in the benthic boundary layer? 5) What is the quantitative significance of cross-shelf and 

 along- shelf transport of pigments? 



SPATIAL AND TEMPORAL SAMPLING SCALES 



The use of fiber optic sensors provides for great flexibility in the spatial scales that can 

 be sampled with a single instrument, ranging from centimeters to 10's of meters. The instrument 

 is currently configured for sampling eight depths at intervals within a range of 5 m above the 

 bottom. Horizontal sampling scales will be limited by the number of instruments and the number 

 of platforms which can accommodate them (see below). 



The instrument is capable of high sampling rates (up to 1 Hz), although lower sampling 

 rates will extend battery life during deployments. With current battery design and power 

 requirements, we estimate a nominal 1200 h (50 d) of operation with sampling rates of 10 min 

 per h. 



METHODS AND PLATFORMS 



The autonomous instrument is capable of measuring and storing fluorescence data at eight 

 different depths. The present system is contained within an 18 cm diameter, 1 m long aluminum 

 casing with 16 fiber optic feedthroughs at one end. Autonomous operation and data logging are 

 achieved using a Tattletale 7 (TT7) with a 120 Mbyte hard drive and interface board on which 

 additional logic has been constructed. The TT7 is interfaced with the Ocean Optics 

 PC1000-ADC board (500 kHz/12 bit). Excitation light is provided by 4 strobe units (EG&G). 

 The light is filtered using a Schott BG-28 blue transmission filters. Strobe intensity is monitored 

 with separate fibers going to a phototransistor. Detection of fluorescence is achieved with two 

 Hamamatsu photomultiplier tubes equipped with 676 nm narrow bandpass filters (Edmund A43, 

 140, 1 in diam.). 



The multi-sensor fluorometer will be deployed on the eastern U.S. continental shelf north 

 of Cape Hatteras near the Duck site for a 4-6 week period in July- August 1994 in conjunction 

 with the CoOP Pilot study. Our instrument will be mounted on the BASS bottom tripod system 

 of Williams and Churchill. The BASS tripod system provides an ideal platform for deployment 

 of the fiber optic fluorometer array. Variations in fluorescence can be interpreted in the context 

 of data collected with other BASS sensors including thermistors, CTD, acoustic travel time 

 current meters, optical backscatterance (OBS) sensors and laser diffraction particle size 

 measurements. This will permit an assessment of the extent that resuspension and lateral flows 

 result in transport of pigments associated with the benthic boundary layer. Ideally, calibration 

 of OBS and fluorescence measurements to particulate organic carbon can be made using 

 simultaneous measures of organic matter from time-series samplers. 



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