Investigating Seasonal Succession Patterns in Mesozooplankton Community Structure Following Hurricane Harvey

Abstract

The northern Gulf of Mexico (nGOM) is a highly productive region and supports some of the world’s largest fisheries. Mesozooplankton represent a key linkage in coastal food webs for larval fish, both as food and as competition. While many studies have investigated seasonal patterns of mesozooplankton off the Louisiana coast and in the Mississippi Bight, there is little information about mesozooplankton communities on the Texas shelf. In this study, we investigated environmental drivers of mesozooplankton community variability over space and time. Samples were collected on the Texas shelf near Galveston Bay at seasonal intervals following Hurricane Harvey. Total mesozooplankton abundance were found to be highest in September. Diversity exhibited a hump-shaped pattern over the 6 months sampled, with the highest diversity occurring in October 2017. Taxa richness did not vary over the sampling period. Significant differences in mesozooplankton community structure were found only between September 2017 and March 2018. Community abundance was greatest nearshore, and zooplankton diversity was greatest on the shelf. Community structure was found to be driven by both temperature and salinity. Spatial and temporal patterns of specific larval fish prey are presented.

Pico‐ and nanoplankton communities on a near to offshore transect along the continental shelf of the northwestern Gulf of Mexico in the aftermath of Hurricane Harvey

“…Additionally, attribution of changes in phytoplankton biomass or assemblage to changes in purely bottom‐up or environmental controls following a tropical cyclone may underestimate the potential for changes in grazer communities and grazing activity following such events. Increases in microzooplankton numbers (Wetz and Paerl 2008b) and time‐lagged grazing rates (Morison et al 2019) have been documented in the aftermath of storms, and recent study indicates increased mesozooplankton abundances in the nearshore waters of our study region following Hurricane Harvey (Topor et al 2020). Both microzooplankton and copepod grazing rates were quantified in October, January, and March during the same cruises and in the broader region prior to Hurricane Harvey in July, and these findings will be discussed in forthcoming papers.…”

Multi-storm analysis reveals distinct zooplankton communities following freshening of the Gulf of Mexico shelf by Hurricane Harvey

“…As energetic expressways between primary production and higher consumers, changes in the abundance and evenness of zooplankton communities impact energy transfer in coastal food webs. Large increases in coastal zooplankton abundance, like we see following Harvey 22 , can represent a flood of food resources for planktivorous consumers in the area (e.g., forage fish). Zooplankton abundance is often closely linked to larval fish recruitment success, with higher zooplankton abundances representing greater availability of prey in the water column 51 , but can also represent increased top-down control by zooplankton predating on larval fish 52 .…”

“…Each hurricane made landfall along the Texas and Louisiana coastline and were classified as ‘severe weather events’ for the Houston area by Texas A&M’s State Climatologist 30 . Zooplankton sampled after Hurricane Harvey in 2017 were collected at the established SEAMAP stations during September (21–24 Sept), and October–November (30 Oct–3 Nov) following Topor et al 22 .…”

“…Mesozooplankton were identified and enumerated following Topor et al 22 . Physical samples were homogenized in a graduated beaker using an aquarium bubbler and multiple aliquots (2 mL or 5 mL) were taken using a Henson–Stempel pipette.…”

“…Kurtay et al 20 reported decreases in overall phytoplankton biomass relative to historic levels and numerical increases of pico- and nanoplankton on the northwestern GOM shelf 2 months following Harvey. In the same area, Topor et al 22 reported higher abundances 1 month after the storm in September as well as subsequent shifts in mesozooplankton abundance and diversity relative to the 6 months following the storm. A caveat to these findings is that NWGOM zooplankton abundance is highly variable year-to-year 23 , 24 , and these results must be placed within historic context to determine if Harvey was indeed anomalous 20 , 22 .…”