US Navy

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Marine Species Monitoring

Coral survey at Farallon de Medinilla

Introduction & Objectives

Coral reef surveys were conducted at Farallon de Medinilla (FDM) September 27 – October 1, 2017 by Space and Naval Warfare (SPAWAR) Systems Center Pacific, Scientific Diving Services (SDS) to satisfy requirements of the Mariana Islands Training and Testing Area Biological Opinion (MITT BO) issued by the National Marine Fisheries Service in 2015 (NMFS 2015). The primary objectives of this survey were to quantify the abundance and location around the island of Endangered Species Act (ESA)-listed corals, quantify coral reef health (percent cover of living coral, coral species composition, and coral condition), and compile observations of ordnance impacts. Secondary objectives were to record incidental observations of any other ESA-listed species encountered while fulfilling the primary objectives. The 2017 survey fully fulfilled Terms and Conditions 4 and 5 from the 2015 MITT BO (NMFS 2015), specifically to “provide reports of any observed in-water effects (e.g., crater size, observed mortality) to corals resulting from detonations of high-explosive bombs as they are discovered incidental to routine operations or during coral reef surveys to confirm or to help revise assumptions on the effects of high-explosive bombs to corals at various depths” and “survey coral reef habitat around FDM within 20 meters of water depth…to confirm presence or absence and abundance or ESA-listed corals and to assess general trends in coral reef species composition, percent coral coverage, and condition (disease, predators, extent of breakage, etc.)”.

This survey follows prior surveys at FDM, conducted by some of the same team members since 1997 (Smith and Marx 2015).

Technical Approach

Surveys were conducted in all habitat types around the island, including collection of approximately 750 photoquadrats on 50 transects and 250 representative photos in the survey area. Corals from 23 genera were identified in photoquadrat and representative photographs for this reporting effort.

Progress & Results

A single confirmed specimen of the ESA-listed coral Acropora globiceps was observed; seven other colonies that could potentially be A. globiceps were also observed in the same area as the confirmed specimen. Six colonies of coral were also identified as the ESA-listed coral Pavona diffluens. This coral species has not been confirmed in the Commonwealth of the Northern Mariana Islands (CNMI), although Randall (2003) lists it in Guam. This evidence confirms that ESA listed corals are present, but rare, in waters of <20m depth around FDM.

This survey also satisfied the requirement to “assess general trends in coral reef species composition, percent coral coverage, and condition (disease, predators, extent of breakage, etc.)” at <20m depth around FDM (NMFS 2015).

There was a severe coral bleaching event underway at FDM during the surveys, caused by regional anomalously warm sea surface temperatures.

Only three relatively fresh ordnance items were observed. All other ordnance encountered was historical. No impacts attributable to ordnance (e.g. craters, fresh scars near ordnance) were observed anywhere around the island. In summary, there were no observed effects of training, including the use of high-explosive bombs, on corals at FDM during this survey effort.

 

Publications

Coral bleaching variability during the 2017 global bleaching event on a remote, uninhabited island in the western Pacific: Farallon de Medinilla, Commonwealth of the Northern Mariana Islands

De-facto marine protection from a Navy bombing range: Farallon De Medinilla, Mariana Archipelago, 1997 to 2012