Jorge A Herrera-Silveira

USGS2017

Methane fluxes from tropical coastal lagoons surrounded bymangroves, Yucatán, Mexico

Methane concentrations in the water column and emissions to the atmosphere were determined for three tropical coastal lagoons surrounded by mangrove forests on the Yucatán Peninsula, Mexico. Surface water dissolved methane was sampled at different seasons over a period of 2 years in areas representing a wide range of salinities and anthropogenic impacts. The highest surface water methane concentrations (up to 8378 nM) were measured in a polluted canal associated with Terminos Lagoon. In Chelem Lagoon, methane concentrations were typically lower, except in the polluted harbor area (1796 nM). In the relatively pristine Celestún Lagoon, surface water methane concentrations ranged from 41 to 2551 nM. Methane concentrations were negatively correlated with salinity in Celestún, while in Chelem and Terminos high methane concentrations were associated with areas of known pollution inputs, irrespective of salinity. The diffusive methane flux from surface lagoon water to the atmosphere ranged from 0.0023 to 15 mmol CH 4 m −2 d −1 . Flux chamber measurements revealed that direct methane release as ebullition was up to 3 orders of magnitude greater than measured diffusive flux. Coastal mangrove lagoons may therefore be an important natural source of methane to the atmosphere despite their relatively high salinity. Pollution inputs are likely to substantially enhance this flux. Additional statistically rigorous data collected globally are needed to better consider methane fluxes from mangrove-surrounded coastal areas in response to sea level changes and anthropogenic pollution in order to refine projections of future atmospheric methane budgets.

Yucatam↗

USGS2003

The seagrasses of the Gulf of Mexico

The Gulf of Mexico is a vast basin of water, spanning 12° of latitude, from 18° to 30°N. and 17° of longitude, from 81° to 98°W. It is bisected by the Tropic of Cancer and is largely subtropical; however, along the northern edge, up to five days with freezing temperatures are probable on an annual basis. The coastal fringe is moist, with annual precipitation in excess of 1 000 mm, except for southern Texas and northern Mexico. Precipitation is concentrated in the summer period, most pronounced along the coast of Mexico and least pronounced along the coast of Louisiana. Most of the Gulf of Mexico is fringed by a broad coastal plain, except for northwestern Cuba and sections of the Mexican coast near Veracruz. The inner continental shelf to a depth of 20 m is broad off the western side of the Yucatan Peninsula, along the coast of Louisiana and along the western side of Florida, extending as much as 80 km offshore to the tip of Florida. Elsewhere, the inner shelf is relatively narrow. Most of the rivers draining into the Gulf of Mexico have restricted catchments, except along the north shore, most obviously the Mississippi River, and parts of the western gulf, including the Rios Bravo IGrandel, Panuco, Grijalva and Usumacinta. Barrier islands and spits are prominent features along much of the coast, and coral reefs shelter the large expanse of water off the southern tip of Florida and off the coasts of Veracruz, Campeche, Yucatan and northwestern Cuba. Lunar spring tides are less than 1 m throughout the region.

Book chapter↗