Exploring concealed hydrothermal activity in Lāna'i (Hawaiian Islands) and its hydrogeological effects through geophysical surveys

ABSTRACT Tourism demand forecasting is essential for destination management and policy planning. This study develops a spatio-temporal deep learning framework based on Graph WaveNet to forecast daily tourist arrivals across the Hawaiian Islands. The proposed model jointly captures temporal dynamics and dynamic spatial dependencies among destinations, enabling more accurate multi-step demand prediction. Using island-level arrival data, we compare the proposed approach with classical statistical models and neural network–based benchmarks. The results show that the Graph WaveNet model consistently outperforms baseline methods across multiple forecasting horizons. These findings demonstrate the value of incorporating spatio-temporal structures into tourism demand forecasting and provide practical insights for regional tourism analytics and decision-making.

This study aims to quantify environmental health impacts and assess risk by understanding the disproportionate burden of infectious diseases, specifically Influenza-like Illness (ILI), across regions with varying socio-economic characteristics. We introduce a novel vulnerability-based approach to better understand the complex relationship between socio-economic factors and ILI burden. We developed a machine-learning-driven framework to assess and map state-level socio-economic vulnerability to ILI in the United States. A vulnerability index was created by integrating 39 diverse socio-economic and health indicators from the latest CENSUS. A Random Forest Regression model then weighed these indicators to quantify each state's vulnerability for the ILI values in 2022. To assess multicollinearity, Variance Inflation Factor (VIF) was calculated, and parameters were filtered to reduce the VIF. Key determinants of vulnerability include migration patterns, insurance coverage, and proportions of female and elderly populations. The resulting state-level vulnerability map reveals significant regional disparities. District of Columbia was identified as the most vulnerable state, followed by Massachusetts, Hawaii, New Mexico, and Rhode Island, all with normalized vulnerability indices exceeding 0.35. Our findings highlight significant regional variations in ILI vulnerability, emphasizing the need for targeted public health interventions tailored to state-specific socio-economic conditions. This scalable and adaptable methodology extends beyond influenza, offering a valuable approach for assessing vulnerability to a wide range of infectious diseases, strengthening epidemic preparedness and response.

The Hawaiian-Emperor chain has exhibited two distinct Loa-Kea magmatic groups over the past 8 million years, but their origin remains debated. Using paleographically constrained global mantle convection models, we reproduce the present-day location of the Hawaiian hot spot and the associated spatiotemporal geochemical evolution. The composition of the plume conduit shows conventional concentric zoning prior to the Hawaiian-Emperor Bend and gradually evolves to a north-south bilateral zoning pattern afterward, corresponding to the subparallel Loa-Kea trends. Further analysis suggests that the plume originates from ridges of large low-velocity province (LLVP) induced by the push of slabs. Upwelling at the intersections of ridges is more energetic than at the middle of the ridge, causing bottom-up splitting of plume conduit in the lower mantle that propagates upward, forming bilateral zoning and eventually two independent plumes. This process suggests that bilateral zoning is transient and more common in the Pacific than Africa due to the circum-Pacific subduction.

ABSTRACT Geochemical studies of basalt quarries, rock sources and stone adzes and their biproducts found at distant habitation sites have increasingly allowed archaeologists to track the direction of island colonisation and post‐settlement interaction and proffer explanations for the development of social complexity in Polynesia. The Tuamotu Archipelago is unrivalled for studying inter‐archipelago transfer of stone tools in East Polynesia, as the islands consist of coral sand and limestone with no local sources of volcanic rock. Indeed, with at least 155 imported stone adzes known from the Tuamotus weighing ∼75 kg—more than any other archipelago in Polynesia—the challenge is to determine artefact origin. Using museum collections, we geochemically analysed 25 basalt adzes and preforms (in addition to 19 analyses from a previous study), to track intra‐and inter‐archipelago transfer of these stone tools. Artefacts analysed by inductively coupled mass spectrometry (ICP‐MS) were demonstrated to have originated from the Hawaiian Islands, some 4000 km distant, Marquesas Islands, Pitcairn Island, Austral Islands, the Society Islands and possibly Sāmoa. As almost all artefacts were from known atolls, but not dated archaeological sites, we used Duff adze types to assign broad temporal control to the assemblage. We acknowledge that the importance of long‐curated museum collections cannot be overstated.

Abstract Understanding the acoustic communication of the endangered main Hawaiian Islands insular population of false killer whales (Pseudorca crassidens) is essential for effective management. In this study, biologging tags were deployed on four individuals, recording 26.2 h of acoustic data. A total of 5940 high-quality possible focal pulsed calls were analysed and 52 stereotyped call types were characterized. The fundamental frequency contour ranged from a mean minimum frequency of 7.22 ± 0.78 to 9.28 ± 0.80 kHz (mean maximum frequency) with a mean duration of 0.32 ± 0.08 s. Predominant call types and call rates across dive states varied by individual. Probability of calling was higher during the descent and bottom phase compared with the surface. Four types of nonlinear phenomena (NLP) were documented including biphonation (call + clicks, 78% of all NLP), secondary sidebands, chaos and frequency jumps. Frequency jumps were commonly produced by two animals from the same group (13–19%). Most calls contained NLP (80%). The average call rate recorded by the tags on two individuals was 17.5 calls m−1 (hourly average) and call rates decreased as swim speed increased. Our findings suggest high repertoire diversity and high signal complexity informing future passive acoustic monitoring efforts.

A new species of Peperomia with alternate leaves from Kaua‘i, Hawaiian Islands, is described and illustrated, with notes on its conservation status, distribution and ecology. We present a dichotomous key to all five Hawaiian Peperomia species with alternate leaves and include notes on two possibly extinct Hawaiian Peperomia species, namely P.degeneri and P.subpetiolata. Peperomiakauaianasp. nov. differs morphologically from its Hawaiian congeners by its unique combination of diminutive leaves 5–14(–18) mm long, 4–11(–14) mm wide, palmately 5- to 7-nerved, ovate to ovate-orbicular with margins revolute, petioles 2–5 mm long and spikes 11–17(–22) mm long. Plants have been documented in three distinct windward Kaua‘i locations to date, including the southern ridges of Wahiawa, the central ridges of Wai‘ahi and the north-eastern ridges of the Makaleha Mountains. Peperomiakauaiana represents a newly-described wet forest species endemic to the island of Kaua‘i and is currently in need of conservation. Its discovery raises the total number of endemic Hawaiian Peperomia species to 24 and single-island endemic Peperomia on Kaua‘i to three.

We have reported the first mitochondrial (GenBank accession PV035080) and chloroplast (GenBank accession PV035081) genomes for a representative of the gigartinalean family Dumontiaceae (Gibsmithia punonomaewa). High-throughput sequencing yielded both organellar genomes for the holotype specimen of Gibsmithia punonomaewa, a recently described species that is also a putative endemic to the mesophotic zone of the Hawaiian Islands. Gene content and order of the 26,428-bp mitochondrial genome are conserved relative to other available genomes of the Gigartinales. The genome contains 52 genes, including 25 protein-coding sequences (CDSs), 3 rRNAs, and 24 tRNAs, as well as one group II intron in a trnI-GAU tRNA. The chloroplast genome is 185,316 bp in length and contains 236 genes, including 203 CDSs, three rRNAs, and 30 tRNAs, and one group II intron in a trnM-CAU tRNA. Both organellar genomes displayed high synteny compared to close relatives in the order Gigartinales, with unique features restricted to several open reading frames. Phylogenomic analyses of the mitochondrial and chloroplast genomes with other gigartinalean representatives yielded well-resolved phylogenies that supported an early diverging position of the Dumontiaceae within the order Gigartinales.

Several insect lineages, including some fruit flies, have evolved mutualistic associations with primary symbiotic bacteria. Some species of Tephritinae, the most specialized subfamily of fruit flies (Diptera, Tephritidae) harbour co-evolved, vertically transmitted and non-culturable bacterial symbionts in their midgut, known as Candidatus Stammerula spp. (Enterobacteriaceae). While such associations have previously been reported in the Palearctic and Hawaiian Archipelago, their occurrence in Australasia had not been investigated. In this study we assessed the genetic diversity of eight Australian fruit fly's species from six genera belonging to the Tephritini tribe using mitochondrial markers (16S rRNA and COI-tRNALeu-COII genes) and compared their bacterial diversity using the 16S rRNA gene. We detected the presence of specific symbiotic bacteria in all sampled species. Analysis of bacterial 16S rRNA showed that, with one exception, all Australian symbionts clustered in a well-supported monophyletic clade with Ca. Stammerula detected in Palearctic and Hawaiian Tephritini. Distinct Stammerula lineages were identified in several taxa, while two species, Trupanea prolata and Spathulina acroleuca shared identical symbiont sequences and the same host plant. Notably, Australian and Palearctic Sphenella spp. harboured closely related symbionts. The cophylogenetic analysis revealed a substantial congruence between host and symbiont tree, supporting a history of cospeciation and suggesting biogeographic links between Australasian and Palearctic taxa. Overall, the results expand the geographic knowledge of Tephritini-Ca. Stammerula association and highlight a global pattern of co-diversification.

Shark bite incidents in Hawaiian waters exhibit a significant seasonal pattern, with October experiencing a disproportionate spike in bites despite no corresponding increase in ocean recreational activity. Analysis of 30 years of bite records (1995–2024) reveals that 20% of all incidents occurred in October, a frequency 2 to 4 times higher than in any other month. Statistical modeling confirms October’s significantly elevated bite probability and count. Tiger sharks ( Galeocerdo cuvier ) are the primary driver of this pattern, accounting for at least 63% of October bites. This seasonal trend aligns with peak tiger shark sightings at ecotourism sites and the partial migration of mature females from the Northwestern Hawaiian Islands, suggesting a potential link to reproductive cycles. Parturition during September–October may increase encounters via two mechanisms: (1) a temporary rise in nearshore adult female abundance and (2) heightened foraging by postpartum individuals recovering from energy depletion. These findings provide ecological insight into seasonal shark bite risk and highlight potential biological drivers warranting further investigation.

Abstract Studies of biodiversity loss commonly imply that species extinctions occurred as a direct result of initial human arrival and thus are attributable to stewardship failures of Indigenous Peoples. However, recent studies have suggested this assumption is not supported by the evidence, prompting a global reevaluation of existing assumptions. To assess the relationship between human arrival in the Hawaiian Islands and documented declines in waterbird biodiversity, we reviewed empirical evidence from paleoecological studies. We first identified the time period that extinct Hawaiian waterbird species were last observed within the fossil record. We then evaluated four hypotheses proposed to explain drivers of Holocene waterbird extinctions: (1) the overkill hypothesis; (2) the deforestation hypothesis; (3) the climate change hypothesis; and (4) the species introductions hypothesis. Of the 18 extinct waterbird species evaluated in this study, 10 were last observed in the fossil record prior to Polynesian arrival, 6 were last observed in the fossil record during the Polynesian era, and 2 were last visually observed after European arrival. Extinctions that possibly occurred during the Polynesian era were likely caused by a suite of factors, some anthropogenic and some non‐anthropogenic. Our findings contradict previous studies that attributed Holocene waterbird extinctions to hunting and deforestation by Native Hawaiians and suggest a future line of inquiry regarding a proposed “regime shift extinctions” in hypothesis to explain complex impacts of human‐mediated and climatic drivers of extinction in the Anthropocene.

Biogeochemical anatomy and ecosystem dynamics of a large phytoplankton bloom north of the Hawaiian Islands

Drawing on the perspective of diaspora archaeology, this study analyzes 2,066 funeralrelated articles published in Kukminbo(國民報, the Korean National Herald, 1930–1969) together with material evidence from Korean headstones across the Hawaiian Islands. It examines how early Korean immigrants in Hawaiʻi constructed and maintained their social order and collective identity through funeral ceremonies. The analysis shows that Korean funerals in Hawaiʻi were organized into a complex social system structured around four axes: speed, space, mobilization, and memory. First, the practice of Sokjang(速葬, rapid funeral), which completed funerals within an average of three to four days, and the tripartite spatial arrangement of mortuary, church, and cemetery represent an operational adaptation to modern American society’s emphasis on efficiency. The replacement of traditional Tongya(通夜, all-night wakes) with American-style viewings further illustrates the community’s strategic adaptation to external pressures such as wartime regulations and the rise of the funeral industry. Second, at the center of this system stood the Hosangbu(護喪部, Funeral Assistance Department), which established a trust-based moral economy by transparently disclosing its finances and communalizing the estates of those who died without kin. This indicates that the community functioned as a diasporic proto-state that autonomously operated systems of social welfare and governance. Third, headstones, as the final material traces of these rituals, serve as key sources for an archaeology of memory. The coexistence of Confucian terms, Christian symbols, and pre-division national designations such as Joseon(朝鮮) and Daehan(大韓) even after the Korean War suggests that cemeteries functioned as non-divided(非分斷) spaces that preserved the immigrants’ unified national identity. By bringing together textual and archaeological evidence, this study expands the methodological horizon of diaspora archaeology and empirically reconstructs the processes through which a diaspora community in Hawaiʻi established its identity and autonomous order through funerary practices.

In view of the toxic effects of persistent organic pollutants (POPs), fast and effective assessment of their concentrations in marine mammals is important for understanding individual and population-level health impacts. This study developed an ultrasonic-based method that is less time-consuming, uses minimal solvent, and thus is more sustainable than the gold standard Soxhlet method for accurate analysis of organochlorine pesticides (OCs), polychlorinated biphenyls (PCBs), and benzene hexachlorides (BHC) in false killer whale blubber. This method was developed by comparing concentrations of POPs obtained using the traditional Soxhlet and novel ultrasonic extraction methods using blubber from false killer whales (n = 4) that were stranded in the Hawaiian Islands. The average total POPs extracted from the four killer whales and adjusted for lipid weight (lw) were 11,379.57 ± 3,303.03 ng/g lw for Soxhlet extraction and 14,310.39 ± 4,469.00 ng/g lw for the ultrasonic method, indicating a greater extraction efficiency of the ultrasonic method. The results further revealed that false killer whale FKW2013018 (∑OCs 15,447.38 ± 812.17 ng/g lw and ∑PCBs 5,205.32 ± 253.46 ng/g lw) and false killer whale FKW2016016 (∑OCs 18,164.90 ± 1,433.15 ng/g lw and ∑PCBs 4,913.32 ± 447.29 ng/g lw) accumulated organochlorines and PCBs at very high and potentially toxic levels. The low ratio of 4,4'-DDT/4,4'-DDE (0.026 ± 0.004) using both extraction methods indicated that the stranded false killer whales experienced long-term exposure to 4,4'-DDT, leading to bioaccumulation of the stable 4,4'-DDE metabolite. The levels of OCs, PCBs, and BHCs in this study were below toxic threshold levels. However, in view of the susceptibility of cetaceans with reduced lipid content to the toxic effects of POPs, cetaceans with low lipid content (as a result of starvation, fasting, or extended migration events) may be at higher risk of the negative health impacts of organic pollutants.

The Hawaiian Islands, shaped by a legacy of intensive plantation agriculture, continue to face persistent soil contamination with heavy metals, particularly arsenic and lead, which are remnants of historic pesticide and industrial chemical application. Today, these contaminants pose elevated environmental and human health risks, especially in areas repurposed as residential neighborhoods and public parks. This review consolidates current evidence on the primary contamination sources, spatial distribution, and potential health impacts of arsenic and lead in Hawaiian soils. It also evaluates and confirms advanced field and laboratory assessment techniques, namely, decision unit–multi-increment sampling and energy dispersive X-ray fluorescence, which are increasingly employed in Hawai’i for efficient and representative analysis. By synthesizing regulatory guidelines, historical land-use records, and recent case studies, this article emphasizes the necessity of thorough legacy contamination assessments to inform safe land conversion practices. These findings offer valuable insights for future research, remediation strategies, and policy development, both in Hawai‘i and in similar post-agricultural contexts globally.

SynopsisEvolution on islands often generates specialized lifestyles that are rarely seen in continental species. The biota on oceanic islands are, however, prone to extinctions following human colonization, resulting in an incomplete understanding of the lifestyles of species that evolved prior to colonization. For example, the Hawaiian Islands hosted a unique and diverse assemblage of endemic taxa, most of which became extinct following human colonization. Among these is Apteribis (Threskiornitidae), an extinct genus of flightless ibises for which nothing is known of their behaviour and ecology. To gain insight into the foraging behaviour and activity pattern of this unusual genus, we quantified their olfactory, visual, and somatosensory systems from direct measurements of skulls, CT scans, and endocasts. We then compared Apteribis with extant ibises with phylogeny-informed statistics to determine if they differed significantly in any of our measured traits. Our analyses show that the olfactory and somatosensory systems of Apteribis are comparable in size and anatomy to those of extant ibises and it was likely flexible in terms of preferred foraging habitat. In contrast, the visual system of Apteribis is greatly reduced in size, suggesting a nocturnal lifestyle, which is an unprecedent trait among ibises. Our data therefore suggests that Apteribis occupied a niche similar to that of New Zealand kiwi (Apteryx): nocturnal, flightless species that rely on tactile cues from its beak to detect prey. This study provides the first quantitative evidence for the evolution of a kiwi-like niche for a bird outside New Zealand, and emphasizes the remarkable diversity of avian lifestyles lost due to anthropogenic impact.

Tiger sharks (Galeocerdo cuvier) are typically solitary marine predators that are rarely observed forming aggregations. We analyzed long-term acoustic telemetry data from the Hawaiian Archipelago that indicate that there are seasonal partial migrations within the population. We investigated whether these migrations are driven primarily by mating or foraging behaviors. Mature tiger sharks tagged around O ‘ahu migrated seasonally to Maui, with timing aligned with the known mating season in Hawai ‘i. In contrast, sharks tagged around Maui displayed year-round residency (no seasonal departures). Seasonal philopatry was most pronounced at Olowalu, Maui. At this site, we observed a high spatiotemporal overlap between mature males and females and physical signs of mating activity for both sexes, which suggested a mating aggregation. Shark abundance at Olowalu peaked approximately one month prior to the peak presence of adult humpback whales (Megaptera novaeangliae). Whale calf abundance was moderately correlated with shark detection rates, suggesting that foraging opportunities might also influence the timing of shark aggregations. These aggregations appear diffuse rather than dense, extending over several kilometers and persisting for several weeks. Our findings provide the first evidence of potential seasonal mating aggregations in tiger sharks, a behavior previously undocumented for this typically solitary species.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-27742-y.

Seasonal rainfall and runoff of sediments from the Hawaiian Islands could be responsible for the previously undetected peak.

Understanding connectivity between populations is key to identifying hotspots of diversity, dispersal sinks and sources, and effective management units for natural resources. Multi-species connectivity seeks to overcome species-specific idiosyncrasies to identify shared patterns that are most critical to spatial management. The linear Hawaiian archipelago provides an excellent platform to assess multi-species connectivity patterns, with shared boundaries to gene flow identified across a majority of the 41 coral reef species surveyed to date. Here, we evaluate genome-scale data by comparing consistency and resolution to previous connectivity studies using far fewer loci. We used pool-seq to genotype 22,503–232,730 single nucleotide polymorphisms per species (625,215 SNPs total) from the same individuals published in previous studies of two fishes, two corals, and two lobsters. Additionally, one coral species (Pocillopora meandrina) without previous archipelago-wide population genetic data was included. With greater statistical power, most genetic differences between pairwise comparisons of islands were significant (250 of 308), consistent with the most recent larval dispersal models for the Hawaiian Archipelago. These data reveal significant differentiation at a finer scale than previously reported using single-marker studies, yet did not overturn any of the conclusions or management implications drawn from previous studies. We confirm that population genomic datasets are consistent with previously reported patterns of multispecies connectivity but add a finer layer of population resolution that is pertinent to management.

Drosophila suzukii is a common agricultural pest in numerous parts of the world, costing more than $500 million annually in crop loss in the United States alone. Understanding the genetic and physiological mechanisms underlying its remarkable adaptability has been a major focus for the agricultural industry as well as evolutionary biologists. The microbiome, the community of microbes associated with host organisms, can play a pivotal role in local adaptation by improving host resilience to environmental stress and providing access to new sources of nutrition. Here, we test the hypothesis that the colonization of non-native regions is associated with the incorporation of regionally-specific microbial taxa. We compare the microbiome profiles of wild-caught D. suzukii across five global sites, Asia, Europe, the United Kingdom, North America, and Hawai‘i. We also compare microbial communities of D. suzukii found in Hawai‘i to another local invasive species, D. immigrans , and native Hawaiian drosophilids. Our results reveal that wild-caught D. suzukii from Asia, Europe, the United Kingdom, North America, and the Hawaiian Islands exhibit distinct microbial compositions indicating that the environment is a stronger driver of microbiome composition than species identity. Seven bacterial families were conserved between all wild D. suzukii populations. Within Hawai‘i, non-native D. suzukii bacterial communities differed from those of native Hawaiian Drosophila species as well as non-native D. immigrans . By contrast, fungal microbiome profiles between the Hawaiian Drosophila and two invasive species closely resemble each other. In sum, all populations of D. suzukii in this study contain a subset of conserved bacterial families but also incorporate local bacterial taxa. This strategy may contribute to the rapid range expansion of D. suzukii and enhance its ability to exploit new dietary sources.