KSU Symphony Orchestra, Concerto Winners Concert

KSU School of Music presents Concerto Winners Concert with KSU Symphony Orchestra.https://digitalcommons.kennesaw.edu/musicprograms/1235/thumbnail.jp

Competition for nutrients and light: testing advances in resource competition with a natural phytoplankton community

A key challenge in ecology is to understand how nutrients and light affect the biodiversity and community structure of phytoplankton and plant communities. According to resource competition models, ratios of limiting nutrients are major determinants of species composition. At high nutrient levels, however, species interactions may shift to competition for light, which might make nutrient ratios less relevant. The "nutrient-load hypothesis" merges these two perspectives, by extending the classic model of competition for two nutrients to include competition for light. Here, we test five key predictions of the nutrient-load hypothesis using multispecies competition experiments. A marine phytoplankton community sampled from the North Sea was inoculated in laboratory chemostats provided with different nitrogen (N) and phosphorus (P) loads to induce either single resource limitation or co-limitation of N, P, and light. Four of the five predictions were validated by the experiments. In particular, different resource limitations favored the dominance of different species. Increasing nutrient loads caused changes in phytoplankton species composition, even if the N:P ratio of the nutrient loads remained constant, by shifting the species interactions from competition for nutrients to competition for light. In all treatments, small species became dominant whereas larger species were competitively excluded, supporting the common view that small cell size provides a competitive advantage under resource-limited conditions. Contrary to expectation, all treatments led to coexistence of diatoms, cyanobacteria and green algae, resulting in a higher diversity of species than predicted by theory. Because the coexisting species comprised three phyla with different photosynthetic pigments, we speculate that niche differentiation in the light spectrum might play a role. Our results show that mechanistic resource competition models that integrate nutrient-based and light-based approaches provide an important step forward to understand and predict how changing nutrient loads affect community composition

Hook length biases and general linear partition inequalities

Motivated in part by hook-content formulas for certain restricted partitions in representation theory, we consider the total number of hooks of fixed length in odd versus distinct partitions. We show that there are more hooks of length $2$, respectively $3$, in all odd partitions of $n$ than in all distinct partitions of $n$, and make the analogous conjecture for arbitrary hook length $t \geq 2$. We also establish additional bias results on the number of gaps of size $1,$ respectively $2$, in all odd versus distinct partitions of $n$. We conjecture similar biases and asymptotics, as well as congruences for the number of hooks of fixed length in odd distinct partitions versus self-conjugate partitions. An integral component of the proof of our bias result for hooks of length $3$ is a linear inequality involving $q(n)$, the number of distinct partitions of $n$. In this article we also establish effective linear inequalities for $q(n)$ in great generality, a result which is of independent interest. Our methods are both analytic and combinatorial, and our results and conjectures intersect the areas of representation theory, analytic number theory, partition theory, and $q$-series. In particular, we use a Rademacher-type exact formula for $q(n),$ Wright's circle method, modularity, $q$-series transformations, asymptotic methods, and combinatorial arguments.Comment: 36 page

From Ecological Stoichiometry to Biochemical Composition: Variation in N and P Supply Alters Key Biosynthetic Rates in Marine Phytoplankton

One of the major challenges in ecological stoichiometry is to establish how environmental changes in resource availability may affect both the biochemical composition of organisms and the species composition of communities. This is a pressing issue in many coastal waters, where anthropogenic activities have caused large changes in riverine nutrient inputs. Here we investigate variation in the biochemical composition and synthesis of amino acids, fatty acids (FA), and carbohydrates in mixed phytoplankton communities sampled from the North Sea. The communities were cultured in chemostats supplied with different concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) to establish four different types of resource limitations. Diatoms dominated under N-limited, N+P limited and P-limited conditions. Cyanobacteria became dominant in one of the N-limited chemostats and green algae dominated in the one P-limited chemostat and under light-limited conditions. Changes in nutrient availability directly affected amino acid content, which was lowest under N and N+P limitation, higher under P-limitation and highest when light was the limiting factor. Storage carbohydrate content showed the opposite trend and storage FA content seemed to be co-dependent on community composition. The synthesis of essential amino acids was affected under N and N+P limitation, as the transformation from non-essential to essential amino acids decreased at DIN:DIP ≤ 6. The simple community structure and clearly identifiable nutrient limitations confirm and clarify previous field findings in the North Sea. Our results show that different phytoplankton groups are capable of adapting their key biosynthetic rates and hence their biochemical composition to different degrees when experiencing shifts in nutrient availability. This will have implications for phytoplankton growth, community structure, and the nutritional quality of phytoplankton as food for higher trophic levels

Exploring the Efficacy of Nile Red in Microplastic Quantification: A Costaining Approach

The presence of microplastic particles ([less than]5 mm) in the environment has generated considerable concern across public, political, and scientific platforms. However, the diversity of microplastics that persist in the environment poses complex analytical challenges for our understanding of their prevalence. The use of the dye Nile red to quantify microplastics is increasingly common. However, its use in microplastic analysis rarely accounts for its affinity with the breadth of particles that occur in environmental samples. Here, we examine Nile red’s ability to stain a variety of microplastic particles and common natural and anthropogenic particles found in environmental samples. To better constrain microplastic estimates using Nile red, we test the coapplication of a second stain that binds to biological material, 4′,6-diamidino-2-phenylindole (DAPI). We test the potential inflation of microplastic estimates using Nile red alone by applying this costaining approach to samples of drinking water and freshwater. The use of Nile red dye alone resulted in a maximum 100% overestimation of microplastic particles. These findings are of particular significance for the public dissemination of findings from an emotive field of study

2015 KSU Concerto Competition Final Round

KSU School of Music presents 2015 KSU Concerto Competition Final Round.https://digitalcommons.kennesaw.edu/musicprograms/1169/thumbnail.jp

Stable coexistence of equivalent nutrient competitors through niche differentiation in the light spectrum

Niche?based theories and the neutral theory of biodiversity differ in their predictions of how the species composition of natural communities will respond to changes in nutrient availability. This is an issue of major environmental relevance, as many ecosystems have experienced changes in nitrogen (N) and phosphorus (P) due to anthropogenic manipulation of nutrient loading. To understand how changes in N and P limitation may impact community structure, we conducted laboratory competition experiments using a multispecies phytoplankton community sampled from the North Sea. Results showed that picocyanobacteria (Cyanobium sp.) won the competition under N limitation, while picocyanobacteria and nonmotile nanophytoplankton (Nannochloropsis sp.) coexisted at equal abundances under P limitation. Additional experiments using isolated monocultures confirmed that Cyanobium sp. depleted N to lower levels than Nannochloropsis sp., but that both species had nearly identical P requirements, suggesting a potential for neutral coexistence under P?limited conditions. Pairwise competition experiments with the two isolates seemed to support the consistency of these results, but P limitation resulted in stable species coexistence irrespective of the initial conditions rather than the random drift of species abundances predicted by neutral theory. Comparison of the light absorption spectra indicates that coexistence of the two species was stabilized through differential use of the underwater light spectrum. Our results provide an interesting experimental example of modern coexistence theory, where species were equal competitors in one niche dimension but their competitive traits differed in other niche dimensions, thus enabling stable species coexistence on a single limiting nutrient through niche differentiation in the light spectrum

Seasonal and habitat-based variations in vertical export of biogenic sea-ice proxies in Hudson Bay

Despite their wide use in past sea-ice reconstructions, the seasonal, habitat and species-based sources of sedimentary sea-ice proxies are poorly understood. Here, we conduct direct observations of the community composition of diatoms, dinoflagellate cysts and highly branched isoprenoid lipids within the sea ice, water column, sediment traps and sediment surface in the Belcher Islands Archipelago, Hudson Bay throughout spring 2019. We find that Arctic diatom and dinoflagellate cysts species commonly used as sea-ice proxies appear to be only indirectly linked to sea-ice conditions, and that the sediment assemblages of these groups overrepresent summertime pelagic blooms. Species contributing to the diverse sea-ice diatom communities are rare in the sediment. Dinoflagellate cysts form a typical Arctic assemblage in the sediment, although they are virtually absent in the sea ice and water column in spring. We also find that certain highly branched isoprenoid lipids that were previously considered indicators of open water, can be produced in sea-ice. We conclude that contextual knowledge and a multiproxy approach are necessary in reconstruction, encouraging further studies on the sources and controls of sea-ice proxy production in different geographic areas

Mock theta functions and related combinatorics

In this paper we add to the literature on the combinatorial nature of the mock theta functions, a collection of curious $q$-hypergeometric series introduced by Ramanujan in his last letter to Hardy in 1920, which we now know to be important examples of mock modular forms. Our work is inspired by Beck's conjecture, now a theorem of Andrews, related to Euler's identity: the excess in the number of parts in all partitions of $n$ into odd parts over the number of partitions of $n$ into distinct parts is equal to the number of partitions with only one (possibly repeated) even part and all other parts odd. We establish Beck-type identities associated to partition identities due to Andrews, Dixit, and Yee for the third order mock theta functions $\omega(q), \nu(q)$, and $\phi(q)$. Our proofs are both analytic and combinatorial in nature, and involve mock theta generating functions and combinatorial bijections