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382. Quantifying the time lag between organic matter production and export in the surface ocean: Implications for estimates of export efficiency

Author

Stange, P., Bach, L. T., Le Moigne, F. A. C., Taucher, J., Boxhammer, T., and Riebesell, U.

Abstract

The ocean's potential to export carbon to depth partly depends on the fraction of primary production (PP) sinking out of the euphotic zone (i.e., the e‐ratio). Measurements of PP and export flux are often performed simultaneously in the field, although there is a temporal delay between those parameters. Thus, resulting e‐ratio estimates often incorrectly assume an instantaneous downward export of PP to export flux. Evaluating results from four mesocosm studies, we find that peaks in organic matter sedimentation lag chlorophyll apeaks by 2 to 15 days. We discuss the implications of these time lags (TLs) for current e‐ratio estimates and evaluate potential controls of TL. Our analysis reveals a strong correlation between TL and the duration of chlorophyll abuildup, indicating a dependency of TL on plankton food web dynamics. This study is one step further toward time‐corrected e‐ratio estimates. In times of rising atmospheric carbon dioxide concentrations, it is important to understand how efficient our oceans are in transporting organic matter produced in the surface to depth. In order to estimate this efficiency, surface production and organic matter arrival at depth are monitored simultaneously during field expeditions. Unfortunately, the produced organic matter does not sink out immediately and when it does, it may be transported horizontally by currents. Without the ability to track this organic matter on its way through the water column, we may connect collected organic matter at depth to production measurements at the surface that are completely unrelated. In this paper, we address the temporal part of the problem: the time lag between production of organic matter at the surface and the initiation of its sinking process. We find that this time lag differs substantially throughout the ocean. We argue that this is due to differences in the plankton community. The large range of time lag we observed shows that we have to adapt our methodology in estimating the efficiency of organic matter transport to depth. Otherwise, we may under‐ or overestimate the oceans potential to store carbon. We calculated time lags between peaks in chlorophyll a and organic matter sedimentation for four mesocosm studies in different regionsTime lags varied between 2 to 15 days at the surface and increased with depth depending on sinking velocitiesTime lag correlated with chlorophyll abuildup rate, indicating a dependency of time lag on the plankton community structure

Published
2017
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387. Genotyping an Emiliania huxleyi (prymnesiophyceae) bloom event in the North Sea reveals evidence of asexual reproduction.

Author

Krueger-Hadfield, S. A., Balestreri, C., Schroeder, J., Highfield, A., Helaouët, P., Allum, J., Moate, R., Lohbeck, K. T., Miller, P. I., Riebesell, U., Reusch, T. B. H., Rickaby, R. E. M., Young, J., Hallegraeff, G., Brownlee, C., and Schroeder, D. C.

Subjects
GENOTYPE-environment interaction, COCCOLITHUS huxleyi, CLIMATE change, PLANT habitats, ASEXUAL reproduction
Abstract

Due to the unprecedented rate at which our climate is changing, the ultimate consequence for many species is likely to be either extinction or migration to an alternate habitat. Certain species might, however, evolve at a rate that could make them resilient to the effects of a rapidly changing environment. This scenario is most likely to apply to species that have large population sizes and rapid generation times, such that the genetic variation required for adaptive evolution can be readily supplied. Emiliania huxleyi (Lohm.) Hay and Mohler (Prymnesiophyceae) is likely to be such a species, as it is the most conspicuous extant calcareous phytoplankton species in our oceans with growth rates of 1 day-1. Here we report on a validated set of microsatellites, in conjunction with the coccolithophore morphology motif genetic marker, to genotype 93 clonal isolates collected from across the world. Of these, 52 came from a single bloom event in the North Sea collected on the D366 United Kingdom Ocean Acidification cruise in June-July 2011. There were 26 multilocus genotypes (MLGs) encountered only once in the North Sea bloom and 8 MLGs encountered twice or up to six times. Each of these repeated MLGs exhibited Psex values of less than 0.05, indicating each repeated MLG was the product of asexual reproduction and not separate meiotic events. In addition, we show that the two most polymorphic microsatellite loci, EHMS37 and P01E05, are reporting on regions likely undergoing rapid genetic drift during asexual reproduction. Despite the small sample size, there were many more repeated genotypes than previously reported for other bloomforming phytoplankton species, including a previously genotyped E. huxleyi bloom event. This study challenges the current assumption that sexual reproduction predominates during bloom events. Whilst genetic diversity is high amongst extant populations of E. huxleyi, the root cause for this diversity and ultimate fate of these populations still requires further examination. Nonetheless, we show that certain CMM genotypes are found everywhere, while others appear to have a regional bias. [ABSTRACT FROM AUTHOR]

Published
2014
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391. Das Kohlenstoffrätsel

Author

Riebesell, U., Wolf-Gladrow, Dieter, Riebesell, U., and Wolf-Gladrow, Dieter

Published
1993

392. Phytoplankton growth and CO2

Author

Riebesell, U., Wolf-Gladrow, Dieter, Smetacek, Victor, Riebesell, U., Wolf-Gladrow, Dieter, and Smetacek, Victor

Published
1993

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