2007-2020 NMSAS Summary of Resource Conditions
National Marine Sanctuary of American Samoa

The various resource status and trend evaluations presented in this report are summarized below. Each question used to rate the condition of and trends in sanctuary resources is listed, followed by:

1. A set of rating symbols that display key information. The first symbol includes a color and term to indicate status. The next symbol indicates trend. A shaded scale adjacent to both symbols indicates confidence (see key for example and definitions).


2. The status description, which is a statement that best characterizes resource status and corresponds to the assigned color rating and definition as described in Appendix A. The status description statements are customized for all possible ratings for each question.


3. The rationale, which is a short statement or list of criteria used to justify the rating.

Key:

Water Quality

Question 1: What is the eutrophic condition of sanctuary waters and how is it changing?

Status Description: Eutrophication has not been documented, or does not appear to have the potential to negatively affect ecological integrity.

Rationale: Data on eutrophication are limited, but available data suggest that nitrogen, phosphorus, and chlorophyll a concentrations remain below recommended threshold levels in sanctuary waters. However, dissolved inorganic nitrogen may be increasing in Fagatele Bay based on the most recent data. Macroalgae cover was evaluated as a proxy for nutrients and has been variable over the reporting period, but remains low overall within sanctuary units.

Question 2: Do sanctuary waters pose risks to human health and how are they changing?

Status Description: One or more water quality indicators suggest the potential for human health impacts, but human health impacts have not been reported.

Rationale: There are currently no known human health risks from NMSAS waters; however, data are limited and no trend data are available. Contaminants were detected in Fagatele Bay, but only nickel concentrations exceeded toxicology screening levels. Coliform bacteria have been detected in Fagatele Bay, and there is a sewage outfall in the Aunu’u Multipurpose Zone, but sanctuary units are not part of regular water sampling efforts, so any potential health impact is unknown. No ciguatera poisoning has been reported from fish caught in the sanctuary.

Question 3: Have recent, accelerated changes in climate altered water conditions and how are they changing?

Status Description: Climate-related changes have caused measurable, but not severe, degradation in some attributes of ecological integrity.

Rationale: Increasing sea surface temperatures have caused more frequent and more severe coral bleaching events. Ocean acidification is affecting water quality worldwide; however, aragonite saturation state and calcification rates have remained high in sanctuary units.

Question 4: Are other stressors, individually or in combination, affecting water quality, and how are they changing?

Status Description: Selected stressors are suspected and may degrade some attributes of ecological integrity, but have not yet caused measurable degradation.

Rationale: Nonpoint source pollution from landfill activity, agriculture, and development was raised as a concern for Tutuila and Aunu’u units; however, managers did not detect major impacts to the ecological integrity of these sites during the reporting period. Accelerated coastal erosion caused by subsidence has not caused significant deposition. Iron enrichment at a vessel grounding site continues to be a problem at Rose Atoll, but has improved. Bird populations at Rose Atoll have varied somewhat due to storms, but these fluctuations do not appear to have disturbed nutrient cycles around the atoll.

Question 5: What are the levels of human activities that may adversely influence water quality and how are they changing?

Status Description: Some potentially harmful activities exist, but they have not been shown to degrade water quality.

Rationale: There are measurable contaminant and nutrient inputs within NMSAS units, particularly in Fagatele Bay. Contaminants and nutrients from a landfill and agricultural activities have been documented at low levels in Fagatele Bay and it is likely that they have also reached Fagalua/Fogama’a. No measurable impact on water quality or biological communities has been detected. There is a sewage outfall in the Aunu’u Multipurpose Zone A Unit that may also discharge contaminants and nutrients to the shallow reef zone. Limited data prevent full assessment of these impacts and no trend data were available to assess changes over time.

Habitat Resources

Question 6: What is the integrity of major habitat types and how are they changing?

Status Description: Selected habitat loss or alteration is suspected and may degrade some attributes of ecological integrity, but has not yet caused measurable degradation.

Rationale: Habitats within NMSAS have demonstrated resilience to disturbances from coral bleaching events, sea level rise, crown-of-thorns sea stars, and cyclones. These ecosystems have adapted to or recovered from these events. The damage from a vessel grounding in Aunu’u has had lasting impacts, but is constrained to a small area, and marine debris continues to be a chronic but minor problem across all habitats. Data for pelagic and deep-sea habitats are limited, and no immediate threats were identified.

Question 7: What are contaminant concentrations in sanctuary habitats and how are they changing?

Status Description: Selected contaminants are suspected and may degrade some attributes of ecological integrity, but have not yet caused measurable degradation.

Rationale: Data on contaminants within NMSAS are limited. Heavy metals, hydrocarbons, pesticides, and pharmaceuticals were detected in water and sediment in Fagatele Bay in 2018, but only nickel was observed at concentrations above recommended screening levels. Iron contamination from the 1993 grounding at Rose Atoll persists but is limited in scope and continues to improve. As the Fagatele Bay data are from a single point in time and no recent data are available for other sanctuary units, the expert confidence in this rating was medium and experts were unable to determine a trend rating.

Question 8. What are the levels of human activities that may adversely influence habitats and how are they changing?

Status Description: Selected activities have caused measurable resource impacts, but effects are localized and not widespread or persistent.

Rationale: Vessel groundings have had localized effects on coral reef habitat in the Aunu’u and Muliāva units. Destructive fishing practices have not been observed recently, but abandoned fishing gear has been removed from sites on Tutuila. Marine debris is widespread across the sanctuary, but documented habitat impacts have been limited. Deep-sea surveys detected significant marine debris accumulations in the deep sea around Tutuila, but did not detect marine debris in the Muliāva unit. Limited data are available for all sites, particularly for pelagic, mesophotic, and deep-sea habitats.

Living Resources

Question 9: What is the status of keystone and foundation species and how is it changing?

Status Description: The status of keystone and foundation species is mixed.

Rationale: The status of keystone and foundation species varies across taxa. Experts assigned a rating of fair/poor to fish taxa, as the low abundance of large predators and herbivores in shallow coral reef habitats may decrease ecosystem resilience. Benthic foundation species, such as corals and crustose coralline algae, were rated as good/fair. While experts are concerned that low reef fish biomass may eventually impair reef resilience, during this reporting period, benthic foundation species demonstrated an ability to recover after coral bleaching, crown-of-thorns starfish outbreaks, a tsunami, and storms. Data for mesophotic and deep-sea species are limited, but do not indicate degradation of these habitats.

Question 10: What is the status of other focal species and how is it changing?

Status Description: The status of keystone or foundation species is mixed.

Rationale: The abundances of giant clams (Tridacna spp.), targeted food fish species, and humphead wrasse (Cheilinus undulatus) are low, and their recovery is uncertain due to continued harvesting and life cycle characteristics. The continued low abundance of these species resulted in a rating of fair/poor. Giant Porites corals were added after the workshop based on expert recommendation and feedback. The status of these species is good. Data on sea turtles suggest that regional populations are stable and may be slowly recovering, but remain at risk. Sea turtle nesting activity is still limited and may be affected by harvest outside of American Samoa, coastal development, and climate change. Humpback whale populations may be increasing, but data are limited. Additionally, increasing ocean temperatures may be shifting humpback whales’ preferred habitat away from American Samoa. The status of sea turtles and humpback whales was considered fair.

Question 11: What is the status of non-indigenous species and how is it changing?

Status Description: Non-indigenous species are present and may preclude full community development and function, but have not yet caused measurable degradation.

Rationale: Non-indigenous species have been observed in American Samoa, but have not exhibited invasive characteristics within NMSAS units.

Question 12: What is the status of biodiversity and how is it changing?

Status Description: Selected biodiversity loss or change has caused measurable but not severe degradation in some attributes of ecological integrity.

Rationale: Diversity remains high in NMSAS, additional species have been documented, and new species continue to be discovered. Shallow scleractinian coral populations have fluctuated over time due to predation, cyclone, and coral bleaching events, but have proven resilient. Many large, ecologically important fish species are rare throughout the sanctuary, and fish biomass is below island averages in Tutuila units and below estimated biological potential in all units except for Swains Island. Impaired fish community structure may affect overall coral reef ecosystem function, and resilience and was a primary driver for this rating.

Question 13: What are the levels of human activities that may adversely influence living resources and how are they changing?

Status Description: Selected activities have caused measurable resource impacts, but effects are localized and not widespread or persistent.

Rationale: Fishing appears to be a significant pressure on living resources in NMSAS. Experts believe that Fagatele Bay may deserve a fair/poor rating due to low fish biomass observed at the site. Fishing pressure appears to be decreasing, but fish biomass has not increased during the reporting period. Clam populations continue to decline. Sea turtle populations are stable or increasing. Vessel groundings reduced species diversity and abundance at the impact sites in Aunu’u and Rose Atoll. Limited data are available for pelagic, mesophotic, and deep-sea habitats.

Maritime Heritage Resources

Question 14: What is the condition of known maritime heritage resources and how is it changing?

Status Description: The diminished condition of selected maritime heritage resources has reduced, to some extent, their aesthetic, cultural, historical, archaeological, scientific, or educational value, and may affect the eligibility of some sites for listing in the National Register of Historic Places.

Rationale: Maritime heritage resources have not been subject to human impacts that might otherwise diminish their aesthetic, cultural, historical, archaeological, scientific, or educational value. They have been subject to natural deterioration, erosion, and high-energy shoreline events, but have generally not been assessed, documented, or monitored. Therefore, their condition is rated as fair. However, the trend is worsening because maritime heritage resources are subject to ongoing natural forces like erosion and high-energy shoreline events, leading to concern regarding future conditions. Maritime heritage resources like submerged shipwrecks and aircraft, which likely exist within the sanctuary, are presumed to be slowly degrading, primarily due to natural processes.

Question 15: What are the levels of human activities that may adversely affect maritime heritage resources and how are they changing?

Status Description: Some potentially damaging activities may exist, but they have not been shown to degrade maritime heritage resource condition.

Rationale: This question addresses human activities that may have adverse impacts, and is not meant to consider deterioration primarily due to natural processes. Based on observations by participating experts, few activities, either within or adjacent to NMSAS boundaries, are known to have the potential for adverse impacts to maritime heritage resources. Additionally, experts agreed that this low level of adverse activity has not changed since the previous condition report.