Enhancement Of Primary Production Research Articles

Nutricline shoaling in the eastern Pacific warm pool during the last two glacial maxima

Isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) and alkenones were analyzed in sediment samples retrieved from Ocean Drilling Program Site 1241 covering the last 150000 years to understand the hydrological evolution of the eastern Pacific warm pool (EPWP). GDGT and alkenone concentrations showed higher values in marine isotope stage (MIS)-2 and MIS-6, which suggests the enhancement of primary production at glacial maxima. \( {\text{TEX}}_{86}^{\text{H}} \)- and \( U_{ 3 7^\prime }^{\text{K}} \)-derived temperature depicted different temperature evolutions. \( U_{ 3 7^\prime }^{\text{K}} \)-derived temperature was marked by small variation during the glacial–interglacial cycles, whereas \( {\text{TEX}}_{86}^{\text{H}} \)-derived temperature showed pronounced glacial–interglacial variation that was similar to Mg/Ca-derived temperature records from nearby cores in the EPWP. Given that enhanced primary production during glacial maxima suggests nutricline shoaling, unchanged \( U_{ 3 7^\prime }^{\text{K}} \) over glacial–interglacial cycles can be interpreted as the shift of alkenone production depth. \( {\text{TEX}}_{86}^{\text{H}} \) seems not to be influenced by glacial–interglacial changes in nutricline depths, recording an integrated temperature in surface and thermocline water. The shallow nutricline in the EPWP during glacial maxima most likely reflected the intense formation of Antarctic intermediate water.

Enhancement of primary production in the North Atlantic outside of the spring bloom, identified by remote sensing of ocean colour and temperature

The heterogeneity in phytoplankton production in the North Atlantic after the spring bloom is poorly understood. We analysed merged microwave and infrared satellite sea surface temperature (SST) data and ocean colour phytoplankton size class biomass, primary production (PP) and new production (ExP) derived from SeaWiFS data, to assess the spatial and temporal frequency of surface thermal fronts and areas of enhanced PP and ExP. Strong and persistent surface thermal fronts occurred at the Reykjanes Ridge (RR) and sub-polar front (SPF), which sustain high PP and ExP and, outside of the spring bloom, account for 9% and 15% of the total production in the North Atlantic. When normalised by area, PP at the SPF is four times higher than the RR. Analysis of 13years of satellite ocean colour data from SeaWiFS, and compared with MODIS-Aqua and MERIS, showed that there was no increase in Chla from 1998 to 2002, which then decreased in all areas from 2002 to 2007 and was most pronounced in the RR. These time series also illustrated that the SPF exhibited the highest PP and the lowest variation in Chla over the ocean colour record. This implies that the SPF provides a high and consistent supply of carbon to the benthos irrespective of fluctuations in the North Atlantic Oscillation.

In-situ analyses of phosphorus contents of carbonate minerals: Reconstruction of phosphorus contents of seawater from the Ediacaran to early Cambrian

The Ediacaran and Cambrian periods were one of the most important periods for the evolution of life. The biodiversity drastically expanded in the period. However, the origins are still ambiguous because surface environmental changes through the time have not been well understood yet. We conducted in-situ analyses of the phosphorus contents of carbonate minerals with a laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) to estimate the phosphorus contents of seawater from the Ediacaran to the early Cambrian. Carbonate rocks contain not only the carbonate minerals but also detrital and authigenic materials such as silicate and phosphate minerals. Therefore, the whole rock compositions of carbonate rocks are not directly related with seawater composition. To avoid the influence of the involvement of the phosphate minerals, we performed the microscopic observation, elemental mapping of Si, Ca, Mg, Fe, and P contents with an electron probe microanalyzer (EPMA), and investigation of time profiles of signal intensities of Ca, Sr, Mn, P, La and Ba with the LA-ICP-MS. Especially, samples with low Mn/Sr ratios and primary textures such as oolites are suitable to estimate the primary phosphorus contents of the carbonates.The chemostratigraphy of the phosphorus contents of carbonates from the drill core and outcrop samples displays that the phosphorus contents decrease from ca. 400ppm in the Ediacaran through ca. 200ppm around the terminal Ediacaran and the beginning of the Cambrian to ca. 50ppm in the early Cambrian. Previous works on 87Sr/86Sr chemostratigraphy from the Ediacaran to the Cambrian sections suggested relatively high continental influx in the middle Ediacaran, and around the Precambrian–Cambrian (PC/C) boundary. The high phosphorus content in the Ediacaran was possibly due to the high continental flux. On the other hand, previous works on chemostratigraphy of carbon isotope values of carbonate carbon from the Ediacaran to the Cambrian sections showed some large negative anomalies in the Ediacaran and around the Precambrian–Cambrian (PC/C) boundary, and suggested that the negative anomalies were caused by remineralization and respiration of dissolved organic matter. The degradation of the organic matter also accounts for the high phosphorus contents in the Ediacaran. The high phosphorus content of seawater favors enhancement of primary productivity and formation of phosphorites. The high phosphorus contents in the seawater possibly led to the emergence of the large, and motile organism through the enhancement of primary productivity and the consequent increase of oxygen content of the seawater.

Is biological productivity enhanced at the New England shelfbreak front?

A two‐dimensional (cross‐shelf) numerical model of the mean seasonal circulation offshore of southern New England predicts upwelling at the shelfbreak front. Expected ramifications of this upwelling include enhancement of nutrient supply, phytoplankton biomass, and productivity. However, seasonal climatologies of chlorophyll based on both in situ data and satellite observations show no mean enhancement at the front. We investigate this apparent discrepancy with a four‐component planktonic ecosystem model coupled to the two‐dimensional physical model. Nutrient fields are restored to climatological values at depth, and upper ocean values evolve freely according to physical and biological forcing. Vertical diffusivity is based on seasonally averaged surface and bottom mixed layer depths compiled from in situ observations. The model reproduces the general pattern of the observed cross‐shelf and seasonal variations of the chlorophyll distribution. It predicts a local enhancement of phytoplankton productivity at the shelfbreak in spring and summer as a result of the persistently upwelled nutrient‐rich slope water. In the model, zooplankton grazing prevents accumulation of phytoplankton biomass at the site of the upwelling. The predicted enhancement of primary productivity (but not phytoplankton biomass) at the shelfbreak constitutes a hypothesis that could be tested in the future with suitable measurements from regional long‐term observatories, such as the Ocean Observatories Initiative Pioneer Array.

Nitrogen fixation in the Gulf of California and the Eastern Tropical North Pacific

Di-nitrogen (N2) fixation plays a well-recognized role in the enhancement of primary production and arguably particle export in oligotrophic regions of the subtropical and tropical oceans. However, recent evidence suggests that N2 fixation may also be significant in regions of the surface ocean proximate to or overlying zones of intense subsurface denitrification. In this study, we present results from a series of research cruises in the Gulf of California (GoCal) and adjacent waters of the Eastern Tropical North Pacific (ETNP). Measurements include microscopy, genomic analyses, incubations, stable isotopic measurements, and sediment traps coupled with 238U:234Th disequilibria. Combined, these results suggest that N2 fixing microorganisms are present and active throughout the region, with larger sized Richelia and Trichodesmium spp. recorded within the warmer waters at the entrance to and within the GoCal, and smaller, unicellular diazotrophs observed in the cooler waters of the northern ETNP. N2 fixation rates in the summer varied from 15–70μmolNm−2d−1, with episodic blooms contributing as much as 795μmolNm−2d−1. While the estimated contribution of N2 fixation to particle export was highly variable, blooms of diatom-Richelia symbioses accounted for as much as ∼44% of the measured summer carbon flux at 100m. Alternately, evaluation of the N isotopic composition of sinking material and the magnitude of measured N2 fixation rates indicate negligible to small enhancements of new production when blooms of either colonial Trichodesmium spp. or unicellular diazotrophs were encountered. Consistent with previous research, we also found that while fluxes of C to sediment traps are similar in winter and summer months, the efficiency of C export (export/surface productivity) in the GoCal region is elevated during summer relative to the more productive diatom-dominated winter phase of the seasonal cycle. The episodic and variable nature of N2 fixation recorded in this region make it unlikely that new production via diazotrophic activity is solely responsible for the observed patterns of C transport efficiency; rather, we hypothesize that eolian inputs and/or efficient transport of picocyanobacterial biomass via grazing or aggregation may further explain the enhanced export efficiency observed in the GoCal summer. In sum, diazotrophy typically supports <10%, but as much as 44% of export production. The high variability of direct measurements of N2 fixation implies that other mechanisms contribute to the seasonal invariance of C flux in this region. If this region is indicative of other oxygen minima zones with active diazotrophs, our results indicate that export-mediated feedback mechanisms between N2 fixation and denitrification are not as strong as previously hypothesized.

Investigation of the biophysical processes over the oligotrophic waters of South Indian Ocean subtropical gyre, triggered by cyclone Edzani

The biophysical effects of a storm in the most oligotrophic waters of the South Indian Ocean (SIO) subtropical gyre have been investigated by conjunctive analyses using space-borne sensors and in situ observations. The most oligotrophic waters of the SIO are identified using more than 8-years of chlorophyll-a images derived from Aqua-Moderate Resolution Imaging Spectroradiometer (Aqua-MODIS). Earlier studies revealed that the source of oceanic primary production enhancement in these oligotrophic waters has remained inconclusive. However, the present study succeeded in attributing the cyclone, named Edzani, which passed over these waters and to be responsible for enriching the chlorophyll-a pigment, lowering of sea surface temperature (SST) and deepening of mixed layer. Analyses of MODIS Chlorophyll-a and SST images during the cyclone and pre-cyclone period shows lowering of SST values up to 2.23°C and chlorophyll-a enrichment up to 0.062mg/m3 from the pre-storm values along the cyclone track. Argo floats in the region recorded 10m deepening of mixed layer with an average mixed layer cooling of ∼1.34°C and 0.14‰ increase in salinity. These changes controlled by the physical processes have been examined using wind stress, wind stress curl and upwelling velocity derived from the new Advanced Scatterometer (ASCAT). The results provide a significant evidence to suggest that the frequent storms could possibly modify the prevailing oligotrophic conditions of the SIO subtropical gyres into a relatively productive environment, thus leading to regulate the global carbon cycle which is an essential component of climate change.

Forest productivity under elevated CO2 and O3: positive feedbacks to soil N cycling sustain decade-long net primary productivity enhancement by CO2

The accumulation of anthropogenic CO₂ in the Earth's atmosphere, and hence the rate of climate warming, is sensitive to stimulation of plant growth by higher concentrations of atmospheric CO₂. Here, we synthesise data from a field experiment in which three developing northern forest communities have been exposed to factorial combinations of elevated CO₂ and O₃. Enhanced net primary productivity (NPP) (c. 26% increase) under elevated CO₂ was sustained by greater root exploration of soil for growth-limiting N, as well as more rapid rates of litter decomposition and microbial N release during decay. Despite initial declines in forest productivity under elevated O₃, compensatory growth of O₃ -tolerant individuals resulted in equivalent NPP under ambient and elevated O₃. After a decade, NPP has remained enhanced under elevated CO₂ and has recovered under elevated O₃ by mechanisms that remain un-calibrated or not considered in coupled climate-biogeochemical models simulating interactions between the global C cycle and climate warming.

Consumers can enhance ecosystem productivity and stability in changing environments

AbstractThere is increasing interest in the impacts of pulsed resource inputs (e.g., seasonal fluctuations in primary production) on ecosystem properties. However, theoretical models have focused on the ecosystem role of consumers only in stable environments. We investigated how the consumption rate affects ecosystem properties when resource supplies are pulsed using a simple model with numerical simulations. We initially investigated how primary production responds to resource supply shortages under various consumption rates and found that a vigorous consumer attenuates a rapid reduction in primary production. We next examined ecosystem properties under pulsed resource supplies. Intermediate consumption enhances primary production. The consumption rate that maximizes productivity differs for producers and consumers in a given resource supply environment, irrespective of the pattern of pulsation. The enhancement of primary production and the maximization of secondary production occur simultaneously in a stable environment but are not always the same when the resource supply is pulsed. We also investigated the variability of primary production and found that intermediate consumption rates reduce its coefficient of variation. In addition, we found that consumers with either very low or very high consumption rates are vulnerable to extinction when resource supplies are pulsed. Therefore, consumers with intermediate consumption rates contribute not only to the enhancement and stabilization of primary production but also to the stability of the consumer population itself.

Elevated CO2 affects photosynthetic responses in canopy pine and subcanopy deciduous trees over 10 years: a synthesis from Duke FACE

AbstractLeaf responses to elevated atmospheric CO2 concentration (Ca) are central to models of forest CO2 exchange with the atmosphere and constrain the magnitude of the future carbon sink. Estimating the magnitude of primary productivity enhancement of forests in elevated Ca requires an understanding of how photosynthesis is regulated by diffusional and biochemical components and up‐scaled to entire canopies. To test the sensitivity of leaf photosynthesis and stomatal conductance to elevated Ca in time and space, we compiled a comprehensive dataset measured over 10 years for a temperate pine forest of Pinus taeda, but also including deciduous species, primarily Liquidambar styraciflua. We combined over one thousand controlled‐response curves of photosynthesis as a function of environmental drivers (light, air Ca and temperature) measured at canopy heights up to 20 m over 11 years (1996–2006) to generate parameterizations for leaf‐scale models for the Duke free‐air CO2 enrichment (FACE) experiment. The enhancement of leaf net photosynthesis (Anet) in P. taeda by elevated Ca of +200 μmol mol−1 was 67% for current‐year needles in the upper crown in summer conditions over 10 years. Photosynthetic enhancement of P. taeda at the leaf‐scale increased by two‐fold from the driest to wettest growing seasons. Current‐year pine foliage Anet was sensitive to temporal variation, whereas previous‐year foliage Anet was less responsive and overall showed less enhancement (+30%). Photosynthetic downregulation in overwintering upper canopy pine needles was small at average leaf N (Narea), but statistically significant. In contrast, co‐dominant and subcanopy L. styraciflua trees showed Anet enhancement of 62% and no Anet–Narea adjustments. Various understory deciduous tree species showed an average Anet enhancement of 42%. Differences in photosynthetic responses between overwintering pine needles and subcanopy deciduous leaves suggest that increased Ca has the potential to enhance the mixed‐species composition of planted pine stands and, by extension, naturally regenerating pine‐dominated stands.

Methane sources and sinks in Lake Kivu

Unique worldwide, Lake Kivu stores enormous amounts of CH 4 and CO 2 . A recent study reported that CH 4 concentrations in the lake have increased by up to 15% in the last 30 years and that accumulation at this rate could lead to catastrophic outgassing by ∼2100. This study investigates the present-day CH 4 formation and oxidation in Lake Kivu. Analyses of 14C and 13C in CH 4 and potential carbon sources revealed that below 260 m, an unusually high ∼65% of the CH 4 originates either from reduction of geogenic CO 2 with mostly geogenic H 2 or from direct inflows of geogenic CH 4 . Aerobic CH 4 oxidation, performed by close relatives of type X CH 4 -oxidizing bacteria, is the main process preventing CH 4 from escaping to the atmosphere. Anaerobic CH 4 oxidation, carried out by CH 4 -oxidizing archaea in the SO 4 2--reducing zone, was also detected but is limited by the availability of sulfate. Changes in 14C CH4 and 13C CH4 since the 1970s suggest that the amount of CH 4 produced from degrading organic material has increased due to higher accumulation of organic matter. This, as well as the sudden onset of carbonates in the 1960s, has previously been explained by three environmental changes: (1) introduction of nonnative fish, (2) amplified subaquatic inflows following hydrological changes, and (3) increased external inputs due to the fast growing population. The resulting enhancement of primary production and organic matter sedimentation likely caused CH 4 to increase. However, given the large proportion of old CH 4 carbon, we cannot exclude an increased inflow of geogenic H 2 or CH 4 . Copyright 2011 by the American Geophysical Union.

210Pb-derived Sedimentation Rates and Corg Fluxes in Soledad Lagoon (Cispatá Lagoon System, NW Caribbean Coast of Colombia)

With the aim of evaluating temporal changes in sedimentation and organic carbon (Corg) supplied over the last ~100 years, a sediment core was collected at Soledad Lagoon, a costal ecosystem surrounded by mangroves, located in the Cispata Estuary (Caribbean coast of Colombia). The core sediments were characterized by low concentrations of calcium carbonate (0.2–2.9%), organic matter (3–8%), total nitrogen (0.11–0.38%), and total phosphorus (0.19–0.65 mg g−1). Fe and Al concentrations ranged from 4% to 5%, and Mn from 356 to 1,047 μg g−1. The 210Pb-derived sediment and mass accumulation rates were 1.54 ± 0.18 mm year−1 and 0.08 ± 0.01 g cm−2 year−1, respectively. The sediment core did not provide evidence of human impact, such as enhancement of primary production or nutrient enrichment, which may result from recent land uses changes or climate change. The Corg fluxes estimated for Soledad Lagoon core lay in the higher side of carbon fluxes to coastal ecosystems (314–409 g m−2 year−1) and the relatively high Corg preservation observed (~45%) indicate that these lagoon sediments has been a net and efficient sink of Corg during the last century, which corroborate the importance of mangrove areas as important sites for carbon burial and therefore, long-term sequestration of Corg.

Biogeochemical implications of increased mineral particle concentrations in surface waters of the northwestern North Pacific during an Asian dust event

[1] Simultaneous observations were made in the marine atmospheric boundary layer and surface ocean during spring 2007 to investigate potential impacts of Asian dust on a semi-pelagic region of the northwestern North Pacific. The results suggest that mineral dust aerosols were scavenged by sea fog, and their deposition to the ocean increased the particle concentration in surface seawater. The atmospheric input of mineral dust to the ocean surface from this event was calculated to be 40 to 680 mg m−2 event−1. A general relationship for the solubility of iron from dust particles led to an estimate of 20 to 330 μg m−2 for the amount of bio-available iron delivered during the dust event. This input of bio-available iron is comparable to total dissolved iron added during an iron fertilization experiment in the northwestern North Pacific in which an enhancement of primary production was observed.

Phosphorus mass balance in a highly eutrophic semi-enclosed inlet near a big metropolis: A small inlet can contribute towards particulate organic matter production

Terrigenous loading into enclosed water bodies has been blamed for eutrophic conditions marked by massive algal growth and subsequent hypoxia due to decomposition of dead algal cells. This study aims to describe the eutrophication and hypoxia processes in a semi-enclosed water body lying near a big metropolis. Phosphorus mass balance in a small inlet, Ohko Inlet, located at the head of Hiroshima Bay, Japan, was quantified using a numerical model. Dissolved inorganic phosphorous inflow from Kaita Bay next to the inlet was five times higher than that from terrigenous load, which may cause an enhancement of primary production. Therefore, it was concluded that not only the reduction of material load from the land and the suppression of benthic flux are needed, but also reducing the inflow of high phosphorus and oxygen depleted water from Kaita Bay will form a collective alternative measure to remediate the environmental condition of the inlet.

Potential for remediation of acidic mining lakes evaluated by hydrogeochemical modelling: Case study Grünewalder Lauch (Plessa 117, Lusatia/Germany)

About one third of several hundred mining lakes in Eastern Germany are highly acidified, and there is a need to restore them to neutral conditions because they constitute an environmental hazard for water resources and downstream environments. The aim of this study is to evaluate the efficiency of three different acid pit lake water remediation treatments: dilution with alkaline (river) water, limestone treatment and biological neutralization by organic carbon-driven alkalinity generation. The efficiency is evaluated for the acidic mining lake Grünewalder Lauch by adjusting input values into a geochemical model and making future projections. Current approaches, such as flooding with neutral surface water or extensive liming, are not suitable for many lakes because of a limited supply of alkaline water or high lime immobilizing potential of Fe- and Al-rich water in acidic lakes, respectively. Further treatment methods are, therefore, designed to combine water supply and biological measures with the management of water quality by the application of in-lake microbial processes. These processes are focused on the metabolic response of aquatic ecosystems to nutrient enrichment (enhancement of primary production and thereby organic carbon supply) and the microbial decomposition of organic matter and their effects on the gain or loss of alkalinity. The results and comparisons of different neutralization measures will be generalized by the application of hydrogeochemical models for alkalinity production showing the long term efficiency of the measures, depending on carbon turnover at the sediment/water interface, the development of bicarbonate buffering capacity as a consequence of biological measures, the importance of pyrite formation instead of FeS.

海底マウンドによる人工湧昇流技術の包括的環境影響評価

Artificial upwelling is a technology aiming to increase the marine productivity by uplifting bottom seawater with rich nutrient to euphotic zone using artificial structure. The environmental impacts of an artificial upwelling technology using a seabed mound is inclusively assessed by using the Triple I (III: Inclusive Impact Index). Triple I is calculated based on ecological footprint (EF),biocapacity, ecological risk, human risk, cost, and benefit. In the calculation of EF, environmental impacts due to CO2 emission is estimated using input-output analysis considering indirect effects through the whole economy, which could be several times larger than the direct effects. It is also found that increase of biocapacity due to the enhancement of primary production will much greater than EF increase due to the construction of seabed mound. The value of III could significantly affected by the parameter γ which converts economic value (cost or benefit) to environmental value (EF). Based on a detail consideration about the parameter , a new method to calculate γ was proposed in which marginal abatement costs of CO2 emission and GDP produced by each industrial categories are utilized. III with proposed γ indicates that the artificial upwelling technology will be sustainable when the indirect effect is considered.

Re‐assessment of plant carbon dynamics at the Duke free‐air CO2 enrichment site: interactions of atmospheric [CO2] with nitrogen and water availability over stand development

*The potential for elevated [CO(2)]-induced changes to plant carbon (C) storage, through modifications in plant production and allocation of C among plant pools, is an important source of uncertainty when predicting future forest function. Utilizing 10 yr of data from the Duke free-air CO(2) enrichment site, we evaluated the dynamics and distribution of plant C. *Discrepancy between heights measured for this study and previously calculated heights required revision of earlier allometrically based biomass determinations, resulting in higher (up to 50%) estimates of standing biomass and net primary productivity than previous assessments. *Generally, elevated [CO(2)] caused sustained increases in plant biomass production and in standing C, but did not affect the partitioning of C among plant biomass pools. Spatial variation in net primary productivity and its [CO(2)]-induced enhancement was controlled primarily by N availability, with the difference between precipitation and potential evapotranspiration explaining most interannual variability. Consequently, [CO(2)]-induced net primary productivity enhancement ranged from 22 to 30% in different plots and years. *Through quantifying the effects of nutrient and water availability on the forest productivity response to elevated [CO(2)], we show that net primary productivity enhancement by elevated [CO(2)] is not uniform, but rather highly dependent on the availability of other growth resources.

Enhancement of phytoplankton primary productivity in the southern East China Sea following episodic typhoon passage

The enhancement of primary productivity (PPenh) in the southern East China Sea (ECS) following 16 typhoon passages was investigated using ocean color data and a primary productivity model. PPenh tended to be higher when typhoons traversed slowly with trajectories that allowed strong southerly winds to prevail over Yonaguni Island. Such long‐lasting southerly winds were believed to push the Kuroshio current axis shelfward, enhancing the upwelling of nutrients, hence promoting new productivity (NP). The importance of long‐lasting southerly winds as a proxy for physical perturbations underlying PPenh was expressed by an empirical equation by which 88% of PPenh variation could be explained. Applying this equation, we assessed that typhoon passages accounted for a minimum of 0.6–11.8% of the ECS summer–fall NP, suggesting that typhoon passage over the southern ECS is an important phenomenon supporting NP in the ECS.

Modelled effects of primary and secondary production enhancement by seamounts on local fish stocks

Abstract This paper addresses how large aggregations of fish found on many seamounts are sustained. We used a generic seamount ecosystem model from the Northeast Atlantic to examine the impact of a potential increase of local primary production on higher trophic levels, to quantify the immigration of allochthonous micronekton that would be required to maintain a “typical” seamount community, and to quantify if the necessary immigration ratios could be supported by local oceanographic conditions. Our simulation predictions indicate a lack of autochthonous resources in the system to support large amounts of seamount aggregating fish. In other words, autochthonous seamount production may be responsible for sustaining only a small amount of its total biomass. Additionally, our study supports the idea that enhancement of primary productivity also cannot sustain large aggregations of seamount fish. Our seamount model, which took into account high abundances of fish, marine mammals, seabirds and tuna, required a total immigration of allochthonous micronekton of 95.2 t km−2 yr−1 less than the potential available biomass after considering the immigration of prey based upon average current velocities and prey standing stocks in oceanic waters. Our model predicted that the horizontal flux of prey would be sufficient to sustain the rich communities living on seamounts.

Ocean physical and biogeochemical responses to the passage of Typhoon Meari in the East China Sea observed from Argo float and multiplatform satellites

We elucidated ocean physical and biogeochemical responses to slow‐moving Typhoon Meari using a new method combining Argo float and satellite observations. Meari‐driven upwelling brought colder, nutrient‐rich deep water to the surface layer, causing sea surface cooling (3–6°C) and threefold enhancement of primary production (PP). Maximum surface cooling (and hence nutrient injection) and peak PP enhancement lagged Meari's passage by 1 and 3 days, respectively, implying that remarkable PP enhancement was attributed to new production (NP). This NP accounted for approximately 3.8% of annual carbon export in the East China Sea (ECS) outer shelf, suggesting that typhoon‐driven upwelling is important for biogeochemical processes in the ECS. Given the wide coverage of Argo float and satellite data, our new approach may prompt comparative studies in other basins and advance the understanding of the role of tropical cyclones in the global ocean biogeochemical cycle.

Primary production enhancement by artificial upwelling in a western Norwegian fjord

To enhance primary production rate for shellfish cultivation in fjords, a large-scale artificial upwelling experiment was carried out in a western Norwegian fjord during the summers of 2004 and 2005. Pumping 2 m3 s–1 brackish surface water to a depth of 30 m created an artificial upwelling of nutrient-rich deeper water. The entrainment of deeper water into the buoyant brackish plume resulted in a transport of about 450 kg d–1 nitrate, 760 kg d–1 silicate and 75 kg d–1 phosphate to an intrusion depth of 8 to 10 m. The artificial upwelling approximately tripled mean chlorophyll a (chl a) concentration and related primary production rate during the summer within an influence area of 10 km2 near the head of the fjord. The size of the area of influence and the relative increase of the algae biomass within it depend on both the water exchange and the photosynthetic effectiveness. The relatively high silicate content of the deeper water stimulated diatom growth inside the area influenced by the artificial upwelling. A higher stable level of phytoplankton biomass, dominated by nontoxic species, would probably increase the carrying capacity of seston-feeding shellfish and could form the basis of more predictable mussel cultivation in fjords.