Azorean Vascular Plants with Potential Use in Constructed Wetlands with Horizontal Subsurface Flow

Constructed wetlands are considered integrated ecosystems and a promising wastewater treatment option, relying on vegetation, soils, and microbial assemblages. The potential dispersal of effluents from domestic septic systems, the application of dairy farm effluents containing excessive nutrients and pathogens into pastures, and undertreated effluent discharge in coastal areas are some of the threats to water quality in the Azores. Constructed wetlands could be used in the Azores to protect and preserve the quality of drinking water sources and bathing waters. However, the most used plant species in other regions are considered as introduced in the Azores, where a considerable number of invasive plants and weeds are already present. Here, we present a review of the plant taxa already present in the Azorean flora with the potential to be used in constructed wetland systems, based on a literature review, and on the assessment of nine criteria. We evaluated 73 taxa, including mostly Cyperaceae, Poaceae and Juncaceae, showing that, although some of the top-ranking species were considered potentially noxious, several native and some naturalized taxa could be used for wastewater treatment. This work supports the implementation of constructed wetlands in the Azores, while minimizing the risk of new invasions.