Non-indigenous and Invasive Freshwater Species on the Atlantic Islands of the Azores Archipelago

Abstract

Freshwater systems on remote oceanic islands are particularly vulnerable to biological invasions. The case of freshwater ecosystems in the Azores Archipelago is especially relevant considering the islands’ youth and remoteness, and low natural connectivity. This study presents a review of the introduction and presence of non-indigenous freshwater species in the Azores, retrieved from various historical records, paleoenvironmental reconstructions, published records, and field data from two decades of the Water Framework Directive (WFD) monitoring programs. At least 132 non-indigenous freshwater species have successfully established in the Azores, belonging to several taxonomic groups: cyanobacteria (10), synurophytes (1), desmids (1), diatoms (20), plants (41), invertebrates (45), amphibia (2), and fishes (12). Intentional and accidental introductions have been occurring since the establishment of the first human settlers on the archipelago, impacting freshwater ecosystems. The first reported introductions in the Azores were intentional fish stocking in some lakes. Non-deliberate introductions have recently increased through transport-contaminants (51%) associated with the aquarium trade or agricultural products. In the Azores, the highest number of non-indigenous species occur on the largest and most populated island, São Miguel Island (116), followed by Flores (68). Plants constitute the most representative group of introduced species on all islands, but invertebrates, diatoms, and fishes are also well established on most islands. Among invertebrates, non-indigenous arthropods are the most well-established group on all islands except on the smallest Corvo Island. Many non-indigenous species will likely benefit from climate change and magnified by globalization that increases the probability of the movement of tropical and subtropical species to the Azores. Present trends in international trade, importations, and enhanced connectivity of the archipelago by increasing flights and shipping will probably promote the arrival of new species. Augmented connectivity among islands is likely to improve non-indigenous species dispersal within the archipelago as accidental transportation seems to be an essential pathway for non-indigenous freshwater species already present in the Azores.

Checklist of Basidiomycota and New Records from the Azores Archipelago

“…The introduction of agricultural species and adventitious vascular plants from different geographical origins constitute a major impact on the native flora of the Azores [146]. Many of these endemic plant communities have experienced regression or irretrievable alterations as a result [147].…”

Synergistic Effects of Climate Change and Alien Fish Invasions in Freshwater Ecosystems: A Review

“…Also, Souza et al [47], on the basis of observational data, have demonstrated the distribution range expansion of C. carpio in the European lakes where it has been introduced, favored by the rising temperatures, which promote the reproductive success of the species and the establishment of self-sustaining populations; also, in this case, the species benefited from restocking activities. C. carpio is also the most abundant invasive species in the Azorean lakes, where the species produces detrimental ecological effects in terms of rising water turbidity and releasing of nutrients from sediments, due to the above-mentioned bottomfeeding behavior; all these effects will likely be enhanced by climate changes, thanks to the high ecological traits plasticity, which renders the species able to cope with changing environmental conditions [56].…”

Searching for the critically endangered European eel in oceanic islands: A pioneer study in the freshwater systems of Madeira, Macaronesia

“…Due to escalating anthropogenic pressures, freshwater systems stand out as the most threatened on a global scale (Dudgeon et al, 2006; Maasri et al, 2022; Tickner et al, 2020). Insular freshwater ecosystems – often species‐poor and geographically isolated – are particularly sensitive, and the knowledge of their ecology and conservation needs typically lags that of mainland (Costa et al, 2021; Dudgeon, 2019; Tickner et al, 2020). This is particularly worrisome as islands cover approximately 5% of the Earth's surface but are home to around 20% of the planet's biodiversity and often act as refuges for species that have disappeared elsewhere (Conenna et al, 2017; Fernández‐Palacios et al, 2021).…”