Association of an Unusual Marine Mammal Mortality Event With Pseudo-Nitzschia Spp. Blooms Along the Southern California Coastline

Abstract

ABSTRACT:During 2002, 2,239 marine mammals stranded in southern California. This unusual marine mammal stranding event was clustered from April to June and consisted primarily of California sea lions (Zalophus californianus) and long-beaked common dolphins (Delphinus capensis) with severe neurologic signs. Intoxication with domoic acid (DA), a marine neurotoxin produced during seasonal blooms of Pseudo-nitzschia spp., was suspected. Definitively linking harmful algal blooms to large-scale marine mammal mortalities presents a substantial challenge, as does determining the geographic extent, species composition, and potential population impacts of marine mammal die-offs. For this reason, time series cross-correlation analysis was performed to test the temporal correlations of Pseudo-nitzschia blooms with strandings occurring along the southern California coastline. Temporal correlations were identified between strandings and blooms for California sea lions, long-beaked common dolphins, and short-beaked common dolphins (Delphinus delphis). Similar correlations were identified for bottlenose dolphins (Tursiops truncatus) and gray whales (Eschrichtius robustus), but small sample sizes for these species made associations more speculative. The timing of the blooms and strandings of marine mammals suggested that both inshore and offshore foraging species were affected and that marine biotoxin programs should include offshore monitoring sites. In addition, California sea lionstrandings appear to be a very sensitive indicator of DA in the marine environment, and their monitoring should be included in public health surveillance plans.

Year-round algal toxin exposure in free-ranging sea lions

“…In this and previous studies (Goldstein et al 2008, Torres de la Riva et al 2009), sea lions appear to act as indicators of offshore blooms, such as those occurring in the Juan de Fuca Eddy, before they are apparent in the nearshore waters. Past studies have found evidence for both co-occurrence of HAB toxins in marine mammals and in bivalves (Doucette et al 2006, Lefebvre et al 2010) and for a lack of correlation between the 2 (Scholin et al 2000).…”

Complexity of domoic acid-related sea lion strandings in Monterey Bay, California: foraging patterns, climate events, and toxic blooms

“…In contrast, waters were more productive and intense blooms of toxic Pseudo-nitzschia were occurring off southern California (Goericke et al 2004, 2005, Langlois 2004, 2005, Peterson et al 2006, Schnetzer et al 2007). More than 1000 sea lions were stranded in the south due to DA-related toxicity (Schnetzer et al 2007, de la Riva et al 2009), where toxic Pseudo-nitzschia blooms occurred during this period. Between summer 2004 and 2007 toxic Pseudonitzschia populations appeared to be suppressed along the central coast, and therefore DA-related CSL stranding events were unlikely and, indeed, occurred very infrequently (Table 1).…”

Clinical signs and histopathology associated with domoic acid poisoning in northern fur seals (Callorhinus ursinus) and comparison of toxin detection methods

“…Cetacean mortality, especially of common dolphins (Delphinus spp.) in southern California in 2002, has been temporally associated with DA producing Pseudo-nitzschia blooms (Torres de la Riva et al, 2009). Domoic acid exposure has also been associated with mortality and risk of development of cardiomyopathy in southern sea otters (Enhydra lutris) (Kreuder et al, 2003).…”