West Hawaii Research Articles

Monitoring Coffee Leaf Rust (Hemileia vastatrix) on Commercial Coffee Farms in Hawaii: Early Insights from the First Year of Disease Incursion

Coffee leaf rust (CLR, Hemileia vastatrix) is considered the most damaging coffee disease worldwide, causing reduced yields and even plant death. CLR was detected in Hawaii for the first time in 2020, and quickly spread across the state. We initiated a CLR monitoring program in Kona, West Hawaii Island, to track the spread of this new invasive disease across a broad elevational gradient. The goals of the program were to assist growers in the early detection of CLR, to characterize patterns of disease incidence across the region, and to collect information on farm agronomics, management practices, and costs to apply fungicides, all of which can be used to develop Integrated Pest Management (IPM) strategies for this pathogen. We monitored 30 coffee lots in Kona, located between 204 and 875 m elevation. Average CLR incidence remained below 4% early in the season and increased to 36% during harvest. We observed no significant difference in CLR incidence between low-, mid- and high-elevation farms. A significant reduction in the number of leaves per branch was observed at the end of the harvest season, and a significant negative correlation was found between the number of leaves per branch and maximum CLR severity. Mean disease incidence and mean severity were observed to have a significant positive correlation. Incidence increased above threshold levels (5%), despite most growers applying preventative fungicides 3–10 times throughout the season, suggesting that improved coverage and timing of applications is needed along with the addition of systemic fungicides. Our study provides the first insights into CLR disease patterns under the unique and variable conditions under which Hawaiian coffee is grown, and will aid in the development of IPM programs that can be used to sustain Hawaii’s coffee industry under this new threat.

Impacts of pollution, fishing pressure, and reef rugosity on resource fish biomass in West Hawaii.

Human activities and land-use drivers combine in complex ways to affect coral reef health and, in turn, the diversity and abundance of reef fauna. Here we examine the impacts of different marine protected area (MPA) types, and various human and habitat drivers, on resource fish functional groups (i.e., total fish, herbivore, grazer, scraper, and browser biomass) along the 180 km west coast of Hawaii Island. Across survey years from 2008 to 2018, we observed an overall decrease in total fish biomass of 45%, with similar decreases in biomass seen across most fish functional groups. MPAs that prohibited a combination of lay nets, aquarium collection, and spear fishing were most effective in maintaining and/or increasing fish biomass across all functional groups. We also found that pollution, fishing, and habitat drivers all contributed to changes in total fish biomass, where the most negative impact was nitrogen input from land-based sewage disposal. Fish biomass relationships with our study drivers depended on fish functional grouping. For surgeonfish (grazers), changes in biomass linked most strongly to changes in reef rugosity. For parrotfish (scrapers), biomass was better explained by changes in commercial catch where current commercial fishing levels are negatively affecting scraper populations. Our observations suggest that regional management of multiple factors, including habitat, pollution, and fisheries, will benefit resource fish biomass off Hawaii Island.

Dust on a Hawaiian volcano: A regional model using field measurements to estimate transport and deposition

AbstractThe western slopes of Hawaii's Mauna Kea volcano are mantled by fine‐grained soils, the record of volcanic airfall and eolian deposition. Where exposed, strong winds transport this sediment across West Hawaii, affecting tourism and local communities with decreased air and water quality. Operations on US Army's Ke'amuku Maneuver Area (KMA) have the potential to increase dust flux from these deposits. The USGS established 18 ground monitoring sites and sampling locations surrounding KMA. For over 3 years, each station measured vertical and horizontal dust flux, while co‐located anemometers measured wind speed and direction. We used these datasets to develop a parsimonious regional model for dust supply and transport to assess whether KMA is a net dust sink or source.We found that dust transport is most highly correlated with threshold wind speeds of 8 m/s. We used this value as the regional average threshold wind speed for dust entrainment. Using a model that partitions measured horizontal dust flux into inward‐ and outward‐directed components, we estimate that KMA is currently a net dust sink. Geochemical analysis of dust samples illustrates that local organics and carbonate make up 64% of dust mass, the remainder being volcanic silt and fine sand. Measured vertical dust deposition rates of 0.006 mm/yr are similar to 0.004 mm/yr of deposition predicted from taking the divergence of dust across KMA's boundary. These rates are low compared with pre‐historic rates of ~0.2–0.3 mm/yr, from radiocarbon dating of buried soils.KMA's soils record persistent deposition over millennia, at rates that imply episodic dust storms. Such events created a soil‐mantled landscape in the middle of a largely Pleistocene rocky landscape. A substantial portion of fine‐grained soils in other leeward Hawaiian Island landscapes may have formed from similar eolian deposition, and not direct weathering of parent rock. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Trophic designation and live coral cover predict changes in reef-fish community structure along a shallow to mesophotic gradient in Hawaii

Reef-fish community structure and habitat associations are well documented for shallow coral reefs ( 30 m). We documented the community structure of fishes and seafloor habitat composition through visual observations at depth intervals from 3 to 50 m in West Hawaii. Community structure changed gradually with depth, with more than 78% of fish species observed at mesophotic depths also found in shallow reef habitats. Depth explained 17% of the variation in reef-fish community structure; live coral cover explained 10% and prevalence of sand accounted for 7% of the fitted variation indicating that depth-related factors and coral habitat play a predominant role in structuring these communities. Differences in community structure also appear to be linked closely with feeding behavior. Trophic designation accounted for 31% of the fitted variation, with changes in herbivore abundance accounting for 10% of the variation. These findings suggest that changes in reef-fish community composition from shallow to mesophotic environments are largely influenced by trophic position, coral habitat and indirect effects of depth itself.

Chlorofluorocarbon apparent ages of groundwaters from west Hawaii, USA

Summary The volcanic coastal aquifers of west Hawaii supply drinking water to the area’s residents and nutrient-rich groundwater discharge to the nearby oligotrophic coastal waters. Despite the societal and ecological importance of the water in these aquifers, very little is known about the ages and recharge areas of the groundwater. We therefore determined aquifer recharge areas and groundwater residence times by sampling 18 locations for the oxygen and hydrogen isotopic composition of groundwater and chlorofluorocarbon (CFC) apparent groundwater ages. We sampled water supply wells, coastal wells, and coastal ponds. We applied a δ 18 O/altitude gradient and well-established lapse rates to find that groundwater recharge predominantly occurs in the area’s maximum rainfall zone. Furthermore, the isotopic data suggest that fog drip contributes to aquifer recharge. A single-water source model yielded recharge years ranging from the mid-1960s to mid-1980s for ten samples (56% of samples). Alternatively, a simple binary mixing model, with one water source recharging before1940 and the other after 1940, indicated that 14 samples (78% of samples) contained young water that recharged the aquifer between the mid-1970s and mid-1980s. We also find that CFCs can be used to distinguish between water originating from different aquifers in the area.

What makes a “successful” marine protected area? The unique context of Hawaii′s fish replenishment areas

In 1998, in order to combat the degradation of yellow tang populations on the west coast of Hawaii Island, fish replenishment areas (FRAs) were established prohibiting aquarium fishing along more than thirty percent of the coastline. Unlike other marine management approaches in Hawaii, which have largely been controversial, fraught with confusion over regulations, inadequately enforced, and lacking public support, these FRAs have been lauded as a marine conservation success, with wide-ranging support and evidence of rapid replenishment of the yellow tang population. In order to better understand the contextual factors contributing to the success of the West Hawaii FRAs, this research explores the following questions: (1) What factors documented in the literature on marine protected areas (MPAs) have been demonstrated to contribute to or inhibit MPA success internationally; (2) which of these factors do the FRAs of West Hawaii exhibit; and (3) are there additional factors that may have contributed to their wide acceptance and success? Common factors contributing to MPA success are determined through a synthesis of the literature. These include: level of community engagement, socioeconomic characteristics, ecological factors, MPA design, governance, and enforcement. The outcomes of West Hawaii′s FRAs are examined in the context of these factors. While the common factors agreed upon in the literature were key to the success of the FRAs, additional contextual factors such as the unique nature of the aquarium fishery and its social marginalization also played a vital role.

Persistent spatial patterns of recruitment in a guild of Hawaiian coral reef fishes

We herein describe a long-term (22 consecutive yr, 1990 to 2011) time series of recruitment surveys for a guild of coral-sheltering fishes at 7 to 12 sites along a 26 km section of the west coast of Hawaii Island. For arc-eye hawkfish, the numerically dominant species, recruit- ment (defined as the contribution of young-of-year to the benthic population within several months after settlement from the water column) varied 7-fold among years averaged over sites. Nonetheless, recruitment also differed spatially, with sites along the Kohala Peninsula comprising a high recruitment group. Spatial differences were persistent (some sites predictably low, others predictably high) and generally lacked demonstrable variation over time. Complementary em - pirical data suggested that post-settlement processes (predation, interspecific competition) also affected recruitment. A dispersal model combined with currents from an oceanic circulation model (Hybrid Coordinate Ocean Model, HYCOM) was used to simulate the spatial patterns of settlement by larvae released throughout the main Hawaiian Islands. These simulations generally agreed with observed spatial patterns of recruitment. Greater recruitment was also predicted near geomorphological features (headlands) on Hawaii Island most influenced by the flow of surface eddy currents generated by prevailing E-NE trade winds. Empirical data and simulations together suggest that the headlands of west Hawaii Island likely enhance recruitment by intercepting or concentrating larvae at greater rates, but that post-settlement processes dampen variations in settlement. We suggest that habitat geomorphology should be considered in the criteria used to select sites for no-take Marine Protected Areas at Hawaii Island.

Terrigenous sediment impact on coral recruitment and growth affects the use of coral habitat by recruit parrotfishes (F. Scaridae)

Some major anthropogenic stressors have impacts that occur at infrequent, unpredictable intervals; their effects are difficult to evaluate in a timely manner unless space is substituted for time. In this paper we substitute space for time along an environmental gradient that aliases a predicted temporal response to habitat restoration. We herein describe a 3-year study that combined field experiments and descriptive surveys of a fringing reef at Pelekane Bay, west Hawaii, along a sedimentation gradient from an intermittent stream that episodically discharges from the Kohala Watershed. This degraded watershed is now being restored by grazer exclusion, habitat engineering, and replanting of native flora. Sediment traps, arrays of settling plates, marked branches of endemic finger coral Porites compressa, together with surveys of benthic composition, densities of recruits of economically important parrotfishes, and the relative use of corals by fish recruits, were evaluated during the summers of 2010–2012. As expected, sediment accumulation rate decreased while all coral metrics and the densities, use, and preference of corals by recruit fishes generally increased with distance from the point of sediment discharge. Proportionate abundances of recruit through large adult-sized parrotfishes, overlayed on distributions (mapped by separate study) of sediment impact, allowed us to estimate, as an example, the amount and value of parrotfish rersources that are being unrealized because of sediment impacts on recruit parrotfish. Our Pelekane Bay case study thus illustrates how “space-for-time” substitution can be efficiently applied in an evaluation of potential watershed reclamation of reef resources—at a time considerably prior to likely temporal responses of the reef and its resources to watershed restoration.

Evaluating marine protected areas for managing marine resource conflict in Hawaii

Abstract Conflict surrounding commercial fisheries is a common phenomenon when diverse stakeholders are involved. Harvesting reef fish for the global ornamental fish trade has provoked conflict since the late 1970s in the State of Hawaii. Two decades later the state of Hawaii established a network of marine protected areas (MPAs) on the west coast of the island of Hawaii (“West Hawaii”) to protect and enhance the fish resources and alleviate conflict between stakeholders, principally between commercial dive tour operators and aquarium fishers. The perceptions held by these stakeholders on West Hawaii and Maui were evaluated to understand how MPAs influenced conflict dimensions, as the former location had a well-established MPA network designed to alleviate conflict, while the latter did not. This was accomplished by analyzing the following questions: (1) perceptions about the effectiveness of MPAs to alleviate conflict and enhance reef fish; (2) perceived group encounters and threats to coral reefs; (3) willingness to encourage fishing; and (4) value orientations toward the aquarium fish trade. The results indicate the MPAs in West Hawaii were moderately effective for alleviating conflict, encounters between stakeholders occurred on both islands, dive operators strongly opposed commercial fishing and perceived aquarium fishing as a serious threat to the coral reef ecosystem, and polarized value orientations toward the aquarium fish trade confirms pervasive social values conflict. The conflict between these groups was also asymmetrical. MPAs are inadequate for resolving long term conflict between groups who hold highly dissimilar value orientations toward the use of marine resources. Future marine spatial planning and MPA setting processes should include stakeholder value and conflict assessments to avoid and manage tensions between competing user groups.

Evaluating ontogenetic patterns of habitat use by reef fish in relation to the effectiveness of marine protected areas in West Hawaii

Identifying habitats important to vulnerable life stages of reef fish is an important goal for the effective design and management of Marine Protected Areas (MPAs). However, data on habitat requirements for most fish species are limited. Using a benthic habitat map that characterized reef habitats on the island of Hawaii , we examined ontogenetic patterns of habitat use by each of the life stages of endemic (i.e., Ctenochaetus strigosus; Ctenochaetus hawaiiensis), non-targeted species (i.e., Acanthurus nigrofuscus; Chromis agilis; Thallasoma duperrey; Paracirrhites arcatus) and targeted aquarium fish species (Zebrasoma flavescens; C. strigosus; C. hawaiiensis; Chaetodon multicinctus) in relation to the effectiveness of existing MPAs designed to replenish aquarium fishes targeted by the aquarium trade. Our study empirically demonstrates that many species shift habitats ontogenetically while others remained in the same habitats as they matured. And among those that shifted habitats, depending on species, adults shifted either to more structured (branching coral in mid-depth aggregate and boulder habitats in 5 to 11m depths) or to less structured substrates (shallow turf-rich boulder habitats in 0 to 11m depths). In addition, this study shows how the spatial characteristics of the MPA (i.e., reef size) may be important to reef fish assemblages and ultimately the effectiveness of MPAs to replenish protected ornamental fishes. It is therefore critically important that the management and future design of MPAs provide sufficient diversity and quantities of habitats for all life stages of managed species in order to ensure the replenishment necessary to satisfy their conservation needs and management goals.

Fisher behaviour influences catch productivity and selectivity in West Hawaii's aquarium fishery

Abstract Stevenson, T. C., Tissot, B. N., and Dierking, J. 2011. Fisher behaviour influences catch productivity and selectivity in West Hawaii's aquarium fishery. – ICES Journal of Marine Science, 68: 813–822. In 1999, marine protected areas (MPAs) were implemented along the west coast of the Big Island of Hawaii, closing ∼35% of the coastline to aquarium fishing. Catch per unit effort and total catch of the most commonly targeted fish, yellow tang (Zebrasoma flavescens), have increased since the implementation of the MPAs, yet its abundance has declined by 45% in areas open to aquarium fishing between 1999 and 2007. How effort allocation, harvesting efficiencies, and job satisfaction influence catch productivity and selectivity in West Hawaii's aquarium fishery are investigated, and how these dynamics explain the discrepancy between catch rates and relative abundance for yellow tang is discussed. Cross-sectional fisher questionnaires, semi-structured fisher interviews, and in situ and ex situ catch analyses were performed. The results indicate that fishers dive deeper when reef fish recruitment is perceived as weak, increase harvest efficiency with larger fishing teams, and intensively harvest “coral-friendly” reef fish to supply the global aquarium fish trade. Experienced fishers were less likely to exit the fishery, and job satisfaction was high despite declining fish stocks. These findings may help explain harvesting efficiencies and fleet investment, underscore the importance for evaluating fisher behaviours, and have potential management implications for other aquarium fisheries.

Differential movement patterns and site fidelity among trophic groups of reef fishes in a Hawaiian marine protected area

We tracked the long-term movements of 70 parrotfishes, surgeonfishes and goatfishes captured inside a small (1.3 km2) marine protected area (MPA: Kealakekua Bay Marine Life Conservation District, Hawaii) by implanting them with small transmitters and deploying underwater monitoring devices inside the bay and along 100 km of the adjacent west Hawaii coastline. Individual fish were detected inside Kealakekua Bay for up to 612 days but many were detected for much shorter periods (median = 52 days). There were species-specific differences in the scale of movements and habitats used, but most fish utilized between 0.2 and 1.6 km of coastline, and individuals of each species showed some degree of diel habitat shift. A wide variety of reef fishes captured inside the MPA swam back and forth across an MPA boundary intersecting continuous reef (i.e., this boundary was porous to reef fish movements), but only 1 of 11 species tagged crossed a wide sandy channel inside Kealakekua Bay suggesting that this feature may function as a natural barrier to movements. Results indicate relatively small MPAs (<2 km of coastline) could provide effective, long-term protection for multi-species assemblages of reef fishes provided that boundaries are situated along major habitat breaks (e.g., large sand channels between reefs) that may serve as natural barriers to reef fish movements. It is crucial that a multi-species approach be used when assessing MPA effectiveness.

Hawaiian Islands Marine Ecosystem Case Study: Ecosystem- and Community-Based Management in Hawaii

The Hawaiian Islands comprise a large and isolated archipelago that includes the largest reef area in the United States. Managing nearshore fisheries in this archipelago is a major challenge compounded by the difficulty of coordinating multiple agencies to provide governance across a broad series of islands with substantial social and political differences. There has been interest in, and progress toward, key elements of ecosystem-based management (EBM) in Hawaii, including a network of MPAs and community-based co-management. However, progress has been slow and largely driven by increased attention to the risks facing coral reef ecosystems, enabling both legislation and emergence of local engagement in fishery issues. Key elements of EBM in Hawaii include enhanced coordination among multiple agencies, establishment of place-based and community-based (or Hawaiian ahupua‘a’-based) co-management, and acquisition of data on both the ecology of the nearshore system and the role of human impacts for use in management decisions. The development of community-based co-management and an MPA network along the western Kohala-Kona coast of the island of Hawaii (West Hawaii) illustrates a unique approach demonstrating an incremental approach toward EBM. Nonetheless, there are major challenges to scaling up the West Hawaii model to other islands within the state. These challenges include (1) the limited extent of community involvement, as well as legislative and administrative support, of community-based co-management and MPAs, (2) the complexity of conflicts that develop on more populated islands with diverse stakeholders, (3) weak enforcement of fishing regulations, and (4) whether synergy among federal, state, and local governments, nongovernmental organizations, and the scientific community will be sustainable.

Ontogenetic patterns of habitat use by reef-fish in a Marine Protected Area network: a multi-scaled remote sensing and in situ approach

A network of Marine Protected Areas (MPAs) on the west coast of the island of Hawaii (West Hawaii) has been shown to vary in its effectiveness to replenish depleted aquarium fish stocks. To determine the abundance and distribution of habitats needed to better design and manage MPAs in Hawaii, underwater video transects, remote sensing data and a benthic classification scheme were combined to develop a map of reef habitats previously identified as important to the life history of aquarium fish and other reef species. Using these maps, an assessment was conducted to quantify habitat use by different life history stages of the most commonly live-caught aquarium fish, the yellow tang Zebrasoma flavescens, in existing MPAs. Rugosity, small reef features (i.e. percent cover of dominant reef species) and the abundance and size of fish were quantified in 115 circular plots to determine the accuracy of mapping efforts and the distribution of fish life history stages across the reef in 4 MPAs. Visual classification and mapping of habitat types was 93% accurate and consistent with percent cover of substrates quantified at the quadrat level. The different life history stages of yellow tangs were distributed along distinct habitat types in all of the MPAs examined. New recruits and juveniles of the yellow tang showed similar patterns of habitat use among sites and were associating with coral-rich areas and patches of the finger coral Porites compressa. In contrast, the distribution and abundance of adults varied greatly within and among sites. The development of a ground-truthed habitat map allowed a holistic examination of habitat use by yellow tang, including most life history stages, which provides key information for the design of MPAs and the advancement of ecosystem-based management.

Bet-hedging strategies, agricultural change, and unpredictable environments: historical development of dryland agriculture in Kona, Hawaii

It is argued that current models of agricultural change are overly focused on productive increases. Risk management strategies, practices that can be critical to the long-term survival of a given agronomic system, warrant a more prominent role. Neo-Darwinian theory, and the bet-hedging model in particular, offers a way to evaluate both kinds of agronomic change within a single theoretical paradigm, as well as a means of assessing the long-term outcomes of variant agronomic strategies. The bet-hedging model is used herein to assess agricultural change in an unpredictable Hawaiian environment, the Kona District of central West Hawaii. A fine-grained record of agronomic change from one of the region’s more productive areas is compared with patterns from the region at large. The analysis shows that variance minimizing (or risk management) strategies were initiated by 1450 AD, if not earlier, and occurred in even the most productive localities. Innovations in gardening architecture, novel cultivation practices and changes in the scale of agronomic integration, are argued to have been effective in reducing the impact of environmental variance. Later in time (after 1650 AD) there was a shift in emphasis to productive maximizing strategies, with implications for the region’s economic and socio-political stability.

Teaching Japanese-American Incarceration

FEW EVENTS IN AMERICAN HISTORY are so universally deplored as the incarceration of Japanese Americans during World War II. The United States government has acknowledged the error and the injustice that resulted with an official Presidential apology and a Congressional disbursement of reparations to the victims of the incarceration policy. The decision, its implementation, and its consequences for various individuals have been the topics for a variety of historical accounts, museum exhibits, documentary films, short stories, novels, plays and movies. Moder observers are appalled that the United States enacted such an inhumane, unjust and unnecessary policy, yet most citizens at the time thought the policy appropriate, necessary, and humane. The policy was supported overwhelmingly by the American people and the few who opposed the policy were considered unpatriotic and their reasoning bizarre. Most people thought internment of enemy aliens was a normal precaution in wartime situations, made particularly appropriate given the Japanese attack on Pearl Harbor. The residence of Japanese immigrants near military facilities on the west coast and Hawaii seemed to make the

Further Species of the Lichen Genus Staurolemma (Collemataceae, Lichenized Ascomycetes)

The hitherto monospecific European genus Staurolemma is shown to contain two more species, S. dussii (Vain.) P. M. J~rg. & Henssen in subtropical America (West Indies and Hawaii), usually previously included in Lempholemma, an unrelated genus that has different ascomata (pycnoascocarpia), asci, and hymenial reactions and the closely related Hawaiian endemic, S. weberi Henssen & P. M. J~rg. sp. nov. A key to the simple-spored genera of Collemataceae is presented. As shown recently (Jergensen & Henssen 1993), the species usually called Physma omphalarioides (Anzi) Zahlbr. (Fig. 1B, D) should be placed into a genus of its own, Staurolemma Korb. This is basically a Mediterranean species with outlying localities in Macaronesia and coastal, central Norway. It is therefore unexpected and surprising to discover further species in this genus from subtropical parts of America, North of the Equator. MATERIAL AND METHODS This study is based on the herbarium material cited below; for sectioning a freezing microtome has been used to produce 18-22 pm thick sections that were mounted in lactic/glycerine with cotton-blue (LB). For studies of the iodine reaction, Lugol's solution was added to sections and squash preparations without pretreatment with KOH.

Developing talent in high school students: An integrative model

Talented students are being quietly neglected in many schools (Ross, 1993). In this article two staff members and two students describe the program of the West Hawaii Explorations Academy, a restructuring effort of Konawaena High School housed at the Natural Energy Laboratory of Hawai'i The students tell about their previous school experiences, the work they have done at the academy, and their outlook for the future. The university liaison and program director conclude by discussing the role of the environment and the importance of expert mentors in talent exploration and development.

Silicon deficiency and the adaptation of tropical rice ecotypes

Although silicon (Si) is found at much higher concentrations in healthy rice crops than N, P or K, it has received far less study, particularly for upland rice. There are few reports on the existence, causes, and effects of varying Si supplies in different environments. Chemical analyses of soil, water and plant tissue samples from experiments grown on a typical weathered, acidic upland soil in Colombia found concentrations of Si which were 80-90% lower than those in a typical lowland environment. These results corroborate published findings from West Africa and Hawaii, and lend support to a conclusion that acid-soil upland rice environments in the tropics tend to be deficient in Si, increasing disease damage, among other effects. Critical values for diagnosis of Si deficiency in soils, water and rice husk tissue are suggested. These are reasonably consistent with, but extend the application of previously published values derived from lowland rice studies to upland environments, and use simpler sampling and analysis methods. A strong correlation was found (r = -0.91) between high husk Si concentration and low husk discoloration disease damage, among diverse rice genotypes grown in the uplands. These genotypic differences were mainly explained by their ecotypic affinities: those belonging to the tropical japonica ecotype exhibited 93% higher husk Si concentrations than indica ecotypes (ecotypic means of 23 vs. 12 mg kg 1 ). This is consistent with a hypothesis that the tropical japonicas may have adapted to Si deficiency in their native upland environment by evolving mechanisms to attain relatively higher tissue Si concentrations than indicas, which are believed to have evolved in the lowlands, where the Si supply is generally ample. Increased understanding of Si-mediated disease resistance in different rice environments and ecotypes could help breeders combine the high yield potential of indica types with the more durable disease resistance of the japonicas, and could contribute to the development of integrated disease management strategies.

Coral ages and island subsidence, Hilo drill hole

A 25.8‐m‐thick sedimentary section containing coral fragments occurs directly below a surface lava flow (the ∼1340 year old Panaewa lava flow) at the Hilo drill hole. Ten coral samples from this section dated by accelerator mass spectrometry (AMS) radiocarbon and five by thermal infrared multispectral scanner (TIMS) 230Th/U methods show good agreement. The calcareous unit is 9790 years old at the bottom and 1690 years old at the top and was deposited in a shallow lagoon behind an actively growing reef. This sedimentary unit is underlain by a 34‐m‐thick lava flow which in turn overlies a thin volcaniclastic silt with coral fragments that yield a single 14C date of 10,340 years. The age‐depth relations of the dated samples can be compared with proposed eustatic sea level curves after allowance for island subsidence is taken. Island subsidence averages 2.2 mm/yr for the last 47 years based on measurements from a tide gage near the drill hole or 2.5–2.6 mm/yr for the last 500,000 years based on the ages and depths of a series of drowned coral reefs offshore from west Hawaii. The age‐depth measurements of coral fragments are more consistent with eustatic sea levels as determined by coral dating at Barbados and Albrolhos Islands than those based on oxygen isotopic data from deep sea cores. The Panaewa lava flow entered a lagoon underlain by coral debris and covered the drill site with 30.9 m of lava of which 11 m was above sea level. This surface has now subsided to 4.2 m above sea level, but it demonstrates how a modern lava flow entering Hilo Bay would not only change the coastline but could extensively modify the offshore shelf.