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A mixoplankton is a mixotrophic plankton, capable of both photosynthesis and predation. That is, it is a plankton that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixoplankton comprise more than half of all microscopic plankton. There are two types of mixoplankton: those with their own , and those with —and others that acquire them through kleptoplasty or by enslaving the entire phototrophic cell.
Recognition of the importance of mixotrophy as an ecological strategy is increasing, as well as the wider role this may play in marine biogeochemistry. Studies have shown that mixotrophs are much more important for marine ecology than previously assumed and comprise more than half of all microscopic plankton. Their presence acts as a buffer that prevents the collapse of ecosystems during times with little to no light.
The distinction between plants and animals often breaks down in very small organisms. Possible combinations are phototroph and , lithotroph and , autotroph and or other combinations of these. Mixotrophs can be either eukaryote or prokaryote. They can take advantage of different environmental conditions.
A 2017 study of marine microzooplankton found 30–45% of the ciliate abundance was mixotrophic, and up to 65% of the amoeboid, foram and radiolarian biomass was mixotrophic.
| Generalists | Protists that retain chloroplasts and rarely other organelles from many algal taxa | Most oligotrich ciliates that retain plastidsa | ||||
| Specialists | 1. Protists that retain chloroplasts and sometimes other organelles from one algal species or very closely related algal species | Dinophysis acuminata | Dinophysis spp. Myrionecta rubra | |||
| 2. Protists or zooplankton with algal endosymbionts of only one algal species or very closely related algal species | Noctiluca scintillans | with algal Most mixotrophic Rhizaria (Acantharea, Polycystinea, and Foraminifera) Green Noctiluca scintillans | ||||
| aChloroplast (or plastid) retention = sequestration = enslavement. Some plastid-retaining species also retain other organelles and prey cytoplasm. | ||||||
Dinoflagellates have long whip-like structures called Flagellum that allow them to move freely throughout the water column. They are mainly marine but can also be found in freshwater environments. Combinations of phototrophy and phagotrophy allow organisms to supplement their inorganic nutrient uptake This means an increased Trophic level transfer to higher levels in food web compared to the traditional food web.
Mixotrophic dinoflagellates have the ability to thrive in changing ocean environments, resulting in shifts in red tide phenomenon and paralytic shellfish poisoning. It is unknown as to how many species of dinoflagellates have mixotrophic capabilities, as this is a relatively new feeding-mechanism discovery.
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