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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]

Sediment samples from the coastal lagoons and estuaries of New York and New Jersey were used to investigate the influence of contaminants on diatom assemblages. Multivariate analyses demonstrated correspondence between composition of diatom assemblages and concentrations of several metals and total PAH. The effects of the individual contaminants were difficult to disentangle because of the considerable correlations between their concentrations. The most conspicuous trend was the increase in the relative abundance of small centric planktonic diatoms in response to contamination and the corresponding decrease in the benthic flora. The high relative abundance of planktonic species on contaminated sediments apparently resulted not so much from their tolerance to pollution, but from the paucity of benthic species. A comparison of the assemblages on the surface and at the depth of approximately 8–10 cm revealed a statistically significant temporal change in community composition towards planktonic diatoms. [ABSTRACT FROM AUTHOR]

• DNA metabarcoding is an emergent tool for biodiversity assessments. • Benthic eukaryotic assemblages were characterized using18S-V9 rDNA. • Diatoms, water molds, holozoans, green algae, fungi responded to stream impairment. • This approach may be recommended for biomonitoring of stream eukaryotic biota. DNA metabarcoding is rapidly expanding as a new approach to biodiversity assessments and biomonitoring and is especially valuable for characterizing microbial communities in aquatic habitats. When applied to eukaryotic organisms, metabarcoding is usually targeting specific taxonomic groups, such as macroinvertebrates, fungi, diatoms, or other protists. The goal of this study was to explore the potential use of metabarcoding of entire biofilm eukaryotic assemblages for the purpose of stream biomonitoring. We sampled 14 stream sites in New Jersey, USA along an impairment gradient and characterized rock biofilm assemblages using Illumina Mi-Seq sequencing of the V9 hypervariable region of 18S rDNA following the Earth Microbiome Project (EMP) protocol. We also enumerated diatoms from the same samples to compare DNA metabarcoding results with morphological assessments. Among the 5866 unique rDNA sequence variants, the fungal and holozoan sequences were the most diverse, while diatom sequences were the most abundant in most sites. Among-site variability of assemblage composition was significantly higher than within-site variability of field and lab replicates, which indicates an acceptable level of reproducibility of the method. Different taxonomic groups of eukaryotes exhibited similar, but not identical patterns of assemblage variation in response to underlying environmental gradients. Both morphological and metabarcoding approaches recovered strong relationships between diatom assemblage composition and water quality impairment. Several other groups of eukaryotes, such as fungi, peronosporomycetes, green algae, and holozoans had only slightly weaker response to water quality impairment than diatoms. These findings suggest that molecular characterization of biofilm eukaryotic assemblages can be an effective tool for monitoring stream biota and its responses to disturbance even if the taxonomic assignments of sequences are only partially resolved. [ABSTRACT FROM AUTHOR]