Long term ultraviolet treatment for macrofouling control in Northern and Southern hemispheres

Biofouling of marine structures must be controlled if crippling operational and maintenance costs are to be avoided and biological invasions prevented. However, traditional methods of biofouling control typically involve the use of toxic chemicals, which have their own drawbacks, both financial and environmental. For ships, the hull is the largest surface requiring a fouling-control coating, however there are other so-called ‘niche’ areas (up to 10% of total wetted area) that typically cannot be, or are not routinely, treated to prevent biofouling accumulation. The use of UV light is a tried and tested sterilization method that has been shown to also work underwater. However, the speed with which UV can be applied to large-scale biofouling control will be determined by the engineering challenges involved and the lack of basic understanding around the biological mode of action. The former is essential for effective translation of this established technology into a high-performance, industrially useful, fouling-control system. The latter will be important for environmental regulation and safe use as well as performance optimisation. Here, we developed two bespoke flow-through systems to replicate ship niche areas and deployed them in Melbourne, Australia, and North East England. We demonstrated a 40-90% reduction in biofouling coverage on silicone tiles embedded with UV-emitting LEDs, even as the LED output waned (after ~8000 hours). Image analysis and amplicon sequencing of 18S genes provided complementary information about the taxonomic composition of the fouling communities and highlighted some taxa, for example ascidians and diatoms, which may have, or in future develop, UV resistance. Interestingly, the UV treatment far exceeded performance estimates based upon the predicted attenuation distance of UV in seawater. Overall, while it is clear that UV treatment works in terms of its efficacy against the vast majority of observed fouling species, technical challenges remain, as do knowledge gaps surrounding the biological and ecological effects of widespread use.

若欲避免因生物污损而导致的运营与维护成本激增及生物入侵的预防，海洋结构物的生物污损控制势在必行。然而，传统的生物污损控制方法通常涉及有毒化学物质的使用，此类方法不仅存在财务上的弊端，亦对环境造成不利影响。对于船舶而言，船体是需涂覆防污层的最大表面积，然而，其他所谓的“特殊区域”（占总表面积的10%左右）通常无法或未常规地进行处理以防止生物污损的积累。紫外线照射作为一种经过验证的消毒方法，已被证实适用于水下环境。然而，紫外线在大规模生物污损控制中的应用速度将由工程挑战以及对于生物作用机制基本理解的不足所决定。前者对于将这一成熟技术有效转化为高性能、工业适用的防污系统至关重要。后者对于环境法规的制定、安全使用以及性能优化亦至关重要。在本研究中，我们开发了两套定制的流过式系统以复制船舶特殊区域，并将它们部署在澳大利亚墨尔本和英国东北部。我们展示了在嵌入紫外线发射LED的硅片上，生物污损覆盖率降低了40-90%，即便LED输出衰减（约8000小时后）。通过图像分析和18S基因扩增子测序，我们获得了关于污损群落分类组成的有益补充信息，并突显了一些可能具有或未来可能发展出紫外线抗性的类群，例如海鞘和硅藻。有趣的是，紫外线处理的效果远超基于海水中对紫外线预测衰减距离的预期。总体而言，尽管紫外线处理在对抗绝大多数观察到的污损物种方面显示出其有效性，但技术挑战依然存在，关于广泛使用紫外线处理的生物学和生态效应的知识空白亦需填补。