Ichthyoplankton Distribution And Assemblage Within And Around The Saco River Plume

A majority of research has focused on the importance of large river plumes for ichthyoplankton survival and recruitment. However, the impacts of smaller, more ephemeral river plumes, such as those commonly found in the Gulf of Maine, on ichthyoplankton are far less understood. The purpose of the current study was to use a small river plume located in the southern Gulf of Maine as a model system to increase our understanding of their effects on ichthyoplankton distribution and diversity, and determine what biotic and abiotic factors may be influencing any differences observed. Plankton tow sampling revealed that although ichthyoplankton abundance was highest in the ocean habitat, species diversity was lowest within this region due to the dominance of one species. Chlorophyll α concentrations and zooplankton densities did not differ between plume or ocean waters, most likely due to the ephemeral nature of the river plume. Overall, compared to larger plume systems, the Saco River plume appeared to have minimal influence in Saco Bay. However, specific events of higher river discharge may be having the greatest effect on ichthyoplankton distribution through advection offshore, as well as downwelling at the front and subsequent entrainment into plume waters