AOML researchers have taken an innovative approach to studying the changing carbonate chemistry of seawater at shallow coral reef sites. Using 3D printing technology made possible by the new Advanced Manufacturing and Design Lab at AOML, researchers have been able to create their own water sampler within the lab.

The new instrument, a Subsurface Automated Sampler, or SAS, minimizes some of the financial hurdles encountered in performing marine research by serving as a low-cost, open-source alternative to existing water samplers. Its simple design is also easily modified to accommodate evolving research needs.

The subsurface automated sampler  was designed and built by coral ecologists, Dr. Ian Enochs and Nathan Formel.  The instrument was envisioned to address two of the largest hurdles to marine research—time and cost. “The issues of time and cost are the biggest obstacles often faced in marine research,” said Enochs. “Our objective was to overcome these issues, making it easier to study carbonate chemistry on shallow reef habitats.”

Prior to the development of the subsurface automated sampler, most of the water samples collected on reef sites were done manually. While automated water samplers do exist, their design is proprietary, adding an inflated cost to their use. They are also typically unwieldy in size, limited to single samples, and not always functionally applicable to shallow-water environments.

The sampler makes field work more efficient by enabling researchers to study coral reef carbonate chemistry at finer spatial and temporal scales. It can be programmed to collect water samples and temperature measurements at predetermined dates and times. Additionally, its compact size allows researchers to deploy multiple instruments and collect them at a later date for in-lab analysis of the water chemistry at different points across a reef site or at different times within an area.

The ocean’s long-term uptake of carbon dioxide has gradually made seawater more acidic. This phenomenon, widely known as ocean acidification, detrimentally affects coral reef ecosystems. While open ocean carbonate chemistry shows a clear trend in decreasing seawater pH, shallow-water systems are inherently more dynamic. Fluctuations in water chemistry occur over time scales ranging from daily to seasonal. To accurately characterize their variability and to monitor ocean acidification trends, high-frequency sampling is needed.

Work began in 2015 to develop the first sampler prototype capable of deployment at reef sites to depths of 15 meters (49 ft) and programmed in advance to collect two 500-ml samples at pre-set times. “We wanted to create something to maximize our effectiveness in collecting ocean acidification data on coral reefs,” said Enochs. “To do this, we needed a waterproof device to reliably collect water samples at least as effectively as the current common practice while also strong enough to endure the often rough water conditions found in shallow nearshore reef habitats. Because conditions are dynamic, we also needed the instrument to be adaptable and field programmable. We built a small, power efficient screen and infrared receiver into the unit that can be programmed using a handheld remote control, even under water.”

Drawing on their collective wealth of marine research experience, AOML scientists have since then tested and refined this first prototype, leading to the production of what is now the subsurface automated sampler. As a result, researchers are poised to better determine how changes in dissolved inorganic carbon, total alkalinity, and ocean acidity have occurred over time and space at coral reef sites, furthering their understanding of these fragile ecosystems.

While AOML scientists are using 3D printing technology to achieve their research goals, they are also committed to ensuring the science is accessible and remains open source. Detailed instructions for how to build the samplers and the circuitry that powers it are available online at www.coral.noaa.gov/accrete/sas. Construction and operating guides, along with sampler code, 3D printing design files, laser cutting files, and circuit board design files, are also available for download. Additionally, lesson plans developed in conjunction with Far­Outreach Solutions are available online to teach students about ocean acidification, as well question-based engineering and design.

The SAS is currently being used by NOAA’s National Coral Reef Monitoring Program https://www.coris.noaa.gov/monitoring/ and scientists at the Mote Marine Laboratory, the University of the Philippines, Texas A&M University, the University of Hawaii, the Escuela Superior Politécnica del Litoral (Ecuador), and the Universidad de Concepciόn (Chile), among others.