Crab Bioturbation and Seasonality Control Nitrous Oxide Emissions in Semiarid Mangrove Forests (Ceará, Brazil)

• Main Authors: Xosé L. Otero, José M. C. Araújo, Diego Barcellos, Hermano M. Queiroz, Danilo J. Romero, Gabriel N. Nóbrega, Marcos Siqueira Neto, Tiago O. Ferreira
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Applied Sciences
• Subjects: <i>ucides cordatus</i>; n₂o; mangroves; greenhouse gas; estuarine fauna
• Online Access: https://www.mdpi.com/2076-3417/10/7/2215

Seasonality and crab activity affects the nutrients and physicochemical parameters in mangrove soils, thus, affecting the emissions of greenhouse gases, such as nitrous oxide (N₂O). Climate change may intensify rainfall and/or enhance droughts, affecting mangroves and associated biota. Crabs are natural soil bioturbators responsible for soil aeration and turnover. We evaluated the effect of <i>Ucides cordatus</i> crab on N₂O emissions from mangrove soils under a semiarid climate in Northeastern Brazil. Soil and gas samples were collected over the rainy and dry seasons in crab-naturally-bioturbated and crab-exclusion mangrove plots. We measured the soil&#8217;s pH, redox potential, and the total contents of carbon, nitrogen, and sulfur. We found higher N₂O emissions in the crab-exclusion sites compared to the bioturbated sites, as well as higher N₂O emissions in the rainy season compared to the dry season. The fluxes of N₂O (&#181;g m^&#8722;2 h^&#8722;1) were 47.3 &#177; 9.7 and 8.9 &#177; 0.5 for the crab-exclusion sites, and 36.5 &#177; 7.8 and 4.5 &#177; 2.1 for the bioturbated sites (wet and dry seasons, respectively). The soil turning over by macrofauna led to lower N₂O fluxes in natural crab-bioturbated areas, and seasonality was the environmental factor that contributed the most to the changes in N₂O emissions. Broadly, anthropic activities and seasonality influence nitrogen fate, N₂O emissions, and ecological services in coastal ecosystems.