Looe Key

Setting

Looe Key Sanctuary Preservation Area, south of Big Pine Key — the classic Lower Keys spur-and-groove reef, dived twice on 9 December 2021 (09:41 and 10:50; 9.8 m maximum, 26.1–26.3°C average, 48 and 56 minutes).

General benthic features

The photographs show a reef whose architecture is largely relict and whose living coral is concentrated in the shallowest zones. Limestone spurs run seaward between white sand grooves; most spur flanks are old framework skinned in pink crustose coralline algae and turf, with sea fans (Gorgonia ventalina), sea plumes and sea rods standing in dense stands over it. Where living stony coral does hold ground it does so emphatically: several meter-scale Orbicella-group boulder heads sit intact on the spur tops with tissue over the whole dome, and both bladed and branching fire coral (Millepora complanata / M. alcicornis) form waist- to chest-high stands. The shallowest crests carry near-continuous carpets of the zoanthid Palythoa (Anderson's identification), mounded mats of large separate polyps that almost surround some of the stony colonies. Living elkhorn coral (Acropora palmata) is present on the shallow fore-reef in several separate colonies. An in-water staghorn nursery — Acropora cervicornis fragments strung on line droppers from multiple tree structures (e.g., Image 21, Image 22) — stands over sand nearby, and a numbered outplant disk sits on the pavement beside a linear staghorn array (e.g., Image 10).

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A heavily corroded iron anchor lies in one sand groove among encrusted rubble; the reef takes its name from HMS Looe, which ran aground here in 1744, but nothing visible on the anchor dates or attributes it (e.g., Image 23).

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Coral cover

• Reference: Claude CV point count (this site's photos)
• Coral cover: 20% — a blind Claude computer-vision point count of 108 of Anderson's edited photographs (20 points per photo; water, fish, and obstructions excluded). Other computer-vision methods are listed in the method table. Nothing below is a cover estimate — the habitat notes describe what is in the frames, not what fraction of the benthos it covers, and cover is deliberately not eyeballed from photographs.

Stressors

One massive colony carries two tissue-loss lesions consistent with stony coral tissue loss disease (SCTLD), each a ring of freshly exposed white skeleton between live tissue and an older, turf-covered dead center (e.g., Image 26).

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The zoanthid Palythoa carpets on the shallowest crests almost surround some of the stony colonies there. An invasive lionfish was photographed on the reef pavement (Anderson's identification) (e.g., Image 18).

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No corallivores were evident.

Fish and other fauna

Fish were abundant throughout — sergeant majors in loose clouds, bluehead and yellowhead wrasse, blue tang, blue chromis, yellowtail snapper, a great barracuda on both dives, an invasive lionfish, and a spotted eagle ray crossing the reef (e.g., Image 24, Image 25); the barracuda hangs low over the sand in Image 3.

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Comparisons with other data

NOAA NCRMP Florida surveyed this site (FLK PSU 8195-1) in 2024, 0.07 km from the pin. Within 5 km, 37 independent stations recorded station-year means of 0.0–39% hard coral cover between 1996 and 2024; the nearest, NOAA NCRMP Florida at FLK PSU 8195-1, 0.07 km away, read 4.0% in 2024.