Survey-date heat gave no clear next-year algae cover link in four Atlantic and Pacific coral survey samples in 2003-2018

We tested whether heat at a Reef Check survey was linked to next-year change in nutrient-indicator algae cover. We used 1,377 matched cells in separate Atlantic and Pacific samples in 2003-2009 and 2010-2018. All four adjusted country-cluster intervals included zero. Pacific slopes were +0.36 and +0.25 cover points per four TSA degree-heating weeks. Atlantic slopes were -3.65 and +0.67 points, with wide intervals. Only 45 matched cells had heat of at least four TSA degree-heating weeks. Usable next-year matches occurred in 12-21% of eligible baseline cells. Fixed-record bounds with missing cover from 0 to 100% allowed both heat slope signs in all four samples. The result does not establish no heat effect or no shift toward algae. Heat at the survey date can miss heat between visits. Missing records, few country clusters, unknown observers and selected sites limit inference. The package gives code, cell data, source hashes, checks and a figure.

coral reefs · algae cover · heat stress · observation bias · missing follow-up · regional replication