Award: OCE-1760509

The overarching major scientific goal of this collaborative project was to discern impacts of a major storm event (Hurricane Harvey) on carbon cycling, community metabolism, and phytoplankton community composition. The effort comprised an examination of post-hurricane conditions in the northern Gulf of Mexico following Hurricane Harvey and comparison to available pre- and post-hurricane observations related to carbon and nutrient cycles, metabolic balance, ocean acidification and phytoplankton biomass and community composition. The specific goals of this PI?s portion of the project were the following: 1. To utilize a combination of satellite ocean color and ship-based observations to characterize regional patterns in carbon properties and phytoplankton biomass and community composition associated with the passage of Hurricane Harvey. 2. To examine and compare these new observations with data acquired prior to the storm and during similar times of the year from past studies in the same region. 3. To examine analogous sets of observations acquired after hurricanes Katrina and Rita in the same region of the northern Gulf of Mexico. Total chlorophyll a concentrations as determined using High Pressure Liquid Chromatography (HPLC) were relatively higher for mid-shelf and offshore stations during Sep/Oct 2017 (post-storm) as compared to a previous cruise in July 2009. This was a possible indication of storm-induced enhancement of phytoplankton productivity in shelf waters. An examination of the phytoplankton size class fraction for microplankton based on the Uitz et al. (2006) algorithm during Sep/Oct 2017 similarly revealed higher fractions of microplankton near the river outflow regions, but also extending along the inner shelf. This same general pattern was evident during July 2009, although the higher microplankton fractions extended over a wider area during Sep/Oct 2017. A comparison of pre- (Aug 13-21) and post-storm (Aug 28 - Sep 5) satellite observations revealed a more extensive region of high chlorophyll in the area corresponding to the storm track. This pattern was also evident for the pre- and post-storm and cruise period microplankton fractions, with a more extensive area of higher microplankton fractions in the vicinity of the storm track during the post-storm and cruise periods compared to the pre-storm conditions. The results from this effort demonstrated a significant impact of Hurricane Harvey on chlorophyll concentrations and phytoplankton community composition when comparing pre- and post-storm conditions. Such changes likely have consequences for carbon and nutrient cycling and ongoing efforts with collaborators will provide a more detailed assessment of this. Last Modified: 02/12/2019 Submitted by: Steven E Lohrenz