Responses of corals to chronic turbidity

Area of Science:

• Marine Biology
• Ecotoxicology
• Environmental Science

Background:

• Dredging operations elevate suspended sediment concentrations (SSCs), leading to increased water turbidity and light attenuation.
• Reduced light availability significantly impacts light-dependent organisms such as corals, crucial for reef ecosystems.

Purpose of the Study:

• To investigate coral physiological responses to prolonged exposure to elevated turbidity and light reduction.
• To develop predictive models for managing dredging impacts on coral health.

Main Methods:

• Utilized an automated sediment dosing system to precisely control SSCs and light levels.
• Exposed four common coral species with diverse morphologies to turbidity treatments (0-100 mg L⁻¹) for approximately 7 weeks.
• Monitored symbiotic dinoflagellate density, algal pigments, photosynthetic yields, lipids, and growth rates.

Main Results:

• Coral physiological parameters including symbiotic dinoflagellate density, pigment concentration, photosynthetic yields, lipid profiles, and growth varied significantly across turbidity treatments.
• Corals demonstrated photoacclimation under low turbidity conditions.
• High turbidity treatments induced bleaching and altered lipid metabolism in most coral species.

Conclusions:

• Most coral species, excluding *P. damicornis*, could acclimate to moderate turbidity (10 mg L⁻¹ SSC) and reduced light (2.3 mol photons m⁻² d⁻¹) over 7 weeks.
• Elevated SSCs and associated light reduction pose significant physiological stress to corals, with species-specific tolerance levels.
• Findings aid in predicting and mitigating the ecological consequences of marine dredging activities on coral reefs.