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  • 1
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    Distribution of transparent exopolymer particles (TEP) in the northeast Atlantic Ocean and their potential significance for aggregation processes (2004)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 51 (1). pp. 83-92.
    Details
    Publication Date: 2016-11-01
    Description: The abundance of transparent exopolymer particles (TEP) was determined in the northeast Atlantic Ocean (40–55°N, ∼20°W) during several cruises from June to November 1996. An accumulation of TEP in the water column was observed at bloom and post-bloom sites along a 20°W transect in June/July (maximum concentration: 124 μg Gum Xanthan equivalents (Xeq.) l−1), but concentrations were uniformly low (mean concentration: 28.5±10.2 μg Xeq. l−1) during autumn at the BIOTRANS site (47°N, 20°W). TEP concentrations in the open northeast Atlantic were considerably lower than previously published values from coastal sites. However, during June/July TEP:Chl a (weight/weight) ratios were comparable to values at coastal seas. It is suggested that phytoplankton production modulates TEP concentration in the open ocean as it does in coastal systems. TEP contributed significantly to the organic carbon pool as derived from the ratio TEP-C:POC, in summer (mean percentage: 17±7.5; w/w), as well as in autumn (mean percentage: 18±11, w/w). The potential influence of TEP on particle coagulation rates in the northeast Atlantic was assessed from estimates of their influence on particle stickiness and on particle volume concentrations. This indicated that TEP may be essential for initiating particle aggregation at low biomass concentrations, typical for open ocean sites.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.dsr.2003.09.001
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    The role of aggregation for the dissolution of diatom frustules (2003)
    Elsevier
    In:  FEMS Microbiology Ecology, 46 (3). pp. 247-255.
    Details
    Publication Date: 2020-03-20
    Description: Observations that the majority of silica dissolution occurs within the upper 200 m of the ocean, and that sedimentation rates of diatom frustules generally do not decrease significantly with depth, suggested reduced dissolution rates of diatoms embedded within sinking aggregates. To investigate this hypothesis, silica dissolution rates of aggregated diatom cells were compared to those of dispersed cells during conditions mimicking sedimentation below the euphotic zone. Changes in the concentrations of biogenic silica, silicic acid, cell numbers, chlorophyll a and transparent exopolymer particles (TEP) were monitored within aggregates and in the surrounding seawater (SSW) during two 42-day experiments. Whereas the concentration of dispersed diatoms decreased over the course of the experiment, the amount of aggregated cells remained roughly constant after an initial increase. Initially only 6% of cells were aggregated and at the end of the experiment more than 60% of cells were enclosed within aggregates. These data imply lower dissolution rates for aggregated cells. However, fluxes of silica between the different pools could not be constrained reliably enough to unequivocally prove reduced dissolution for aggregated cells.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0168-6496(03)00199-5
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Chemical and biological composition of suspended particles and aggregates in the Baltic Sea in summer (1999). (2002)
    Elsevier
    In:  Estuarine, Coastal and Shelf Science, 55 . pp. 729-741.
    Details
    Publication Date: 2019-09-23
    Description: Suspended particles and particle aggregates, which formed from concentrated field samples on the roller table, were characterized biologically and chemically along a transect through the Baltic Sea in summer 1999. Phytoplankton composition in field samples was dominated by cyanobacteria, including the filamentous diazotrophic cyanobacteria Aphanizomenon ‘ baltica’, Nodularia spumigena and Anabaena spp. These species formed aggregates together with diatoms, mainly Skeletonema costatum and Chaetoceros spp. and with dinoflagellates, mainly withDinophysis norvegica . Compared to the Redfield ratio, concentration ratios of particulate organic carbon, nitrogen and phosphorus, [POC]:[PON]:[POP], indicated an enrichment of carbon, especially in aggregates. However, regression analysis indicated a higher production rate of PON relative to POP and POC and significant background concentrations of POC. In field samples the concentration of transparent exopolymer particles (TEP) varied around 200 μg Xanthan Equiv. l−1 and comprised a volume fraction of 2–7 ppm and an abundance of about 105 TEP ml−1. TEP were enriched in aggregates as inferred from volume ratios of TEP to conventional particles. It is suggested, that TEP contribute substantially to the background concentration of POC, while the high production rate of PON is attributed to nitrogen fixation of diazotrophic cyanobacteria.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1006/ecss.2001.0927
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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