Local biodiversity trends over time are likely to be decoupled from global trends, as local processes may compensate or counteract global change. We analyze 161 long-term biological time series (15-91 years) collected across Europe, using a comprehensive dataset comprising 6,200 marine, freshwater and terrestrial taxa. We test whether (i) local long-term biodiversity trends are consistent among biogeoregions, realms and taxonomic groups, and (ii) changes in biodiversity correlate with regional climate and local conditions. Our results reveal that local trends of abundance, richness and diversity differ among biogeoregions, realms and taxonomic groups, demonstrating that biodiversity changes at local scale are often complex and cannot be easily generalized. However, we find increases in richness and abundance with increasing temperature and naturalness as well as a clear spatial pattern in changes in community composition (i.e. temporal taxonomic turnover) in most biogeoregions of Northern and Eastern Europe.

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Production of European flat oysters Ostrea edulis in the Netherlands has been hampered by the presence of the haplosporidian parasite Bonamia ostreae, which is now an enzootic species following its establishment after 1980. We analyzed histopathological data from annual shellfish disease monitoring from 1988 to 2006 to quantify prevalence of B. ostreae in flat oyster stocks of the marine Lake Grevelingen. In addition, we estimated prevalence of B. ostreae on a monthly basis with field surveys in 2003. The parasite was detected with PCR, using specific primers for B. ostreae. Prevalence of B. ostreae was analyzed relative to O. edulis density, biomass and a range of environmental parameters. B. ostreae was detected in flat oysters throughout the year with a higher prevalence in spring than in autumn, possibly due to termination of spawning and the onset of oyster growth in autumn. Although B. ostreae was detected in all oyster weight classes, prevalence was highest in the largest oysters in spring and declined disproportionately in autumn, possibly due to high mortality of large oysters before autumn, suggesting that prevalence depends on oyster age. Parasite prevalence was independent of oyster density and total biomass, but appeared to be higher after a warm autumn. Abundance of the flat oyster (infected or non-infected with B. ostreae) was negatively related to the temperature of the preceding period, suggesting that mortality in flat oysters increased at higher water temperatures. Furthermore, O. edulis appeared to be more susceptible to B. ostreae after years with lower food availability and lower salinities (< 29.5). B. ostreae may weaken the competitive ability of O. edulis relative to the introduced Pacific oyster Crassostrea gigas, particularly in years with high water temperatures.

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