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Bacterioplankton

**This is what is currently the introduction for bacterioplankton.We can edit/add to this

Bacterioplankton refers to the bacterial component of the plankton that drifts in the water column. The name comes from the Ancient Greek word πλανκτος (planktos), meaning "wanderer" or "drifter" (Thurman, 1997), and bacterium, a Latin neologism coined in the 19th century by Christian Gottfried Ehrenberg. They are found in both seawater and freshwater.

Bacterioplankton occupy a range of ecological niches in marine and aquatic ecosystems. They are both primary producers and primary consumers in these ecosystems and drive global biogeochemical cycling of elements essential for life (e.g., carbon and nitrogen fixation). Many are saprotrophic, and obtain energy by consuming organic material produced by other organisms. This material may be dissolved in the medium and taken directly from there, or bacteria may live and grow in association with particulate material such as marine snow. Many other bacterioplankton species are autotrophic, and derive energy from either photosynthesis or chemosynthesis. The latter are often categorised as picophytoplankton, and include cyanobacterial groups such as Prochlorococcus and Synechococcus. Bacterioplankton play critical roles in global nitrogen fixation, nitrification, denitrification, remineralisation and methanogenesis.

Like other small plankton, the bacterioplankton are preyed upon by zooplankton (usually protozoans), and their numbers are also controlled through infection by bacteriophages.

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diversity depends on predation and nutrient availability

Types

Photosynthetic Bacterioplankton

Photosynthetic bacterioplankton are responsible for a large proportion of the total primary production of aquatic food webs, supplying organic compounds to higher trophic levels. These bacteria undergo oxygenic and anoxygenic photosynthesis. Differences between these processes can be seen in the byproducts produced, the primary electron donor, and the light harvesting pigments used for energy capture.

Cyanobacteria, orginally named blue-green alage, are organisms responsible for the oxygenic photosynthesis from bacterioplankton communities in aquatic ecosystems. They use photosynthetic to generate oxygen and organic compounds for energy storage. Cyanobacteria, along with photosynthetic eukaryotes, are responsible for approximately half of the total global primary production. Major light harvesting pigments in cyanobacteria include chlorophylls, phycoerytherin, phycocyanin and carotenoids. The majority of cyanobacteria found in coastal and marine environments are represented by the genera Synechococcus and Prochlorococcus. Some species of cyanobacteria are responsible for harmful blooms after water eutrophication and producing toxins. Oftenm cyanobacteria grows in colonies. Many Cyanobacteria are also capable of nitrogren fixation. Anabaena uses specialized cells called heterocysts to physically separate the nitrogen fixation from oxygen producing photosynthesis due to the toxicity of oxygen to nitrogen fixation. Trichodesmium is another cyanobacteria that also is capable of fixing nitrogen while undergoing photosynthesis. Instead of using heterocysts, Trichodesminum uses an alternative photosyntheitc pathway to fix nitrogen.

Anoxygenic photosynthetic bacteria:use sulfur compounds, or alternative hydrogen sources for electrons, found in freshwater, brackish,marine, and hyper saline.

Proteobacteria (Purple bacteria): alternative hydrogen sources to water, produce sulfur, anaerobic water due to oxygen supression of pigment synthesis, use hydrogen sulfide instead of water, bacteriochlorophyll a and b, some show chemoautotrophy. PS in lamellae, color due to carotenoids, pigment synthesis limited by light intensity (more light = less pigments). Sulfur (g-, sulfide produced intracellularly, anoxic region of water column) and non sulfur (low-sulfur conditions, sulfur produced outside of organism, anaerobic growth in dark, ) types.

Green bacteria: brown colour from carotenoids, g-, BChl, chlorosomes, 2 types: sulfur (anaerobic obligate phototroph) and non-sulfur (filamentous, thermophilic, no sulfur production)

Heterotrophic Bacterioplankton

Heterotrophic bacterioplankton rely on the available concentration of dissolved organic matter in the water column. Usually these organisms are saprophytic, absorbing up nutrients from their surroundings. These heterotrophs also play a key role in the microbial loop and the remineralization of organic compounds like carbon and nitrogen. Pelagibacterales, also known as members of an alphaproteobacteria clade, are the most abundant bacterioplankton in the oceans and are found in waters with low nutrient availability.

Trophic Interactions

**Could be interactions with other primary producers/consumers as well as viruses, or even how size/ composition of bacteria determines how they are grazed/preyed on

Or could do a section on seasonality of bacterioplankton

Ecological Significance

Blooms or impact on human populations? ##Maybe a section of Human Impact or Anthropengic Pollution - like how they are impacted by human-made pollution (like agriculture run off and heavy metal contamination)