Coral Mortality and African Dust

Summary of Findings

• Synthetic organic chemical contaminants (pesticides, polyaromatic hydrocarbons [PAHs]) and polychlorinated biphenyls (PCBs) have been identified in air samples from a dust source region in the African Sahara/Sahel (Mali) and downwind sites in the US Virgin Islands (USVI; St. Croix and St. John) and Trinidad during dust conditions. Air samples from Mali contained higher concentrations of the organic contaminants than USVI and Trinidad air samples. Some are known endocrine disruptors or toxins. (Garrison, Foreman, Majewski, Mohammed, Simonich, Genualds in preparation)
  
  
• As of August 2005, preliminary identification has been made of >300 kinds of microorganisms cultured from air samples collected on St. Croix, St. John and Trinidad during dust and non-dust conditions. Air samples collected during dust events in the USVI and Trinidad contain approximately 2-3 times as many culturable microorganisms per volume as do air samples collected during non-dust conditions. Of those microorganisms identified to date, 25% are known plant pathogens and 10% are known opportunistic pathogens of humans. (Griffin, Ramsubhag, Smith, Gray in preparation; publication - Griffin et al. 2001, 2003)
  
  
• Air in Mali contains orders of magnitude more microorganisms per volume than air sampled in the downwind areas (USVI and Trinidad) and more species. Of the hundreds of microorganisms cultured and isolated from Sahara and Sahel (Mali, West Africa) air samples, DNA sequencing has been used to identify 50 types of bacteria (and 3 genera of fungi) and preliminary identifications have been made on >100 additional kinds of bacteria. Of the cultureable bacteria identified thus far, 10% are known animal pathogens, 5% are plant pathogens, and 27% are opportunistic human pathogens. (Kellogg, Smith, Coulibaly, Gray in preparation; publication - Kellogg et al., 2004)
  
  
• A pilot study found that dust collected in the USVI during African dust conditions was highly toxic to gametes and embryos of some marine organisms (Nipper, Carr, Garrison in preparation).
  
  
• The pathogenic strain of the fungus known to cause sea fan disease and mortality of sea fans throughout the Caribbean region has been isolated from:
  
  
  • lesions of diseased sea fans.
    
    
  • air samples collected in the USVI during African dust conditions but not from non-dust periods.
    
    
  • soil from the Sahel (Mali).
    
    
  • sediment from the Gulf of Paria (SE Caribbean) near the mouth of the Orinoco River. (Smith in preparation; publication - Weir-Brush et al., 2004)
    
    
• Concentrations of metals in dust aerosols at source and downwind sites are similar to the elemental composition of the earth's crust, with slight enrichment of copper and silver. (Garrison, Holmes, Lamothe in preparation).

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