Mass Stranding of Marine Birds Caused by a Surfactant-Producing Red Tide

In November-December 2007 a widespread seabird mortality event occurred in Monterey Bay, California, USA, coincident with a massive red tide caused by the dinoflagellate Akashiwo sanguinea. Affected birds had a slimy yellow-green material on their feathers, which were saturated with water, and they were severely hypothermic. We determined that foam containing surfactant-like proteins, derived from organic matter of the red tide, coated their feathers and neutralized natural water repellency and insulation. No evidence of exposure to petroleum or other oils or biotoxins were found. This is the first documented case of its kind, but previous similar events may have gone undetected. The frequency and amplitude of red tides have increased in Monterey Bay since 2004, suggesting that impacts on wintering marine birds may continue or increase

Correspondence between the spatial and temporal patterns of seabird strandings and red tide during November-December 2007 in Monterey Bay.

<p>Black circles represent the approximate location and magnitude of morbidity and mortality, and satellite data represent the red tide for panels (A–C). Three pulses of seabird stranding were observed: A) focused along the northern bay, B) focused in the south-central portion of the bay, and C) in both northern and central portions of the bay. In (A) and (B) the MERIS data indicate extreme bloom conditions above MCI level of ∼0.3. Although ideal for red tide detection, MERIS coverage was not adequate for the third pulse. In (C) the reddish discoloration on the MODIS true color image during the third pulse (28 Nov) shows the spatial extent and location of the red tide. Panels (D) and (E) show increased seabird stranding during the November–December 2007 red tide event. Light bars are 10-year average (1997–2006) standardized monthly stranding counts on nine Monterey Bay beaches. Dark bars are 2007 counts for western/Clark's grebes and Northern fulmar, the species most affected during the mass-stranding event. Panel (D) corresponds to the first stranding event, while panel (E) corresponds to the second and third waves of strandings.</p

Natural and laboratory produced wetting of normal feathers.

<p>A) Normal breast feather from a brown pelican after dipping in clean seawater. Note the minimal wetting and matting of feather barbs. B) Normal seawater after agitation for 30 seconds, then resting for 2 hours. Note the absence of surface foam. C) Normal-appearing breast feathers from a Northern fulmar after dipping in the test tube containing normal seawater. D) Normal breast feather from a brown pelican after dipping in surface foam collected near an <i>A. sanguinea</i> bloom in Monterey Bay. Contact with the foam resulted in severe wetting and matting of feather barbs. E) Senescent laboratory culture of <i>A. sanguinea</i> after agitation for 30 seconds, then resting for 2 hours. Note the persistence of a thick surface layer of foam. F) Normal breast feathers from a Northern fulmar after dipping in the surface foam derived from the senescent <i>A. sanguinea</i> culture, resulting in severe wetting and matting of feather barbs.</p

Observations of chlorophyll, fluorescence, phytoplankton species composition, and occurrence of foam and red tide patches were available from a series of stations in Monterey Bay.

<p>Solid symbols (dashed line) represent total chlorophyll collected weekly from the Santa Cruz Municipal Wharf from August 15 to December 15, 2007 (labelled SCW on the inset map); the solid line represents daily chlorophyll fluorescence data for the same time period from the M0 mooring. Red bars along the x-axis denote visual observations of red tides from stations depicted in the map (inset), with the letters above the red bars denoting dominant species (C = <i>Ceratium</i> spp., Co = <i>Cochlodinium</i> spp., A = <i>Akashiwo sanguinea</i>). Green bars denote visual observation of foam at the Santa Cruz Municipal Wharf. The bird strandings coincided with the largest red tides (note the chlorophyll and fluorescence) dominated exclusively by <i>A. sanguinea</i> and co-occuring with foam.</p

Aerial photograph taken 26 November, 2007 off Pajaro Dunes Colony (rectangular inset) in central Monterey Bay.

<p>A dense front of red tide is visible in the left foreground. A distinct line of surface foam is spatially associated with the red tide, along with aggregations of marine birds. Circular inset: a single non-senescent <i>Akashiwo sanguinea</i> cell.</p