Reprint of 'Seagrasses in Portugal: a most endangered marine habitat'. (Special Issue: Mediterranean seagrasses - from genes to seascapes.)

摘要

Numerous reports of seagrass decline around the world indicate that seagrass habitats are undergoing a global crisis with important consequences for coastal biodiversity, environmental status and economy, reflecting their vulnerable and overlooked status within many conservation agendas. This paper describes the results of the first extensive survey of this habitat in Portugal. It shows the present cover distribution and declining trends of seagrasses on the Portuguese coast (1980-2010), identifies environmental and conservation issues, and discusses challenges for long-term survival. Seagrass populations of the Portuguese coast are also facing an unprecedented decline in distribution, matching the general trends described for most world seagrasses. The results of this investigation show a dramatic decrease of seagrass cover in Portugal in the last 20 years. This decrease followed different trends for the three species present on this coast. Zostera noltii, having disappeared from some systems by almost 75%, is still the most abundant species, present in 10 of the 18 sites assessed. Zostera marina is presently the most endangered seagrass species in Portugal, as it disappeared from six of eight historical locations and faces extinction from the Portuguese territory if measures are not taken to assure the protection of the last regions left with populations. Cymodocea nodosa has a geographic distribution range limited to the southern/southwestern coasts, and its current conservation status is uncertain, although there is evidence for the recent occurrence of several population bottlenecks. Management questions are discussed and actions to improve habitat conservation are suggested.