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

Abstract

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 Ucides cordatus 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’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 (µg m−2 h−1) were 47.3 ± 9.7 and 8.9 ± 0.5 for the crab-exclusion sites, and 36.5 ± 7.8 and 4.5 ± 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.

Seasonal Response of Crab Disturbance to nitrogen at the Sediment-Water Interface in coastal tidal wetlands

“…Kristensen and Kostka 2005). This "biological irrigation" can accelerate deep pore water transportation and sedimentation(Mermillod- Blondin et al 2004), which promote the release or absorption of nutrients from the sediment to the overlying water.Crab activities could directly promote the porosity of the sediments, leading to a relatively aerobic microenvironment(Otero et al 2020). Moreover, the present data indicated that the presence of crab burrows could alleviate nitri cation inhibition caused by the alternating tidal uctuations.…”

How Do Plants and Climatic Conditions Control Soil Properties in Hypersaline Tidal Flats?

“…Thus, the selective use of NH 4 + , instead of NO 3 − , by the studied species can ameliorate water use-efficiency and mitigate the negative effects of hypersaline conditions. Together with plant activity and exudates, microbial communities are also greatly important for the biogeochemical cycling of N and other elements in humid coastal areas [21,26,63]. Microbial communities in HTF are predominantly halotolerant to halophilic microorganisms that may vary along the tidal flat in biodiversity, structure, and richness, as well as in association with different plants [64].…”

“…In fact, rain and drought events regulated by seasonal changes strongly influence the edaphic components of coastal ecosystems soils and, as a consequence, several ecological processes and ecosystem services [25][26][27]. Semiarid seasonal precipitation induces changes in pH, organic matter content, and nutrient bioavailability for plants in hypersaline environments [1,28].…”

Impact of Human Disturbance on Fiddler Crab (<i>Uca tangeri</i>) Burrow Morphology, Distribution and Chemistry at Eagle Island, Niger Delta, Nigeria

“…This is because there is a local belief that the waving of the right pincer signals the approaching of tidal current. Fiddler crabs perform other vital functions within the coastal environment, for instance they help recycle nutrient and energy in mangrove forest [1] [2]. By their filter feeding habit, they also consume microphytobenthos and plant litter from substrates [3].…”