Sea Technology

FEB 2017

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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Page 36 of 72

36 st / February 2017 included time series of water currents, temperature, salinity, dissolved oxygen (DO), fluorescence and light intensity. Loggers for Shamal Study On January 18, 2013, an instrumented oceanographic mooring was deployed about 2 naut. mi. northeast of Qarooh Island, off the coast of Kuwait (28° 50.938 N, 048° 47.534 E). Three PME Cyclops-7 chlorophyll fluorometers sampling every 5 min. and five PME miniDOT dissolved oxygen sen- sors sampling every 1 min. were part of the sensor suite on this mooring. The Cyclops-7 logger was designed in partnership with Turner Designs, and each logger can connect to one Turner Designs Cyclops-7 sensor at a time. PME offers a fixed sen- sor version, as well as an interchangeable sensor version. The logger records measurements internally at a variety of sample rates and can collect roughly 28,000 samples before the batteries need to be replaced. Data are stored internally and downloaded to a computer via a standard USB cable. Included software allows the user to calibrate the sensor, change the sample rate and graphically view data after de- ployment. The miniDOT logger is a completely submersible instru- ment that logs dissolved oxygen and temperature measure- ments at 100 m maximum depth. The oxygen sensor is an optode that measures dissolved oxygen concentration in wa- ter through a fluorescence method. Data are recorded to an internal SD card. Operation of the miniDOT logger, such as setting the time and sample interval, can be accomplished via USB cable. Anis's analysis of the miniDOT data led to the observation that, as a result of the Shamal events, the dissolved oxygen concentration in the water column increases significantly, with elevated levels reaching down to the sea bottom at a depth of about 20 m. These elevated levels were observed to last more than two days after the event began. Low levels of oxygen, if sustained for an extended period, may eventually result in hypoxic conditions in the water col- umn. Elevated levels of oxygen resulting from strong mixing events, as has been observed to occur as a result of Shamal events, may disturb such buildup of hypoxic conditions. Analysis of available data suggests an increase in the number of Shamal events during the past 14 years. However, it is premature to conclude if this may significantly decrease development of hypoxic conditions since, at the same time, global warming is promoting stratification of the water col- umn, which is likely to decrease mixing. As for the Cyclops-7 units in this study, they yielded only a relatively short data set (approximately 10 days). Unfortu- nately, the data set from the Cyclops-7 logger was not long enough to produce any conclusions. The idea was that the Cyclops-7 loggers would collect chlorophyll data for a long enough period that may have detected elevated chlorophyll levels resulting from Shamal events. The elevated levels of chlorophyll could have resulted from an increase in nutrient fluxes from bottom sediments into the euphotic zone. Further Work Anis said he intends to continue using PME instruments in his future coastal oceanographic and lake studies. He re- ports that both the miniDOT and the Cyclops-7 loggers are reliable, simple to operate and well-designed from a human engineering point of view, including ease of maintenance, programming, deployment and downloading of data. The data are stored into relatively small files several times a day, preventing loss of data that could happen when all data are stored in a single large file. The small files can be easily con- catenated using software provided by PME. ST Kristin Elliott has been involved with Precision Measurement Engineering since she was born. She enjoys new business development, discussing strategy and managing the daily processes of the company. She also enjoys spending time with her family outdoors on their annual camping trips. Instrumented oceanographic moor- ing for the Shamal study, including PME Cyclops-7 fluorometers and PME miniDOT dissolved oxygen sensors.

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