Methods for Reducing Biofouling of Moored Optical Sensors

Abstract

Biofouling is one of the primary limiting factors in terms of measurement accuracy and deployment longevity for oceanographic studies involving autonomous sampling. Copper can significantly reduce marine fouling for long-term optical sensor deployments in coastal and open-ocean environments. Copper can effectively replace previously used highly toxic chemical antifoulant methods. Copper-based antifouling systems can be employed with three types of optical sensors: 1) open, 2) enclosed or semienclosed, and 3) shuttered. Copper plates on open-faced backscattering sensors can enable deployment periods of longer than 60 days in coastal waters without biofouling. In addition, copper tubing on nine-wavelength absorption-attenuation meters (ac-9s) has extended measurement capabilities from about 10 days to greater than 60 days with no signs of biofouling in coastal waters. Implementation of copper shutters on optical sensors in open-ocean waters off Japan has resulted in extended deployment periods (410 days and possibly longer) for optical measurements whereas previous optical measurements in the open ocean were typically degraded within several weeks to at most a few months due to biofouling.

Comparison of inherent optical properties as a surrogate for particulate matter concentration in coastal waters

“…We cannot rule out, however, that differences in handling (manual cleaning of the transmissometer vs. automated shutter for the turbidity sensors) could explain the observed differences. An automated method to minimize biofouling of flow-through transmissometers does exist (Manov et al 2004) but cannot be applied to transmissometers open to the environment as was done here. Measuring two optical properties improves retrieval of PM, though not by much, and only if backscattering is one of the two optical properties measured (Table 5).…”

Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health

“…Daily average data were calculated from all burst average data which passed the QA protocol. Breaks in data are due to instrumentation failure or biofouling of sensors which is a common problem in these productive regions (Manov et al, 2004). Chlorophyll fluorometers were calibrated using results from discrete samples collected and analysed as described above (n = 119, r 2 = 0.74, P > 0.01).…”

Nanocomposite thin film of Ag nanoparticles embedded in amorphous Al 2 O 3 on optical sensors windows: Synthesis, characterization and targeted application towards transparency and anti-biofouling

“…Such measures may involve incorporation of some type of brush or wiper, however it should be ensured that it will not scratch the optical surface. In this perspective, copper plates, tubing and shutters were proposed by Manov et al to delay biofouling [5]. Chlorination resulting from either bleach injection or electrolysis [6] or the use of pressurized fresh water cleaning [7] have also been reported as means of chemical cleaning of sensors' lens and housing.…”

“…In that case, the measurement medium and the sensor sensitive area must remain as much as possible unmodified. This implies that the coatings need to be transparent and to present low surface roughness to avoid erroneous measurements [2,5]. For sensors operating in marine environment, these specifications have been met through the use of conductive, catalytic coatings composed of platinum, Pt and indium tin oxide, ITO [8].…”