Gray’s Reef National Marine Sanctuary: Summary of Resource Conditions

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, and 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:

Pressures

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

Status Description: Few or no activities occur that are likely to negatively affect water quality.

Rationale: Salt marsh cover remained stable in coastal Georgia, although impervious surface cover increased slightly. Vessel registrations in coastal Georgia increased from 2015–2021, potentially increasing the risk of vessel discharge within the vicinity of the sanctuary. However, no spills were reported in GRNMS from 2008–2022.

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

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

Rationale: Activities that could harm habitats, including recreational fishing, research activities, and scuba diving, occur regularly at GRNMS. However, available data suggest they did not occur at levels that resulted in measurable habitat impacts during the study period.

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

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

Rationale: Vessel registrations and activity increased during the study period, but vessel activity was generally seasonal, peaking in summer. The majority of vessels visiting the sanctuary engaged in fishing. The number of recreational fishing trips and landings in federal waters offshore of Georgia were higher during the current study period compared to historical levels; trends were stable during the study period, except for an increase in the number of fish caught and released. Recreational fishing information and fishery-independent data specific to GRNMS were lacking, but experts agreed that although fishing pressure should be further examined in the sanctuary, it likely occurred at sustainable levels during the study period.¹

Water Quality

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: Chlorophyll concentration and anomalies varied seasonally but were stable overall, nutrient levels were low, evidence of short-term hypoxia events was limited, and seasonal trends in turbidity and riverine input were consistent.

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: Mercury contamination advisories were issued for one targeted fish species, and one study found heavy metals in biota that exceeded some consumption advisories. No ciguatera fish poisoning cases were reported, and only one day of favorable conditions for Vibrio spp. was observed during the study period for this report. No offshore phytoplankton data were available to assess harmful algal blooms. Many available human health metrics rely on data from outside the sanctuary.

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

Status Description: Climate-related changes are suspected and may degrade some attributes of ecological integrity, but have not yet caused measurable degradation.

Rationale: Changes in a number of key climate parameters (e.g., increasing temperature, increasing storm frequency, increasing CO2) were detected, but no large impacts on or measurable degradation of resources were observed from 2012–2022.

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: No contaminant discharges from vessels were reported within the boundaries of GRNMS during the study period. Discharge of contaminants (primarily petroleum) did occur within 100 kilometers of the sanctuary, although there was no trend in the number of incidents or volume of material released during the study period. No direct sampling of GRNMS waters for contaminants associated with these regional events has occurred, representing an important knowledge gap.

Habitat

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

Status Description: Habitats are in near-pristine condition.

Rationale: Available data suggest no changes to habitat at GRNMS other than those likely from natural processes (e.g., storm activity, sand movement). New and ongoing monitoring is required to increase understanding of the dynamics of sanctuary habitat integrity.

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: Some contaminants were present in GRNMS sediments and biota, but they were detected at low levels that would not be expected to significantly degrade ecological integrity. However, data on contaminants were limited to one or few time points.

Living Resources

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

Status Description: Conflicting signals from indicators prevent the selection of a singular status rating.

Rationale: Select focal fish (red snapper, tomtate, black sea bass, king mackerel) and coral (Oculina arbuscula) species remained stable or improved within GRNMS during the study period. Conversely, North Atlantic right whales are endangered and experienced an unusual mortality event during the study period. For other species, including loggerhead sea turtles, sand tiger sharks, and Halymenia spp. algae, data were too limited to determine status or trends.²

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: To date, the abundances of non-indigenous species in GRNMS have been low, and impacts have not been observed nor are they suspected. Limited data suggest high variability and no consistent trends across most indicators.

What is the status of biodiversity and how is it changing?

Status Description: Selected biodiversity loss or change is suspected and may preclude full community development and function, but has not yet caused measurable degradation.

Rationale: Biodiversity data were available for fish and invertebrates, but were limited for infauna and macroalgae, which are particularly important, as they are indicators for climate change. Metrics for observed species appeared to be stable; however, there is lack of information regarding species turnover, as well as for observed increases of tropical fishes.

¹ Due to time constraints, a status rating for this question was not determined during the expert workshop. This status rating was determined later by GRNMS staff, who reevaluated the indicators, data sets, and expert input provided during the workshop.

² Due to time constraints, status and trend ratings and associated confidence scores for this question were not determined during the expert workshop. They were determined later by GRNMS staff who reevaluated the indicators, data sets, and expert input provided during the workshop.