Ocean acidification caused by climate change is a serious threat. Excess carbon dioxide combines with ocean water to produce carbonic acid, which impacts numerous marine organisms, including bacteria. David Hutchins of the University of Southern California, in collaboration with the Woods Hole Oceanographic Institution, reports that the growth of the marine bacterium Trichodesmium is significantly altered by conditions that mimic ocean acidification.
Trichodesmium (Tricho, for short) is a filamentous cyanobacterium found in numerous marine waters, including the Atlantic, Pacific, and Indian oceans. It is sometimes called “sea sawdust”, named for the large brown blooms it forms on the ocean surface. Cyanobacteria produce energy through photosynthesis, but Tricho also fixes atmospheric nitrogen into ammonium, which can be used by other organisms. This makes it a crucial member of the marine ecosystem. (Unlike most bacteria, these cells are up to 4 mm long, making them visible to the naked eye!)
In their study, published in Nature Communications, Hutchins and colleagues grew Tricho under conditions that mimicked the climate changes predicted for the year 2100. Unexpectedly, these conditions drove Tricho to increase its nitrogen consumption by nearly 50%. The bacteria also increased their growth rates and, as a result, nutrient consumption went up.
The most striking finding was that these “adaptations” were permanent. If other microbes react to climate change in the same way, marine organisms could be starved for nutrients. According to Hutchins, “losing the ability to regulate your growth rate is not a healthy thing … the last thing you want is to be stuck with these high growth rates when there aren’t enough nutrients to go around. It’s a losing strategy in the struggle to survive”.