Long term deployments of oceanographic instrumentation are vulnerable to the harsh conditions of the ocean. For optical instruments the build up of organic matter via growth of marine organisms (i.e. biofouling) on the optical sensing faces can significantly reduce the quality of the measurements. Biofouling is now the limiting factor for long term biogeochemical data sets as recent technological improvements have increased instrument deployment lifetime. The ECO line of instruments from WET Labs are designed for long term deployment capabilities with low power requirements, a large memory and an available bio-wiper™. The bio-wiper™ on the ECO was designed to protect the optical surface and has been very effective under most conditions. Long term deployments on the Gulf of Maine Ocean Observing System (GoMOOS) and the MOSEAN mooring in the Santa Barbara Channel of up to 6 months and longer have been observed with little to no effect on the baseline signal (Figure 1).
Figure 1. Six month deployment of a ECO DFLS chlorophyll
fluorometer at 3 m depth on a Gulf of Maine Ocean Observing System
mooring in the Gulf of Maine. The baseline value of chlorophyll varies
with time but does not increase with time as is typically observed
when biofouling compromises the data. Figure courtesy of Dr. Collin Roesler, Bigelow
Laboratory for Ocean Science and the Gulf of Maine Ocean Observing System.
Occasionally, in areas of rapid biofouling, the bio-wiper™ (right) mechanism has been less than fully effective due to fouling on surfaces
of the ECO instrument not protected by the bio-wiper™. To
prevent marine organisms from attaching to the instrument body near the
optical head and interfering with the operation of the bio-wiper™ we
suggest using copper foil tape. The GoMOOS project developed this technique
for their ECO sensors (Figures 2 and 3) and WET Labs recommends this technique.
This technique does not violate the ECO warranty and WET Labs will service
instruments that have had copper tape applied to them.
Figure
2. Electrical tape applied under area where copper tape will be applied.
This protects the meter from the significant adhesive residue of the
copper foil tape.
Figure 3. Copper tape applied. The above
example is 3-in. wide tape with non-conductive adhesive, available
from McMaster-Carr. Note that when applying the tape the adhesive should
not be touched; it will not stick to the electrical tape on the meter.
When submerged in salt water, the copper will adhere more closely to the
meter.
