Distribution of Toxic Cyanobacteria in Volcanic Lakes of the Azores Islands

Abstract

Eutrophication and global climate change gather advantageous conditions for cyanobacteria proliferation leading to bloom formation and cyanotoxin production. In the Azores, eutrophication is a major concern, mainly in lakes where fertilizers and organic matter discharges have increased nutrient concentration. In this study, we focused on understanding the influence of environmental factors and lake characteristics on (i) cyanobacteria diversity and biomass and (ii) the presence of toxic strains and microcystin, saxitoxin, anatoxin-a, and cylindrospermopsin cyanotoxin-producing genes. Fifteen lakes from the Azores Archipelago were sampled seasonally, environmental variables were recorded in situ, cyanobacteria were analyzed with microscopic techniques, and cyanotoxin-producing genes were targeted through conventional PCR. Statistical analysis (DistLM) showed that lake typology-associated variables (lake’s depth, area, and altitude) were the most explanatory variables of cyanobacteria biomass and cyanotoxin-producing genes presence, although trophic variables (chlorophyll a and total phosphorus) influence species distribution in each lake type. Our main results revealed higher cyanobacteria biomass/diversity, and higher toxicity risk in lakes located at lower altitudes, associated with deep anthropogenic pressures and eutrophication scenarios. These results emphasize the need for cyanobacteria blooms control measures, mainly by decreasing anthropogenic pressures surrounding these lakes, thus decreasing eutrophication. We also highlight the potential for microcystin, saxitoxin, and anatoxin-a production in these lakes, hence the necessity to implement continuous mitigation protocols to avoid environmental and public health toxicity events.

Distribution and diversity of cyanobacteria in the Azores Archipelago: An annotated checklist

“…The absence of some orders, such as the Chroococcidiopsidales and Thermostichales , in the Azores and the other Macaronesia Archipelagos, suggests that they probably have a more restricted geographic distribution. Although biological, geographical and climatic factors may contribute to cyanobacteria regional species richness ( Moreira et al 2013 , Walter et al 2017 , Ribeiro et al 2018 ), the differences amongst islands are most probably related to different sampling efforts ( Cordeiro et al 2020b ) and, between Azorean Islands, the distribution of planktic cyanobacteria seems to be mainly related to lake typology rather than environmental parameters ( Cordeiro et al 2020c ). For instance, the reduced richness of Oscillatoriales in the Azores could be related to their preference for terrestrial and benthic habitats that are less studied in this Archipelago.…”

Early detection and the importance of environmental drivers for the invasive cyanobacterium Raphidiopsis raciborskii

“…This finding is not surprising as lowland areas generally have milder climates. Furthermore, lowland lakes are often situated in catchments that are affected by land use such as agricultural and urbanization, resulting in elevated nutrients that favor cyanobacterial blooms (Cordeiro et al, 2020). By complementing climatic variables with information on the nutrient status of Swedish lakes, we were able to identify areas of high risk for invasion success.…”

The vanishing and the establishment of a new ecosystem on an oceanic island – Anthropogenic impacts with no return ticket

“…The δ 15 N was used as an indicator of in-lake dynamics variability. A rise of nutrients (mainly phosphorus) availability increase lake trophic status and N 2fixing cyanobacteria blooms in Azorean lakes (Cordeiro et al, 2020;Santos et al, 2005) and elsewhere (Taranu et al, 2015), resulting in a lower isotopic signal (Struck et al, 2000). Internal-lake P recycling in dimictic and monomictic lakes, as Lake Funda, is related to the hypolimnetic oxygen depletion during summer stratification, leading to a sharp increase in P and ammonia during the overturn period (Cruz et al, 2015;Richter et al, submitted).…”