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Six species of large-celled Pinnularia Ehrenberg from lakes of eastern North America, P. dariana (A.W.F. Schmidt) Mills, P. alabamae Krammer, P. bihastata (A. Mann) R.M. Patrick, P. torta (A. Mann) R.M. Patrick, P. rexlowei sp. nov. and P. spinifera sp. nov. are investigated with light and scanning electron microscopy. All six species are shown to possess marginal spines, a trait sporadically encountered in Pinnularia and generally rare in raphid diatoms. Besides having spines, the six species differ in their frustular morphology, including appearance and position of spines. We summarize data on their ecology and distribution using a set of 702 sediment core samples from 424 lakes from eastern USA and Canada. Pinnularia rexlowei is only known from Quaternary lacustrine deposits in the State of Connecticut and from the surface and subfossil sediments of two lakes in northeastern USA. The other five species are relatively common, and at least one species of spine-bearing Pinnularia was found in 34% of studied lakes. Pinnularia dariana and P. torta reach as far north as Labrador, while P. alabamae, P. bihastata and P. spinifera were only encountered south of Canada. Pinnularia alabamae and P. spinifera are characteristic for lakes with relatively soft and slightly acidic water, while P. bihastata, P. dariana and P. torta are found in a wider range of physico-chemical conditions, including alkaline and eutrophic lakes. [ABSTRACT FROM AUTHOR]

Sediment diatoms are widely used to track environmental histories of lakes and their watersheds, but merging datasets generated by different researchers for further large-scale studies is challenging because of taxonomic discrepancies caused by rapidly evolving diatom nomenclature and taxonomic concepts. We collated five datasets of lake sediment diatoms from the Northeastern USA using a harmonization process which included updating synonyms, tracking the identity of inconsistently identified taxa, and grouping those that could not be resolved taxonomically. Each harmonization step led to an increase in variation explained by environmental variables and a parallel reduction of variation attributable to taxonomic inconsistency. To maximize future use of the data and underlying specimens we provide the original and harmonized counts for 1327 core samples from 607 lakes, name translation schemes, sample metadata, specimen museum locations, and the Northeast Lakes Voucher Flora, which is a set of light microscope images grouped into 1154 morphological operational taxonomic units. Post-hoc harmonization enables data quality control when other approaches (e.g., upfront management of taxonomic consistency) are not possible. Measurement(s) diatom taxa • abundance Technology Type(s) observation • literature review • digital curation Sample Characteristic - Organism Bacillariophyta Sample Characteristic - Environment Lakes Sample Characteristic - Location Northeastern Unites States of America [ABSTRACT FROM AUTHOR]

A new species of Aulacoseira Thwaites is described from sediment deposits of Surprise Lake, an isolated lake located in the New Jersey Highlands. The species is characterized by (1) a low mantle, (2) unevenly distributed mantle areolae of variable size and shape, and (3) a valve face covered by rounded areolae. The new species is most similar to Aulacoseira biseriata (Grunow in Van Heurk) Houk, R. Klee & H. Tanaka. Both taxa possess frustules with mantles that are low, with irregular pervalvar rows or scattered areolae. However, the two species differ in the shape and pattern of the areolae, the shape and structure of the mantle wall, the shape and depth of the ringleist, and other morphological features. In this study, we present light and scanning electron microscopic images of the new species and compare it to the most similar taxa. [ABSTRACT FROM AUTHOR]

Desianti, N.; Potapova, M.; Enache, M.; Belton, T.J.; Velinsky, D.J.; Thomas, R., and Mead, J., 2017. Sediment diatoms as environmental indicators in New Jersey coastal lagoons. In: Buchanan, G.A.; Belton, T.J., and Paudel, B. (eds.), A Comprehensive Assessment of Barnegat Bay-Little Egg Harbor, New Jersey. The goal of this study was to explore the possible use of sediment diatoms as environmental indicators in New Jersey coastal lagoons. Diatom samples were collected from 100 sites in Barnegat Bay and Great Bay representing both subtidal and intertidal habitats. A total of 603 diatom taxa were found, with most samples characterized by high species diversity. A strong north-to-south salinity gradient in the study area was a major factor influencing composition of diatom assemblages. Subtidal sediments, especially in highly productive areas in the northern part of the Barnegat Bay, contained a high proportion of planktonic diatoms, especially small-celled Cyclotella and Chaetoceros species. Habitat type and physical properties, such as particle size and depth, were other important factors structuring diatom assemblages. Water-column nutrients and sediment contaminants did not show much effect on sediment diatoms, possibly due to the overriding effect of salinity or low variability in nutrient/contaminant concentrations. However, the organic matter content of sediments was significantly related to diatom species composition. Both sediment carbon and nitrogen were considerably higher in the northern part of the Barnegat Bay and other areas experiencing strong human impacts. This study developed diatom inference models for salinity and sediment nitrogen content and concluded that diatom species with relatively high optima for sediment nitrogen may be used as indicators of nutrient enrichment in studied lagoons. [ABSTRACT FROM AUTHOR]