Evaluating The Impact Of The Clean Water Act On Coastal Waters Off The Southern California Bight: Temporal And Spatial Gradients In Metal Contamination In The Water Column And In Phytoplankton Website
Sergio A. Saņudo-Wilhelmy - University of Southern California
Period: 2/1/2008 - 1/1/2010
|Current Status: Completed||Last Updated: 8/18/2010|
|Federal Funds:||State Funds:|
The main goal of the proposed research is twofold: 1) to establish current levels of toxic metals in the dissolved, particulate and phytoplankton pools in the SCB and 2) to establish whether has been a reduction in those levels due to the implementation of the Clean water Act . In order to accomplish the research goals, I am proposing the following objectives:
o Establish seasonal (winter runoff versus summer upwelling) and spatial gradients in the concentrations of different metals in different pools (dissolved, particulate and in phytoplankton), including tracers of sewage (Ag), toxic (Cd, Cu, Fe, Ni, Pb) and bio-essential (Co, Fe, Mo, and Zn) metals in surface waters of the SCB.
o Establish long-term decadal changes in metals levels within the SCB by comparing the present data with those measured 30 years ago.
o Under laboratory conditions, estimate the internalization rate of toxic metals in local phytoplankton species.
To establish whether there has been a reduction in metal levels within the SCB, samples will be collected at the same locations as Ken Bruland, John Martin and Clair Patterson collected their samples in the 1970s. To facilitate this comparison, samples will be collected under winter conditions, as in those previous studies. Winter sampling will also allow us to establish how important runoff is as an influence on metal levels within the SCB. Additional samples will be collected in the summer under upwelling conditions, as this oceanographic process strongly influences metal levels in coastal waters off northern and Baja California.
Although Federal and State monitoring programs have provided extensive data on contaminants in biological tissues and sediments, there is inadequate information on the levels of toxic metals in the water column of the SCB. Therefore, it has been difficult to establish the full impact of the implementation of the Clean Water Act in this coastal environment. The information generated in this research may have tremendous implications for various coastal managerial decisions. For example, this research will help us to delimit areas impacted by toxic metals. If the current metal levels in the coastal ocean of the SCB are as low as the open ocean, should we continue spending more money upgrading sewage treatment plants? Similarly, if the levels of metal in phytoplankton are mostly in the extracellular pool, and/or metals are being internalized too slowly to produce any toxic effects, should we then re-evaluate current metal criteria standards? However, without knowing the levels of toxic metals in the water column and in phytoplankton, it is almost impossible to have a complete assessment of the contamination affecting the urban ocean of the SCB. It is to some extent unbelievable that despite the more than 175 million people visiting the beaches of Southern California every year, generating about $9 billion in ocean-related activities, levels of toxic metals in those waters are still unknown.
Publications & other print media:
Natali SM, Sañudo-Wilhelmy SA and Lerdau MT. 2009. Effects of elevated carbon dioxide and nitrogen fertilization on nitrate reductase activity in sweetgum and loblolly pine trees in two temperate forests Plant and Soil 314(1-2):197-210.
2009. Antonio Tovar-Sanchez, Carlos M. Duarte, Santiago Hernández-León. & Sergio Sañudo-Wilhemy. Impact of submarine hydrothermal vents on the metal composition of krill and its excretion products. Marine Chemistry. 113. 129-136
Natali SM, Sañudo-Wilhelmy SA, Norby RJ, Zhang H, Finzi AC and MT Lerdau. 2008. Increased mercury in forest soils under elevated carbon dioxide. Oecologia 158:343-354, DOI 10.1007/s00442-008-1135-6
Video, electronic, and computer products:
|Figure 1. Dissolved silver concentrations measured in surface waters of the Long Island Sound in April 2004. The west-east gradient is consistent with the high volumes of sewage being discharged into the western regions of the Sound (Modified from Buck et al., 2005).||Figure 2. Comparison of intra-cellular versus surface adsorbed Cd and Cu measured in field populations of phytoplankton of the tropical North Atlantic (Tovar-Sanchez and Sañudo-Wilhelmy et al., in preparation). Metal concentrations were normalized to phosphorous to eliminate variability due to different biomass in the samples. This comparison clearly shows that total metal levels do not reflect the intracellular pool.|
|Figure 3. Lead concentrations measured in the total and intracellular pool of the diatom Thalassiosira weissflogii under laboratory conditions (Sañudo-Wilhelmy et al., in preparation). While there was an increase in total metal levels 12 hours following a Pb addition of ~100 pmol, the increase was due to surface scavenging as the intracellular pool remained unchanged. In contrast to these results, a significant fraction of Cu was internalized after 12 hours (results not shown).||Figure 4. Station grid of the SCCWRP Regional Marine Monitoring Survey. I am proposing to collect samples at 50 stations within this grid. If this project is funded, the actual sampling locations will be chosen in consultation with SCCWRP scientists.|