Utilisation of seaweed carbon by three surface-associated heterotrophic protists, Stereomyxa ramosa, Nitzschia alba and Labyrinthula sp.

Abstract

In view of the abundance of protists associated with seaweeds and the diversity of nutritional strategies displayed by protists in general, the ability of 3 closely associated protists to utilise seaweed carbon was investigated. Stereomyxa ramosa, Nitzschja alba and Labyrinthula sp. were cultured with seaweed polysaccharides as well as seaweed itself. N. alba and Labyrinthula sp. were found to utilise seaweed polysaccharides in axenic culture. All 3 protists were capable of penetrating intact but 'damaged' (autoclaved) seaweed particularly when bacteria were present. The possibility that these and other heterotrophic protists are directly removing macroalgal carbon in the field is discussed.

Microphytobenthic extracellular polymeric substances (EPS) in intertidal sediments fuel both generalist and specialist EPS‐degrading bacteria

“…Heterotrophic uptake is known in benthic diatoms, though work has concentrated on small molecules, e.g., acetate, glucose, and amino acids (Admiraal et al 1987;Liu et al 2009). It is not known if diatoms secrete extracellular enzymes to degrade EPS (some diatoms are reported to be able to degrade macroalgal polysaccharides; Armstrong et al 2000). Decreases in extracellular carbohydrates in the dark in axenic diatom cultures have been reported (Smith and Underwood 2000;Staats et al 2000), and a number of species of apochlorotic diatoms, including species in the genus Nitzschia, can utilize algal polysaccharides in axenic culture (Armstrong et al 2000).…”

“…It is not known if diatoms secrete extracellular enzymes to degrade EPS (some diatoms are reported to be able to degrade macroalgal polysaccharides; Armstrong et al 2000). Decreases in extracellular carbohydrates in the dark in axenic diatom cultures have been reported (Smith and Underwood 2000;Staats et al 2000), and a number of species of apochlorotic diatoms, including species in the genus Nitzschia, can utilize algal polysaccharides in axenic culture (Armstrong et al 2000). Our experimental design does not allow us to determine whether diatoms present in the slurries were directly utilizing the 13 C-labeled N. tubicola EPS or other labeled by-products of microbial degradation of this EPS.…”

The place of diatoms in the biofuels industry

“…In the natural environment, heterotrophic diatoms can be found on macroalgae (kelp), from which they obtain their carbon [94]. Nitzschia alba is an obligate heterotroph that has lost its chloroplasts, and can grow on both simple and complex carbohydrates [94][95][96], demonstrates growth rates in the field appreciably higher than other heterotrophic protists, and doubles in 6 h when cultured in the presence of glucose [95]. The ability of diatoms to breakdown complex carbohydrates suggests possible applications with different carbon feedstocks, such as cellulose.…”

Effects of freshwater input and mariculture (bivalves and macroalgae) on spatial distribution of nanoflagellates in Sungo Bay, China

“…However, excess carbon, accounting for up to 40% of the carbon produced daily during photosynthesis, is released as DOC into the surrounding water (Sieburth 1969, Lucas et al 1981. Some protists can utilise seaweed-derived polysaccharides and other types of high-molecular-weight polysaccharides (Sherr 1988, Armstrong et al 2000, whereas bacteria are considered the main consumers of DOC, which is then transferred to higher trophic levels when bacteria are consumed as prey (i.e. by NF).…”