New photographic technology has allowed scientists to dive beneath the ocean’s surface and peer into the hidden world of baby corals to learn how these tiny organisms survive and develop throughout the crucial first 12 months of life.
In a research just publishedresearchers from Southern Cross University and CSIRO describe how advanced imaging techniques offer recent ways to observe young corals.
Corals provide a very important habitat for a big selection of marine organisms. It is subsequently necessary to higher understand how young corals select and connect to reefs, settle and grow into adult corals.
This knowledge is very necessary if we would like to assist reefs recuperate from devastating events reminiscent of mass bleaching events and cyclones.
The secret lifetime of corals
The lifetime of a coral begins during annual synchronized spawning. Coral colonies release hundreds of thousands of tiny eggs and sperm into the water at the identical time. They all float to the surface, where the eggs are fertilized, which then turn into embryos after which larvae.
Over the course of days or perhaps weeks, hundreds of thousands of larvae spread on ocean currents. If all goes in accordance with nature’s plan, the larvae eventually fall into the water, attach themselves to the reef, and grow into adult corals. This process is known as coral “recruitment.”
In healthy coral reefs, recruitment occurs naturally. However, as coral reefs grow to be increasingly degraded – for instance through coral bleaching brought on by climate change – fewer coral larvae are produced. This often means recruitment slows or stops and natural regeneration is weakened.
Scientists are working on ways to be sure that coral larvae attach to and grow on reefs. This includes collecting coral eggs from the ocean, raising embryos in floating nurseries and releasing larvae on damaged reefs.
Coral larvae are lower than one millimeter in size, so recruitment occurs on a small scale, invisible to the human eye. To higher understand this process, researchers traditionally attach artificial plates to the reef. Once the corals have settled in, the plates are taken back to the lab to be examined under a microscope.
This method can provide priceless information, but doesn’t replicate the natural environment of the reef. This is where our research is available in. We mainly moved the lab to the reef.
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Capturing the reef in incredible 3D detail
Our recent study explores the event and application of an modern imaging approach often called underwater “macrophotogrammetry.”
Technology connects macro photography – photographing small objects up close, in very high resolution – and photogrammetry – taking measurements from photos. In this case, we used photogrammetry to “stitch” the photos together to recreate three-dimensional models just like the one below.
The three circular objects within the model are “targets” that we placed to assist the software put the photos together. Look closely and you will see a nailhead on the left side of every goal. To offer you an idea of the dimensions of the model, the nail head has a diameter of two.8 mm.
Reef scale photogrammetry could be: priceless tool to trace changes in coral cover and growth over time. However, it doesn’t provide the detailed resolution needed to discover and observe recent, tiny corals.
Macro photography provides this incredibly detailed scale. Technology coupling also enables a comprehensive understanding of all the ecosystem, from the smallest to the biggest processes.
We conducted macrophotogrammetric research near Lizard Island on the Great Barrier Reef. We marked several locations on the reef measuring 25cm x 25cm. We then took lots of of photos from different angles using high-resolution cameras.
Photogrammetric software was used to process the photos, creating precise 3D models showing small fragments of the reef in very high resolution.
The models were examined to find out where young corals settle, mark their location and measure their size. They reveal the complexity of the reef’s microstructure, including the tiny crevices where coral larvae live they often calm down.
The models also reveal quite a lot of microorganisms, reminiscent of small turf algae and invertebrates, that interact with corals throughout the recruitment process.
Macro surveys could be conducted at the identical reef locations over time. Thanks to this, we will monitor the survival and growth of young corals and observe changes in organisms living near them.
Lauren Hardiman CSIRO
Looking to the long run
Complementary techniques can further enhance the potential of macrophotogrammetry. These could also be, for instance, coral larvae dyed in numerous colours before being released, making them more visible as they reach and decide on the reef. This could be captured in 3D models to enable even higher tracking of larval recovery efforts.
The use of macro photography will deepen our understanding of why some larvae settle and survive on reefs and others don’t. This knowledge might help support our efforts to enhance the general protection and restoration of coral reefs.
Its use doesn’t need to be limited to coral reef ecosystems. We are excited concerning the potential of this technology to expand marine research more broadly.
