Planktonic Communities and Trophic Interactions in the North Equatorial Pacific Ocean

• Main Author: Kj Hoffman
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Pacific; Ocean acidification
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.525.5500; http://stanford.sea.edu/research/Plankton Final - Kat.pdf

The complex relationships between marine planktonic trophic levels are not yet well understood, despite the importance of the plankton community in the global carbon cycle and its role as a food source for commercial fisheries. In this study, phytoplankton and zooplankton community samples were collected and identified along a transect from a Hawaiian cyclonic eddy, through the oligotrophic North Pacific gyre, to the high-nutrient equatorial ocean. Within the phytoplankton community, siliceous diatoms and dinoflagellates were found to respond differently to environmental fluctuations, with more significant correlations between nutrient availability and diatoms than dinoflagellates. Differential responses by different trophic communities were also found, with bottom-up forcings more important for phytoplankton communities and top-down influences primarily controlling zooplankton. Using the different productivities along this transect, planktonic biodiversity was correlated with resource availability. Phytoplankton, due to competitive exclusion, have higher diversity at lower productivities. Zooplankton, due to predation influences, have higher diversity at higher productivities. By tracking changes in planktonic biodiversity over time, both top-down effects from anthropogenic influences like overfishing and bottom-up forcings from nutrient runoff and ocean acidification may be revealed.