Mercury concentrations and stable isotopes (δN and δC) in fish muscle indicate human impacts in tropical coastal lagoons.

Coastal lagoons are essential nursery habitats of many marine fishes, but they are often sites of intense human activities that impact water quality and potentially the fish using these habitats. We compared the variability in nutrient uptake (using δN and δC) and total mercury (THg) levels in juveniles and adults of three common species in two lagoons on the central Mexican coast of the Pacific Ocean during the wet and dry seasons. One of three species, Achirus mazatlanus had higher THg, δN, and δC levels in the lagoon with the greatest wastewater inputs (Barra de Navidad).

Fishes as indicators of untreated sewage contamination in a Mexican coastal lagoon.

Lagoons are important nursery habitats for fishes but are often sites of intense human activity including wastewater discharges. The goal of this research was to compare stable nitrogen (δN) and carbon (δC) isotopes, total mercury (THg) and other metal levels in four selected fish species among sites with different levels of untreated sewage discharge inside Barra de Navidad coastal lagoon in the Mexican Pacific. Three species from sites heavily impacted by sewage showed higher δN and δC compared to those from non-impacted sites.

[Species and size composition of fishes in Barra de Navidad lagoon, Mexican central Pacific].

Coastal lagoons are considered important nursery areas for many coastal fishes. Barra de Navidad coastal lagoon (3.76km2) is important for local economy as it supports tourism development and artisanal fisheries.