How does marine growth threaten structures?

1. Physical Penetration and Attachment

    •    Barnacles and oysters attach by secreting strong adhesives that bond permanently to surfaces. On organic pilings (like treated wood), this attachment breaks down protective coatings, exposing the material underneath.

    •    As they grow, barnacles bore micro-crevices into the surface. This can lead to cracking and splintering over time, especially in softer or aging wood.

 

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 2. Moisture Retention and Water Trapping

    •    These organisms trap water between themselves and the piling surface.

    •    Constant moisture accelerates rot and fungal decay in wood, especially in the intertidal zone where drying should naturally occur.

    •    Oxygen-starved wet pockets foster anaerobic bacteria, which can lead to sulfide corrosion in treated wood or even nearby metal fasteners.

 

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 3. Biological Synergy (Biofouling Communities)

    •    Once oysters and barnacles colonize, they attract other fouling organisms like worms, algae, sponges, and boring mollusks.

    •    For example, shipworms (Teredo navalis) and gribbles (Limnoria) are notorious for boring into wooden pilings, and they thrive in the moist microenvironments created by barnacle mats.

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 4. Weight Load and Structural Stress

    •    A mature colony can add significant weight and drag, especially during tides, storms, or waves.

    •    This increased stress can lead to structural fatigue or breakage, especially in older or poorly maintained pilings.

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5. Chemical Breakdown of Protective Treatments

    •    Over time, oysters and barnacles contribute to acidic micro-environments, especially if they’re accompanied by bacterial colonies.

    •    These can neutralize or erode copper-based wood preservatives, accelerating decay in treated pilings.

 

6. Patron risk:
  • Oysters and barnacles are protected by durable and sharp calcium carbonate shells. 

  • filter feeders accumulate bacteria and toxins introduced by urban activity. Oysters in the Tampa Bay Area can carry the dangerously infective species Vibrio vulnificus.