Postdoctoral Scholar Studies Coral Reefs

May 10, 2012

Minor climate changes contribute to reefs' decline

Melissa RothMelissa Roth has always been interested in how changes in the environment – specifically climate change – can affect organisms important to the Earth’s ecosystem.

Roth is now taking a giant step forward into a new branch of her research as a postdoctoral scholar working in Professor Krishna Niyogi’s lab. She is also affiliated with the Lawrence Berkeley National Lab.

Recently, Roth published an important and well-received paper about the effect of both hot and cold temperature increases, caused by climate change, on reef-building coral. The paper Cold induces acute stress but heat is ultimately more deleterious for the reef-building coral Acropora yongei was published in Scientific Reports.

"I enjoy investigating photoprotection in algae because it is essential for their productivity and survival. Ultimately, photosynthesis produces oxygen that most of life depends on. For me it is exciting to unravel these pathways in ecologically relevant species," Roth said.

Coral Reef Research

Coral is extremely important to our environment. Beyond its intrinsic value and role as a breeding ground for ocean fish and other species, coral reefs provide us with resources and services worth many billions of dollars each year. Millions of people and thousands of communities all over the world depend on coral reefs for food, protection, and jobs. These numbers are especially staggering considering that coral reefs cover less than one percent of the Earth’s surface.

 Coral reefs make up one of the world’s most diverse and productive ecosystems. The survival and success of reef-building corals depends on a healthy relationship between corals and their endosymbiotic dinoflagellates, which provide corals with most of their energy.

New hot and cold temperatures, even within a few degrees, can have a very negative effect on coral reef-building, and contribute to the decline of coral reefs. Corals build the foundation of the coral reef ecosystem which has social, economic and cultural benefits such as providing a home to approximately one-fourth of all marine organisms, and as a source of potential biopharmaceuticals, nursery grounds for fish, shoreline protection, commercial fishing and tourism.

Roth’s paper, published with co-authors Ralf Goericke and Dimitri D. Deheyn, determined that both hot and cold climate changes – even by a few degrees - are detrimental to coral. The team exposed the branching coral Acropora yongei to a five-degree plus or minus temperature change, and concluded:

  • Cold-treated corals initially show greater declines after the exposure to temperature change, but then acclimate and show improvement.
  • In the short term, cold temperature change is more damaging for branching corals.
  • Heat did not initially harm photochemical efficiency, but after a delay photosynthetic pressure increased rapidly and corals experienced severe bleaching and cessation of growth.
  • Long-term warm temperatures are more harmful than long-term cold temperatures.

Coral GardensRoth earned her Ph.D. from the Scripps Institution of Oceanography, University of California at San Diego, in 2010. Her research focused on the ecology and physiology of reef-building corals.

“My dissertation research investigated both the coral host and the symbiotic dinoflagellates’ response to changes in light and temperature,” Roth said. Endosymbiotic dinoflagellates are dinoflagellates that live inside the cells of corals and have a symbiotic relationship with them. They provide the coral with  approximately 90 percent of its energy.

She also volunteered for the U.S. Fish and Wildlife Service and worked for the US Geological Survey in the northwestern Hawaiian Islands doing conservation ecology work, including restoration ecology, seabird monitoring, and endangered species  research.

As an undergrad, Roth designed her own major at Stanford University which was a combination of biology and geology with a focus on the oceans, which she named “Ocean Sciences” and conducted research on intertidal whelk behavioral ecology and population genetics under George Somero and Eric Sanford.

During her PhD research, she was especially interested in the photoprotective mechanisms of the coral host (how coral protects itself and potentially its algal symbionts from too much light, and how it sheds that extra energy) and decided that she wanted to study algal mechanisms of photoprotection for her postdoctoral studies.

Work at Niyogi Lab, LBNL

The main pathway for photoprotection of photosynthesis is non-photochemical quenching (NPQ) which is Krishna Niyogi’s areas of expertise. Non-photochemical quenching (NPQ) is a mechanism employed by plants and algae to protect themselves from the adverse effects of high light intensity. NPQ is believed to occur in all oxygenic photosynthetic eukaryotes (algae and plants), and helps to regulate and protect photosynthesis in environments where light energy absorption exceeds the capacity for light utilization in photosynthesis.

The Niyogi lab primarily focuses on the model organisms Arabidopsis and Chlamydomonas. Their research has led to the discovery of the NPQ mechanisms in these organisms.

The Niyogi Lab found different mechanisms of NPQ between plants and algae, so it’s likely that different types of algae may also have different NPQ mechanisms.

Roth’s research in the Niyogi lab will investigate NPQ in non-model organisms including coral endosymbiotic dinoflagellates, marine phytoplankton and freshwater algae.

“The implications for this research are not only to understand ecologically relevant species, but also may give insight into improving biofuel and crop production through providing new photoprotection pathways that can be inserted into species of interest” Roth said. “Research among different types of algae will provide insight into the evolution and basic mechanisms of photosynthesis.”

By understanding more about the photosynthetic apparatus and how it functions, we may then be able to manipulate it to improve production under specific conditions, Roth said. For example, enhancing photoprotective capacity may improve growth of crop plants or biofuel production ponds that are outside and experience various abiotic stresses. However, if biofuel production is conducted in a closed systMelissa Rothem such as in bioreactors, reducing the photoprotective pathways may help achieve faster biomass production.

The departure in her research will enable Roth to gain more tools and perspectives to conduct novel research in the future.

As part of her research in the Niyogi lab, Roth recently went down in a three-man submersible, the PICES V, to collect coral and macroalgal samples from a depth of 120 meters off the coast of Hawaii. Understanding how these organisms conduct photosynthesis in such little light may provide new insights into how algae regulate photosynthesis.