Colonies of P. chilensis were sampled via self-contained underwater breathing apparatus (SCUBA) diving on 14th and 15th of May 2019 at two different sites in Comau fjord. At each site, 20 colonies of a length between 20 cm and 30 cm were collected at a depth between 16 m and 20 m by cutting the terminal tips of the colonies with scissors. To determine behavioural stress, polyp activity states of Primnoella chilensis colonies and the frequency of these states were observed under turbid seawater in an experimental setup for 15 days (Treatment 1: equals sedimentation rate of 225 mm/y; Treatment 2: equals sedimentation rate of 450 mm/y; control group: ambient seawater). A visual overview analysis of colonies of Primnoella chilensis was conducted with the image-viewing program IrfanView. In a defined sector the overall colony activity was assessed and categorized: category 0 = > 50 % of polyps closed; category 1 = > 50 % of polyps semi-open; 2 = > 50 % of polyps open ; n.d. = no data. After the experiment, each coral colony was carefully blotted dry using delicate task wipers and weighed to determine the wet mass. Furthermore, the respective lengths and polyp diameter of a single, representative polyp were measured. Afterwards, they were dried for 36 h at 50 °C in a drying oven, weighed again to determine dry mass and then ashed for 24 h at 500 °C in a muffle furnace and weighed again to determine ash-free dry mass.

This dataset was generated in the frame of the co-operation between the Huinay Scientific Field Station (http://www.huinay.cl) and the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (http://www.awi.de).