Source: Water Resources Research
Coastal aquaculture has grown rapidly over the past few decades, and although ocean-based food supplies have increased, concerns about the environmental impacts of aquaculture have as well. For example, research has found that shrimp aquaculture ponds pollute surface waters by releasing nutrient-rich waste into the ocean. Although researchers know that salt water from shrimp farms can seep into groundwater, the extent to which shrimp ponds affect subsurface salinization, groundwater quality, and groundwater composition is unclear.
In a new study, Hou et al. examined how shrimp farms’ water salinity, pond water depth, and farm width affect groundwater salinization and discharge. The researchers identified a saline plume in groundwater under a shrimp farm in Zhongshan, Guangdong Province, China, and monitored its salinity for 1 year. They also used numerical models to examine how shrimp pond characteristics and farm expansion affected groundwater salinization and submarine discharge along the coast over the past 30 years.
They found that from 1990 to 2020, the total area of aquaculture ponds doubled. In addition, the wider a farm was, the longer it took an aquifer to regain its freshness during the non-shrimp-growing season. For most farms, the 3-month nongrowing season was not enough time for aquifers to recover from salinization. As pond depth increased, so did the rate of fresh and saline submarine groundwater discharge.
According to the authors, these findings may help decisionmakers evaluate groundwater vulnerability and optimize shrimp farm layouts to help reduce aquifer salinization and improve coastal water quality. (Water Resources Research, https://doi.org/10.1029/2021WR031866, 2022)
—Aara’L Yarber (@yarber79), Science Writer