The Azorean Biodiversity Portal is a regional database that compiles georeferenced records of marine and terrestrial taxa from historical literature, collections and field observations. Field activities included site selection and fieldwork by Fernando Pereira and Rui B. Elias, following authorisation from the Azorean Regional Directorate for the Environment.

Rui B. Elias also conducted fieldwork and site selection. Andrea Petrone and Rui B.

Elias served as taxonomists, while Andrea Petrone and Paulo A. V. Borges were responsible for the Darwin Core databases.

These activities link field observations and taxonomic identification with standardised geospatial records for the regional database. The inventory was conducted on Pico, the second-largest of the nine volcanic islands in the Azores Archipelago. The archipelago lies in the North Atlantic at approximately 37–40° N and 25–31° W, about 1,600 km west of mainland Portugal.

Pico covers approximately 447 km², measures about 42 km from east to west and 15 km from north to south, and reaches 2,351 m above sea level at Mount Pico, the highest point in Portugal. Described as the youngest island in the archipelago, Pico has an age of approximately 0.27 million years. Pico’s volcanic and tectonic setting creates pronounced environmental gradients.

Its three principal volcanic units are the older Topo volcano, an intermediate volcanostratigraphic unit containing basaltic spatter cones, and the younger Madalena Volcanic Complex, which includes fissural systems and the Pico stratovolcano with its summit pit crater. Historical eruptions in 1562–64, 1718 and 1720 produced recent lava fields locally known as the “Misterios.” Young, poorly developed andisols predominate, while organic soils and peat occur in depressions and at higher elevations. Climate also varies markedly with altitude.

Mean annual temperature at sea level is approximately 17.4–17.5°C, with limited seasonal variation. Precipitation occurs throughout the year and increases from about 1,000–1,900 mm at low elevations to more than 4,000 mm above 700 m. Fog and cloud interception are important between roughly 180 and 700 m, average relative humidity is around 80%, and snowfall may occur above 2,000 m.

These climatic and topographic gradients shape the island’s sequence of coastal woodlands, lowland and montane forests, submontane forests, and alpine scrublands. Although human colonisation has substantially transformed Pico through forest clearance for agriculture and pasture, wood extraction and the introduction of alien species, the island retains some of the Azores’ best-preserved natural habitats. Its limited agricultural potential and low level of urbanisation have helped sustain large areas of natural and semi-natural vegetation.

The island preserves nearly the complete sequence of vegetation belts, from Erica–Morella coastal woodlands at 0–100 m to Calluna alpine scrublands above 1,700 m, creating substantial ecological heterogeneity. The principal reported contribution is improved spatial documentation of plant distributions on Pico. The occurrence dataset provides a more explicit record of where vascular plants have been observed and can support island biogeography, long-term ecological monitoring, conservation strategies and further studies of Azorean biodiversity.

This is a field-based inventory and dataset study rather than a comparative experiment, and it is geographically bounded to Pico Island, with an emphasis on exotic potentially invasive vascular plants in natural and semi-natural areas. The available project description does not report sampling effort or detection uncertainty, and the inventory does not establish trends in species richness, invasive-plant impacts or ecosystem condition.

Subject of Research: Georeferenced field inventory of vascular plants in natural and semi-natural areas of Pico Island, Azores

Article Title: New spatial records of vascular plants in the Azores Archipelago: the PRIBES project and the Azorean Biodiversity Portal (ABP) initiatives – II. Pico Island

Article References: Petrone, A., Borges, P., Pereira, F., & Elias, R. (2026). New spatial records of vascular plants in the Azores Archipelago: the PRIBES project and the Azorean Biodiversity Portal (ABP) initiatives – II. Pico Island. Biodiversity Data Journal, 14, Article e206276. https://doi.org/10.3897/bdj.14.e206276

Image Credits: AI Generated

DOI: 10.3897/BDJ.14.e206276

Keywords: Pico Island, Azores, vascular plants, biodiversity inventory, georeferenced records, PRIBES, Azorean Biodiversity Portal, plant distributions, spatial, records, vascular, plants

The Azores host just two confirmed extant bat species, both of them endemics with restricted ranges. The Azorean bat, Nyctalus azoreum, is found nowhere else in the world and has so far been confirmed on seven of the archipelago’s nine islands. The Madeiran pipistrelle, Pipistrellus maderensis, is a Macaronesian endemic that also occurs in Madeira and the Canary Islands. In the western group of the Azores, composed of Flores and the even smaller Corvo, only pipistrelle-type calls had ever been detected acoustically. But recent observations of bats flying during daylight hours on Flores, together with the recovery of a dead pipistrelle specimen, raised questions about what was really living on the island and prompted the new investigation.

The genetic half of the study rested on a single, poignant specimen. In August 2024, a nature conservation ranger recovered a dead bat at Fazenda on the northern coast of Flores. The dark brown adult, with a forearm measuring 32.4 millimetres, bore tears in its wing membranes and lower abdomen, and contextual evidence suggested it had likely been killed by a domestic cat. Researchers excised a three-millimetre puncture of wing tissue, stored it in ethanol, and extracted genomic DNA in the laboratory. They amplified a fragment of the mitochondrial cytochrome b gene by polymerase chain reaction and sequenced it commercially, producing an 814-base-pair sequence that was subsequently deposited in GenBank under accession number PZ699694.

The sequence told an unambiguous story. When compared against public databases, it showed its highest identity, 98.8 percent, with P. maderensis sequences from the Madeira archipelago. To place the Flores bat in a broader geographic context, the team built a median-joining haplotype network from 465 base pairs of cytochrome b, drawing on published sequences from Madeira, Porto Santo, the Canary Islands, and multiple populations of the related Kuhl’s pipistrelle from Europe, North Africa, and the Middle East, alongside Azorean N. azoreum sequences. The Flores specimen fell squarely within the P. maderensis cluster, most closely associated with haplotypes from Madeira and Porto Santo. Intriguingly, the Flores sequence represents a unique haplotype, separated by six mutational steps from the shared Madeira and Porto Santo group and ten steps from the nearest Canarian haplotype, a pattern that hints at either colonisation from the Madeira region or shared ancestry followed by local differentiation in the Azores.

This genetic confirmation carries real weight for Macaronesian biogeography. Although P. maderensis had previously been genetically identified on the Azorean island of Santa Maria, that sequence was never published in a public database, meaning the Flores specimen now constitutes the first publicly available genetic reference for the species in the Azores. Until now, pipistrelle records across most of the archipelago rested on acoustic detections alone, which cannot distinguish P. maderensis from morphologically similar relatives with complete certainty. The new sequence establishes a baseline for future studies of population structure, connectivity, and colonisation history across the scattered island groups of the region, where small founder populations can diverge rapidly in isolation.

The acoustic half of the study was equally revealing. Between 16 and 19 September 2024, the team deployed autonomous AudioMoth recorders at ten sites across Flores, mounted on tree trunks or poles about 1.8 metres above the ground. The devices sampled at 192 kilohertz in a cyclical pattern of four and a half minutes of recording followed by a thirty-second pause, running continuously over consecutive 24-hour periods. Persistent heavy rainfall caused two devices to malfunction, and two remote northwestern sites could not be reached by vehicle, but the remaining ten sites provided broad coverage of the island’s main habitat types. Out of 5,760 recordings, 296 files contained bat activity, yielding a total of 3,862 bat passes, each defined as at least two sequential recognisable echolocation pulses.

The species split within those passes was strikingly lopsided. Pipistrellus maderensis accounted for 99.6 percent of all recorded activity and was detected at every sampled site, confirming its status as the most widespread and acoustically active bat on Flores, with particularly high activity along the northern coast. Nyctalus azoreum, by contrast, contributed just 0.4 percent of passes and was detected only at a handful of sites in the central and southern parts of the island. The two species can be reliably separated acoustically because their echolocation calls occupy similar but non-overlapping frequency ranges: N. azoreum calls peak at around 32.1 kilohertz, while Pipistrellus calls peak at about 45.3 kilohertz. The detection of the Azorean bat at sites that had been surveyed before suggests that earlier non-detections reflected low detectability and lower sampling effort rather than true absence, since previous surveys relied on short-duration hand-held detectors rather than recorders running for days at a time.

Activity patterns followed a strictly nocturnal rhythm. Every call was recorded between sunset at 20:06 and sunrise at 07:47 local time, with no daytime activity detected during the study period, despite N. azoreum being known elsewhere in the archipelago to forage in daylight. Both species remained active throughout the night, tapering off in the hours before dawn. The earliest P. maderensis call came at 20:07 and the latest at 07:30, while N. azoreum activity spanned from 20:23 to 05:40. To test whether the bats favoured particular environments, the researchers classified sites as stream or urban habitats and fitted a negative binomial generalised linear mixed model with the number of passes per night as the response. The effect of species on activity was only marginal, and neither habitat nor the species-by-habitat interaction was statistically significant, suggesting that both species use a range of environments on the island, although the very low number of Azorean bat detections limits any firm conclusions about its habitat preferences.

The findings matter well beyond Flores. Island bat populations are typically small, isolated, and vulnerable to habitat alteration, invasive species, and stochastic events, and previous work has shown substantial genetic structuring among N. azoreum populations, with haplotypes often restricted to individual islands and limited inter-island gene flow. That pattern implies the small Flores population may have little connection to bats elsewhere in the archipelago, raising questions about its long-term viability and the mechanisms that allow it to coexist with the far more abundant pipistrelle. The authors argue that continued monitoring is essential, and they recommend reassessing the occurrence of N. azoreum on neighbouring Corvo using passive acoustic recording, since earlier hand-held surveys there may likewise have missed a rare species. Surveys on São Miguel, Terceira, and Faial, where P. maderensis has not yet been confirmed, could also clarify the pipistrelle’s full distribution.

There is also a sobering conservation note embedded in the data. The only P. maderensis specimen collected during the study was likely predated by a domestic cat, a vivid illustration of the threat that introduced predators pose to island bats worldwide. Cats are increasingly recognised as significant predators of bats on oceanic islands, where native species evolved without such hunters and often roost or forage in accessible places. Combined with the apparent rarity of the Azorean bat on Flores and the vulnerability that comes with small population size, the study underscores a broader lesson: even in a well-studied European archipelago, remote islands can still hide species that only modern, patient, and integrated methods, listening to the night and reading the DNA of a single recovered wing, can bring to light.

Subject of Research: Distribution and conservation of bat species on Flores Island in the Azores, assessed through genetic and bioacoustic monitoring

Article Title: Bats of a remote island: integrated genetic and bioacoustics monitoring confirms species occurrence in Flores (Azores, Portugal)

Article References: Rainho, A., Estácio, C. S., Silva, C. G., & Gabriel, S. I. (2026). Bats of a remote island: integrated genetic and bioacoustics monitoring confirms species occurrence in Flores (Azores, Portugal). Web Ecology, 26(2), 193-202. https://doi.org/10.5194/we-26-193-2026

Image Credits: AI Generated

DOI: 10.5194/we-26-193-2026

Keywords: Azores, Flores Island, bats, Nyctalus azoreum, Pipistrellus maderensis, bioacoustics, mitochondrial DNA, island biogeography, conservation, endemic species, haplotype network, invasive predators

The choice of study site was deliberate. Volcanic lakes are usually treated as special cases in greenhouse gas budgets because they can receive magmatic and hydrothermal carbon from below, potentially inflating their emissions far above those of ordinary lakes. The Azores, with active volcanism and widespread hydrothermal manifestations, is an ideal place to test how much of a lake’s carbon output is geological and how much is biological. Previous work across the archipelago estimated that 45 Azorean lakes together emit roughly 171,000 tonnes of carbon dioxide per year, of which about 42 percent was attributed to volcanic origin. But the Flores lakes had only been measured once before, leaving large uncertainties, and their methane emissions had never been quantified at all.

The three lakes differ dramatically despite sitting within a few kilometers of each other inside the Seven Lakes Caldera. Comprida is the smallest and shallowest, just 14.3 meters deep with a surface area of 0.06 square kilometers, occupying an elongated maar formed by a row of at least five craters during a single eruption dated to 3,180 calibrated years before present. Negra, formed in the same eruption, is the deepest lake in the entire Azores at 119 meters, with water that can linger for 17 years before being flushed out. Funda, the largest at 0.38 square kilometers, lies in a steep-walled maar created by a phreatomagmatic eruption around 3,250 years ago and drains a watershed more than eight times its own surface area. These differences in depth, volume and residence time turned out to matter enormously for how the lakes behave chemically and biologically.

The team conducted four field surveys between May 2023 and February 2024, capturing the full seasonal cycle of these monomictic lakes, which stratify thermally in summer and mix completely in winter. They measured diffuse carbon dioxide flux using a static floating chamber equipped with an infrared detector, mapping the lake surfaces point by point, and applied both the Graphical Statistical Approach and sequential Gaussian simulation to convert those measurements into total lake-wide emission estimates. For methane, they deployed floating chambers along transects during the November and February surveys and also calculated theoretical fluxes from dissolved gas concentrations using a thin boundary layer model, finding the two methods agreed closely. Water chemistry was profiled at depth intervals in every lake, and sediment cores were collected for microbial analysis using full-length 16S rRNA gene sequencing on a PacBio platform.

The headline numbers show that carbon dioxide dominates these systems by two to three orders of magnitude over methane. Funda Lake emerged as the strongest emitter, releasing about 1.06 tonnes of carbon dioxide per day during the first survey and 1.02 tonnes during the second, while Comprida and Negra released at most around 0.39 and 0.22 tonnes per day respectively. Yet crucially, none of the measured fluxes came close to the threshold of 35 grams per square meter per day above which a magmatic contribution cannot be excluded. Carbon isotope data reinforced this conclusion: the delta-13C values of dissolved inorganic carbon in all three lakes were more negative than both the atmospheric and mantle signatures, pointing to a biogenic origin for the escaping carbon dioxide rather than a deep volcanic source.

Seasonality left a clear fingerprint on the emissions. Carbon dioxide fluxes were consistently lower during the August survey than in May, a counterintuitive result the researchers attribute to warmer surface waters boosting photosynthetic activity, which strips dissolved carbon dioxide from the water before it can escape. In eutrophic lakes this effect can be strong enough to push surface waters below atmospheric equilibrium, turning them into temporary carbon dioxide sinks. Methane behaved differently: fluxes were two to three times higher during the November survey, when Negra and Funda were still stratified and bottom waters were warm, than in February after full mixing. Warmer sediments favor methane-producing archaea, so the stratified autumn conditions gave methanogenesis a head start that winter mixing then erased.

The microbial data provide the mechanistic explanation for these patterns. In summer, Negra Lake was dominated by autotrophic Nostocaceae, cyanobacteria that fix carbon dioxide through photosynthesis, consistent with its relatively low surface fluxes. Meanwhile Comprida and Funda harbored abundant fermentative taxa such as Clostridiaceae and Enterobacteriaceae, which break down organic matter anaerobically and release carbon dioxide in deeper sediments. When winter mixing broke down the stratification in Negra and Funda, the microbial balance shifted sharply: fermenters, sulfate-reducing Desulfatiglandaceae and syntrophic Syntrophaceae all surged, indicating intensified anaerobic respiration and a potential pulse of carbon dioxide from sediments that had been accumulating organic matter under oxygen-poor conditions.

Methane cycling followed its own microbial logic. In Funda Lake, syntrophic families that feed methanogens, including Smithellaceae, Syntrophaceae and Syntrophorhabdaceae, were already well established during summer stratification and grew further in winter, but so did Methylomonadaceae, aerobic bacteria that oxidize methane. The researchers suggest that winter mixing oxygenates deeper water, giving methanotrophs the oxygen they need to consume methane before it reaches the surface, which helps explain the lower winter fluxes. Comprida Lake told a different story: syntrophic groups were scarce, but methane-oxidizing Methylococcaceae and Methylomonadaceae exploded in winter, suggesting that in this less productive lake, biological oxidation is the dominant brake on methane escape. In deep Negra Lake, by contrast, methanotrophs declined in winter, possibly because even full mixing could not deliver enough oxygen to the lake’s great depths, allowing methane to accumulate.

Trophic status emerged as a unifying theme. Negra and Funda are classified as being in poor and bad ecological status respectively under the EU Water Framework Directive, with chlorophyll-a values reaching 45 and 86.4 micrograms per liter, while Comprida remains in good status with far lower productivity. The eutrophic lakes support larger microbial communities engaged in anaerobic degradation, which translates into higher greenhouse gas production. The study’s total emission estimates reflect this: when the lakes were stratified, Funda released about 1.23 tonnes of carbon dioxide equivalent per day, compared with 0.33 and 0.23 tonnes for Comprida and Negra. Methane emissions, ranging from 0.64 to 6.28 kilograms per day across the lakes, remained below global averages for lakes of comparable size, but the authors warn that ongoing eutrophication, potentially worsened by climate-driven increases in nutrient runoff, could push these numbers upward.

The broader message is that volcanic setting alone does not make a lake a carbon hotspot. In Flores’s maar lakes, the geology provides the basin, but the biology writes the emissions budget. Microbial communities act as dynamic regulators, mediating the balance between carbon fixation and respiration, between methanogenesis and methane oxidation, and shifting that balance with every seasonal turn of the water column. As climate change alters stratification patterns and nutrient loading in lakes worldwide, the authors argue that integrating microbial functional profiles into biogeochemical assessments will be essential for predicting how these small but numerous ecosystems will feed back on the global carbon cycle.

Subject of Research: Carbon dioxide and methane fluxes and their microbial controls in monomictic volcanic crater lakes on Flores Island, Azores

Article Title: CO2 and CH4 fluxes from monomictic volcanic lakes in a remote oceanic island: Flores island case study (Azores)

Article References: Ferreira, L., Andrade, C., Cruz, J. V., Tassi, F., Pimentel, A., Braga, D., Frias, J., Raposeiro, P., & Toubarro, D. (2026). CO2 and CH4 fluxes from monomictic volcanic lakes in a remote oceanic island: Flores island case study (Azores). Environmental Earth Sciences, 85(16), Article 417. https://doi.org/10.1007/s12665-026-13139-1

Image Credits: AI Generated

DOI: 10.1007/s12665-026-13139-1

Keywords: volcanic lakes, greenhouse gases, carbon dioxide flux, methane emissions, Azores, Flores Island, maar lakes, microbial communities, eutrophication, biogeochemistry, lake stratification, methanotrophs