Fungal community composition in the gut of rove beetles (Coleoptera: Staphylinidae) from the Canadian boreal forest reveals possible endosymbiotic interactions for dietary needs

The goal of this study was to investigate the fungal community composition in the gut of Staphylinidae from boreal forest in order to better understand the diversity and the complexity of fungus-insect relationships. DNA gut content analyses of nine abundant rove beetle species (Coleoptera, Staphylinidae) living in the boreal balsam fir forest ecosystem (Montmorency Forest, Quebec, Canada) were performed to identify the fungal taxa present either as endosymbiotic taxa or as a source of nutrition. A total of 42 fungal operational taxonomic units (OTUs) were recorded from the analysis of 441 fungal ITS rDNA sequences recovered from gut extracts. The OTU richness per species ranged between four in Tachinus quebecensis and 16 in Atheta ventricosa. The fungal mycobiota in posterior gut extracts was dominated by Saccharomycetales (12 OTUs), followed by Sordariomycetes (nine OTUs). No significant difference was observed between the OTU richness recorded within each of the three subfamilies of rove beetles investigated. The core mycobiome of the posterior gut extracts was dominated by three OTUs related to yeasts, with ITS sequences having pairwise similarities equal to or greater than 99% with Candida mesenterica, Debaryomyces spp. and Ophiostoma pluriannulatum. These results provide some evidence of the consumer-resource relationships of these beetles. Predominance of yeast and fungal spores in the posterior gut of rove beetles suggests that they may play an important role in their dietary requirements and as endosymbionts.     

Variation in Carbon Storage and Its Distribution by Stand Age and Forest Type in Boreal and Temperate Forests in Northeastern China

The northeastern forest region of China is an important component of total temperate and boreal forests in the northern hemisphere. But how carbon (C) pool size and distribution varies among tree, understory, forest floor and soil components, and across stand ages remains unclear. To address this knowledge gap, we selected three major temperate and two major boreal forest types in northeastern (NE) China. Within both forest zones, we focused on four stand age classes (young, mid-aged, mature and over-mature). Results showed that total C storage was greater in temperate than in boreal forests, and greater in older than in younger stands. Tree biomass C was the main C component, and its contribution to the total forest C storage increased with increasing stand age. It ranged from 27.7% in young to 62.8% in over-mature stands in boreal forests and from 26.5% in young to 72.8% in over-mature stands in temperate forests. Results from both forest zones thus confirm the large biomass C storage capacity of old-growth forests. Tree biomass C was influenced by forest zone, stand age, and forest type. Soil C contribution to total forest C storage ranged from 62.5% in young to 30.1% in over-mature stands in boreal and from 70.1% in young to 26.0% in over-mature in temperate forests. Thus soil C storage is a major C pool in forests of NE China. On the other hand, understory and forest floor C jointly contained less than 13% and <5%, in boreal and temperate forests respectively, and thus play a minor role in total forest C storage in NE China.     

Forest microsite effects on community composition of ectomycorrhizal fungi on seedlings of Picea abies and Betula pendula

Niche differentiation in soil horizons, host species and natural nutrient gradients contribute to the high diversity of ectomycorrhizal fungi in boreal forests. This study aims at documenting the diversity and community composition of ectomycorrhizal fungi of Norway spruce ( Picea abies ) and silver birch ( Betula pendula ) seedlings in five most abundant microsites in three Estonian old-growth forests. Undisturbed forest floor, windthrow mounds and pits harboured more species than brown- and white-rotted wood. Several species of ectomycorrhizal fungi were differentially represented on either hosts, microsites and sites. Generally, the most frequent species in dead wood were also common in forest floor soil. Ordination analyses suggested that decay type determined the composition of EcM fungal community in dead wood. Root connections with in-growing mature tree roots from below affected the occurrence of certain fungal species on seedling roots systems in dead wood. This study demonstrates that ectomycorrhizal fungi differentially establish in certain forest microsites that is attributable to their dispersal and competitive abilities. Elevated microsites, especially decayed wood, act as seed beds for both ectomycorrhizal forest trees and fungi, thus affecting the succession of boreal forest ecosystems.     

Molecular Identification of Ectomycorrhizal Mycelium in Soil Horizons

Molecular identification techniques based on total DNA extraction provide a unique tool for identification of mycelium in soil. Using molecular identification techniques, the ectomycorrhizal (EM) fungal community under coniferous vegetation was analyzed. Soil samples were taken at different depths from four horizons of a podzol profile. A basidiomycete-specific primer pair (ITS1F-ITS4B) was used to amplify fungal internal transcribed spacer (ITS) sequences from total DNA extracts of the soil horizons. Amplified basidiomycete DNA was cloned and sequenced, and a selection of the obtained clones was analyzed phylogenetically. Based on sequence similarity, the fungal clone sequences were sorted into 25 different fungal groups, or operational taxonomic units (OTUs). Out of 25 basidiomycete OTUs, 7 OTUs showed high nucleotide homology (≥99%) with known EM fungal sequences and 16 were found exclusively in the mineral soil. The taxonomic positions of six OTUs remained unclear. OTU sequences were compared to sequences from morphotyped EM root tips collected from the same sites. Of the 25 OTUs, 10 OTUs had ≥98% sequence similarity with these EM root tip sequences. The present study demonstrates the use of molecular techniques to identify EM hyphae in various soil types. This approach differs from the conventional method of EM root tip identification and provides a novel approach to examine EM fungal communities in soil.     

Molecular identification of ectomycorrhizal mycelium in soil horizons

Molecular identification techniques based on total DNA extraction provide a unique tool for identification of mycelium in soil. Using molecular identification techniques, the ectomycorrhizal (EM) fungal community under coniferous vegetation was analyzed. Soil samples were taken at different depths from four horizons of a podzol profile. A basidiomycete-specific primer pair (ITS1F-ITS4B) was used to amplify fungal internal transcribed spacer (ITS) sequences from total DNA extracts of the soil horizons. Amplified basidiomycete DNA was cloned and sequenced, and a selection of the obtained clones was analyzed phylogenetically. Based on sequence similarity, the fungal clone sequences were sorted into 25 different fungal groups, or operational taxonomic units (OTUs). Out of 25 basidiomycete OTUs, 7 OTUs showed high nucleotide homology (> or = 99%) with known EM fungal sequences and 16 were found exclusively in the mineral soil. The taxonomic positions of six OTUs remained unclear. OTU sequences were compared to sequences from morphotyped EM root tips collected from the same sites. Of the 25 OTUs, 10 OTUs had > or = 98% sequence similarity with these EM root tip sequences. The present study demonstrates the use of molecular techniques to identify EM hyphae in various soil types. This approach differs from the conventional method of EM root tip identification and provides a novel approach to examine EM fungal communities in soil.     

Molecular phylogenetic biodiversity assessment of arctic and boreal ectomycorrhizal Lactarius Pers. (Russulales; Basidiomycota) in Alaska, based on soil and sporocarp DNA

Despite the critical roles fungi play in the functioning of ecosystems, especially as symbionts of plants and recyclers of organic matter, their biodiversity is poorly known in high-latitude regions. In this paper, we discuss the molecular diversity of one of the most diverse and abundant groups of ectomycorrhizal fungi: the genus Lactarius Pers. We analysed internal transcribed spacer rDNA sequences from both curated sporocarp collections and soil polymerase chain reaction clone libraries sampled in the arctic tundra and boreal forests of Alaska. Our genetic diversity assessment, based on various phylogenetic methods and operational taxonomic unit (OTU) delimitations, suggests that the genus Lactarius is diverse in Alaska, with at least 43 putative phylogroups, and 24 and 38 distinct OTUs based on 95% and 97% internal transcribed spacer sequence similarity, respectively. Some OTUs were identified to known species, while others were novel, previously unsequenced groups. Non-asymptotic species accumulation curves, the disparity between observed and estimated richness, and the high number of singleton OTUs indicated that many Lactarius species remain to be found and identified in Alaska. Many Lactarius taxa show strong habitat preference to one of the three major vegetation types in the sampled regions (arctic tundra, black spruce forests, and mixed birch-aspen-white spruce forests), as supported by statistical tests of UniFrac distances and principal coordinates analyses (PCoA). Together, our data robustly demonstrate great diversity and nonrandom ecological partitioning in an important boreal ectomycorrhizal genus within a relatively small geographical region. The observed diversity of Lactarius was much higher in either type of boreal forest than in the arctic tundra, supporting the widely recognized pattern of decreasing species richness with increasing latitude.     

Spatial Variation of Bird Species in Landscapes Dominated by Old-growth Forests in Northern Boreal Finland

An important issue in conservation planning is to study the distribution and abundance patterns of species in natural landscapes. Information of concordant and clumped species distribution pattertns can enhance attempts to focus conservation efforts in sites/areas preferred by various species. We compared bird species abundance, community composition and species distribution patterns in three large old-growth forest areas (size 40–120 km²) in northern boreal Finland on the basis of quantitative bird censuses. Total bird density and species composition, and mean density and variances of the most abundant species were highly similar between the three areas. Most of the bird species were distributed randomly within the areas and species preferring old-growth forests showed compensatory density variation without preference for any sub-area. Mean density of species preferring old-growth forests was significantly higher in the studied large old-growth forests than in smaller old-growth forests and was about threefold higher than regional density of species in a predominantly managed landscape matrix. Bird species preferring old-growth forests are probably not dependent on a certain specific part of a virgin boreal forest landscape but rather on the overall size of the high-quality and diverse old-growth forest area.     

Phylogenetic relationships and spatial distributions of putative fungal pathogens of seedlings across a rainfall gradient in Panama

Despite their importance in structuring plant communities, the identities and spatial distributions of the pathogens impacting wild plant communities are largely unknown. To advance our knowledge of plant-pathogen interactions in tropical forests, I identified likely fungal pathogens from forest sites across a rainfall gradient in Panama and compared the communities of fungi inhabiting a wetter, Atlantic and a drier, Pacific forest (∼45 km apart). Seedlings with symptoms of pathogen attack were collected and fungi were isolated from the symptomatic tissue. Based on internal transcribed spacer region sequences, I assigned the fungal isolates to operational taxonomic units (OTUs) and estimated their taxonomic placements. I observed 28 OTUs (defined by 95% sequence similarity); primarily, the genera Mycoleptodiscus, Glomerella, Bionectria, Diaporthe, and Calonectria. The wetter, Atlantic and drier, Pacific forest sites shared 29% of observed and 56% of non-singleton fungal OTUs, suggesting that, in these forests, the common fungal pathogens of seedlings are relatively widespread, habitat generalists.     

Molecular diversity and distribution of marine fungi across 130 European environmental samples

Environmental DNA and culture-based analyses have suggested that fungi are present in low diversity and in low abundance in many marine environments, especially in the upper water column. Here, we use a dual approach involving high-throughput diversity tag sequencing from both DNA and RNA templates and fluorescent cell counts to evaluate the diversity and relative abundance of fungi across marine samples taken from six European near-shore sites. We removed very rare fungal operational taxonomic units (OTUs) selecting only OTUs recovered from multiple samples for a detailed analysis. This approach identified a set of 71 fungal ‘OTU clusters'' that account for 66% of all the sequences assigned to the Fungi. Phylogenetic analyses demonstrated that this diversity includes a significant number of chytrid-like lineages that had not been previously described, indicating that the marine environment encompasses a number of zoosporic fungi that are new to taxonomic inventories. Using the sequence datasets, we identified cases where fungal OTUs were sampled across multiple geographical sites and between different sampling depths. This was especially clear in one relatively abundant and diverse phylogroup tentatively named Novel Chytrid-Like-Clade 1 (NCLC1). For comparison, a subset of the water column samples was also investigated using fluorescent microscopy to examine the abundance of eukaryotes with chitin cell walls. Comparisons of relative abundance of RNA-derived fungal tag sequences and chitin cell-wall counts demonstrate that fungi constitute a low fraction of the eukaryotic community in these water column samples. Taken together, these results demonstrate the phylogenetic position and environmental distribution of 71 lineages, improving our understanding of the diversity and abundance of fungi in marine environments.     

PLFA Profiling of Microbial Community Structure and Seasonal Shifts in Soils of a Douglas-fir Chronosequence

The impact and frequency of forest harvesting could significantly affect soil microbial community (SMC) structure and functioning. The ability of soil microorganisms to perform biogeochemical processes is critical for sustaining forest productivity and has a direct impact on decomposition dynamics and carbon storage potential. The Wind River Canopy Crane Research Forest in SW, WA, provided a unique opportunity to study a forest chronosequence and the residual effects of harvesting on the SMC in comparison to old-growth forests. The objective of this study was to determine the effect of clear-cutting and stand age on temporal dynamics of SMC and physiological stress markers using phospholipid fatty acid (PLFA) profiling. Soil microbial PLFA profiles were determined seven times over 22 months (Nov. 02 to Sep. 04) in old-growth coniferous forest stands (300–500 years) and 8 (CC8)- or 25 (CC25)-year-old replanted clear-cuts. PLFA patterns of the SMC shifted because of clear-cutting, but seasonal temporal changes had greater shifts than differences among stand age. The microbial biomass (total PLFA) and bacterial, fungal, and selected other PLFAs were significantly reduced in CC8 but not in CC25 sites relative to the old-growth sites. An increase in stress indicators [PLFA ratios of saturated/monsaturated and (cy17:0 + cy19:0)/(16:1ω7 + 18:1ω7)] in late summer was related to water stress. Although the canopy and litter input are quite different for a 25-year clear-cut compared to virgin old-growth forest, we conclude that the composition of the microbial communities, 25 years after clear-cutting, has recovered sufficiently to be much more similar to old-growth forests than a recent clear-cut at this Pacific Northwest forest site. The study shows the potential of PLFA analysis for profiling microbial communities and their stress status under field conditions, but wide temporal shifts emphasize the need for sampling over seasons to fully interpret ecosystem management impacts on microbial populations.     

Soil propagule banks of ectomycorrhizal fungi share many common species along an elevation gradient

We conducted bioassay experiments to investigate the soil propagule banks of ectomycorrhizal (EM) fungi in old-growth forests along an elevation gradient and compared the elevation pattern with the composition of EM fungi on existing roots in the field. In total, 150 soil cores were collected from three forests on Mt. Ishizuchi, western Japan, and subjected to bioassays using Pinus densiflora and Betula maximowicziana. Using molecular analyses, we recorded 23 EM fungal species in the assayed propagule banks. Eight species (34.8 %) were shared across the three sites, which ranged from a warm–temperate evergreen mixed forest to a subalpine conifer forest. The elevation pattern of the assayed propagule banks differed dramatically from that of EM fungi on existing roots along the same gradient, where only a small proportion of EM fungal species (3.5 %) were shared across sites. The EM fungal species found in the assayed propagule banks included many pioneer fungal species and composition differed significantly from that on existing roots. Furthermore, only 4 of 23 species were shared between the two host species, indicating a strong effect of bioassay host identity in determining the propagule banks of EM fungi. These results imply that the assayed propagule bank is less affected by climate compared to EM fungal communities on existing roots. The dominance of disturbance-dependent fungal species in the assayed propagule banks may result in higher ecosystem resilience to disturbance even in old-growth temperate forests.     

Loss of biodiversity and shifts in aboveground biomass drivers in tropical rainforests with different disturbance histories

Tropical forests account for more than half of the global carbon forest stock and much of the biological diversity on Earth. However, disturbances such as deforestation and forest degradation threaten the maintenance of these ecosystem services. This study aimed to understand how different disturbance histories affect the forest stand biomass, as well as species and functional diversity, and to what extent these differences can change the relationships between biomass and their drivers. We used data from forests with clear-cut and selectively logged disturbance histories, and from old-growth forests, situated in the Brazilian Atlantic forest. Forests with logging disturbances showed significant losses in their aboveground biomass compared to those of old-growth forests (50% loss in selectively logged forests and 80% loss in clear-cut forests). Interestingly, only clear-cut secondary forests showed differences in species and functional diversity, and were dominated by species with acquisitive trait values, commonly found early in succession. Shifts in stand biomass drivers were observed in selectively logged forests. The mass-ratio hypothesis (mainly through the functional trait of maximum height) was the most important biomass driver in clear-cut secondary and old-growth forests, whereas the importance of the niche complementarity hypothesis (through functional richness and dispersion) was higher in selectively logged forests. Our study highlights that disturbance histories can affect forest aboveground biomass and its drivers. Moreover, our results reinforce the need for conservation of intact forests but highlight the importance of including degraded forests in conservation mechanisms based in carbon stocks, as these forests retain high values of species and functional diversities that are crucial to biomass and consequently carbon stock acquisition.     

Decreasing negative impacts of harvesting over insect communities using variable retention in southern Patagonian forests

Variable retention is an alternative silvicultural approach to timber forest management, which consist in a regeneration treatment with different degrees and patterns of stand retention. It has been proposed to mitigate harmful effects of harvesting, but effectiveness in insect conservation remains unknown in southern Patagonian Nothofagus pumilio forests. Here, the objectives were to: (1) define a baseline of insect diversity in old-growth forests along a site quality gradient (high, medium and low, associated to the forest productivity of each site); (2) evaluate stands with different retention treatments [aggregated (AR) surrounded by dispersed (DR) retention, and aggregated retention surrounded by clear-cut (CC)] and to compare with old-growth unmanaged forests (OGF); and (3) assess temporal changes during the first 4 years after harvesting (YAH). In a long term forest research plot, mobile epigean insect richness and relative abundance were characterized and classified in seven response type groups, using a wide spectrum sampling set. Data analyses included parametric and permutational ANOVAs, multivariate classification and ordinations. There were found 79 species before harvesting, and that richness was not related to site quality. After harvesting, 84 new species were added considering all treatments along the first four sampled YAH, of which 65 % were added to OGF, while in harvested sites richness and abundance directly diminished with retention degree (OGF > AR > DR > CC) due to incoming species cannot compensate the lost of them. However, fluctuations in diversity were observed along the YAH. Therefore, harvesting reduces insect richness in N. pumilio forests independently of the treatment, but the original insect assemblage significantly changes due to loss of sensitive species and introduction of others from surrounding environments. Despite this, inclusion of aggregates greatly diminished harvesting impacts because insect assemblage is favoured when structural complexity is preserved, conserving richness and abundance at similar levels than in old-growth forests. However, more studies are necessary to evaluate effects of different aggregate size, shape and distribution into harvested forests, as well as their fragmentation and connectivity at landscape level.     

Forests regenerating after clear-cutting function as habitat for bryophyte and lichen species of conservation concern

The majority of managed forests in Fennoscandia are younger than 70 years old but yet little is known about their potential to host rare and threatened species. In this study, we examined red-listed bryophytes and lichens in 19 young stands originating from clear-cutting (30-70 years old) in the boreal region, finding 19 red-listed species (six bryophytes and 13 lichens). We used adjoining old stands, which most likely never had been clear-cut, as reference. The old stands contained significantly more species, but when taking the amount of biological legacies (i.e., remaining deciduous trees and dead wood) from the previous forest generation into account, bryophyte species number did not differ between old and young stands, and lichen number was even higher in young stands. No dispersal effect could be detected from the old to the young stands. The amount of wetlands in the surroundings was important for bryophytes, as was the area of old forest for both lichens and bryophytes. A cardinal position of young stands to the north of old stands was beneficial to red-listed bryophytes as well as lichens. We conclude that young forest plantations may function as habitat for red-listed species, but that this depends on presence of structures from the previous forest generation, and also on qualities in the surrounding landscape. Nevertheless, at repeated clear-cuttings, a successive decrease in species populations in young production stands is likely, due to increased fragmentation and reduced substrate amounts. Retention of dead wood and deciduous trees might be efficient conservation measures. Although priority needs to be given to preservation of remnant old-growth forests, we argue that young forests rich in biological legacies and located in landscapes with high amounts of old forests may have a conservation value.     

Identifying airborne fungi in Seoul,Korea using metagenomics

Fungal spores are widespread and common in the atmosphere. In this study, we use a metagenomic approach to study the fungal diversity in six total air samples collected from April to May 2012 in Seoul, Korea. This springtime period is important in Korea because of the peak in fungal spore concentration and Asian dust storms, although the year of this study (2012) was unique in that were no major Asian dust events. Clustering sequences for operational taxonomic unit (OTU) identification recovered 1,266 unique OTUs in the combined dataset, with between 223?96 OTUs present in individual samples. OTUs from three fungal phyla were identified. For Ascomycota, Davidiella (anamorph: Cladosporium) was the most common genus in all samples, often accounting for more than 50% of all sequences in a sample. Other common Ascomycota genera identified were Alternaria, Didymella, Khuskia, Geosmitha, Penicillium, and Aspergillus. While several Basidiomycota genera were observed, Chytridiomycota OTUs were only present in one sample. Consistency was observed within sampling days, but there was a large shift in species composition from Ascomycota dominant to Basidiomycota dominant in the middle of the sampling period. This marked change may have been caused by meteorological events. A potential set of 40 allergyinducing genera were identified, accounting for a large proportion of the diversity present (22.5?7.2%). Our study identifies high fungal diversity and potentially high levels of fungal allergens in springtime air of Korea, and provides a good baseline for future comparisons with Asian dust storms.     

Changes in the root-associated fungal communities along a primary succession gradient analysed by 454 pyrosequencing

We investigated changes in the root-associated fungal communities associated with the ectomycorrhizal herb Bistorta vivipara along a primary succession gradient using 454 amplicon sequencing. Our main objective was to assess the degree of variation in fungal richness and community composition as vegetation cover increases along the chronosequence. Sixty root systems of B. vivipara were sampled in vegetation zones delimited by dated moraines in front of a retreating glacier in Norway. We extracted DNA from rinsed root systems, amplified the ITS1 region using fungal-specific primers and analysed the amplicons using 454 sequencing. Between 437 and 5063 sequences were obtained from each root system. Clustering analyses using a 98.5% sequence similarity cut-off yielded a total of 470 operational taxonomic units (OTUs), excluding singletons. Between eight and 41 fungal OTUs were detected within each root system. Already in the first stage of succession, a high fungal diversity was present in the B. vivipara root systems. Total number of OTUs increased significantly along the gradient towards climax vegetation, but the average number of OTUs per root system stayed unchanged. There was a high patchiness in distribution of fungal OTUs across root systems, indicating that stochastic processes to a large extent structure the fungal communities. However, time since deglaciation had impact on the fungal community structure, as a systematic shift in the community composition was observed along the chronosequence. Ectomycorrhizal basidiomycetes were the dominant fungi in the roots of B. vivipara, when it comes to both number of OTUs and number of sequences.     

Relationships of fungal spore concentrations in the air and meteorological factors

High concentrations of airborne fungal spores are associated with human health concerns. Environmental variables, such as temperature and moisture, can influence growth and reproduction in fungi and airborne spore concentrations can fluctuate seasonally. However, we do not understand how long-term changes in climate affect fungal abundance in the air. Here, we sampled annually (at peak season, in September, over a 20-yr period) for airborne fungal spores in two North American cities (New York and Toronto), and related fungal abundance to local variation in climate. We found that at both locations, the total precipitation during the 2- month period prior to sampling (Jul.–Aug.) was negatively related to observed fungal spore concentrations. Considering that climate predictions for these two regions indicate an increase in drought events in summer, we expect airborne fungal concentrations to increase in future years, potentially exacerbating human health concerns.     

Structure and species composition of ectomycorrhizal fungal communities colonizing seedlings and adult trees of Pinus montezumae in Mexican neotropical forests

Mexico is a center of diversity for pines, but few studies have examined the ectomycorrhizal (ECM) fungal communities associated with pines in this country. We investigated the ECM communities associated with Pinus montezumae seedlings and mature trees in neotropical forests of central Mexico and compared their structure and species composition. Root tips were sampled on both planted seedlings and naturally occurring adult trees. A total of 42 ECM operational taxonomic units (OTUs) was found on P.?montezumae. Diversity and similarity indices showed that community structure was similar for both plant growth stages, but phylogenetic diversity and Chao-estimated richness were higher for seedlings. Species composition differed between communities. The dominant OTUs belonged to the families Atheliaceae, Cortinariaceae, and Sebacinaceae, although different taxa appeared to colonize seedlings and adults. Only 12 OTUs were shared between seedlings and adults, which suggests that ECM fungi which colonize seedlings are still not fully incorporated into mycelial networks and that ECM taxa colonizing young individuals of P.?montezumae are likely to come from fungal propagules. Intra-generic diversity could be an insurance mechanism to maintain forest productivity under stressed conditions. This is the first report describing the abundance of Atheliaceae in tree roots in neotropical ecosystems.     

A metabarcoding comparison of windward and leeward airborne algal diversity across the Ko‘olau mountain range on the island of O'ahu,Hawai‘i1

Airborne algae from sites on the windward (n = 3) and leeward (n = 3) sides of the Ko‘olau Mountain range of O‘ahu, Hawai‘i, were sampled for a 16 d period during January and February 2015 using passive collection devices and were characterized using Illumina MiSeq sequencing of the universal plastid amplicon marker. Amplicons were assigned to 3,023 operational taxonomic units (OTUs), which included 1,189 cyanobacteria, 1,009 heterotrophic bacteria, and 304 Eukaryota (of which 284 were algae and land plants). Analyses demonstrated substantially more OTUs at windward than leeward O‘ahu sites during the sampling period. Removal of nonalgal OTUs revealed a greater number of algal reads recovered from windward (839,853) than leeward sites (355,387), with the majority of these being cyanobacteria. The 1,234 total algal OTUs included cyanobacteria, diatoms, cryptophytes, brown algae, chlorophyte green algae, and charophyte green algae. A total of 208 algal OTUs were identified from leeward side samplers (including OTUs in common among samplers) and 1,995 algal OTUs were identified from windward samplers. Barcoding analyses of the most abundant algal OTUs indicated that very few were shared between the windward and leeward sides of the Ko‘olau Mountains, highlighting the localized scale at which these airborne algae communities differ. Back trajectories of air masses arriving on O‘ahu during the sampling period were calculated using the NOAA HY‐SPLIT model and suggested that the sampling period was composed of three large‐scale meteorological events, indicating a diversity of potential sources of airborne algae outside of the Hawaiian Islands.