The influence of physicochemical factors and wind-induced resuspension on microalgal and zooplankton community assemblages in a shallow coastal embayment, South Bay, TX, USA

摘要

Plankton communities are important members of the food web in coastal systemsand are regulated by top-down and bottom-up controls. This study examined theinfluence of bottom-up controls, such as physicochemical factors, and top-downcontrols, such as predation, on the plankton communities in South Bay, Texas.Microalgal photopigments were ascertained by high-performance liquid chromatography(HPLC) to determine the relative abundances of major algal classes. Zooplankters wereidentified to the lowest possible taxon and enumerated. No spatial trends were observedfor the physicochemical factors. The northern bay sections exhibited significantlyhigher phytoplankton and microphytobenthic diatom biomass, probably due to theirproximity to the bay inlet. Copepod, gastropod veliger and brachyuran zoea abundanceswere also higher in this area, albeit insignificantly. The southern bay sectionsexperienced significantly higher cyanobacterial, euglenophyte and chlorophyte biomass,and polychaete larval abundances. Total zooplankton and nauplii abundances were alsohigher in the southern areas, albeit insignificantly. Sampling the inaccessible areas ofthe bay in the future may reveal spatial variability among the physicochemical factorswhich could be influencing the distribution of plankton. Temporal variation for thephysicochemical factors followed a typical trend for subtropical climates and influencedthe seasonality of the plankton communities. Phytoplankton biomass peaked inFebruary, August and October but these maximums were not significantly different fromthe other months sampled. Microphytobenthic biomass peaked during the summermonths, while diatom biomass also peaked in February. Zooplankton abundancespeaked in October, while nauplii and polychaete larvae also peaked in February. Relationships between wind speed, turbidity and the microalgal pigments were assessedto determine if wind-induced resuspension influenced the location of the major algalclasses within the water column compared to the sediments. Wind speed and turbiditywere directly related to each other, albeit insignificantly. Some phytoplankton andmicrophytobenthos were considered tychopelagic because wind-induced resuspensionincreased their biomass in the water column compared to the sediments. Thephysicochemical factors exerted bottom-up control of plankton community dynamics inthis study, while top-down controls, such as predation, require further investigation.Future studies should focus on which of these controls have more influence on planktoncommunity dynamics in South Bay.