times higher at the mouth than at the head of Saanich Inlet and, averaged across stations, total productivity was 460gCm−2 y−1. Average new productivity was 53% and 58% of total primary productivity at the head and mouth of the inlet, respectively, and during the growing season micro-phytoplankton (>20μm; mainly diatoms) was the most abundant size-class of phytoplankton. These rates of primary production are as high as or higher than those measured in other fjords, possibly because of a tidally-driven fortnightly gravity exchange that supplies nutrients to surface waters that enhance biological production when nutrients would otherwise be limiting. This exchange delivers nutrients at least as far inland as the head station, while nutrients associated with an eddy near the mouth may be the cause of even higher productivity there. We discuss the impact of these nutrient sources to Saanich Inlet on the records of paleoproduction generated from two Ocean Drilling Program cores extracted from this fjord, and suggest that the fortnightly exchange buffers variations in nutrient supply occurring on sub-decadal or decadal scales. [Copyright &y& Elsevier]

• Respiration consumes a large portion of annual gross primary productivity in forest ecosystems and is dominated by belowground metabolism. Here, we present evidence of a previously unaccounted for internal CO2 flux of large magnitude from tree roots through stems. If this pattern is shown to persist over time and in other forests, it suggests that belowground respiration has been grossly underestimated. • Using an experimental Populus deltoides plantation as a model system, we tested the hypothesis that a substantial portion of the CO2 released from belowground autotrophic respiration remains within tree root systems and is transported aboveground through the xylem stream rather than diffusing into the soil atmosphere. • On a daily basis, the amount of CO2 that moved upward from the root system into the stem via the xylem stream (0.26 mol CO2 m−2 d−1) rivalled that which diffused from the soil surface to the atmosphere (0.27 mol CO2 m−2 d−1). We estimated that twice the amount of CO2 derived from belowground autotrophic respiration entered the xylem stream as diffused into the soil environment. • Our observations indicate that belowground autotrophic respiration consumes substantially more carbohydrates than previously recognized and challenge the paradigm that all root-respired CO2 diffuses into the soil atmosphere. [ABSTRACT FROM AUTHOR]

1. Assessments of flow abstractions in streams often focus on changes to biological communities and in-stream physical characteristics, with little consideration for changes in ecosystem functioning. It is unclear whether functional indicators of ecosystem health may be useful for assessing the impacts of reduced discharge on small streams. 2. We used weirs and diversions to reduce stream discharge by over 89% in three small New Zealand streams (11–84 L s−1), ranging in water quality from pristine to moderately impaired. 3. We used both structural (benthic invertebrates) and functional (drifting invertebrates, leaf breakdown, coarse particulate organic matter (CPOM) retention and primary productivity) measures of ecosystem integrity to compare responses to water abstraction in before-after, control-impact designed experiments during summer 2005. 4. At the pristine site, the density of invertebrates, taxon richness, Macroinvertebrate Community Index (MCI), Quantitative MCI, percentage of Ephemeroptera, Plecoptera and Trichoptera individuals and percentage of filter-feeders decreased in response to reduced flows. Only taxon richness decreased at the mildly impaired stream, and reduced discharge had no effect on the invertebrate community at the stream with the lowest water quality. 5. We found that reduced discharge had little influence on the breakdown rate of willow leaves in mesh bags over 1 month. Primary productivity was also relatively insensitive to water abstraction. However, CPOM retention increased with decreased flows. Drift propensity of invertebrates increased at two sites but only within the first few days after flow reduction. 6. Structural measures of ecosystem integrity suggested that the impacts of water abstraction differed among streams of varying water quality, probably because of differences in the sensitivity of invertebrate assemblages in the three streams. In contrast, the three functional measures tested were generally less sensitive to water abstraction impacts, although understanding how stream ecosystems respond to water abstraction clearly requires that both are considered. [ABSTRACT FROM AUTHOR]

This study analyzes 9 years of eddy-covariance (EC) data carried out in a Pacific Northwest Douglas-fir ( Pseudotsuga menzesii) forest (58-year old in 2007) on the east coast of Vancouver Island, Canada, and characterizes the seasonal and interannual variability in net ecosystem productivity (NEP), gross primary productivity (GPP), and ecosystem respiration ( Re) and primary climatic controls on these fluxes. The annual values (± SD) of NEP, GPP and Re were 357 ± 51, 2124 ± 125, and 1767 ± 146 g C m−2 yr−1, respectively, with ranges of 267–410, 1592–2338, and 1642–2071 g C m−2 yr−1, respectively. Spring to early summer (March–June) accounted for more than 80% of annual NEP while late spring to early autumn (May–August) was mainly responsible for its interannual variability (∼80%). The major drivers of interannual variability in annual carbon (C) fluxes were annual and spring mean air temperatures ( Ta) and water deficiency during late summer and autumn (July–October) when this Douglas-fir forest growth was often water-limited. Photosynthetically active radiation ( Q), and the combination of Q and soil water content ( θ) explained 85% and 91% of the variance of monthly GPP, respectively; and 91% and 96% of the variance of monthly Re was explained by Ta and the combination of Ta and θ, respectively. Annual net C sequestration was high during optimally warm and normal precipitation years, but low in unusually warm or severely dry years. Excluding 1998 and 1999, the 2 years strongly affected by an El Niño/La Niña cycle, annual NEP significantly decreased with increasing annual mean Ta. Annual NEP will likely decrease whereas both annual GPP and Re will likely increase if the future climate at the site follows a trend similar to that of the past 40 years. [ABSTRACT FROM AUTHOR]

Afforestations can be considerable carbon (C) sources due to C losses from the soil after site preparation for tree planting and decreased primary production. In this study, the transition from grassland to afforestation was investigated using two eddy flux towers, which were operated in parallel for 3 years, one on a young afforestation and one on an adjacent grassland. Differences between the fluxes at the two sites were attributable to the management of the sites, without confounding influences of meteorological variability. Site preparation with deep ploughing of the planting rows destroyed 30% of the grassland vegetation at the afforestation site and reduced gross primary productivity by 41% in the first year. At the afforestation site 38 g m−2 less C was sequestered compared with the nonafforested grassland during the first year. In the following years, the C sink at the afforestation site was higher than at the grassland indicating that soil C loss due to site preparation and land use change on the afforestation occurred only during the first year. Metrological conditions, especially summer drought, caused a high interannual variability of the C balance: both sites were small C sources in 2005 (67 g C m−2 a−1 at the grassland and 19 g C g−1 a−1 at the afforestation site) and small C sinks in 2004 and 2006 (−72.5 and −16 g C m−2 a−1 at the grassland and −34 and −61 g C g−1 a−1 at the afforestation). Sheep grazing and mowing affected the short-term dynamics of the C balance and sheep grazing accelerated the C turnover on the grassland site. The investigated afforestation site did not provide any short-term way of sequestering additional C even though soil C losses during the first 3 years were relatively small. [ABSTRACT FROM AUTHOR]

There is widespread concern that loss of biodiversity can influence important ecosystem services. A positive relationship between diversity and productivity has been observed in investigations of terrestrial and aquatic plant communities. However, an increase in primary production (carbon assimilation) does not necessarily result in higher nutrient uptake by primary producers. There is a loose coupling between carbon assimilation and nutrient uptake in autotrophs, and their biomass carbon-to-nutrient ratios (stoichiometry) are flexible. We performed controlled laboratory experiments to investigate the effect of phytoplankton biodiversity on phytoplankton stoichiometry. Our results indicate that biodiversity influences carbon assimilation and nutrient uptake of phytoplankton communities in different ways, resulting in variations of biomass stoichiometry. Data from 46 lake communities also support this link. Shifts in the biomass stoichiometry of phytoplankton communities are generally attributed to environmental fluctuations in resources. However, our results show that biodiversity is also important in determining their stoichiometry. [ABSTRACT FROM AUTHOR]

The article focuses on the influence of coastal water darkening in fjords in Norway. It notes that light regime of the water column has a robust structuring impact on aquatic food webs. It adds that it is believed that coastal water darkening has increased the success of tactile predators in terms to visual predators including fish. Moreover, it states that water light attenuation is a crucial ecosystem variable due to its effect on primary production. It suggests that darkening needs to be taken into account in the analyses of mesopelagic regime shifts involving mass occurrence of the jellyfish Periphylla periphylla.

Electronic tags were used to examine the seasonal movements, aggregations and diving behaviors of Atlantic bluefin tuna (Thunnus thynnus) to better understand their migration ecology and oceanic habitat utilization. Implantable archival tags (n = 561) were deployed in bluefin tuna from 1996 to 2005 and 106 tags were recovered. Movement paths of the fish were reconstructed using light level and sea-surface-temperature-based geolocation estimates. To quantify habitat utilization we employed a weighted kernel estimation technique that removed the biases of deployment location and track length. Throughout the North Atlantic, high residence times (167633 days) were identified in four spatially confined regions on a seasonal scale. Within each region, bluefin tuna experienced distinct temperature regimes and displayed different diving behaviors. The mean diving depths within the high-use areas were significantly shallower and the dive frequency and the variance in internal temperature significantly higher than during transit movements between the high-use areas. Residence time in the more northern latitude high-use areas was significantly correlated with levels of primary productivity. The regions of aggregation are associated with areas of abundant prey and potentially represent critical foraging habitats that have seasonally abundant prey. Throughout the North Atlantic mean diving depth was significantly correlated with the depth of the thermocline, and dive behavior changed in relation to the stratification of the water column. In this study, with numerous multi-year tracks, there appear to be repeatable patterns of clear aggregation areas that potentially are changing with environmental conditions. The high concentrations of bluefin tuna in predictable locations indicate that Atlantic bluefin tuna are vulnerable to concentrated fishing efforts in the regions of foraging aggregations. [ABSTRACT FROM AUTHOR]

The modern Eastern Equatorial Pacific (EEP) Ocean is a large oceanic source of carbon to the atmosphere. Primary productivity over large areas of the EEP is limited by silicic acid and iron availability, and because of this constraint the organic carbon export to the deep ocean is unable to compensate for the outgassing of carbon dioxide that occurs through upwelling of deep waters. It has been suggested that the delivery of dust-borne iron to the glacial ocean could have increased primary productivity and enhanced deep-sea carbon export in this region, lowering atmospheric carbon dioxide concentrations during glacial periods. Such a role for the EEP is supported by higher organic carbon burial rates documented in underlying glacial sediments, but lower opal accumulation rates cast doubts on the importance of the EEP as an oceanic region for significant glacial carbon dioxide drawdown. Here we present a new silicon isotope record that suggests the paradoxical decline in opal accumulation rate in the glacial EEP results from a decrease in the silicon to carbon uptake ratio of diatoms under conditions of increased iron availability from enhanced dust input. Consequently, our study supports the idea of an invigorated biological pump in this region during the last glacial period that could have contributed to glacial carbon dioxide drawdown. Additionally, using evidence from silicon and nitrogen isotope changes, we infer that, in contrast to the modern situation, the biological productivity in this region is not constrained by the availability of iron, silicon and nitrogen during the glacial period. We hypothesize that an invigorated biological carbon dioxide pump constrained perhaps only by phosphorus limitation was a more common occurrence in low-latitude areas of the glacial ocean. [ABSTRACT FROM AUTHOR]

Seabirds are an important link between their marine feeding areas and their terrestrial breeding environments, transporting both marine-derived nutrients and contaminants and then depositing them on land in their guano. In this study, the impact of a large northern fulmar (Fulmarus glacialis) colony on the water chemistry of 26 nearby ponds spanning a gradient of seabird influence was investigated at Cape Vera, Devon Island, in the Canadian High Arctic. The presence of the fulmar colony has led to nutrient and trace element enrichment in the ponds, as evidenced by the close association among As, Cd, Co, Cu, Li, Mn, Mo, Ni, Sb, and Sr and the ornithogenic gradient. The ponds most affected by the fulmar colony were characterized by increased primary production, high organic carbon concentrations, and elevated pH — conditions favorable for the in situ removal of metals from the water column. Despite this, the highest trace element concentrations were observed in the seabird-influenced ponds, suggesting that these elements have undergone biotransport. [ABSTRACT FROM AUTHOR]