SIBER SPIS sept 2011.pdf - IMBER

SIBER
Science Plan and Implementation Strategy
It is also entirely feasible and highly desirable to deploy oxygen sensors on the RAMA
moorings. Installing a Sea-Bird (SBE) 16 (or 19) sensor on the mooring bridle would provide
ports for several additional sensors, such as chlorophyll, turbidity and dissolved oxygen. In
addition, the software for the CO 2 instrument mentioned above has recently been upgraded
to make it compatible with the SBE 16 (or 19) system, i.e. it can be plugged in and all the data
(including chlorophyll, turbidity and dissolved oxygen) can be transmitted back in real-time with
the CO 2 data. This would provide an excellent option for powering, data logging and real-time
data transmission, and would probably reduce the cost of the WETLabs Inc. fluorescence/
backscatter sensors discussed above, to about $7,000 USD per unit. The total cost of an SBE-
16 including fluorescence, backscatter and oxygen is $20,000 USD.
Deploying this suite of sensors would provide a powerful set of highly complementary
biogeochemical measurements (chlorophyll, particulate organic carbon, O 2 , and CO 2 ) with
physical data for context. The estimated overall cost of this sensor package is $60,000 USD,
plus $10,000 USD for buoy modifications and mounting hardware.
To fully constrain the carbon systems and assess ocean acidification, ocean pH could also
be measured on the moorings with a SAMI-pH system (Sunburst Sensors; http://www.
sunburstsensors.com/). The SAMI-pH can also be plugged directly into the MAPCO 2 system
so the data can be transmitted back to the lab in near real-time. The approximate cost of these
systems is $20,000 USD.
Another biogeochemical sensor that should be considered is one that can be deployed to
measure nutrients, like a Satlantic NO 3 sensor. These are, however, relatively expensive,
costing ~$30,000 - $40,000 USD each, and may not be suitable for long-term deployments.
In terms of sensor priority, CO 2 and pH are the highest, given their relevance to the global
carbon cycle. The next would be fluorescence and backscatter. It would be very beneficial to
have oxygen for comparison with CO 2 and the biological measurements. The ranking for the
full suite of measurements/sensors from highest to lowest priority is CO 2 /pH, fluorescence/
backscatter, O 2 and then NO 3 . NO 3 is ranked lowest due to the high cost and the absence of
a track record of long-term deployments of these instruments in the open ocean.
Lon g e v i t y of in s t r u m e n t s
Fouling will probably compromise the data of the fluorescence/backscatter instrument first.
Good data have been logged off the Oregon coast for four months where fouling is fairly
intense (Pete Strutton, personal communication). In low-to-moderate productivity regions of
the IO, six-month deployments should be feasible, perhaps more (this estimate is based on
successful deployments in the equatorial Pacific which experiences comparable productivity
and hence fouling). It is therefore, essential to consider the mooring servicing schedule to
determine the feasibility of deploying biogeochemical sensors on the RAMA moorings. The
current RAMA service schedule is one year and it is unlikely, in most cases, that this could
be reduced to six months on a regular basis. The CO 2 systems should last for a year; but
there may be some degradation in the fluorescence and backscatter data towards the end of
deployments.
Imp l e m e n t a t i o n, s e r v i c i n g an d pr o g r a m du r a t i o n
Given the previous discussion, initial surface and subsurface deployments of CO 2 and optics,
plus pH at the surface only, are recommended at an approximate instrument cost of $128,000
USD per system (s e e Ta b l e 1). A different CO 2 sensor (SAMI-CO 2 ) would be used for the
subsurface location since the MAPCO 2 can only be used at the surface. The subsurface
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