High molecular weight petroleum hydrocarbons differentially affect freshwater benthic macroinvertebrate assemblages

High-molecular weight petroleum hydrocarbons (HMWPHs) are a common pollutant in urban freshwater sediments. A previous study found that HMWPHs derived from synthetic oils are detrimental to aquatic benthic macroinvertebrates at concentrations greater than 840 mg/kg, but it is unclear what effect hydrocarbons derived from other sources have on these organisms. A field-based microcosm experiment was conducted to determine whether natural and other types of HMWPHs produce similar effects on indigenous benthic macroinvertebrates as was induced by synthetic motor oils. Ordinations and comparisons of sensitive species indicated that HMWPHs from different anthropogenic sources negatively affected macroinvertebrates, whereas naturally occurring hydrocarbons above the threshold of 840 mg/kg had no detrimental effect. This result suggests that total petroleum hydrocarbon content, which is often used to identify hydrocarbon pollutants, is a good conservative indicator of HMWPH concentrations affecting the biota.