What stress sequence kills: different sequences of cold and freshening stress with varying latency periods and mortality of Tigriopus californicus copepodids
Date
2023
Authors
Krohman, Rebecca
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Abstract
Anthropogenic activities are increasing the number of extreme events in nature prompting researchers to study how multiple stressors impact animals. Currently, few studies have researched sequential stressors. However, in nature, stressors generally act one after another making sequential stressor studies increasingly more important to properly inform management practices. Responses of animals can change when stressors are applied in different sequences and with different amounts of time in benign conditions (latency time) between stressors. I test how mortality changes with different sequences of 12-hour cold (-15 °C change) and freshening (34% salinity of seawater) stress with three latency periods of 0, 12, and 24 hours. I use a model organism without laboratory rearing for physiology, Tigriopus californicus, which is an abundant harpacticoid copepod found in high intertidal splash pools. I find that hypo-salinity has a more severe effect than cooling disturbance and that stress sequence changes the mortality of T. californicus. In particular, there was high fatality in stress sequences that included freshening while individuals survived better in sequences that only had cold stress. The low recovery in hyposaline water shows that T. californicus had a poor capacity to osmo-regulate in 12 ppt hypoosmotic surroundings while the low mortality observed following cold stress indicates individuals were adapted for temperatures below freezing. Furthermore, there was a positive relationship between survival and latency time when hypoosmotic conditions were applied before low temperature stress showing that exposure to hypoosmotic extremes increases the ability of T. californicus to withstand cold. My results support the hypothesis that the sequence of extreme events and timing between stressors may change whether an organism lives or dies. This research adds to studies of multiple stressors and can be important for reference to future studies investigating sequence effects.