Barnacles are a common sight on boats, often appearing as hard, cone-shaped growths clinging to the hull. While they might seem like a minor nuisance, these marine organisms can pose significant challenges for boat owners. Understanding their nature and why they attach to vessels helps clarify their impact and management.
Understanding Barnacles
Barnacles are crustaceans, relatives of crabs, lobsters, and shrimp. As adults, these marine invertebrates are sessile, meaning they permanently attach to a surface. They form a hard, calcified shell that protects their soft bodies. They feed by extending feather-like appendages called cirri into the water, sweeping for microscopic organisms like plankton.
Barnacles begin their lives as free-swimming larvae, progressing through two stages: the nauplius and the cyprid. The nauplius larva is a feeding stage, while the cyprid larva is non-feeding and finds a suitable place to settle. This cyprid stage is when barnacles seek out and attach to surfaces.
Why Barnacles Attach to Boats
The cyprid larval stage explores potential surfaces using modified antennules. Once a suitable spot is identified, the cyprid secretes an adhesive known as barnacle cement. This biological glue hardens rapidly underwater, creating a strong bond that allows the barnacle to affix itself.
Boats provide an ideal environment for barnacle attachment and growth. The stable, hard surfaces of a hull offer a secure substrate, and constant water movement ensures a steady supply of food for filter-feeding adults. Barnacle larvae are also attracted to rough or porous surfaces, which offer increased surface area and crevices for better adhesion.
Consequences for Your Vessel
The accumulation of barnacles on a boat’s hull, known as biofouling, creates hydrodynamic drag. This increased resistance means the vessel’s engine must work harder to maintain speed, leading to reduced performance. Studies have shown that even a 10% barnacle coverage can increase fuel consumption by as much as 36% or more.
Beyond fuel inefficiency, barnacle growth can cause direct physical damage to the boat. Their strong adhesion can compromise hull coatings and paint when they are removed, potentially exposing the underlying material. Extensive growth can also affect propellers, disrupting their function, and even obstruct water intakes, which can lead to engine overheating. Such issues necessitate costly maintenance and repairs, impacting a boat’s longevity.
Strategies for Control
Preventing barnacle attachment involves several strategies.
Antifouling Paints
Applying specialized antifouling paints to the hull is a primary method. These paints contain biocides that deter marine organisms or create a slick surface. Ablative paints, for example, slowly wear away, continuously exposing fresh biocides. Environmentally friendly options, like silicone-based foul-release coatings, create a surface too slick for barnacles to firmly grip, allowing them to be washed away as the boat moves.
Regular Cleaning
Regular hull cleaning manages barnacle growth. This includes manual scraping, pressure washing, or applying chemical removers that dissolve barnacle husks and residue.
Dry Storage
For boats not constantly in the water, dry storage or using a boat lift keeps the hull out of the marine environment, preventing attachment. Consistent maintenance practices, including protective coatings, regular cleaning, or dry storage, are important for minimizing barnacle-related issues.