Coral reefs around the world face destruction due to ocean acidification, pollution, overfishing, and other factors. These stressors affect reef health on short timescales, but scientists have struggled to capture the details of these rapid changes. Takeshita et al. have now developed and successfully tested a new tool that could improve real-time reef monitoring worldwide.
The Benthic Ecosystem and Acidification Measurements System (BEAMS) is the first tool that can make autonomous, simultaneous measurements of two important reef health indicators: net community production (NCP) and net community calcification (NCC). NCP is the balance between organic production and respiration, and NCC is the balance between calcification (reef building) and dissolution (reef erosion).
Measuring NCC and NCP is important because their ratio reflects reef community structure and health. For example, coral-dominated reefs have higher NCC to NCP ratios than reefs dominated by other organisms, such as algae. NCC and NCP also reflect the effects of stressors. Since the Industrial Revolution, ocean acidification alone has decreased reef NCC by 12% worldwide.
When deployed directly in a reef, BEAMS detects NCC and NCP at 10-minute intervals. A pump retrieves water from different near-seafloor depths and pushes it past a sensor, which measures pH and oxygen levels. BEAMS then uses these measurements to calculate NCC and NCP.
In September 2014, the team put BEAMS to the test. The researchers wanted to see whether it could accurately distinguish between two reef ecosystems with very different community structures. The two sites were located less than 1 kilometer apart in the Palmyra Atoll, a protected area in the central Pacific that is home to some of the healthiest reefs in the United States.
In 2 weeks, BEAMS captured more than 1000 NCC and NCP measurements at each site. The NCC to NCP ratio was higher at the site dominated by corals and lower at the site dominated by noncoral organisms called corallimorphs. Following these successful results, the authors say, researchers could use BEAMS to monitor reef health worldwide and shed new light on the details of reef metabolism. (Journal of Geophysical Research: Oceans, https://doi.org/10.1002/2016JC011886, 2016)
—Sarah Stanley, Freelance Writer