Metals in horseshoe crabs from Delaware Bay

Area of Science:

• Environmental Science
• Marine Biology
• Ecotoxicology

Background:

• Horseshoe crabs (Limulus polyphemus) are a vital component of the Delaware Bay ecosystem.
• Assessing contaminant levels in horseshoe crabs is crucial for understanding potential risks to marine food webs.

Purpose of the Study:

• To determine locational differences in arsenic, cadmium, chromium, lead, manganese, mercury, and selenium concentrations in horseshoe crabs.
• To evaluate contaminant levels in horseshoe crab eggs, leg muscle, and apodeme.
• To assess trends in contaminant levels over time.

Main Methods:

• Collected horseshoe crabs from eight locations in Delaware Bay (New Jersey and Delaware sides).
• Analyzed concentrations of seven heavy metals (arsenic, cadmium, chromium, lead, manganese, mercury, selenium) in eggs, leg muscle, and apodeme.
• Compared contaminant levels across different locations and time periods (1993-2001).

Main Results:

• Identified some locational differences in contaminant concentrations, but these were not substantial.
• Found generally low levels of all measured contaminants in horseshoe crabs.
• Observed a general decline in contaminant levels in horseshoe crab eggs between 1993 and 2001.

Conclusions:

• Contaminant levels in Delaware Bay horseshoe crabs are below thresholds known to cause adverse effects.
• The low and declining contaminant levels suggest minimal risk to the crabs and their predators.
• Contaminants are unlikely to be a significant factor in the decline of secondary consumers.