Biofouling of natural and artificial surfaces in the marine environment and possible antifouling strategies for long-term, in situ deployment

Abstract

Biofouling is a major problem for long-term deployment of sensors in marine environments. The aim of this project is to find a practical and effective strategy to prevent the biofilm formation on sensors; especially in the marine environment. This requires understanding of: 1) variability in the nature and severity of fouling as a function of the deployment location. For this purpose the planktonic and biofilm microbial community structure of the Mid-Cayman ridge were examined. 2) The effect of biofouling the material from which the surface is manufactured. 3) Efficacy of antifouling strategies that could be applied.

Experiments, deploying on a variety of artificial materials deployed for 10 days and 23 months at 4,700 m in the Cayman Trough, showed that significant biofilm formation occurred. Biofilm surface coverage was used as a biomass indicator. The results demonstrate microfouling might turn out to be a major problem for long-term deployment in this type of extreme environment and therefore the potential need for mitigation strategies for any kind of long–term deployments of remote sensors in marine environments.
Possible antifouling techniques might be surface modification. Cyclic Olefin Copolymer (COC), COC embedded with copper, copper(I) oxide, and copper(II) oxide respectively were examined. In order to test the effectives of copper and copper oxides embedded, samples were exposed to an eutrophic environment, the Solent, for 14 day. These showed a significant variance in the live cell number between all materials (p = 1.14E-8). COC embedded with copper also showed a reduction in the Total cell number and the ratio of live to total cells. For the community analysis a denaturing gradient of 30-50% and 30-80% were determined to be sufficient for the separation of eukaryotic and archaean/bacterial.
Another approach to increase the fouling resistance of materials is to change their surface characteristics. As example regarding this approach micro-/nano-structuring and plasma treatment to create hydrophobic and hyper-hydrophobic surfaces were examined in a laboratory experiment. In this study examined example significant reduction of biofilm formation at an intermediary wettability of the surface.
The electrolysis of seawater for the production of chlorine is currently used in a variety of fields e.g. on ship hull surfaces or in pipelines, but the huge power consumption prohibited the use for remote sensors until now. The examined sensor electrode with included seawater electrolysis demonstrated significant fouling reduction of over 50% on sensor electrode deployed for 20 days using an incorporated cleaning waveform.

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