Recording-2025-02-21T14:35:01.165Z

Jetties

• Definition: Man-made structures built perpendicular to the shore.

• Purpose: Control inlet migration and connect coastal bays with open seas.

• Functions:

  • Found at entrances to harbors, lagoon outlets, and river mouths.

  • Protect coasts from erosion, manage sediment transportation, and outline navigation channels.

• Materials: Constructed primarily from stone, wood, or concrete.

• Ecological Benefits: Provides habitat for marine life, particularly juvenile species, by creating nooks and crannies.

• Tourist Utility: Offers access to coastal areas for recreational activities like fishing.

• Construction Challenges: Expensive to build and maintain; can clog with sand and may require dredging.

• Limitation: Jetties tend to disrupt natural sand flow, leading to erosion elsewhere.

Groins

• Definition: Man-made structures similar to jetties, built perpendicular to the shore to maintain updrift beaches.

• Purpose: Capture sand and restrict longshore currents to prevent beach erosion.

• Construction Materials: Made from boulders, concrete blocks, steel, or wood.

• Functionality: Designed as a permanent solution to beach erosion, often deployed in series along beaches.

• Ecological Impact: Can disrupt natural habitats and sediment circulation; create downdrift erosion, which may increase repair costs.

• Problematic Aspects: Over time, groins can lead to unintended consequences like increased erosion in downdrift areas, necessitating more dredging.

Comparison: Jetties vs. Groins

• Jetties:

  • Robust structures that redirect longshore currents.

  • Protect the coast from tides, currents, and erosion.

  • Typically longer and extend into the water.

• Groins:

  • Shorter in length, starting on land and extending into water.

  • Captures sand and maintains beach structure.

  • Often constructed in series to work collectively for sediment management.

Marine Biology - Acorn Barnacles

• Species: Balanus (acorn barnacle) with a unique shell structure.

• Habitat and Behavior: Commonly found in clusters on rocks; filter feeders using feather-like legs to capture prey from water.

• Adaptation: Can close up when out of water to retain moisture and protect themselves.

• Reproductive Strategy: Older barnacles emit chemicals to attract younger ones, enhancing chances of reproduction and increasing species biodiversity.

Marine Biology - Oyster Drills

• Species: Straminida hemostoma, a predatory snail often found in shallow waters.

• Predatory Behavior: Drills into oysters and barnacles using its rasping tongue (radula) to consume them, contributing to a decline in oyster populations.

• Challenges: Difficult to control their population as altering the environment to affect them can harm oyster survival and reproduction.