Scientists can now peer directly into the microscopic world of living coral reefs, thanks to a portable underwater microscope that reveals photosynthesis happening in real-time within individual coral cells.
The device, developed by researchers at UC San Diego’s Scripps Institution of Oceanography, allows marine biologists to study coral health and bleaching processes without disturbing these fragile ecosystems.
The Benthic Underwater Microscope imaging PAM (BUMP) represents a significant technological advance in coral research, offering unprecedented views of the symbiotic relationship between corals and the tiny algae that keep them alive.
Seeing the Invisible
Corals depend entirely on microscopic algae living inside their tissues—each just 10 micrometers across, or one-tenth the width of human hair. These algae perform photosynthesis, converting sunlight into energy-rich sugars that feed the coral. When corals lose these algae due to stress, they bleach white and eventually starve.
“This microscope is a huge technological leap in the field of coral health assessment,” explained Or Ben-Zvi, a postdoctoral researcher at Scripps Oceanography and lead author of the study. “We now have a tool that allows us to examine these microalgae within the coral tissue, non-invasively and in their natural environment.”
The microscope uses pulse amplitude modulated (PAM) light techniques to measure how efficiently individual algae photosynthesize within coral tissue—something previously impossible to observe underwater at such scales.
Technical Innovation
The BUMP builds upon earlier underwater microscope technology but adds crucial new capabilities:
- Nearly micron-level resolution for imaging individual algae cells
- Real-time photosynthesis measurement using fluorescence techniques
- 3D scanning capability through focal depth adjustments
- Portable design fitting in a carry-on suitcase
- 20-hour battery life for extended underwater research
Coral Behavior Surprises
Beyond measuring photosynthesis, the microscope revealed unexpected coral behaviors. Ben-Zvi observed corals constantly changing their volume and shape, with individual polyps rapidly contracting tentacles to capture or remove passing particles.
The research team tested the instrument at coral reef sites in Hawaii, the Red Sea, and Palmyra Atoll. In studies comparing shallow versus deep-water corals, they discovered that shallow corals showed lower photosynthetic efficiency and higher variability—likely due to more stressful light conditions.
One technical detail not emphasized in initial reports: the system uses specialized LED arrays with Fresnel lenses to focus illumination precisely, enabling short 50-microsecond exposures that minimize motion blur while reducing potential stress on the corals from bright lights.
Real-World Applications
“We get a lot of information about their health without the need to interrupt nature,” Ben-Zvi noted. “It’s similar to a nurse who takes your pulse and tells you how well you’re doing. We’re checking the coral’s pulse without giving them a shot or doing an intrusive procedure on them.”
The microscope’s non-invasive approach means researchers don’t need to collect samples or even touch the corals they’re studying. This preserves the natural ecosystem while gathering detailed health data.
Early results suggest the instrument can detect warning signs before corals experience irreversible damage from climate change events like marine heat waves. These insights could help guide conservation strategies to better protect vulnerable reef systems.
Beyond Coral Reefs
“Since photosynthesis in the ocean is important for life on earth, a host of other applications are imaginable with this tool, including right here off the coast of San Diego,” said Jules Jaffe, the research oceanographer who co-developed the microscope.
Several Scripps researchers are already using BUMP to study early life stages of giant kelp off California’s coast. The technology could potentially examine any small marine organisms that photosynthesize, opening new windows into ocean ecosystem health.
As coral reefs face mounting pressure from climate change, having tools that can diagnose problems at the cellular level—in the corals’ natural habitat—may prove crucial for conservation efforts worldwide.
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