The mouth of the Amazon (the volume of flow is equal to the volume of flow of all rivers on Earth) is not the best place for a living coral reef. I, unfortunately, did not find underwater photographs of this reef. Turbid water prevents the symbiosis of algae and the polyp. I would not be surprised if the corals on this reef have no color (zooxinella does not survive in the dark. In addition, heavy sedimentation should occur in the reef area and the corals should be covered with silt. They claim that its area is 9300 square kilometers, and the length is 970 kilometers (1/3 of the length of the Great Barrier Reef in Australia). Maybe they are joking with us? I don't believe. This should not be. If you have a photo or video, show it.

It's no joke, the mesophotic coral reef system was discovered about 40 years ago, but only relatively recently did it attract the attention it deserves.

https://www.science.org/doi/10.1126/sciadv.1501252?cookieSet=1

https://www.nature.com/articles/s41598-019-50245-6

Borys, there are a number of delta-front coral reefs systems in Indonesia, even few km from the delta of Mahakam River in East Kalimantan.

Article First record of coral reefs in the delta front of mahakam de...

Many coral reefs are able to thrive in relatively turbid waters because of other favourable conditions. If you are interested in this subject have a look at pages 447-483 in the following link where you can download the chapter.

Data Tomascik, T., A. J. Mah, A. Nontji & M. K. Moosa (1997). Cha...

Cheers,

Tom

my guess would be wave action and to a lesser extent tidal currents - wind and high energy shallow waters directing wave energy and distributes it across a long axis

Dear Tomas Tomascik.

This is very unusual and for this reason very important for understanding the reasons for the growth of coral reefs. This goes against everything I know about corals (tropical rivers are not only cloudy, but usually more acidic than ocean waters). After your information, I am at a loss, but it makes it possible to obtain a correct understanding of the process.

Thank you very much, Borуs.

Dear Iain McKechnie,

I have attached the bottom topography map (https://webapp.navionics.com/#boating@3&key=_erHhuarF). According to the map, there is a depth of more than 100 m and the waves do not reach the bottom.

Sincerely, Borуs.

Dear Tomas Tomascik,

I have read your articles with great interest. Learned a lot.

But I can also share useful information with you. I organized several dozen expeditions to the coral reefs of the Red Sea. The purpose of our research is to study the upwellings that you also observe. We managed to understand what kind of cold waters are fixed on a coral reef. This is the release of groundwater from the seabed. It is they who provide the reef with missing nutrients (nitrogen and phosphorus). Please find some free time and watch our presentations (we have been working on this for 20 years).

Presentations:

monograph coral reef 2021.pptx

New paradigm accumulative reliefin shallow water areas oceans and seas. Volume 2 (About coral reef);

Connection of coral reefs with zones of increased permeability of the earth's crust;

Binary effects of groundwater on coral reefs.

Sincerely, Borуs.

Thank you Borys, much appreciated. The old view that coral reefs have evolved in clear tropical oligotrophic oceanic waters has been shown not to be the case. If you are interested have a look at the papers published by Dr. Wilson and her colleagues (see the two links below).

https://d1wqtxts1xzle7.cloudfront.net/39358638/Equatorial_carbonates_an_earth_systems_approach20151022-1476-15lsia8-libre.pdf?1445529531=&response-content-disposition=inline%3B+filename%3DEquatorial_carbonates_an_earth_systems_a.pdf&Expires=1663265115&Signature=hOAUTG727HZ0Jc7ykBC9x31CH3G5glQsBEKf01-7LYef57lr2jlhTqBkrNa5~-NHoTDbPeW2GDuutIpdBKk8dzBIhFeXP9FZ3EoMgwdo3gnX-6NmU2DflNrCcxWiYNx4fQng9Wjd2tTqpYJ7Z2Mc9-tnTcHW8~mDqD-0M74-52HSjzZEzTkvuHRw6u769HQjdOp1q-NWjEjcLRxH97-sp6MUu7SySU-D5gHdhI4cTpAtRScsNxaLvvVayiI1DQVLBpmTqJPn4tqoIuORgJfSDz7BOSvDqImabqGgMGQiNvHv9erN0qoyLd-Nl9uHepYkTh9kFzQjw9DBh71q-~66HA__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA

http://searg.rhul.ac.uk/pubs/wilson_2005%20borneo%20patch%20reefs.pdf

Cheers,

Tom

I believe that most researchers in Brazil associate the linear shape of the reefs in the country with changes in relative sea level (roughly similar to the processes responsible for the circular shapes of atolls).

In particular, there are extensive lines of beachrocks occurring at different depths along the continental margin of the SW Atlantic. As beachrock form from "in situ" cementation of beach sand, beachrocks at greater depths are usually considered to be remnants of ancient coastlines. Thus, they are typically elongated rocks, running parallel to the coast. Many reefs in Brazil (but not all!) may have developed on top of these beachrock lines. There is a preprint suggesting that this is also the case of the Amazon reefs, thus explaining their linear shape.

https://www.researchgate.net/publication/363870723_Beachrocks_of_the_last_low_sea_level_substrate_of_the_barrier_reef_system_along_the_outer_Guiana_shelf

Dear Pedro Carneiro.

In science, including in the field of coral reef formation, the worldview is formed on the basis of the analysis of available information. If new information appears that contradicts the previously formed worldview, then the paradigm changes. It's unavoidable.

It is generally accepted that for the formation of a coral reef, clear water is necessary (photosynthesis of zooxinela is impossible in muddy water) and warm water (in cold water, a polyp cannot form an external carbonate skeleton). In addition, it is desirable to have a solid substrate for fixing the polyp at the bottom and sea currents that bring food to the polyp are desirable.

In tropical seas, these conditions are everywhere, but coral reefs are not formed everywhere. The reason is that the tropical zone of the ocean is oligotrophic. For the first time, we have included in the list of necessary conditions a fluid dynamic process in tectonic faults of the earth's crust. You can see the link: https://magazine.neftegaz.ru/articles/geologorazvedka/443409-flyuidodinamicheskie-anomalii-kaspiyskogo-morya/.

This led to the need to formulate a new paradigm for the formation of coral reefs. We did this in the second volume (Spatial patterns of coral reef formation) of the monograph "A new paradigm of accumulative relief formation in shallow areas of oceans and seas" (2021).

It was shown for the first time that in the oligotrophic tropical zone of the ocean, solutions of phosphates and nitrates enter the bottom layer only along tectonic faults. Without these substances, phytoplankton cannot form. Without phytoplankton, zooplankton (polyp food) cannot arise. We used the theory of structure formation of the solid shell of the Earth.

Block sizes change discretely (… 35x35 km, 70x70 km, 140x140 km, 280x280 km, 560x560 km, 1120x1120 km …). The orientation of the block structure is discrete (0° and 270°; 17° and 287°; 35° and 305°; 45° and 315°; 62° and 332°; 77° and 347°).

Solutions of nitrogen and phosphorus enter the oligotrophic waters of the ocean only along straight faults. Linear fault directions can only have six azimuths. Coral reefs only form along faults. Let's apply a new coral reef formation paradigm to a coral reef in the Amazon Delta. I have attached a diagram of this reef and a satellite image of the Amazon Delta with our additions. (Scheme of a coral reef from an open Internet resource).

The grid of tectonic blocks is like a chessboard. The white squares are up and the adjacent black squares are down. On the satellite image, I put a yellow line (approximate position of the coral reef). To this line, I leaned a square with dimensions of 1120x1120 km with an azimuth of 35° and 305°. The line of the coral reef and the northeastern boundary of the tectonic block coincided.

The correctness of drawing a tectonic block on a satellite image has several practical confirmations. The arrow in the image shows a tectonic fault, which manifested itself in the configuration of the ocean coast. The bay has an azimuth of 35 degrees. In the north-west direction, at a distance of about 560 km, you can see a similar bay (tectonic fault). This is natural, since the tectonic block 1120x1120 km is divided into 4 blocks. The adjacent block is shown in red. It is shown in the terrain as an uplift. I think it's convincing.

If there are doubts about the theory of fluid dynamics, I will provide additional evidence. In the picture, I showed in blue a tectonic block, which has dimensions of 560x560 km. It has a different spatial orientation (77° and 347°). Along the northern and western borders of the block, you can see straight riverbeds. This can be explained only by the theory of fluid dynamics of the lithosphere. All riverbeds coincide with tectonic faults. Thank you for watching.

Sincerely, Boris.

Dear Tomas,

I give my geologist point of view: many reefs have linear shape because they grew on top of past coastal areas (such as deltas) for example during the last deglaciation, when sea level rose from -120m to present level. There are many examples around the world (Belize barrier reef, Great Barrier Reef, including reefs offshore the Amazone river), some of them having been drowned during this very rapid sea-level rise (around 40mm/year). They grew on top of ancient deltas because these areas offered stable substrates and high-energy settings when they started to be flooded.

This is why some reefs have shapes looking as linear coastal/siliciclastic systems (some of them being still preserved: past fluvial channels being modern tidal inlet in lagoons). In other words they mimic the underlying morphologies!

Hope this will help.

Dear Stephan J. Jorry. I perfectly understood your idea. I think you get my point too. The coral reef is alive. Living requires a clear list of conditions daily. There are conditions that are necessary but not sufficient for a living coral reef to exist.

The presence of a solid substrate is necessary, but not sufficient, for a coral reef to exist at a depth of 50-100 m. The necessary factors for a reef in the Amazon Delta are: 1. no powerful sedimentation; 2. availability of food for the polyp; 3. the presence of light for zooxinella. Agree, if the reef is covered with sediments of the Amazon River, if there is no light for zooxinella, if there is no zooplankton for the polyp, the reef will not be alive. These conditions must be provided daily. Sincerely, Boris.

Dear all.

I don't know if my answer will help, but I attached some picture from my last research in Pannikiang island (Google Maps), located 1,79 km from sulawesi, and had a turbid water. There are 3 rivers near it. picture taken from east side of Island (5 meters depth). in the pictures we can see there are mostly dead corals, but there are some species that starting to grow. So, I guess the reef from amazon will looks like this. with, assumption there was already reef in this area before the turbidity in this area increases.

Thank you.

Dear Ayub Wirabuana Putra. In the discussion, this question was answered by Tomas Tomascik. In his articles it is written about upwelling. The upwelling water reached the sea surface. In such places, the water from the bottom to the surface is more transparent and cold, even in the region of the river delta. In this I found confirmation of my observations in the Red Sea.

In your photos you can see that the living coral has grown in the place where the water is clear. Algae grows in this place. In the place where the coral is found, there is no sedimentation to the bottom of solid particles that the river carries out. I can conclude that your photo was taken in the place where groundwater is released. Thanks for the important information. Sincerely, Boris.

Dear Natalya Kucherenko, I think that at the mouth of the Amazon, where there is hypoxia in the near-bottom layer (powerful oxidation of organic matter), favorable conditions for the life of a coral reef are formed only in the zone of groundwater discharge. In the groundwater discharge zone, organic matter cannot fall to the bottom. Look at the photo (1Suesswasserquellen-im-Meer-Lombok) submarine groundwater source (https://www.leibniz-zmt.de/en/research/scientific-departments/biogeochemistry-geology/wg-submarine-groundwater-discharge.html). Look at two photos of groundwater discharge along a tectonic fault along the reef "Thermal Imaging Camera Use: Groundwater Inputs to a Reef". https://www.dreamstime.com/stock-photo-outlet-fresh-water-spring-shallow-waters-caribbean-cost-mexico-image41963746. The first photo (2HGB_samoa-hilltop) is the location of the reef, the second photo (3HGB_samoa-hilltop-data) is an infrared image of groundwater (red). "Image of an area where groundwater discharges into a lagoon". «Thermal image indicates water temperature, where warmer temperatures are represented as red and cooler temperatures as blue. The image presents an area where warmer groundwater (red) may be discharging into a lagoon. Temperature is in degrees Celsius.»

The underground flow of the Amazon River is exceptionally large. Unlike surface turbid runoff, underflow runoff is transparent. According to https://www.scielo.br/j/jbchs/a/dxsv9VxQHnXgNqX4CBq8G7M/?lang=en "Recently, SGD was addressed at the Todos os Santos Bay, in the mid coast of Bahia State.37 Using short-lived radium isotopes, an advective rate of 142 cm day-1 was estimated. Considering the entire bay, it was found a total groundwater flux up to 300 m3 s-1, which represents three times the average river discharge into the bay."

For this reason, there may be "windows of transparency" in murky water over the reef at the mouth of the Amazon. But the source of groundwater must be so powerful that it must rise above the bottom to a height of more than 50 m. We carried out mathematical modeling of this process. See Figure (4). These are the results of our modeling of the rise to the sea surface of a less dense source of groundwater, over which we conducted instrumental measurements (described in the monograph "Interaction in the lithosphere-hydrosphere system").

Look at the photo of groundwater outlet to the sea surface (5_2017_07_07_Suesswasserquellen-im-Meer_01-550x413). Fresh water source in the sea off Lombok. The fresh water in the "water eye" has lower density than the sea water (c) Till Oehler, Leibniz Center for Tropical Marine Research (ZMT). https://blog.mares.com/freshwater-sources-in-the-sea-5267.html.

I assume that along the reef at the mouth of the Amazon, above the coral buildings on the bottom, there should be "windows" of transparent waters above the groundwater outlets at the bottom. In this area, the surface layer of turbid river waters has a thickness of about 10 m. I assume that the fact of "windows" of transparency over the reef can be confirmed by satellite images of the ocean surface by joint processing of the infrared (temperature) and green (turbidity) spectral bands. Sincerely, Boris.