The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
David M. Karl - One of the best experts on this subject based on the ideXlab platform.
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Dissolved Inorganic Phosphorus Dissolved iron and trichodesmium in the oligotrophic south china sea
Global Biogeochemical Cycles, 2003Co-Authors: Shi-wei Chung, Liang-saw Wen, Kon Kee Liu, Yuh-ling Lee Chen, Houng Y. Ng Chen, David M. KarlAbstract:[1] Dissolved Inorganic Phosphorus (DIP) concentrations in the oligotrophic surface waters of the South China Sea decrease from ∼20 nM in March 2000 to ∼5 nM in July 2000, in response to seasonal water column stratification. These minimum DIP concentrations are one order of magnitude higher than those in the P-limited, iron-replete stratified surface waters of the western North Atlantic, suggesting that the ecosystem in the South China Sea may be limited by bioavailable nitrogen or some trace nutrient rather than DIP. Nutrient enrichment experiments using either nitrate, phosphate or both indicate that nitrogen limits the net growth of phytoplankton in the South China Sea, at least during March and July 2000. The fixed nitrogen limitation may result from the excess phosphate (N:P<16) transported into the South China Sea from the North Pacific relative to microbial population needs, or from iron control of nitrogen fixation. The iron-limited nitrogen fixation hypothesis is supported by the observation of low population densities of Trichodesmium spp. (<48 × 103 trichomes/m3), the putative N2 fixing cyanobacterium, and with low concentrations of Dissolved iron (∼0.2–0.3 nM) in the South China Sea surface water. Our results suggest that nitrogen fixation can be limited by available iron even in regions with a high rate of atmospheric dust deposition such as in the South China Sea.
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Dissolved Inorganic Phosphorus, Dissolved iron, and Trichodesmium in the oligotrophic South China Sea
Global Biogeochemical Cycles, 2003Co-Authors: Shi-wei Chung, Liang-saw Wen, Kon Kee Liu, Yuh-ling Lee Chen, Houng Y. Ng Chen, David M. KarlAbstract:[1] Dissolved Inorganic Phosphorus (DIP) concentrations in the oligotrophic surface waters of the South China Sea decrease from ∼20 nM in March 2000 to ∼5 nM in July 2000, in response to seasonal water column stratification. These minimum DIP concentrations are one order of magnitude higher than those in the P-limited, iron-replete stratified surface waters of the western North Atlantic, suggesting that the ecosystem in the South China Sea may be limited by bioavailable nitrogen or some trace nutrient rather than DIP. Nutrient enrichment experiments using either nitrate, phosphate or both indicate that nitrogen limits the net growth of phytoplankton in the South China Sea, at least during March and July 2000. The fixed nitrogen limitation may result from the excess phosphate (N:P
Klaas R. Timmermans - One of the best experts on this subject based on the ideXlab platform.
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Uptake kinetics and storage capacity of Dissolved Inorganic Phosphorus and corresponding Dissolved Inorganic nitrate uptake in Saccharina latissima and Laminaria digitata (Phaeophyceae)
Journal of phycology, 2019Co-Authors: Alexander Lubsch, Klaas R. TimmermansAbstract:Uptake rates of Dissolved Inorganic Phosphorus and Dissolved Inorganic nitrogen under unsaturated and saturated conditions were studied in young sporophytes of the seaweeds Saccharina latissima and Laminaria digitata (Phaeophyceae) using a "pulse-and-chase" assay under fully controlled laboratory conditions. In a subsequent second "pulse-and-chase" assay, internal storage capacity (ISC) was calculated based on V-M and the parameter for photosynthetic efficiency F-v/F-m. Sporophytes of S. latissima showed a V-S of 0.80 +/- 0.03 mu mol center dot cm(-2) center dot d(-1) and a V-M of 0.30 +/- 0.09 mu mol center dot cm(-2) center dot d(-1) for Dissolved Inorganic phosphate (DIP), whereas V-S for DIN was 11.26 +/- 0.56 mu mol center dot cm(-2) center dot d(-1) and V-M was 3.94 +/- 0.67 mu mol center dot cm(-2) center dot d(-1). In L. digitata, uptake kinetics for DIP and DIN were substantially lower: V-S for DIP did not exceed 0.38 +/- 0.03 mu mol center dot cm(-2) center dot d(-1) while V-M for DIP was 0.22 +/- 0.01 mu mol center dot cm(-2) center dot d(-1). V-S for DIN was 3.92 +/- 0.08 mu mol center dot cm(-2) center dot d(-1) and the V-M for DIN was 1.81 +/- 0.38 mu mol center dot cm(-2) center dot d(-1). Accordingly, S. latissima exhibited a larger ISC for DIP (27 mu mol center dot cm(-2)) than L. digitata (10 mu mol center dot cm(-2)), and was able to maintain high growth rates for a longer period under limiting DIP conditions. Our standardized data add to the physiological understanding of S. latissima and L. digitata, thus helping to identify potential locations for their cultivation. This could further contribute to the development and modification of applications in a bio-based economy, for example, in evaluating the potential for bioremediation in integrated multitrophic aquacultures that produce biomass simultaneously for use in the food, feed, and energy industries.
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Uptake kinetics and storage capacity of Dissolved Inorganic Phosphorus and corresponding N:P dynamics in Ulva lactuca (Chlorophyta).
Journal of phycology, 2018Co-Authors: Alexander Lubsch, Klaas R. TimmermansAbstract:Dissolved Inorganic Phosphorus (DIP) is an essential macronutrient for maintaining metabolism and growth in autotrophs. Little is known about DIP uptake kinetics and internal P-storage capacity in seaweeds, such as Ulva laduca (Chlorophyta). Ulva laduca is a promising candidate for biofiltration purposes and mass commercial cultivation. We exposed U. laduca to a wide range of DIP concentrations (1-50 mu mol center dot L-1 and a nonlimiting concentration of Dissolved Inorganic nitrogen (DIN; 5,000 mu mol center dot L-1 ) under fully controlled laboratory conditions in a "pulse-and-chase" assay over 10 d. Uptake kinetics were standardized per surface area of U. lactual fronds. Two phases of responses to DIP-pulses were measured: (i) a surge uptake (V-s) of 0.67 +/- 0.10 mu mo] center dot cm(-2) center dot d(-1) and (ii) a steady state uptake (V-M ) of 0.07 +/- 0.03 mu mol center dot cm(-2)center dot d(-1) . Mean internal storage capacity (ISCp) of 0.73 +/- 0.13 mu mol center dot cm(-2) was calculated for DIP. DIP uptake did not affect DIN uptake. Parameters of DIN uptake were also calculated: V-s = 12.54 +/- 1.90 mu mol center dot cm(-2) center dot d(-1), V-M = 2.26 +/- 0.86 mu mol center dot cm(-2) center dot d(-1) , and ISCN = 22.90 +/- 6.99 mu mol center dot cm(-2) . Combining ISC and V-M values of P and N, nutrient storage capacity of U. lactuca was estimated to be sufficient for similar to 10 d. Both P and N storage capacities were filled within 2 d when exposed to saturating nutrient concentrations, and uptake rates declined thereafter at 90% for DIP and at 80% for DIN. Our results contribute to understanding the ecological aspects of nutrient uptake kinetics in U. lactuca and quantitatively evaluating its potential for bioremediation and/or biomass production for food, feed, and energy.
Christa Pohl - One of the best experts on this subject based on the ideXlab platform.
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An estimate of the efficiency of the iron‐ and manganese‐driven Dissolved Inorganic Phosphorus trap at an oxic/euxinic water column redoxcline
Global Biogeochemical Cycles, 2010Co-Authors: Robert Turnewitsch, Christa PohlAbstract:[1] Geochemical records suggest the ocean has undergone periods of at least partial deeper-ocean anoxia or euxinia. Two counteracting feedback loops involving redox control of the dynamics of the phytoplankton nutrient Dissolved Inorganic Phosphorus (DIP) might coexist, helping to stabilize the redox state of the atmosphere and oceans. This concept implies that, during deeper-ocean anoxia, the DIP transfer from the deep anoxic into the oxic surface ocean is uninhibited by processes taking place at the redoxcline. This implicit assumption requires testing because iron (Fe) and manganese (Mn) dynamics at oxic/anoxic water column redoxclines have the potential to form a DIP trap, inhibiting DIP transport from anoxic deep into oxic surface waters. Using a time series data set of Fe, Mn, DIP, and Dissolved oxygen distributions in the Eastern Gotland Basin of the Baltic Sea, we provide estimates of the efficiency of this Fe- and Mn-driven DIP trap. This efficiency was estimated by calculating the ratios of (1) the downward flux of DIP adsorbed onto and/or coprecipitated into the settling authigenic Fe- and Mn-rich particles just above the redoxcline and (2) the upward turbulent-diffusive DIP flux across the redoxcline. Depending on the assumed particle densities, we find average ±1 SD trapping efficiencies of 0.38 ± 0.29 and 0.63 ± 0.45. The efficiencies are significant in that they seem to impact cyanobacterial dynamics in the central Baltic Sea. We discuss possible implications of the trapping mechanism for, and propose two hypotheses relating to the potential importance of Fe-controlled DIP trapping at redoxclines during, ocean anoxic events.
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an estimate of the efficiency of the iron and manganese driven Dissolved Inorganic Phosphorus trap at an oxic euxinic water column redoxcline
Global Biogeochemical Cycles, 2010Co-Authors: Robert Turnewitsch, Christa PohlAbstract:[1] Geochemical records suggest the ocean has undergone periods of at least partial deeper-ocean anoxia or euxinia. Two counteracting feedback loops involving redox control of the dynamics of the phytoplankton nutrient Dissolved Inorganic Phosphorus (DIP) might coexist, helping to stabilize the redox state of the atmosphere and oceans. This concept implies that, during deeper-ocean anoxia, the DIP transfer from the deep anoxic into the oxic surface ocean is uninhibited by processes taking place at the redoxcline. This implicit assumption requires testing because iron (Fe) and manganese (Mn) dynamics at oxic/anoxic water column redoxclines have the potential to form a DIP trap, inhibiting DIP transport from anoxic deep into oxic surface waters. Using a time series data set of Fe, Mn, DIP, and Dissolved oxygen distributions in the Eastern Gotland Basin of the Baltic Sea, we provide estimates of the efficiency of this Fe- and Mn-driven DIP trap. This efficiency was estimated by calculating the ratios of (1) the downward flux of DIP adsorbed onto and/or coprecipitated into the settling authigenic Fe- and Mn-rich particles just above the redoxcline and (2) the upward turbulent-diffusive DIP flux across the redoxcline. Depending on the assumed particle densities, we find average ±1 SD trapping efficiencies of 0.38 ± 0.29 and 0.63 ± 0.45. The efficiencies are significant in that they seem to impact cyanobacterial dynamics in the central Baltic Sea. We discuss possible implications of the trapping mechanism for, and propose two hypotheses relating to the potential importance of Fe-controlled DIP trapping at redoxclines during, ocean anoxic events.
Tim Jickells - One of the best experts on this subject based on the ideXlab platform.
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has the role of estuaries as sources or sinks of Dissolved Inorganic Phosphorus changed over time results of a kd study
Marine Pollution Bulletin, 1998Co-Authors: K Prastka, Richard Sanders, Tim JickellsAbstract:Abstract There are literature reports suggesting that some estuaries are sinks for Dissolved Inorganic Phosphorus (DIP) whilst other estuaries appear to be sources of DIP. Here a simple Kd model is presented that is able to rationalize these disparate patterns of behaviour. This model suggests that riverine DIP levels are an important regulator of DIP behaviour in estuaries. DIP concentrations have increased in many rivers over the last 50 years as a result of human activity. The model results presented suggest that increases in riverine DIP concentrations from 5 μM, consistent with documented changes in some systems over the last 50 years, can change estuaries from being sources to sinks for DIP. The model results demonstrate that suspended solid concentrations in estuaries (based on simulations over the range 100–2000 mg 1−1) are also an important regulator of DIP behaviour and hence the modification of suspended solids via dredging and land reclamation activities in estuaries can alter their DIP removal capacity.
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Has the role of estuaries as sources or sinks of Dissolved Inorganic Phosphorus changed over time ? Results of a Kd study
Marine Pollution Bulletin, 1998Co-Authors: K Prastka, Richard Sanders, Tim JickellsAbstract:Abstract There are literature reports suggesting that some estuaries are sinks for Dissolved Inorganic Phosphorus (DIP) whilst other estuaries appear to be sources of DIP. Here a simple Kd model is presented that is able to rationalize these disparate patterns of behaviour. This model suggests that riverine DIP levels are an important regulator of DIP behaviour in estuaries. DIP concentrations have increased in many rivers over the last 50 years as a result of human activity. The model results presented suggest that increases in riverine DIP concentrations from 5 μM, consistent with documented changes in some systems over the last 50 years, can change estuaries from being sources to sinks for DIP. The model results demonstrate that suspended solid concentrations in estuaries (based on simulations over the range 100–2000 mg 1−1) are also an important regulator of DIP behaviour and hence the modification of suspended solids via dredging and land reclamation activities in estuaries can alter their DIP removal capacity.
Shi-wei Chung - One of the best experts on this subject based on the ideXlab platform.
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Dissolved Inorganic Phosphorus Dissolved iron and trichodesmium in the oligotrophic south china sea
Global Biogeochemical Cycles, 2003Co-Authors: Shi-wei Chung, Liang-saw Wen, Kon Kee Liu, Yuh-ling Lee Chen, Houng Y. Ng Chen, David M. KarlAbstract:[1] Dissolved Inorganic Phosphorus (DIP) concentrations in the oligotrophic surface waters of the South China Sea decrease from ∼20 nM in March 2000 to ∼5 nM in July 2000, in response to seasonal water column stratification. These minimum DIP concentrations are one order of magnitude higher than those in the P-limited, iron-replete stratified surface waters of the western North Atlantic, suggesting that the ecosystem in the South China Sea may be limited by bioavailable nitrogen or some trace nutrient rather than DIP. Nutrient enrichment experiments using either nitrate, phosphate or both indicate that nitrogen limits the net growth of phytoplankton in the South China Sea, at least during March and July 2000. The fixed nitrogen limitation may result from the excess phosphate (N:P<16) transported into the South China Sea from the North Pacific relative to microbial population needs, or from iron control of nitrogen fixation. The iron-limited nitrogen fixation hypothesis is supported by the observation of low population densities of Trichodesmium spp. (<48 × 103 trichomes/m3), the putative N2 fixing cyanobacterium, and with low concentrations of Dissolved iron (∼0.2–0.3 nM) in the South China Sea surface water. Our results suggest that nitrogen fixation can be limited by available iron even in regions with a high rate of atmospheric dust deposition such as in the South China Sea.
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Dissolved Inorganic Phosphorus, Dissolved iron, and Trichodesmium in the oligotrophic South China Sea
Global Biogeochemical Cycles, 2003Co-Authors: Shi-wei Chung, Liang-saw Wen, Kon Kee Liu, Yuh-ling Lee Chen, Houng Y. Ng Chen, David M. KarlAbstract:[1] Dissolved Inorganic Phosphorus (DIP) concentrations in the oligotrophic surface waters of the South China Sea decrease from ∼20 nM in March 2000 to ∼5 nM in July 2000, in response to seasonal water column stratification. These minimum DIP concentrations are one order of magnitude higher than those in the P-limited, iron-replete stratified surface waters of the western North Atlantic, suggesting that the ecosystem in the South China Sea may be limited by bioavailable nitrogen or some trace nutrient rather than DIP. Nutrient enrichment experiments using either nitrate, phosphate or both indicate that nitrogen limits the net growth of phytoplankton in the South China Sea, at least during March and July 2000. The fixed nitrogen limitation may result from the excess phosphate (N:P