## 1 Introduction  
Severe droughts and stronger storms are the future scenarios of global climate change, which may threaten innumerable ecosystems [1; 2; 3], including mangroves. Mangrove ecosystems contain the most carbon-rich soils on the planet [4; 5], characterized by fluctuations in the soil redox conditions due to tidal flooding [6; 7; 8]. Consequently, mangrove forests are one of the most important coastal carbon (C)sinks, contributing to the mitigation of climate change by sequestering and storing significant amounts of carbon, known as blue carbon [9; 10; 11; 12]. Mangrove macrofauna (especially the crab species) are known drivers for changing the soil's physicochemical conditions in intertidal environments and can directly affect greenhouse gas emissions, such as nitrous oxide (N\({}_{2}\)O) [13; 14; 15]. Crab burrows may change the air-water fluxes, increase the soil O\({}_{2}\) content, and oxidize the soil around the burrows [16]. The _Ucides cordatus_ crabs are one of the most important bioturbators of mangrove soils, turning over and inducing the natural recycling of nutrients and organic matter [17; 18]. Aerobic respiration, anaerobic iron, and sulfate reduction are usually the most important carbon oxidation pathways in mangrove soils [13; 19], while denitrification has been considered less important in the organic matter cycling of mature mangrove forests due to the limited availability of nitrate (NO\({}_{3}\)\({}^{-}\)) [20; 21]. However, investigations regarding N\({}_{2}\)O emissions have been increasing because it is considered a key greenhouse gas. Nitros oxide is produced as a by-product between the microbial pathways of denitrification and nitrification [22; 23; 24; 25]. Denitrification consists of the reduction of nitrite (NO\({}_{2}\)\({}^{-}\)) and NO\({}_{3}\)\({}^{-}\) as alternative electron acceptors to oxygen (O\({}_{2}\)), resulting in gaseous nitrogen production; this process is mediated by heterotrophic bacteria under anoxic conditions (anaerobic pathways) [26; 27; 28]. Nitrification may occur when ammonium (NH\({}_{4}\)\({}^{+}\)) is sequentially oxidized to nitrite/nitrate under aerobic conditions, and N\({}_{2}\)O production occurs by the reduction of NO\({}_{2}\)\({}^{-}\). The first step of nitrification is the oxidization of NH\({}_{4}\)\({}^{+}\) to nitrite (NO\({}_{2}\)\({}^{-}\)) via hydroxylamine (NH\({}_{2}\)OH) [29; 30]. This biotic process is carried out under aerobic conditions by the chemoautotrophs using NH\({}_{4}\)\({}^{+}\) as an energy source [31] and can ultimately produce N\({}_{2}\)O by several biochemical pathways [24; 30; 32]. Nitros oxide is one of the most concerning non-CO\({}_{2}\) greenhouse gas [33] due to its long atmospheric lifetime (114 years) and high capacity to absorb infrared radiation that can be returned as thermal energy (298 times higher than CO\({}_{2}\)) [34; 35]. Thus, N\({}_{2}\)O production and other related biogeochemical N-cycling are important pathways in mangrove forests. Land-use change in mangrove forests by anthropogenic activities and climate change effects (e.g., sea-level rise) substantially affects the biota and physicochemical characteristics of this important and complex marine/terrestrial/estuarine system [36; 37]. The impacts of land-use change and pollution in mangroves are severe and may eradicate mangrove fauna, which are fundamental for mangrove functioning [38; 39]. For instance, the lack of bioturbation promoted by crabs decreases soil aeration, enhancing anaerobic conditions [40], which are propitious for increasing the emissions of anaerobic pathways of N\({}_{2}\)O and methane (CH\({}_{4}\)), and potentially feeding back to mangroves with climate change effects. To our knowledge, there are no studies that have evaluated the effect of crab bioturbation on N\({}_{2}\)O emission in mangrove forests, and together, investigated the effects of the seasonal climatic conditions (rainy and dry seasons).