Diver’s drop over the gunnel.
Tanks, weights, divers, and a mesh bag full of tools all descend in emerald waters beneath grey skies. Off the vessel’s bow, a yellow beacon blinks with a red flashing light and a thin data cable stretching to the seafloor, all connected to a suite of sensors twenty feet below – a new real-time monitoring system for tracking one of the greatest threats to coral reefs: Ocean Acidification.
A new series of ocean instruments is monitoring vital reefs within the Florida Keys National Marine Sanctuary (FKNMS). Scientists at NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) and the Cooperative Institute for Marine and Atmospheric Sciences (CIMAS) have deployed Sofar “Spotter” buoys at four of the seven Mission: Iconic Reef sites identified as essential for restoration.
The Sofar buoy at the surface measures wave energy, wind speed, sea surface temperature, and pressure. Below the surface, integrated sensors measure pH and seafloor temperature in near-real time – actively monitoring ocean acidification on crucial reefs.
Global ocean acidification is impacting the integrity and hard, calcium carbonate structure that comprises entire coral reefs. The decrease in pH across marine ecosystems due to the ocean’s increasing uptake of atmospheric carbon dioxide accelerates the erosion of reefs and decreases their ability to grow (i.e. calcify). Together, these threats contribute to loss of crucial habitat that provide shelter to the highest concentration of marine biodiversity.
The global impacts of ocean acidification are well-known. But a decade-long study led by scientists at AOML revealed that there are spatial gradients in how acidification progresses across the Florida Keys, and some sites in the Upper Keys may act as refugia able to mitigate a decrease in pH – potentially due to the higher abundance of seagrass beds and other benthic communities.
The seven Mission: Iconic Reefs (M:IR) within the Florida Keys National Marine Sanctuary (FKNMS)
The Florida Keys National Marine Sanctuary consists of 350 miles of the only North American barrier reef – the Florida Coral Reef – stretching from the Dry Tortugas to Port St. Lucie. An estimated 5 million visitors travel to the Florida Keys every year where 54% of jobs are tied directly to the marine ecosystems – along with billions in economic contributions to the state of Florida from tourism alone.
The NOAA-led, partner driven project Mission: Iconic Reefs was launched in 2019 to restore seven strategically-selected reefs covering three million square feet – or 52 football fields – within the Florida Keys to self-sustaining levels over 20 years. However, as ocean acidification and other environmental stressors threaten this crucial ecosystem, the need to monitor changing ocean conditions becomes more essential.
“We needed a new, cost-effective way to accurately monitor ocean acidification in real time,” explains Ian Enochs, Ph.D., Principal Investigator of AOML’s Coral Program.
Dive team deploying the integrated instrument system at Horseshoe Reef. Located in Key Largo Florida.
Collecting and transmitting data below the surface has always been a challenge. Current methodologies are often limited by labor-intensive deployments, requiring heavy machinery, highly trained personnel, and larger vessels, resulting in costly and time-consuming field operations. Additionally, many existing systems rely on satellite-based data transmission, which, due to cost constraints, often sends data at longer intervals to minimize expenses. This delay in transmission impacts data availability and resolution, limiting the ability to monitor rapid environmental changes in real time.
Investigating conditions on coral reefs below the surface usually depended on field operations, deployable instrumentation and seawater sampling complicated by weather conditions, costs, and potential data loss due to unmonitored instrumentation. Satellites provide high-resolution observations of ocean conditions in near-real time – but they can’t see below the surface or provide information on the environmental conditions the reefs are experiencing, specifically key environmental factors affecting reef growth, such as pH.
With these Sofar buoys and a newly-developed online application, scientists with AOML’s Coral Program are now actively seeing how conditions fluctuate and monitoring instrument functionality in real-time at four of the seven Mission: Iconic Reefs: Carysfort, Horseshoe, Cheeca Rocks and Sombrero Reefs.
“With this new system,” explains Enochs, “we can detect issues when they happen, so we can ensure instrument performance and respond accordingly.”
However, the true advantage that set the Sofar “Spotter” buoy for the team came with their ability to customly integrate an advanced sensor monitoring changes in pH across these reefs.
While probes and pH electrodes are often strapped to buoys and other deployable instrumentation in the marine environment, these sensors may not be of sufficient quality to monitor the gradual progression of ocean acidification. Over time they degrade, leading to drifting data that can compromise a monitoring program. Scientists with AOML’s Coral Program have instead taken a different approach.
The Sofar Spotter buoy floats at the surface monitoring ocean conditions with a protected data cable running to the seabed. The bristlemouth development kit (center) receives pH and temperature data from the SAMI-pH sensor (bottom left).
Integrating a Sami-pH logger at the base of each buoy, the team uses a colorometric system where seawater enters the device – comprised of micro pumps, injector valves and reactor cells – and undergoes a chemical reaction when exposed to reagents.
This reaction changes the water’s color. A change that the Sami-pH measures and quantifies as a pH reading, it is sent via the cable to the buoy and over satellite or cellular to the Coral Program’s online application, providing a high-resolution pH measurement of a reef in near-real time.
With the Sami-pH’s ability to perform this process consistently for up to ~6 months without maintenance, the Coral Program can more accurately monitor whether coral reefs are exposed to more acidic (i.e. lower pH) waters.
“The durable and easily customizable design of these buoys allows for easy deployment in a variety of environments. It’s amazing not only being able to see what is happening on the reef in real-time, but also being able to make sure all instruments are working properly and providing a continuous dataset.” – Taylor Gill, AOML Coral Program’s Mission Iconic Reef Environmental Monitoring Coordinator
As hurricanes, tropical storms and severe weather brush the Florida Keys, scientists at AOML will also be able to see how these storms influence coral reefs as they hit – and whether they provide relief when water temperatures are peaking or exacerbate the impacts of other stressors.
Ultimately, deploying these novel integrated systems is the beginning of an easily – scalable solution to monitor marine environments and fill gaps in ocean acidification research by providing better data collection both spatially and temporally.
As part of the large-scale Mission: Iconic Reefs restoration effort comprised of various multiple groups implementing different stages of restoration, AOML’s Coral Program oversees the environmental monitoring initiative. However, understanding the environmental conditions at these reefs in real-time and managing instrument functionality will also help scientists at AOML build on crucial ongoing experiments that seek to enhance coral resiliency.
Explore the live Mission: Iconic Reefs Environmental Monitoring Application here: https://coral.aoml.noaa.gov/mir/