Do marine protected areas influence mercury exposure? Insights from a shark community in the tropical Northeast Pacific
Abstract
Biomass depletion caused by overfishing is likely to alter the structure of food webs and impact mercury transfer to marine predators. Although marine protected areas (MPAs) are spared from fishing pressure, their influence on biota mercury levels is poorly understood. Here, we used carbon and nitrogen stable isotope compositions as well as mercury concentrations in fin clips to characterize foraging habitat and mercury exposure of a shark community composed of migratory and resident species of the Revillagigedo archipelago, an offshore MPA in the Northeast Pacific off Mexico. We found that the probability of finding migratory sharks in the isotopic niche of Revillagigedo-resident sharks was low, likely reflecting the use of habitats outside the archipelago by highly mobile species. Community-wide variations in mercury were primarily explained by shark length, revealing that bioaccumulation was the main driver of Hg concentrations. We failed to detect a clear effect of foraging habitat on shark mercury exposure, which may be related to migratory species using both exploited and protected areas when moving outside the Revillagigedo MPA. More similar studies on the potential mitigation of Hg contamination by MPAs are needed in the future if fishing pressure increases to satisfy the growing global human population
Keywords
bioaccumulation
Carcharhinus albimarginatus
Carcharhinus falciformis
Carcharhinus galapagensis
concentration (parameter)
controlled study
environmental exposure
environmental protection
fishing
foraging
Galeocerdo cuvier
geographic names
isotope analysis
migratory fish
nonhuman
Pacific Ocean
Revillagigedo Archipelago
sea pollution
shark
species difference
species habitat
tropics
water pollution control
carbon and nitrogen
Carbon stable isotopes
Food webs
Marine protected area
Mercury concentrations
Mercury exposure
Nitrogen stable isotope
Northeast pacific
Revillagigedo archipelago