SS3.15 Physical Forcing and Pelagic-Benthic Interactions in Aquatic Systems
Date: Thursday, June 13, 2002
Time: 11:00:00 AM
Location: Oak Bay
 
BolenderJP, Chemistry Dept., University of San Diego, 5998 Alcala Park, San Diego, CA, USA, bolender@sandiego.edu
Boudrias, M, A, Marine & Environmental Studies, University of San Diego, 5998 Alcala Park, San Diego, CA, USA, boum@sandiego.edu
 
EFFECTS OF ORGANIC LOADING ON SANDY BEACHES IN BAHIA MAGDALENA I: NUTRIENTS, SEDIMENT SULFIDE, & HEAVY METALS
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The dumping of fish waste from a cannery onto beaches in Bahia Magdalena, Baja California has resulted in both abiotic and biological changes in near-shore sediments. We sampled the sediments and overlying water at five sites, four along a gradient from the cannery to a distance of 6.5 km south and at a control site 6 km across the bay. Sites were sampled with the cannery in three different operational modes (closed, fully operational, clean up). Nitrate and phosphate concentrations showed a decreasing trend from the cannery, with values 100 times background, to sites further south. The control site across the bay had nitrate and phosphate concentrations approaching 0 mg/l. Sediment sulfide concentrations were highest at a site 1 km south of the cannery and correlated to high levels of sulfur-philic surface bacteria. Pore water heavy metals concentrations from a previous study showed lead concentrations close to 1000 times expected background values. The effluent from the cannery is clearly affecting the surface water and sediments of the bay but in a restricted zone within a kilometer from the point source.