GALVÁN, K.: BARGU, S.; WHITE, J.R.; LI, C.; SULLIVAN, M., and WEEKS, E., 2012. The effects of two consecutive hurricanes on basal food resources in a shallow coastal lagoon in Louisiana.

Short-term effects of two consecutive hurricanes on physical, chemical, and biological factors were examined in a Louisiana coastal lagoon (Bay Champagne) with a focus on effects to basal food resources. Hurricanes Gustav and Ike made landfall on Louisiana's coast on 1 and 13 September 2008, respectively. Water column and sediment chlorophyll a (Chl a), phytoplankton, and benthic microalgal (BMA) community composition, phytoplankton toxin production, sediment organic matter (SOM), sand ∶ mud ratio, and water column nutrients were measured at one prehurricane and three posthurricane sampling dates. Additional samples were taken 1 year later to address relative long-term effects on sediment characteristics. After Hurricane Gustav, the sand ∶ mud ratio of sediment significantly increased, whereas SOM and water depth decreased likely because of sediment transport of the beach and nearshore sands. This continued after the storm because of multiple breaches in the beach. Water column Chl a decreased over time; sediment Chl a did not significantly change. Phytoplanktonic diatoms increased in sediments after hurricanes relative to benthic assemblages, resulting in a BMA community more closely resembling the water-column phytoplankton community. The sand ∶ mud ratio remained high for most stations, whereas SOM decreased after Gustav and remained low 1 year after the hurricanes. Thus, sediment nutritional quality decreased with decreases in SOM and reduced BMA species; however, phytoplankton may have replaced BMA as a food resource within sediments. Additionally, the abundance of phytoplankton in the domoic acid (DA)–producing genus Pseudo-nitzschia increased in the water column and benthos after the hurricanes, and particulate DA increased significantly in the water samples. Our results suggest that hurricanes substantially affect food resources (e.g., phytoplankton, BMA, and SOM) on Louisiana's coast, and posthurricane production of DA, in this case, could increase ecosystem stress during recovery. To our knowledge, this is the first study to address the effects of hurricanes on DA concentrations.