Update from the Mariana Archipelago: monitoring cruise completes work in the southern islands

By Bernardo Vargas-Ángel
The NOAA Ship Hi`ialakai, seen off the coast of Anatahan, a northern island in the Commonwealth of the Northern Mariana Islands, during a previous monitoring cruise in the Mariana Archipelago in May 2009. NOAA photo by Bernardo Vargas-Ángel

The NOAA Ship Hi`ialakai, seen off the coast of Anatahan, a northern island in the Commonwealth of the Northern Mariana Islands, from a small boat during a previous monitoring cruise in the Mariana Archipelago in May 2009. NOAA photo by Bernardo Vargas-Ángel

On April 17, the NOAA Ship Hi`ialakai departed Saipan Harbor and began Leg III of the PIFSC cruise HA-14-01 with a few more days of monitoring operations around Saipan before transiting to the island of Sarigan. With work essentially complete in the southern islands of the Mariana Archipelago, the Hi`ialakai had been in port in Saipan Harbor for a short, 3-day pause between legs of this Pacific Reef Assessment and Monitoring Program (Pacific RAMP) expedition. Activities to monitor coral reef ecosystems of the Commonwealth of the Northern Mariana Islands (CNMI) began on April 5 during Leg II of this cruise and work around Guam took place on March 25–April 4, primarily during Leg I. Led by the PIFSC Coral Reef Ecosystem Division (CRED), this mission marks the 6th monitoring cruise in Guam and the CNMI by staff from PIFSC and partner agencies since 2003.

Around Guam, Rota, Aguijan, Tinian, and Saipan Islands, CRED scientists on March 25–April 18 conducted ecosystem surveys of fishes, benthic and coral communities, and microbes and deployed oceanographic instruments and biological installations. During Leg III, which is expected to conclude on May 6, CRED staff will conduct small-boat operations for coral reef ecosystem monitoring at the following northern islands and banks: Sarigan, Zealandia Bank, Guguan, Alamagan, Pagan, Agrihan, Asuncion, Maug, Supply Reef, and Farallon de Pajaros (or Uracas).

On a reef off the coast of Rota Island, divers conduct belt-transect surveys of the benthos on April 8. NOAA photo by Bernardo Vargas-Ángel

On a reef off the coast of Rota Island, divers conduct a belt-transect survey of the benthos on April 8 during the PIFSC cruise HA-14-01, the 6th expedition in the Marina Archipelago since 2003 for the Pacific Reef Assessment and Monitoring Program, which is led by the PIFSC Coral Reef Ecosystem Division. NOAA photo by Bernardo Vargas-Ángel

A diver on April 13 collects digital images of reef benthos along a transect at a Climate Monitoring Station off the cost of Saipan. NOAA photo

A diver on April 13 collects digital still photographs of the reef benthos along a transect at a Climate Monitoring Station off the cost of Saipan. Such benthic images can be analyzed to characterize benthic habitat and estimate percent cover of key functional groups. NOAA photo

At Rapid Ecological Assessment (REA) sites, surveys for reef fishes document species richness, abundance, and sizes, and surveys of benthic and coral communities study the percent composition of bottom-dwelling organisms in addition to the densities, sizes, and health conditions of coral colonies. During broad-scale towed-diver surveys, divers record observational data on large-bodied fishes (>50 cm total length), percent composition of the seafloor, coral stress, and conspicuous invertebrates. Studies of microbial communities document the diversity and abundance of bacteria and viruses and their interactions with coral reefs.

This mission also includes studies of the diversity of cryptic invertebrates; collection of data on water temperature, salinity, carbonate chemistry, and other physical characteristics of coral reef environments; and assessment of the potential early effects of ocean acidification on cryptobiota (e.g., small, hidden organisms) and the rates of reef carbonate deposition and coral calcification.

Researchers of the PIFSC Coral Reef Ecosystem Division use trays, like the one in this photo taken on April 13, to sort the cryptic reef invertebrates that they collect from autonomous reef monitoring structures (ARMS) retrieved during this current cruise from the nearshore locations where they had been deployed in 2011 during the previous Pacific Reef Assessment and Monitoring Program expedition in the Mariana Archipelago. NOAA photo

Researchers of the PIFSC Coral Reef Ecosystem Division on April 13 use this tray and others to sort the cryptic reef invertebrates that they collect from the autonomous reef monitoring structures (ARMS) retrieved during this current cruise from the nearshore locations where they had been deployed in 2011 during the previous Pacific Reef Assessment and Monitoring Program expedition in the Mariana Archipelago. NOAA photo

Thus far across the 5 southern Mariana Islands, including work on April 17, CRED researchers during this cruise have completed 66 towed-diver surveys along a combined 130 km of coastline and, at REA sites, 153 fish surveys and 62 benthic surveys. The instrumentation team deployed 4 Climate Monitoring Stations around Guam and 3 stations around Saipan, with each station containing arrays of subsurface temperature recorders (STRs), calcification accretion units (CAUs), autonomous reef monitoring structures (ARMS), and bioersion monitoring units (BMUs). Overall, no notable changes in the structure of the fish and benthic communities can be reported at this time for the areas surveyed at Guam or in the southern CNMI, in comparison to survey results from the previous cruise in this region in 2011. Additionally, no widespread coral bleaching or outbreaks of coral diseases or corallivorous crown-of-thorns seastars (Acanthaster planci) were observed.

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