Mercury Biomagnification Through a Coral Reef Ecosystem.

Area of Science:

• Marine Biology
• Environmental Chemistry
• Ecotoxicology

Background:

• Coral reefs exhibit high biodiversity, suggesting complex food webs.
• Complex food webs with lateral links are hypothesized to reduce biomagnification.
• Mercury (Hg) is a persistent environmental contaminant of concern in marine ecosystems.

Purpose of the Study:

• To test if high biodiversity in Florida coral reefs reduces mercury biomagnification.
• To investigate mercury levels and trophic magnification in reef fish and invertebrates.
• To compare mercury biomagnification between two distinct reef sites.

Main Methods:

• Collected muscle tissue from 50 fish and invertebrate species at two Florida reef sites (April 2012 - December 2013).
• Analyzed total mercury (Hg) concentrations using established methods.
• Utilized stable isotopes of nitrogen (δ¹⁵N) and carbon (δ¹³C) to assess trophic positions and food web structure.
• Calculated Trophic Magnification Slopes (TMS) to quantify mercury biomagnification.

Main Results:

• Mercury levels in fish muscle tissue reached up to 6.84 mg/kg.
• Highest mercury concentrations were found in porkfish (Anisotremus virginicus), a cleaner fish, not in top predators like great barracuda (Sphyraena barracuda).
• Trophic Magnification Slopes (TMS) for mercury did not differ significantly between the two study sites.
• The measured TMS values were comparable to those reported for other ecosystems, indicating mercury biomagnification was not reduced.

Conclusions:

• High biodiversity and complex food webs in the studied Florida coral reef system did not reduce mercury biomagnification.
• Mercury biomagnification in fish muscle tissue occurred at levels consistent with other ecosystems.
• The trophic role of species, such as cleaner fish, may influence mercury accumulation patterns.
• Further research is needed to understand the specific mechanisms driving mercury accumulation in coral reef food webs.