Combined environmental stress from shrimp farm and dredging releases in a subtropical coastal lagoon (SE Gulf of California).

Nutrient pollution causes environmental damages on aquatic ecosystems worldwide. Eutrophication produces impacts in coastal ecosystems, affecting biota and ecosystem services. The Urias coastal lagoon (SE Gulf of California) is a sub-tropical estuary under several environmental pressures such as nutrient inputs from shrimp farm effluents and dredging related to port operations, which can release substances accumulated in sediments. We assessed the water quality impacts caused by these activities and results showed that i) nitrogen was the limiting nutrient, ii) shrimp farm effluents increased particulate organic matter and chlorophyll a in the receiving stations, and iii) dredging activities increased nitrite and reduced dissolved oxygen concentrations. The co-occurrence of the shrimp farm releases and dredging activities was likely the cause of a negative synergistic effect on water quality which mainly decreases dissolved oxygen and increases nitrite concentrations. Coastal zone management should avoid the co-occurrence of these, and likely others, stressors in coastal ecosystems.

Health risk assessment from mercury levels in bycatch fish species from the coasts of Guerrero, Mexico (Eastern Pacific).

With the aim of determining Hg distribution in muscle and liver of bycatch fish from Guerrero state in the Eastern Pacific Ocean and assess the potential risk to consumer, Hg was quantified in 14 species of bycatch fish. For the majority of fish the order of Hg levels was liver > muscle. The highest concentration corresponded to the liver of Isopisthus remifer (2.05 µg g(-1)) and the lowest (0.02 µg g(-1)) was detected in muscle of Prionotus sp. The highest hazard quotient (0.75) was found in the Mexican milkfish Micropogonias ectenes; considering all the individuals, mean hazard quotient was 0.336.