Large Fine‐Scale Spatiotemporal Variations of CH₄ Diffusive Fluxes From Shrimp Aquaculture Ponds Affected by Organic Matter Supply and Aeration in Southeast China

Abstract

Mariculture shrimp ponds are important CH4 sources to the atmosphere. However, the spatiotemporal variations of CH4 concentration and flux at fine spatial scales in mariculture ponds are poorly known, particularly in China, worlds largest aquaculture producer. In this study, the plot‐scale spatiotemporal variations of water CH4 concentration and flux, both within and among ponds, were researched in shrimp ponds in Shanyutan wetland, Min River Estuary, Southeast China. The average water CH4 concentration and diffusion flux across the water‐air interface in the shrimp ponds over the shrimp aquaculture period varied from 2.29 ± 0.29 to 50.48 ± 20.91 μM and from 0.09 ± 0.01 to 2.32 ± 0.95 mmol·m−2·hr−1, respectively. The CH4 emissions from the estuarine ponds varied greatly between seasons, with peaks in August and September, which was similar to the trend of water temperature and dissolved oxygen concentrations. There was no remarkable difference in CH4 concentration and flux between shrimp ponds but significantly spatiotemporal differences in CH4 concentration and flux within the ponds. Significantly higher emissions occurred in the feeding zone, accounting for approximately 60% of total CH4 emission flux, while much lower CH4 emissions appeared in aeration zone, contributing 14% to total flux. This study suggests the importance of considering spatiotemporal variation in the whole‐pond estimates of CH4 concentration and flux. In light of such high spatial variation within ponds, improving aeration and feed utilization efficiency would help to mitigate CH4 emissions from mariculture ponds.

Spatial Variations of N2O Fluxes Across the Water‐Air Interface of Mariculture Ponds in a Subtropical Estuary in Southeast China

“…Our field measurements were conducted in the mariculture ponds in the Shanyutan wetland in the Min River Estuary in southeast China (Figure 1; P. Yang et al, 2019), which covered a total area of approximately 234 ha (P. Yang, Lai, et al, 2017). The study area was influenced by a subtropical monsoonal climate, with annual mean temperature and precipitation of 19.60°C and 1,350 mm, respectively (Tong et al, 2010).…”

“…According to the spatial variations of microtopographic features, water depth, and management practices, the shrimp ponds were divided into three different zones, namely, Zone N, which was a nearshore area with sparse submerged vegetation, Zone F, which was a deepwater area used for feeding, and Zone A, which was a shallow‐water area subjected to aeration activities (Figure 1c). Please refer to Zhang et al (2019) and P. Yang et al (2019) for more details about the overall setup and the three spatial zones of these shrimp ponds. Details about the management practices in these shrimp ponds can be found in P. Yang, Lai, et al (2017) and P. Yang et al (2018).…”

“…(a) Location of the study area at Shanyutan Wetland of Min River Estuary, Southeast China, (b) a photo showing one of the studied ponds, and (c) a diagram showing the locations of sampling sites (red dots) within the pond. Zones N, F, and A are nearshore, feeding, and aeration areas, respectively (modified after P. Yang et al, 2019). …”

“…Mariculture shrimp ponds are generally semiartificial ecosystems that are heavily managed by practices such as stocking, feeding, harvesting, and aeration (Chen et al, 2016; P. Yang et al, 2018). These ponds are inherently heterogeneous over multiple spatiotemporal scales as a result of differences in topographic features, environmental conditions, and management actions (P. Yang et al, 2019). However, the fine‐scale spatial variations of N 2 O fluxes both within and between ponds and their temporal changes remain poorly characterized.…”

Spatial Variation in Aragonite Saturation State and the Influencing Factors in Jiaozhou Bay, China

“…Ocean acidification (OA) not only causes physical and chemical changes in the ocean but is also of widespread concern due to its serious impact on marine ecosystems and calcifying organisms [1][2][3][4]. Coastal waters are the most active areas for fishery production and shellfish farming, and studies related to OA mechanisms are a top priority in the region [5][6][7]. Unlike the open ocean, nearshore acidification is not only affected by global OA caused by increasing atmospheric CO 2 levels but also by the coupled effects of various processes, such as upwelling, organic matter degradation, primary production of phytoplankton and river input, due to the strong interaction between land and ocean, making the acidification mechanism in coastal waters more complicated [8][9][10][11].…”