Florida - Marathon 3
Part of the regional summary: USA - Florida
More info
Florida Keys (NOAA CRW virtual station)Near Marathon, Sombrero Reef, 7 km away, is a lighthouse-marked spur-and-groove bank reef, a Sanctuary Preservation Area, and a Mission: Iconic Reefs restoration site. Closer stations within 2 km, surveyed 2009-2024, are listed on the site page, though none measures this spot.
21 independent survey stations shown with the program’s logo — click one to see how far it is from this site.
Site description
Setting
A site offshore of Marathon and Vaca Key, in the Middle Keys (24.67 N, 81.06 W), where Anderson has dived.
Stressors
No stressor observations are recorded for this site: Anderson's dive log has no entry for it, and no dive date or photograph is on file.
Comparisons with other data
Five Reef Check surveys within 10 km, all from 1997-1998, spanned 6.9-20% hard coral (mean 12%); the nearest of them is Sombrero Reef, 7.00 km away, at 6.9% in 1998. Closer monitoring stations run much later: the 5 km table below lists 21 stations surveyed between 1996 and 2024, the nearest being NOAA NCRMP FLK-240 and FLK-301 (0.63 km; 37% in 2014, 29% in 2015) and FWC CREMP's four Thor stations (0.91 km; 6.6–25% between 2009 and 2024). Sombrero Reef is a spur-and-groove bank reef marked by its lighthouse, a Sanctuary Preservation Area, and one of the seven target sites of NOAA's Mission: Iconic Reefs restoration program.
No underwater photographs from this site are on file.
Independent surveys nearby
| Agency / program | Year(s) | Stations / distance | Link |
|---|---|---|---|
| FWC CREMP (Florida Keys) | 1996–2024 | 8 stations, 0.91–3.78 km | Records ↓ |
| NOAA NCRMP | 2014–2016 | 11 stations, 0.63–4.43 km | Records ↓ |
| NOAA NCRMP Florida | 2024 | 2 stations, 2.99–3.61 km | Records ↓ |
Within 5 km, 21 independent survey stations recorded hard coral cover in 177 records between 1996 and 2024. Of the 8 stations surveyed in more than one year, 7 declined (by 0.8–9.0 points) and 1 increased (by 7.0 points) between their first and latest surveys. Four stations share the longest span (1996–2024); one, Dustan Rocks #352 (FWC CREMP (Florida Keys), 3.78 km away), went from 22% in 1996 to 13% in 2024. Since 2021, station-year means average 12% (range 1.0–20%; n = 34 station-years from 34 records).
Collected by other programs using different methods (NOAA rows come from NOAA monitoring programs (NCRMP, PIFSC, NCCOS), and each row's method is in its hover text; FWC-FWRI uses fixed-station point counts), so these are context for the figures above, not a like-for-like comparison. Where a station was surveyed more than once, the cell shows either the range of its values or, as a single value, the mean of surveys made in one year. Station names are not dive-site names.
Show all 177 independent survey records
| Agency | Site / location | Date | Hard coral cover (%) | Distance | Link |
|---|---|---|---|---|---|
| FWC CREMP (Florida Keys) | Dustan Rocks #351 | 1996–2024 | 7.5–19% (19 surveys) | 3.78 km | — |
| FWC CREMP (Florida Keys) | Dustan Rocks #352 | 1996–2024 | 9.8–22% (29 surveys) | 3.78 km | — |
| FWC CREMP (Florida Keys) | Dustan Rocks #353 | 1996–2024 | 8.1–14% (29 surveys) | 3.78 km | — |
| FWC CREMP (Florida Keys) | Dustan Rocks #354 | 1996–2024 | 13–24% (29 surveys) | 3.78 km | — |
| FWC CREMP (Florida Keys) | Thor #241 | 2009–2024 | 7.2–21% (16 surveys) | 0.91 km | — |
| FWC CREMP (Florida Keys) | Thor #242 | 2009–2024 | 9.7–18% (16 surveys) | 0.91 km | — |
| NOAA NCRMP | FLK-240 | 2014 | 37% | 0.63 km | — |
| FWC CREMP (Florida Keys) | Thor #243 | 2014–2024 | 6.6–14% (11 surveys) | 0.91 km | — |
| FWC CREMP (Florida Keys) | Thor #244 | 2014–2024 | 13–25% (11 surveys) | 0.91 km | — |
| NOAA NCRMP | FLK-242 | 2014 | 29% (2 records) | 1.46 km | — |
| NOAA NCRMP | FLK-239 | 2014 | 34% (2 records) | 2.33 km | — |
| NOAA NCRMP | FLK-243 | 2014 | 17% | 2.84 km | — |
| NOAA NCRMP | FLK-244 | 2014 | 2.0% | 3.17 km | — |
| NOAA NCRMP | FLK-238 | 2014 | 8.5% (2 records) | 4.43 km | — |
| NOAA NCRMP | FLK-301 | 2015 | 29% | 0.63 km | — |
| NOAA NCRMP | FLK-302 | 2015 | 4.0% (2 records) | 4.06 km | — |
| NOAA NCRMP | FLK-398 | 2016 | 5.0% | 2.84 km | — |
| NOAA NCRMP | FLK-399 | 2016 | 16% | 3.17 km | — |
| NOAA NCRMP | FLK-400 | 2016 | 5.0% | 4.06 km | — |
| NOAA NCRMP Florida | FLK PSU 1801-1 | 2024 | 1.0% | 2.99 km | NCEI 0306238 |
| NOAA NCRMP Florida | FLK PSU 1566-1 | 2024 | 4.0% | 3.61 km | NCEI 0306238 |
Long-term monitoring nearby: FWC Coral Reef Evaluation and Monitoring Project
One FWC monitoring site lies within 2 km of this site.
Stony coral cover
Stony coral covered 10% ± 1.5 at Thor in 2024 (mean ± SE of 4 stations; 14% in 2009).
What covers the bottom (2024)
| Group | Thor |
|---|---|
| Stony coral | 10% ± 1.5 |
| Octocorals | 1.1% ± 0.4 |
| Macroalgae | 4.1% ± 0.8 |
| Sponges | 9.5% ± 1.0 |
| Zoanthids | 2.0% ± 0.4 |
| Cyanobacteria | 0.9% ± 0.1 |
| Bare substrate | 72% ± 2.0 |
Mean ± SE percentage of bottom area. Most common stony corals by cover: Thor: Montastraea cavernosa 4.2%; Siderastrea siderea 4.2%; Stephanocoenia intersepta 1.1%.
Coral colonies: number, size, and recruits
| Thor | |
|---|---|
| Colonies per m² | 8.7 (2011) → 9.4 ± 0.9 (2024) |
| Juvenile colonies per station | 40 (2018) → 118 ± 25 colonies (2024) |
Living stony coral tissue area, m² per station (estimated from colony size)
Thor: 8.8 m² per station in 2011, 6.4 m² in 2024.
Bleaching and disease in surveyed colonies
| Year | Thor | |
|---|---|---|
| Bleached or pale | Diseased | |
| 2011 | 2% May | 1% |
| 2012 | 5% May | 1% |
| 2013 | 5% May | 1% |
| 2014 | 20% Aug | 2% |
| 2015 | 5% May | 2% |
| 2016 | 3% May | 1% |
| 2017 | 5% May | 1% |
| 2018 | 22% Jun | 7% (SCTLD 19) |
| 2019 | 5% May | 2% (SCTLD 1) |
| 2020 | 9% Sep | 1% |
| 2021 | 4% May | 2% (SCTLD 4) |
| 2022 | 11% May | 1% (SCTLD 1) |
| 2023 | 7% May | 1% |
| 2024 | 20% May | 2% |
Share of surveyed stony coral colonies that FWC recorded as bleached, partly bleached, or pale, and with any disease; the survey month is beside each bleaching value, because FWC's survey month varies between years and bleaching shares are comparable only within a season. SCTLD = stony coral tissue loss disease (number of colonies).
Water temperature at the reef (in-situ loggers)
Mean temperature of the warmest month each year, complete logger years only. Averaged over 2011–2023, the annual mean was 27.2°C at Thor.
Surveys and data: Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute (FWC), Coral Reef Evaluation and Monitoring Project (CREMP); FWC CREMP 2024 data release (2025), gis.myfwc.com. Each FWC site is shown on its own and is not combined with other programs' surveys.
Data & links
Data on this page are from the organizations named in the data sources above, not Coral Reef Diagnostics; Coral Reef Diagnostics has no coral cover estimate of its own at this site.
© Coral Reef Diagnostics.