Cyanobacteria from freshwater lakes in the Azores archipelago, Portugal: data from long term phytoplankton monitoring

Abstract

The Azores are oceanic islands located in the Northern Atlantic Ocean and are particularly rich in aquatic systems, ranging from freshwater, brackish, marine and thermal habitats. Due to the increase in local anthropogenic pressures and global warming, several azorean lakes began to reveal signs of eutrophication that led to the implementation of monitoring programmes and management strategies on the most impacted lakes. Later, the Water Framework Directive (2000/60/EC) demanded the establishment of biomonitoring programmes for European freshwater ecosystems and the limited Azorean monitoring programmes were extended to a larger set of lakes. Since the establishment of the aquatic systems monitoring programme in the Azores archipelago, lakes have been regularly sampled, producing innumerous unpublished records of cyanobacteria that are difficult to access. Here we present the occurrences of cyanobacteria in Azorean lakes that result from 22 years of phytoplankton monitoring in a total of 1948 cyanobacteria occurrences from 968 phytoplankton sampling events on Azorean lakes done between 1996 and 2018 as part of regional inland aquatic ecosystems monitoring programmes. Forty two cyanobacteria taxa were identified in those events, 28 species and 14 at genus level. This information is crucial for conservation, biodiversity studies and lake management, as some of the cyanobacteria species present are bloom-forming and have the ability to produce toxins. This will also allow for the identification of invasive species and possible targeted control and mitigation programmes, according to the species present in the Azorean lakes.

Cyanobacteria Phylogenetic Studies Reveal Evidence for Polyphyletic Genera from Thermal and Freshwater Habitats

“…Water temperature varied between 12-23 • C in lakes, 14-15 • C in streams, and from 28 • C to over 100 • C in thermal sites. Lake water pH varied from slightly acid to alkaline (6)(7)(8)(9), while in streams it was mainly neutral (around 7), and more acidic in thermal sites (5.9-6.9). Dissolved oxygen was similar in lakes and streams (9-12 mg L −1 ), however lower in thermal sites (2-6 mg L −1 ), while electric conductivity was higher in thermal sites (477-2440 µS cm −1 ), and streams (93-380 µS cm −1 ), and lower in lakes (30-148 µS cm −1 ).…”

“…In the Azores, a remote Atlantic Ocean archipelago of volcanic origin, the study of cyanobacteria on different types of ecosystems is also biased. Although cyanobacteria have been reported in these islands since 1874 [5,6], most reports are from freshwater lakes (e.g., [5,[7][8][9]), due to high abundance of these ecosystems (88) [10] and to the occurrence of cyanobacteria blooms associated with lake cultural eutrophication [8,11]. Despite the abundance of thermal sites [12] and other environments suitable for cyanobacteria inhabitance [13], only a few studies on cyanobacteria diversity in these habitats were done [9,13].…”

“…Despite the abundance of thermal sites [12] and other environments suitable for cyanobacteria inhabitance [13], only a few studies on cyanobacteria diversity in these habitats were done [9,13]. In fact, a recent work by Luz et al [6] gathers almost 2.000 cyanobacteria occurrences (42 different taxa) only from freshwater lakes.…”

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

“…In general, invasions by microorganisms are poorly understood and, until recently, their impact on the environment has been underestimated (Foissner and Hawksworth, 2009;Kaštovský et al, 2010).Many species of cyanobacteria can produce toxins harmful to the ecosystem, and when present in drinking or recreational waters might lead to human health problems (Christoffersen and Kaas, 2000;Funari and Testai, 2008;Oscoz et al, 2010) that can vary from psychological effects, discomfort, nuisance, and phobias, to skin irritations, allergies, poisoning, disease and even death (Bayliss et al, 2017;Peyton et al, 2019). Examples of the latter can be posed by the invasive species Microcystis aeruginosa (Kützing) Kützing, Microcystis flosaquae (Wittrock) Kirchner, Aphanizomenon flos-aquae Ralfs ex Bornet & Flahault, Aphanizomenon gracile Lemmermann and Dolichospermum scheremetieviae (Elenkin) Wacklin, L. Hoffmann & Komárek, found in many lakes in the archipelago, often with high abundance (Santos et al, 2005;Cordeiro et al, 2020;Luz et al, 2020).…”

Distribution of Toxic Cyanobacteria in Volcanic Lakes of the Azores Islands

“…References to the presence of cyanobacteria in the Azores date back to the late Nineteenth century [37][38][39], but the current knowledge on their distribution and ecology is still limited [35,36], and even less is known about the presence of toxigenic strains in the Azorean lakes [7,30,40,41]. Considering that several species known from the literature as producers of MC, STX, ATX-a, and CYN, such as Aphanizomenon gracile [42], Microcystis aeruginosa [43], and Raphidiopsis curvata [44], were found in the Azores lakes [45], the presence of toxigenic strains and/or cyanotoxins should be further investigated, in order to determine the present risk in these waters.…”