Gomes, AnaCamacho, Sarita2020-06-152020-06-152017-08978-989-8859-18-1http://hdl.handle.net/10400.1/14008The Guadiana River estuary is the most important estuarine system in southern Portugal. The estuary’s variety of habitats supports a great diversity of species. Some of these species have only recently been discovered and are found nowhere else on Earth. This chapter details the current state of knowledge of the estuary’s habitats, with a particular focus on the unseen microscopic flora and fauna that support the entire food chain – and many economic activities – in the estuary.engbook part