Received: 01 Mar 2016 – Accepted for review: 08 Mar 2016 – Discussion started: 17 Mar 2016
Abstract. Phytoplankton growth is the foundation for energy transfer into higher trophic levels, influences climate by the uptake of atmospheric CO2, and plays an important role in nutrient cycling. Here we use a novel lagrangian approach to characterize the nitrate supply to the Great Australian Bight, identify episodes of extreme phytoplankton blooms and ascertain the origin of the nitrate sources that fuel them. We find that 55 % of nitrate used by phytoplankton enters the GAB in the upper 100 m and that 88 % originates locally from a region between the GAB and the Sub Antarctic Front, rather than from more remote oceans; thus, most of the nitrate is recycled locally. Our results show extreme phytoplankton blooms have an annual periodicity, peaking in the Austral autumn when the mixed layer deepens. This suggests that stratification erosion is key supplying nutrients into the euphotic zone and triggering these episodes.
How to cite. Cetina-Heredia, P., van Sebille, E., Matear, R., and Roughan, M.: Lagrangian characterization of nitrate supply and episodes of extreme phytoplankton blooms in the Great Australian Bight, Biogeosciences Discuss. [preprint], https://doi.org/10.5194/bg-2016-53, 2016.
Characterizing phytoplankton growth influences fisheries and climate. We use a lagrangian approach to identify phytoplankton blooms in the Great Australian Bight (GAB), and associate them with nitrate sources. We find that 88 % of the nitrate utilized in blooms is originated between the GAB and the SubAntarctic Front. Large nitrate concentrations are supplied at depth but do not reach the euphotic zone often. As a result, 55 % of blooms utilize nitrate supplied in the top 100 m.
Characterizing phytoplankton growth influences fisheries and climate. We use a lagrangian...