Barnacles are small crustaceans that attach themselves to hard surfaces like boats, docks, and whales. If you’ve ever wondered, “Are barnacles harmful?” you’re not alone. Barnacles can cause major headaches for boat owners and whalers, but they also play an important ecological role.

If you’re short on time, here’s a quick answer: Barnacles are generally not dangerous to humans, but they can damage boats, ships, and whales by attaching to and weighing down these surfaces. They can be very costly and time-consuming to remove.

In this approximately 3000 word article, we’ll take a deep dive into barnacles, including:

What Are Barnacles?

Barnacles are small marine crustaceans that attach themselves to hard surfaces like boats, pilings, and rocks. They have a hard outer shell for protection and use feathery appendages called cirri to filter food from the water.

Barnacles are found around the world along rocky shorelines and man-made structures.

Basic Biology and Life Cycle

Barnacles have a fascinating life cycle. They start as tiny free-swimming larvae, drifting with ocean currents until they find a suitable place to settle. Using special cements, barnacle larvae glue their heads to a surface and then transform into young barnacles.

As adults, barnacles continue to be permanently cemented in one place, using their cirri legs to catch food.

Feeding is key for barnacles. Their cirri legs catch tiny drifting plants and animals, passing the food to the mouth. Most barnacle species have separate sexes. Eggs are fertilized internally and later hatch into larvae, starting the cycle again.

Types of Barnacles

While over 1,000 species of barnacles exist, two main types are most common:

  • Rock/acorn barnacles – With hard protective plates, these species glue themselves to rocky shores, pilings, ship hulls, and more.
  • Gooseneck/stalked barnacles – Instead of cementing directly, these barnacles attach to surfaces using a muscular stalk. Species like Pollicipes polymerus are considered a delicacy.

The durability and permanence of barnacles have made them notoriously good at fouling man-made structures. Groups of barnacles accumulate on boat hulls, water pipes, dock pilings, and other marine infrastructure. This biofouling can create maintenance issues and increase costs.

However, barnacles also play a key ecological role. As filter feeders, they help recycle nutrients in the ocean. And the hard shells provide hiding spots and attachment sites for other organisms. So while sometimes considered a nuisance, barnacles are important members of marine ecosystems.

Problems Caused by Barnacles

Damage to Boats and Ships

Barnacles can cause extensive damage to boats and ships. As they accumulate on the hull, they increase drag, which slows the vessel down and reduces fuel efficiency. This costs ship owners a lot of money in extra fuel costs and maintenance expenses.

According to a 2021 study, biofouling by barnacles on commercial ships leads to an increase in fuel consumption of around 40%!

The extra weight and uneven distribution of barnacles also make boats less stable and more difficult to steer. Large buildups can corrode and weaken the hull, leading to expensive repairs. Before effective antifouling paints were developed, fast-moving ships like clipper ships could be reduced to half speed after just a few months due to the accumulation of barnacles!

To prevent and remove barnacles, boat owners often have to haul out their boats and perform extensive scraping, sanding and repainting. This process, called “de-fouling,” is costly, time-consuming and labor-intensive.

According to BoatUS, the average cost to haul out and clean the bottom of a 40-foot powerboat is $2,500. Ouch!

Impacts on Whales and Other Marine Life

Barnacles don’t just plague boats and ships. They can also heavily colonize whales and other marine mammals, weighing them down, impairing their mobility, and increasing their drag as they swim. According to NOAA, North Atlantic right whales often have so many barnacles attached to them that their calving rates are affected.

One study found 389 pounds of barnacles on a single right whale! Researchers noted the barnacles caused “extreme changes” to the whale’s body shape and swimming behavior. They had to flap their tails harder to swim and couldn’t roll as easily, which uses up extra energy.

Other species like humpback and gray whales can also accumulate barnacles around their blowholes, eyes, fins and tails. This not only slows them down, but can also lead to openings in the skin for dangerous bacterial infections.

Biologists have to carefully remove the barnacles to improve the whales’ health.

Barnacles will readily grow on any inert surface in the ocean, so they can also attach to marine turtles, sharks, crabs, jellyfish and even whales washed up on the beach! While they rarely kill the animals, they definitely negatively impact their ability to swim, eat and survive.

Removing and Preventing Barnacles

Manual Removal Techniques

Barnacles can be removed manually using simple hand tools like paint scrapers, putty knives, stiff brushes, and high-pressure water jets. Hand removal works best for light barnacle growth on boats, docks, pilings, and other submerged surfaces.

Be sure to wear waterproof gloves during manual removal to avoid cuts and skin irritation.

Some effective manual removal techniques include:

  • Scraping – Carefully scrape off barnacles with a plastic putty knife or paint scraper.
  • Brushing – Scrub hardened barnacles with a stiff brush to break bond from surfaces.
  • High-pressure washing – Use a pressure washer to blast off barnacles and their cement-like base.

The best time to manually remove barnacles is when they are still small and newly attached. Trying to eliminate mature, calcified barnacles takes more effort and can damage boat hulls. It’s recommended to inspect surfaces weekly and remove new barnacle growth right away.

Antifouling Paints and Coatings

Marine antifouling paints prevent barnacle attachment using leaching biocides like copper and zinc compounds. As the paint slowly dissolves, toxins are released to repel larvae for 1-2 seasons. Common antifouling paint types include:

Ablative Paints Copper-based paint wears away to expose fresh biocides. Offers around 12 months protection.
Hard Paints Glossy, durable copper paints provide multiple seasons of barnacle defense.
Silicone Paints Use slippery silicone oils to make surfaces “non-stick” to organisms like barnacles. Last 1-3 years.

In a recent survey, nearly 80% of boat owners relied on antifouling hull paints for barnacle prevention. When applied by professionals, quality antifouling coatings prevent over 90% of barnacle attachment for 1-2 years.

Other Preventative Measures

In addition to paints and coatings, boaters can help deter barnacles using these prevention methods:

  • Boat Lifting – Regularly lift boats from water to clean/dry hulls and prevent biofouling when not in use.
  • Sacrificial Anodes – Protect metal components with zinc anodes to reduce corrosion that enables barnacle growth.
  • Hull Waxing – Apply marine wax to fiberglass hulls for an ultra-smooth surface that deters barnacle larvae from sticking.
  • Ultrasound Devices – Battery-powered transducers emit ultrasound waves to repel organisms like barnacles without harming the environment [1].

Vigilance is key – diligently monitoring boat hulls and underwater structures allows early stage removal of young barnacles before they calcify and require harsher treatment. Consider a multi-pronged approach using manual cleaning, protective coatings, and preventative measures for the most effective barnacle defense.

Ecological Role of Barnacles

Part of Food Chain

Barnacles play an important role in the food chain of many marine ecosystems. Here are some key points about the ecological role of barnacles as food sources:

  • Barnacles are eaten by a variety of predators, including whelks, starfish, crabs, birds, and even humans in some cultures. This makes barnacles an important source of energy transfer to higher trophic levels.
  • Shorebirds such as oystercatchers often feed on barnacles, gaining crucial nutrition especially during migration when barnacles provide a reliable food source.
  • Whales, such as gray whales, feed on barnacle larvae during their long migrations, filtering huge volumes of water through their baleen plates to catch the nutritional larvae.
  • Barnacles that colonize whale skin and shells provide an important supplemental food source for the whales themselves when they are feeding.

So in essence, the rich caloric content of barnacles, combined with their immobile adult stage and frequent aggregation in dense clusters, makes them a vital prey species for birds, whales, and many other marine predators.

Habitat for Other Species

In addition to being food sources themselves, aggregations of barnacles often serve as critical habitat for other intertidal species. Here are some of the key ways barnacles create habitat:

  • The hard calcium carbonate shells of barnacles provide attachment points and protective cover for small invertebrates and newly settled larvae.
  • Mussels often anchor their byssal threads to the ridged plates of barnacles, using them as a sturdy base.
  • The crevices between barnacles offer hiding spaces from predators and strong wave action for small species like juvenile rockfish.
  • Dense clusters of barnacles help moderate temperature and humidity fluctuations for associated species during low tide.

Interestingly, one study found over 100 different species inhabiting a single barnacle cluster. This complex three-dimensional structure supports high biodiversity in the rocky intertidal zone. So by providing food, attachment sites, and refuge to other species, sedentary barnacle aggregations form vital biogenic habitat in nearshore ecosystems.


To conclude, while barnacles can certainly be a nuisance for maritime vessels and industries, they are generally not dangerous for humans. Their tenacious ability to adhere to hard surfaces can cause damage and increased fuel costs, so boat owners must be diligent in manually removing barnacles and using antifouling paints to prevent accumulation.

At the same time, barnacles play an important ecological role as prey species and by providing habitat for other organisms. So while no one wants a barnacle-encrusted boat, these stubborn little crustaceans are an integral part of the marine ecosystem.

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