Falling foul of marine organisms

Biofouling - the settlement and growth of organisms on submerged structures - poses a major concern to industries working in the marine environment. The hydrodynamic and mechanical consequences on marine energy converters are a particular worry as they may decrease efficiency of energy generation, and accelerate corrosion of marine metals affecting the survivability of the technology.

"Biofouling is a ubiquitous problem for any industry putting structures or vessels into the marine environment, however there are specific issues regarding biofouling for the marine renewable energy industry," explains Joanne Porter, Associate Professor of Marine Biology at the International Centre of Island Technology (ICIT) in Scotland.

What is Biofouling?

Biofouling is divided into microfouling -- the formation of a 'biofilm' with bacterial adhesion - and macrofouling -- attachment of larger organisms. Examples of macrofouling organisms include: hard, encrusting animals such as barnacles, molluscs, tube worms and bryozoans; and soft, non-calcareous biofoulants include hydroids and seaweed. Some of these groups have been studied in considerable detail, while other major biofouling organisms such as the bryozoans, are said to be much more poorly understood.

Biofouling is a major concern for all industries working in the marine environment. In the marine energy industry such concerns pertain to periods when the devices are deployed and working, and when the devices are moored in harbours for maintenance or down-time. A number of issues include:

• Increases to surface weight and roughness thereby impacting drag, and survivability of devices.
• Biofouling on turbine blades, decreasing efficiency of energy generation.
• Contributing to or accelerating corrosion of marine metals that could affect subsea connectors.
• Providing surfaces on artificial structures in the marine environment which may create 'stepping-stone' habitats for the spread of fouling communities.

In an effort to build a clearer picture and fill any knowledge gaps, which will ultimately help marine energy developers to drive down costs, ICIT has been carrying out research in collaboration with the European Marine Energy Centre (EMEC) and Heriot-Watt's Energy Academy.

The initial stages of a project looking at biofouling solutions for marine renewables has just been completed. Work focused on the development of a knowledge network enabling biofouling experts to work closely with marine energy test site personnel and technology developers. Their goal was to gather data, share knowledge and formulate expertise on the specific aspects of biofouling that are relevant to the marine renewables industry.

Initial field research was carried out at EMEC's wave and tidal energy test sites to identify common fouling organisms found in Orkney waters. Key ones which were identified here include barnacles, calcified worms, kelp, hydroids and bryozoans. Scientists from Heriot Watt University were able to utilise their expert knowledge regarding the taxonomy and life cycles of several groups of these biofouling organisms.

Key considerations which evolved from this project include recommendations about the timing of device deployment and maintenance schedules. His have to be worked out in order to minimise major biofouling settlements and ease removal before the organisms consolidate. It is suggested that maintenance is timed for early summer to remove young barnacles and, if possible, again at the end of the summer to remove macroalgae.

The initial establishment of a network of renewable energy developers and biofouling experts has been heralded as a success. It will help facilitate the sharing of relevant information and collaboration for future development of innovative solutions and funding proposals. However those involved in the initial project stress that more work is needed.

"Further work is needed to understand how the timing of settlement of these types of organisms could impact the fouling of artificial structure deployment and maintenance schedules," Porter says.

Although various test centres have begun to gather data on native and non-native fouling organisms during deployments of devices, the issues of fouling are described as being far from fully resolved.

"Ideally we'd like to develop a map of biofouling in key strategic areas for the marine industries around Orkney, and then expand it to include other key marine renewables sites around the world," adds Matthew Finn, Senior Business Development Manager at EMEC."Now that the initial collaborations have been made, and a network of interested parties is being built, we are looking to build these initial studies into larger research projects and identify the funding mechanisms which we can use to fill these key knowledge gaps."

Reference
Biofouling Solutions For Marine Renewables: Knowledge Network Development. Final Report. July 2015 by Heriot Watt University, EMEC and ICIT. www.emec.org.uk

Further research

Knowledge gaps were identified during the research carried out by EMEC, ICIT and Heriot-Watt's Energy Academy. Future proposals which could be considered include:

• Quantitatively analysing decreases in energy extraction from biofouling - involving engineers and developers.
• Connecting with developers in Orkney to access devices before cleaning and to source data on deployment history (place, length of time, depth, salinity, temperature etc).
• Propose mitigation actions such as timings of clearing and coating; which organisms and what times and in what circumstances? i.e. deployment and maintenance scheduling.
• Consideration of standardisation of biofouling monitoring procedures.
• Establishment of Orkney as a centre for long-term monitoring of the marine ecosystem; or part of a European Observatory Organisation.
• Determining biofouling contribution to sensor accuracy, e.g. wave resource assessment and device capture may be undervalued as organisms affect movement of buoys and devices.