Alkane composition of the microlayer in Corpus Christi Bay: Implications of HAB formation

Short-chain n-alkanes (n-pentadecane, n-heptadecane, and n-nonadecane) stem primarily from algae. Long-chain n-alkanes (n-heptacosane, n-noncosane, and n-hentriacontane) originate from terrigenous/land plants and are introduced to coastal waters by runoff. Since alkanes are hydrophobic compounds, they tend to concentrate in the microlayer (air-water interface). This study strives to ascertain the efficacy of using the aquatic-terrigenous ratio (ATR) as a precursor to harmful algal bloom (HAB) formation. Since the ATR is a new HAB parameter, it may further our understanding of HAB formation. Corpus Christi Bay microlayer samples have been collected via the glass plate method. Although algal and terrigenous n-alkanes have been detected in these samples using a gas chromatography-mass spectrometry (GC-MS), they are present in lower concentrations than expected. As a result, new microlayer samples are currently being collected at larger volumes to increase their n-alkane concentrations. Once adequate concentrations have been achieved, ATRs will be calculated in order to establish a range in baseline values for Corpus Christi Bay. ATR values are expected to increase prior to and during HAB events.