University marine science senior studies DNA of coral and algae

[USA] Coral reefs are an important ecosystem for marine plants, fish and other organisms. Despite making up less than one percent of the ocean environment, they shelter approximately 25 percent of marine species, protect shorelines and support the fishing industry.

Yet as water temperatures rise and pH levels fall in response to climate change, the future of coral reefs remains uncertain.

University of Delaware senior Danielle Dodge believes that analyzing the unique genetic fingerprints of algae living inside of corals could be integral to uncovering the future of coral reefs.

Dodge, an environmental science major in the College of Earth, Ocean, and Environment, is characterizing algae living inside coral samples from the western Pacific island of Palau and the Caribbean island Curaçao to understand how algae and coral are responding to climate change and ocean acidification.

Coral and some algae have a symbiotic, or interdependent, relationship. Corals provide algae with a safe environment in which to grow and necessary compounds for photosynthesis, while the algae produce sugars for the coral and help remove wastes.

Working in the Algal Physiology Research Lab of Mark Warner, professor of marine biosciences, as part of her Semester-in-Residence Program experience, Dodge used the polymerase chain reaction to make copies of numerous DNA sequences. When examined by electrophoresis, the DNA samples unwind and separate into individual bands or “fingerprints” that can be studied.

“I take a picture of the stained electrophoresis gel under a UV light. This gives visual confirmation of the genetic fingerprint of each sample that can later be used for further sequencing,” she said.

Some algae species are known to grow faster or be more thermally tolerant, she continued. Knowing what types of algae live in coral in these regions helps researchers understand how ocean acidification and climate change are affecting coral reefs.

“She is helping to confirm that they are the correct genetic type before we proceed with larger research projects,” said Warner, whose research interests are algal-invertebrate symbioses, climate change and phytoplankton.

Coral reefs are sensitive to temperature and water quality. When temperatures rise, the coral experience a phenomenon called coral bleaching and turn from their normally vibrant colors like orange, red and brown to white. If the algae are not quickly reabsorbed, the coral can die.

As carbon dioxide levels rise, the water’s pH level drops, causing the water to become more acidic. Many coral species then cannot maintain their calcium carbonate skeletons, and the coral can be damaged or destroyed.

“Dani has been instrumental in helping us figure what the algal genetics and physiology can tell us about the thermal tolerance levels of these corals in relation to their tolerance to coral bleaching,” Warner said.

Through genetic testing, researchers are learning more about what reefs can survive, the tolerance levels of the algae and whether or not all types of algae are affected, Dodge explained.

According to the National Oceanic and Atmospheric Administration, scientists estimate that there could be millions of undiscovered species living among coral reefs. This biodiversity has led some scientists to call the reefs 21st century “medicine cabinets” because coral reef plants and animals are important sources of new medicines being developed to treat cancer, arthritis, human bacterial infections, heart disease, viruses and other diseases. If these coral reefs do not continue to thrive, scientists could lose these valuable opportunities.

Now a senior, Dodge plans to continue studying coral reef ecology and climate change in graduate school. “Working in the lab has confirmed my passion for continuing in this research field,” she said.


Photo: UD senior Danielle Dodge studies the DNA of algae living in corals to learn how corals and their algae are affected by climate change

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