Michael J. Lemke

Exploring the Sulfur Nutrient Cycle Using the Winogradsky Column

fully understand the workings of the biological world, it is important that students have a fundamental sense of the natural cycles that provide the nutrients and energy that power life, as well as a sense of how these systems evolved. Many teachers cover carbon cycles and emphasize microbial processes when reviewing the complexities of nitrogen cycling, but often the sulfur cycle, if covered, is done so briefly. There may be many reasons for this: time limitations, the element is less prevalent than others as a biological constituent, or the topic is thought to be too complex. However, teaching the sulfur cycle in conjunction with the classic Winogradsky column exercise presents the opportunity to cover several important topics simultaneously. The exercise links microbial processes, concepts of biodiversity, inorganic chemistry, biogeochemical cycling, evolution, microbiology, and microbial ecology to help meet the many demands and standards that are part of todays science classes. The Winogradsky column is a glass or clear plastic column, filled with enriched soil or sediment. When developed, it has an anaerobic lower zone and aerobic upper zone that allow growth of microorganisms under conditions similar to those found in sediments and water rich in nutrients (Sylvia et al., 1998). Often teachers simply convey the message that different microorganisms exist in different strata of the column and that some live in the aerobic and some in anaerobic zones. However, this is really where the discovery begins rather than ends! Explaining the complexity that lies within the depths of the ecosystem allows deeper insights into the microbial world. In the laboratory, the Winogradsky column demonstrates how the metabolic diversity of prokaryotes transforms sulfur, an essential constituent of living matter and an abundant element in the Earths crust (Stanier et al., 1976), to different forms with varying redox states, thus supplying nutrients and/or energy to the organism. The microbial assemblage that develops in the column spatially separates organisms into distinct layers several T

Fish community succession and biomanipulation to control two common aquatic ecosystem stressors during a large-scale floodplain lake restoration

Biomanipulation, or management actions aimed to structure biological communities to achieve certain goals, has often been used in the restoration of aquatic ecosystems. In 2000, The Nature Conservancy acquired the Emiquon Preserve, which included two former Illinois River floodplain lakes, to restore these ecosystems. Restoration included stocking to establish a native fish community commensurate with historical records. Largemouth bass (Micropterus salmoides, bass) were also introduced to control poor water clarity and invasive common carp (Cyprinus carpio, carp). We summarized fish community characteristics and tested whether bass contributed to water clarity maintenance and limited carp during 2007–2014. The fish community was dominated by species stocked in greatest abundance, 13 of 32 species initially stocked have not been collected, and species diversity increased. No carp were observed in bass diets, water clarity declined significantly, and carp relative abundance increased. Increasing water levels during 2008–2009 diffused bass predation potential upon zooplanktivorous fishes and carp and weakened potential trophic cascading interactions. Our findings suggest that water level management, greater stocking of piscivores to maintain predator densities, prevention of gizzard shad (Dorosoma cepedianum) introduction, and/or a more diverse fish community including other native piscivores may be required to achieve long-term restoration goals.

A Global eDNA Comparison of Freshwater Bacterioplankton Assemblages Focusing on Large-River Floodplain Lakes of Brazil.

With its network of lotic and lentic habitats that shift during changes in seasonal connection, the tropical and subtropical large-river systems represent possibly the most dynamic of all aquatic environments. Pelagic water samples were collected from Brazilian floodplain lakes (total n = 58) in four flood-pulsed systems (Amazon [n = 21], Araguaia [n = 14], Paraná [n = 15], and Pantanal [n = 8]) in 2011–2012 and sequenced via 454 for bacterial environmental DNA using 16S amplicons; additional abiotic field and laboratory measurements were collected for the assayed lakes. We report here a global comparison of the bacterioplankton makeup of freshwater systems, focusing on a comparison of Brazilian lakes with similar freshwater systems across the globe. The results indicate a surprising similarity at higher taxonomic levels of the bacterioplankton in Brazilian freshwater with global sites. However, substantial novel diversity at the family level was also observed for the Brazilian freshwater systems. Brazilian freshwater bacterioplankton richness was relatively average globally. Ordination results indicate that Brazilian bacterioplankton composition is unique from other areas of the globe. Using Brazil-only ordinations, floodplain system differentiation most strongly correlated with dissolved oxygen, pH, and phosphate. Our data on Brazilian freshwater systems in combination with analysis of a collection of freshwater environmental samples from across the globe offers the first regional picture of bacterioplankton diversity in these important freshwater systems.

Diversity and succession of pelagic microorganism communities in a newly restored Illinois River floodplain lake

While the success of restoration efforts frequently depends on reconstructing ecological communities, time series observations of community structure over the course of restoration are rare. Here, frequent sampling of bacterioplankton, phytoplankton, planktonic protozoa (ciliates and testaceans), and zooplankton was done along with measurements of select physical and chemical parameters during the first year of ecological restoration of Thompson Lake (TL), an Illinois River floodplain lake not connected to the river. The primary objective was to describe the microbial composition, diversity, and seasonal dynamics in TL and compare these results to similar measurements made in a nearby reference lake, river flood-pulsed Lake Chautauqua (LC). Strong seasonal patterns in bacterioplankton diversity were observed for both lakes. While TL phytoplankton diversity was lower and blooms more erratic than in LC, ciliate richness and abundance patterns were similar in both lakes. Rotifers and microcrustaceans were about 5× more abundant in TL than LC, with copepods and cladocerans exhibiting a fall abundance peak only in TL. When compared to temporal patterns of planktonic microorganisms in the reference lake (LC), the microbial dynamics in a lake recovering from decades of agriculture and drainage (TL) reflect the instability associated with early stages of ecological restoration.

Ecological Response of Floodplain Restoration to Flooding Disturbance: A Comparison of the Effects of Heavy and Light Flooding

Major floods elicit calls for more comprehensive and multi-faceted approaches to flood management. In the future, adding floodways and flood storage areas to traditional structural strategies (e.g. dams and levees) may be a viable strategy. Beyond reducing flood damages, there is growing societal interest in floodplain services, including nutrient processing and supporting fisheries and wildlife habitat. In April 2013, a record flood on the Illinois River created a natural floodplain management experiment within two restored, but disconnected floodplains. With the benefit of extensive pre-flood data at both sites, we evaluated the biological response to a minor (levee overtopping) and a major (levee failure) flooding event. Our intent was to test the ecological resilience of restored floodplains to these two alternative management scenarios. We hypothesized that a minor flood event would have little effect on ecosystem structure, whereas the major flood event would result in lower production and diversity of zooplankton; increase invasive vegetation and decrease desirable submerged and emergent aquatic vegetation; and decrease overall waterbird use. Case studies such as this are critically needed to inform policy-makers and managers of the trade-offs between alternative floodplain connectivity regimes on ecological services.

Diel Variation Related to Thermal Mixing in a Subtropical and in a North-Temperate Shallow Floodplain Lake

ABSTRACT Shallow floodplain habitats connected to large rivers undergo seasonal flooding making them integral parts of large river ecosystems. In tropical and subtropical regions, water mixing in these habitats is described as polymictic, yet little description exists for other large river floodplain lakes. In this study, the effect of thermal input on die1 mixing was compared between subtropical Garças Lake (GL)(1.2 m depth) connected to the Paraná River, Brazil and temperate Crane Lake (CL)(0.5 m depth) connected to the Illinois River, USA. Physical, chemical, and microbial variables were measured at 3 h intervals on clear, nearly windless (avg. < 1.2 m s−1) days in summer (GL, 8–9 Jan 02; CL, 8–9 Aug 02). Nocturnal, convective mixing was evident for temperature (range: GL, 28–33 °C; CL, 23–32 °C) and oxygen (range GL: 23–196%; CL: 24–200%) in each system by nightfall (1930h) and correlated with differences in nitrate and ammonia. Although total bacterial density differed between surface and bottom water samples by afternoon, it was similar at both depths by evening (CL, 2230h) or early morning (GL, 430h)Diel mixing occurred in both systems and has important implications in nutrient cycling, coupling of oxic-anoxic processes, and distribution of microbiota.