A COMPLETE HOLOCENE RECORD OF TREMATODE PREVALENCE FROM THE PEARL RIVER DELTA, CHINA: IMPLICATIONS FOR GLOBAL CHANGE AND THE FUTURE OF DISEASE

There is great concern about how vector-borne diseases will respond to anthropogenic climate change in the coming centuries. Most studies addressing this problem have utilized experimental and patchy historical data over very limited temporal scales (10^-1-10³ years); however nothing is known about how diseases respond to shifting environments due to global change through deep time. Here we take advantage of a complete Holocene record of trematode prevalence from the Pearl River Delta (China) in order to examine the response of a complex multi-life stage parasite-host(s) interaction to global change on an appropriate temporal scale (10⁴-10⁵ years). We examined the two dominant bivalve taxa, Potamocorbula amurensis (n=3,984) and Cyrenodonax formosana (n=9,576) for trematode-induced malformations from a 24 m core from which 168 samples were collected. Both taxa exhibited evidence consistent with trematode infestation, but the traces are most diagnostic in P. amurensis; therefore, these data will be the sole focus of this study. Ninety-two out of 137 (67.2%) species occurrences of P. amurensis preserved trematode-induced pits, proportional prevalence values ranged from 0.011 to 0.397 in species occurrences with n≥10 valves. A highly statistically significant increase in trematode parasite prevalence occurred during the initial stages of sea level rise (~300 years) relative to subsequent transgression, delta progradation, and delta lobe switching. Elevated prevalence values have also been identified in fossil and modern marine settings in other basins. Using this early transgressive stage in the Holocene as an analog for anthropogenic climate change and sea level rise in the next few centuries, we predict stark implications for estuarine macrobenthos, seabirds, marine fisheries, and human health.