//
you're reading...

Climate Change

Who benefits from more CO2? Harmful algae.

The paper:

Sandrini, G., Ji, X., Verspagen, J.M., Tann, R.P., Slot, P.C., Luimstra, V.M., Schuurmans, J.M., Matthijs, H.C. and Huisman, J., 2016. Rapid adaptation of harmful cyanobacteria to rising CO2. Proceedings of the National Academy of Sciencesdoi:10.1073/pnas.1602435113

 

Background: the winners and losers of climate change

Climate change will generate both winners and losers, but who will the winners be? We need to understand what organisms are benefited and harmed by climate change in order to predict how ecosystems will look in the future. Higher CO2 concentrations as a result of fossil fuel emissions is one example of how environmental conditions are changing. CO2 dissolved in surface waters is a key ingredient in photosynthesis for algae and aquatic plants, so their ability to compete for it against their neighbors determines in part whether or not they survive and proliferate.

Figure 1: green slime from a cyanobacteria bloom (Ohio Sea Grant/Creative Commons)

Figure 1: green slime from a cyanobacteria bloom (Ohio Sea Grant/Creative Commons)

Different organisms have different strategies of competing for CO2 and other nutrients. Some algae (often larger organisms) have a large storage capacity: they take up nutrients relatively slowly when nutrients are scarce, but are able to increase their uptake more when nutrients are more abundant.  You can imagine these organisms do better when nutrients are plentiful! In contrast, other algae are good at scavenging nutrients when they are scarce, but reach their storage limit quickly. These are often smaller algae with a higher ratio of surface area to body size, giving them in an advantage in absorbing scarce nutrients. Increasing CO2 concentrations in the ocean could therefore disrupt the current competitive balance between types of algae, tipping the scales in favor or organisms adapted to higher CO2 concentrations.

Cyanobacteria are the tiniest algae in the ocean and can form toxic blooms when they outcompete other types of algae (Figure 1). Due to their small cell size, they are usually considered to be well adapted to low CO2 concentrations. They therefore might be expected to be losers in a future high-CO2 ocean. However, different types of cyanobacteria have different mechanisms for acquiring CO2, each with a different tradeoff between how quickly they take up CO2 and their storage capacity. This raises the possibility that cyanobacteria could adapt to increasing nutrient concentrations and maintain their competitive advantage in the future.

 

Can cyanobacteria adapt to higher CO2?

A new paper in the Proceedings of the National Academy of Science tests the potential for the cyanobacterial community to adapt in response to increasing CO2. First, the authors conducted a lab experiment with 5 different strains of the cyanobacterium microcystis, each containing a different mechanism for CO2 uptake. Those with the BicA gene specialized in rapid uptake at high concentrations, while those with SbtA could better compete for CO2 at low concentrations. They used both a high (1000 ppm) and low (100 ppm) CO2 treatment to test how increasing the concentration would affect competition among the different strains.

Figure 2: the algal community during the lab experiments. In the low-CO2 experiment (left) cyanobacteria with both CO2 uptake genes dominated (bicA+sbtA), while in high-CO2 conditions (right) a strain adapted for rapid uptake in high-nutrient conditions was also successful (bicA). From Sandrini et al. 2016.

Figure 2: the algal community during the lab experiments. In the low-CO2 experiment (left) cyanobacteria with both CO2 uptake genes dominated (bicA+sbtA), while in high-CO2 conditions (right) a strain adapted for rapid uptake in high-nutrient conditions was also successful (bicA). From Sandrini et al. 2016.

Overall, the cyanobacteria grew faster at higher CO2 concentrations, and the total biomass at the end of the experiment was 2.5 time higher than in the low concentration experiment. The different concentrations also changed the competition among the different strains. At low concentrations, a toxic strain with both the BicA and SbtA genes completely took over and outcompeted the other cyanobacteria. At high concentrations, the toxic strain with only BicA coexisted with a nontoxic strain with both genes (Figure 2). This showed that under higher CO2 concentrations, natural selection will favor organisms able to capitalize on the additional nutrients.

Figure 3: seasonal changes in the lake cyanobacteria community. Strains with both types of CO2 uptake genes dominated in the summer, when concentrations were low, but they were rapidly replaced by cyanobacteria adapted for higher CO2 conditions in fall. From Sandrini et al. 2016.

Figure 3: seasonal changes in the lake cyanobacteria community. Strains with both types of CO2 uptake genes dominated in the summer, when concentrations were low, but they were rapidly replaced by cyanobacteria adapted for higher CO2 conditions in fall. From Sandrini et al. 2016.

A field study was also conducted in Lake Kennemermeer in the Netherlands. This lake regularly experiences cyanobacteria blooms so severe the water is not considered safe to swim in. CO2 concentrations in the lake are very low during the summer due to high algal activity, and increase in the fall when the population is smaller. Strains with genes for both uptake mechanisms dominated in the summer when CO2 was scarce. But in the fall, as concentrations increased, they were replaced with strains with only BicA, adapted to the higher CO2 (Figure 3). The replacement of the population was very rapid, occurring within 2 months or 12-42 generations of the cyanobacteria. Both the lab and field experiments indicate that at higher concentrations of CO2, organisms able to take up CO2 more rapidly outcompete organisms adapted to lower CO2 conditions.

 

Implications

The study demonstrates rapid evolution of a cyanobacterial species, both in the lab and in natural conditions—not from new mutations, but by natural selection acting on existing diversity within the population. We like to think of evolution as something happening over thousands or millions of years. But for bacteria with short lifespans, it can happen in just months. This means that when thinking about the winners and losers of climate change, we can’t just think about what species will do well and which will suffer. Instead, we must consider that species themselves will adapt to new conditions as they occur. Unfortunately, toxic cyanobacteria are among the most genetically diverse and capable of rapid evolution. They will probably be fine, at the expense of more desirable algal species.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 9 hours ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 1 week ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 2 weeks ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 3 weeks ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 1 month ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 3 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 3 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 4 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 4 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 5 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 5 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 6 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 6 months ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
  • by oceanbites 7 months ago
    Feeling a bit flattened by the week? So are these summer flounder larvae. Fun fact: flounder larvae start out with their eyes set like normal fish, but as they grow one of their eyes migrates to meet the other and
  • by oceanbites 7 months ago
    Have you seen a remote working setup like this? This is a photo from one of our Oceanbites team members Anne Hartwell. “A view from inside the control can of an underwater robot we used to explore the deep parts
  • by oceanbites 8 months ago
    Today is the day of  #shutdownacademia  and  #shutdownstem  and many of us at the Oceanbites team are taking the day to plan solid actions for how we can make our organization and the institutions we work at a better place
WP2Social Auto Publish Powered By : XYZScripts.com