Coastal water quality monitoring combines public-health measurements at beaches with broader assessments of estuaries, sediments, biological condition, nutrients, and contaminants. EPA’s 2023 beach report covers 5,090 monitored or notified beaches during the 2023 swimming season, while the National Coastal Condition Assessment provides a national snapshot of estuarine and Great Lakes nearshore conditions measured in 2015.
Table of contents
- National beach safety results
- Estuarine biological and nutrient condition
- Estuarine contamination and health indicators
- Great Lakes nearshore biology
- Great Lakes eutrophication and sediment
- Fish-tissue contamination and ecological effects
- Beach notifications and possible pollution sources
National beach safety results
EPA reported that U.S. coastal and Great Lakes program beaches were open and safe for swimming 91% of the time during the 2023 swimming season. The monitoring network represented 5,090 beaches and 697,737 available beach days. Beach advisories or closings were reported on 62,131 of those beach days.
Thirty percent of program beaches had at least one advisory or closing: 1,541 of the 5,090 beaches. States, territories, and Tribes issued 8,088 beach advisories or closings during the season. These figures describe notification activity, not a single nationwide concentration measurement, so they are most useful for understanding how often monitoring led to a public warning.
| 2023 beach-monitoring measure | Reported result |
|---|---|
| Program beaches | 5,090 |
| Available beach days | 697,737 |
| Beach days with advisories or closings | 62,131 |
| Beaches with at least one advisory or closing | 1,541, or 30% |
| Total advisories or closings issued | 8,088 |
| Beaches open and safe for swimming | 91% of the time |
Seventy-seven percent of 2023 notification actions ended within a week after bacteria levels no longer exceeded applicable standards or advisory thresholds. The timing matters when interpreting beach closures: a notification can reflect a temporary condition that is resolved after follow-up monitoring, rather than a persistent failure across the entire swimming season.
Source: EPA’s Beach Report: 2023 Swimming Season, 2023 swimming season.
Estuarine biological and nutrient condition
The 2015 National Coastal Condition Assessment rated 71% of the nation’s estuarine waters good for biological condition. That result sits alongside a weaker picture for eutrophication, the nutrient-related condition indicator. Sixty-six percent of estuarine waters had an increased likelihood of eutrophication impacts.
For the 2015 estuarine eutrophication results, about 51% of waters were in fair condition, 15% were in poor condition, and only 33% were in good condition. These are condition ratings for the 2015 assessment period and should not be read as a current-year trend.
Sediment quality was more favorable in the national estuarine assessment: 76% of estuarine area had good sediment quality in 2015. The contrast between sediment quality and eutrophication condition shows why coastal monitoring uses multiple indicators. A waterbody may have good sediment quality while still showing nutrient-related stress.
The biological and nutrient results can be summarized as follows:
- Biological condition was good in 71% of estuarine waters in 2015.
- Sixty-six percent of estuarine waters had an increased likelihood of eutrophication impacts.
- Eutrophication condition was good in 33%, fair in about 51%, and poor in 15% of estuarine waters.
- Good sediment quality covered 76% of estuarine area in 2015.
Source: National Coastal Condition Assessment, 2015.
Estuarine contamination and health indicators
Enterococci monitoring produced a comparatively favorable human-health indicator in 2015. Enterococci levels were at or below EPA’s human-health benchmark in almost 99% of estuarine waters. The regional results were 99% of estuarine area in the Northeast, 99% in the Southeast, 99% in the Gulf, and 98% in the West at or below the benchmark.
Less than 1% of estuarine area was above the enterococci human-health benchmark, and less than 1% was unassessed for enterococci. These results concern the enterococci indicator and its benchmark; they do not replace the other ecological and chemical measurements in the assessment.
The same assessment compared estuarine microcystin results with EPA’s recreational freshwater benchmark of 8 ng/L. All estuarine waters tested in 2015 were at or below that comparison benchmark, although microcystins were detected in 6% of estuarine waters. Detection and exceeding a comparison benchmark are different measurements, so both figures are relevant.
Fish-fillet mercury results were less complete and more mixed. Fifty-five percent of estuarine area had concentrations at or below the 300 ppb benchmark, 2% was above the benchmark, and 43% was unassessed for the fish-fillet mercury indicator. In the Northeast, 60% of estuarine area was at or below the benchmark.
| Estuarine indicator, 2015 | Reported result |
|---|---|
| Area at or below enterococci benchmark | Almost 99% |
| Area above enterococci benchmark | Less than 1% |
| Area unassessed for enterococci | Less than 1% |
| Microcystin comparison benchmark | 8 ng/L |
| Estuarine waters with microcystins detected | 6% |
| Fish-fillet mercury at or below 300 ppb | 55% of estuarine area |
| Fish-fillet mercury above 300 ppb | 2% of estuarine area |
| Fish-fillet mercury unassessed | 43% of estuarine area |
Source: National Coastal Condition Assessment, 2015.
Great Lakes nearshore biology
The Great Lakes nearshore assessment shows substantial variation by indicator and lake. In 2015, 31% of total Great Lakes nearshore area had good biological condition, 15% had fair biological condition, and 21% had poor biological condition. One-third, or 33%, could not be assessed biologically.
Good biological condition varied sharply among the named lakes. Lake Michigan had 45% of its nearshore area in good biological condition, followed by Lake Superior at 40%. Lake Erie was at 13%, and Lake Ontario at 10%.
The assessment also provides a 2010–2015 comparison for the total Great Lakes nearshore area: the share rated good biologically rose from 22% in 2010 to 31% in 2015. This is a comparison between the reported assessment periods, not a forecast of later conditions.
| Great Lakes nearshore area | Good biological condition in 2015 |
|---|---|
| Total nearshore area | 31% |
| Lake Superior | 40% |
| Lake Michigan | 45% |
| Lake Erie | 13% |
| Lake Ontario | 10% |
Source: National Coastal Condition Assessment, 2015.
Great Lakes eutrophication and sediment
The Great Lakes eutrophication index rated 54% of total nearshore area good in 2015. Lake Superior and Lake Michigan each had 62% of nearshore area in good eutrophication condition. Lake Ontario had 61%, Lake Huron had 48%, and Lake Erie had 23%.
The lake-level pattern is different from the biological-condition pattern. Lake Erie had 13% of nearshore area in good biological condition and 23% in good eutrophication condition, while Lake Ontario had 10% and 61%, respectively. The two indicators therefore describe different dimensions of nearshore condition.
Sediment quality in total Great Lakes nearshore area was good in 62%, fair in 15%, and poor in 2% in 2015. Sediment quality was not assessed in 21% of nearshore area. The share rated good for sediment quality increased by 11 percentage points from 2010 to 2015.
Key Great Lakes eutrophication results were:
- Good condition covered 54% of total nearshore area.
- Good condition covered 62% of Lake Superior, 62% of Lake Michigan, 48% of Lake Huron, 23% of Lake Erie, and 61% of Lake Ontario.
Key sediment results were:
- Good sediment quality covered 62% of total nearshore area.
- Fair sediment quality covered 15%, and poor sediment quality covered 2%.
- Twenty-one percent of nearshore area was not assessed for sediment quality.
- The good sediment-quality share increased by 11 percentage points between 2010 and 2015.
Source: National Coastal Condition Assessment, 2010–2015 comparisons and 2015 results.
Fish-tissue contamination and ecological effects
Fish-tissue contamination was a major concern in the Great Lakes nearshore results. In 2015, 17% of Great Lakes nearshore area had fish-tissue contamination rated good for ecological effects, 19% was rated fair, and 47% was rated poor. The indicator was unassessed in 17% of nearshore area.
EPA reported that wildlife depending on fish may have experienced adverse effects in 66% of Great Lakes nearshore area in 2015. That ecological-effects statistic should be kept separate from the beach-safety results: it reflects fish-tissue contamination across nearshore area, not the number of beach days with a notification.
Microcystins were detected in 31% of Great Lakes nearshore waters in 2015. This Great Lakes detection result is distinct from the national estuarine result, where microcystins were detected in 6% of estuarine waters and all tested waters were at or below the 8 ng/L comparison benchmark.
The Great Lakes fish-tissue figures were:
- Good ecological-effects rating: 17% of nearshore area.
- Fair ecological-effects rating: 19%.
- Poor ecological-effects rating: 47%.
- Potential adverse effects for fish-dependent wildlife: 66% of nearshore area.
- Unassessed fish-contamination area: 17%.
Source: National Coastal Condition Assessment, 2015.
Beach notifications and possible pollution sources
EPA’s 2023 beach report also categorized reported possible pollution sources associated with beach notifications. Unknown sources accounted for 41% of reported possible pollution sources. Stormwater runoff accounted for 20%, with 1,207 source reports. Wildlife accounted for 7%, with 427 reports; dry-weather runoff accounted for 4%, with 264 reports; and boat discharge accounted for 3%, with 199 reports.
Algae accounted for less than 1% of reported possible pollution sources, with 17 source reports. These are reported possible sources associated with notifications, not a complete measurement of every pollutant entering coastal waters.
| Reported possible source | Share or count in 2023 |
|---|---|
| Unknown | 41% |
| Stormwater runoff | 20%; 1,207 reports |
| Wildlife | 7%; 427 reports |
| Dry-weather runoff | 4%; 264 reports |
| Boat discharge | 3%; 199 reports |
| Algae | Less than 1%; 17 reports |
Taken together, these monitoring statistics show why coastal conservation relies on repeated, indicator-specific measurement. Beach notifications describe short-term recreational exposure decisions during the 2023 swimming season. The 2015 national assessment adds biological condition, eutrophication, sediment quality, enterococci, microcystins, mercury, and fish-tissue effects across estuarine and Great Lakes nearshore areas. Each result retains its own geography, measurement period, benchmark, and assessment scope.
Source: EPA’s Beach Report: 2023 Swimming Season, 2023 swimming season; National Coastal Condition Assessment, 2015.