ORIGINAL RESEARCH Potential Methane Production Associated with Aquatic Macrophytes Detritus in a Tropical Coastal Lagoon André Luiz dos Santos Fonseca 1 & Claudio Cardoso Marinho 2 & Francisco de Assis Esteves 2,3 Received: 11 August 2016 /Accepted: 11 April 2017 # Society of Wetland Scientists 2017 Abstract Anaerobic decomposition of aquatic macrophytes in the sediment of wetlands is a key source of methane to the atmosphere. An experiment was conducted in order to evaluate the potential methane production (PMP) in the sediment colo- nized by three species of aquatic macrophytes and in the lim- netic region of a tropical coastal lagoon. The incubations were prepared and maintained (70 days) at 25.0 °C, and the PMP was measured by gas chromatography. The initial concentrations of dissolved organic carbon (DOC), carbohydrates and methane in the sediment were also measured. The sediment colonized by emergent aquatic macrophytes showed higher PMP due to the higher amounts of carbohydrates. On the other hand, PMP was lower in the limnetic region, which showed lower amounts of carbohydrates. The carbon found in the limnetic region is main- ly originated from the refractory detritus of aquatic macrophytes that reaches the central region of the lagoon, with lower carbo- hydrate content. These results indicate that detritus quality, which means highest concentration of carbohydrates in the DOC, was the main controlling factor of methanogenesis. Keywords Methanogenesis . Global warming . Greenhouse gas . Tropical wetlands . Sediment . Detritus quality Introduction Aquatic macrophytes decomposition is a fundamental process for carbon (C) and nutrient cycling in aquatic ecosystems (Rejmánková and Sirová 2007). The breakdown of aquatic plant detritus significantly provides organic compounds and releases C in the forms of DOC and CO 2 (Bianchini and Cunha-Santino 2008). However, incomplete decomposition of aquatic detritus generally increases carbon storage in the sediment (Costantini et al. 2009; Geurts et al. 2010). The decomposition of organic carbon accumulated in the sediment occurs primarily by anaerobic processes. Methanogenesis is the primary route of anaerobic decomposition of organic mat- ter in freshwater sediments, accounting for 30–80% of anaer- obic carbon mineralization (Kuivila et al. 1988; Bédard and Knowles 1991), generating methane and carbon dioxide as end products in equimolar amounts (Corbett et al. 2013). Considering that wetlands store 20–30% of organic carbon stocked in the terrestrial soils and are the main natural sources of CH 4 to the atmosphere (Bousquet et al. 2006; Bridgham et al. 2013), studies addressing the factors that influence meth- ane production are critical for gaining a fundamental under- standing of the methane cycle in such ecosystems. Among the factors that control methanogenesis, detritus quality plays a major role (Reiche et al. 2010; Fonseca et al. 2015). Interspecific variations in macrophytes’ features usual- ly result in differences in detritus quality and, consequently, in methanogenic rates. In general, detritus with low structural carbon content as well as low C:N, C:P, and N:P ratios is considered to have high detritus quality (Li et al. 2012). This kind of detritus decays faster in the water column and, conse- quently, presents lower accumulation in the sediment (Enríquez et al. 1993; Rejmánková and Houdková 2006), which potentially influences the methanogenic process. In ad- dition, living plants release root exudates, which are organic * André Luiz dos Santos Fonseca andre.fonseca@ifrj.edu.br 1 Instituto Federal de Educação, Ciência e Tecnologia do Rio de Janeiro, Rua Professor Carlos Wenceslau, 343, Rio de Janeiro, Brazil CEP: 21715-000 2 Laboratório de Limnologia, Departamento de Biologia, Universidade Federal do Rio de Janeiro, Avenida Brigadeiro Trompowski, s/n, Cidade Universitária, Rio de Janeiro, Brazil CEP: 21941-540 3 Núcleo em Ecologia e Desenvolvimento Sócio Ambiental de Macaé, Universidade Federal do Rio de Janeiro, Av. São José do Barreto, 764, Barreto, Macaé, Rio de janeiro, Brazil CEP: 27965-045 Wetlands DOI 10.1007/s13157-017-0912-6