NOAA scientists quantify coral reef growth to monitor the effects of ocean acidification

by Bernardo Vargas-Ángel
Assemblage of branching and foliose corals at Swains Island, American Samoa (NOAA Photo by James Morioka).

Assemblage of branching and foliose corals at Swains Island, American Samoa (NOAA Photo by James Morioka).

Often referred to as the “rainforests of the sea,” coral reefs are some of the most biologically rich and economically valuable ecosystems on Earth. Most coral reefs occur in warm, shallow, clear waters and are built by stony corals together with other organisms that form hard, calcium carbonate skeletons over decades and centuries.

Underwater photo of coral assemblages at Fagatele Bay, American Samoa (NOAA Photo by Louise Giuseffi).

Underwater photo of coral assemblages at Fagatele Bay, American Samoa (NOAA Photo by Louise Giuseffi).

Scientists at the Coral Reef Ecosystem Program of NOAA’s Pacific Islands Fisheries Science Center are conducting long-term research to monitor the rates at which reef organisms build their calcium carbonate skeletons and how changes in ocean chemistry, particularly ocean acidification, might impact their growth.

Ocean acidification is a global phenomenon in which increasing carbon dioxide in the atmosphere is absorbed into the ocean making the seawater more acidic. The lower pH and higher acidity of the ocean makes it harder for marine creatures, such as shellfish and corals, to build their calcium carbonate shells or skeletons.

CAU assembly unit: a. oblique view, b. side view, and c. in-situ image of deployed CAU unit (NOAA Drawing by Daniel Merritt).

CAU assembly unit: a. oblique view, b. side view, and c. in-situ image of deployed CAU unit (NOAA Drawing by Daniel Merritt).

Throughout the coral reefs of the U.S. Pacific Islands, we are monitoring the production of calcium carbonate using calcification accretion units (CAUs). These underwater units are made of two PVC plates that are placed at specific locations on coral reefs to allow for the recruitment and colonization of crustose coralline algae and hard corals onto the plates. By measuring net accretion, we can determine how much calcium carbonate is produced over a given period of time. Total net accretion on coral reefs can be calculated by measuring the change in weight of CAUs deployed on the reefs for periods of two to three years.

Newly deployed CAU assembly installed at Swains Island, American Samoa.

Newly deployed CAU assembly installed at Swains Island, American Samoa.

CAU plates encrusted with crustose coralline algae after two years of deployment.

CAU plates encrusted with crustose coralline algae after two years of deployment.

We hypothesize that net accretion will vary based on island, region, and habitat—and will change over time. By monitoring net accretion on coral reefs, we will be able to detect changes in calcification rates over time and therefore, assess the effects of ocean acidification.

Spatial distribution and mean carbonate accretion rates derived from CAU deployments by study site (left panel) and island-wide (right panel).

Spatial distribution and mean carbonate accretion rates derived from CAU deployments by study site (left panel) and island-wide (right panel).

A recently published article in the journal PLoS ONE, Baseline Assessment of Net Calcium Carbonate Accretion Rates on U.S. Pacific Reefs, presents a comprehensive baseline of carbonate accretion rates primarily by crustose coralline algae (CCA) on CAU plates deployed on coral reefs at dozens of sites across 11 islands in the central and south Pacific Ocean. The study underscores the pivotal role CCA play as a key reef calcifier and offers a unique perspective to better understand the potential effects of ocean acidification at different scenarios of future ocean chemistry.

CAU plates prepared for processing in the lab show a diverse collection of organisms (a. corralline algae, b. shellfish, c. coral, d. encrusting algae).

CAU plates prepared for processing in the lab show a diverse collection of organisms (a. corralline algae, b. shellfish, c. coral, d. encrusting algae).

Five main conclusions can be gleaned from this study:

Reef at Swains Island, American Samoa (NOAA Photo by Louise Giuseffi)

Reef at Swains Island, American Samoa (NOAA Photo by Louise Giuseffi)

  • Due to the highly variable nature of the carbonate accretion rates, it is expected that coral community responses to ocean acidification will likely vary widely between reef ecosystems, as well as between sites within islands.
  • Crustose coralline algae deposit a highly soluble form of calcium carbonate (CaCO3) known as high-Mg-calcite. Increases in the acidity of ocean water will likely result in lower CCA accretion rates.
  • Under acidified conditions CCA may lose their competitive advantage as the dominant calcifying group of the early reef colonizers, which in turn may have adverse implications for the settlement and development of other important reef calcifying organisms such as corals themselves.
  • Under the projected changes in marine seawater carbonate chemistry (e.g. ocean acidification), the ability of marine calcifying organisms to cope with such changes, and continue offering the ecosystem services they currently provide, will likely be determined by both the magnitude and rate of seawater pH decrease.
  • The combined effects of chronic human impacts, together with decreased pH from ocean acidification, will likely affect reef community structure and therefore carbonate accretion on coral reefs worldwide.

To read the full article go to: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0142196

Vargas-Ángel B, Richards CL, Vroom PS, Price NN, Schils T, Young CW, Smith J, Johnson MD, Brainard RE (2015) PLoS ONE 10(12): e0142196. doi:10.1371/journal.pone.0142196

How can an ecosystem approach be used to address climate change?

By Adel Heenan and Amanda Dillon
Figure 1. Potential pathways for climate driven impacts on fisheries systems. Projected changes in climate and ocean properties (top tier) in response to increased CO2 emissions will directly affect human and natural capital (bottom tier). Changes in these aspects of the ocean will affect fishes and their related ecosystems (second tier) which will amplify through the fishery system, affecting aspects of fishing catch and effort (third tier). This will in turn have national level societal and economic repercussions (forth tier), in addition to influencing the natural and physical capital of individuals and fishing related communities (bottom tier).

Figure 1. Potential pathways for climate driven impacts on fisheries systems. Projected changes in climate and ocean properties (top tier) in response to increased CO2 emissions will directly affect human and natural capital (bottom tier). Changes in these aspects of the ocean will affect fishes and their related ecosystems (second tier) which will amplify through the fishery system, affecting aspects of fishing catch and effort (third tier). This will in turn have national level societal and economic repercussions (forth tier), in addition to influencing the natural and physical capital of individuals and fishing related communities (bottom tier).

The Pacific Islands Fisheries Science Center’s Coral Reef Ecosystem Division (CRED), in collaboration with scientists from 16 international institutions, recently published a paper in the journal Marine Policy that discusses how coastal fisheries management can incorporate considerations of climate change.

The projected impacts of climate change and ocean acidification on fishes and fisheries in the Asia-Pacific region are being documented with increasing frequency. In turn, these impacts will directly and indirectly effect both natural and human capital (Figure 1). The risks posed by climate change need to be assessed in concert with efforts to address pre-existing threats to tropical fisheries—such as overfishing, habitat degradation, pollution, eutrophication, and invasive species. What is needed is an approach to management that can more effectively deal with these pre-existing stresses, while reducing the vulnerability to longer-term climate impacts. The challenges inherent in achieving this management approach is demanding, particularly in the Asia-Pacific, where coastal fisheries are characterized by a lack of data, limited human capacity for effective management, and weak governance.

This paper focuses on an ecosystem approach to fisheries management (EAFM), which is now widely accepted as a potential solution to the current deficiencies in existing management efforts. The activities required to harness the full potential of an EAFM as an adaptation to climate change and ocean acidification include:

  • provision of the necessary expertise to inform all stakeholders about the risks to fish habitats, fish stocks and catches due to climate change,
  • promotion of trans-disciplinary collaboration,
  • facilitating the participation of all key stakeholders,
  • monitoring the wider fisheries system for climate impacts,
  • and enhancing resources and capacity to implement an EAFM.

By using an “ecosystem approach” to address climate and ocean change, developing countries will build resilience to the ecological and fisheries effects of climate change, and will also address the habitat degradation and overfishing that damages the productivity of coastal fisheries.

For more detail, the full paper is available for download here.

Scientists return to Timor-Leste for reef monitoring mission

By Max Sudnovsky

In the early morning on Sept. 16, Molly Timmers, Charles Young, and Max Sudnovsky of the PIFSC Coral Reef Ecosystem Division (CRED) departed Dili, Timor-Leste, on their way to Atauro Island to kick off the first day of a five-week field operation. Timmers, Young, and Sudnovsky, along with Michael Abbey from the NOAA Fisheries Office of International Affairs, Rui Pinto of Conservation International (CI), and Lloyd Lee of Dive Timor Lorasae, spent the next four days in the district of Beloi processing a suite of instruments and installations that had been deployed two years ago by CRED staff to monitor biodiversity and ocean acidification in nearshore coral reef ecosystems of Timor-Leste and removed by Pinto and Lee.

Robert Crean of Compass Charters, Molly Timmers of the PIFSC Coral Reef Ecosystem Division (CRED), Lloyd Lee of Dive Timor Lorasae, Rui Pinto of Conservation International, and Charles Young of CRED arrive on Sept. 16 at Atauro Island, Timor-Leste, on the Lancet, a charter vessel. NOAA photo

Robert Crean of Compass Charters, Molly Timmers of the PIFSC Coral Reef Ecosystem Division (CRED), Lloyd Lee of Dive Timor Lorasae, Rui Pinto of Conservation International, and Charles Young of CRED arrive on Sept. 16 at Atauro Island, Timor-Leste, on the Lancet, a charter vessel. NOAA photo

Scientific equipment gets off-loaded from the Lancet for land-based operations. NOAA photo

Scientific equipment gets off-loaded from the Lancet for land-based operations. NOAA photo

The NOAA team is working with CI Timor-Leste staff, national and district fisheries officers of the Timor-Leste Ministry of Agriculture and Fisheries (MAF), staff from a local scuba dive shop, and local fishers to facilitate retrieval of the suite of monitoring instruments previously deployed in October 2012. The instrumentation includes subsurface temperature recorders (STRs), which are used to assess trends in water temperatures; calcification accretion units (CAUs), which are used to assess rates of reef calcification and accretion; and autonomous reef monitoring structures (ARMS), which are used to assess biodiversity of reef cryptobiota of coral reef ecosystems.

Later during this mission, the team will collect surface and bottom water samples, which can be used to monitor long-term trends in carbonate chemistry (i.e., ocean acidification) and conduct photoquadrat surveys along transects on the seafloor to capture the benthic composition around the site.

This field operation is supported by the U.S. Agency for International Development Timor-Leste Mission, and the NOAA Fisheries Office of International Affairs, in collaboration with MAF and CI Timor-Leste. This collaboration will enable CI, MAF, local dive operators, and community members to build local, institutional, and organizational capacity to continue efforts in long-term coral reef monitoring so that future managers will have scientifically credible observations by which to make informed decisions. The field team is based out of Barry’s Place, a lodge with a business strategy based on the ethics and principles of ecotourism and permaculture.

Michael Abbey of the NOAA Fisheries Office of International Affairs scrapes plates from autonomous reef monitoring structures (ARMS) with a spatula; scrapings will be homogenized in a blender, and subsamples will be preserved in dimethyl sulfoxide for mass genetic sequencing. NOAA photo

Michael Abbey of the NOAA Fisheries Office of International Affairs scrapes a plate that was part of an autonomous reef monitoring structure (ARMS) with a spatula. NOAA photo

Charles Young (middle) briefs Rui Pinto from Conservation International and Lloyd Lee from Dive Timor Lorasae on the protocol for taking still photographs (photoquadrats) to record the benthos at set intervals along two 25-m transect lines. NOAA photo

Charles Young (middle) briefs Rui Pinto from Conservation International and Lloyd Lee from Dive Timor Lorasae on the protocol for taking still photographs (photoquadrats) to record the benthos at set intervals along two 25-m transect lines. NOAA photo

Molly Timmers explains the processing of autonomous reef monitoring structures (ARMS) to Barry Hinton, owner of the lodge Barry's Place, and his two sons Micky and Mardy Hinton. Barry’s Place served as the base of operations for the part of this mission at Atauro Island. NOAA photo

Molly Timmers explains the processing of ARMS to Barry Hinton, owner of Barry’s Place, and his sons. Barry’s Place served as the base of operations for the part of this mission at Atauro Island. NOAA photo

Rui Pinto of Conservation International sorts motile inverts that were found on ARMS. NOAA photo

Rui Pinto of Conservation International sorts motile inverts that were found inside ARMS recovered from a reef off Atauro Island. NOAA photo

Atauro Island is situated approximately 22 nautical miles (41 km) to the north of Dili, on the extinct Wetar segment of the volcanic Inner Banda Arc. This island is 25 km long, 9 km wide, and about 105 km2 in area with a mountainous spine and narrow coastal plains. Two deep straits, the Ombai (5000 m deep) and Wetar (3000 m deep), meet at both the northern and southern ends of the island. The mountains are mostly limestone with some volcanic rock foundations. The highest of them, Manucoco (with an elevation of 995 m) is considered sacred.

Charles Young of CRED processes water samples. NOAA photo

Charles Young of CRED processes water samples. NOAA photo

The Atauro community of approximately 8000 people, mostly subsistence fishers and farmers, live in five districts (or sucos). The main centers of Maquili, Vila, Beloi, and Bequeli sit along the eastern coast, and Macadade rests in the mountains. Small communities live in isolated hamlets along the coast and in the mountains.

The team from NOAA and Conservation International very much appreciates all the support that we have received so far from Barry Hinton and his staff at Barry’s Place, Compass Charters, Lloyd Lee, local fishers, and the community members of Beloi who have stopped by to check out what we have been up to. Obrigadu Barak!

Stay tuned for more updates as the team next heads to Beacou!

The field operations team poses for a photo in Atauro: (left to right): Michael Abbey of the NOAA Fisheries Office of International Affairs, Rui Pinto of Conservation International, Lloyd Lee of Dive Timor Lorase), and Molly Timmers, Max Sudnovsky, and Charles Young of the PIFSC Coral Reef Ecosystem Division.  NOAA photo

The field operations team poses for a photo at Atauro Island: (left to right): Michael Abbey of the NOAA Fisheries Office of International Affairs, Rui Pinto of Conservation International, Lloyd Lee of Dive Timor Lorase, and Molly Timmers, Max Sudnovsky, and Charles Young of the PIFSC Coral Reef Ecosystem Division. NOAA photo

The fastest divers you’ve ever seen: installation of a climate monitoring station at Pagan Island

Text and video by Noah Pomeroy

I wish we could actually move as fast as we do in this video! In reality, this time-lapse video captures a scuba dive that took place on April 23 over about one hour in real time during a recent Pacific Reef Assessment and Monitoring Program (Pacific RAMP) research cruise in the Mariana Archipelago. This video shows the Climate and Ocean Change Team of the PIFSC Coral Reef Ecosystem Division (CRED) establishing a 15-m-deep climate monitoring station at Pagan Island in the Commonwealth of the Northern Mariana Islands (CNMI).

 

This site and other climate monitoring stations feature a variety of instrumentation, including subsurface temperature recorders (STRs), autonomous reef monitoring structures (ARMS), calcification accretion units (CAUs), and bioerosion monitoring units (BMUs). These instruments and monitoring installations provide oceanographic and ecological information about coral reef ecosystems. Seawater temperature is measured by STRs, calcification and bioerosion rates are determined by CAUs and BMUs, and cryptic biodiversity is evaluated by the analysis of invertebrate communities found living within ARMS.

The work at each station involves other activities in addition to the installation of instruments. During this dive, we completed a survey of rugosity, or habitat complexity, to document the physical relief of the reef structure. We also performed a photoquad survey, taking photographs along a transect to document the benthic reef community. Water samples were collected to assess the carbonate chemistry of water at the reef and at the surface above it.

Conducting this much work during one dive requires a lot of pre-dive planning and in-water choreography. Before beginning such a scuba dive, each diver identifies the tasks that he or she will complete and makes sure to have all the necessary tools and instruments. Although the team works to execute the dance as planned, unexpected challenges are common underwater. Heavy surge (the back and forth motion of water due to frequent waves) or a very hard substrate can make installing instruments and conducting a reef survey difficult.

Climate monitoring stations are one component of the broad National Coral Reef Monitoring Plan (NCRMP) of NOAA’s Coral Reef Conservation Program (CRCP). The NCRMP philosophy is to collect a standard suite of oceanographic and ecological information throughout each of NOAA’s jurisdictions to establish baselines and assess temporal and spatial variability in these coral reef ecosystems caused by global climate change and ocean acidification.

Ocean acidification is the changing of the carbonate chemistry of Earth’s oceans due to absorption of carbon dioxide (CO2). This absorption changes their delicate chemical balance, making it difficult for calcifying organisms, such as corals, mollusks, and shellfishes, to produce their carbonate skeletons. Information gathered at climate monitoring stations will be used by CRED staff to examine how the temperature and chemistry of the waters surrounding reefs vary over time and space and how those changes effect the fishes, corals, algae, and other organisms of the coral reef ecosystems at those sites.

The CRED so far has established climate monitoring stations in the CNMI and Guam, at Wake Island, and throughout the Hawaiian Archipelago. In 2015, the CRED will establish stations in American Samoa and at islands and atolls that make up the Pacific Remote Islands Marine National Monument. Support for these climate stations as part of NCRMP comes from the CRCP and the NOAA Ocean Acidification Program.

Four scuba divers from the PIFSC Coral Reef Ecosystem Division are featured in this video: Jeanette Clark, Russell Reardon, Charles Young, and Noah Pomeroy.

 

Researchers complete surveys of coral reef ecosystems around O`ahu

By Bernardo Vargas-Ángel
Panoramic view of Kaneohe Bay, on the eastern coast of O`ahu, as seen from a small boat on Oct. 20 during a two-week mission (SB-13-20) to conduct monitoring surveys of coral reef ecosystems. NOAA photo by Brett Schumacher

Panoramic view of Kane`ohe Bay, on the eastern coast of O`ahu, as seen from a small boat on Oct. 20 during a two-week mission (SB-13-20) to conduct monitoring surveys of coral reef ecosystems. NOAA photo by Brett Schumacher

Members of the PIFSC Coral Reef Ecosystem Division (CRED) recently concluded a two-week deployment on O`ahu, where they conducted surveys of coral reef ecosystems as part of the Pacific Reef Assessment and Monitoring Program (Pacific RAMP) in the main Hawaiian Islands. These shore-based operations (PIFSC small-boat mission SB-13-20) augment the surveys undertaken during the PIFSC research cruise HA-13-04 aboard the NOAA Ship Hi`ialakai, marking the completion of the fifth such research effort by PIFSC in the main Hawaiian Islands. Pacific RAMP, part of the National Coral Reef Monitoring Plan of NOAA’s Coral Reef Conservation Program, is designed to provide a consistent, comparable flow of information to document and report the status and trends of the environmental conditions and living resources of the nation’s coral reef ecosystems in the Pacific.

Paula Ayotte, a member of the fish team at the PIFSC Coral Reef Ecosystem Division, conducts surveys for fish at a Rapid Ecological Assessment site implementing the stationary-point-count (SPC) method. NOAA photo

Paula Ayotte, a member of the fish team at the PIFSC Coral Reef Ecosystem Division, conducts surveys for fish at a Rapid Ecological Assessment site implementing the stationary-point-count (SPC) method. NOAA photo

During the SB-13-20 mission on Oct. 18–Nov. 6, scuba divers conducted Rapid Ecological Assessments (REAs), focusing on the acquisition of data to derive estimates of diversity, relative abundance, biomass, and size-class structure of reef fishes and corals. Divers from the CRED instrumentation team collected data on water temperature, salinity, carbonate chemistry, and other physical characteristics of the reef environment with an assortment of oceanographic monitoring instruments. They also collected water samples and deployed autonomous reef monitoring structures (ARMS) to assess the taxonomic diversity of cryptic invertebrate species on coral reefs and arrays of calcification accretion units (CAUs) and bioerosion monitoring units (BMUs) to assess the effects of ocean acidification on rates of reef carbonate deposition.

Data collected by the scientific staff of this mission contribute to information that provides the scientific basis necessary for sound management of the marine resources of coral reef ecosystems in the main Hawaiian Islands.

Dione Swanson, a member of the benthic team at the PIFSC Coral Reef Ecosystem Division, conducts surveys for corals at a Rapid Ecological Assessment site implementing the belt-transect method. NOAA photo

Dione Swanson, a member of the benthic team at the PIFSC Coral Reef Ecosystem Division, conducts surveys for corals at a Rapid Ecological Assessment site implementing the belt-transect method. NOAA photo

The final count: cruise for monitoring of effects of ocean and climate change in the Northwestern Hawaiian Islands completed

By Chip Young

Scientists from the PIFSC Coral Reef Ecosystem Division (CRED) recently completed a 17-day expedition to the Northwestern Hawaiian Islands, where they conducted coral reef monitoring surveys at Pearl and Hermes Atoll, Lisianski Island, and French Frigate Shoals. These 3 locations are part of the Papahānaumokuākea Marine National Monument and World Heritage Site, the third largest marine protected area on Earth and the largest conservation area in the United States.

This PIFSC research cruise (HA-13-05) aboard the NOAA Ship Hi`ialakai implemented a standardized set of methods for the measurement of fluctuations in the region’s coral reef ecosystems caused by global climate change. NOAA’s National Coral Reef Monitoring Plan (NCRMP) outlines the importance of monitoring changes in temperature and the chemical composition of ocean waters within which the coral reef ecosystems of the United States are found. Coral reefs are fragile biological systems that have been observed to live best in specific ranges of water temperatures and composition parameters. Changes in either of these ranges can cause a coral reef system to malfunction, through problematic processes that are familiar to much of the general public. Such processes, including coral bleaching (a result of increased ocean temperatures) and ocean acidification (a result of a drop in the ocean’s pH), affect the ability of corals and other reef organisms to calcify or “build their houses.” Other potential effects can occur, as well, such as shifts in biogeochemical cycles, shifts in species diversity, and changes in the ocean’s food web.

Jamison Gove and Chip Young of the PIFSC Coral Reef Ecosystem Division deploy oceanographic instrumentation on Sept. 13 at Lisianski Island as part of the recent research cruise to the Northwestern Hawaiian Islands. NOAA photo by Oliver Vetter

Jamison Gove and Chip Young of the PIFSC Coral Reef Ecosystem Division deploy oceanographic instrumentation on Sept. 13 at Lisianski Island as part of the recent research cruise to the Northwestern Hawaiian Islands. NOAA photo by Oliver Vetter

As part of the implementation of the NCRMP, CRED scientists on Sept. 3–19 deployed 16 arrays of temperature sensors along various reef systems, installing a total of 64 instruments at depths of 1–25 m. At its specific location on a reef, each sensor records the seawater temperature at the same time as other sensors, every 5 min, over a period of 3 years. The resulting product is a high-resolution picture of temperature variability of 16 different reef systems across space (across the archipelago and to a depth of 25 m) and time (3-year deployment of each sensor).

During the monitoring cruise earlier this month, 100 calcification accretion units (CAUs), like the one shown above, were installed in the Northwestern Hawaiian Islands by staff of the PIFSC Coral Reef Ecosystem Division. CAUs are used to measure not only net reef calcification rates but also species-specific recruitment rates and the percent cover of corals, crustose coralline algae, and fleshy algae. NOAA photo

During the monitoring cruise earlier this month, 100 calcification accretion units (CAUs), like the one shown above, were installed in the Northwestern Hawaiian Islands by staff of the PIFSC Coral Reef Ecosystem Division. CAUs are used to measure not only net reef calcification rates but also species-specific recruitment rates and the percent cover of corals, crustose coralline algae, and fleshy algae. NOAA photo

CRED scientists and partners also collected samples of seawater for chemical analysis, conducted hydrocasts with a conductivity-temperature-depth (CTD) instrument, and deployed installations designed to measure specific biological activities that can be affected by changes in the pH of a reef’s waters. Settling plates, known as calcification accretion units (CAUs), are used to measure net reef calcification rates, species-specific recruitment rates, and the percent cover of corals, crustose coralline algae, and fleshy algae. Bioerosion monitoring units (BMUs) are made up of precisely measured pieces of calcium carbonate, the material that makes up the skeletal structure of corals, and will provide a value for how much biological removal of reef structure is naturally present along the reef. Autonomous reef monitoring structures (ARMS) essentially act as “hotels” for cryptic biota living within the matrix of a reef ecosystem and provide a standard method for evaluation of the existing community of sessile and mobile organisms found on a reef.

Including work conducted during this cruise and the earlier PIFSC cruise SE-13-05 to Kure Atoll in July, CRED scientists have installed 100 CAUs, 50 BMUs, and 24 ARMS throughout the Northwestern Hawaiian Islands this year. Because monitoring activities associated with NCRMP are conducted on a triennial basis, CRED will return to these islands in 2016. At that time, researchers will retrieve and replace all instruments. NCRMP is a long-term project, and the goal of this work is to measure change over time. The results from this ongoing project will be available to help the managers of these remote islands monitor, evaluate, and predict the ecological effects of global climate change on the reefs of the Papahānaumokuākea Marine National Monument.