|Hetzer, Paul - UNIV OF MD, CBL|
|Brown, Steve - UNIV OF MD, CBL|
|Baker, Joel - UNIV OF MD, CBL|
Submitted to: SETAC Conference
Publication Type: Abstract Only
Publication Acceptance Date: November 14, 1999
Publication Date: N/A
Technical Abstract: Outdoor agricultural plots were planted with two fresh-market tomato cultivation methods; (1) raised-bed plasticulture, and (2) raised-bed organic mulch. Four estuarine organisms: the copepod Eurytemore affinis, the amphipod Leptochierus plumulosus, the hard clam Mercenaria mercenaria, and the diatom Thalassiosira psuedonana were studied. Toxicity to all four organisms was significantly higher in runoff water and sediments from the plasticulture plots compared to those from the vetch plots. Water and sediment runoff collected over the 1998 growing season were examined to determine if agrochemical concentrations were sufficient to cause toxicity seen in the bioassays. Concentrations of target analytes (endosulfan I and II, endosulfan sulfate, fenvalerate, esfenvalerate, chlorothalonil, metribuzin, and copper) were quantified in water (dissolved), and sediment samples were collected on site to determine if agrochemical concentrations were sufficient to cause the observed toxicity. To explore the relationshi between observed toxicity and measured pesticide concentrations, LC50s and EC50s were developed in the laboratory for the individual chemicals. Two organisms, the copepod, Eurytemora affinis and the centric diatom, Thalassiosira psuedonana, were used in serial dilution toxicity tests. LC50s ranged from 3.7 ug/L for the insecticide fenvalerate, to 22.7 mg/L for the herbicide metribuzin for juvenile copepods, and 6.6 ug/L for the insecticide endosulfan to 48.2 mg/L for the herbicide metribuzin for the adult copepods. EC50s ranged from a 39.0 ng/L for diatoms exposed to copper to a high of > 0.1 mg/L when the diatoms were exposed to mixture of the insecticides and endosulfan I and II.