you're reading...


Microbialites are the unseen power house for marine and inland sea ecosystems

Microbes: tiny but mighty

Invisible to our eyes, microbes maintain energy flow in marine, freshwater, and inland sea food webs. Microbial communities are composed of diverse groups of Bacteria, Algae, and Fungi. In just a few places around the globe,  microbial communities can build incredible structures that can be seen without the aid of a microscope!

Going back in time to understand the present

Microbes evolved billions of years ago, when Earth’s atmosphere was not hospitable to more complex life forms. Microbes living at that time had to figure out a way to survive in the face of adverse conditions. What are microbes to do during such dire times? Stick together! Microbes can stick together in cohesive mats, or biofilms, that allow the microbes to control the local environmental conditions. Maybe at one point you have seen green slimy stuff on the sides of a fish bowl; several microbes can secrete sticky glue called exopolymeric substances (EPS) that allows them to live as a biofilm attached to a surface. This glue is also important for trapping and binding minerals to build a more stable habitat for the microbial community, a process which over time can result in impressive stromatolite structures (Bowlin et al. 2012). Amazingly, this process of sticking together, which occurred eons ago, is still happening today!

Stunning microbial towers found in Pavilion Lake, British Columbia. Photo source: Pavilion Lake Research Project via Wikimedia Commons.

Because microbes grew during adverse times, present-day microbes tend to thrive in “extreme” environments, such as hypersaline lakes and thermal springs, as well as marine systems (Fernandez et al. 2016). In a few extreme locations throughout the world, scientists have discovered remarkable types of biofilm communities, called microbialites.

Microbialites are reef-like structures that contain abundant communities of Algae, Bacteria, Fungi, and Archaea. Some of the most abundant microbialites can be found in marine coastal systems as well as “inland seas” such as Utah’s Great Salt Lake. Microbialites are increasingly regarded as important study systems to help us understand how microbes contribute to globally important processes such as carbon cycling, and they are also gaining attention as an important food source for aquatic organisms.

How do microbialites form?

The formation of microbialites depends on the interplay between the surrounding water chemistry and types of microbes floating around. Scientists often find microbialites in shallow, clear lakes and marine ecosystems that have many dissolved cations, such as calcium, as these are necessary for the reef-like part of microbialites. In addition, lakes and coastal areas with substantial groundwater input may have high numbers of cations and organic matter to fuel microbialite formation (Dupraz et al. 2009).

Here is a conceptual overview of microbialite formation. All photos except for person (me) holding microbialite are via Wikimedia Commons.

Cyanobacteria, a major group of bacteria, are dominant photoautotrophs (photosynthesizing organisms) that create localized increases in pH of the water. This happens because photosynthesis by Cyanobacteria consumes carbon dioxide, CO2, often at a faster rate than CO2 can be replaced from the atmosphere. This rapid depletion of CO2 changes the surrounding water chemistry and allows free-floating calcium to bond with carbonate molecules, becoming a solid mineral that falls out of the water column. This solid mineral is now ready to be colonized by microbes, and over time, more minerals form, which eventually become incorporated into a highly organized microbial architecture. Some microbes produce sticky glue-like substances which keep other important members of the biofilm, such as diatoms, firmly attached to the microbialite surface (Baumgartner et al. 2009). These become highly organized communities, usually with photosynthesizers at the top, and various other types of microbes are found below the surface.

What exactly does a microbialite do?

Each of the different types of bacteria, algae, and fungi perform specific functions in their environment; they are the cogs and wheels that make the microbialites extremely productive habitats (Dupraz and Visscher 2005). Through DNA sequencing technologies, scientists have uncovered the diversity of microbes contained on microbialites, which has allowed them to determine who does what in these ecosystems. Scientists have found that Cyanobacteria are the dominant photosynthesizing bacteria on marine, hypersaline, and freshwater microbialites (Couradeau et al. 2011, Foster and Green 2011, White et al. 2015). Microbialites also contain heterotrophic species, which get their energy by consuming sugars and other molecules produced by Cyanobacteria, diatoms, and algae. Yet other microbes process sulfur, nitrogen, phosphorus, and even metals (Saghai et al. 2016). Because of the high numbers of photosynthesizing microbes, microbialites play an important role in the global carbon cycle. Together, all of these processes contribute to the recycling of nutrients, an important aspect of ecosystem functioning.

(Featured image) Up-close view of a microbialite collected from Great Salt Lake. If you look closely, you might notice several brownish things-those are brine flies, an important organism in the lake that relies on microbialites to complete their life cycle. Photo: K. Barrett.

Cryptic resources

Microbialites are part of the benthos, the bottom portion of marine and inland lake ecosystems, a previously overlooked component of aquatic food webs. Pelagic (open-water) organisms were previously thought to only feed on resources contained in the water column, but emerging research is pointing to the importance of benthic biofilm as a food source for these consumers (Vadeboncoeur and Power 2017). Therefore, microbialites and their productive biofilms highlight an emerging theme in ecology: unseen resources often contribute unexpectedly to the functioning of ecosystems we value and seek to protect. In fact, abundant biofilms contained on microbialites in marine and hypersaline ecosystems are likely an important food source for invertebrates (Lindsay et al. 2017, Rishworth et al. 2018).

Those obscured dark shapes may look like nothing special, but those are microbialites in the Great Salt Lake, Utah! Where the water is clear, one can easily see these communities from a boat. Photo: K. Barrett.

Uncertain future

Microbialites thrive in extreme environments, but increasing human stresses threaten these rare ecosystems. Climate change, pollution, and increasing water diversions for agriculture all pose threats to the health and functioning of microbialites. The persistence of microbialites depends on a delicate balance between surrounding water properties and the composition of the resident microbial community, both of which may be altered by global change.

Of major concern is that increasing salinity and nutrient inputs will cause the important photosynthetic Cyanobacteria, the main builders of microbialites, to diminish in number, and be replaced by other microbes that may negatively impact microbialites. Lindsay et al. (2017) found that high salinity in one section of Great Salt Lake, Utah, corresponded with a reduction of the photosynthesizing Cyanobacteria and a rise in heterotrophic bacteria, a change which may hinder further microbialites growth. Similarly, in a study of Lake Clifton microbialites, Smith et al. (2010) reported that a trend of increasing salinity over the past three decades coincided with a major shift in the dominant microbialite communities. This study found a startling decline in a group of Cyanobacteria that formed the foundation of microbialite formation, and an increase in numbers of other bacteria that may not be able to maintain microbialite growth. Based on these studies, it is apparent that continued research will need to occur in a variety of marine and lake ecosystems to increase our understanding of how microbialite communities will respond to global change.


Baumgartner, L. K., C. Dupraz, D. H. Buckley, J. R. Spear, N. R. Pace, and P. T. Visscher.  2009.  Microbial species richness and metabolic activities in hypersaline microbial mats: insight into biosignature formation through lithification.  Astrobiology 9:861-874.

Bowlin, E. M., J. S. Klaus, J. S. Foster, M. S. Andres, L. Custals, and R. P. Reid.  2011.  Environmental controls on microbial community cycling in modern marine stromatolites.  Sedimentary Geology 263-264:45-55.

Couradeau, E., K. Benzerara, D. Moreira, E. Gérard, J. Kaźmierczak, R. Tavera, P. López-García.  2011.  Prokaryotic and eukaryotic community structure in field and cultured microbialites from the alkaline Lake Alchichica (Mexico).  PLoS ONE 6: e28767. doi:10.1371/journal.pone.0028767.

Dupraz, C., R. P. Reid, O. Braissant, A. W. Decho, R. S. Norman, and P. T. Visscher.  2009.  Processes of carbonate precipitation in modern microbial mats.  Earth-Science Reviews 96:141-162.

Dupraz, C., and P. T. Visscher.  2005.  Microbial lithification in marine stromatolites and hypersaline mats.  Trends in Microbiology 13:429-438.

Fernandez, A. B., M. C. Rasuk, P. T. Visscher, M. Contreras, F. Novoa, D. G. Poire, M. M. Patterson, A. Ventosa, and M. E. Farias.  2016.  Microbial diversity in sediment ecosystems (evaporites domes, microbial mats, and crusts) of hypersaline Laguna Tebenquiche, Salar de Atacama, Chile.  Frontiers in Microbiology 7:1284.

Foster, J. S., and S. J. Green.  2011.  Microbial diversity in modern stromatolites.  Life in Extreme Habitats and Astrobiology 18:383-405.

Lindsay, M. R., C. Anderson, N. Fox, G. Scofield, J. Allen, E. Anderson, L. Bueter, S. Poudel, K. Sutherland, J. H. Munson-McGee, J. D. Van Nostrand, J. Zhou, J. R. Spear, B. K. Baxter, D. R. Lageson, E. S. Boyd, Microbialite response to an anthropogenic salinity gradient in Great Salt Lake, Utah.  Geobiology 2017:1-15.

Papineau, D., J. J. Walker, S. J. Mojzsis, and N. R. Pace.  2005.  Composition and structure of microbial communities of Hamelin Pool in Shark Bay, Western Australia.  Applied and Environmental Microbiology 71:4822-4832.

Rishworth, G. M., R. Perissinotto, M. S. Bird, and N. Pelletier.  2018.  Grazer responses to variable macroalgal resource conditions facilitate habitat restructuring.  Royal Society Open Science 5:171428.

Smith, M. D., S. E. Goater, E. S. Reichwaldt, B. Knott, and A. Ghadouani.  2010.  Effects of recent increases in salinity and nutrient concentrations on the microbialite community of Lake Clifton (Western Australia): are the thrombolites at risk? Hydrobiologia 649:207-216.

White, R. A., I. M. Power, G. M. Dipple, G. Southam, and C. A. Suttle.  2015.  Metagenomic analysis reveals that modern microbialites and polar microbial mats have similar taxonomic and functional potential.  Frontiers in Microbiology 6:966 doi: 10.3389/fmicb.2015.00966


No comments yet.

Post a Comment


  • by oceanbites 3 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 4 months ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 5 months ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 6 months 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 7 months 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 7 months 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 7 months 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 8 months 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 8 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 8 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 8 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 9 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 9 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 10 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 10 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 11 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 11 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 12 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 12 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 1 year 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 
WP2Social Auto Publish Powered By : XYZScripts.com