POGO, our vertical profiler system will return to the water this summer after a trip to Japan for repair and extensive testing. POGO will be placed approximately 10 km north of the Barkley Canyon node to provide information about continental shelf waters off the coast of Vancouver Island. The motivation for this innovative instrument platform is to provide real-time access to the water column. Studies of the water column are traditionally done from ships and, in fact, this area is monitored by two programs led by scientists in Fisheries and Oceans Canada at the Institute of Ocean Sciences: La Perouse Bank and Line P, which each intensively sample two and three per each year, respectively. These areas are the most productive parts of the coast and together Line P and La Perouse Bank provide five snapshots each year.
Although the Line P and La Perouse Bank programs gather regular and valuable data from this area, data are lacking during important transition times, particularly the change from winter to summer when phytoplankton tends to bloom. Many questions surround the phytoplankton bloom: Which variations in parameters have the greatest influences on productivity? How do El Niño and ENSO influence biology and chemistry in the ocean? POGO will provide a real-time presence that can respond to events immediately. Every day, POGO will make four trips through the water column and when an important event, such as a bloom occurs, the VPS instruments can be custom-positioned to monitor this bloom.
A team of 10 scientists across the country put this project together and selected a suite of instruments that would be broad enough to measure key physical, biological and chemical parameters. The instruments include:
- Satlantic upwelling radiometer
- Satlantic downwelling radiometer
- ASL acoustic water column profiler (a.k.a. echosounder)
- WETLabs Chl fluorometer and turbidity sensor
- WETLabs coloured dissolved organic matter sensor (CDOM)
- Pro-Oceanus CO2 sensor
- Naxys hydrophone
- Seabird SBE 19plus Conductivity-Temperature-Depth (CTD) sensor
- Nortek Aquadopp Acoustic Doppler Current Profiler (ADCP)
- Aanderaa oxygen optode
- Satlantic nitrate sensor
Serial Number 0001
There have been significant difficulties getting this first-of-a-kind platform up and running since it arrived from Japan in November 2008. As John Dower (principle investigator for the Biophysical Linkages research projectthat intends to use POGO) commented, challenges are expected given that POGO has “serial number 0001”.
After its first deployment in August 2009, the original winch motor did not last the winter. We were able to extend the instrument float upward, but we were unable to retract it. POGO had to sit on the seafloor until May 2010 when we were able to recover it. The components were then sent to the manufacturer Nichiyu Giken Kogoyo (NGK) in Japan for repair. The newly refurbished POGO was re-deployed in September 2010, but developed a ground fault on one of the connectors and so had to be recovered again. After further repairs over the winter, POGO was placed in Saanich Inlet at 80m depth for one month where it performed admirably with only a few minor, easily resolved issues to be dealt with. We planned to re-install POGO in 2011, but an unlucky incident put these plans on ice: communications to our Barkley Upper Slope platform were lost in February 2011.
NGK arrived in March 2012 to replace a few parts that had suffered some wear during the month at 80m. The NGK technicians also completed a final firmware upgrade that allows the platform to better handle depth changes, due to tides, when docking to the base. In addition, the tether between buoy and platform was replaced. One instrument port also suffered some intermittency, so the affected fluorometer was moved to a new port just to be safe. Our team is hopefully optimistic that POGO will operate as desired when it is installed during our upcoming summer cruise. During deployment, there will be extensive ship-board CTD and Rosette inter-calibrations with the instruments on the VPS. Once deployed, its readings will be compared to a small instrument package the Ocean Networks Canada Centre for Enterprise and Engagement is testing to ensure accuracy. Installing POGO during our first cruise of the season will allow us to monitor it and see how it performs; if any issues crop up, we can revisit the system and deal with them during our September cruise.
Once POGO is up and running, researchers can begin to tackle some intriguing questions about offshore oceanography. One of the major goals is to monitor the transition in coastal water from winter to summer, when phytoplankton blooms begin. Scientists hope to track this transition in detail; although there is a general understanding in the scientific community of how it happens, the time scale and variation of this transition remain unknown. Changes in temperature and salinity structure with accompanying changes in nutrients (nitrates) and light as well as stratification can all be tracked as the phytoplankton bloom begins.
Scientists also hope to answer basic questions about the bloom itself. Is there a single big bloom? Are there mini-blooms? How does the bloom kick-start? Satellite observations can help us monitor ocean surface colour, but that only lets us know a bloom is happening; POGO will allow key biological, chemical and physical variables associated with these blooms to be monitored through the depth of the water column.
When phytoplankton bloom, the zooplankton biomass tends to increase as they have more food. The response of zooplankton to the bloom can be monitored by acoustic sensors such as echosounders. The question of how rapidly the zooplankton biomass increases after the summer bloom may begin to be answered. In addition to monitoring small creatures and their environments, a hydrophone installed on POGO will providing a real-time listening post for both passing marine mammals and marine traffic.
Although POGO will only measure the water column at one spot in the ocean, what is lost in spatial resolution is gained in time resolution. The continuous data collected by POGO will provide the background for what happens in the ocean during the gaps between the intensive sampling missions of the Line P and La Perouse Bank programs. Hopefully, this will let researchers working with data from Line P and La Perouse Bank to gain further insight into the oceanographic context for samples collected through these programs. Furthermore, four daily measurements of various water properties through the depth of the water column, will help scientists gain new insights into diurnal cycle variations.