This dataset, consisting of 3 separate files, provides the basis for our manuscript entitled "Saxitoxin and tetrodotoxin bioavailability increases in future oceans". Each file contains the data for one figure. For detailed calculation methods please refer to the method and supplementary information sections of the associated manuscript. Fig1_STX_and_TTX_pH-availability contains abundance data of saxitoxin (STX) and tetrodotoxin (TTX) protonation states across the pH range from 6 to 10 at 3 different temperatures. It is calculated based on published pKa data using the Henderson-Hasselbalch equation. Temperature is taken into account employing a pKa-influencing factor of -0.2/+10C.Fig2_Dinos_HAEDAT_STX_concatenated contains all the information required for plotting the pH and temperature dependent global toxicity map. It combines georeferenced records for localities with STX-related HABs (extracted from the Harmful Algal Information System metadatabase - HAEDAT) and the distribution of two dinoflagellate genera, which are known to produce STX, Gymnodinium and Alexandrium (extracted from the NOAA COPEPOD database). For each location we also extracted current and future pH and sea surface temperature from the Global marine environment dataset (GMED)/ IPCC (WCRP CMIP3) multi-model database. We calculated the abundance of the toxic STX form based on the pH and temperature for each of the respective locations in current and future conditions. Fig3_STXinClamTissue contains the compiled total STX content in clam tissue data from the PSP Program website of the Quagan Tayagungin Tribe for the time frame between June 2012 and July 2018 for each month at Spit Beach, Sand Point (Alaska). Based on this data we further calculated the current and future toxic proportion of this total STX content for the location's specific current and future temperature and pH data.

Supplement to: Roggatz, Christina C; Fletcher, Nichola; Benoit, David M; Algar, Adam C; Doroff, Angela; Wright, Bruce; Wollenberg Valero, Katharina C; Hardege, Jörg D (2019): Saxitoxin and tetrodotoxin bioavailability increases in future oceans. Nature Climate Change