Mass Stranding of Marine Birds Caused by a Surfactant Producing Red Tide
Finding out the effects that harmful algal blooms (HABs) have on the surrounding environment and organisms will prove crucial to gaining a better understanding of the dynamics of microbial communities.
HABs are caused by a wide variety of dinoflagellates that occur worldwide. HABs can cause morbidity and mortality of fish, invertebrates, marine birds, marine mammals, and humans. The most prevalent form of morbidity and mortality in marine organisms results from direct ingestion, inhalation, or absorption of toxins. One case involved an external coating of birds by a foam derived from a red tide bloom, which occurred in November 2007 in Monterey Bay, California. Monterey Bay is an important foraging and molting area for a diversity of migratory birds. This was the first documented case where a nontoxic red tide bloom caused unprecedented beach stranding of live and dead seabirds.
Effects of HABs on Seabirds in Monterey Bay:
Fourteen seabird species were affected during the 2007 red tide in Monterey Bay. It impacted birds that feed in near shore habitat, such as surf scoters (Melanitta perspicillata). Some of the seabird species had just completed their southward migration and thus were in poor nutritional condition, which compounded their exposure to the red tide. A total of 550 birds were stranded alive and 207 birds were dead when collected during this event.
Live birds were severely hypothermic (very low body temperature), wet and hypoglycaemic (low level of blood glucose), with variable patches of a slimy pale yellow-green material on their feathers. Freshly stranded birds had a pungent odor similar to that of linseed oil while still wet, but with time, this material dried, leaving a fine, pale yellow crust with minimal smell. However, upon rinsing, rehydration, warming, and nutritional supplementation, the majority of birds regained body mass and recovered and were subsequently released.
Postmortem examinations were conducted on 283 birds from the event, including animals that were found dead and those that died during rehabilitation. Interestingly, the majority of the deceased birds were only in fair or poor nutritional condition. However, microscopic examination of the tissues revealed that approximately half of the birds had gross evidence of acute hemorrhage into the pulmonary parabronchi (the bird respiratory system).
Correspondence between seabird stranding and redtide during November-December 2007
During autumn 2007, there were a series of dinoflagellate blooms, including several red tides, culminating in the large scale November seabird mortality event. The plankton samples that were collected at various points in Monterey Bay during 2007 were dominated by the autotrophic dinoflagellate Akashiwo sanguinea. Akashiwo sanguinea's blooms have been previously linked to coral bleaching and is known to produce large quantities of amino acids that are water-soluble and serve as powerful surfactants.
The affected seabirds were observed swimming in the thick foam near the shoreline. When the seabird feathers' came into contact with the thick foam, the contour feathers lost their water repellency and became soaked. Analysis of the surface foam and feathers from affected birds coated with the yellow-green proteinaceous material revealed high concentrations of the same 616 m/z protein dimer, but seawater collected from unaffected areas did not contain this compound.
Monterey Bay's influence on red tide occurrence:
Northeastern Monterey Bay has previously been identified as a ‘‘red tide incubator’’. Monterey Bay is an incubator region because there is relatively weak ocean circulation, which means the red tide stays longer inside the bay .The bloom was detected by satellite before the harmful effects on marine birds were detected. There is also the possibility that there have been previous high-seabird mortality events caused by the red-tide that have gone unnoticed.
Prediction of the harmful effects of algal blooms requires a better understanding of linkages between climate variability, phytoplankton blooms and natural history of higher animals. It remains to be seen whether the combination of events we describe for 2007 is a result of climate change, but the frequency, amplitude and duration of ‘‘red tides’’ have increased substantially within Monterey Bay since 2004 and continue to increase globally, suggesting that the harmful effects of dinoflagellate blooms may become more common.
This describes the type of biological feature we would like to be able to track, monitor, and understand using a "Lagrangian Observatory".
The information above is from the following reference:
Jessup, D.A., M.A. Miller, J.P. Ryan, H.M. Nevis, H. Kerkering, A. Mekebri, D.B. Crane, T.A. Johnson, and R.M. Kudela (2009). Mass stranding of marine birds caused by a surfactant-producing red tide. PLoS One, 4(2): doi:10.1371/journal.pone.0004550.