An alternative method of particulate fluorescent tracer analysis in sediments using a microplate fluorimeter

Abstract

Conservative particulate fluorescent tracers (e.g. luminophores and microspheres) are commonly used in a wide range of sediment transport studies. Traditionally, their spatial redistribution is estimated by counting them in sediments under ultraviolet light (e.g. by epifluorescence microscopy), a time-consuming but effective method. While alternative methods have recently been developed (e.g. photodetection, digital image analyses), this 'classical' counting method remains the most commonly used. This article describes an alternative procedure for measuring the concentration of fluorescent tracers (here, microspheres) using a microplate fluorimeter. This technique enables simultaneous analysis of numerous samples while reducing the sediment preparation and quantification time. After a calibration step from sediment samples with known microsphere content, the method was validated by comparing results from the epifluorescence microscopy method. Different adjustments were also reported, as well as application examples. The different calibration tests showed high linear relationships between the microsphere concentration of sediment samples and the measured fluorimetric intensities (R2-0.99) with a detection limit of 6%. In comparison with the previously used method, very similar results were obtained, as illustrated in recent studies using both luminophores and microspheres. The rapid and reliable method proposed here will enable increasingly complex experiments to be performed with less time-consuming qualitative analyses.

Quantification of sediment reworking by the Asiatic clam Corbicula fluminea Müller, 1774

“…Then, sediment from each layer was homogenized, and subsamples were deposited in a 24-well microplate (BD Falcon TM , Franklin Lakes, NJ, USA). Luminophore distributions were quantified by fluorescence (bottom reading fluorescence; k excitation = 405 nm; k emission = 502 nm; area scan: 9 9 9) using a microplate reader (Synergy Mx, Biotek, Winooski, VT, USA) following a protocol slightly modified from Lagauzère et al (2011).…”

Benzo(a)pyrene inhibits the role of the bioturbator Tubifex tubifex in river sediment biogeochemistry

“…Each slice of fresh sediment was homogenized and a sub-sample was freeze-dried and deposited in a well of a 24-well microplate. Detection of luminophores was performed with a Synergy Mx microplate reader (Biotek, USA) according to a protocol adapted from Lagauzère et al (2011): fluorescence bottom reading; λem: 565 nm; λex: 602 nm; and area scan: 9 * 9.…”

Bioturbation functional roles associated with mangrove development in French Guiana, South America

“…In order to quantify the biologically induced sediment transport in cores, inert fluorescent particles, referred to as microspheres hereafter (Fluoresbrite Ò YG Microspheres, Polysciences Europe GmbH, Eppelheim, Germany), whose diameter (10 lm) corresponded to in situ silt sediment grains (70% of grains: 4 \ x \ 31 lm; preliminary data of 2012), were homogeneously introduced into a mud layer and deposited at the core sediment surface (Gerino et al, 2007;Lagauzere et al, 2011). The mud layers (2 mm thick, 10.4 cm diameter) were prepared with a mixture of surface sediment from each station and 400 ll of microsphere.…”

“…The proportions of microspheres were quantified by fluorescence (bottom reading fluorescence; k excitation = 441 nm; k emission = 486 nm; number of readings per well: 9 9 9) using a microplate reader Sinergy Mx (BioTek Instruments Inc., Winooski, VT, USA) following Lagauzere et al (2011) and Majdi et al (2014). Fluorescence values resulting from the microsphere emissions were obtained by subtracting the fluorescence value of natural sediments at different depths (additional cores) from the fluorescence measurements of incubated sediments.…”