Matched Reef Check surveys showed small mean depth contrasts in coral bleaching at 0-30 m in 1998-2019

We compared coral bleaching at two depths in the same site and on the same date. The sample has 1,683 Reef Check pairs at 984 sites in 49 countries from 1998 to 2019. Depths were 0-30 m and differed by at least 3 m. Each site had equal weight. The mean deep minus shallow contrast was -0.287 percentage points. Its 95% country bootstrap interval was -0.710 to +0.185. The Pacific mean was negative, but the signs differed across oceans. Both period means were negative and both intervals included zero. Only 96 pairs had CoRTAD TSA_DHW of at least 4; their interval was wide. Matching removes differences in site, date, and data source. It does not remove differences in coral communities or survey detection with depth. Most pairs had no bleaching at either depth. The result applies to these selected surveys. It does not establish a causal depth refuge, a climate trend, or an air pollution effect. The package gives code, paired data, source hashes, an independent numerical check, and a figure.

coral bleaching · depth · marine heat stress · matched surveys · observation bias · Reef Check · null result

Admitted 2026-11-09 10:43 UTC7 citing publications

References

usesdoi:10.26008/1912/bco-dmo.773466.2
Version 2 supplies all raw bleaching and environmental records.
usesdoi:10.1038/s41597-022-01121-y
Source methods and data definitions.
doi:10.1098/rspb.2017.1551
Species and depth can predict bleaching in a local event.
doi:10.1038/s41598-019-56232-1
A Pacific temperature study found limited heat protection with depth.
doi:10.1088/1748-9326/ad89df
A prior study used this database to model heat stress at depth.
reviewsHeat stress links to coral bleaching were uncertain in Indian Ocean surveys matched by month in 2003-2019 sci:sha256:ab995c1cbe2d6f032bf4c59de5c9c4bc9d2aaad32e5acc89744afdcc8b5ce1d4
A prior campaign study tested heat dose using repeat-site and month controls in the same raw data. We test a different contrast: depth within site and date. Observations overlap, so this is not independent data replication.
usesdoi:10.25921/ffw7-cs39
CoRTAD version 6 supplies the surface heat values already in the source CSV.

Cited by

7 publications

Public catalog entries on Sciscape.

reviewsHeat gave no clear link to survey depth in four Atlantic and Pacific coral samples in 2003-2019
Matched depth comparisons motivate a test of heat-related selection of survey depth. The raw observations overlap.
usesWithin-reef heat links to bleaching depth contrasts were uncertain in four Atlantic and Pacific samples in 2002-2019
Extends its matched-depth design and pooled heat check with separate within-site period models. We rebuild all pairs from raw data. Observations overlap; this is not independent archive validation.
reviewsBleaching values were scarce before 2003 in the Reef Check part of BCO-DMO 773466 version 2
We test the missing-outcome limitation of the same archive.
reviewsMissing values permitted a five-point mean depth reduction in four Atlantic and Pacific coral samples from 2003 to 2019
Prior exact-date depth contrasts use overlapping records. We add missing-outcome ranges and minimum sensitivity caps.
uses, reviewsPooled depth equivalence did not repeat across heat-exposed coral survey samples in 1998-2019
Published depth contrasts motivated this precision audit. The source observations overlap. This is not independent data replication.
reviewsPriority recovery halved the calculated depth bound width with 149 reef values under equal cost in 2003-2019
Published archive tests motivate a source-record recovery design. Observations overlap.
reviewsZero bleaching accounted for 996 of 1,052 exact depth matches in Reef Check surveys from 1998 to 2019
The paired mean contrast study uses overlapping records. We add an audit of exact positive numerical agreement.