Loop Current Induced Zooplankton Dynamics in the Northern Gulf of Mexico

Abstract

In the northern Gulf of Mexico (GoM), quantitative research on the spatial and temporal relationships between zooplankton and oceanographic processes currently remains insufficient but needed to understand the impacts of shifts in zooplankton communities on ecosystem dynamics and fisheries production in terms of changing environmental conditions of the Loop Current (LC) circulation and Mississippi River plume. In this dissertation, I attempt to fill the current gap of knowledge to assist in the development of effective management strategies of marine living resources. Zooplankton were collected during spring and summer from 2015 to 2017 in the northern GoM. In Chapter 2, I investigated the LC induced impacts on chaetognath distribution and abundance in the northern GoM and found species-specific relationships with environmental drivers mainly related to the LC position. In Chapter 3, I extended the investigation to the entire zooplankton community and found that zooplankton assemblages and environmental conditions varied seasonally in response to shifts in the LC circulation and the Mississippi River. In Chapter 4, I found that variations in zooplankton synchrony were uncorrelated with hydrological or geographical distances, but overall, the zooplankton diversity was significantly associated with the geographic distance. The low synchrony indicates the complexity of the Moran effect in the GoM, and implies that mesoscale processes induced effects were not the main synchronizing mechanism, but regional processes likely play a key role in driving the zooplankton spatial dynamics in the northern GoM. This dissertation contributes to the growing body of knowledge on the impacts of environmental and spatial variability to the zooplankton community in the GoM to gain a better understanding of how communities are interacting within the GoM, especially given the projected impacts of climate change. Since zooplankton act as key indicators of shifts in environmental variability, understanding the impacts of oceanographic processes on their abundance and diversity is critical for projecting shifts in mesoscale processes over time, as well as to understand how these shifts impact trophic dynamics in marine ecosystems.