The Health of Hawaii's Twilight-Zone ReefsLatest update June 14, 2019 Started on March 1, 2019
Beginning in Fall 2019 we will begin research to monitor ecological processes on Hawaii's mesophotic "twilight-zone" coral reefs. By measuring mesophotic coral recruitment we'll discover how these unique reefs persist.
Doing science is always about flexibility and scientists everywhere sacrifice endlessly to ensure the quality of the data they collect. Working on particularly deep coral reefs means finding the right balance between minimizing risk and ensuring good data. Rebreathers are finicky and prone to failure, which is just about the last thing you want happening when you're down deep. So we plan, train, and spend enormous amounts of time scouting potential study locations to find the right location to do our science. Below is a video of one such dive on a truly unique fossil shoreline off of Kaneohe Bay, Oahu. While only at a depth of about 90 ft (27 m) this site features corals with morphology much like their mesophotic counterparts. The proximity of this site to our lab at the Hawaii Institute of Marine Biology, and safety of making relatively shallow dives to about 30 m makes it a strong contender for this project.
A critical part of any diving research is efficient, safe scouting - this is especially true for deep mesophotic reefs. It might be fun to get on a rebreather and make a deep dive to check on equipment, but it is always safer to send a camera down if you can. That's why we're applying to the OpenROV S.E.E initiative, which aims to donate OpenROV units to researchers in need.
Having a low-cost, efficient OpenROV system would drastically improve the safety and efficiency of scouting for mesophotic coral reefs in Hawaii. Currently every day of diving on these sites costs approximately $1,000 after equipment and fees. That is a high price to pay for researchers, but is required to keep our divers safe. However, the reality of rebreather diving is that even with the best training things can go wrong and the results are frequently tragic. Being able to rapidly scout locations with an OpenROV would greatly reduce the cost of scouting new mesophotic study locations, and most importantly, keep our divers safer by limiting the number of dives required to do this incredible science. In addition we'll also be using this ROV to deploy and retrieve equipment from the seafloor such as CoralCam or settlement tiles - and possibly add a few tools of our own to the ROV!
To succeed in our OpenROV proposal we'll need at least 25 followers, so please invite your friends to follow our expeditions if you haven't already!
CoralCam development is continuing and a build guide for the cameras has been submitted for publication - details to follow soon. These cameras are remarkably resilient to fouling and clean up nicely after deployment! Our hope is that monthly rotation of these cameras can provide a continuous daily record of coral growth and potential sources of mortality such as bleaching, disease, or predation. To keep up with CoralCam updates check out the Open Science Framework page which has all the resources needed to build your own! Link to OSF here: https://osf.io/tvq8n/
We've now developed a unique, low-cost camera for monitoring the experimental treatments used in this experiment and have submitted the design for publication. Named CoralCam, these cameras cost just $80 USD and can be deployed up to 45 m for one month at a time. That's about 1/10 the cost of commercial options! During their month-long deployment each camera captures twiced-daily photos or videos of the settlement tiles. Our hope is to use these cameras in conjunction with OpenROV to improve our ability to detect fine-scale ecological processes occurring along the shallow to mesophotic depth gradient. Preliminary tests in shallow water have demonstrated CoralCam's ability to detect daily variation in sediment stress and interactions between corals and other benthic invertebrates - we can't wait to see what we see at the mesophotic sites!
Using a combination of instrumentation and closed-circuit rebreathers (CCR), we'll be monitoring recruitment processes occuring on Hawaii's little-known mesophotic coral reefs. These reefs exist at 60m and deeper, beyond the range of traditional SCUBA diving and too shallow to study with expensive submarines. The unique community composition of mesophotic reefs, and their similarities to declining shallow reefs, have made their study a priority among reef stakeholders worldwide. We'll investigate the rate at which corals are settling into and growing in these dark environments, and compare this to data from shallow reefs to try and assess the magnitude of post-settlement selection across a complete shallow to mesophotic gradient.
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