A new centric diatom genus is described from laminated freshwater sediments of Middle Eocene age ... more A new centric diatom genus is described from laminated freshwater sediments of Middle Eocene age near Horsefly, British Columbia, Canada. This diatom, Eoseira wilsonii gen. et sp. nov., grew in filaments that constitute dense monospecific sub-horizons within the white couplets that represent summer deposition in the varved sequence. Although Eoseira clearly belongs within the Family Aulacoseiraceae, several features distinguish its valve structure from Aulacoseira. Gigantism of spines and the lack of geometric relationships between spine position and mantle areolae are the most conspicuous features of the genus. Eoseira is among the oldest freshwater diatoms known and one of relatively few extinct freshwater genera. In addition to serving as a potential biostratigraphic marker, Eoseira is a cornerstone to undertanding the evolutionary trajectory of the Aulacoseiraceae, likely the oldest family of freshwater diatoms. As such, it refines our understanding of early radiations from the marine realm in western North America. Furthermore, paleoecological inferences based on Eoseira life strategy pertain directly to limnological conditions during early Cenozoic hot-house conditions. Résumé : Un nouveau genre de diatomée centrique est décrit à partir de sédiments laminés d'eau douce (datant de l'Éocène moyen) à proximité de Horsefly, Colombie-Britannique, Canada. Cette diatomée, Eoseira wilsonii gen et sp. nov., croissait dans des filaments qui constituent des sous-horizons denses monospécifiques à l'intérieur des couplets blancs, lesquels représentent la dépôt estival dans la séquence varvée. Bien que Eoseira appartienne clairement à la famille Aulacoseiraceae, plusieurs caractéristiques distinguent la structure de sa valve de celle d'Aulacoseira. Le gigantisme des épines et le manque de relations géométriques entre la position des épines et des pores aréolaires du manteau sont les caractéristiques les plus remarquables du genre. Eoseira est parmi les plus anciennes diatomées d'eau douce connues et l'un des relativement peu nombreux genres d'eau douce disparus. En plus de servir comme indicateur biostratigraphique potentiel, Eoseira précise nos connaissance de comprendre la lignée des Aulacoseiraceae, probablement la plus ancienne famille de diatomées d'eau douce. En tant que tel, cela affine nos connaissances des premiers retraits du domaine marin dans l'ouest de l'Amérique du Nord. De plus, les inférences paléo-écologiques basées sur la stratégie de vie d'Eoseira réfèrent directement aux conditions limnologiques durant les conditions de serre au Cénozoïque intérieur. [Traduit par la Rédaction] Wolfe and Edlund 257
Landscape Influences on Dissolved Organic Carbon, pH, Fe, and Ca in 37 Lakes in the Forest-Tundra of Northern Manitoba, Canada
AGUFM, Dec 1, 2009
DOC, pH, Fe, and Ca are major influences on lake ecosystems, and all three may be impacted by the... more DOC, pH, Fe, and Ca are major influences on lake ecosystems, and all three may be impacted by the surrounding catchment, especially the presence of wetlands and coniferous forest. To better understand past and future lake responses to climate change in the sub-arctic forest-tundra of northern Manitoba, we measured DOC, SUVA, pH, Ca, and Fe in 37 lakes in 2008
Interpreting Linkages among Landscape, Water Chemistry, and Diatom Communities to Better Understand Subarctic Paleoenvironmental Records
AGUFM, Dec 1, 2010
ABSTRACT Arctic ecosystem response to climate warming will likely be complex, with important link... more ABSTRACT Arctic ecosystem response to climate warming will likely be complex, with important linkages among terrestrial, wetland, and aquatic systems set within the context of geologically unique landscapes. Ecosystem responses to warming include: increased lake productivity, permafrost thaw, shrub expansion, and northward shifts in subarctic tree line. There have been many studies on freshwater aquatic responses to climate change in the Arctic, but few consider the role of the terrestrial landscape. As part of a three-year project to study the Holocene history of lakes and landscapes and their response to climate, we undertook a hydrobiological survey along the northern Manitoba boreal forest-tundra ecotone, with the aim of linking lake water chemistry with surrounding landscape and with the algal (diatom and chrysophyte) community composition in the lakes. Fossil algal assemblages from sediment cores can be better interpreted in terms of complex relationships between climate change, landscape change, and lake response if an understanding of modern linkages is developed. Using this modern study to develop quantitative calibration, sediment cores were used to focus on landscape-level biogeochemical changes in these systems at multiple time scales over the past 8,000 years. Forty-five lakes across the boreal-tundra transition were sampled for diatoms and physico-chemistry in 2008-2009 and their watersheds characterized using GIS. Diatoms were collected from the surface (top 1-cm) of a sediment core. Water quality measures included nutrients, anions and cations, pH, conductivity, Secchi depth, and dissolved carbon. Landscape variables including watershed area, watershed to lake area ratios, wetland area within 100 m of lake shore and percent cover of different vegetation types were calculated using GIS with on the ground verification. Primary gradients among the lakes are related to pH and water clarity. Among the landscape variables, distance to treeline, slope, wetland areas and areas of exposed till were strongly correlated to water quality variables, suggesting that landscape position and development across the tundra-boreal ecotone exert strong influence on water quality. Diatom communities showed strong relationships with both water chemistry and landscape variables. By applying diatom-based inference models, in conjunction with multi-proxy evidence from magnetics, pollen, and isotope data, we see relative stability in the recent record of algal community composition in some lakes, despite known climate changes in the region. Other core sections show lake response to shifts in vegetation; this suggests that certain settings buffer lakes from rapid climate changes. Understanding these processes has implications for how we understand linkages between terrestrial and aquatic ecosystems (e.g. coupled biogeochemical cycling of carbon and nitrogen) and how we interpret recent (~300 years) biological changes in the context of a lake's entire history.
We used light and electron microscopy to characterize a Late Miocene freshwater diatomite deposit... more We used light and electron microscopy to characterize a Late Miocene freshwater diatomite deposit in the Chalk Hills Formation, near Payette, Idaho, USA. The diatom assemblage from this sample was nearly monotypic, dominated by a single taxon with similarities to Lindavia bodanica (Thalassiosirales) but with several features uncharacteristic of the genus Lindavia, such as a rimoportula(e) on the valve mantle located on a costa, simple alveolar structure, and spines at the external valve face-mantle junction. A combination of other characters for this species complicate its placement into existing genera, including a lack of central fultoportulae, central area with loculate areolae with domed cribra, and a single ring of mantle fultoportulae with three satellite pores with well-developed cowlings and broad satellite pore covers. Based on this unique set of features, we have established a new genus, Fascinorbis, which appears to represent an important transitional form in the evolution of the Lindavia lineage.
Near-surface wind speeds have changed over recent decades, raising questions about the extent to ... more Near-surface wind speeds have changed over recent decades, raising questions about the extent to which these changes are altering the vertical thermal structure of lakes and affecting lake food webs. Neo-and paleolimnological techniques were used to assess wind-driven changes in lake thermal habitat and resulting effects on primary producers in two lakes in Isle Royale National Park, an island archipelago located in Lake Superior, where wind speed has increased in recent decades. Responses in Siskiwit Lake, a large (16 km 2 surface area), deep (Z max = 49 m), oligotrophic lake, were compared to those of Lake Desor, a moderately large (4.3 km 2 ) but shallower (Z max = 13 m), mesotrophic lake. High-frequency sensor data suggested that changes in wind speed affected epilimnion thickness in both lakes synchronously (ρ = 0.7, p < 0.001). Diatom-inferred mixing depths suggested a coherent shift in both lakes to deeper mixing (an increase of 3 and 6 m) since 1920 (ρ = 0.8), which was correlated with an increase in regional wind speed during the 20 th century at the decadal-scale in Lake Desor and Siskiwit Lake (ρ = 0.6 and 0.4, respectively). In Lake Desor, algal biomass declined as mixing deepened from 1920 to 1980, and then cyanobacteria and cryptophyte pigments increased from 1980 to present, a period of inferred stable and deep mixing. Algal pigment concentrations in Siskiwit Lake were unchanged as mixing depth deepened. Although changes in wind speed altered lake physical structure similarly, the ecological consequences of these changes differed between lakes and were most likely influenced by lake-specific variability in nutrient and light availability.
The genus Semiorbis (Eunotiaceae, Bacillariophyta) in North America
Diatom Research, Jan 2, 2021
The genus Semiorbis was erected by R.M.Patrick in 1966 as monotypic based on the relatively rare ... more The genus Semiorbis was erected by R.M.Patrick in 1966 as monotypic based on the relatively rare taxon Semiorbis hemicyclus. Defining characters for Semiorbis include strongly arcuate valves, short eunotioid raphe branches, well-developed external costae with spine-like projections on the virgae, lack of rimoportulae, and a broader dorsal mantle. New populations of Semiorbis were found in the central USA (Wisconsin) on Outer Island, Apostle Islands National Lakeshore, along southeast Lake Superior, from a lake in New Jersey (USA), and from a small arctic lake in Nunavut, Canada. The population in Outer Lagoon, a shallow embayment cut off from Lake Superior by a long-shore bar, provided documentation of living cells and colonies of Semiorbis. We examined the morphology, ecology, and taxonomy of these new populations using light and scanning electron microscopy, traditional morphometrics, and sliding landmarks shape analysis. We compared these populations to European populations of Semiorbis hemicyclus and North American populations of Semiorbis rotundus and Semiorbis catillifera. We determined that the population found in Wisconsin represents a new species herein described as Semiorbis eliasiae Edlund, D.R.L.Burge, N.A.Andresen & VanderMeulen sp. nov., the New Jersey (USA) population is Semiorbis rotundus, and the Nunavut (Canada) population represents a North American population of the generitype Semiorbis hemicyclus.
Estimates of Arctic Wetland Extent Using Ground Penetrating Radar
AGU Fall Meeting Abstracts, Dec 1, 2010
Arctic wetlands are an important terrestrial carbon reservoir, a potential sink for atmospheric C... more Arctic wetlands are an important terrestrial carbon reservoir, a potential sink for atmospheric CO2 as well as a significant source of CH¬4. We collected approximately 2 km of ground-penetrating-radar profiles across nine wetlands to supplement or borehole-based study of Holocene wetland formation in northern Manitoba. Data were acquired using a SIR-3000 radar unit (Geophysical Survey Systems Incorporated) and analyzed using
A freshwater diatom species, Stauroneis kingstonii sp. nov., is described from cypress-tupelo wet... more A freshwater diatom species, Stauroneis kingstonii sp. nov., is described from cypress-tupelo wetlands of the Cache River, Arkansas, USA. Stauroneis kingstonii can be distinguished from other Stauroneis species by its narrow lanceolate shape, high length:breadth ratio, coarse areolae and striae, and lateral raphe bounded by a broad axial area and straight proximal raphe ends. The diatom is currently known only from the Cache River Watershed and found living benthic or epiphytic on submerged bald cypress and water tupelo tree bark, in slightly acidic, and fresh to slightly brackish waters.
We studied the St. Croix River from May to September 2000, sampling the water with surface plankt... more We studied the St. Croix River from May to September 2000, sampling the water with surface plankton net tows. We found low water, low flow, and a warm environment and observed new surface plankton. We report a red alga. The surface plankton also contained the alga genera Oedegonium, Hvdrodictvon, Elakatothrix, Selenastrurn, Tetraedon, Ouadrimla, and Xanthidinium for the first time in our years of study. We also observed Svnura, a chrysophyte, which had not been observed previously. We found many suctorian and amoeboid forms in the plankton, and we report the first continuous surface plankton observations of tardigrades.
Pairing Modern and Paleolimnological Approaches to Evaluate the Nutrient Status of Lakes in Upper Midwest National Parks
Journal of The American Water Resources Association, Sep 26, 2016
Understanding what constitutes a reference (background) nutrient condition for lakes is important... more Understanding what constitutes a reference (background) nutrient condition for lakes is important for National Park Service managers responsible for preserving and protecting aquatic resources. For this study we characterize water quality conditions in 29 lakes across four national parks, and compare their nutrient status to U.S. Environmental Protection Agency (USEPA) nutrient reference criteria and alternative criteria recently proposed by others. Where appropriate we also compare the nutrient status of these 29 lakes to state or tribal nutrient reference criteria or standards. For lakes that exceed reference criteria we investigate physical and chemical patterns, and for a subset of lakes compare modern nutrient conditions to paleolimnological (i.e., diatom‐inferred [DI]) nutrient reconstructions. Many lakes exceeded USEPA nutrient reference criteria, but met alternative less restrictive criteria. Modern nutrient conditions were also largely consistent with DI historic (pre‐1900) nutrient conditions. Lakes exceeding alternative nutrient criteria and with elevated nutrient levels relative to DI historic conditions were mostly small, shallow, and dystrophic; continued attention to their nutrient dynamics and biological response is warranted. Coupling modern and paleolimnological data offer an innovative and scientifically defensible approach to understand long‐term nutrient trends and provide greater context for comparison with reference conditions.
Proposals for a terminology for diatom sexual reproduction, auxospores and resting stages
Diatom Research, Sep 1, 2013
ABSTRACT The past few decades have brought about a significant expansion in our understanding of ... more ABSTRACT The past few decades have brought about a significant expansion in our understanding of the diatom life cycle, particularly its sexual part. Presented here is a set of proposals for the terminology of processes and structures associated with sexual reproduction and for the resting stages of diatoms, some of which have at times been confused with each other. The proposals fill the void present in widely used publications offering standardized terminology related to diatom frustule micro-architecture.
bioRxiv (Cold Spring Harbor Laboratory), Apr 12, 2023
Our understanding of drivers of cyanobacterial harmful algal blooms (cHABs) is evolving, but it i... more Our understanding of drivers of cyanobacterial harmful algal blooms (cHABs) is evolving, but it is apparent that not all lakes are created equal. Nitrogen (N) is an important component of all cHABs and is crucial for cyanotoxin production. It is generally assumed that external nitrogen inputs are the primary N source for cHABs. However, in northern lakes, nitrogen inputs are typically low, and suggests that internal nitrogen cycling, through heterotrophic organic matter decomposition or nitrogen fixation, may play a significant role in cHAB development and sustainment. Using Lake of the Woods as a testbed, we quantified nutrients, cyanotoxins, nitrogen fixation, and the microbial community in the southern extent of the lake. During our temporal study, inorganic nitrogen species (NO3 -+NO2 -and NH4 + ) were either at very low concentrations or below detection, while phosphorus was in excess. These conditions resulted in nitrogen-deficient growth and thereby favored nitrogen fixing cyanobacterial species. In response, nitrogen fixation rates increased exponentially throughout the summer and coincided with the Aphanizomenon sp. bloom. Despite nitrogen limitation, microcystin, anatoxin, saxitoxin, and cylindrospermopsin were all detected, with microcystin being the most abundant cyanotoxin detected. Microcystin concentrations were highest when free nitrogen was available and coincided with an increase in Microcystis. Together, our work suggests that internal nitrogen dynamics are responsible for the dominance of nitrogen fixing cyanobacteria and that additions of nitrogen may increase the likelihood of other cyanobacterial species, currently at low abundance, to increase growth and cyanotoxin production.
We examined palatability of 37 species of nonencrusting macroalgae from the Antarctic Peninsula. ... more We examined palatability of 37 species of nonencrusting macroalgae from the Antarctic Peninsula. This represents approximately 30% of the entire antarctic macroalgal flora and 75% of the 49 nonencrusting species we collected. Organic extracts from most species were also prepared and mixed into artificial foods. We examined palatability using feeding bioassays with three common, macroalgaconsuming animals (an omnivorous antarctic rockfish, Notothenia coriiceps; an omnivorous sea star, Odontaster validus; and a herbivorous amphipod, Gondogenia antarctica). Thallus pieces from 23 of 34 macroalgal species tested with the fish (68%) were rejected. Of the 23 species rejected as thallus, organic extracts of 16 were bioassayed using the fish with 9 (56%) unpalatable. Thallus pieces from 21 of 36 macroalgal species tested with the sea star (58%) were rejected. Of the 21 species rejected as thallus, organic extracts of 20 were bioassayed using the sea stars and 14 (70%) were unpalatable. Overall, 28 of the 37 species assayed as thallus (76%) were rejected by either or both the fish and sea stars. The amphipod assay was not suitable for use with thallus but was utilized with organic extracts of 23 macroalgal species that were rejected as thallus by either or both the fish and sea stars. Of these, 14 (61%) of the species' extracts were rejected by the amphipods. Unpalatability was highest among the brown algae examined with only an ephemeral, ectocarpoid species not rejected as thallus out of 10 species tested. Of the remaining nine brown algal species, six of seven tested were also unpalatable as extracts, including all the ecologically dominant, perennial species in the area. We conclude that unpalatability to herbivores is common in antarctic macroalgae and that chemical defenses may play an important role in the unpalatability of many algal species (NSF OPP9814538, OPP9901076).
... Cody, WC Cohn, S. A. Com@re, P. Conley, DJ Conrad, C. Cooper, S. R. Corsi, D. Cox, E. J. Craw... more ... Cody, WC Cohn, S. A. Com@re, P. Conley, DJ Conrad, C. Cooper, S. R. Corsi, D. Cox, E. J. Crawford, R. M. Czamecki, D. B ... SM Frohlich, F. Fryxell, G. A. Garbary, DJ Garbe-Schonberg, C.-D. Garcia-Baptista, M. Garcia, J. Gardner, C. (see also Honeywill, C.) Garza, SA Gasse, F ...
Diets of the benthic amphipod Diporeia in southern Lake Michigan before and after the dreissenid invasion
Journal of Great Lakes Research, Apr 1, 2021
Abstract Diporeia spp. were a key component of the Great Lakes benthos, converting the pelagic al... more Abstract Diporeia spp. were a key component of the Great Lakes benthos, converting the pelagic algal rain to secondary production, which is critical for Great Lakes fishes. However, Diporeia declines since the 1980s have been rapid and widespread. While there are temporal relationships between Diporeia declines and spread of zebra and quagga mussels, establishing a mechanistic link has been difficult. Diporeia declines may result from competition for food resources with dreissenid mussels; however, conflicting evidence suggests food limitation may not be the direct link. To test food limitation, we analyzed gut contents of Diporeia collected between the 1980s and 2009 from two deep (>100 m) and one nearshore station (~50 m depth) in southern Lake Michigan. We further analyzed sediment cores from the same stations to resolve relationships among food resources, Diporeia diet, and diet selectivity during pre- and post-dreissenid invasion. In spring, pre-dreissenid Diporeia fed selectively and exclusively on large (Stephanodiscus) and filamentous centric diatoms (Aulacoseira). Diporeia diets showed significant shifts during the 2000s to greater proportions of small centric and araphid diatoms, coincident with Diporeia declines and offshore expansion of quagga mussels. Sediment cores recorded declines in Aulacoseira and large Stephanodiscus from 1960 to 2009 and increases in small centrics after dreissenid introduction. Accounting for high selectivity in springtime Diporeia diets, community changes in sediment records are consistent with changes observed in Diporeia diets and suggest Diporeia declines have been exacerbated by a shift from more nutritious and highly preferred diatom species to less nutritious and negatively selected species.
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