Stowaways – The Marine Life Hitching A Lift On Your Boat

Fouling – What Is It?

Once I naively thought that you bought a boat, put it on the water, made sure the woodwork and rigging were kept up to scratch and then sailed away into the sunset. No way!!! Once in the water a nasty, vicious, undersea army is waiting to attach itself to your boat.

Fouling begins with a layer of slime or bio film which can form on anything under the water line and then attracts marine plants and animals. Organisms such as algae, sea squirts, barnacles, muscles and even sponges can attach themselves to hulls, propellers, anchors, lines and fishing gear and it is believed that over 1,700 different species are responsible for fouling. There are basically two types of fouling, micro fouling which includes micro organisms and bacteria and macro fouling which is the attachment of larger organisms. They can also be divided into hard and soft types. Hard or calcareous organisms include barnacles, mussels, bryozoans, molluscs and tube worms, while soft or non-calcareous organisms are algae, seaweed, hydroids and slime.

More About Your Stowaways

  • The Ascidians or Sea Squirts are sac-like invertebrate filter feeders with a tough outer skin. Found all over the world in shallow, salt water they attach themselves to rocks, shells and, more importantly, boats. Some types are solitary, while other form large colonies several meters in diameter.
  • Bryozoa, commonly known as moss animals are also invertebrate filter feeders. They are around 0.5 millimetres long and sieve food particles from the water using a crown of tentacles. There are over 4,000 different species, most of which live in colonies. The most common marine form is encrusting. It forms a sheet of organisms over a hard surface or over seaweed, having an exoskeleton reinforced with calcium carbonate. The colony grows by asexual budding and each colony can last up to about 12 years. They will be some of the first colonisers of new or recently cleaned boats.
  • Mussels are edible bivalves which attach themselves to a firm object by means of a strong byssal thread or beard. Zebra Mussels are particularly invasive. They are a species of freshwater mussel which originated in the Balkans, Poland and the former Soviet Union. Since then they have become an invasive species in many other countries and are present in Britain's waterways. Small though they are, they can cause a huge amount of damage by attaching to objects, clogging up pipes and even killing other types of mussels.
  • Molluscs compose a huge range of invertebrate animals. There are around 85,000 species, many of which comprise a shell covering the body parts and a foot with which it attaches itself.
  • Barnacles are encrusters which attach themselves permanently to a hard object. Some types grow their shells directly onto the object while others attach themselves by a stalk. They are suspension feeders, living permanently in their shell.
  • Polychaetes and tube worms are marine worms who anchor their tail to an underwater object. They then secrete a mineral tube around their body into which they can withdraw completely. Polychaetes are sometimes referred to as Bristle Worms because of the bristles along their body.
  • Hydroids are small predators, related to jellyfish, which attach themselves directly to a hard object. The majority live in colonies and reproduce by producing buds along a branching stem.
  • Gribble Worms are marine isopods, some varieties of which bore into wood for food. These little shrimp-like creatures often occur in areas of mud and can invade your boat if you have not kept up with your antifouling.

"So what", you may say, "they're not doing any harm just hitching a ride". Big mistake!! "Fouling" as it is called, can affect your boat's speed, fuel efficiency and maintenance costs. Powerboats will use more fuel and sailing boats will slow down because of the friction these unwanted passengers can cause, breaking up the smooth line of the hull. It can also affect the manoeuvrability of your boat and can damage woodwork and paintwork if left too long without removal. The type of fouling you experience will depend on where the boat is kept, how long it is in the water and the climate.

Some Alarming Facts

  • Over time accumulation of fouling organisms can lead to an increased drag of up to 60%.
  • The increased drag can decrease speed by up to 10%.
  • The resulting increased fuel consumption could be up to 40%.
  • The increase use of fuel may lead to adverse environmental effects and an increase of carbon dioxide and sulphur dioxide emissions. However there may be environmental issues when toxic antifouling paint is used.

Boats that remain stationary in the water for long periods at a time are most susceptible to hull fouling, especially if they are not protected regularly by antifouling paint. Boats that are trailered to the water do not usually have enough time to be affected by hull fouling although they can carry organisms on other parts of their equipment.

It's ironical that while most boat lovers care greatly about our marine environment and marine life, yet some of these very creatures are wreaking havoc to their boats.

Read my next article, "Antifouling – The Hows And Whys", to discover facts, figures and advice about this tricky subject.

Author – Dee White

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