Data Sheet 1_Beyond warming: changes in copepod phenological timing in response to marine heatwaves before and during their blooms.pdf

As ectothermic organisms with short life cycles, they are particularly sensitive to environmental changes, because their metabolism and development are closely tied to abiotic conditions. Consequently, changes in environmental conditions, including temperature, can affect copepods and potentially lead to phenological shifts that may disrupt entire food webs.

Whilst such shifts have been linked to global warming, the specific impact of marine heatwaves (MHWs) on copepod phenology remains unclear.</p>Methods<p>We used the Helgoland Roads long-term time series (German Bight, North Sea), one of the world’s richest marine datasets, to examine changes in the phenological timing of key copepod taxa in response to MHWs. We computed yearly bloom traits using an algorithm adapted from phytoplankton bloom analyses and assessed their relationships with MHW components (i.e., mean temperature intensity, proportion of MHW days, maximum temperature decline rate and maximum temperature increase rate) both before and during the bloom.</p>Results<p>With the exception of the calanoid copepod Acartia spp., we found no evidence of consistent phenological shifts in response to MHW components occurring before the bloom.