Allelopathic compounds of a red tide dinoflagellate have species-specific and context-dependent impacts on phytoplankton

Abstract

The use of chemical compounds to suppress the growth of competitors is a competitive strategy known as allelopathy that can be readily observed with many phytoplankton species in laboratory studies. However, it is unclear how these allelopathic interactions are altered when the complexity of the system is increased to more closely mimic natural conditions. In the present study, we conducted laboratory experiments to decipher how the identity, abundance, and growth stage of competitors affect the outcome of allelopathic interactions with the red tide dinoflagellate Karenia brevis. Multiple chemical compounds produced by K. brevis were found to inhibit the growth of 4 phytoplankton competitors, although these competitors were susceptible to different combinations of compounds. We found that physiological state and cell concentration of competitors were important determinants of allelopathy, with early-stage (lag phase) cells more vulnerable to allelopathic effects than later growth stages for the diatom Skeletonema grethae. Despite being allelopathic to multiple competitors in the laboratory, in a microcosm experiment using plankton field assemblages, extracellular extracts of 2 strains of K. brevis had no effects on some taxa although they stimulated the growth of some diatoms. This suggests that in a species-rich ecological community under oligotrophic conditions, the relative importance of K. brevis allelopathy may not be as high as most laboratory studies predict.

Inhibitory effect of Salicornia europaea on the marine alga Skeletonema costatum

“…This was observed previously, and was reported as a fertilization effect at very low concentrations [24]. Alternatively, the extract may have had a chelating effect on some micronutrients in the culture medium [25].…”

Metabolomics and proteomics reveal impacts of chemically mediated competition on marine plankton

“…Competitor susceptibility to K. brevis allelopathy is at least partly mediated by ecological context and not all competitors are equally affected (4). The presence of particular competitor species modulates allelopathic potency (27), and competitors in earliest growth stages are most susceptible to K. brevis allelopathy (23). Allelopathic compounds produced by K. brevis cause sublethal reductions in growth and photosynthetic efficiency as well as increased cell membrane permeability (25), although the exact cellular metabolic targets of K. brevis allelopathy are unknown.…”

Effects of algicide on the growth of Microcystis flos-aquae and adsorption capacity to heavy metals

“…With the prolonged culture time, the concentration of SA in the medium will gradually decline. When the concentration of SA reduced to a certain concentration which could not inhibit algae cell growth effectively, the inhibition rate was decreased (Poulson et al 2010;Jiang et al 2010). …”