An advanced laser-based fluorescence microstructure profiler (TurboMAP-L) for measuring bio-physical coupling in aquatic systems

An 11-d quasi-Lagrangian surface layer experiment to the east of Norfolk Island tracked a 140-m-deep drifting vertical array (DVA) of instruments, including conductivity sensors, thermistors, and current meters. These are the first in situ data from the area to measure large-amplitude internal waves. The observations show isotherm peak-to-peak excursions reaching 50 m and were dominated by the semidiurnal forcing frequency. The DVA exhibited horizontal loops at the semidiurnal tidal frequency as it tracked water at depths of 80-140 m to within 10% of total horizontal displacement. The large vertical isotherm excursions generated substantial vertical shear. Temperature microstructure estimates of the vertical diffusivity of scalar properties at 70-m depth, around the center of the thermocline, were on the order of 10 24 m 2 s 21 and around an order of magnitude larger at shallower depths. When combined with nitrate data, this implies vertical fluxes of nitrate in the pycnocline of , 1 mmol m 22 d 21 . The internal waves also potentially cause an interaction between the variability in tidal forcing and the diurnal radiation cycle that influences chlorophyll in the deep chlorophyll maximum. The average effect of the internal wave was to increase the light level for a particular isotherm over the static case. The internal waveinduced velocities were strong enough to dominate phytoplankton rise speeds and so potentially played a role in the formation and persistence of an observed Trichodesmium bloom.

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“…9). Thus, rapid changes in fluorescence can exist and are related to stratification (Doubell et al 2009). …”

Section: Resultsmentioning

confidence: 99%

Internal waves downstream of Norfolk Ridge, western Pacific, and their biophysical implications

Stevens

Sutton

Law

2012

Limnology & Oceanography

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“…The TurboMAP-L (Doubell et al 2009) is a fastresponse conductivity, temperature, vertical shear and fluorescence probe capable of measuring at subcentimetre scales. This is a free-falling instrument with typical profiling speeds between 0.5 and 0.8 m s -1 and a sampling rate of 512 Hz.…”

Section: Methodsmentioning

confidence: 99%

“…In recent years, a commercially available turbulence microprobe (TurboMAP, Wolk et al 2002) has led to an increasing number of field studies on turbulence and planktonic distributions (e.g. Yamazaki et al 2006, Doubell et al 2009, Prairie et al 2011. Most of these studies have focused on the sub-centimetre (microscale) structure of the turbulent field (Wolk et al 2002, Yamazaki et al 2006) and the associated biological signatures (Doubell et al 2009); only two studies have examined the macroscopic (>1 metre) patterns that emerge from microscale interactions (Yamazaki et al 2010, Prairie et al 2011.…”

Section: Introductionmentioning

confidence: 99%

Turbulence as a driver for vertical plankton distribution in the subsurface upper ocean

Macías¹,

Rodríguez-Santana²,

Ramirez-Romero³

et al. 2013

Sci. Mar.

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SUMMARY: Vertical distributions of turbulent energy dissipation rates and fluorescence were measured simultaneously with a high-resolution micro-profiler in four different oceanographic regions, from temperate to polar and from coastal to open waters settings. High fluorescence values, forming a deep chlorophyll maximum (DCM), were often located in weakly stratified portions of the upper water column, just below layers with maximum levels of turbulent energy dissipation rate. In the vicinity of the DCM, a significant negative relationship between fluorescence and turbulent energy dissipation rate was found. We discuss the mechanisms that may explain the observed patterns of planktonic biomass distribution within the ocean mixed layer, including a vertically variable diffusion coefficient and the alteration of the cells' sinking velocity by turbulent motion. These findings provide further insight into the processes controlling the vertical distribution of the pelagic community and position of the DCM.Keywords: turbulence, deep chlorophyll maximum, vertical plankton distribution. RESUMEN: La turbulencia como mecanismo forzante de la distribución vertical del plancton en el océano subsuperficial. -Las distribuciones verticales de la tasa de disipación de la energía turbulenta y de la fluorescencia han sido medidas simultáneamente usando un microperfilador de alta resolución en cuatro regiones oceánicas distintas, desde zonas templadas a polares y desde regiones costeras al océano abierto. Valores altos de fluorescencia, conformando un máximo profundo de clorofila (MPC) fueron detectados habitualmente en regiones poco estratificadas de la columna de agua y justo por debajo de capas con valores máximos de la tasa de disipación de la energía turbulenta. En las cercanías del MPC se encontró una relación estadísticamente significativa y negativa entre los valores de fluorescencia y energía turbulenta. En este trabajo se discuten los posibles mecanismos que pueden explicar estas relaciones, incluyendo el efecto de la variación vertical del coeficiente de difusión y la posible alteración de la velocidad de sedimentación de las células de fitoplancton por el movimiento turbulento. Estos resultados proporcionan un mayor conocimiento sobre los procesos que controlan la distribución vertical de la comunidad pelágica y la posición de los MPC.Palabras clave: turbulencia, máximo profundo de clorofila, distribución vertical del plancton.

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“…The TurboMAP‐L and FIDO‐Φ were deployed approximately 100 m apart; since both instruments were subject to horizontal drift as they descended, the horizontal displacement between the two sets of measurements was likely much greater. The TurboMAP‐L carried sensors for turbulent shear and temperature gradient, in addition to biological and turbidity microstructure (Doubell et al 2009; Yamazaki et al 2009). Sample rates ranged between 64 and 512 Hz for different parameters, and typical profiling speeds were between 0.50 and 0.80 m s − 1 .…”

Section: Methodsmentioning

confidence: 99%

Physical and biological controls of vertical gradients in phytoplankton

Prairie

Franks

Jaffe

et al. 2011

Limn Fluids and Environments

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Lay Abstract As the base of the food web, phytoplankton perform vital functions in the ocean by fixing carbon through photosynthesis and by acting as prey for other organisms. Recently, scientists have observed layers of increased phytoplankton concentration in the ocean as thin as a meter or less. These findings have suggested that phytoplankton are rarely homogeneously distributed with depth, which has significant implications for predator foraging and the formation of marine snow—particles that are important to downward carbon flux. In this study, we have developed a mathematical model that describes the biological and physical mechanisms that allow these phytoplankton layers to form and persist. Our results suggest that the steepness of a phytoplankton layer is controlled by a balance of ocean mixing and the process that allowed the layer to form, such as phytoplankton growth or swimming. We then compare our model results to data of ocean mixing and phytoplankton distributions that were obtained from a free‐falling phytoplankton imaging system on a cruise in 2006.The comparison of the data to our model shows a strong fit and allows us to estimate the rate at which observed phytoplankton layers were formed. This project thus combined biological and physical measurements in the ocean with mathematical theory to provide an understanding of the mechanisms leading to phytoplankton layer formation and persistence in the ocean. This new understanding will allow us to better predict the occurrence of these features and quantify their importance to the functioning of the marine ecosystem.

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An advanced laser-based fluorescence microstructure profiler (TurboMAP-L) for measuring bio-physical coupling in aquatic systems

Cited by 42 publications

References 28 publications

Internal waves downstream of Norfolk Ridge, western Pacific, and their biophysical implications

Internal waves downstream of Norfolk Ridge, western Pacific, and their biophysical implications

Turbulence as a driver for vertical plankton distribution in the subsurface upper ocean

Physical and biological controls of vertical gradients in phytoplankton

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