, 1999). Changes in oceanic conditions are still taking place, including a minor regime shift in 1989 (the year of the spill), which nonetheless had noticeable effects on various biota in the region (Hare and Mantua, 2000). In the face of all this ecosystem “noise,” it is probably impossible to discern an unambiguous signal from an oil spill that occurred more than two decades

in the past, in an area with less than 100 sea otters. The sea otter’s susceptibility to oil contamination was well known before the spill (Costa and Kooyman, 1982 and Davis et al., 1988) and accordingly, Cyclopamine supplier dire forecasts had been made in the event of an oil spill within the range of this species (VanBlaricom and Jameson, 1982). Shortly after completion of the Trans-Alaska oil pipeline, with the threat of a future spill near the terminus in PWS, studies were conducted on potential oiling effects on sea otters; this work concluded that otters could survive only light contamination

of their pelage (Siniff et al., 1982). At the time, consideration was not given to potential longer-term effects of remnant oil buried in the substrate, altered otter demography, or even what to study in the years after a spill. An event of the nature and magnitude of EVOS will inevitably lead to disagreements about the eventual short and long-term effects. In this case, scientists with differing perspectives posed questions differently, designed studies differently, Fulvestrant order and interpreted data differently, resulting in different conclusions. In part, these differences arose from different approaches to examining the situation.

One approach was to closely investigate otter abundance in relatively small but heavily-oiled sites like NKI and Herring Bay, looking for discrepancies from either a reference site or a time in the past. An alternate approach was to examine variation across a broader spatial and temporal scale, attempting to discern whether outliers corresponded with places that had significant oiling. The first approach creates more Type I errors (detecting oiling effects that are not real), whereas the latter is more prone to Type II errors (not finding oiling effects that are present). Post-spill studies of sea otters were made more difficult by the fact that potential Cyclin-dependent kinase 3 reference sites were not only ecologically different from oiled sites, but otter numbers at reference sites were changing (unexpectedly). Ecological catastrophes are messy not only in a literal sense, but also in terms of the complexity of confounding factors and difficulties in study designs (Wiens and Parker, 1995). With large background variation, control-impact studies require too many replicates to be feasible, because each site must be sufficiently large to contain a demographically meaningful population. Likewise, if the pre-event dynamics are not well understood, before–after study designs will not yield reliable results.