Cryptic Biodiversity: The Microbes That Make Our Ecosystems Work
All animal and plant plant life is underpinned by a complex community of microbes that are fundamental to the healthy function of ecosystems. Tiny single-celled organisms that live in freshwater, soil, marine environments, and even ice form their own 'micro-ecosystems' which consist of photosynthetic microscopic plants, minute grazers, and predators which feed on them.
Single-celled algae and cyanobacteria ('blue-green algae') form the basis of microbial food webs, playing a role similar to that of plants. They are able to convert energy from sunlight into organic material such as carbohydrates just like land-based plants can. Under the right conditions, these microscopic plants can form blooms which can be seen as a green mass in fresh and salt water.
Grazers that feed on this algae include microflagellates—tiny single-celled organisms, about one hundredth of a millimetre, which have tail like projections called flagella—and ciliates, which feed on algae, bacteria, and flagellates in the water.
The ciliates belong to the group of organisms known as protozoa ('first animals', though this is a little misleading as protozoa are no longer classed as animals) and are particularly important as they serve as the main predators in this system. Ciliates are easily identified by cilia, which are hair-like projections around the cell, which are used in feeding and movement. They feed on all other microbes, from bacteria to algae, other protozoa (such as microflagellates and even other ciliates), and even microscopic animals (for example the ciliate Litonotus which has been found feeding on microscopic worms).
The ciliates are responsible for linking microbial food webs with animal-based food webs, as small animals such as rotifers and nematode worms feed on them, and these are then fed on by larger invertebrates and insects. When protozoa die, they release organic matter left in the cell (particulate organic matter, POM), which is used by bacteria for food; thus some of the energy accumulated by microbial predators is returned to the producers. This process is known as the microbial loop, and it fuels the success of animal-based food webs, constantly recycling organic matter and energy.
Although these microbes are invisible to the naked eye, they are just as important for the function of a healthy ecosystem as larger creatures are. By monitoring these communities, we can understand how changes in the microbial loop will impact large-animal food webs.
© 2017 Jack Dazley