Measuring Outdated Corals & Coral Reefs (Half 1)

Measuring Old Corals & Coral Reefs (Part 1)

Reposting from Jennifer Marohasy's blog

November 27, 2020 by Jennifer

Measurement is fundamental to science. It is a way of objectively assessing something, anything, even the condition of a coral reef, even a single coral. Historically, coral growth rates were measured by coring the really old massive porites.

Like tree rings in temperate forests, the massive old pores can be gutted to identify the banding, and from this coral calcification rates can be calculated, which are a measure of the growth rate of individual corals.

Peter Ridd has requested quality assurance for so many measurements related to the health of the Great Barrier Reef, including coral growth rates. Important Australian institutions have responded with stone walls and in the case of James Cook University actually fired him. After two rounds in federal courts, his appeal against his dismissal eventually goes to the High Court of Australia, with the next hearing likely in February 2021. While attorneys are preoccupied with Peter's rights or otherwise with academic freedom and freedom of speech, I worry whether Peter is actually telling the truth when he says the Great Barrier Reef is resilient and definitely won't die of coral bleaching, despite the fact that there is an issue with the integrity of science.

Most media reports, based on extensive aerial photographs by his former colleague Terry Hughes, conclude that the reef has died 50% or 60% of coral bleaching as a direct result of global warming.

These media reports do not take into account coral growth rates, but rather the area of ​​coral that Professor Hughes measured as bleached, with the conclusion that this will all die.

Terry Hughes and Peter Ridd can't both be right.

How could they have come to such different conclusions about the health of the Great Barrier Reef? Is the reef really half dead or not?

Jen / me the other side of a red sea fan coral, two days ago at Pixie Reef.

My working hypothesis is that Terry Hughes' claim that the reef is half dead is not objective because there is a flaw in his particular survey method. This method is well described in the literature, particularly in his 2018 article in Ecology entitled "Large-Scale Coral Bleaching on the Great Barrier Reef".

Science is not a truth. It is a way of getting to the truth by one method or another that is often measured. Sometimes scientists get the method wrong and find answers that are also wrong. Sometimes people like the wrong answer because it is politically correct.

Could it be that while surveying Professor Hughes inadvertently looked out the window of an airplane at such a great altitude (150 meters) and then only tilled the ground on a particular type of reef habitat known as a "reef crescent" incorrectly Answer recorded? Could he avoid it, even in denial, when it comes to all the coral in the reef lagoon?

Marine researchers and anyone who has experience diving coral reefs know that coral reefs have different ecological zones. The reef crest, as the name suggests, is the highest part with corals in this habitat, which are often exposed at low tide and sometimes rain. In storms and cyclones, this is the part of the reef that is most likely to be smashed by large waves. It is not surprising that in this coral reef habitat / area, there may be no living corals or that the corals may be more stunted and sparse. On the same reef, there can be healthy corals in the lagoon and in the back reef on the leeward side of the ridge, and corals growing down the front slope, even around the perimeter of the ridge if it's a flat-topped platform . If the scientist / Terry Hughes just surveyed the crest, he could give the impression that the reef is dead when it is actually full of life – just not at the reef crest.

Pixie reef from about 100 meters high (thanks to my Skido drone). In the foreground (with our boat) is the so-called reef lagoon. Then there is the reef crest which is mostly beige. Behind the ridge is the front of the reef, which drops steeper and deeper. The types of coral vary so much with these three different habitat types.A picture at a lower height shows more clearly a demarcation between the reef lagoon and the reef crest on one reef, the Pixie Reef not far from the city of Cairns in the far north of Queensland.

Professor Hughes, in his 2018 article, explicitly states that underwater surveys were conducted to assess the accuracy of aerial photographs using five 10 x 1 meter belt transects on the reef crest. There is no evidence that it distinguished between the various reef habitats. He only overlooks the ridge of the reef. He examined the area where there were probably the "worst" and "least" corals.

I tested my hypothesis that Professor Hughes' methodology was flawed only two days ago (November 25th) at Pixie Reef. We took my Skido drone in the air and took photos at heights of 5, 10, 20, 40, 100 and 120 meters on the reef crest, the reef lagoon and the reef curtain. Photos follow just 5 and 120 meters from the ridge and lagoon at Pixie Reef. (If I can put together a large collection of these types of photographs from different reefs, they could form the basis of a notice for publication on the measurement and importance of measuring different habitat types on the same reef if the idea is to understand health of the entire reef ecosystem, not just the reef crest.)

A photo taken at 120 meters of the reef crest is very different from a photo of the reef lagoon that was taken at exactly the same height. At a height of 120 meters, parts of the reef ridge look rather barren, perhaps bleached. For the most part, Hughes has concluded that 60% of the Great Barrier Reef is bleached from 150 meters and looks out at the reef crest from an airplane window.

The reef crest on Pixie Reef with a view from 120 meters.The reef lagoon on Pixie Reef with a view from 120 meters. Photo taken on November 25th with Skido.

The rather large circular boulders in the lagoon photo from 120 meters high are massive porite corals. The type of coral that Peter Ridd AIMS wants as the core, so we had an objective measure of coral growth rates 100 years ago.

Jen / I put a tape measure to know that this porite is about 1.2 meters high and 1.8 meters wide. These are external measurements. I wonder how old is this coral? It would be possible to determine its age by pitting (an internal measure) and then counting the annual growth rings.This is a close-up of the same porites with their gold-colored tentacles. With the tentacles retracted, I wonder if the coral is more pale pink than golden.

The photo of the reef crest from a height of 120 meters was taken with the drone (Skido of course), which was raised vertically from 5 meters to 120 meters. This is what the same reef looked like just 5 meters above the ridge. There are live corals but no massive porites or even red sea fans, although both exist on the Pixie Reef, but would have been excluded from a 10 meter belt cut across the reef crest and from an aerial view of the ridge because they exist in a different habitat Art.

The ridge of the reef is only 5 meters high.

A photo taken 5 meters above a section of the reef lagoon shows plate corals that appear as toadic mushrooms when photographed underwater. This seems best because it is the pixie reef. However, I did not find any elves.

The reef lagoon at a height of only 5 meters. Of course, to really know the corals you have to go underwater.This is what a plate coral looks like underwater. Of course, it looks more like a toadstool on the pixie reef.

Thanks to Stuart Ireland for taking me to Pixie Reef and taking all the photos underwater, and he also flew skido. All photos (with the exception of the closure of the core) were taken on the Pixie Reef on November 25, 2020. The Pixie Reef is located northeast of Cairns in the far north of Queensland.

The picture at the top of this blog post shows me / Jen swimming over a 7 meter wide porite on Pixie Reef on November 25, 2020. This is the type and size of coral that Peter Ridd would like to consider still to be gutted by the Australian Institute for Marine Science (AIMS) as an objective measure of coral growth rates. AIMS used to core these ancient corals to get an idea of ​​climate change hundreds of years ago. This coral could be more than 400 years old, with annual bands that can be measured on the scale of one year, year after year, maybe 300 or 400 years back to calculate an annual growth rate. With the help of one coral we could see (if they gutted it) whether the growth rates have increased or decreased from year to year or not. ShareTweetShare

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