SE16-02: Jumping in the deep end

by Motusaga Vaeoso

Training in standard fish survey methods for the Pacific Islands Fisheries Science Center’s reef fish survey project was difficult, intensive work. As the new coral reef monitoring technician for the American Samoa Coral Reef Advisory Group (CRAG), I wanted to participate in this research cruise (SE16-02) to further develop the skills that will improve my role as a technician. Participating in the NOAA research cruise was also a tremendous personal development opportunity for me. Before Paula Ayotte from the NOAA Coral Reef Ecosystem Program (CREP) arrived to conduct the final training the week before the cruise, there was still a good amount of preparation to be done.

Two months before the date of the cruise, I had to study my reef fish species. Paula provided helpful tools, review aids, and exams to develop our fish identification skills. The American Samoa reef fish flashcards created for the Flashcard Deluxe app was a handy mobile tool that helped develop my fish identification skills. In addition to studying fish, there was the matter of acquiring the required certifications for Advanced Diving using Nitrox and all of the physical health examination documentation for reciprocity to dive with NOAA divers.

Parrotfish

Parrotfish (Chlorurus frontalis), NOAA Photo by Tate Wester

On the first day of the training week, we reviewed fish identification, size estimation, binning, and benthic cover estimates. We also completed a dry run of the survey method. For the next three days, we were in the field—diving underwater with Paula, Alice Lawrence, and Brittney Honisch, to practice the skills we learned and familiarize ourselves with the survey methods. The more we practiced going through the motions, the more comfortable I felt. At sites where fish diversity and population is high, conducting the reef fish surveys can be overwhelming. Closely following the protocol was important to staying on track. As a fairly new diver I had to master the skill of multitasking underwater, which included recording fish data, maintaining buoyancy, checking air supply, and maintaining contact with my dive buddy.

I knew that this cruise was going to be physically challenging, especially for me. But it wasn’t until I tried to climb aboard the the American Samoa Department of Marine and Wildlife Resources (DMWR) enforcement boat from the water without the ladder, that it hit me, this is going to be really hard. To increase my upper body strength, I was tasked with five push-ups, increasing the number each day during the remaining days before the cruise. The last day of training consisted of entering data in the database, quality checking (QC) with my dive buddy, and an introduction presentation to life aboard the NOAA Ship Oscar Elton Sette. Going through the training prepared me for the cruise in the survey method and developed my fish identification and size estimation, substrate height and benthic cover estimation skills. It also helped me realize where my limits lie and areas that I needed to focus on improving.

Abandon Ship Drill

Putting on our survival “gumby” suits for an abandon ship drill aboard the NOAA Ship Oscar Elton Sette.

On April 14, I boarded the Sette along with other scientists from NOAA. The first day consisted of settling into our staterooms, familiarizing ourselves with where gear is stored, going over safety protocols, running drills to be prepared in the event of fire, man overboard, or need to abandon ship. There was a lot going on that day, but all I remember is feeling nauseous because the floor was constantly moving. After a day, I got over that seasick feeling and was ready to start.

Diving operations began on April 15. As it was the first day of diving, we took it slow. I did a swim test, used the Redundant Air Source System (RASS) for the first time, practiced buddy breathing skills and the rescue skills of removing an unconscious diver from the water. All divers had to have alternate air sources just in case of an “out of air” situation. I had to adjust my weight system to account for the weight of the RASS and get used to the weird feeling of this protruding object on my right side.

I noticed great improvement in my fish identification skills after every dive. As I got to see certain surgeonfish like Ctenochaetus striatus and Acathurus nigrofuscus repeatedly, certain features became more prominent and easy to recognize. With each dive, I looked forward to checking off a new fish or two on my mental list and it was always a treat to see a new species.

In my first deep dive of about 75 feet off the coast of Ta‘u Island, I saw my first shark. I do not have a fear of sharks but I do have a healthy respect for them and believe in giving them adequate space. Seeing this 130-cm gray reef shark up close was one of the most exhilarating moments I have ever experienced.

First shark

My first ever shark sighting at the island of Ta‘u in the Manu‘a Group, NOAA Photo by Louise Guiseffi

I signed up for the first leg of the cruise, from April 14-25, surveying the islands of Tutuila and Ta‘u. After six consecutive successful dives days, operations had to be halted because of cyclone Amos which was heading towards Tutuila. It was an anti-climactic end to such a great start but it could not be helped. Fortunately, the chief scientist Kevin Lino extended my stay for the second leg to survey Tutuila, Ofu and Olosega Islands, and Rose Atoll from April 25-May 6.

There was so much beauty and life to be seen around each of the islands we surveyed in American Samoa. My most favorite part of the experience was diving in the gorgeous and pristine waters of Rose Atoll Marine National Monument. It was phenomenal to see the vibrant pink and purple crustose coralline algae of Rose and the life it harbors. I saw so many new species of fish in numbers I have never seen before.

Tang

School of achilles tang (Acanthurus achilies) and whitecheek tang (Acanthurus nigricans) in an herbivorous feeding frenzy, NOAA Photo by Kevin Lino

Overall, my experience on the SE16-02 cruise was more enjoyable than I could have ever imagined. The quality of life aboard the ship was good, safety is a high priority, and the food was amazing! The crew and scientists were helpful, easy to work with, organized, and capable individuals. I had the opportunity to dive with almost all of the scientists and learned something new every day, a technique or skill, no matter how small. Louise Guiseffi showed me some helpful techniques to secure the rescue and tracking float with minimal tangling and easy removal. I was able to get on the small boats on my own with encouragement and coaching from Paula.

My last day of diving in the pristine waters of Rose Atoll was phenomenal and I could not have had a better last day for this research cruise. Although I did not get to see the Acanthurus hawaiiensis as I had hoped on my last dive, that is something to look forward to on my next visit to Rose. I am taking so much away from this cruise—not only in my professional development as a scientist but also in building character!

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.

Study reveals differences in coral development within Faga`alu Bay, American Samoa

By Bernardo Vargas-Ángel

Analyses of quantitative data from surveys conducted last year in American Samoa corroborate anecdotal patterns of differences in coral cover and demographics between the northern areas and the southern and central areas of Faga`alu Bay. Here, we provide a summary of our analyses and the project activities conducted by scientists from the PIFSC Coral Reef Ecosystem Division (CRED) and partner organizations in this bay between March and August 2012 as part of a project funded by NOAA’s Coral Reef Conservation Program.

Entitled “Inter-disciplinary study of flow dynamics and sedimentation effects on coral colonies in Faga`alu Bay, American Samoa,” this CRED-led project provides information necessary to better understand the effects of land-based sources of pollution (runoff and sedimentation) on the coral reef community in Faga`alu Bay. This information supports the development, implementation, and effectiveness of local, reef-to-ridge watershed conservation and management action plans. Benthic percent cover and coral demographic data were collected at 37 study sites along the shallow backreef and deep forereef in Faga`alu Bay. These quantitative data support the notion of patterns that previously had been observed only casually in the field: coral development is conspicuously prominent along the central and southern portions of the reef in Faga`alu Bay (Fig. 1a, b), compared to the northern areas, where coral growth is quite limited and depauperate (Fig. 1c, d).

Figure 1. Visual, spatial comparison of coral growth, development, and appearance of shallow habitats of the (a) south, (b) central and (c, d) northern areas of the backreef in Faga`alu Bay, American Samoa. NOAA photos by Bernardo Vargas-Ángel

Figure 1. Visual, spatial comparison of coral growth, development, and appearance of shallow habitats of the (a) south, (b) central and (c, d) northern areas of the backreef in Faga`alu Bay, American Samoa. NOAA photos by Bernardo Vargas-Ángel

Figure 2. Spatial comparison of mean cover (%) values for (a) live hard corals, (b) crustose coralline algae (CCA), (c) turf algae and spatial comparison of (d) values of the reef-builder ratio (ratio of mean cover for corals and crustose coralline algae combined to cover for nonaccreting organisms) from line-point-intercept surveys conducted in March–August 2012 in Faga`alu Bay off the island of Tutuila in American Samoa.

Figure 2. Spatial comparison of mean cover (%) values for (a) live hard corals, (b) crustose coralline algae (CCA), (c) turf algae and spatial comparison of (d) values of the reef-builder ratio (ratio of mean cover for corals and crustose coralline algae combined to cover for nonaccreting organisms) from line-point-intercept surveys conducted in March–August 2012 in Faga`alu Bay off the island of Tutuila in American Samoa. (Click on image above for a large version.)

Results from these quantitative surveys also indicate that, on average, percent live-coral cover was nearly twice as high along the southern area of the reef compared to the northern sector (Fig. 2a). Levels of crustose coralline algae were not distinctly different between the northern and southern sectors of the reef (Fig. 2b), but percent cover of turf algae was much greater along the northern forereef and backreef than along the other sampled portions of this bay (Fig. 2c). The northern areas of the reef in Faga`alu Bay are directly affected by terrigenous siltation and runoff. Surveys corroborate this appraisal, as exemplified by the reef-builder ratio, which is the ratio of corals and crustose coralline algae to nonaccreting organisms (macroalgae and turfalgae) calculated with values of mean percent cover. The reef-builder ratio was greater along the southern backreef and forereef than along the coral-impoverished northern reefs (Fig. 2d). In actively growing coral reefs, calcifying organisms—corals, crustose coralline algae, and other calcifying plants—typically dominate coral communities. In contrast, communities dominated by noncalcifiers, such as turf algae, cyanobacteria, and other macroalgae, are common in areas with suboptimal conditions for coral growth, including areas with elevated levels of nutrient inputs, pollution, turbidity, and sedimentation.

Figure 3. Multidimensional scaling ordination plot that illustrates the ecological grouping of study sites based on ecological composition, reef zone, and cardinal placement on reefs in Faga`alu Bay, American Samoa.

Figure 3. Multidimensional scaling ordination plot that illustrates the ecological grouping of study sites based on ecological composition, reef zone, and cardinal placement on reefs in Faga`alu Bay, American Samoa.  (Click on image above for a large version.)

We assembled an ordination (multidimensional scaling) plot on the basis of the benthic percent cover data. Illustrated in Figure 3, this plot indicates that overall benthic composition was distinct between reef zones (forereef vs. backreef) and cardinal position (north vs. south). A similarity profile (SIMPROFF) analysis supported a clear segregation between most forereef and backreef sites; and, within the backreef subdivision, the SIMPROFF analysis also showed the segregation between most of the northern and southern sites, corroborating the visual observations discussed above (Fig. 2). The separation between the northern and southern forereef sites was not strongly supported by the SIMPROFF analysis. These analyses provide quantitative evidence that the ecological communities of the northern and southern backreef in Faga`alu Bay are ecologically distinct from each other. This variation is driven most likely by the differences in levels of water quality, clarity, and terrigenous sedimentation.

Figure 4. Spatial comparison of (a) coral-colony density (colonies/m2) and (b) total coral generic richness from belt-transect surveys conducted in March–August 2012 in Faga`alu Bay. The color-coded pie charts indicate densities of selected dominant coral genera, and pie-chart size is proportional to total colony density.

Figure 4. Spatial comparison of (a) coral-colony density (colonies/m2) and (b) total coral generic richness from belt-transect surveys conducted in March–August 2012 in Faga`alu Bay. The color-coded pie charts indicate densities of selected dominant coral genera, and pie-chart size is proportional to total colony density. (Click on image above for a large version.)

Figure 4a illustrates estimates of coral-colony density of 4 important reef-building coral genera in Faga`alu Bay. Overall colony densities were relatively higher along the southern backreef and forereef (10.1 colonies/m2, standard error of the mean [SE] 0.90) than along the northern sector of the reef (6.01 colonies/m2, SE 0.81), and these differences were statistically significant (P=0.012, Student’s t-test). Differences in coral generic composition and density also were evident: corals of the genus Porites were heavily dominant along the shallow northern and southern backreef and corals of the genus Montipora occurred primarily along the deeper forereef. Additional notable spatial and structural differences indicated a preponderance of encrusting and foliose corals of the genera Montipora and Pavona, respectively, along the shallow northern backreef and, in contrast, the presence of branching corals of the genera Pocillopora and Acropora throughout the southern backreef. Fast-growing branching corals, such as Pocillopora and Acropora, are better adapted to the shallow, well-lit habitats of the southern backreef, compared to encrusting and foliose species that appeared to tolerate the lower levels of light and conditions of higher turbidity prevalent on the northern backreef (see Rodgers 1990; Crabbe and Smith 2005).

Differences among habitats also were observed in values of coral generic richness (Fig. 4b), with a greater mean number of genera occurring along the deeper forereef (10.95, SE 0.67) compared to the shallow backreef (6.29, SE 0.25), and these differences also were statistically significant (P=0.001, Student’s t-test). Such variation is expected given the disparate range of environmental conditions (for example, light, depth, water circulation) and of available microhabitats present on the forereef compared to the shallow, relatively homogeneous backreef.

Figure 5. Spatial comparison of prevalence (%) of (a) bleaching and (b) disease from belt-transect surveys conducted in March–August 2012 in Faga`alu Bay.

Figure 5. Spatial comparison of prevalence (%) of (a) bleaching and (b) disease from belt-transect surveys conducted in March–August 2012 in Faga`alu Bay. (Click on image above for a large version.)

Except for one site on the southern backreef, low levels of bleaching were commonplace across habitats and depths in Faga`alu Bay (Fig. 5a). Similarly, mean prevalence of coral disease (Fig. 5b) was low (0.56%, SE 0.16) overall; however, observed levels of disease were greater at north-facing backreef and forereef sites (0.82%, SE 0.35) than at south-facing sites (0.52%, SE 0.19). Although they were small, these differences could be associated with the elevated, chronic terrigenous runoff and sedimentation that affects these areas.

For another aspect of this project, in addition to the 37 study sites, 3 permanent coral reef monitoring stations were installed along the shallow backreef and channel of Faga`alu in March 2012 to evaluate long-term changes in community structure and composition. These stations are periodically monitored by students of the American Samoa Community College and staff of the American Samoa Department of Marine and Wildlife Resources. Also, oceanographic instrumentation, including wave-and-tide recorders, current meters, and salinity and temperature recorders, were deployed in March and April 2012 at strategic sites inside and outside of Faga`alu Bay to better profile water flow patterns and sediment residence times. Project activities will continue throughout 2013. CRED plans to conduct additional demographic surveys in 2013 to expand and complement the benthic assessments conducted thus far. CRED scientists plan to gather supplementary information on coral-colony sizes, density of juvenile corals, and coral bleaching and disease. After activities have concluded, results of the biological and oceanographic surveys will be made available to all relevant parties.

Many partners have provided instrumental support to this project. Partner organizations include the NOAA Pacific Islands Regional Office (Fatima Sauafea-Leau), American Samoa Department of Marine and Wildlife Resources (Domingo Ochivallo), San Diego State University (Trent Biggs and Alex Messina), American Samoa Community College (Kelley Anderson Tagarino), and the Faga`alu watershed community working group.

References

Rodgers CS. 1990. Responses of coral reefs and reef organisms to sedimentation. Mar Ecol Prog Ser 64:185–202.

Crabbe MJC, Smith DJ. 2005. Sediment impacts on growth rates of Acropora and Porites corals from fringing reefs of Sulawesi, Indonesia. Coral Reefs 24:437–441.

Survey of mesophotic coral reefs completed in the Manu`a Islands, American Samoa

Scientists Marie Ferguson, Jeremy Taylor, and John Rooney from the PIFSC Coral Reef Ecosystem Division (CRED) and Tee Jay Letalie of the American Samoa Department of Marine and Wildlife Resources (DMWR) recently completed an 18-day project to survey habitats and communities of mesophotic coral reef ecosystems around the Manu`a Islands in American Samoa. The Manu`a Islands are a group of 3 lightly populated islands ~102 km (55 nautical miles) east of the main island of Tutuila (Fig. 1).

Figure 1. Map of American Samoa.

Figure 1. Map of American Samoa.

A similar survey was conducted around Tutuila in 2008, leading to the publication of a paper, “Mesophotic communities of the insular shelf at Tutuila, American Samoa,” in the journal Coral Reefs and contributing to other products designed to support management of coral reef ecosystems. The success of that project inspired CRED and DMWR scientists, with the support of NOAA’s Coral Reef Conservation Program, to conduct surveys around the Manu`a Islands.

Until a few years ago, the general perception among marine scientists was that reef-building, stony corals were limited mostly to depths of 40 m and shallower because light below that depth was insufficient to enable them to survive. Although individual live corals had been observed at much deeper depths, those coral species were viewed as oddities that were too rare to be ecologically important. This general perception fit with the personal observations of most scientists: this maximum depth of 40 m coincided with the approximate maximum depth of a no-decompression limit for a scuba dive with a single scuba tank, and, more often than not, coral cover did decline with depth.

In 2003, however, reports surfaced in both scientific literature and news services about a healthy reef at depths of 65 m off the coast of Florida. Over time, more and more stories have appeared about light-dependant coral reefs found at depths well below 40 m. Today, these communities of corals, algae, fishes, invertebrates, and other organisms are referred to as mesophotic coral ecosystems (MCEs). They often contain well-developed coral reefs and diverse and abundant fish communities, and they are ecologically important components of overall coral reef ecosystems.

Still, working at depths of 30–150 m is technologically and logistically challenging, and these deep ecosystems remain relatively unknown areas that are rarely included in ecological monitoring programs or explicitly considered in management activities. The aim of CRED’s recent study was to characterize MCEs in the Manu`a Islands and gain an understanding of where they are found to provide information critical to resource managers in their decision making about these ecosystems.

The team towed an underwater camera sled (Fig. 2) at randomly selected points around the Manu`a Islands on Nov. 1–13 to capture video imagery of organisms growing on the seafloor and fish species living nearby. The sled, more commonly referred to as TOAD (for towed optical assessment device), features a downward-facing still camera, a forward-facing video camera, a depth sensor, sonar altimeter, and other instruments. While the sled was in the water, the operator sat in front of a control console (Fig. 3) on the boat and watched a live feed from the sled’s video camera. With a switch mounted on the right side of the control console, the operator could automatically raise or lower the TOAD in the water. Video from the onboard video camera was recorded on a VCR in the console, and data on the sled’s track were recorded on a laptop computer. After each day of surveying, still photos were downloaded from the camera once the TOAD was back aboard the vessel.

Figure 2. The towed optical assessment device is lowered into the ocean with a 12-V pot hauler and an umbilical cable.

Figure 2. The towed optical assessment device is lowered into the ocean with a 12-V pot hauler and an umbilical cable.

Figure 3. Scientist Marie Ferguson stands next to the control console for the camera sled. NOAA photo

Figure 3. Scientist Marie Ferguson stands next to the control console for the TOAD. NOAA photo

Figure 4. Bonavista II, docked alongside the pier in Ofu Harbor. NOAA photo

Figure 4. The chartered vessel, Bonavista II, docked alongside the pier in Ofu Harbor. NOAA photo

The TOAD was deployed off the 12-m (40-ft) vessel Bonavista II (Fig. 4), which is owned and expertly operated by Tutuila-based Pago Pago Marine Charters. The seaworthy Bonavista II is regularly used by resource management personnel from several agencies to transport their scientists and managers to work around the Manu`a Islands and Rose Atoll. While the captain and first mate stayed aboard the vessel each night, the scientists stayed at the Vaoto Lodge on the southeastern coast of Ofu. Carlo Caruso, a park ranger on Ofu for the National Park of American Samoa, was very helpful and generously allowed the scientists to use space at the National Park Service’s laboratory to set up a data processing station and store spare equipment.

Around the islands of Ofu and Olosega, 65 camera sled dives were completed, covering a length of 30.8 km of seafloor (Fig. 5). Another 27 dives were made around the island of Ta`u and covered a length of 11.5 km of seafloor (Fig. 6).

Figure 5. Map showing tracks of the camera sled during surveys around the islands of Ofu and Olosega.

Figure 5. Map showing tracks of the camera sled during surveys around the islands of Ofu and Olosega.

Figure 6. Map showing tracks of the camera sled during surveys around the island of Ta`u.

Figure 6. Map showing tracks of the camera sled during surveys around the island of Ta`u.

The scenery around the Manu`a Islands, both above and below the surface of the ocean, is often dramatic and beautiful. The scientists found a number of areas with diverse, well-developed coral reefs (Figs. 7–10). Many of these reefs had abundant fish populations with communities of jacks and snappers, in particular, at several spots around these islands at the edge of steep ledges, generally at depths of 90–100 m. Abundant sea fans also were observed along these steep ledges.

Rooney gave a presentation on preliminary results of this survey on Nov. 14 in Pago Pago to an audience of about 30 natural resource managers and stakeholders. Over the next year, seafloor substrates and the organisms growing on them, as recorded in video imagery from this survey, will be classified through the use of a standardized method that CRED has used for imagery collected across the Pacific Islands Region. Local partners from the DMWR are particularly interested in fish communities at mesophotic depths, so fish species observed in the imagery will be identified to the lowest taxonomic resolution possible, their lengths will be estimated, and this information will be entered in a database.

Results of these classification efforts will be made available for download along with other data that CRED has collected in American Samoa. In time, other products, such as benthic habitat maps and scientific publications, may be created as well.

By John Rooney
Figure 7. Foliose coral species off northeastern Olosega at a depth of ~60 m. NOAA photo

Figure 7. Foliose coral species off northeastern Olosega at a depth of ~60 m. NOAA photo

Figure 8. Various coral species and crustose coralline algae off northwestern Ofu at a depth of ~50 m. NOAA photo

Figure 8. Various coral species and crustose coralline algae off northwestern Ofu at a depth of ~50 m. NOAA photo

Figure 9. Soft coral species with crustose coralline algae off northwestern Ofu at a depth of ~50 m. NOAA photo

Figure 9. Soft coral species with crustose coralline algae off northwestern Ofu at a depth of ~50 m. NOAA photo

Figure 10. Various coral species and macroalgae off northern Ta`u at a depth of ~45 m. NOAA photo

Figure 10. Various coral species and macroalgae off northern Ta`u at a depth of ~45 m. NOAA photo

 

New data on benthic cover at Guam now available

Since the first cruise of the Pacific Reef Assessment and Monitoring Program (Pacific RAMP) in 2000, NOAA Fisheries has used towed-diver surveys to provide large-scale assessments of benthic habitats. This survey method involves towing scuba divers behind a small boat at a constant speed (~1.5 kt) and depth (~15 m standard target), with individual surveys lasting ~50 min and covering ~2 km of habitat. A GPS track of the path of each survey launch is recorded, and digital still photographs of the benthos also are captured every 15 s. Towed-diver surveys are part of an integrated, multidisciplinary suite of research activities conducted as part of Pacific RAMP, which is led by the PIFSC Coral Reef Ecosystem Division (CRED) and funded by NOAA’s Coral Reef Conservation Program. Pacific RAMP cruises have been conducted biennially at Guam since 2003.

Figure 1. Map of towed-diver-survey tracks and five geographic regions around Guam from CRED research cruises conducted in 2003–2011.

To improve understanding of islandwide trends, CRED scientists have determined benthic cover around Guam at the functional level—corals, algae (fleshy macroalgae and turf algae combined), and crustose coralline red algae—through analyses of digital images collected during Pacific RAMP towed-diver surveys conducted from 2003 to 2011. The data set generated from these image analyses summarizes the overall islandwide trends on the basis of ~100 towed-diver surveys completed in five geographic regions (north, east, south, west, and northwest; Fig. 1). These new analyses represent an important baseline and trend data set that is pivotal to the implementation of NOAA Fisheries’  Habitat Blueprint initiative for Guam.

Results from these image analyses indicate a slow, steady, islandwide decline in live coral cover from 19.4% (2.6 standard error of the mean [SE]) in 2003 to 10.4% (1.4 SE) in 2011 (Fig. 2). The greatest change in coral cover (~20%) was observed between 2005 and 2007, the same time period in which visual observations from towed-diver surveys noted steep increases in densities of crown-of-thorns seastars (Acanthaster planci) islandwide.

These image-analysis data are available currently upon request from the CRED information services team. Make inquiries to nmfs.pic.credinfo@noaa.gov.

 By Bernardo Vargas-Ángel

Figure 2: Temporal comparison of mean values of cover (%) of live hard corals, algae (fleshy macroalgae and turf algae combined), and crustose coralline red  algae (CCA) from analyses of benthic images collected during towed-diver surveys conducted at Guam in 2003–2011. Mean densities (individuals/100 m2) of crown-of-thorns seastars (Acanthaster planci; COTS) are provided for reference. Error bars indicate standard error of the mean (± 1 SE).