Dr. Charles W. Reimer dedicated almost 50 years of his life to the development and maintenance of the ANSP Diatom Herbarium. Today this is one of the largest diatom collections in the World. Its holdings include many historic and taxonomically important collections of prominent diatomists. Extensive collections of diatoms from river, lake, and wetland surveys conducted across North America by ANSP staff, environmental agencies, corporations, and individual researchers represent the core of the Herbarium holdings, which are an important resource for diatom systematic, biogeographical and environmental studies. This paper gives an overview of the history of the Herbarium, its holdings and structure, and ongoing renovations of the collection.

The Reimer Diatom Herbarium (ILH) at Iowa Lakeside Laboratory (ILL), a field station of Iowa's state universities, contains 3,280 permanent diatom slides of collections made from prairie potholes, alkaline fens, acid bogs, eutrophic lakes, saline lakes, Pleistocene paleolakes, and Miocene fossil deposits near ILL. The herbarium has a focus on collections made within Dickinson County, a region with an important legacy of study by students and visiting researchers from the US, Canada, and international institutions. The herbarium is well documented by taxon and location catalogues. The taxon card catalogue contains over 2,800 records referencing 67 genera, and the location card catalogue references collection sites from 51 counties in 16 North American states. Curated slides include over 300 species identifications made, or verified, by C.W. Reimer. Most curated slides have diatom specimens identified to species, circled with a diamond objective marker, and indicated on the slide label Six holotypes are included in the herbarium and we present the first light micrograph images of these type specimens. We present documentation of the contents and current condition of the herbarium and report that it is now available to researchers for scientific study. Many of the sites represented in the Reimer Diatom Herbarium are the same locations visited each year by students and visiting researchers at ILL, resulting in an important resource for monitoring environmental change, resolving taxonomic issues, and understanding species distributions in unique habitats.

Cosmioneis Mann et Stickle is a pennate diatom in the family Cosmiondeidaceae and order Naviculales. A single species of this genus (Navicula pusilla W. Sm., now Cosmioneis pusilla (W. Sm.) Mann et Stickle), had been previously reported from the island of Oahu, in the Hawai'ian archipelago. In extensive surveys of algae of subaerial habitats in Hawai'i we collected samples from the islands of Maui and Oahu, from which we distinguished populations of three species of Cosmioneis. Reports from other habitats describe C. pusilla as morphologically variable with valve ends ranging from subrostrate to strongly capitate. Our populations of Cosmioneis showed little variability and were either strongly capitate, rostrate or broadly lanceolate. We discuss the morphology and ecology of Cosmioneis in Hawai'i and propose three new species in this genus, Cosmioneis reimeri, Cosmioneis citriformis and Cosmioneis hawaiiensis. Light and scanning electron micrographs of the new species are provided.

New taxa: Cosmioneis reimeri Lowe and Sherwood, Cosmioneis citriformis Sherwood and Lowe, Cosmioneis hawaiiensis Lowe and Sherwood

Three new diatoms from North American rivers are described: Staurosira reimeri, Staurosirella elegantula and Staurosirella magna. The features of these diatoms are distinctive, and although they are reported here for the first time, misidentifications and lumping with other taxa in the past are likely. The finding of these three new taxa has two main implications: 1) knowledge of the diversity of araphid diatoms in the Fragilariaceae in North America is still incomplete, and 2) the full set of characters for araphid genera such as Staurosira and Staurosirella is still unknown since the three species described here have novel characters that were unknown or uncommon until the present study. The morphology of the new taxa is shown using light microscopy (LM) and scanning electron microscopy (SEM) and compared with the available literature on this group. S. reimeri is unique within Staurosira because it includes rhomboid, isopolar valves with a narrow linear axial area, rudimentary spines, and apical pore fields reduced to two slits located perpendicularly on the valve mantle edge at the valve apices. S. elegantula and S. magna are unique within Staurosirella due to their large and heavily silicified valves. Both taxa are also shown here to have thick spines with less densely silicified cores, a first report of this feature for Staurosirella. Additionally, S. magna has copulae possessing well developed ligulae that can be folded outwards, a feature that has not been seen in any other published taxa within Staurosirella. Finally, two varieties are transferred to the genus Staurosirella at the species level: S. dubia and S. rhomboides, based on a previous study of these diatoms in North American material done at the LM and SEM levels.

New taxa: Staurosira reimeri Morales, Manoylov et Bahls, Staurosirella elegantula Morales et Manoylov, Staurosirella magna Morales et Manoylov.

New combinations: Staurosirella dubia (A. Grunow) Morales et Manoylov, Staurosirella rhomboides (A. Grunow) Morales et Manoylov.

A new Eunotia species, E. charliereimeri, is described from Bear Meadows Bog near State College, Pennsylvania. Bear Meadows is an open, montane, nutrient-poor fen that is about 1.6 km long and 0.5 km wide with its open wetlands dominated by Sphagnum, sedges, swamp laurel, blueberry, sundews, Rhododendron spp., alder, Spiraea spp., and mountain holly. Eunotia charliereimeri has been collected intermittently from Bear Meadows over the last decade. Among the eunotioid diatoms, E. charliereimeri is characterized by its arcuate-lunate valve, prominent terminal raphe ends, and two rimoportulae per valve. Most importantly, it has amphoroid frustule symmetry, a character recently used to support the description of the new eunotioid genus Amphorotia Williams et Reid. However, E. charliereimeri does not share several other key features with Amphorotia including marginal spines or silica-rimmed external raphe fissures. A sister taxon, E. sarraceniae Gaiser et Johansen, described from South Carolina bays, shares the characteristic amphoroid symmetry and lunate shape, but E. sarraceniae is more finely striated, less arcuate, and has more rostrate ends than E. charliereimeri.

New taxon: Eunotia charliereimeri Edlund et Brant

We observed six diatom taxa from North American samples and one taxon from China that are considered within the genus Encyonema Kützing. Two of the taxa are described as new, Encyonema reimeri Spaulding, Pool et Castro sp. nov. and Encyonema nicafei Spaulding sp. nov. A third taxon, Encyonema stoermeri Spaulding, Pool et Castro nom. nov., shat. nov. is assigned a new name and rank. In the past, these taxa have been ascribed to several names, but primarily the names Cymbella muelleri Hustedt and C. muelleri f. ventricosa (Tempère et Peragallo) Reimer have been used, based on their inclusion in the two volumes of “The Diatoms of the United States”. We compare the new species with other members of this group of taxa, including Encyonema latum Krammer, E. sinicum Krammer and E. yellowstonianum Krammer. This group of species shares the features of 1) a broad axial area, 2) raphe branches curved with the convex side toward the dorsal valve margin, 3) slightly expanded and dorsally deflected proximal raphe ends, and 4) oval areolae near the axial area, becoming lineolate, or transapically elongate, towards the dorsal margin. We expect that many of the species reported in the U.S. have been identified using names of species from other continents. We also expect that critical microscopy and use of original literature is likely to clarify the geographic distribution of species within Encyonema. This work is important in order to understand, document and protect the species diversity of diatoms and their aquatic habitats.

New taxa: Encyonema reimeri Spaulding, Pool et Castro, Encyonema nicafeiSpaulding

Change in name and rank: Encyonema stoermeri Spaulding, Pool et Castro

Many closely related diatom species are differentiated by simple morphometric characters such as length, width, and striae density. In addition, simple shape descriptors, such as curvature of the valve, can also be distinguishing morphometric characters. The curvature calculation described here is an intermediate technique between simple, direct measurements (i.e., length, width) and more complex descriptors of shape. The goal of this work is to develop a simple technique to calculate diatom curvature. Curvature is calculated from the length of a chord and the length of its sagitta (the perpendicular segment between the chord to the midpoint of the arc). These parameters correspond to diatom valve length and valve deflection from the chord and are incorporated into the equation: κ; = 2h(l² h²)^-1(where κ; = curvature, l = half of the chord length, and h = sagitta length). This equation can be utilized to estimate the curvature of the valve margin, valve margin asymmetry, and other morphological structures including apices and central area shape, and complex valve shapes.

For clear observation of diatom frustules, both inner- and extracellular impurities need to be eliminated from samples. This process is usually performed using oxidizing acids that can completely decompose organic matter. However, oxidizing acids often result in dissociation of frustules, and if oxidative byproducts are not washed out completely at the end of the process, they can act as impurities. Moreover, the treatment is time-consuming, and the necessity for subsequent rinsing may reduce the number of diatom frustules and/or valves because of loss during rinsing. Application of low-temperature plasma (LTP) was examined for diatom cleaning. LTP treatment is an extremely gentle cleaning method in which all the processes can be performed on a cover slip without rinsing with distilled water or the addition of chemicals. Application of this method to the tidal flat sample was found to be effective for the preservation of complete frustules, such as those observed in Amphora, Cocconeis and Planothidium species; with this treatment, there was no reduction in the diatom population during the cleaning process.

Eunotia fennica (Hustedt) Lange-Bertalot, originally described as E. denticulata var. fennica Hustedt, was identified in good numbers from a small Orchid Bog Pond, Newfoundland. We investigate the population and valve morphological structure of this taxon using LM and SEM preparations. Additional specimens representing the Eunotia denticulata-complex are identified from five regions across eastern and northern North America and are compared with E. fennica. Current problems in the taxonomy of the E. denticulata complex are explored through an investigation of the original descriptions, and characters used to separate E. denticulata, E. neoborealis and E. fennica are identified. A preliminary examination of water chemistry is also made and related to the taxa. This Orchid Bog Pond is an acidic, poorly buffered, dilute waterbody situated on a sphagnum bog with a selective diatom flora which includes a good population of E. fennica, a taxon presently identified across three continents.

Mastogloia smithii var. lacustris Grun. is the dominant diatom in periphyton mats of the calcareous, freshwater to brackish wetlands of Caribbean coasts. Despite oligotrophy, frequent desiccation, high irradiance and temperatures, and occasional fire, periphyton communities in these wetlands can produce over 2000 g m^-2 of organic biomass, prompting studies that examine stress resistance and maintenance of algal mats under extreme conditions. The diatom flora inhabiting periphyton mats from over 500 sites in the Florida Everglades and similar wetlands in Belize, Jamaica and Mexico was examined, and M. smithii var. lacustris was a persistent component, present in 97% of samples and comprising up to 80% of a diverse diatom assemblage. Valves at various stages of division were observed encased in extracellular polysaccharide that exceeded the cell volume; SEM observations confirm issuance from mantle pores resulting in suspension of the cell in a matrix dominated by cyanobacterial filaments. Using corresponding biophysical data from the collection sites, we define the optima for M. smithii var. lacustris along salinity, pH, phosphorus, and water depth gradients. Experiments revealed a collapse of M. smithii var. lacustris populations in the presence of above-ambient phosphorus concentrations and a rapid resurgence upon reflooding of desiccated mats. This widespread diatom taxon appears to play a critical role similar to that of cyanobacteria in microbial mats, and its disappearance in the presence of enrichment threatens biodiversity and the natural function in these systems that are increasingly influenced by urbanization.

Water level fluctuations, whether climatically induced or the result of artificial regulation, can have a profound effect upon lake processes, especially in shallow lakes. Confounding the impact of changing water levels is nutrient input resulting from anthropogenic changes in land use. Paleolimnological techniques were used in a shallow seepage lake to infer the importance of water level changes and shoreland development as a source of nutrients to the lake. A long-term record of lake level in a Wisconsin lake was obtained from the measurements obtained by residents, who measured the width of the beach in front of their property over 73 years. These measurements were converted to vertical elevation through a detailed survey in 2008. Additional lake elevations were inferred from a 110-year precipitation record. While the mean depth of the lake was 2.1 m, lake elevation fluctuated up to 2.4 m. Cottage development began in the 1920s, increased in the late 1930s and further increased in recent decades. The bulk sedimentation accumulation rate initially increased with early cottage development, but the rate tripled with intensified development in the latter part of the twentieth century. The increase in the sedimentation resulted from increased soil erosion. Even though erosional rates have declined in the last 2 decades, use of soil amendments, hydrated lime and synthetic fertilizers have resulted in additional nutrient input to the lake. Multivariate statistical techniques performed on the diatom community revealed the greater importance of phosphorus concentrations than changing lake elevation in structuring the diatom responses. This analysis suggested that shoreline development history was more important than changes in lake elevation as a source of nutrients to the lake. This shallow, seepage lake was much more responsive to landuse changes than to long-term water level fluctuations.