Alkalinity: calcification is not the same as extension or safety
Acropora cervicornis
Names as reported by the authors; no accepted-taxon or specimen-identity claim.
Reading the evidence
These records describe traits and results under specific study conditions. They do not establish recommended aquarium settings.
What the study tells us
Calcification increased, but the full-period extension result was not significant after the stated analyses. Actual enrichment differed from intended treatment. This is endpoint and time-window divergence, not an independent-study contradiction or a safe dosing range.
Study conditions
Forty fragments from three SNP-confirmed nursery genotypes, individually maintained in 600 mL beakers; four treatments, nominal ambient about 2500 micromol kg−1 total alkalinity and realized increments labelled +1200, +1850 and +2000 micromol kg−1. Treatments lasted seven weeks; reported growth window 33 days. About 27 degrees C, peak 200 micromol m−2 s−1, regular feeding and automated water replacement. Buoyant weight for calcification; photographs for linear extension.
Methods and evidence class
controlled captive experiment
Buoyant-weight calcification normalized to initial area; photographic linear extension; linear models, genotype mixed-effects analyses and Tukey-adjusted comparisons. Six partially declining corals were removed; rates used their decline day as endpoint.
Findings
obs-pmc13150020-01
Calcification was higher in all alkalinity-enriched groups than ambient, but not significantly different among enriched groups. The reported highest-group mean was 0.83 ± 0.06 versus ambient 0.37 ± 0.05 mg cm−2 day−1 (mean ± SEM).
Across the entire 33-day growth interval, the linear-extension versus alkalinity regression was not significant (p=0.065), and Tukey-adjusted pairwise comparisons were also nonsignificant. The earlier half alone showed a significant positive relationship (p=0.01), so the title's growth benefit must not be treated as an unqualified full-period linear-extension effect.
Where to find it in the paper
Results / Coral response / Total calcification / Linear extension | ./body/sec[2]/sec[2]/sec[1]/sec[1]/p[1]
Results / Coral response / Reduced calcification and linear extension over time | ./body/sec[2]/sec[2]/sec[2]/p[1]
Realized alkalinity increments were substantially below intended +1500/+3000/+4500; the highest two realized groups were not significantly distinct.
Precipitation in stored sample bottles caused exclusions; uncertainty in carbonate chemistry complicates threshold interpretation.
The reported sample counts are internally inconsistent: 859 original, 141 excluded and 642 remaining.
Linear extension significance depends on time window and multiple-comparison correction. Calcification response is not proof of an optimal or safe dosing target; small fragments over weeks, not long-term colony health.
Six corals showed partial tissue loss and were removed during the latter half (two controls, three +1200, one +2000; five same genotype). Limited health measurements cannot establish long-term safety.
All chemistry, calcification and extension measurements are the same experiment; repeated bottle samples are not independent coral genotypes.
Evidence family: study-pmc13150020
Method passage locators
Methods / Coral collection and acclimation | ./body/sec[4]/sec[1]/p[1]