Mucous Secretion and Cilia Beating Defend Developing Coral Larvae from Suspended Sediments

Area of Science:

• Marine Biology
• Ecology
• Coral Reef Science

Background:

• Suspended sediments from dredging and runoff pose risks to marine ecosystems.
• Understanding sediment impacts on coral life stages is crucial for coastal and reef management.

Purpose of the Study:

• To assess the effects of varying suspended sediment concentrations and types on coral embryos and larvae.
• To determine concentration-response relationships for survivorship and metamorphosis in corals.

Main Methods:

• Exposed coral embryos (Acropora tenuis, A. millepora) and larvae (A. tenuis, A. millepora, Pocillopora acuta) to siliciclastic and carbonate sediments.
• Evaluated survivorship and metamorphosis under different exposure durations and sediment concentrations.
• Utilized microscopy to examine embryo responses, including cocoon formation.

Main Results:

• Coral embryos and larvae showed no significant reduction in survivorship or metamorphosis at sediment concentrations up to ~1000 mg L-1.
• A novel response observed: ~10% of embryos formed negatively buoyant cocoons with sediment coatings at ≥35 mg L-1 siliciclastic sediment.
• Cocoon formation, more prevalent with siliciclastic sediments, was not observed in larvae; embryos emerged from cocoons post-transfer.

Conclusions:

• Mucous secretion and cilia beating are effective protective mechanisms for coral embryos and larvae against suspended sediments.
• These physiological responses may significantly enhance the recruitment success of corals in sediment-affected marine environments.