What doesn’t kill you makes you stronger: Fear of predation widens the thermal niche of the harmful algal bloom species Phaeocystis globosa

Study Description: This study investigates how predation risk modulates the thermal tolerance of Phaeocystis globosa, a harmful algae genus. We demonstrate that grazing cues (from ciliates and copepods) enhance P. globosa colony formation and expand its thermal niche, enabling survival at higher temperatures (up to 30°C) and explaining its bloom persistence in tropical summers. Thermal performance curve (TPC) modeling revealed that predation cues increase the critical thermal maximum from <30°C to 35°C, highlighting the role of \"fear effects\" in mitigating climate-driven vulnerability., Study organisms: P. globosa was cultured in f/2 medium in the exponential stage. Ciliates and copepods were fed the green alga Dunaliella tertiolecta every 3–4 days
Grazing risk experiment: P. globosa grew alone and exposed to grazing risks from the ciliate Euplotes vannus, and the copepod Apocyclops royi were maintained at temperatures of 13, 15, 17, 21, 25, 28, and 30°C.
Solitary cell concentrations: Solitary cell concentrations were measured using Sedawick-Rafter chambers. Cells were counted in randomly selected fields of view until 300 cells were counted per replicate.
Colony abundances: Colony abundances, colony diameters, and the number of cells per colony were measured in 24-well plates using an Olympus inverted microscope. At least 30 colonies from each replicate were randomly chosen to measure colony diameters and cell numbers per colony.
Growth rates: 2 ml P. globosa samples from beakers were collected daily to measure in vivo chlorophyll fluorescence with a Turner Design..., , # Data from: What doesn’t kill you makes you stronger: Fear of predation widens the thermal niche of the harmful algal bloom species Phaeocystis globosa

[https://doi.org/10.5061/dryad.573n5tbjb](https://doi.org/10.5061/dryad.573n5tbjb)

## Description of the data and file structure

To evaluate whether non-consumptive effects alter thermal responses, *P. globosa* grown alone and those exposed to grazing cues associated with ciliates and copepods were maintained at temperatures ranging from 13°C to 30°C.  The incubations lasted for seven days. Solitary cell abundances, colony numbers, colony diameters, and cells per colony of *P. globosa* grown alone and exposed to grazing cues at different temperatures were determined. We also quantified TPCss using the equation by Thomas et al. 2012.

### Files and variables

#### File: Data\_\_Fear\_Phaecystis\_Warming\_Ye.xlsx

**Description:** This dataset contains six sets of data on predation risk on thermal traits of *Phaeocystis globosa*. We pr...,