Date

2018-11-19

Author

Karakuş, Onur

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In this study, a three dimensional, coupled ocean ecosystem model (FESOMREcoM2) is used to investigate the impact of krill on the ecosystem dynamics of the Southern Ocean in modeling studies. A new, second zooplankton group defined to be Antarctic krill is added to an already existing and validated setup of the modelling system. This species was chosen because it is a key organisms in the Southern Ocean. The effect of grazing on net primary production and export production due to the addition of Antarctic krill was investigated. It was hypothesized that inclusion of macrozooplankton (Antarctic krill) as a second zooplankton group in the model would improve the capability of the model to better represent relevant biogeochemical processes. After the implementation and parameterization of the new zooplankton group in the FESOM-RecoM2 model, two separate model runs over the duration of 25 years (with and without krill) were conducted, and the effect of Antarctic krill on nutrient distribution, total production, export production and the seasonal cycle of chlorophyll concentrations was analysed. Incorporating Antarctic krill in the model increased simulated nutrient concentrations (nitrate, silicate and iron) due to enhanced nutrient recycling. Also, the simulated spatial distribution and seasonal variation of primary production in the Southern Ocean were affected. The total net primary production did not show major differences between the simulations with and without the krill parametrization. However, export production decreased slightly after the implementation of krill. The seasonal cycle of nanophytoplankton chlorophyll concentrations as well as its concentration increased. However, the diatom chlorophyll concentrations did not show the similar change. After the implementation of the second zooplankton group, total chlorophyll concentrations did not show major changes. The krill simulation produced more zooplankton in the Southern Ocean compared to a previous study using REcoM2 in the Southern Ocean, which is considered as a major model improvement.

Subject Keywords

Antarctic krill, Ecosystem modeling, The Southern Ocean, Carbon cycle

URI

https://hdl.handle.net/11511/95087

Collections

Graduate School of Marine Sciences, Thesis