Results from the latest Census of Marine Life study are in, highlighting spectacular examples of hard-to-see underwater microbes, part of a wider study involving four research groups looking at some of the smallest sea species.
This amoeba grows fragile, crystal shells of strontium sulphate. They're found almost everywhere across the world's oceans and lead their adult lives within 300 metres of the surface. During reproduction, the amoeba walls itself in and forms a cyst. This cyst falls like a microscopic snowflake towards the seabed. They have been found as deep as 2000 metres.
Within the sinking shell, the amoeba divides several times so that when the strontium sulphate dissolves, daughter cells can feast on sinking dead phytoplankton.
Acantharians form cysts at any time of year, but the rate is highest in spring, possibly coinciding with the abundance of dead phytoplankton from algal blooms.
(Image: Dr. Linda Amaral Zettler)
This phytoplankton lives on the surface of the ocean. The image clearly shows its spidery setae: long hair-like structures that radiate out from the central, silicate-walled cell. Rather than the familiar green chloroplasts of plants, its photosynthetic material is yellow-brown. This cylindrical microbe links up with neighbours to form filaments.
This specimen was captured off Martha's Vinyard in Massachusetts, part of the thriving Bacteriastrum community among the surface phytoplankton species there.
(Image: J. Cole)
Unassuming as this lonely specimen may appear, this single-celled alga is the cause of so-called "red tides" in the Gulf of Mexico, forming typically between August and February. During this period the multitude of Karenia brevis gives the water a reddish tinge. The algae secrete a neurotoxin that paralyses and kills fish by halting respiration, leaving many dead fish to wash onto the shore.
The flagella of K. brevis cause it to move in a spinning motion, and it can be photosynthetic.
(Image: Bob Andersen and D. J. Patterson)
These examples, found in the Sargasso Sea, build bubble-like defences of calcium carbonate or silicates. Within them live single-celled jelly-like plankton.
Living in the deepest parts of the ocean, they constantly "rain" dead plankton onto the sea floor. Their carbonate bubbles fossilise well, resulting in one of the most complete fossil records dating back to the mid-Jurassic period.
Their fossils are particularly valuable for dating nearby rocks and for historical climate science, because their bubble composition reflects the materials available at the time. In addition, geographical patterns in Foraminifera fossils can reveal ancient ocean currents.
(Image: Colomban de Vargas, EPPO/SBRoscoff)
Microbial mats, thought once to have covered early Earth, are now restricted to regions of extreme conditions where competitors cannot survive: salt marshes, arid temperate deserts, hot springs or Antarctica.
As a layered combination of microbes, these mats form their own mini-ecosystems. Photosynthetic and chemotrophic bacteria live in the mats, with some microbes living off the by-products of others. They can respire both with oxygen, as we do, or without, depending on their depth in the mat.
This particular mat cross-section comes from Baja California, a high-salinity area. The different groups of microbes are evident in the layers.
(Image: D. J. Patterson, under license to MBL)
The chloroplasts of this bioluminescent dinoflagellate follow the sun across the cell. This individual is dividing – the separated nuclei are visible above and below the central knot of photosynthetic material
(Image: Bob Andersen and D. J. Patterson)
This slender microbe is a pennate, or feather-shaped, diatom. The brown photosynthetic elements are enclosed in a silicate "glasshouse". Made of two mirror-image halves, pennate diatoms developed after their cylindrical cousins.
Fresh water favours pennate diatoms. The porous, silicate shells are so finely marked that they are used to test microscopes' resolution. One such marking is the raphe, a groove often lined with cilia which is thought to be a mechanism that allows pennate diatoms to slowly glide through the water.
(Image: L Amaral-Zettler and D. J. Patterson)