Subterranean Fishes of the World

6325

2022

Freshwater Biology

2007-2023

67

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited

1. Coastal aquifers are vital water sources for humanity. Their quality and the ecosystem services they provide depend on the integrity of their subterranean biota. However, current anthropogenic impacts such as climate change effects and coastal population growth place enormous pressure on the sustainability of these environments. 2. Despite the significance of subterranean biota to ecosystem function and the delivery of ecosystem services, stygofauna—groundwater- dwelling aquatic animals—have until recently been largely ignored in aquifer monitoring and management. This issue is of importance in both coastal and inland zones. Common threats in inland and coastal areas are water extraction, reduced recharge caused by aridification, and pollution, while, in coastal zones, additional complications arise from sea-level change and salt water ingress. 3. This review examines stygofaunal diversity, impacts, and future conservation challenges in coastal aquifers. Focussing on Australia, we provide a summary of the available data on stygofaunal communities and distributions; identify and describe potential threats to these communities across the diverse coastal regions of the continent; and propose future research priorities with the goal of facilitating the long-term preservation of these ecosystems on the Australian continent. While we focus this review on Australia, the threats and management issues discussed are relevant globally. 4. Recent subterranean studies in Australia have been primarily undertaken in inland areas, and while coastal data exist, ecological assessment of coastal subterranean ecosystems is incomplete, compromising the efficacy of conservation plans. This review indicates that the Australian continent hosts five major coastal stygofaunal biodiversity areas characterised by heterogeneous community assemblages, involving a total of 17 taxonomic groups spanning microscopic aquatic invertebrates to vertebrates. The most relevant impacts and threats identified were aquifer size reduction, intrusion of seawater, land clearing, contamination, and mining. 5. Given the projections of increasing coastal development and subsequent loss or degradation of habitat during coming decades, it is important to improve our limited understanding of the ecology of coastal aquifers. Future research should include the refinement of biological assessment tools for coastal systems, functional and ecotoxicological studies, and faunal surveys of urban coastal aquifers. The recommendations and guidelines outlined in this review are applicable globally and provide a further step toward the sustainable use of coastal groundwater resources and the maintenance of healthy groundwater ecosystems. K E Y W O R D S aquifer, conservation, groundwater ecology, management, stygobiont

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