RESUMO
The Gulf of Mexico blue carbon habitats (mangroves, seagrass, and salt marshes) form an important North American blue carbon hot spot. These habitats cover 2,161,446â¯ha and grow profusely in estuaries that occupy 38,000â¯km2 to store substantial sedimentary organic carbon of 480.48â¯Tgâ¯C. New investigations around GoM for Mexican mangroves, Louisiana salt marshes and seagrasses motivated our integration of buried organic carbon to elucidate a new estimate of GoM blue carbon stocks. Factors creating this include: large GoM watersheds enriching carbon slowly flowing through shallow estuarine habitats with long residence times; fewer SE Mexican hurricanes allowing enhanced carbon storage; mangrove carbon productivity enhanced by warm southern basin winter temperatures; large Preservation reserves amongst high anthropogenic development. The dominant total GoM mangrove blue carbon stock 196.88â¯Tg from total mangrove extent 650,482â¯ha is highlighted from new Mexican data. Mexican mangrove organic carbon stock is 112.74â¯Tg (1st sediment meter) plus USA 84.14â¯Tg. Mexican mangroves vary greatly in storage, total carbon depositional depths and in sediment age (to 3500â¯y). We report Mexican mangrove's conservative storage fraction for the normally-compared top meter, whereas the full storage depth estimates ranging above 366.78â¯Tg (high productivity in very deep sediment along the central Veracruz/Tabasco coast) are not reflected in our reported estimates. Seagrasses stock of 184.1â¯Tgâ¯C organic is derived from 972,327â¯ha areal extent (in 1st meter). The Louisiana marshes form the heart of GoM salt marsh carbon storage 99.5â¯Tg (in 1st meter), followed by lesser stocks in Florida, Texas, finally Mexico derived from salt marsh extent totaling 650,482â¯ha. Constraints on the partial estuarine fluxes given for this new data are discussed as well as widespread anthropogenic destruction of the GoM blue carbon. A new North American comparison of our GoM blue carbon stocks versus Atlantic coastal blue carbon stock estimates is presented.
Assuntos
Carbono/análise , Monitoramento Ambiental , Sedimentos Geológicos/química , Ecossistema , Estuários , Golfo do MéxicoRESUMO
Seagrasses comprise a substantive North American and Caribbean Sea blue carbon sink. Yet fine-scale estimates of seagrass carbon stocks, fluxes from anthropogenic disturbances, and potential gains in sedimentary carbon from seagrass restoration are lacking for most of the Western Hemisphere. To begin to fill this knowledge gap in the subtropics and tropics, we quantified organic carbon (Corg) stocks, losses, and gains from restorations at 8 previously-disturbed seagrass sites around the Gulf of Mexico (GoM) (n=128 cores). Mean natural seagrass Corg stocks were 25.7±6.7MgCorgha-1 around the GoM, while mean Corg stocks at adjacent barren sites that had previously hosted seagrass were 17.8MgCorgha-1. Restored seagrass beds contained a mean of 38.7±13.1MgCorgha-1. Mean Corg losses differed by anthropogenic impact type, but averaged 20.98±7.14MgCorgha-1. Corg gains from seagrass restoration averaged 20.96±8.59Mgha-1. These results, when combined with the similarity between natural and restored Corg content, highlight the potential of seagrass restoration for mitigating seagrass Corg losses from prior impact events. Our GoM basin-wide estimates of natural Corg totaled ~36.4Tg for the 947,327ha for the USA-GoM. Including Mexico, the total basin contained an estimated 37.2-37.5Tg Corg. Regional US-GoM losses totaled 21.69Tg Corg. Corg losses differed significantly among anthropogenic impacts. Yet, seagrass restoration appears to be an important climate change mitigation strategy that could be implemented elsewhere throughout the tropics and subtropics.