Trapped, near‐inertial waves and enhanced chlorophyll distributions

Granata, Timothy C.; Wiggert, Jerry D.; Dickey, T. D.

doi:10.1029/95jc01665

Cited by 28 publications

(20 citation statements)

References 39 publications

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“…A strong interaction occurs at diel time scales because of diel light cycles and the prevalence of internal tides in the ocean (Kamykowski 1974;Haury et al 1983;Granata et al 1995) and diel wind forcing of internal waves in lakes. Interactions also occur at shorter time scales.…”

Section: Discussionmentioning

confidence: 99%

Internal wave effects on photosynthesis: Experiments, theory, and modeling

Evans

MacIntyre

Kling

2008

Limnology & Oceanography

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Using field experiments and mathematical models, we tested whether internal waves enhance photosynthesis as they move phytoplankton through a nonlinear light field in situations where photosynthesis is light limited. Phytoplankton circulated at depths mimicking isotherm displacement for moderate wind speeds had elevated photosynthetic rates compared to static incubations. Experiments and modeling revealed that surface light variation due to cloud cover interacts strongly with the effects of internal waves and may have positive or negative effects on photosynthesis depending on the relative phase of internal wave displacement and light variation. The combined effects of internal waves and fluctuations in surface irradiance ranged from a 15% reduction up to a 200% enhancement. The distribution (sine wave vs. Gaussian) of the vertical displacement of internal waves is also important in determining the internal wave effect on photosynthesis. Internal waves in a wide variety of aquatic systems and with hourly to weekly periods show a strong potential for internal wave-induced enhancement of photosynthesis. The realization of this enhancement is dependent on characteristics of the internal waves, of algal photosynthetic response, and of variable surface light.

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Section: Discussionmentioning

confidence: 99%

Internal wave effects on photosynthesis: Experiments, theory, and modeling

Evans

MacIntyre

Kling

2008

Limnology & Oceanography

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“…The vertical gradient in σt was used to calculate the Brunt-Väisälä buoyancy frequency (N), and the average vertical velocity profiles obtained for each station were used to calculate vertical shear. N and the vertical shear estimates were combined to derive an estimate of the vertical diffusivity across the thermocline, following the parameterization developed by Granata et al (1995). The thermocline depth was defined as the depth at which maximum stratification occurred (i.e.…”

Section: Methodsmentioning

confidence: 99%

Bacterial activity and diffusive nutrient supply in the oligotrophic Central Atlantic Ocean

Gasol

Vázquez-Domı́nguez²,

Vaqué³

et al. 2009

Aquat. Microb. Ecol.

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Growing evidence of inorganic nutrient limitation on oceanic bacteria suggests a global dependence of bacterial activity and production on rates of nutrient supply. The present study examined whether surface bacterial abundance is significantly related to water column stability, and whether bacterial activity and growth rate are related to the rate of diffusive supply of inorganic nutrients to the mixed layer in the Central Atlantic during 2 meridional cruises. The 2 cruises were run under very different oceanic conditions, with relatively low values of bacterial activity in spring 1995 and relatively higher values in fall 1995. We obtained depth-resolved data in the second cruise and found that the integrated value of bacterial production was also related to the rate of nutrient supply, while integrated particulate primary production and chlorophyll concentration were not. There was also no relationship between particulate primary production and bacterial production. The relationship between nutrient supply and integrated bacterial production was tested with data from a mesocosm experiment showing a good fit to the pattern obtained in the Atlantic. Average bacterial production was ~21% of primary production in the Central Atlantic, with values ranging between 5 and 100%, and higher values in the tropical areas. The demonstration of a direct relationship between nutrient supply and bacterial activity helps to explain a relatively large bacterial biomass as compared to phytoplankton biomass, a low bacterial growth efficiency, and a high bacterial carbon demand relative to contemporaneous primary production often measured in the open ocean, as well as the accumulation of dissolved organic carbon (DOC) observed in nutrient-limited oligotrophic seas.

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“…Buoyancy frequencies were depth averaged to intervals corresponding to those used in the calculation of vertical shear, and both estimates were combined to derive an estimate of the vertical diffusivity across the thermocline (following Granata et al [1995] after Gregg [1989]):…”

Section: ϫmentioning

confidence: 99%

Nitrate uptake and diffusive nitrate supply in the Central Atlantic

Planas

Agustı́

Duarte

et al. 1999

Limnology & Oceanography

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The latitudinal variation (35ЊS to 28ЊN) in the rate of diffusive nitrate supply across the thermocline and the associated variation in the uptake rate of nitrate and ammonium in the Central Atlantic was studied. The calculated diffusive nitrate flux showed a sharp latitudinal gradient, with the lowest nitrate supply (0.00037 mol m Ϫ3 d Ϫ1 ) in the South Atlantic subtropical gyre and the highest values (23.5 mol m Ϫ3 d Ϫ1 ) between the Equator and 15ЊN. The uptake rate of nitrate was inhibited at high irradiance at most stations. Both nitrate and ammonium uptake rates were lowest (about 3 and 10 mol m Ϫ3 d Ϫ1 , respectively) at the southern end of the transect and increased (about 20 and 55 mol m Ϫ3 d Ϫ1 , respectively) towards the Equator, with this increase being much greater for ammonium than for nitrate uptake. The f-ratio was highest (ഠ0.4) just south of the Equator and lowest (ഠ0.03) at the southern end of the transect. The slope between total uptake rate of dissolved inorganic nitrogen and gross primary production, calculated from O 2 -based measurements, in surface waters (4.72 Ϯ 1.54) was somewhat lower, but not significantly so, than the expected C/N ratio of 6.6. The average uptake rate of nitrate did not differ significantly from the average estimated diffusive supply of nitrate to the biogenic layer over the Central Atlantic. However, the nitrate uptake rate increased as the ⅓ power of the diffusive nitrate flux to the biogenic layer. As a result, nitrate uptake far exceeded (by up to 100-fold) the nitrate flux to the biogenic layer in the stations where the supply of nitrate was lowest. The excess nitrate uptake averaged 0.65 Ϯ 0.24 mmol NO 3 m Ϫ2 d Ϫ1 (range, 0.05-1.9 mmol NO 3 m Ϫ2 d Ϫ1 ), which must be supplied through atmospheric deposition and other perturbation events. This excess nitrate uptake is relatively large compared to the diffusive supply in the most unproductive areas, where external nitrate inputs fuel the new production. In contrast, these sources of nitrate are far less significant where high diffusive fluxes suffice to maintain high nitrate uptake rates.

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Trapped, near‐inertial waves and enhanced chlorophyll distributions

Cited by 28 publications

References 39 publications

Internal wave effects on photosynthesis: Experiments, theory, and modeling

Internal wave effects on photosynthesis: Experiments, theory, and modeling

Bacterial activity and diffusive nutrient supply in the oligotrophic Central Atlantic Ocean

Nitrate uptake and diffusive nitrate supply in the Central Atlantic

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