Comparison of Euphausia pacifIca ingestion rates on five different phytoplankton
Sremba, Angela L.
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The euphausiid Euphausia pacifica is a keystone zooplankton species found throughout the northern Pacific Ocean. As a primary producer, this species of zooplankton sustains life within the aquatic food web. E. pacifica rely on several different food sources including phytoplankton and other species of zooplankton to support and maintain its abundance. Different species of zooplankton and phytoplankton contain different levels of carbon essential to the health of the euphausiid. The ability to ingest different species of phytoplankton may determine not only the health of E. pacifica populations but other species that depend on them for survival as well. Feeding experiments were conducted to determine E. pacifica's ingestion rate on five different types of phytoplankton at an average phytoplankton cell concentration of 150 cells ml-1. E. pacifica ingested all the different types of phytoplankton at similar rates, at an average of 22255.41 cells ml-1 , despite the differing size phytoplankton particles found among the different species. Due to this variability in size and corresponding carbon content of the different phytoplankton particle types, the percentage of body carbon ingested by E. pacifica varied between the different types of phytoplankton. The larger species of phytoplankton allowed for a higher carbon intake. Further studies using higher concentrations of phytoplankton will be necessary to generate a feeding curve for E. pacifica ingestion rates at higher phytoplankton concentrations. Understanding the consumption of phytoplankton by E. pacifica at varying concentrations in addition to the current phytoplankton levels in the ocean allows for predictions about the current condition of the euphausiid population which can be extrapolated to the health of the oceanic ecosystem overall.