Recurrent outbreaks of disease in sea urchins Strongylocentrotus droebachiensis in Nova Scotia:evidence for a link with large-scale meteorologic and oceanographic events

Recurrent outbreaks of a disease (paramoebiasis, caused by a marine amoeba Paramoeba invaclens) result in mass mortalit~es of sea urchins Strongylocentrotus droebachjensis in the rocky subtidal zone of the Atlantic coast of Nova Scotia (Canada).Recent epizootics in 1993 and 1995, l ~k e those which occurred in the early 1980s, were associated with unusually warm sea surface temperatures (SST) in late summer/fall of each year Disease outbreaks were localized in 1993 and d.id not completely eliminate sea urchin populations, whereas a w~despread epizootic caused near-complete mortality over -130 km of coast (straight-llne d~stance) In 1995.lnteranr~ual differences in the extent of mortality were related to d~fferences in the temperature regime [peak tenlpcrdtures prevailed longer in 1995), which is consistent wlth previously descnbeci patterns The absence of mortality in 1994 is attributed to the inability of P invadens to survlve low (