Effects of drift macroalgae on sediment nitrogen cycling in Thalassia testudinum beds of St. Joseph Bay, FL

Anthropogenic nitrogen (N) loading and eutrophication can affect valuable ecosystem services and seagrass habitats by modifying structural and functional aspects of estuarine communities including increasing and prolonging macroalgae blooms. In some contexts, macroalgae may play a key role in N cycling pathways because they can alter sediment chemistry. Previous research has associated drift macroalgae blooms with elevated dissolved inorganic N concentrations in sediments as a result of increased remineralization of organic matter, but drift macroalgae effects on microbial N transformation pathways are not well understood. This study quantified the effects of macroalgae on estuarine N cycling in Thalassia testudinum seagrass beds of St. Joseph Bay, FL, on June 4, 18, and 26, 2017. Sediment physical characteristics, seagrass and macroalgae biomass measurements, and porewater chemistry were analyzed to compare sediments in areas with and without macroalgae cover. Seagrass aboveground and belowground biomass was significantly greater in areas with no macroalgae on June 18, and 26. Sediments at incubation sites with macroalgae had higher porewater sulfide and % organic matter, though this was not significant across all sites and incubation dates. Porewater sulfide concentrations were positively correlated to seagrass shoot density in areas with and without drift macroalgae. A continuous-flow incubation system for intact sediment cores amended with stable isotope additions (15NH4+ and 15NO3- ) was used to measure N transformation rates across the sediment-water interface. Results shows that DNRA (dissimilatory nitrate reduction to ammonium) rates were similar in magnitude to denitrification rates in areas with and without macroalgae, showing similar rates of N removal and recycling within sediments. Anammox rates were a minor source of N2 flux from sediments in macroalgae and no macroalgae areas, though anammox was stimulated under drift macroalgae blooms. N fixation was observed during all incubations, even in sediments with porewater NH4+ above 300 µM. Previous research in St. Joseph Bay during summer and fall had higher denitrification rates, and lower N fixation rates than this study. Presence of drift macroalgae appears to possibly alter organic matter supply during blooms that may affect seasonal sediment N cycling rates in seagrass beds. Though there were not many significant differences in N cycling rates between areas with and without drift macroalgae, data presented in this study provides baseline N transformation rates in a relatively unimpacted bay, St. Joseph Bay, FL, and is an important step in understanding how nutrient loading may alter N cycling rates in other similar systems

The Podberesky Case and Race-Based Financial Aid

The United States Supreme Court\u27s decision of May 23, 1995 not to grant certiorari and to let stand a federal court of appeal\u27s decision in Podberesky v Kirwin (1994) made headlines across the nation. The Supreme. Court has let stand a lower court\u27s findings that a race-exclusive scholarship, awarded only to African-Americans at the University of Maryland, violates the 14th Amendment to the US. Constitution and Title VI of the Civil Rights Act of 1964.1 While the decision is legally binding only in the jurisdiction of the Court of Appeals for the Fourth Circuit (the states of Maryland, North Carolina, South Carolina, Virginia, and West Virginia), it does establish a significant legal precedent. On the other hand, Department of Education guidelines, issued in February 1994, advise that race-exclusive scholarships are legal if they are designed to remedy past discrimination or to promote diversity. (Federal Register, 1994). Yet recent legal decisions have made it increasingly difficult to prove the existence of present effects of past discrimination, thereby justifying remedies, such as race-based financial aid. Financial aid administrators now wonder how to administer institutional aid programs. Colleges and universities are being advised by the American Council on Education, don\u27t do anything different from what you are doing. (Jaschik, June 2, 1995, p. A25). But Richard Samp of the Washington Legal Foundation (and Daniel Podberesky\u27s attorney) states, it would be \u27virtually impossible\u27 for colleges to meet the legal standard set by the Fourth Circuit to justify minority scholarships, and it will take only a few multi-million-dollar [damage] awards for schools to start thinking differently. (Jaschik, June 2, 1995, p. A25). The purpose of this article is to review the Podberesky decision and to discuss the implications of that decision on race-based financial aid awards

Nutrient Addition Effects on Phytoplankton Communities in the Amazon River Plume

The types and abundance of phytoplankton is largely controlled by availability of sunlight and bioavailable nutrients. Phytoplankton require essential nutrients including nitrate, phosphate, and silicate to grow, so understanding the role of these macronutrients in limiting the growth phytoplankton communitiesand the way this may differ depending on community compositionis key to understanding the controls on phytoplankton biomass and community structure. We aimed to explore how the availability of these nutrients affects the health and composition of phytoplankton communities by conducting a series of nutrient amendment experiments (NAEs) with samples from the Western Tropical North Atlantic, which is heavily influenced by the nutrient-rich, low salinity waters of the Amazon River Plume. These experiments, conducted at five locations in and around the plume, provide greater resolution and further our understanding about the ways nutrients affect communities in dynamic coastal regions

Origin of the `He/N' and `Fe II' Spectral Classes of Novae

The spectra of postoutburst novae display either He+N or Fe II lines as the most prominent non-Balmer lines at maximum light. Spectral diagnostics indicate physical conditions for 'He/N' spectra that are consistent with their origin in the white dwarf (WD) ejecta, whereas 'Fe II' spectra point to their formation in a large circumbinary envelope of gas whose origin is the secondary star. A determining parameter for which of the two types of spectra predominates may be the binary mass ratio Msec/MWD. The increasing fraction of novae that are observed to be 'hybrid' objects, where both classes of spectra appear sequentially, is explained by changing parameters in the two emitting regions during the postoutburst decline. We argue that most novae may be hybrids that show both types of spectra during decline. The emission line intensity ratio O I {\lambda}8446/{\lambda}7773 is suggested as a good density diagnostic for the ejecta, and a finding list of emission lines identified in recent spectroscopic surveys of novae is presented as an aid to future line identification work.Comment: 14 pages, 2 table

Assessing Multiple Sequence Alignments Using Visual Tools

Bioinformatics and molecular evolutionary analyses most often start with comparing DNA or amino acid sequences by aligning them. Pairwise alignment, for example, is used to measure the similarities between a query sequence and each of those in a database in BLAST similarity search, the most used bioinformatics tool (Altschul et al., 1990; Camacho et al.