The role of air-sea exchange in the marine nitrogen cycle

Jickells, Tim

doi:10.5194/bg-3-271-2006

Cited by 50 publications

(27 citation statements)

References 61 publications

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“…It may surpass N 2 -fixation as the primary source of bioactive N for the world’s oceans in the next 50 years [24]. In contrast, atmospheric deposition of P is relatively small [82], [83].…”

Section: Discussionmentioning

confidence: 99%

Increased Toxicity of Karenia brevis during Phosphate Limited Growth: Ecological and Evolutionary Implications

et al. 2013

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Karenia brevis is the dominant toxic red tide algal species in the Gulf of Mexico. It produces potent neurotoxins (brevetoxins [PbTxs]), which negatively impact human and animal health, local economies, and ecosystem function. Field measurements have shown that cellular brevetoxin contents vary from 1–68 pg/cell but the source of this variability is uncertain. Increases in cellular toxicity caused by nutrient-limitation and inter-strain differences have been observed in many algal species. This study examined the effect of P-limitation of growth rate on cellular toxin concentrations in five Karenia brevis strains from different geographic locations. Phosphorous was selected because of evidence for regional P-limitation of algal growth in the Gulf of Mexico. Depending on the isolate, P-limited cells had 2.3- to 7.3-fold higher PbTx per cell than P-replete cells. The percent of cellular carbon associated with brevetoxins (%C-PbTx) was ∼ 0.7 to 2.1% in P-replete cells, but increased to 1.6–5% under P-limitation. Because PbTxs are potent anti-grazing compounds, this increased investment in PbTxs should enhance cellular survival during periods of nutrient-limited growth. The %C-PbTx was inversely related to the specific growth rate in both the nutrient-replete and P-limited cultures of all strains. This inverse relationship is consistent with an evolutionary tradeoff between carbon investment in PbTxs and other grazing defenses, and C investment in growth and reproduction. In aquatic environments where nutrient supply and grazing pressure often vary on different temporal and spatial scales, this tradeoff would be selectively advantageous as it would result in increased net population growth rates. The variation in PbTx/cell values observed in this study can account for the range of values observed in the field, including the highest values, which are not observed under N-limitation. These results suggest P-limitation is an important factor regulating cellular toxicity and adverse impacts during at least some K. brevis blooms.

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Section: Discussionmentioning

confidence: 99%

Increased Toxicity of Karenia brevis during Phosphate Limited Growth: Ecological and Evolutionary Implications

et al. 2013

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“…The relative importance of wet and dry deposition obviously varies greatly on short time scales since rainfall is episodic and varies spatially on longer time scales with global rainfall patterns (Jickells 2006). We estimated mean total (dry+wet) deposition fluxes of atmospheric TIN in the Pacific Ocean from 48°N and 55°S to be 32-64 μmol m −2 d −1 , with 66-99% of this in the form of wet deposition.…”

Section: Dry and Wet Deposition Fluxes Of Atmospheric Inorganic Nitromentioning

confidence: 99%

Atmospheric inorganic nitrogen in marine aerosol and precipitation and its deposition to the North and South Pacific Oceans

2011

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Aerosol and rain samples were collected between 48°N and 55°S during the KH-08-2 and MR08-06 cruises conducted over the North and South Pacific Ocean in 2008 and, to estimate dry and wet deposition fluxes of atmospheric inorganic nitrogen (N). Inorganic N in aerosols was composed of~68% NH 4 + and~32% NO 3 -(median values for all data), with~81% and~45% of each species being present on fine mode aerosol, respectively. Concentrations of NH 4 + and NO 3 − in rainwater ranged from 1.7-55 μmol L −1 and 0.16-18 μmol L −1 , respectively, accounting for~87% by NH 4 + and~13% by NO 3 − of total inorganic N (median values for all data). A significant correlation (r00.74, p<0.05, n010) between NH 4 + and methanesulfonic acid (MSA) was found in rainwater samples collected over the South Pacific, whereas no significant correlations were found between NH 4 + and MSA in rainwater collected over the subarctic (r0 0.42, p>0.1, n06) and subtropical (r00.33, p>0.5, n06) western North Pacific, suggesting that emissions of ammonia (NH 3 ) by marine biological activity from the ocean could become a significant source of NH 4 + over the South Pacific. While NO 3 − was the dominant inorganic N species in dry deposition, inorganic N supplied to surface waters by wet deposition was predominantly by NH 4 + (42-99% of the wet deposition fluxes for total inorganic N). We estimated mean total (dry+wet) deposition fluxes of atmospheric total inorganic N in the Pacific Ocean to be 32-64 μmol m −2 d −1 , with 66-99% of this by wet deposition, indicating that wet deposition plays a more important role in the supply of atmospheric inorganic N than dry deposition.

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“…Recent research has provided much support for these hypotheses, with recent estimates that the cooling effect due to DMS may be up to 40% of the anthropogenic greenhouse forcing in polar regions (Gabric et al 2003). Similarly, a recent review by Jickells (2006) stresses the importance of iron in terrestrial dust in climate studies.…”

Section: Possible Climate Regulating Mechanismsmentioning

confidence: 93%

The peatland/ice age hypothesis revised, adding a possible glacial pulse trigger

Franzén

Cropp

2007

Geografiska Annaler: Series A, Physical Geography

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Carbon sequestering in peatlands is believed to be a major climate‐regulating mechanism throughout the late Phanerozoic. Since plant life first evolved on land, peatlands have been significant carbon sinks, which could explain significant parts of the large variations in atmospheric carbon dioxide observed in various records. The result is peat in different degrees of metamorphosis, i.e. lignite, hard coal and graphite. During phases of extensive glaciations such as the 330–240 Ma Pangea Ice Age, atmospheric carbon dioxide was critically low. This pattern repeats itself during the Pleistocene when carbon dioxide oscillates with an amplitude of c. 200–300 ppmv. This paper suggests that the ice age cycles during the Pleistocene are generated by the interglacial growth of peatlands and the subsequent sequestering of carbon into this terrestrial pool. The final initiation of ice age pulses towards the end of inter‐glacials, on the other hand, is attributed to the cyclic influx of cosmic dust to the Earth surface, which in turn regulates cloud formation and the incoming shortwave radiation. These shorter cycles have a frequency of c. 1000‐1250 years and might be connected to sunspot or other low frequency solar variations. In a wider context the ice age cycling could be regarded as an interplay between terrestrial life on the high latitudes of the northern hemisphere and the marine subsurface life in the southeast. If the results presented here are correct, the present global warming might just be the early part of a new warm period such as the Bronze Age and the Roman and Medieval Warm periods. This could be caused by entry into another phase of decreasing influx rates of cosmic dust. The increasing concentrations of atmospheric carbon dioxide might have contributed to this warming but, most important of all, it might temporarily have saved us from a new ice age pulse.

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The role of air-sea exchange in the marine nitrogen cycle

Cited by 50 publications

References 61 publications

Increased Toxicity of Karenia brevis during Phosphate Limited Growth: Ecological and Evolutionary Implications

Increased Toxicity of Karenia brevis during Phosphate Limited Growth: Ecological and Evolutionary Implications

Atmospheric inorganic nitrogen in marine aerosol and precipitation and its deposition to the North and South Pacific Oceans

The peatland/ice age hypothesis revised, adding a possible glacial pulse trigger

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