The collaborative project team consisting of the Robinson and Stauffer labs at UL Lafayette, the Schnetzer lab at NCSU, and the Geist lab at TAMU-CC completed 3 research cruises on the TX-LA shelf in the northern Gulf of Mexico in the 6 months following Hurricane Harvey in 2017-2018. During the cruises samples were collected at 10 stations to characterize the plankton communities ranging from the smallest (pico- and nanoplankton) through larval fish that comprise the ichthyoplankton (Fig. 1). The team was successful in documenting how plankton communities and food webs changed in the coastal ocean off Texas following Hurricane Harvey. Our collaborators found that at the base of the food web, biomass of the planktonic primary producers (phytoplankton) first increased and then decreased in the 3 weeks and 6 weeks following Harvey, respectively. The numerical abundance and diversity of mesozooplankton communities (organisms typically 0.02 ? 20 cm in size which consume both larger phytoplankton and microzooplankton), varied across the Texas shelf and over time following the hurricane. Post-storm, densities were highest in September and then decreased 10-fold in three weeks when sampled again in October. Mesozooplankton were consistently more abundant at stations closest to Galveston Bay and lowest in offshore waters. Temporal patterns suggest mesozooplankton may be highly resilient to hurricanes, with community structure only altered for a few weeks after a storm.

Larval stages of fish were the research focus in the Geist lab to understand if and how these were responding to direct and indirect effects of the Hurricane Harvey freshwater plume. The larval stage is characterized by limited swimming capacities that affects their foraging range and escape capacity. At the same time larval stages have a high energy demand to fuel fast growth rates and development of body organs. This makes them highly susceptible to be impacted by suboptimal environmental conditions that ultimately could affect year-class strength. The spatial distribution and composition of the larval fish assemblage showed a clear distinction between families that occur closer to shore and those that are found in the blue waters further offshore. This pattern was both apparent in samples from the four cruises analyzed for this project (3 and 6 weeks, Fig.2; 4 and 6 months post Harvey), and in the NOAA SEAMAP dataset ranging back to 2000. In Fall 2017, larval fish densities were high at mid-shelf stations during the two cruises and the highest larval density was recorded for an outer shelf-station in September 2017 (Fig. 3). The expansion of low surface salinity water upon the mid-shelf may have contributed to the observed pattern by shifting spawning activity of coastal species further offshore. In terms of community composition, a strong dominance of larvae belonging to the Croaker family at near shore stations during Fall 2017 compared to historic data stood out. These high densities of Sciaenid larvae - including Atlantic croaker, Silver seatrout and Banded - drum occurred over a wide range of surface salinities between 30 and 35 (Fig. 4) and suggest that there was no negative effect on abundance in Fall 2017.

For the three mentioned Sciaenid species, diet analyses revealed that different size classes of calanoid and cyclopoid copepods were the main prey items during October 2017. This is a common diet composition for coastal marine fish larvae, suggesting the lack of a drastic effect on feeding ecology at 6 weeks post Hurricane Harvey. A surprising observation was the importance of arrowworms (Chaetognaths) in the diet of Silver seatrout larvae, which can also act as fish larvae predators themselves (Fig.5). Sciaenid larvae collected three weeks after the storm had a high frequency of empty stomachs, which hints to suboptimal prey availability, however a sampling effect may have contributed to this. The diet data are in process to be linked to our collaborator's results of mesozooplankton densities to unravel spatial differences in prey electivity of fish larvae.  

This project supported the research of one early-career faculty member (Geist), one Ph.D. student who is basing her dissertation on this research, and one other  graduate student and 16 undergraduate students and volunteers at TAMU-CC who took part in research cruises, sample processing, and data analyses. Local outreach events in and around Corpus Christ showcased the project's research to a diverse audience including high school students, families and senior citizens (Fig. 6). We presented our research to the scientific community by 7 presentations given at 5 scientific meetings from international to state level. Through this project, the PI began working with a collaborative group that is working to advance a more general framework for understanding impacts of tropical cyclones on ecosystems from the ocean to land. Currently four manuscripts are in preparation for submission to peer-reviewed journals in Summer 2020.

Last Modified: 05/15/2020
Modified by: Simon Geist