I want this blog to be a record of all that is happening in our bays – the things that are worthy of celebration, and the things that are not so palatable and are hard to see.
Today’s post is one of the latter. Over the last six weeks, I have increasingly noticed a disease that is presenting differently to the white syndrome that we have sadly become used to seeing, and which I have described in this blog several times. With white syndrome, the coral tissue dies and the white skeleton of the dead coral remains, eventually getting overgrown by surface algae. With this disease, which I have seen before but not to this extent, the coral goes grey-ish black and sometimes looks like it is almost dissolving or melting away.
I sent some photos to Associate Professor Tracy Ainsworth, and her colleagues, Associate Professor Bill Leggat and postdoctoral fellow Charlotte Page, our coral health researchers contracted by Australian Marine Parks to monitor the reef’s health.
Old Gnarly’s hole on 27 March 2022
Old Gnarly’s hole on 20 January 2024. You can read more about him here: Old Gnarly, the swal doodle
This morning, Tracy got back to me, and it wasn’t pretty:
‘I would say this is the advanced stage of the Monitora[1] disease we have been seeing across the bays the last few years. This is a very similar disease progression to the Atramentous Necrosis first described on the reefs adjacent to Magnetic Island; the Monitipora disease over the past few years in Norfolk’s bays displays very similar progression patterns.’[2]
Tracy goes on to explain that in diseases where the skeleton is black like this, there is a microbial black matt growing inside the coral skeleton. This tends to expand inside the skeleton, below the tissue. Generally, black matts are a mix of a (sulphur oxidising) bacteria, fungi, and in some instances a black boring sponge that is also very dense with bacteria and sulphur oxidising bacteria. This creates a toxic environment that kills off the coral tissue, causing it to die and slough off.
Tracy says, ‘It’s possible the temperature and nutrient conditions are allowing these stages of colonisation/growth/necrosis to run very quickly.’
If you wish to know more about coral disease in Norfolk Island’s lagoons, I suggest some useful reading is Page et al.’s paper (link, below).
All the photographs in the gallery, below, were taken in January 2024 and are recent outcrops of the disease.
[1] Montipora is a genus of coral, consisting of at least 85 known species.
[2] Page, C, Leggat, W, Egan, S & Ainsworth, T 2023, A coral disease outbreak highlights vulnerability of remote high-latitude lagoons to global and local stressors, iScience, vol. 26, iss. 3, viewed 29 January 2024, https://doi.org/10.1016/j.isci.2023.106205