Incorporation of oil into diatom aggregates
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abstract
The authors 2019. Rolling table experiments were conducted to investigate the incorporation of 2 types of dispersed oil into diatom aggregates. The goal was to provide specific input parameters for aggregation models that predict the transport of oil to depth via marine snow-sized aggregates (>0.5 mm). The amount of oil incorporated into aggregates is a function of both aggregated biomass and dispersed oil concentration. The maximum carrying capacity of diatom aggregates for dispersed oil likely lies at ~40% of the aggregated organic carbon. These data allow estimates of the amount of oil routed via the aggregation pathway. Furthermore, the concentrations of transparent exopolymer particles (TEP) and the composition of EDTA-extracted extracellular polymeric substances (EPS) were tested as generally valid proxies for stickiness, which is a critical value in aggregation models. TEP and EDTA-extractable EPS were correlated with each other, but aggregation success was not readily predictable from these measurements. The large chemical heterogeneity of TEP and EPS likely obscures a generally valid relationship. Additionally, we found that, contrary to expectations, the sinking velocity of oil-containing aggregates was not decreased, but slightly increased compared to their non-oil-containing counterparts. Tighter packaging of cells due to the oil likely causes this effect. Sinking velocity is an important parameter in aggregationsedimentation models, as it determines the time required for aggregates to reach the seafloor and thus the potential for flux attenuation. Transport of oil to the seafloor exposes benthic organisms, and those feeding on them, to substances that potentially have negative effects on organisms and ecosystems.
