Milad Pourdanandeh Hosseini

Om Milad Pourdanandeh Hosseini

Who am I?

I work as a PhD candidate in the Signals in the Sea working group (pelagial.se), with Erik Selander as supervisor.

I am broadly interested in ecology and ecophysiology, especially in aquatic environments, but also biostatistics, experimental design and science communication.

Twitter/X: @pour__Milad

LinkedIn

Research:

My research focuses on phytoplankton responses to chemical cues released by copepods, called copepodamides, and the consequences of these responses at individual to ecosystem scales.

Copepods, and their chemical scent, have been shown to induce a wide variety of different defensive mechanism. They induce toxin production in harmful algae, bioluminescence (svenska: mareld), shortening of chain forming diatom colonies, altered swimming behaviour in motile dinoflagellates and changes in the diel feeding behaviour of marine protists.

Projects:

• Copepodamides in freshwater copepods, compared to in marine copepods https://doi.org/mf4s
  • We have previously found bioactive copepodamides (i.e., capable of inducing physiological and/or behavioral effects in phytoplankton and protists) in almost all studies of herbivorous/omnivorous marine copepods, the exception being a purely carnivorous copepod (Paraeuchaeta norvegica) which almost exclusively contained only the copepodamide scaffold. However, it has been unknown how prevalent copepodamides are in freshwater copepods and if these differ in chemical composition compared to marine copepods.
  • Here we formally show, for the first time, that also freshwater copepods seem to universally contain copepodamides, and in similar amounts as in similarly sized marine copepods. Interestingly, freshwater copepods almost exclusively contained one of the two sub-groups of copepodamides (the dihydro-copepodamides), unlike marine copepods which have a species specific mix of the two groups.

• Drivers of toxin production in harmful algae (in prep, soon to be submitted)
  • I am currently finishing up a meta-analysis on the relative induction effects of top-down (grazing pressure) and bottom-up (nutrient availability of nitrogen and phosphorous) on toxin production in two important genera of harmful microalgae (Alexandrium & Pseudo-nitzschia).

• The effects of copepod chemicals cues on DSP-causing microalgae (in prep)
  • Copepod chemical cues have been shown to induce toxins in a variety of marine algae, but we do not know if this is also the case for the toxic dinoflagellate Dinophysis sp. which produce diarrhetic shellfish toxins that affect marine organisms and cause diarrhetic shellfish poisoning in humans. Here, we induced cultures of two species of Dinophysis to three concentrations of copepodamides and one live grazing copepod treatment.

• Costs of toxicity and bioluminescence in marine dinoflagellates (planned, partially piloted)
  • Toxin production and bioluminescence in marine dinoflagellates have been shown to, at least partly) be due to grazing pressure from zooplankton such as copepods. These responses are predicted to have an inherent energy cost, which we will attempt to quantify in terms of growth.

• The effect of copepod chemical cues on thecal plates of dinoflagellates (planned)
  • Thecal plates of dinoflagellates in laboratory cultures have been described as "thin" and "weak" by some dinoflagellate taxonomists, compared to cells found in nature. We will study if this is a plastic response to the lack of grazing, and if exposure to grazing pressure from copepods and/or their chemical cues can trigger the cells to reinforce their thecal plates and make them thicker.

• Method development for fragile dinoflagellates (planned, pilot to begin shortly)
  • When we want to expose cultures to several pulses of copepodamides over time, usually to create an environment with more stable copepodamide concentrations, we cannot simply add the compounds to the medium directly, because they are dissolved in methanol and would poison our algae. We therefore coat a new culture vessel with the compounds (dissolved in methanol), evaporate the methanol (either by itself or by flushing it with nitrogen gas), and finally decant the culture into the newly coated vessel. However, several species of dinoflagellates seem to be very sensitive to the decantation, affecting their growth. I will therefore investigate new methods of repeatedly exposing cells to copepodamides in the same vial/flask. The general idea is to instead coat the compounds onto a glass rod/plate, which is attached/suspended from the vessel cap. This would enable us to expose the cultures to new pulses of copepodamides without disturbing the cells as much as we do now.

• Revealing the drivers of harmful algal blooms - Does trophic cascades due to copepod predation by the invasive Americans comb jelly reduce harmful algal blooms? (planned, but potentially a pipe dream).