Spring bloom community change modifies carbon pathways and C : N : P : Chl <i>a</i> stoichiometry of coastal material fluxes

Abstract

Abstract. Diatoms and dinoflagellates are major bloomforming phytoplankton groups competing for resources in the oceans and coastal seas. Recent evidence suggests that their competition is significantly affected by climatic factors under ongoing change, modifying especially the conditions for cold-water, spring bloom communities in temperate and Arctic regions. We investigated the effects of phytoplankton community composition on spring bloom carbon flows and nutrient stoichiometry in multiyear mesocosm experiments. Comparison of differing communities showed that community structure significantly affected C accumulation parameters, with highest particulate organic carbon (POC) buildup and dissolved organic carbon (DOC) release in diatom-dominated communities. In terms of inorganic nutrient drawdown and bloom accumulation phase, the dominating groups behaved as functional surrogates. Dominance patterns, however, significantly affected C : N : P : Chl a ratios over the whole bloom event: when diatoms were dominant, these ratios increased compared to dinoflagellate dominance or mixed communities. Diatom-dominated communities sequestered carbon up to 3.6-fold higher than the expectation based on the Redfield ratio, and 2-fold higher compared to dinoflagellate dominance. To our knowledge, this is the first experimental report of consequences of climatically driven shifts in phytoplankton dominance patterns for carbon sequestration and related biogeochemical cycles in coastal seas. Our results also highlight the need for remote sensing technologies with taxonomical resolution, as the C : Chl a ratio was strongly dependent on community composition and bloom stage. Climate-driven changes in phytoplankton dominance patterns will have far-reaching consequences for major biogeochemical cycles and need to be considered in climate change scenarios for marine systems.

Shifts in phytoplankton community structure modify bacterial production, abundance and community composition

“…Some dinoflagellates show higher percentages of extra cellular release than dia toms (Castillo et al 2010, López-Sandoval et al 2013. However, during the spring bloom in the Baltic Sea, diatom-dominated communities excrete more DOC than mixed or dinoflagellate-dominated communities (Spilling et al 2014).…”

“…Diatoms settle more rapidly than dinoflagellates and transport more organic material with higher carbon:nitrogen:phosphorus (C:N:P) ratios to the seafloor (Arrigo et al 2012, Spilling et al 2014, whereas dinoflagellates either lyse before reaching the sediment (Heiskanen 1998) or settle as dormant resting cysts not readily available for remineralization (Spilling & Lindström 2008). Therefore, diatoms are likely more important than dinoflagellates in terms of input of organic matter to the benthic food web (Heiskanen 1998, Hög-lander et al 2004.…”

Chesapeake Bay nitrogen fluxes derived from a land‐estuarine ocean biogeochemical modeling system: Model description, evaluation, and nitrogen budgets

“…It is more likely caused by an overestimation of light attenuation due to ISS in the upper bay, and our simplifying assumption of a constant phytoplankton species composition in the bay. Because diatoms and dinoflagellates have differing C:Chl ratios and C:N ratios [Spilling et al, 2014], species composition differences may be responsible for the fact that spring blooms in both PON and chlorophyll observations are observed in the upper bay, whereas a spring bloom in chlorophyll and not PON is observed in the lower bay. As expected, correlations between simulated and observed PON concentrations (Figures 8a, 8c, 8e, 8g, 8i, and 8k) concentrations along the trench with background color representing the simulation and circles showing the observations.…”

Models of Plankton Community Changes during a Warm Water Anomaly in Arctic Waters Show Altered Trophic Pathways with Minimal Changes in Carbon Export

“…The C:chl ratio of 53 for phytoplankton was chosen as a compromise between spring and summer values and those for small and large phytoplankton cells as shown by mesocosm experiments in which C:chl ratio of diatoms, dinoflagellate and mixed composition were 95, 45, and 60, respectively (Svensen et al, 2011;Spilling et al, 2014). Similarly, phytoplankton in the Fram Strait in May and August 2014 had a C:chl ratio of 41 (Marit Reigstad, personal communication).…”