Marine Microbes

Microorganisms are everywhere in the marine environment. Diatoms (phytoplankton), Foraminifera (protist), Synechococcus (cyanobacteria), Vibrio cholerae (bacteria), and Roseophage (virus) are all examples of marine microbes. Though the size of each individual is small, their significance to the biological and ecological processes in the ocean is enormous. Marine microbes are abundant. For example, in a drop of coastal ocean seawater there are more than 40,000 bacteria and archaea. It is estimated that there are more than 10 to the power 29 total microbes in the world ocean. Microbes comprise most of the ocean's biomass, about 0.6 to 1.9 times 10 to the power of 15 grams carbon. About 75 percent of the microbial biomass is found in the upper 0 to 150 m of the water column where the availability of sunlight enables photosynthesis. The remaining 25 percent is found in deep seawaters. With an average ocean depth of about 4000 m, the concentration of microorganisms decreases gradually with increasing water depth. However, benthic sediments contain very high concentrations of microbes and this enormous reservoir of microbes also affects biological and geological processes on the global scale.

A collection of marine microbes. The darkest ones are a very common filamentous form that at present have not been formerly identified in scientific literature. The large pink ovoid is a cell of Chromatium a purple sulphur bacterium, the green is a cyanobacterium. The curving structure at about 2 o'clock is a diatom (Nitzschia), which is a photosynthetic eukaryote. Photo credit: D. J. Patterson, L. Amaral-Zettler and V. Edgcomb. Courtesy of micro*scope. Download hi-res version (zip file 2MB).

Biodiversity is extremely high among marine microbes. The International Census of Marine Microbes (ICoMM) is a project of the Census of Marine Life (CoML). A recent publication supported by ICoMM suggests that marine microbial diversity may be 10 - 100 times greater than previously thought and that the vast majority of this diversity is due to unknown, low abundance organisms.

Many human activities are closely dependent on coastal oceans and therefore microbes that live in these ecosystems are important to human activities. Sewage spills from overflows and broken pipes can greatly effect the biological processes that occur near beaches and within coastal recreational waters. In some parts of the world, beaches are closed to human use when levels of certain fecal bacteria exceed public health standards. Storm-drain runoff, which sometimes contain pathogenic bacteria from urban areas, farms, wild animals, and non-point source sewage leaks, may contribute to the water quality along coastal zones. Many scientific efforts have focused on understanding the survival and proliferation of disease-causing bacteria in the ocean.

Microbiology is an exciting aspect of biological oceanography. Microbial assemblages in ecosystems as diverse as polar seas and hydrothermal vents have been explored. Recent research efforts in marine microbiology include:

 

• Ecology of marine viruses, bacteria and phytoplankton, and the roles these organisms play in marine food webs and biogeochemical cycles
• Microbial symbioses with marine invertebrates
• Bioluminescent fish and invertebrates including reef building corals
• Microbial adaptations to pressure and temperature extremes and other environmental stresses in the marine environment
• Massive gene sequencing of marine microbes to discover genetic and molecular bases of adaptations to ocean conditions
• Geomicrobiology, and
• Use of bacteria in bioremediation