Taucher, J and Stange, P and Alguero-Muniz, M and Bach, LT and Nauendorf, A and Kolzenburg, R and Budenbender, J and Riebesell, U, In situ camera observations reveal major role of zooplankton in modulating marine snow formation during an upwelling-induced plankton bloom, Progress in Oceanography, 164 pp. 75-88. ISSN 0079-6611 (2018) [Refereed Article]
Copyright 2018 Elsevier Ltd.
Here we present data from a high-resolution underwater camera system that we used to observe particle size distributions and formation of marine snow (aggregates>0.5 mm) over the course of a 9-week in situ mesocosm experiment in the Eastern Subtropical North Atlantic. After an oligotrophic phase of almost 4 weeks, addition of nutrient-rich deep water (650 m) initiated the development of a pronounced diatom bloom and the subsequent formation of large marine snow aggregates in all 8 mesocosms. We observed a substantial time lag between the peaks of chlorophyll a and marine snow biovolume of 9–12 days, which is much longer than previously reported and indicates a marked temporal decoupling of phytoplankton growth and marine snow formation during our study. Despite this time lag, our observations revealed substantial transfer of biomass from small particle sizes (single phytoplankton cells and chains) to marine snow aggregates of up to 2.5mm diameter (ESD), with most of the biovolume being contained in the 0.5–1mm size range. Notably, the abundance and community composition of mesozooplankton had a substantial influence on the temporal development of particle size spectra and formation of marine snow aggregates: While higher copepod abundances were related to reduced aggregate formation and biomass transfer towards larger particle sizes, the presence of appendicularia and doliolids enhanced formation of large marine snow.
Furthermore, we combined in situ particle size distributions with measurements of particle sinking velocity to compute instantaneous (potential) vertical mass flux. However, somewhat surprisingly, we did not find a coherent relationship between our computed flux and measured vertical mass flux (collected by sediment traps in 15m depth). Although the onset of measured vertical flux roughly coincided with the emergence of marine snow, we found substantial variability in mass flux among mesocosms that was not related to marine snow numbers, and was instead presumably driven by zooplankton-mediated alteration of sinking biomass and export of small particles (fecal pellets).
Altogether, our findings highlight the role of zooplankton community composition and feeding interactions on particle size spectra and formation of marine snow aggregates, with important implications for our understanding of particle aggregation and vertical flux of organic matter in the ocean.
|Item Type:||Refereed Article|
|Keywords:||biological carbon pump, export, plankton, marine snow, aggregation|
|Research Division:||Earth Sciences|
|Research Field:||Biological oceanography|
|Objective Division:||Expanding Knowledge|
|Objective Group:||Expanding knowledge|
|Objective Field:||Expanding knowledge in the earth sciences|
|UTAS Author:||Bach, LT (Dr Lennart Bach)|
|Web of Science® Times Cited:||7|
|Deposited By:||Ecology and Biodiversity|
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