New findings indicate that invisible deep reefs are unique protected areas. A team of highly-qualified scientific divers led by researchers from the California Academy of Sciences examined Pacific and Western Atlantic reefs to test a widely-held hypothesis that climate-sensitive life can escape from shallow reefs to mesophotic depths (1
"We have hope for coral reefs around the world," says Dr. Luiz Rocha, Academy Ichthyology Curator and Hope for Reefs Initiative Co-conductor. "Instead of giving up this hope, these insights show us how important it is to protect zones at dusk in places we normally do not look at, and we can not ignore the depth as we gain our collective power behind protection and restoration Reefs – in the light and in the dark – need our urgent attention. "
Almost 75 percent of the world's coral reefs are currently threatened by the combined effects of overfishing, habitat destruction, water pollution and climate change. Although coral reefs provide human societies with essential goods and services worth an estimated several hundred billion dollars a year, the deeper equivalent of the shallow reefs – the species they harbor, the threats they face, or the sanctuary
Charting Life in the Depth
Rocha is part of a deep-dive research team exploring these mesophotic reefs, the mysterious coral habitats that stretch across a narrow ocean ribbon of 100 -500 feet extend under the surface. In these deep reefs animals live in partial darkness – beyond the limits of scuba diving, but over the deep trenches patrolled by submarines and ROVs. As part of the Hope for Reefs initiative, the Academy team is exploring this unknown border with the help of high-tech devices such as circulatory reactors, which allow scientists to expand their research time underwater. Many species observed in the Twilight Zone are new scientific discoveries – but to determine if and how deep and shallow reefs are interconnected, reefs around the world had to be investigated.
"Twilight research is a scientific adventure that we take very seriously," says Bart Shepherd, Senior Director of the Steinhart Aquarium of the Academy and Hope for Reefs co-conductor. "One reason we know so little about them is that it is difficult to safely end the dives, from the Philippines to the Bahamas we have the life we experienced during these long, amazing and difficult dives, Carefully researched into action-packed reefs is not the sanctuary that some thought they were. "
The researchers performed visual counts of reef species by intersecting transects (an easy-to-follow path from a 20-meter tape measure ) Species appear at different depths. By comparing data from the field with the results of peer review literature, the team presents evidence that contradicts the two main assumptions of the "refuge hypothesis": First, that there are significant overlaps between deep and shallow reefs. and two, that deep reefs are protected from local and global threats (they are not).
Twilight Zone Reefs "Feel It All"
The study results published today describe the unique communities of endemic species found in deep reefs. Species that share shallow and deep coral reefs usually have strong preferences for certain depth zones. This means that only a few inhabitants of flat reefs move between light-flooded reefs and shady twilight zones. Even the largest predators – major players in the marine ecosystem such as sharks, groupers and snappers – that move between shallow and deep reefs every day, eat most of their food in the light and are unlikely to seek shelter in the depths. Flat and deep reef populations seem to be separated.
Mesopotentian coral reefs are in fact vulnerable to human and natural influences (such as hurricanes and tropical storms). In 2016, several members of the research team tracked the devastating path of Hurricane Matthew through the Bahamas and captured a rare glimpse of the effects of powerful storms on mesophilic depths. The team observed that strong storms can affect even the deepest coral reef ecosystems, stifle living coral and damage marine life with sand, mud and natural debris such as branches. Waste – including plastic bags, cups, aluminum cans and fishing gear – also seems to reach deep reefs.
"Deep reefs feel everything," Rocha says, pointing to the evidence of mesophilic vulnerability they have documented in two oceans. "In addition to the storm events, we have seen the well-known signs of strong fishing, sedimentation, coral bleaching and invasive species in deep reefs." "If true refuges exist for shallow reefs, we think they are far away from humans, but we really see the consequences of population growth and the increasing demand for food and natural resources underwater.The reef's problems do not stop at 100 feet. "
A Light in the Dark
The Academy's commitment to study and restoration The global coral reef will continue in the coming years with several visionary partners. This August, researchers from the Twilight Zone are exploring deep Pacific rifts in the Marshall Islands
Hope for Reefs – the Academy's initiative behind this study – supports expeditions to Earth's most remote and unknown reefs and understanding. Visitors to San Francisco's Golden Gate Park Academy can learn more about these precious ecosystems in Twilight Zone: Deep Reefs Revealed a first exhibit that shows the mysterious underwater world that few witness. Visitors can also experience the museum's latest original planetarium show Expedition Reef – immersive visualizations of deep reefs and shallow reef restoration work with SECORE International under a world-class planetarium dome.
"At a time of global coral reef crisis and knowledge of unexplored reef habitats are critical to our understanding of how we can protect them," says Rocha. "Deep reefs are important environments that rarely occur in marine protected areas or protected areas, we want to highlight the unexplored wonders of the ocean and inspire a new generation of sustainability masters."
Deep reefs are unlikely to save shallow coral reefs
L.A. Rocha et al., "Mesopototic coral ecosystems are threatened and ecologically different from shallow reefs" Science (2018). science.sciencemag.org/cgi/doi … 1126 / science.aaq1614