The U.S. Tropical Pacific (USTP) is a globally important area for seabirds with tens of millions of individuals of 32 species breeding in the region. The two greatest threats to breeding seabirds in the USTP are inundation of colonies caused by global climate change and non-native predators. We assessed the status of seabird species breeding in the USTP and which species would benefit most from restoration activities. We scored each species for nine criteria that reflected their extinction risk and vulnerability to climate change and invasive predators, then summed the scores of all criteria to obtain an overall score and ranked the species in terms of overall conservation need. The top five species at risk (in order) were Hawaiian Petrel (Pterodroma sandwichensis), Newell's Shearwater (Puffinus newelli), Polynesian Storm-Petrel (Nesofregetta fuliginosa), Phoenix Petrel (Pterodroma alba), and Black-footed Albatross (Phoebastria nigripes). We also assessed 86 locations in the USTP as potential source and restoration sites for seabirds to mitigate the impacts of sea level rise and invasive predators. Some restoration actions are underway for three of the top five species in the USTP, but more actions are needed. Two of the top species (Polynesian Storm-petrel and Phoenix Petrel) occur primarily outside the USTP. Actions within the USTP are needed to complement existing conservation measures underway elsewhere in the Pacific and should be prioritized for future management actions.

The negative effects of introduced small mammals have been well documented on islands, but their presence in the Mariana Islands warrants special attention, as they are an important prey species of the introduced brown treesnake (Boiga irregularis), which devastated the avifauna of Guam and remains a threat for introduction to nearby islands. The U.S. Navy has a major presence in the Mariana Islands and is charged with maintaining biosecurity protocols when transporting equipment between islands. We conducted small mammal trapping on Tinian, located approximately 165 km northeast of Guam, in 2017 as a baseline survey of introduced species distribution in areas used for military training. These data will facilitate long-term monitoring of introduced small mammals and early detection of newly established species. We also report an updated Catch Per Unit Effort index of small mammal abundance and tested for differences in capture success across species and between two trap types: Sherman live traps and Victor snap traps. We confirmed general patterns of abundance and distribution from previous sampling on Tinian: Rattus diardii and Suncus murinus were common and widespread, Mus musculus less common and more patchy in distribution, R. norvegicus rare, and R. exulans not detected. Comparisons between Sherman and Victor traps showed important differences in species-specific capture rates on Tinian and aligned with previous research from the Mariana Islands.

Few ponds are found in the permeable volcanic landscape of Hawaii. After Hurricane Lane passed close to Hawaii Island in August 2018, causing record rainfalls, a pond temporarily emerged on the Mauna Kea summit plateau that had never been reported before. We characterize the pond using satellite observations and electrical resistivity tomography. The shallow pond is located on glacial till 3,594 m a.s.l., and was visible for less than 1 week. The geophysical survey, carried out 10 months after the pond's appearance and disappearance, revealed a layer of low electrical resistivity at depths of about 1–3 m below the surface, which, based on laboratory analysis, likely represents a perennial body of water well protected from evaporation. The existence of a third pond, in addition to Lake Waiau and Pu‘upōhaku Pond, in the previously glaciated area suggests perching layers are not uncommon. Montmorillonite, a 3-layer shrink-swell clay that can help to perch water, was identified in the Lake Waiau area. Mineral analysis on surface samples of the third pond did not reveal such a clay mineral.

Lake Tagimaucia, a montane volcanic lake on Taveuni Island, is Fiji's only high-elevation lake. This study examined a lacustrine sediment core to explore the lake's potential as a palaeoenvironmental archive through the Late Holocene. Dating reveals no simple age–depth relationship due to sediment age-reversals. However, phases of fire activity are evidenced by two distinct charcoal bands. Catchment burns were probably related to significant ENSO-driven drought, although fire ignition by volcanic eruptions on Taveuni cannot be ruled out. Above the dominant charcoal band, the sediment profile exhibits notable positive shifts in organic matter, bulk density, δ¹³C, and C:N ratio. These peaks suggest a phase of accelerated catchment erosion, possibly triggered by post-burn instability. We introduce a conceptual model to explain the influence of sedge peat swamps on lake sedimentation processes. Surrounding sedge-dominated peatlands have extensively encroached Lake Tagimaucia. Floating peat mats, gradually accumulating through time, act as a repository of organic material that is stored directly on the lake surface. Episodes of drought and fire release old organics directly into the lake itself, probably contributing to the complex chronological sequence in the Late Holocene stratigraphy.

The anchialine ecosystem, comprised of coastal landlocked habitats containing brackish water, experiences tidal fluctuations due to simultaneous underground connections with the sea and terrestrial aquifer system. Anthropogenic impacts have led to substantial habitat degradation and loss, potentially making the anchialine ecosystem and its biota one of Hawai‘i’s most threatened. Prior analyses of mitochondrial (mtDNA) cytochrome oxidase subunit I (COI) sequences from the Hawaiian anchialine atyid shrimp Halocaridina rubra revealed a potential cryptic species complex with strong regional endemism. This study hypothesized that a Halocaridina population discovered in 2018 in southeast O‘ahu, an area with no historically documented anchialine habitats but where a specimen was collected in 1998, represents a unique lineage or genetic group endemic to the region. Comparison of newly generated mtDNA COI sequences to previous ones identified the population as belonging to the South O‘ahu lineage of Halocaridina. However, fixed mutations and significant genetic differentiation distinguish it from the closely related ‘Ewa genetic group of southwest O‘ahu. Given this, we propose the new Maunalua genetic group for Halocaridina from southeast O‘ahu, with an apparent split between groups occurring at approximately the Holocene-Pleistocene Epoch boundary, corresponding well to the geological age of where the new population was discovered. Notably, the 1998 specimen shared the same distinctive coloration as the Maunalua and ‘Ewa genetic groups, implying inclusion within the South O‘ahu lineage. Conservation efforts should consider the currently recognized 15 Halocaridina genetic groups since they represent unique units from all others in both their genetics and geographic distribution.

Acoustic communication in the form of songs is a learned behavior in oscine that can be passed down from one generation to the next through cultural transmission. Over time songs can change when populations become isolated from one another, creating dialects that are distinct to a population. Habitat fragmentation is an isolating mechanism that can influence differences in songs between populations when there is little to no connectivity between fragments and fragment size can influence diversity of song traits. We characterized and analyzed songs of the ‘ōma‘o (Myadestes obscurus) in a naturally fragmented forest to determine how landscape variables influenced song differences between populations. We chose five fragments of different sizes and isolation to record songs of the ‘ōma‘o. We performed a correlation test to evaluate whether there was a relationship between fragment size and total syllables, and between unique syllables and degree of isolation. We also conducted a Mantel test to determine if geographic distance had an influence on song similarity. Our results indicated that songs from larger fragments tended to have higher syllable diversity, but neither connectivity nor distance was related to the number of unique or shared syllables found within a fragment, respectively. Overall, the results indicated that ‘ōma‘o songs are highly variable at the individual level and that there may be little to no syllable sharing within and among populations.

Since human settlement approximately 2,000 years ago, Pacific Island nutrient cycles have been increasingly modified. Modern agricultural intensification has resulted in further changes in the island nutrient flows. Country scale agricultural land nutrient (nitrogen, phosphorus, and potassium) budgeting in Tonga, Fiji, Samoa, Kiribati, and Tuvalu were calculated from FAO country statistic data (1964–2018). Nutrient input data from birds, atmospheric dust, and rainfall and human waste were calculated from literature values. Overall, there are nutrient imbalances in all countries and agricultural lands are exporting nitrogen, phosphorus, and potassium. The budgeting calculations did not consider nutrient losses via erosion, leaching and run-off or denitrification, and the net nutrient fluxes may well be greater than reported. The use of animal and human waste would help off-set nutrient imbalances, but additional macro- and micro-nutrients would need to be added for balanced plant nutrition and soil carbon sequestration. While increasing fertiliser inputs will improve the nutrient balance and potential primary productivity, trade-offs such as nutrient losses will need to be considered. Improving nutrient budgets would need a farming systems approach, whereby the use of cover crops, crop rotations and legumes would augment the fertiliser applications.