By Emma George
In addition to surveys of reef fishes and benthic invertebrates in the main Hawaiian Islands, studies of microbial communities were part of the Pacific Reef Assessment and Monitoring Program (Pacific RAMP) cruise aboard the NOAA Ship Hi`ialakai (PIFSC cruise HA-13-04) that ended today. During this expedition, which began on Aug. 1 and was led by the PIFSC Coral Reef Ecosystem Division, researchers collected 30 water samples and 42 benthic samples for microbial analysis.
Microbes are critical for nutrient recycling and fixing carbon to be used by larger organisms, and viruses release nutrients back into the system by preying on microbes. In 1 mm of ocean water, there are approximately 1 million microbes and more than 10 million viruses. Some species of microbes and viruses are thought to be related to coral disease, an increasing threat to coral reefs worldwide.
Several different methods are used to understand the interactions among coral reefs, microbes, and viruses. One method, metagenomics, allows us to see what microbes and viruses are there and what they do. Microbial and viral DNA is isolated, sequenced, and compared to known species to predict their identity and function.
Another method makes the invisible crowd of microbes and viruses visible. Fluorescent stains allow us to directly count the number of microbes and viruses. The size of the microbes also can be determined with this method, providing the biomass of microbes in a sample.
Finally, nutrients, dissolved organic carbon, and particulate organic matter are measured to investigate how these factors affect coral reef microbes and viruses.
As coral reefs become increasingly stressed because of climate change and pressure from fishing and other human activities, study of the invisible crowd of a reef provides insight to the general health of that reef before it becomes completely degraded. Data gathered during this 2013 Pacific RAMP expedition in the main Hawaiian Islands and other Pacific RAMP cruises will help us gain a better understanding of the role that microbes and viruses play in coral reef ecosystems. These little guys may be out of sight, but they are not out of our minds.
Watch this space early next week for a summary report on this expedition.
Emma George, from the Forest Rohwer Laboratory of San Diego State University, was one of the research partners that participated in PIFSC cruise HA-13-04.