scholarly journals Shining Light on Photosynthesis in the Harmful Dinoflagellate Karenia mikimotoi–Responses to Short-Term Changes in Temperature, Nitrogen Form, and Availability

Phycology ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 30-44
Author(s):  
So Hyun (Sophia) Ahn ◽  
Patricia M. Glibert

Karenia mikimotoi is a toxic bloom-forming dinoflagellate that sometimes co-blooms with Karenia brevis in the Gulf of Mexico, especially on the West Florida Shelf where strong vertical temperature gradients and rapid changes in nitrogen (N) can be found. Here, the short-term interactions of temperature, N form, and availability on photosynthesis–irradiance responses were examined using rapid light curves and PAM fluorometry in order to understand their interactions, and how they may affect photosynthetic yields. Cultures of K. mikimotoi were enriched with either nitrate (NO3−), ammonium (NH4+), or urea with varying amounts (1, 5, 10, 20, 50 µM-N) and then incubated at temperatures of 15, 20, 25, 30 °C for 1 h. At 15–25 °C, fluorescence parameters (Fv/Fm, rETR) when averaged for all N treatments were comparable. Within a given light intensity, increasing all forms of N concentrations generally led to higher photosynthetic yields. Cells appeared to dynamically balance the “push” due to photon flux pressure and reductant generation, with consumption in overall metabolism (“pull” due to demand). However, at 30 °C, all fluorescence parameters declined precipitously, but differential responses were observed depending on N form. Cells enriched with urea at 30 °C showed a smaller decline in fluorescence parameters than cells treated with NO3− or NH4+, implying that urea might induce a photoprotective mechanism by increasing metabolic “pull”.

Data Series ◽  
2009 ◽  
Author(s):  
Lisa L. Robbins ◽  
Paul O. Knorr ◽  
Xuewu Liu ◽  
Robert H. Byrne ◽  
Ellen A. Raabe

Data Series ◽  
10.3133/ds711 ◽  
2014 ◽  
Author(s):  
Lisa L. Robbins ◽  
Paul O. Knorr ◽  
Kendra L. Daly ◽  
Carl A. Taylor

2007 ◽  
Vol 24 (3) ◽  
pp. 484-503 ◽  
Author(s):  
Lynn K. Shay ◽  
Jorge Martinez-Pedraja ◽  
Thomas M. Cook ◽  
Brian K. Haus ◽  
Robert H. Weisberg

Abstract A dual-station high-frequency Wellen Radar (WERA), transmitting at 16.045 MHz, was deployed along the west Florida shelf in phased array mode during the summer of 2003. A 33-day, continuous time series of radial and vector surface current fields was acquired starting on 23 August ending 25 September 2003. Over a 30-min sample interval, WERA mapped coastal ocean currents over an ≈40 km × 80 km footprint with a 1.2-km horizontal resolution. A total of 1628 snapshots of the vector surface currents was acquired, with only 70 samples (4.3%) missing from the vector time series. Comparisons to subsurface measurements from two moored acoustic Doppler current profilers revealed RMS differences of 1 to 5 cm s−1 for both radial and Cartesian current components. Regression analyses indicated slopes close to unity with small biases between surface and subsurface measurements at 4-m depth in the east–west (u) and north–south (υ) components, respectively. Vector correlation coefficients were 0.9 with complex phases of −3° and 5° at EC4 (20-m isobath) and NA2 (25-m isobath) moorings, respectively. Complex surface circulation patterns were observed that included tidal and wind-driven currents over the west Florida shelf. Tidal current amplitudes were 4 to 5 cm s−1 for the diurnal and semidiurnal constituents. Vertical structure of these tidal currents indicated that the semidiurnal components were predominantly barotropic whereas diurnal tidal currents had more of a baroclinic component. Tidal currents were removed from the observed current time series and were compared to the 10-m adjusted winds at a surface mooring. Based on these time series comparisons, regression slopes were 0.02 to 0.03 in the east–west and north–south directions, respectively. During Tropical Storm Henri’s passage on 5 September 2003, cyclonically rotating surface winds forced surface velocities of more than 35 cm s−1 as Henri made landfall north of Tampa Bay, Florida. These results suggest that the WERA measured the surface velocity well under weak to tropical storm wind conditions.


1978 ◽  
Vol 10 (7) ◽  
pp. 853-866 ◽  
Author(s):  
G Hyman ◽  
D J Palmer

This paper presents the results of a time-series analysis of short-term changes in the conditions prevailing in regional labour markets. A set of alternative indicators of changes in these conditions are evaluated for each of the standard regions by use of quarterly data for a period that includes the rapid changes in the economy associated with the ‘Barber Boom’. Leading indicators of changes in labour demand are contrasted with lagging indicators and the findings for different regions compared. The results of the analysis show that in general the numbers of vacant jobs and the rates at which the jobs are being filled provide leading indicators of changes in the region's level of unemployment and of changes in the duration of unemployment in the region, and that there is no feedback from unemployment to change the demand for labour in the region. In consequence it would be justified to claim that changes in regional unemployment and its duration are caused by changes in the demand for labour in the region.


1999 ◽  
Vol 26 (15) ◽  
pp. 2239-2242 ◽  
Author(s):  
Robert D. Hetland ◽  
Ya Hsueh ◽  
Robert R. Leben ◽  
Pearn P. Niiler

2021 ◽  
Author(s):  
Nektaria Ntaganou ◽  
Vassiliki Kourafalou ◽  
Matthieu Le Hénaff ◽  
Yannis Androulidakis

2018 ◽  
Vol 52 (3) ◽  
pp. 43-50 ◽  
Author(s):  
Yonggang Liu ◽  
Robert H. Weisberg ◽  
Jason Law ◽  
Boyin Huang

AbstractSatellite-derived daily sea surface temperature (SST) products are compared with moored SST observations on the West Florida Shelf during the time period of Hurricane Irma. Most of the SST products compare reasonably well with the moored data at the location of 25-m depth, where SST dropped by about 1°C after the hurricane passage. However, most of the SST products did not show the rapid SST drop at the location of 50-m depth where the surface water was cooled by about 4°C within 1 day in response to the hurricane passage. This finding has important implications to air-sea interaction studies and hurricane simulations, in which SST data play an important role. The limitations of the popular satellite products call for additional coastal ocean observations as well as proper inclusion of the real-time observations in satellite-derived products.


2015 ◽  
Vol 12 (10) ◽  
pp. 2080-2084 ◽  
Author(s):  
Ruhul Amin ◽  
Bradley Penta ◽  
Sergio deRada

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