Assessing impacts of coral bleaching: NOAA scientists embark on a three-month survey of coral reef ecosystems in the Hawaiian Archipelago

by Drs. Bernardo Vargas-Ángel and Rusty Brainard
FFS_2013_IMG_2852E

French Frigate Shoals in the Northwestern Hawaiian Islands (NOAA Photo)

Today, scientists from the NOAA Pacific Islands Fisheries Science Center’s Coral Reef Ecosystem Program boarded the NOAA Ship Hi‘ialakai to begin a 75-day Hawaiian Archipelago Reef Assessment and Monitoring Program (HARAMP) research mission. The goal of this mission is to document the status and trends of the coral reef ecosystems of the populated main Hawaiian Islands and the remote Papahānaumokuākea Marine National Monument in the uninhabited Northwestern Hawaiian Islands.

As part of the National Coral Reef Monitoring Program of NOAA’s Coral Reef Conservation Program, this HARAMP expedition will conduct the first statewide surveys to assess the overall impacts of two back-to-back mass coral bleaching events, which occurred in 2014 and 2015 and were caused by unusually warm water temperatures. When water temperatures reach 1°C warmer than their usual summertime maximum, many corals begin to lose the symbiotic algae living in their tissues, making them look white — that is, they become “bleached.”

This expedition will be the 6th monitoring cruise in the main Hawaiian Islands and the 10th monitoring cruise in the Northwestern Hawaiian Islands led by the PIFSC Coral Reef Ecosystem Program and partner agencies since 2000. It’s designed to provide an ongoing, consistent flow of information to document the status and long-term trends of the coral reefs and changing environmental conditions.

These statewide monitoring surveys will complement the local and site-specific coral reef monitoring efforts led by our partner agencies and institutions. Partners participating in this mission include scientists from the State of Hawai‘i Division of Aquatic ResourcesThe Nature ConservancyHawai‘i Institute of Marine Biology, and San Diego State University, among others.

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Autonomous Reef Monitoring Structure installed on left, calcification accretion unit on right (NOAA Photo)

Scientists will survey the coral reefs around each of the main Hawaiian Islands, including Ni‘ihau, Kaua‘i, O‘ahu, Molokai, Lāna‘i, Maui, Kaho‘olawe, and Hawai‘i Islands, and the coral reefs at French Frigate Shoals, Lisianski/Neva Shoals, Pearl and Hermes Atoll, and Kure Atoll in the Northwestern Hawaiian Islands. Each day, they will deploy 4–5 small boats with a team of scientific divers from the Hi`ialakai to conduct in-water surveys of the different reef zones, such as forereef, backreef, and lagoons around the different sides of each island or atoll ecosystem. We often find that the coral reefs and associated organisms vary greatly between leeward and windward sides of islands that are exposed to different environmental conditions, such as waves and currents.

Coral Reef

Under the direction of Chief Scientists Drs. Bernardo Vargas-Ángel in the main Hawaiian Islands and Brett Schumacher in the Northwestern Hawaiian Islands, the different dive teams will conduct underwater surveys of reef fishes, corals, other invertebrates, algae, and microbes. They will deploy and retrieve Autonomous Reef Monitoring Structures, or ARMS, to assess the biodiversity of ‘cryptic’ coral reef species that live within the reef (small crabs, shrimp, snails, etc.).

Autonomous Reef Monitoring Structures (ARMS) installed at Pearl and Hermes Atoll, NWHI (NOAA Photo)

Autonomous Reef Monitoring Structures (ARMS) installed at Pearl and Hermes Atoll, NWHI (NOAA Photo)

Close-up of ARMS unit at Pearl and Hermes Atoll, NWHI (NOAA Photo)

Close-up of ARMS unit at Pearl and Hermes Atoll, NWHI (NOAA Photo)

Calcification accretion unit installed at French Frigate Shoals, NWHI (NOAA Photo)

Calcification accretion unit installed at French Frigate Shoals, NWHI (NOAA Photo)

 

 

 

 

 

 

Additionally, oceanographers aboard the Hi`ialakai will collect data on water temperature, salinity, carbonate chemistry, and other physical characteristics of the coral reef environment with an assortment of oceanographic monitoring instruments. Among other things, they’re monitoring the ecological impacts of ocean acidification by determining the rates of reef growth and reef removal using tools called calcification accretion units and bioerosion monitoring units, respectively, which are deployed on the reef substrate for three years.

Data collected by the scientific staff of this cruise are pivotal to long-term biological and oceanographic monitoring of coral reef ecosystems in the Hawaiian Archipelago. This 2016 HARAMP expedition will help inform scientists, resource managers, and policy makers about changes that have occurred compared with similar surveys conducted in 2000, 2001, 2002, 2003, 2004, 2005 (main Hawaiian Islands only), 2006, 2008, 2010, and 2013.

Hawaiian Archipelago Reef Assessment and Monitoring Program Cruise 2016 Timeline

In particular, data on the abundance and spatial distribution of reef fishes and benthic organisms will allow scientists to evaluate potential changes in the condition and integrity of coral reef ecosystems across the Hawaiian Archipelago. It will also enable federal and state resource managers to more effectively manage and conserve reef-associated animal and plant life in the region. This year’s surveys are particularly important since many of the coral reefs experienced mass coral bleaching in both 2014 and 2015, and these surveys will provide an opportunity to assess the net change in coral cover for each of the islands across the archipelago.

 

From the Village to the Pacific, coordinating coral reef assessments in Tutuila, American Samoa

by Kelvin Gorospe and Adel Heenan
1.Gorospe_survey

Kelvin Gorospe sets transects for a fish survey.

Following the American Samoa portion of the recent Reef Fish Survey cruise, Adel and I disembarked NOAA ship Oscar Elton Sette to remain in Pago Pago, American Samoa. From May 9 to 13, we met with partners from the American Samoa Coral Reef Advisory Group (CRAG), Department of Marine and Wildlife Resources, the Environmental Protection Agency, NOAA’s Coral Reef Conservation Program, National Marine Sanctuary of American Samoa, and National Park Service. During this time, we facilitated a workshop to initiate steps to achieve cross-scale coordination between our programs and cross-scale integration of our datasets. By bringing multiple agencies and institutions together, all of whom are engaged in coral reef ecosystem monitoring in Tutuila, American Samoa, we used our collective experience (more than 120 years!) in coral reef monitoring to think about cross-scale ecosystem monitoring. How can we combine our resources to complement each other’s monitoring programs? Can we integrate datasets collected at different scales, and if not, are there steps that we can take to facilitate this integration down the road?

2.Group

Several participants of the data integration workshop held in Pago-Pago, American Samoa.

To begin taking steps in the right direction, we had to figure out how to compare different datasets and understand the monitoring objectives of different agencies. Effective monitoring objectives determine the scope of inference for the data collected and more often than not, monitoring programs are optimized to report at a specific spatial scale. For example, data collected by the Pacific Islands Fisheries Science Center’s Coral Reef Ecosystem Program (CREP) for the Pacific Reef Assessment and Monitoring Program (Pacific RAMP) are primarily designed to report on key metrics of ecosystem condition at an island or sub-island scale for each of the U.S.-affiliated islands and atolls in the Pacific. In contrast, data collected by various monitoring agencies operating in Tutuila are designed to report metrics at the village/bay or site-specific scale. Coordinating efforts across scales is an important component of ecosystem-based management that allows for more effective comparisons between efforts. For example, how does the status of reef fish populations in a particular marine protected area compare to reef fish populations for the rest of the island, or islands in an archipelago? Such coordination and comparisons allow for inference at an ecosystem-relevant scale. Blending datasets and coordinating monitoring programs is, however, easier said than done.

One barrier to seamless integration that was identified at the workshop, was the existence of multiple survey methods. When identical methods are used to collect data for different scales, the data can be blended and compared on these different scales. Last year, the National Marine Sanctuaries of American Samoa partnered with CREP to collect baseline data for Aunu‘u and Fagatele Bay. Typically CREP collects island-scale data for the National Coral Reef Monitoring Program (NCRMP). However, since the method used to collect both the Pacific RAMP and National Marine Sanctuaries datasets were identical, the Sanctuaries’ baseline data could be easily compared to the island-scale data collected for NCRMP. For many of the monitoring programs operating in Tutuila, however, blending datasets will not be so easy. For example, many of them use belt-transects to conduct fish surveys, while CREP uses a stationary point count method. While both acquire the same type of information, the use of different methods makes blending the data a bit challenging.

3.Lawrence_CRAG

Workshop participant, Alice Lawrence from the Coral Reef Advisory Group, presenting a SWOT evaluation of the American Samoa Coral Reef Monitoring Program’s dataset.

Over several days, partners presented the details (e.g., sampling design, quantitative objectives, etc.) of their individual datasets, reviewed examples and strategies for how datasets can be integrated, and conducted SWOT (strengths, weaknesses, opportunities, and threats) evaluations of their monitoring programs. Our purpose was to understand the intricacies of each other’s datasets before considering how we could potentially integrate.

The workshop culminated in a structured discussion on how to integrate community, jurisdictional, and federal coral reef ecosystem monitoring datasets. Participants were asked to detail concrete, short, and long-term steps that can be taken to overcome existing barriers to integrating our datasets. Recommendations ranged from conducting a calibration study between several of our datasets to facilitate the comparison of our different survey methods to publishing an information brief that co-reports multiple datasets for a single village’s marine resources. These recommendations fell into four broad categories that encapsulate the different components of a monitoring program – (1) communication strategy, (2) data integrity, (3) data relevance, and (4) non-data resources (e.g., creating a full-time interagency monitoring team in Tutuila) – and will be detailed in a forthcoming workshop report.

We are now working on an information brief, that will provide both an outreach tool and serve as a pilot study for how our multiple datasets could be co-reported. The information brief will report on biological and socio-economic indicators collected across multiple efforts for a single village. Our plan is to produce this informational product for a village where multiple datasets already exist. If successful, we hope to roll out similar products for other villages.

4.Data_Tutuila

A map of several different monitoring datasets collected around Tutuila, American Samoa

Funded by NOAA’s Coral Reef Conservation Program, the workshop and its outcomes are an important link between jurisdictional scientists in American Samoa focused on local monitoring efforts and PIFSC scientists focused on Pacific-wide and national efforts. Based on the next steps and recommendations identified at the workshop, the benefits to coordinating across multiple scales are clear: not only will integration allow us to understand more about the ecosystems in which we operate, but will also allow us to collectively achieve more.

SE16-02: American Samoa Reef Fish Survey Summary

by Adel Heenan and Marc Nadon

For the past three weeks, the NOAA Ship Oscar Elton Sette has been the support platform for the Pacific Islands Fisheries Science Center’s reef fish survey project. This research project was led by the NOAA Coral Reef Ecosystem Program (CREP), with partner agency representatives from the American Samoa Department of Marine and Wildlife Resources (DMWR) and the Bigelow Laboratory of Ocean Sciences. The mission was similar to the Pacific RAMP work, but with a particular focus on surveying reef fish assemblages.

Divers collected length observations for all reef fishes recorded during their underwater surveys. To do so accurately, trained divers regularly practice fish sizing using wooden cut-outs in-between research cruises. Length measurements for each reef fish surveyed allows an estimation of biomass by using pre-determined length-weight relationships. Furthermore, it is also used to estimate the size composition of fish populations and obtain a key indicator of population status: average length of exploited size classes. The reason we use this indicator is intuitive: as the exploitation rate of a fish population increases, fewer individual fish have a chance to reach older ages, and therefore, fewer individuals reach larger sizes. Mathematical expressions developed in the 1950s by fisheries scientists can actually relate average length to current fishing mortality rates, and these can be used in computer population simulations to investigate current stock status and generate management advice.

4.Survey_P.Ayotte

Reef fish survey divers regularly train in estimating fish size by using wooden cut-outs of known sizes (NOAA Photo by Paula Ayotte).

Outlined below is a summary of our recently completed survey efforts. More detailed survey results will be available in a forthcoming survey report.

Sampling effort

  •  Ecological monitoring took place in American Samoa from April 15 2016- May 5 2016.
  • Data were collected at 202 sites. Surveys were conducted at Ofu and Olosega (n=11), Rose (n=47), Tau (n=50) and Tutuila (n=94).
  • At each site, the fish assemblage was survey by underwater visual census and the benthic community rapidly assessed.
  • At a subset of sites (n=51), paired comparisons of fish surveys performed using closed circuit re-breathers versus open circuit SCUBA were conducted. Those data will be analyzed and presented in a separate publication.
TCW_rebreather

Diver conducts reef fish survey with a closed circuit re-breather (NOAA photo by Tate Wester).

Overview of the data collected

Primary consumers include herbivores (which eat plants) and detritivores (which bottom feed on detritus), and secondary consumers are largely omnivores (which mostly eat a variety of fishes and invertebrates) and invertivores (which eat invertebrates).

Spatial sampling design

Survey site locations are randomly selected using a depth-stratified design. During project planning and the project itself, logistic and weather conditions factor into the allocation of monitoring effort around sectors of each island or atoll. The geographic coordinates of sample sites are then randomly drawn from a map of the area of target habitat per study area. The target habitat is hard-bottom reef, the study area is typically an island or atoll, or in the case of larger islands, sectors per island, and the depth strata are shallow (0-6 m), mid (6-18 m), and deep (18-30 m).

Sampling methods

A pair of divers surveys the fish assemblage at each site using a stationary-point-count method (Figure 5). Each diver identifies, enumerates, and estimates the total length of fishes within a visually estimated 15-m-diameter cylinder with the diver stationed in the center. These data are used to calculate fish biomass per unit area (g m-2) for each species. Mean biomass estimates per island are calculated by weighting averages by the area per strata. Island-scale estimates presented here represent only the areas surveyed during this project. For gaps or areas not surveyed during this project, data from this and other survey efforts will generally be pooled to improve island-scale estimates.

Fig5.REA_method

Figure 5. Method used to monitor fish assemblages and benthic communities at the Rapid Ecological Assessment (REA) sites.

Each diver also conducts a rapid visual assessment of reef composition, by estimating the percentage cover of major benthic functional groups (encrusting algae, fleshy macroalgae, hard corals, turf algae and soft corals) in each cylinder. Divers also estimate the complexity of the surface of the reef structure, and they take photos along a transect at each site that are archived to allow for future analysis.

About the monitoring program

Pacific RAMP forms a key part of the National Coral Reef Monitoring Program of NOAA’s Coral Reef Conservation Program (CRCP), providing integrated, consistent, and comparable data across U.S. Pacific islands and atolls. CRCP monitoring efforts aim to:

  • Document the status of reef species of ecological and economic importance.
  • Track and assess changes in reef communities in response to environmental stressors or human activities.
  • Evaluate the effectiveness of specific management strategies and identify actions for future and adaptive responses.

In addition to the fish community surveys outlined here, Pacific RAMP efforts include interdisciplinary monitoring of oceanographic conditions, coral reef habitat assessments and mapping. Most data are available upon request.

For more information:

CREP publications

CREP monitoring reports

CREP fish team

Fish team lead and fish survey data requests: ivor.williams@noaa.gov, adel.heenan@noaa.gov

 

Four Million Nine Hundred Ninety-Nine Thousand Nine Hundred and Ninety-Nine

By Kevin Lino

Five million… that number has a pleasant vastness to it. Five million of anything seems overwhelming. Try to picture five million fish. Start small and keep expanding. How would that look? Would they be one compact bait ball of iridescent shapes or a colorful patch work of reef fish schooling together? Well, it would take years to count that high and yet here we stand (or swim) just a few thousand fish away from reaching this landmark.

Image 1: A school of Big Eye Jack (Caranx sexfasciatus) trail behind a towed diver during a survey. Photo by Kevin Lino

Image 1: A school of Big Eye Jack (Caranx sexfasciatus) trail behind a towed diver during a survey. Photo by Kevin Lino

Image 2: Map of Study Region for Jarvis Island, Palmyra Atoll, and Kingman Reef.

Image 2: Map of Study Region for Jarvis Island, Palmyra Atoll, and Kingman Reef.

For the PIFSC Coral Reef Ecosystem Division (CRED) fish team, it has taken 15 years of dedicated hard work under the ocean’s surface to get to this point. This happens as our team collects visual census data on reef fish populations throughout the US-affiliated Pacific Islands. As part of the Pacific Reef Monitoring and Assessment Program (RAMP) these surveys support the National Coral Reef Monitoring Program (NCRMP). The goal of our research missions is to conduct integrated, consistent, and comparable monitoring of coral reefs across all regions while assessing and detecting change in natural resources. This is true around large inhabited islands like Tutuila in American Samoa, where we recently completed surveys, well as the tiny remote atolls in the Line Islands chain where we are currently working.

Image 3: A Scalloped Hammerhead Shark (Sphyrna lewini) cruises the bottom amongst schools of anthias at Jarvis Island. Photo by Kevin Lino

Image 3: A Scalloped Hammerhead Shark (Sphyrna lewini) cruises the bottom amongst schools of anthias at Jarvis Island. Photo by Kevin Lino

Image 4: Diver Marie Ferguson tows over a school of anthias at Jarvis Island. Photo by Kevin Lino

Image 4: Diver Marie Ferguson tows over a school of anthias at Jarvis Island. Photo by Kevin Lino

To date, the division has counted 4,890,980 fish throughout our survey areas using several methods. While it is hard to know which method will be used to count the five millionth fish, our primary surveys are conducted by stationary point count (SPC) divers who use a transect line along the seafloor counting every species in that area. Another team is towed behind a small boat counting the larger (over 50 cm) more mobile species– circumnavigating the islands and covering up to 15km each day. Odds are in the favor of the SPC diver to get the count with one of the smaller species that school in their many of thousands, quite likely a cute little 3 cm Chromis vanderbilti. Either way, it is a major landmark for our program and we look forward to seeing which lucky diver will count that fish.

Image 5: A small school of Chromis vanderbilti huddle near the seafloor. Photo by Kevin Lino

Image 5: A small school of Chromis vanderbilti huddle near the seafloor. Photo by Kevin Lino

Our first stop, Jarvis Island, is one of the most pristine reef environments I have ever seen. In the waters surrounding the mostly barren sands above, is a flourishing ecosystem partially driven by upwelling of cold and nutrient rich water from deeper in the ocean. In such productive waters, tens or even hundreds of large sharks, jacks, and manta rays are likely to appear alongside our divers the moment they enter the water. Just off the bottom, the real work begins as thousands of anthias, chromis, and other small species abound in the rugose benthos of healthy corals and algae. After six days at Jarvis, we voyage north toward the masses of fish at Palmyra Atoll and Kingman Reef for the last 12 days of surveys. Both of these remote areas are also quite unique, hosting an abundance of biodiversity to keep divers busy, while getting closer to that fortunate five millionth fish.

We are grateful for the nearly 80 scientists who have worked together to get us this far. One of whom has counted nearly 500,000 more fish than her next highest counterpart. In the last decade working with CRED, Paula Ayotte has rarely missed an opportunity to go to sea and spend hours underwater during these missions. If we had a Hall of Fame, she would be inducted unanimously for so many reasons: not only for counting nearly a million fish on her own, but also for making sure all other divers are trained, and mostly for being the most entertaining dive buddy you could hope for. It has been a pleasure working with her for that time and while it would be nice to be the diver to count the 5,000,000 fish… I’m hoping that Paula gets that count with a three meter manta ray at Jarvis.

Image 6: A Giant Manta (Manta birostris) curiously swims over a diver during a survey. Photo by Kevin Lino

Image 6: A Giant Manta (Manta birostris) curiously swims over a diver during a survey. Photo by Kevin Lino

Image 7: Diver Paula Ayotte amongst a healthy school of Whitebar Surgeonfish (Acanthurus leucopareius) and Convict Tang (A. triostegus) while conducting an SPC dive.

Image 7: Diver Paula Ayotte amongst a healthy school of Whitebar Surgeonfish (Acanthurus leucopareius) and Convict Tang (A. triostegus) while conducting an SPC dive.

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.

 

Coral reef monitoring in the Mariana Archipelago: preliminary results from visual surveys of fishes and benthic habitats

By Kathryn Dennis and Bernardo Vargas-Ángel

The PIFSC cruise HA-14-01 officially concluded yesterday, Monday, June 2, when the NOAA Ship Hi`ialakai arrived back at Ford Island, Pearl Harbor, from Saipan. During this expedition, which began on March 5, scientists from the PIFSC Coral Reef Ecosystem Division (CRED) and partners conducted ecological surveys, collected water samples, and deployed monitoring instruments and platforms at Wake Island and in the Mariana Archipelago as part of the CRED-led Pacific Reef Assessment and Monitoring Program (Pacific RAMP). As a part of the National Coral Reef Monitoring Plan of NOAA’s Coral Reef Monitoring Program, researchers established climate monitoring stations at 4 islands in the Mariana Archipelago and at Wake Island, where integrated activities provide for long-term collection of data on ocean temperature, chemical composition, benthic cover, calcification, bioerosion, and biodiversity to monitor the effects of climate change and ocean acidification.

The volcano on the island of Pagan emits plumes of gas and steam on the evening of April 20, as seen in this photo taken during the PIFSC cruise HA-14-01. NOAA photo

The volcano on the island of Pagan emits plumes of gas and steam on the evening of April 20, as seen in this photo taken during the PIFSC cruise HA-14-01. NOAA photo

From March 25 to May 6, during Legs II and III and part of Leg I of this latest research cruise at Guam and the Commonwealth of the Northern Mariana Islands (CNMI), CRED scientists and partners completed 100 broad-scale towed-diver surveys, covering more than 220 km of coastline and, at Rapid Ecological Assessment (REA) sites, conducted 329 fish surveys and 158 benthic surveys. Members of the CRED Climate and Ocean Change Team installed 15 climate monitoring stations around Guam, Saipan, Pagan, and Maug, deploying 15 subsurface temperature recorders (STRs), 55 calcification accretion units (CAUs), 45 autonomous reef monitoring structures (ARMS), and 75 bioersion monitoring units (BMUs)—in addition to installations of 70 CAUs at supplementary monitoring sites and 55 STRs at strategic locales associated with climate monitoring stations and long-term (>9 years) time series. For a summary of activities conducted and preliminary results from REA surveys at Wake Island during Leg I, go to the previous blog post published on April 10.

A cursory review (prior to the data being fully analyzed) did not reveal any observations of notable changes in the structure of the fish and benthic communities, in comparison with survey results from the previous Pacific RAMP cruise in the Mariana Archipelago in 2011, at Rota, Aguijan, Tinian, Saipan, Sarigan, Guguan, Alamagan, Pagan, Asuncion, Maug, and Farallon de Pajaros in the CNMI or at Guam are reported at this time. However, unusual cold-water temperatures (~17°C) were experienced at Asuncion, Maug, and Farallon de Pajaros, as was volcanic activity that originated mainly from Ahyi Seamount located nearly 18 km southeast of Farallon de Pajaros.

Preliminary results from the surveys at REA sites of fishes and benthic habitat conducted at depths of 0–30 m by scuba divers from the CRED Fish Ecology Team during the PIFSC cruise HA-14-01 are provided in the fish monitoring brief below. The islands on the Mariana Arc can be divided into 2 groups: the old southern islands and the young, volcanic northern islands. The summary below also was published on May 23 (and is available for download) as 2 separate 2-page PIFSC Data Reports, one for the southern islands of this archipelago and the other for the northern islands.

Pacific Reef Assessment and Monitoring Program
Fish monitoring brief: Mariana Archipelago 2014

By Adel Heenan

About this summary brief

The purpose of this document is to outline the most recent survey efforts conducted by the Coral Reef Ecosystem Division (CRED) of the NOAA Pacific Islands Fisheries Science Center as part of the long-term monitoring program known as the Pacific Reef Assessment and Monitoring Program (Pacific RAMP). More detailed survey results will be available in a forthcoming annual status report.

Sampling effort in the southern islands

  • Ecological monitoring took place in the southern Mariana Archipelago from March 25 2014 to May 07 2014.
  • Data were collected at 178 sites. Surveys were con- ducted at Saipan (n=11), Tinian (n=19), Aguijan (n=10), Rota (n=28), and Guam (n=73).
  • At each site, the fish assemblage was surveyed by underwater visual census and the benthic community was assessed.

Sampling effort in the northern islands

  • Ecological monitoring took place in the northern Mariana Archipelago from April 19 2014 to May 06 2014.
  • Data were collected at 148 sites. Surveys were conducted at Farallon de Pajaros (FDP) (n=11), Maug (n=40), Asuncion (n=21), Pagan (n=43), Alamagan (n=11), Guguan (n=11), and Sarigan (n=11).
  • At each site, the fish assemblage was surveyed by underwater visual census and the benthic community was assessed.

Overview of data collected

Figure 1. Mean total fish biomass at sites surveyed in the southern islands.

Figure 1. Mean total fish biomass at sites surveyed in the southern islands.

Figure 2. Mean total fish biomass at sites surveyed in the northern islands.

Figure 2. Mean total fish biomass at sites surveyed in the northern islands.

Figure 3. Mean hard coral cover at sites surveyed in the southern islands.

Figure 3. Mean hard coral cover at sites surveyed in the southern islands.

Figure 4. Mean hard coral cover at sites surveyed in the northern islands.

Figure 4. Mean hard coral cover at sites surveyed in the northern islands.

Preliminary results for fish biomass also are presented by consumer group and size class. Primary consumers include herbivores (which eat plants) and detritivores (which bottom feed on detritus), and secondary consumers are largely omnivores (which mostly eat a variety of fishes and invertebrates) and invertivores (which eat invertebrates).

Figure 5. Mean consumer group fish biomass (± standard error) at sites surveyed in the southern islands. Primary consumers are herbivores and detritivores, and secondary consumers are omnivores and invertivores.

Figure 5. Mean fish biomass (± standard error) by consumer group at sites surveyed in the southern islands. Primary consumers are herbivores and detritivores, and secondary consumers are omnivores and invertivores.

Figure 6. Mean consumer group fish biomass (± standard error) at sites surveyed in the northern islands. Primary consumers are herbivores and detritivores, and secondary consumers are omnivores and invertivores.

Figure 6. Mean fish biomass (± standard error) by consumer group at sites surveyed in the northern islands. Primary consumers are herbivores and detritivores, and secondary consumers are omnivores and invertivores.

Figure 7. Mean fish biomass per size class (± standard error) at sites surveyed in the southern islands. Fish measured by total length (TL) in centimeters (cm).

Figure 7. Mean fish biomass per size class (± standard error) at sites surveyed in the southern islands. Fish measured by total length (TL) in centimeters (cm).

Figure 8. Mean fish biomass per size class (± standard error) at sites surveyed in the northern islands. Fish measured by total length (TL) in centimeters (cm).

Figure 8. Mean fish biomass per size class (± standard error) at sites surveyed in the northern islands. Fish measured by total length (TL) in centimeters (cm).

Spatial sample design

Survey site locations are randomly selected using a depth-stratified design. During cruise planning and the cruise itself, logistic and weather conditions factor into the allocation of monitoring effort around sectors of each island or atoll. The geographic coordinates of sample sites are then randomly drawn from a map of the area of target habitat per study area. The target habitat is hard-bottom reef, the study area is typically an island or atoll, or in the case of larger islands, sectors per island, and the depth strata are shallow (0–6 m), mid (6–18 m), and deep (18–30 m).

Sampling methods

A pair of divers surveys the fish assemblage at each site using a stationary-point-count method (Fig. 9). Each diver identifies, enumerates, and estimates the total length of fishes within a visually estimated 15-m-diameter cylinder with the diver stationed in the center. These data are used to calculate fish biomass per unit area (g m–2) for each species. Mean biomass estimates per island are calculated by weighting averages by the area per strata. Island-scale estimates presented here represent only the areas surveyed during this cruise. For gaps or areas not surveyed during this cruise, data from this and other survey efforts generally will be pooled to improve island-scale estimates.

Each diver also conducts a rapid visual assessment of reef composition, by estimating the percent cover of major benthic functional groups (encrusting algae, fleshy macroalgae, hard corals, turf algae, and soft corals) in each cylinder. Divers also estimate the complexity of the surface of the reef structure, and they take photos along a transect line at each site that are archived to allow for future analysis.

Figure 9. Method used to monitor fish assemblage and benthic communities at the Rapid Ecological Assessment (REA) sites.

Figure 9. Method used to monitor fish assemblage and benthic communities at Rapid Ecological Assessment (REA) sites.

About the monitoring program

Pacific RAMP forms a key part of the National Coral Reef Monitoring Plan of NOAA’s Coral Reef Conservation Program (CRCP), providing integrated, consistent, and comparable data across U.S. Pacific islands and atolls. CRCP monitoring efforts have these aims:

  • Document the status of reef species of ecological and economic importance
  • Track and assess changes in reef communities in response to environmental stressors or human activities
  • Evaluate the effectiveness of specific management strategies and identify actions for future and adaptive responses In addition to the fish community surveys outlined here, Pacific RAMP efforts include interdisciplinary monitoring of oceanographic conditions, coral reef habitat assessments, and mapping. Most data are available upon request.

For more information

Coral Reef Conservation Program: http://coralreef.noaa.gov

Pacific Islands Fisheries Science Center: http://www.pifsc.noaa.gov/

CRED publications: http://www.pifsc.noaa.gov/pubs/credpub.php

CRED fish team: http://www.pifsc.noaa.gov/cred/fish.php

Fish team lead and fish survey data requests: ivor.williams@noaa.gov

 

To download a PDF file of PIFSC Data Report DR-14-009, the fish monitoring brief for the southern islands of the Mariana Archipelago, click here.

To download a PDF file of PIFSC Data Report DR-14-010, the fish monitoring brief for the northern islands of the Mariana Archipelago, click here.