BIOS Study: Climate Change, Ocean Bacteria

July 12, 2012

When it comes to climate change, few people think about potential impacts on bacteria, but that’s just what a team of researchers from the Bermuda Institute of Ocean Sciences [BIOS] and Princeton University did in a recent study chosen as the feature article in the current issue of Aquatic Microbial Ecology.

Led by Dr. Michael Lomas, PI of the Phytoplankton Ecology Lab at BIOS, the team investigated the short-term responses of photosynthetic bacteria populations to a series of treatments that mimic ocean acidification trends from the last glacial minimum [120,000 years ago] to projected year 2100.

Cyanobacteria, or blue-green bacteria as they are commonly known, are ubiquitous across freshwater, marine, and terrestrial environments.

They obtain their energy from photosynthesis, making them important contributors in the global carbon cycle, particularly in the subtropical ocean near Bermuda, and they also convert atmospheric nitrogen into a form that is bioavailable to living organisms in a process called “nitrogen fixation,” making them equally important in global nitrogen cycles.

“The photosynthetic bacteria commonly dominate the plant biomass in the subtropical and tropical ocean,” says Dr. Lomas, “bringing global relevance to these findings.”

Photo: At-sea ocean acidification experiments show contrasting responses between dominant unicellular and colonial natural cyanobacteria populations. Insets (top to bottom): Synechococcus (epifluorescent microscopy), Prochlorococcus (bright-field microscopy) and Trichodesmium (bright-field microscopy).

Lomas and his colleagues examined two cyanobacteria populations in the subtropical North Atlantic: colonies of Trichodesmium and mixed assemblages of Prochlorococcus andSynechococcus.

By altering the pH and pCO2 (partial pressure of carbon dioxide) of the seawater in collected samples, researchers were able to observe how the cyanobacteria responded to new environmental conditions in their carbon and nitrogen fixation rates, cell sizes, and pigment concentrations.

The results, detailed in the paper effect of ocean acidification on cyanobacteria in the subtropical North Atlantic, suggest that cyanobacteria can rapidly change their cellular physiology to adjust to new conditions.

In particular, Trichodesmium were observed increasing their carbon and nitrogen fixation rates given an appropriate supply of nutrients, which are a limiting factor to cyanobacteria growth and production in many areas of the ocean. However, researchers also determined that changes in ocean pH and pCO2 don’t impact all species of cyanobacteria equally or in a predictable manner.

Dr. Lomas points out that, “a future CO2-enriched ocean will also be warmer, with conditions favorable to the growth of these cyanobacteria. Understanding their physiology is increasingly important.”

Photo by S. Jaeger and M. Lomas.

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Category: All, Environment

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