NOAA - Bird Key Reef, Dry Tortugas

Setting

At about 15 m (the station depth in the June 2021 cruise notes), Bird Key Reef — 5.1% hard coral cover on NOAA's fixed carbonate-budget transects in June 2024 (7.8% in the 2021 Dry Tortugas CREMP point-count survey) — is the NOAA Dry Tortugas station where the June 2021 cruise ran its instrument suite: gorgonian-draped hard-bottom instrumented with pH, light, and current sensors, sampled for water chemistry every three hours, and revisited dive after dive for transects, mosaics, and carbonate-budget blocks (e.g., Image 3, Image 22, Image 23).

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General benthic features

Between the gear, well-spaced massive coral heads — a mustard Montastraea cavernosa dome, a purple-brown Orbicella faveolata head, meandering brain corals — rise from stands of feathery orange gorgonians (e.g., Image 2, Image 16).

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Coral cover

• Coral cover: 5.1% (± 2.9% SD) in June 2024, from the NOAA NCRMP carbonate-budget (ReefBudget) survey of the site's 6 fixed transects; the same transects read 13% in 2015, 12% in 2018, and 12% in 2021. The FWC-FWRI Dry Tortugas CREMP point-count survey of the site's 4 permanent stations read 7.8% in 2021, the year Anderson dived here, and 4.0% in 2024.

Stressors

One Siderastrea head carries sharp white patches of tissue loss within pigmented tissue (e.g., Image 8, Image 12).

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On the 27 June dives Anderson's photographs show tissue-loss fronts on at least two more massive colonies (live tissue, a band of freshly bare white skeleton, then turf-covered skeleton), consistent with stony coral tissue loss disease (SCTLD), and a recently dead, stark-white ridged colony with bare skeleton and no turf yet, cause not recorded (photos not shown). A dark massive colony carries several small, round pale spots (e.g., Image 10).

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No corallivores were evident.

Comparisons with other data

FWC CREMP (Dry Tortugas, DTCREMP) surveyed this site (Bird Key Reef #821) in 2024, 0.00 km from the pin. Within 5 km, 61 independent stations recorded station-year means of 0.0–49% hard coral cover between 1999 and 2024; the nearest, FWC CREMP (Dry Tortugas, DTCREMP) at Bird Key Reef #821, 0.00 km away, read 4.7–24% between 1999 and 2024.

Other notes

The photographs catch that work mid-stream: transect tape over a coral head, a diver carrying a photo-quadrat frame, gloved hands working an instrument low over the reef (e.g., Image 5, Image 6, Image 24).

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