Abstract
Transparent exopolymer particles (TEP) are the central mechanism by which carbon is shuttled from the surface to the deep ocean. Despite the importance of these particles, the magnitude and drivers of temporal variability in the concentration and production rate of TEP in the ocean are not well resolved, especially in highly dynamic and productive regions like estuaries. Here, TEP dynamics were evaluated across weekly, tidal, and diel time scales within the Skidaway River Estuary (GA, USA) and adjacent coastal waters in the South Atlantic Bight. No significant trends in TEP concentration or production rates were observed over weekly time scales, though over tidal cycles, TEP concentration varied between tide stage and TEP:chlorophyll ratios were always lower at low relative to high tides. Over sequential diel cycles, TEP concentrations were two times higher at night relative to midday. Different biological and environmental variables were correlated with TEP dynamics (Spearman ρ) depending on the time scale considered, reinforcing the importance of time-specific drivers of TEP. These results emphasize the importance in considering the temporal variability of field-based TEP measurements, with implications for accurate assessments of carbon cycling in coastal ecosystems and the incorporation of TEP into carbon export models.
Highlights
IntroductionParticle attachment and/or aggregation aided by transparent exopolymer particles (TEP) is one of the most common
Particle attachment and/or aggregation aided by transparent exopolymer particles (TEP) is one of the most commonCommunicated by Zhanfei Liu Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.mechanisms that facilitates carbon export (Alldredge et al 1993; Engel 2004), from the surface to the deep ocean
Failure to consider temporal shifts in TEP concentrations or production rates may result in improper characterization of TEP dynamics, and it remains critical to understand the temporal rhythms of TEP sources and sinks and to identify variables which are important in mediating TEP dynamics across a range of time scales
Summary
Particle attachment and/or aggregation aided by transparent exopolymer particles (TEP) is one of the most common. There remains a high level of uncertainty associated with estimates of global carbon export flux, with reported estimates ranging from 5 to 16 Pg C y−1 (Boyd and Trull 2007; Falkowski et al 2011; Henson et al 2015). This wide variability is partially driven by a poor understanding of the spatial and temporal dynamics of microbial interactions and export flux. In terms of TEP, a great deal of prior work has focused on establishing spatial measurements of TEP and testing factors that may drive in situ TEP dynamics (e.g., TEP formation and standing stock concentrations) such as sunlight, nutrients, and microbial
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