Simulations of phytoplankton species and carbon production in the equatorial Pacific Ocean 2. Effects of physical and biogeochemical processes

A one-dimensional multi-component lower trophic level ecosystem model that includes detailed algal physiology is used to investigate the response of phytoplankton community and carbon production and export to variations in physical and biochemical processes in the Cold Tongue region of the equatorial Pacific Ocean at ON, 140W. Results show that high-frequency variability in vertical advection and temperature is an important mechanism driving the carbon export. Filtering out low frequency physical forcing results in a 30% increase in primary production and dominance of high-light adapted Prochlorococcus and autotrophic eukaryotes. Sensitivity studies show that iron availability is the primary control on carbon export and production; whereas, algal biomass concentration is largely regulated by zooplankton grazing. Recycled iron is an important component of the ecosystem dynamics because sustained growth of algal groups depends on remineralized iron which accounts for 4.0% of the annual primary production in the Cold Tongue region. Sensitivity studies show that although all algal groups have a considerable effect on simulated phytoplankton carbon biomass, not all have a strong effect on primary production and carbon export. Thus, these sensitivity studies indicate that it may not be necessary to represent a broad spectrum of algal groups in carbon cycle models, because a few key groups appear to have a large influence on primary production and export variability. Combining the low-light adapted Prochlorococcus, high-light adapted Prochlorococcus and Synechococcus groups as a single group and using a three algal group model may be sufficient to simulate primary production and export variability in the tropical Pacific waters. The results from this modeling study suggest that the net effect of increased stratification and temperature conditions is a decrease in carbon export in the Cold Tongue region and a shift in the phytoplankton community towards smaller algal forms (e.g., Prochlorococcus spp. and Synechecoccus). Increased stratification can result in decreased iron concentration and reduced vertical velocities, both of which contribute to decreased carbon export. Also, stratified conditions enhance the remineralization rate of nutrients (e.g., iron), which enhances carbon production. Thus, inclusion of iron dynamics in climate models may be needed to fully represent the effect of climate variability on equatorial Pacific ecosystems.


Simulations of phytoplankton species and carbon production in the equatorial Pacific Ocean 1. Model configuration and ecosystem dynamics
Salihoğlu, Barış (2007-03-01)
The primary objective of this research is to investigate phytoplankton community response to variations in physical forcing and biological processes in the Cold Tongue region of the equatorial Pacific Ocean at ON, 140W. This research objective was addressed using a one-dimensional multicomponent lower trophic level ecosystem model that includes detailed algal physiology, such as spectrally-dependent photosynthetic processes and iron limitation on algal growth. The ecosystem model is forced by a one-year (19...
Modeling biogeochemical processes in subterranean estuaries: Effect of flow dynamics and redox conditions on submarine groundwater discharge of nutrients
Spiteri, Claudette; Slomp, Caroline P.; Tuncay, Kağan; Meile, Christof (American Geophysical Union (AGU), 2008-02-22)
[1] A two-dimensional density-dependent reactive transport model, which couples groundwater flow and biogeochemical reactions, is used to investigate the fate of nutrients (NO(3)(-), NH(4)(+), and PO(4)) in idealized subterranean estuaries representing four end-members of oxic/anoxic aquifer and seawater redox conditions. Results from the simplified model representations show that the prevalent flow characteristics and redox conditions in the freshwater-seawater mixing zone determine the extent of nutrient ...
Yilmaz, Elif; Salihoğlu, Barış; Department of Oceanography (2016-10-12)
Three areas of different ecosystem characteristics in the Northern Levantine Basin is compared using a 1-D multicomponent lower trophic level ecosystem model developed by SALIHOĞLU, B. et al. (2009) (NAGEM). Main focus was to analyze and compare the carrying capacity (PP) and regulatory mechanisms of the nutrients on lower trophic levels. 26 years’ of historical data obtained from METU-IMS data inventory and CORIOLIS was used to form a climatology, to introduce boundary conditions to the model as well as to...
Challenges in integrative approaches to modelling the marine ecosystems of the North Atlantic: Physics to fish and coasts to ocean
Holt, Jason; Allen, J. Icarus; Anderson, Thomas R.; Brewin, Robert; Butenschoen, Momme; Harle, James; Huse, Geir; Lehodey, Patrick; Lindemann, Christian; Memery, Laurent; Salihoğlu, Barış; Senina, Inna; Yool, Andrew (2014-12-01)
It has long been recognised that there are strong interactions and feedbacks between climate, upper ocean biogeochemistry and marine food webs, and also that food web structure and phytoplankton community distribution are important determinants of variability in carbon production and export from the euphotic zone. Numerical models provide a vital tool to explore these interactions, given their capability to investigate multiple connected components of the system and the sensitivity to multiple drivers, incl...
A physical-biochemical model of plankton productivity and nitrogen cycling in the Black Sea
Oguz, T; Ducklow, HW; Malanotte-Rizzoli, P; Murray, JW; Shushkina, EA; Vedernikov, VI; Unluata, U (1999-04-01)
A one-dimensional, vertically resolved, physical-biochemical upper ocean model is utilized to study plankton productivity and nitrogen cycling in the central Black Sea region characterized by cyclonic gyral circulation. The model is an extension of the one given by Oguz et al. (1996, J, Geophys. Res. 101, 16585-16599) with identical physical characteristics but incorporating a multi-component plankton structure in its biological module, Phytoplankton are represented by two groups, typifying diatoms and flag...
Citation Formats
B. Salihoğlu, “Simulations of phytoplankton species and carbon production in the equatorial Pacific Ocean 2. Effects of physical and biogeochemical processes,” JOURNAL OF MARINE RESEARCH, pp. 275–300, 2007, Accessed: 00, 2020. [Online]. Available: