UPDATE July 1, 2023: In the Vauxhall Reef area this past winter I observed healthy Padina, but not on the reef flat where it had once been abundant, rather it was on rocks near shore in the beach area.
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Going through my recent and older photographs of the reef flat on Vauxhall Reef, I realized that Padina sanctae-crucis was absent in my recent 2019 photos, but was present in photos taken in each of the winters of 2015,2016, 2017 and 2018. So
I checked the area out over the last couple of days, and also traversed nearby fringing reefs over about 800 m towards the north.
Nada.
I don’t know what that means, but on Jan 30, 2019 asked on the CORALL Facebook page whether anyone else has noticed the plant recently.
It’s not necessarily bad, for example, the loss of P. sanctae-crucis might be due to increased feeding by nearshore herbiverous fishes.