Evaluation of toxicity of polluted marine sediments from Bahía Salina Cruz, Mexico

Abstract

Bahía Salina Cruz, Oaxaca, Mexico is a major center of oil and refined product distribution on the Mexican Pacific coast. From the start of oil industry operations in 1979, negative effects from discharges of treated effluents in the bay have been a constant concern for local communities. We analyzed 28 surface sediment samples obtained in June, 2002 to evaluate the level of toxicity in the littoral zone, port-harbor, and La Ventosa estuary in Bahía Salina Cruz. The extractable organic matter concentration was high (1213 to 7505 μ g g⁻¹) in 5 of 7 stations from the port and harbor, whereas it was low in 12 of 16 stations in the littoral zone (36 to 98 μ g g⁻¹). The total aromatic hydrocarbon concentration was highest (57 to 142 μ g g⁻¹) in the port and harbor compared to the La Ventosa estuary and the littoral zone. Among the heavy metals analyzed, cadmium exceeded the effects range-low values associated with adverse biological effects. The geo-accumulation index of sediments was moderate to strong contamination at 5 stations in the nonlittoral and 6 stations in the littoral zone. The enrichment of lead, zinc, and cadmium at 5 stations from the littoral, port, and harbor suggest that these metals are of anthropogenic origin. Bioassay tests of elutriates of sediments on nauplii of Artemia franciscana and Artemia sp. showed that the port and harbor were more toxic than the La Ventosa estuary and the coastal zone. The Microtox test (Vibrio fischeri) did not show a similar response with the solid phase of the sediments. The results of this study indicate that the high levels of organic content and metals in the sediments of port-harbor and the La Ventosa estuary are mainly caused by anthropogenic activities.

Keywords:

• Toxicity
• heavy metals
• hydrocarbons
• bioassays
• sediments
• Salina Cruz
• Oaxaca

Acknowledgments

This research was supported by Mexican Petroleum Institute. Cristina González-Lozano was a doctorate student in the postgraduate program of CIBNOR. We thank Pablo Monsalvo-Spencer for his assistance during the Artemia bioassays, and Dr. Ellis Glazier for editing this English-language text.

Notes

*Concentrations exceeded effects range-low levels (Long et al.^{[ 28 ]}).