Phytoplankton spring blooms in the North Atlantic

Posted on by Angela M. Kuhn

The phytoplankton spring bloom is a massive growth marine micro-algae that occurs annually during the spring season in mid and high latitudes. The spring bloom plays an important role in feeding the marine ecosystems and determining the amount of carbon exported to the deep ocean. The onset of this event has been explained from bottom-up and top-down perspectives, with different key expectations about how seasonal fluctuations of the mixed layer affect the plankton community.

Sensitivity of phytoplankton to small changes in model variables using a Taylor decomposition method. Changes in the mixed layer depth (C) reorganize phytoplankton in the water column, but the integrated effect is negligible (black line in F). Changes in light (A, and yellow lines in F) and zooplankton (E, and blue lines in F) both have significant effects on phytoplankton prior to the spring bloom (Kuhn et al., 2015)

This project assessed whether the assumptions inherent to two contrasting hypotheses are met on a typical simple Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) ecosystem model. The model was optimized and used in idealized experiments and sensitivity analyses that isolated the effects of mixed layer fluctuations.

Our results showed that the conceptual bases of both bottom-up and top-down approaches are required to explain the process of blooming; however, neither of their bloom initiation mechanisms fully applies in the experiments.

Published by Angela M. Kuhn

I'm a biological oceanographer with interest in understanding the effects of the ocean's physical variability on the marine ecosystem at different scales. I use diverse statistical methods and numerical experiments to systematically combine information from observations, simple and complex numerical marine ecosystem models.