Physical and chemical predictors of diatom dissolution in freshwater and saline lake sediments in North America and West Greenland

Abstract

Diatom dissolution in surface sediment samples from two regional lake datasets in the Northern Great Plains (NGP; n 5 64) and West Greenland (n 5 40) is assessed using a morphological approach categorizing valves during routine diatom analysis. Two dissolution indices are derived to parameterize diatom dissolution, and, when compared between two analysts in a blind test, show good correspondence and are closely correlated to diatom fragmentation. We explore the relationships between hydrochemical and physical lake parameters (including meromixis) on dissolution within both lake regions using multivariate methods and modeled with logistic regression. Salinity is the sole significant predictor of dissolution in West Greenland but salinity, carbonate concentration ([CO 3 22 ]) and meromixis are significant predictors in the NGP. Limnological parameters explain 40-59% of variation in dissolution in both regions for both dissolution indices. The dissolution index methodology is applied to a short sediment sequence from Devils Lake (North Dakota), where diatom-inferred salinity inferences can be compared with a historical record of salinity fluctuations over the 20th century. Absolute errors in paleosalinity estimates are strongly correlated with diatom dissolution, with salinity overestimated in 8 out of 11 poorly preserved samples. Preservation does appear to constrain the reliability of the inferred paleosalinity at this site and may also affect the quality of diatom-based paleoenvironmental inferences elsewhere (including estimates of biogenic silica), where preservation state is often not explicitly considered.

Sedimentary DNA versus morphology in the analysis of diatom-environment relationships

“…The number of chloroplast DNA copies results mainly from the number of chloroplasts per cell and the number of chloroplast genomes per chloroplast, which vary across diatom taxa (Bedoshvili et al 2009). Other aspects regarding taphonomy are the preservation potential of DNA Pedersen et al 2015) versus diatom valves (Ryves et al 2006) and the different representations of DNA versus valves in the various lake habitats, for example caused by different transport characteristics and adsorption of DNA to sediments (Torti et al 2015;Turner et al 2015).…”

Taphonomic signatures and paleoecology of Holocene diatom assemblages in the Llano Grande Basin, northwestern Andean Cordillera, Colombia

“…According to Ryves et al (2006) In general, the trend curves of density, fragmentation, and dissolution of the diatoms showed similar patterns throughout the study section. The values for these variables in the intervals of 22-29 cm, 244-315 cm, and 468-536 cm (mid Holocene) are low and can be ignored.…”

“…Among pennate genera, Eunotia exhibits the greatest diversity (106 species), followed by Pinnularia (21), Encyonopsis (17), Encyonema (16), Gomphonema (14), Navicula (13), Brachysira (12), Frustulia (10), Actinella (7), Cymbopleura (7), Fragilaria (6), Neidium, Caloneis (5), Diploneis (5), Achnanthes (4), Melosira Table 1. The dissolution states of diatoms according to the method established by Ryves et al (2006) and the fragmentation state of diatoms according to Sierra-Arango (2013).…”

“…Additionally, all of the central fragments of the valve and those parts that displayed the taxonomic characteristics (such as the apices) were considered, assuming that the sum of two apical fragments and one central fragment equals one valve. From the counted diatoms that were identifi ed at the species level, the authors separated those that exhibited different scales of dissolution following the method established by Ryves et al (2006).…”

“…Additionally, this study is also the fi rst to evaluate two taphonomic variables from diatom assemblages (fragmentation and dissolution). The established dissolution method was applied following Ryves et al (2006), while the fragmentation determination was conducted based on SierraArango (2013).…”