Influence of Environmental Factors on Seasonal Variation in Plankton Dynamics in Nearshore Waters of Eastern Guangdong, China

Phytoplankton and zooplankton are critical basal resources in regulating aquatic material and energy fluxes. We investigated how environmental variables shape seasonal plankton abundance and diversity across nearshore zones in Eastern Guangdong, China. We identified 62 phytoplankton taxa (dominated by Bacillariophyceae at 88.52%) and 34 zooplankton species (dominated by calanoid copepods at 36.36%). Redundancy analysis (RDA) demonstrated that seasonal shifts in temperature, salinity, pH, dissolved oxygen, and dissolved nutrients (N, P, Si) significantly drive spatial community variability (Y ≥ 0.02). Dominant bioindicator species exhibited strong seasonal ties to environmental gradients; the diatom Skeletonema costatum strongly correlated with inorganic nitrogen during autumn, while the copepod Acartia centrura was heavily influenced by summer salinity and nutrient loads. Overall, phytoplankton diversity was higher than zooplankton diversity. These baseline findings regarding dominant copepods, diatoms, and eutrophic field parameters offer valuable insights for developing live feed alternatives in aquaculture and identifying bioactive substances for pharmaceutical applications.