Expedition Underway to Assess Coral Reef Ecosystems of Wake Atoll and the Mariana Archipelago
The NOAA Ship Hi'ialakai is engaged in a nine-week research cruise to Wake Atoll, Guam, and the Commonwealth of the Northern Mariana Islands (CNMI). The Hi'ialakai departed from Ford Island, Honolulu, on March 10 on its transit to the western Pacific, and will return to Honolulu on May 24. Aboard the vessel are staff of the NOAA Pacific Islands Fisheries Science Center (PIFSC) and partner organizations who will conduct comprehensive oceanographic and ecological surveys of coral reefs in the study areas. This is the fourth biennial cruise to remote Wake Atoll, and the fifth biennial cruise to Guam and the CNMI, as part of the Pacific Reef Assessment and Monitoring Program (RAMP). The field party includes scientists from the PIFSC Coral Reef Ecosystem Division (CRED), including employees of the University of Hawaii Joint Institute for Marine and Atmospheric Research (JIMAR), and research partners from San Diego State University, NOAA Diving Center, Guam Coastal Management Program, CNMI Division of Environmental Quality, NOAA Fisheries Pacific Islands Regional Office, and Papahānaumokuākea Marine National Monument.
During her transit to Saipan from Honolulu, the Hi'ialakai will spend 5 days in surveys of Wake Atoll under the leadership of Jamison Gove, a CRED oceanographer employed by JIMAR. Due in part to its extreme isolation, Wake Atoll hosts a vibrant coral reef ecosystem. Previous RAMP cruises have documented relatively high coral cover, high species diversity and an abundance of reef fishes at Wake. Among many fish species observed at Wake Atoll, researchers have noted an abundance of two species only rarely seen in other parts of their Indo-Pacific range, the bumphead parrotfish (Bolbometopon muricatum) and Napoleon wrasse (Cheilinus undulatus).
After completing the surveys at Wake Atoll, the Hi'ialakai will travel to the Mariana Archipelago, where the vessel and field party will continue with more RAMP operations, first in waters of Saipan and other islands of the CNMI and then around Guam. The CNMI and Guam studies will be overseen by JIMAR scientist Jake Asher.
The research team will carry out surveys using a suite of standardized multi-disciplinary methods employed on RAMP cruises throughout the Pacific. These include Rapid Ecological Assessments (REA) to assess the abundance of corals, other large invertebrates like giant clams and urchins, fish and algae; and towed-diver surveys to assess large fish and composition of the coral reef habitat. In addition to the biological studies, oceanographic instruments will be used to measure conductivity, temperature, and depth of the water column (CTD casts); collect water samples for analysis of nutrients, chlorophyll, and carbonate chemistry; monitor ocean temperature (using moored sea-surface buoys and subsurface recorders); and measure direction and velocity of ocean currents (ADCP).
Scientists will also recover a series of Ecological Acoustic Recorders (EARs) deployed during surveys in 2009 to learn about the presence and activity of marine mammals, fish, crustaceans and other sound-producing marine life and how these change over time. Placed on the seafloor, these autonomous instruments record sounds made by marine fauna and human activity (e.g., vessel noises) when researchers are unable to record them otherwise. Researchers will also recover Autonomous Reef Monitoring Structures (ARMS) and later re-deploy them. ARMS are simple, standardized devices designed to roughly mimic the structural complexity of reef habitats and to attract colonizing non-coral invertebrates. Analysis of fauna collected by ARMS enables scientists to identify small, hard-to-sample, but ecologically important cryptic invertebrates. ARMS are being used throughout the Pacific and globally as part of the CReefs project of the Census of Marine Life. The goal of the project is to systematically assess spatial patterns and temporal changes in coral reef biodiversity.
At several locations across the survey area, scientists on the Hi'ialakai will deploy Calcification Acidification Units (CAUs) that will act as settlement structures for corals and algae that grow by producing calcium carbonate skeletons. More technically, the CAUs will help quantify accretion rates by crustose coralline red algae and hard corals. Accurate measurements of these accretion rates will allow researchers to monitor and assess the effects of ocean acidification on coral reef ecosystems. Oceans are becoming more acidic as a byproduct of increased carbon emissions worldwide. Each CAU consists of 2 gray polyvinylchloride (PVC) plates (10 × 10 cm) separated by a 1-cm spacer. CAUs are installed by pounding stainless steel rods by hand into bare substrate and then bolting the plate assembly to the rods. PVC encourages growth of crustose coralline red algae, and recruitment of coral, and the net weight gain of calcium carbonate on the surfaces of the CAUs can be an indicator of net calcification. CAUs deployed during this cruise will remain on the seafloor for 2 years, enabling the recruitment and colonization of crustose coralline red algae and hard corals. Then they will be collected and analyzed.
A new component of the research protocol on this cruise will be coral coring. Core samples will be extracted from massive coral colonies to help determine historical coral growth and accretion rates. Data on calcification and growth rates will enable scientists to hindcast the carbonate chemistry climate under which the coral reefs have existed, and how those conditions have varied over time, going back hundreds of years. To quantify the size and density of annual growth bands in coral skeletons, a small number of core samples (primarily targeting the genus Porites) will be collected and preserved for later study. Nondestructive CAT scans and image analysis techniques will be used to visualize growth bands that cannot otherwise be observed.
The RAMP cruises conducted by PIFSC are sponsored by NOAA's Coral Reef Conservation Program. The strategic goal of the research is to improve scientific understanding of coral reef ecosystems throughout the Pacific as a foundation for improved conservation and resource management.