Name of plankton: SAR11

Where sample was found: Bermuda Atlantic Time-series Study (BATS) site, 80m

Project: Microbial Observatory

Photo credit: Rachel Parsons, BIOS

What role do these organisms play in the ecosystem: SAR11 are heterotrophic bacteria that dominate the euphotic zone of the ocean comprising up to 40% of the total bacterioplankton population. They are known as oligotrophs or scavengers that feed on dissolved organic carbon and nitrogen and are important in the marine carbon and nitrogen cycles.

Interesting facts: The photo shows total bacterioplankton on the left in blue stained with DAPI. The photo also shows SAR11 in the middle targeted using Fluorescent in-situ hybridization with oligonucleotide probes labeled with Cy3. The right hand side shows the two images overlaid with SAR11 positive cells shown in pink.

SAR11 has one of the smallest number of open reading frames of any free living organism, but it still has metabolic pathways for all 20 amino acids and most co-factors. Its genome has been streamlined, thereby reducing the amount of energy required for cell replication.

Name of plankton: Ceratium

Where sample was found: Bermuda Atlantic Time-series Study (BATS) site

Project: Microbial Observatory

Photo credit: Rachel Parsons, BIOS

What role do these organisms play in the ecosystem: The genus Ceratium includes marine dinoflagellates. Species of Ceratium contain two flagella of different lengths. They also contain armored plates that are composed of cross-linked cellulose. These plates can form horns.

Interesting facts: Some species of Ceratium are mixotrophs capable of both photosynthesis and heterotrophic feeding. Ceratium dinoflagellates have a unique adaptation that allows them to store compounds in a vacuole that they can use for growth when nutrients become unavailable.

Name of plankton: Oceanic bacterioplankton

Where sample was found: Hydrostatic S, 800m depth

Project: BIOS-SCOPE

Photo credit: Rachel Parsons, BIOS

What role do these organisms play in the ecosystem: Oceanic Bacterioplankton often attach to particles known as marine snow. These bacteria and archaea are attached to marine snow particles where they are breaking down dissolved organic matter thereby making it available to higher trophic groups via the trophic pathway known as the microbial loop.

Interesting facts: This image was taken from 800m where there was almost a two-fold increase in bacterioplankton from what was seen at 600m and 1000m.