Coral reef ecosystems are exposed to a range of environmental forcings that vary on daily to decadal time scales and across spatial scales spanning from reefs to archipelagos. Environmental ...variability is a major determinant of reef ecosystem structure and function, including coral reef extent and growth rates, and the abundance, diversity, and morphology of reef organisms. Proper characterization of environmental forcings on coral reef ecosystems is critical if we are to understand the dynamics and implications of abiotic-biotic interactions on reef ecosystems. This study combines high-resolution bathymetric information with remotely sensed sea surface temperature, chlorophyll-a and irradiance data, and modeled wave data to quantify environmental forcings on coral reefs. We present a methodological approach to develop spatially constrained, island- and atoll-scale metrics that quantify climatological range limits and anomalous environmental forcings across U.S. Pacific coral reef ecosystems. Our results indicate considerable spatial heterogeneity in climatological ranges and anomalies across 41 islands and atolls, with emergent spatial patterns specific to each environmental forcing. For example, wave energy was greatest at northern latitudes and generally decreased with latitude. In contrast, chlorophyll-a was greatest at reef ecosystems proximate to the equator and northern-most locations, showing little synchrony with latitude. In addition, we find that the reef ecosystems with the highest chlorophyll-a concentrations; Jarvis, Howland, Baker, Palmyra and Kingman are each uninhabited and are characterized by high hard coral cover and large numbers of predatory fishes. Finally, we find that scaling environmental data to the spatial footprint of individual islands and atolls is more likely to capture local environmental forcings, as chlorophyll-a concentrations decreased at relatively short distances (>7 km) from 85% of our study locations. These metrics will help identify reef ecosystems most exposed to environmental stress as well as systems that may be more resistant or resilient to future climate change.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Nutrient sources to coastal waters with coral reefs are not well-characterized. This study documented spatial distributions of nutrients within coastal waters along two developments with coral reefs, ...and identified nutrient sources through nutrient mixing plots, δ15N measurements in macroalgal tissue, and NO3− stable isotope mixing models. Nutrients decreased from fresh groundwaters to offshore waters, with some surface waters higher in concentrations than benthic ones. Conservative and non-conservative mixing between fresh and ocean waters occurred, the latter suggestive of local nutrient sources and biological removal. δ15N in macroalgal tissue and NO3− concurred that fresh groundwater, ocean water, and fertilizers were dominant nutrient sources. Benthic salinity and NO3− + NO2− concentrations illustrated that submarine groundwater discharge delivered nutrients to reefs in pulses ranging from minutes to days. Information generated from this study is imperative for developing management actions to improve water quality and make coral reefs more resilient to stressors.
•Mixing plots, isotopes, and sensors assessed nutrient patterns on resorts' coral reefs.•Nutrients decreased from fresh groundwaters to offshore waters in resorts' watersheds.•Nutrients mixed conservatively and non-conservatively between fresh and ocean waters.•Groundwater, ocean, and fertilizer were dominate nutrient sources to coral reefs.•Submarine groundwater discharge delivered nutrients to reefs in pulses of min to days.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Following the recent 2014–2017 global coral bleaching event, managers are seeking interventions to promote long-term resilience beyond monitoring coral decline. Here, we applied a spatial approach to ...investigate one potential intervention, mapping areas where local management could build coral reef resilience using herbivore management. Although herbivore management is a top recommendation in resilience-based management, site-specific attributes are thought to affect its success, and thus strategizing placement and design of these areas are crucial. Using Marxan, we mapped and prioritized potential Herbivore Management Areas (HMAs), where herbivores are protected but other types of fishing are allowed, in the main Hawaiian Islands. Through four scenarios, we found multiple hotspots along the west coast of Hawai‘i Island and around the islands of Moloka‘i, Lana‘i, Maui, and Kaho‘olawe where HMAs may have the best chance for success based on habitat, ecologically critical areas, life history, and social considerations. We further analyzed top results and found that a subset of characteristics including habitat types, biomass of herbivore functional groups, and temperature variability were significantly different from surrounding areas and thus contain potential drivers for selection. This unique approach can serve as an example for coral reef management in Hawai‘i, on other Pacific Islands, and beyond, as it provides practical guidance on how to apply a resilience-building tool at a local level, incorporating site-specific biological and socioeconomic considerations.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Pacific remote island areas (PRIA) are sovereign United States unincorporated and unorganized territories not falling within the jurisdiction of any other US territory or State (GAO 1997; US DOI ...2003). There are eight PRIA and all are under the jurisdiction of the US Department of Interior (DOI). All are low reef islets or atolls in the central Pacific Ocean. Table 15.1 and Fig. 15.1 present the size, location, and regional geography of the five PRIA that are the primary focus in this chapter: Baker and Howland Islands in the Phoenix Islands ; and Jarvis Island, Kingman Reef, and Palmyra Atoll in the Line Islands. All five are located between Hawai’i and Samoa and are National Wildlife Refuges (NWR) administered by the US Fish and Wildlife Service (USFWS). The remaining three PRIA: Johnston Atoll NWR, Midway Atoll NWR, and Wake Atoll, are the subject of other chapters in this volume (Chapter 13, Rooney et al.; Chapter 17, Lobel and Lobel). Johnston Atoll is mentioned in this chapter because it is geologically part of the Line Islands archipelago. Wake Atoll, administered by the US.
Air Force, is north of the Republic of the Marshall Islands. Midway Atoll is located at the northwest end of the Hawaiian Islands and is a PRIA because it was excluded from state jurisdiction in the Hawaii Statehood Act of 1959. This chapter covers the cultural, geological, and biophysical characteristics and history of the five PRIA. The following chapter (Chapter 16, Maragos et al.) covers the status, threats and significance of the five PRIA.
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