J. Val Klump

A hypothesis for the origin of perylene based on its low abundance in sediments of Green Bay, Wisconsin

Abstract Perylene, a polycyclic aromatic hydrocarbon (PAH) that is common in sediments, is believed to originate principally from anaerobic diagenesis of organic matter, but its precursor material remains enigmatic. We have investigated the formation of perylene in a dated sediment core from Green Bay, WI. Comparisons of sedimentary profiles of perylene, anthropogenic PAHs, land-plant-derived hydrocarbons, and aquatic contributions of organic matter rule out a specific industrial, terrigenous, or aquatic precursor for perylene. Instead, perylene seems to be formed from any kind of organic matter as a consequence of a specific type of microbial activity in sub-bottom sediments. Despite an abundance of organic matter, the amount of perylene is low in Green Bay and in other organic-carbon-rich lake sediments. The abundant availability of organic matter that stimulates microbial activity in Green Bay sediments would seem to favor perylene formation in such sediments. We therefore hypothesize that the microorganisms responsible for perylene formation do not compete successfully with those that flourish in sediments rich in organic matter. Perylene formation consequently does not become significant until deeper in sediments after the more-reactive types of organic matter have been consumed.

Biogeochemical cycling in an organic-rich coastal marine basin. 5. Sedimentary nitrogen and phosphorus budgets based upon kinetic models, mass balances, and the stoichiometry of nutrient regeneration

Abstract The rapid rates of sediment accumulation (~ 10–20 cm/yr) in the recently formed Cape Lookout Bight, North Carolina, have resulted in the deposition of approximately 157 moles of carbon, 14 moles of nitrogen and 1.3 moles of phosphorus, per square meter annually. The metabolism of the organic matter in these anoxic sediments is dominated by sulfate reduction and fermentation reactions. Sedimentary nitrogen and phosphorus budgets are estimated using 3 related approaches: 1) a kinetic model of solid phase diagenesis; 2) direct measurements of nutrient burial and regeneration; and 3) nutrient recycling rates estimated from annual rates of sulfate reduction and the SO 4 :NH 4 and SO 4 :PO 4 stoichiometry of nutrient regeneration. The mass balances derived agree reasonably well and indicate that approximately 30% of the total nitrogen and 15% of the total phosphorus deposited in these sediments are recycled. The kinetics of nutrient regeneration are rapid. The mean residence time for recycled nutrients within the sediment is 4 to 6 months for nitrogen and 1.5 to 2 years for phosphorus. Nearly 60% of the total nitrogen regeneration and 90% of the total phosphorus regeneration occur during the 4 month summer period of June through September. Nitrogen regeneration, like carbon, appears to be controlled by the microbially-mediated metabolism of labile organic matter. The greater asymmetry and lower percent turnover in phosphorus cycling is apparently due to changes in its solubility under oxidized and reduced conditions and selective regeneration prior to deposition.

Distribution of Hydrophobic Organic Compounds between Dissolved and Particulate Organic Matter in Green Bay Waters

Abstract Water samples freshly collected from southern Green Bay were innoculated with radiolabelled hydrophobic organic compounds (HOC) and, after equilibration, separated into particle bound, dissolved organic matter (DOM) bound and freely dissolved phases. Ambient suspended matter (2.7–28ppm) and dissolved organic carbon (5.2–11.5 ppm) were high in concentration relative to the open Great Lakes, but HOC distribution coefficients were not significantly different between Green Bay and previously measured open Great Lakes values. HOC in the particle phase ranged from 3 % for 4-MCB to 53 % for BaP and DDT. HOC associated with DOM was generally higher than for open lake samples, and ranged from 2% for 2,2′,5,5′-TCB to 26.5% for 4-MCB.

Freshwater suspended sediments and sewage are reservoirs for enterotoxin-positive Clostridium perfringens.

ABSTRACT The release of fecal pollution into surface waters may create environmental reservoirs of feces-derived microorganisms, including pathogens. Clostridium perfringens is a commonly used fecal indicator that represents a human pathogen. The pathogenicity of this bacterium is associated with its expression of multiple toxins; however, the prevalence of C. perfringens with various toxin genes in aquatic environments is not well characterized. In this study, C. perfringens spores were used to measure the distribution of fecal pollution associated with suspended sediments in the nearshore waters of Lake Michigan. Particle-associated C. perfringens levels were greatest adjacent to the Milwaukee harbor and diminished in the nearshore waters. Species-specific PCR and toxin gene profiles identified 174 isolates collected from the suspended sediments, surface water, and sewage influent as C. perfringens type A. Regardless of the isolation source, the beta2 and enterotoxin genes were common among isolates. The suspended sediments yielded the highest frequency of cpe-carrying C. perfringens (61%) compared to sewage (38%). Gene arrangement of enterotoxin was investigated using PCR to target known insertion sequences associated with this gene. Amplification products were detected in only 9 of 90 strains, which suggests there is greater variability in cpe gene arrangement than previously described. This work presents evidence that freshwater suspended sediments and sewage influent are reservoirs for potentially pathogenic cpe-carrying C. perfringens spores.

Variations in Sediment Accumulation Rates and the Flux of Labile Organic Matter in Eastern Lake Superior Basins

Abstract Benthic environments in Lake Superior are variable and dynamic. The complex topography and morphology of eastern Lake Superior results in a variety of depositional environments, from shallow coastal bays to deep profundal basins. Direct observations of bottom types and collection of sediments across the gradient in environments reveal benthic systems that range in sediment accumulation rates from ∼1.7 mm per year to virtually zero net long-term accumulation. Diagenetic modeling of organic carbon and nitrogen under steady state conditions indicate that 15% to 40% of the organic carbon and nitrogen deposited is recycled into the overlying water. This “metabolizable” fraction has a residence time in the sediment column estimated to be 30 to 60 years for organic carbon and 15 to 30 years for nitrogen. Concentration gradients of total dissolved inorganic carbon, ammonium, and oxygen in sediment pore waters yield fluxes of remineralized carbon and nitrogen across the sediment-water interface consistent with diagenetically modeled fluxes. Spatial variability in sediment accumulation patterns, however, is great, particularly in the deep, steep relief basins in the open lake. Here, distances of a few kilometers can radically alter deposition patterns. Evidence of aperiodic bottom currents were observed in the deepest charted basin of the lake as extensive fields of sediment ripples over hard, compacted relict silt and clays. While no currents were observed in these summertime dives, it is assumed that storms during isothermal conditions generate suffficient bottom currents at depth to very effectively scour the bottom. Differences in sediment metabolism appear to be determined by the flux of labile organic matter to the bottom coupled to the physical processes of sedimentation, resuspension, and horizontal transport.

Dynamics of dissolved and particulate phosphorus influenced by seasonal hypoxia in Green Bay, Lake Michigan.

Despite major investments in point source reductions, portions of the Great Lakes, like Green Bay, remain hypereutrophic and are subject to persistent seasonal hypoxia. Phosphorus (P) is generally a limiting nutrient in the Great Lakes ecosystem, but not all P species are equally bioavailable, and the dynamics of nutrients and their correlation to algal bloom remain poorly characterized, in part, due to a lack of adequate quantification of P chemical speciation. During summer 2014, water samples were collected from seasonally hypoxic Green Bay for measurements of dissolved and particulate inorganic and organic P to examine P cycling dynamics along a steep nutrient gradient ranging from Fox River inflow dominated eutrophic waters in the southern bay to mesotrophic northern waters near the bays connection with open Lake Michigan. River-derived dissolved and particulate P was quickly removed from the water column in southern Green Bay through biological uptake and sedimentation. Concentrations of phosphate or dissolved inorganic P (DIP) dramatically decreased from 828 ± 216 nM in the Fox River, comprising 57 ± 1% of the total dissolved P, to 24 ± 9 nM in northern Green Bay where dissolved organic P (DOP) became predominant (>80%). Generally low phosphate concentrations and extremely high dissolved organic C/P ratios (2090 ± 1160 in August 2014) suggested high DOP turnover rates and active transformation between DOP and DIP through organic degradation during P-limited conditions in Green Bay. Elevated DIP levels were accompanied by low dissolved oxygen in deeper waters (10-15m) of central Green Bay where hypoxia-development occurred, suggesting the release of DIP through particle regeneration under hypoxic conditions enhanced by lateral transport and sediment resuspension. High partition coefficients (Kd) of both inorganic and organic P and their significant negative correlation with suspended particulate matter concentrations indicated the particle-reactive nature of P in freshwater environments and may imply that DOP could also be bioavailable under P-limitation.

Measuring low concentrations of 234Th in water and sediment

Th/ 238 U disequilibria have been used extensively in studies of particle dynamics and the fate and transport of particle- reactive matter in marine environments. Similar work in low salinity, estuarine, and freshwater systems has not occurred primarily because the lower concentrations of both parent and daughter nuclides that are typical of these systems often render established methods for the analysis of 234 Th inadequate. The application of this radionuclide tracer technique to these systems, however, has great potential. To this end, we present a method for measuring low activities of 234 Th in relatively small samples (<200 l) using low background gas-flow proportional counters, a 229 Th yield monitor, and empirical corrections for the interferences from real and apparent betas that are emitted by other thorium isotopes and their progeny. For samples with low 234 Th/ 228 Th activity ratios, we improve upon current beta counting methodologies that rely on immediate sample counting, weak beta absorption, or multiple beta counts so that, using the analytical approach outlined here, it should be possible to measure 234 Th activities (i) as low as 1.5 dpm/total sample, (ii) up to 2 weeks after radiochemical purification of thorium, and (iii) with only one sample count for alpha and beta activity. D 2002 Elsevier Science B.V. All rights reserved.

Comparison of defecation rates of Limnodrilus hoffmeisteri Claparède (Tubificidae) using two different methods

The defecation rate of the tubificid oligochaete, Limnodrilus hoffmeisteri Claparéde was measured by using inverted and upright defecation chambers. Worms cultured using the upright method consistently produced larger amounts of feces (45 to 110%) than those in the inverted method (P < 0.01). The average defecation rate for the upright method was 0.69 ± 0.058 (95% CL) mg feces mg-1 dry weight h-1 compared with 0.41 ± 0.033 (95% CL) mg feces mg-1 dry weight h-1 for worms using the inverted method.

The Ecological Patterns of Benthic Invertebrates in a Great Lakes Coastal Wetland

Benthic macroinvertebrates were sampled in the summer of 1997 using a standard D frame kick net along a transect across the Peshtigo wetland, a river delta wetland on the coast of Green Bay, Lake Michigan, to describe the spatial and temporal dynamics of the invertebrate community. Various abiotic factors, including sedimentation rates determined from 210Pb and 137Cs as a proxy for delivery of riverine organic matter, were also measured to determine which factors influenced these dynamics. Significant decreasing gradients in dissolved oxygen and pH with distance from the river, coupled with trends in sedimentation rates, chloride, and sum nitrate (nitrate + nitrite), revealed that riverine water was mixing with wetland water up to 100 m from the wetland-river interface. Aboveground primary production and total invertebrate densities exhibited Weibull type distributions, with highest rates and numbers occurring 20 to 100 m from the Peshtigo River. Invertebrate densities were largely represented by Asellus sp. isopods (12–53%) and exhibited highest numbers in September. Invertebrate diversity at the genus level linearly decreased with distance from the river based on the Simpsons index of diversity (r2 = 0.60, p < 0.05) and the Shannon-Wiener function (r2 = 0.73, p < 0.01). Patterns observed suggest that there is an “optimal” zone for benthic invertebrates in the Peshtigo wetland 20 to 60 m from the Peshtigo River that is protected from high-energy events (e.g., storms, boating) in the Peshtigo wetland by a buffer zone (0 to 20 m) but is close enough to benefit from replenished levels of dissolved oxygen, nutrients, and organic matter delivered via the Peshtigo River.

Phosphorus dynamics in shallow eutrophic lakes: an example from Zeekoevlei, South Africa

Zeekoevlei is the largest freshwater lake in South Africa and has been suffering from hyper-eutrophic conditions since last few decades. We have used total P (TP), dissolved phosphate (PO43−), organic P (OP), calcium (Ca) and iron (Fe) bound P fractions to investigate the relevant physical, chemical and biological processes responsible for sedimentation and retention of P and to study phosphorus (P) dynamics in this shallow lake. In addition, redox proxies (V/Cr and Th/U ratios) are used to study the prevailing redox conditions in sediments. Adsorption by CaCO3 and planktonic assimilation of P are found to control P sedimentation in Zeekoevlei. Low concentration of the labile OP fraction in surface sediments restricts the release of P by bacterial remineralisation. Low molar Ca/P and Fe/P ratios indicate low P retention capacity of sediments, and P is most likely released by desorption from wind-induced resuspended sediments and mixing of pore water with the overlying water column.