Gable, George M., IV (2007-08). Spatio-temporal patterns of biophysical parameters in a microtidal, bar-built, subtropical estuary of the Gulf of Mexico. Master's Thesis. Thesis uri icon


  • Plankton communities are influenced, in part, by water exchange with adjacent
    estuarine and oceanic ecosystems. Reduced advective transport through tidal passes or
    with adjacent bay systems can affect chemical processes and biological interactions,
    such as nutrient cycling, phytoplankton abundance and productivity, community
    respiration, and zooplankton biovolume. The most threatened estuarine ecosystems are
    shallow, bar-built, microtidal estuaries with small water volumes and restricted
    connections through tidal passes and other water exchange points.
    This research explored spatio-temporal trends in plankton communities and the
    physicochemical environment in Mesquite Bay, Texas a microtidal, bar-built,
    subtropical estuary in the Gulf of Mexico. This research couples sampling at fixedstations
    for multiple physical and biological parameters with high-resolution spatial
    mapping of physicochemical parameters.
    Spatial trends were less in magnitude and affected fewer parameters in fixed station
    and spatial data. Two dimensional ordination plots indicated spatial heterogeneity with a
    more pronounced temporal trend affecting parameters including temperature, salinity as a function of inflow timing, and seasonal wind direction affecting primary production
    and zooplankton biovolume.
    Temperature was positively correlated with gross production and respiration rates
    during spring and late summer with sporadic positive and negative correlations with
    phytoplankton biomass. The timing and magnitude of freshwater inflow affected
    various physicochemical and biological parameters. Higher than 71-year inflow rates
    resulted in low salinity system wide, with spatial heterogeneity increasing over the
    course of the study, which was confirmed by spatial maps. Additionally, high inflow
    rates led to two periods of increased inorganic nutrients and dissolved organic matter.
    Low salinity periods coincided with persistence of higher turbidity, likely because of
    decreased sediment flocculation. Gross production was low at this time, and likely from
    light limitation. Additionally, wind magnitude and direction created spatial
    heterogeneity in turbidity levels and phytoplankton biomass. Zooplankton biovolume
    was highest during spring and late summer with high species diversity in total rotifers.
    Copepod biovolume and phytoplankton biomass were positively correlated. Other
    zooplankton taxonomic groups exhibited variable correlations with phytoplankton
    biomass and other taxonomic groups. Further long-term studies are needed to determine
    interactions of various components of trophic food-webs and account for interannual
    variability in all system parameters.

publication date

  • August 2007