USGS Science⌕ Search

Geology topics

S. A. Spaulding

Publications and source records attributed to S. A. Spaulding.

12 recordsLinked to original sources
USGS2019

New and interesting species of the genus Muelleria (Bacillariophyta) from the Antarctic region and South Africa

During a survey of the terrestrial diatom flora of some sub-Antarctic islands in the southern Indian and Atlantic Oceans and of the Antarctic continent, more than 15 taxa belonging to the genus Muelleria were observed. Nine of these taxa are described as new species using light and scanning electron microscopy. Comments are made on their systematic position and how they are distinguished from other species in the genus. Additionally, two previously unrecognized taxa within the genus were discovered in samples from South Africa. One of these, Muelleria taylorii Van de Vijver & Cocquyt sp. nov., is new to science; the other, Muelleria vandermerwei (Cholnoky) Van de Vijver & Cocquyt nov. comb., had been included in the genus Diploneis. The large number of new Muelleria taxa on the (sub)-Antarctic locations is not surprising. Species in Muelleria occur rarely in collections; in many habitats, it is unusual to find more than 1-2 valves in any slide preparation. As a result, records are scarce. The practice of "force-fitting" (shoehorning) specimens into descriptions from common taxonomic keys (and species drift) results in European species, such as M. gibbula and M. linearis, being applied to Antarctic forms in ecological studies. Finally, the typical terrestrial habitats of soils, mosses and ephemeral water bodies of most of these taxa have been poorly studied in the past.

Phycologia↗
USGS2014

The microbial plankton of Lake Fryxell, southern Victoria Land, Antarctica during the summers of 1992 and 1994

Samples collected from Lake Fryxell, southern Victoria Land, Antarctica in January 1992 and 1994 were analysed for the abundance of bacterioplankton and the diversity and abundance of protistan plankton. At the times of sampling, 14 ciliate species and 10 species of autotrophic flagellate were recorded. The samples contained two species of rotifer (Philodina spp.), which formed the first record of planktonic metazoans in the Dry Valley lakes of this region of Antarctica. Bacterial concentrations ranged between 1.0 and 3.8 x 108 l-1 in the upper oxic waters increasing to 20 x 08 l-1 in the anoxic waters. Heterotrophic flagellates decreased in abundance down the oxygenated water column, disappearing completely at 9 m, and ranged between 0.28 and 7.39 x 105 l-1 in abundance. Autotrophic flagellates were much more abundant exhibiting a number of distinct peaks down the water column (1.89 25.3 x 108 l-1). The ciliated protozoa were very abundant (up to 7720 l-1) in relation to flagellate and bacterial numbers, typical of oligotrophic lakes world-wide. The distribution of the protistan plankton showed marked zonation, probably in response to the differing salinity and temperature gradients in the water column. Possible trophic interactions are discussed and comparisons with other continental Antarctic lakes made.

Polar Biology↗
USGS2011

Didymosphenia geminata: Algal blooms in oligotrophic streams and rivers

In recent decades, the diatom Didymosphenia geminata has emerged as nuisance species in river systems around the world. This periphytic alga forms large "blooms" in temperate streams, presenting a counterintuitive result: the blooms occur primarily in oligotrophic streams and rivers, where phosphorus (P) availability typically limits primary production. The goal of this study is to examine how high algal biomass is formed under low P conditions. We reveal a biogeochemical process by which D. geminata mats concentrate P from flowing waters. First, the mucopolysaccaride stalks of D. geminata adsorb both iron (Fe) and P. Second, enzymatic and bacterial processes interact with Fe to increase the biological availability of P. We propose that a positive feedback between total stalk biomass and high growth rate is created, which results in abundant P for cell division. The affinity of stalks for Fe in association with iron-phosphorus biogeochemistry suggest a resolution to the paradox of algal blooms in oliogotrophic streams and rivers. Copyright 2011 by the American Geophysical Union.

Geophysical Research Letters↗
USGS2009

Historical abundance and morphology of Didymosphenia species in Naknek Lake, Alaska

Since the 1980s, nuisance blooms of Didymosphenia geminata (Lyngbye) M. Schmidt have been documented in sites that are warmer and more mesotrophic than historical records indicate. While the invasion of D. geminata in New Zealand is well documented, it is less clear whether nuisance blooms in North America are a new phenomenon. In order to test the hypothesis that D. geminata blooms have increased in recent years, we examined the historical record of this species in sediments of Naknek Lake, in Katmai National Park, Alaska. Chronological control was established by relating the presence of two ash layers to known volcanic eruptions. We identified two species of Didymosphenia within the sediment record: D. geminata and D. clavaherculis (Ehrenberg) Metzeltin et Lange-Bertalot. This is the first published record of D. clavaherculis in North America. We found no statistically significant change in the numerical presence of D. geminata or D. clavaherculis, as a group, in Naknek Lake between the years 1218 and 2003. While there has been no sudden, or recent, increase in abundance of Didymosphenia in Naknek Lake, morphological features of D. geminata populations in Naknek Lake are distinct compared to morphological features of D. geminata in streams containing nuisance blooms from sites in North America and New Zealand. Variance in the morphology of Didymosphenia cells may help determine relationships between distinct sub-populations and establish the history of habitat invasion.

Conference Paper↗
USGS2008

Inland diatoms from the McMurdo Dry Valleys and James Ross Island, Antarctica

Diatom taxa present in the inland streams and lakes of the McMurdo Dry Valleys and James Ross Island, Antarctica, are presented in this paper. A total of nine taxa are illustrated, with descriptions of four new species (Luticola austroatlantica sp. nov., Luticola dolia sp. nov., Luticola laeta sp. nov., Muelleria supra sp. nov.). In the perennially ice-covered lakes of the McMurdo Dry Valleys, diatoms are confined to benthic mats within the photic zone. In streams, diatoms are attached to benthic surfaces and within the microbial mat matrix. One species, L. austroatlantica, is found on James Ross Island, of the southern Atlantic archipelago, and the McMurdo Dry Valleys. The McMurdo Dry Valley populations are at the lower range of the size spectrum for the species. Streams flow for 6-10 weeks during the austral summer, when temperatures and solar radiation allow glacial ice to melt. The diatom flora of the region is characterized by species assemblages favored under harsh conditions, with naviculoid taxa as the dominant group and several major diatom groups conspicuously absent. ?? 2008 NRC.

Botany↗
USGS2007

Increase in nuisance blooms and geographic expansion of the freshwater diatom Didymosphenia geminata

The diatom Didymosphenia geminata (Lyngbye) Schmidt is emerging as an organism with an extraordinary capacity to impact stream ecosystems on a global scale. In recent years, streams in New Zealand, North America, Europe, and Asia have been colonized by unprecedented masses of “didymo” and its extracellular stalks (fig. 1). This diatom is able to dominate stream surfaces by covering up to 100 percent of substrate with thicknesses of greater than 20 cm, greatly altering physical and biological conditions within streams. This species is expanding its geographic range in North America and the rate that nuisance blooms are reported by the public and local media are increasing, yet little scientific investigation of the phenomenon in North America has been initiated.

Open-File Report↗
USGS1998

Valve morphology and systematic position of Navicula walkeri (Bacillariophyceae), a diatom endemic to Oregon and California (USA)

Variation in valve size and ultrastructure is documented for Navicula walkeri, a freshwater diatom species endemic to Oregon and central California (USA). In LM, this large diatom has longitudinal lines on either side of the axial area, as well as lineolate striae. External proximal raphe ends recurve toward the same side as the deflected distal ends. A large central nodule and bulbous areas at the terminus of each raphe branch are visible internally. The edges of an axial plate form the image of longitudinal lines. The suite of features present in N. walkeri suggests it is part of Navicula sensu stricto but occupies an isolated position within the group. Navicula sensu stricto is not an entirely homogeneous assemblage, and further refinements of the systematic affinities of its members may be warranted.

California, Oregon↗
USGS1997

Diatoms in sediments of perennially ice-covered Lake Hoare, and implications for interpreting lake history in the McMurdo Dry Valleys of Antarctica

Diatom assemblages in surficial sediments, sediment cores, sediment traps, and inflowing streams of perennially ice-covered Lake Hore, South Victorialand, Antarctica were examined to determine the distribution of diatom taxa, and to ascertain if diatom species composition has changed over time. Lake Hoare is a closed-basin lake with an area of 1.8 km2, maximum depth of 34 m, and mean depth of 14 m, although lake level has been rising at a rate of 0.09 m yr-1 in recent decades. The lake has an unusual regime of sediment deposition: coarse grained sediments accumulate on the ice surface and are deposited episodically on the lake bottom. Benthic microbial mats are covered in situ by the coarse episodic deposits, and the new surfaces are recolonized. Ice cover prevents wind-induced mixing, creating the unique depositional environment in which sediment cores record the history of a particular site, rather than a lake=wide integration. Shallow-water (<1 m) diatom assemblages (Stauroneis anceps, Navicula molesta, Diadesmis contenta var. parallela, Navicula peraustralis) were distinct from mid-depth (4-16 m) assemblages (Diadesmis contenta, Luticola muticopsis fo. reducta, Stauroneis anceps, Diadesmis contenta var. parallela, Luticola murrayi) and deep-water (2-31 m) assemblages (Luticola murrayi, Luticola muticopsis fo. reducta, Navicula molesta. Analysis of a sediment core (30 cm long, from 11 m water depth) from Lake Hoare revealed two abrupt changes in diatom assemblages. The upper section of the sediment core contained the greatest biomass of benthic microbial mat, as well as the greatest total abundance and diversity of diatoms. Relative abundances of diatoms in this section are similar to the surficial samples from mid-depths. An intermediate zone contained less organic material and lower densities of diatoms. The bottom section of core contained the least amount of microbial mat and organic material, and the lowest density of diatoms. The dominant process influencing species composition and abundance of diatom assemblages in the benthic microbial mats is episodic deposition of coarse sediment from the ice surface.

Journal of Paleolimnology↗
USGS1997

Taxonomy and distribution of the genus Muelleria frenguelli

Navicula gibbula Cleve and its allies have a number of morphological characters which are visible under the light microscope and distinguish them from taxa included in Navicula Bory sensu stricto. These include proximal raphe ends which are sharply and unilaterally hooked and often extend beyond the central area, as well as two apparently thickened longitudinal ribs which extend the length of the valve on either side of the raphe. With the use of the SEM additional well-defined characters of the N. gibbula complex become apparent. Distal raphe ends are bifurcate and the valve face and mantle possess bipartite walls similar to those in Neidium Pfitzer. Furthermore, the apparently thickened longitudinal ribs are actually hollow canals, a feature reminiscent of the longitudinal canals of Diploneis Ehrenberg. Characters of the group are particularly well-defined and distinct from those of other genera, justifying separation from Navicula . Based on the valve morphology of N. gibbula and all other members of the section Naviculae fistulatae McCall, we separate these taxa from Navicula and resurrect the genus Muelleria Frenguelli to include them.

Diatom Research↗
USGS1993

Winter phytoplankton dynamics in a subalpine lake, Colorado, U.S.A

The temporal dynamics of phytoplankton were examined in The Loch, a subalpine lake in Rocky Mountain National Park, over the winter seasons of 1987-88 and 1988-89. The Loch was ice-covered from early November until early to mid May. The pattern of phytoplankton biovolume during ice-cover was consistent between the two years with maxima occurring in November/December and February/March. This pattern resulted principally from the contribution of Asterionella formosa Hass. Other dominant phytoplankton species in terms of biomass ( Dinobryon sertularia Ehrenb., Cryptomonas ovata Ehrenb., and Peridinium cinctum (Müll.) Ehrenb.) collectively contributed from 10 to 90 % of the total cells. Algal composition changed throughout the winter and individual species varied in abundance with depth. The same dominant (and most of the rare) taxa were present both years. They varied in time of occurrence and abundance, but did not occur at the same time in both years. Phytoplankton species composition continually fluctuated throughout the winter. Because of the stability afforded by ice-cover, algal species succession was not driven by thermal regime or by wind induced changes in the mixed depth. Nor did grazing by the winter zooplankton assemblage, composed nearly exclusively of cyclopoid copepods and rotifers, adequately explain the phytoplankton dynamics. Freeze concentration of water (concentration as ions are excluded in the formation of ice) in early winter may be responsible for the early phytoplankton bloom.

Colorado↗