Carbon storage and greenhouse gas fluxes in the San Juan Bay Estuary: Current trends and likely future states.
Martin, R., C. Wigand, A. Oczkowski, Alana Hanson, E. Santos, AND E. Huertas. Carbon storage and greenhouse gas fluxes in the San Juan Bay Estuary: Current trends and likely future states. EPA Workshop, San Juan, San Juan, PUERTO RICO, June 09, 2017.
In Puerto Rico's San Juan Bay Estuary, historic filling of the Martin Pena Canal has resulted in decreased tidal flow. Coupled with excessive nutrient loading, these hydrological changes may be altering carbon storage and sequestration in San Juan Bay Estuary's mangrove ecosystems. We measured fluxes of the greenhouse gases methane and carbon dioxide during rain and dry seasons at five sites along a gradient of human influence in the San Juan Bay Estuary. Our findings demonstrate substantial methane emissions from wetlands bordering the heavily human-altered Martin Pena Canal relative to other sites, suggesting that nutrient pollution and/or tidal restriction are driving loss of the mangrove wetland carbon sink in the form of methane emission. There have been few studies of carbon cycling in urban mangrove ecosystems, and so these results may be of use for ecosystem service management and conservation / restoration planning. In addition, these results contribute to a larger body of work performed under SHC 2.61 assessing relationships between human and environmental health in the San Juan Bay Estuary and will be incorporated into modeling efforts.
Mangrove systems are known carbon (C) and greenhouse gas (GHG) sinks, but this function may be affected by global change drivers that include (but are not limited to) eutrophication, climate change, species composition shifts, and hydrological changes. In Puerto Rico’s San Juan Bay Estuary, mangrove wetlands are characterized by anthropogenic impacts, particularly tidal restriction due to infilling of the Martin Pena Canal and eutrophication. The objective of our research is to measure carbon sequestration and carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes in the San Juan Bay Estuary to understand the sustainability and role in global climate of this urban mangrove ecosystem. Cores for C sequestration measurements were collected and GHG fluxes were measured during rainy and dry seasons at 5 sites along a gradient of development and nitrogen loading in the San Juan Bay Estuary. At each site, paired GHG flux measurements were performed for mangrove wetland soil and estuarine water using static and floating chambers. Our results suggest a positive relationship between urban development and CH4 and N2O emissions, and demonstrate that in this system, estuarine waters are a major methane source. In addition to providing characterization of GHG fluxes in an urban subtropical estuary, these data provide a baseline against which future states of the estuary (after planned hydrological restoration has been implemented) may be compared.