BS, Kent State University, 2018, College of Arts and Sciences / Department of Biological Sciences

Invertebrate activities at the sediment-water interface can facilitate nutrient retention, release, and transformation by changing the nature of oxygen penetration into anoxic sediments, influencing geochemical and microbial-mediated processes. By reworking sediment and conveying oxygenated surface water into deeper anoxic sediment through burrowing activities, bioturbating invertebrates influence nutrient cycling in wetlands sediments. To test the effects of bioturbators on oxygen introduction and nutrient fluxes, we investigated the impacts of two functionally different bioturbators at a range of four densities using a microcosm study. We measured sediment oxygen penetration depth at small-scale resolution using microelectrode sensors and analyzed surface water nutrients weekly over four weeks. Results indicate increased oxygen penetration in regions of normally anoxic sediment with the presence of each of the two bioturbation modes. In general, we observed negative phosphorus fluxes (i.e., into the sediment) with increasing bioturbator densities, indicating retention in the sediment due to bioturbation activities. These activities caused enough retention of phosphorus to counteract the phosphorus released by bioturbator excretion alone. There was a flux of nitrate into the surface water, likely driven by invertebrate excretion of ammonia followed by an oxidative process such as nitrification. This investigation contributes to the growing understanding of how organisms influence nutrient cycling in wetlands, which are hotspots for biogeochemical processing.

Committee: Lauren Kinsman-Costello (Advisor); Andrea Fitzgibbon (Other); David Costello (Committee Member) Subjects: Biogeochemistry; Ecology; Freshwater Ecology; Geochemistry

PHD, Kent State University, 2024, College of Arts and Sciences / Department of Biological Sciences

Freshwater aquatic ecosystems, including lakes and wetlands, provide habitat for abundant and diverse animal communities, which can have large impacts on nutrient (nitrogen [N] and phosphorus [P]) biogeochemistry. Animals play an important role in nutrient recycling in freshwater ecosystems but are infrequently considered in nutrient management. It is broadly known that animals provide nutrients via excretion and egestion, however, less is known about how animals indirectly influence nutrient retention and release through interacting with aquatic sediments, and how their nutrient contributions shape aquatic communities and ecosystem functions such as primary production. Waterbirds (i.e., ducks, geese, wading birds, cormorants) and benthic invertebrates (i.e., benthic dwelling oligochaete worms, insect larvae such as mayfly and chironomid taxa) are common in Great Lakes aquatic ecosystems, yet their roles in shaping nutrient budgets and loading are often overlooked. The overall focus of this dissertation was to understand how sediment-surface water nutrient dynamics and ecosystem processes are shaped by aquatic animals and different water oxygen conditions in a variety of Great Lakes freshwater aquatic ecosystems. We demonstrate that multiple animal groups can measurably shape nutrient dynamics with implications on other ecosystem functions. In the first study, we investigated multiple internal load contributions, including net ambient and bioturbator-mediated sediment-surface water nutrient exchange, in Sandusky Bay, Lake Erie. We found that invertebrate bioturbation supplied P and N and made up a significant component of net internal fluxes, and internal sources made up a significant proportion of the total P load in this shallow, freshwater embayment. In the second study, we examined how the late-summer hypoxic event in Lake Erie shapes sediment oxygen and redox-sensitive indicators to better understand how hypoxia stressors affect sediment conditions and processe (open full item for complete abstract)

Committee: David Costello (Advisor); Lauren Kinsman-Costello (Committee Member); Ferenc de Szalay (Committee Member); Michael Vanni (Committee Member); Allyson Tessin (Committee Member) Subjects: Biogeochemistry; Ecology; Environmental Science; Freshwater Ecology; Limnology

Master of Science (MS), Ohio University, 2021, Geological Sciences

Studies of the relationship between extant trace makers, known environmental conditions, and the morphology of their biogenic structures allow for the interpretation of continental ichnofossils. This study examined the burrowing techniques, behaviors, and trace morphologies of three extant species of burrowing beetles, Tenebrio molitor, Zophobas morio, and Phyllophaga sp., from their larval to adult life stages under normal and stressed environmental conditions in a laboratory setting. Tenebrio molitor and Z. morio burrowed using their mandibles to compact the substrate, while Phyllophaga sp., burrowed by excavation and backfilling. The three species primary behaviors were locomotion, mobile deposit feeding, intermittent resting, and pupation. Larvae burrows of T. molitor and Z. morio included open boxworks, while Phyllophaga sp. larvae generated elongate backfilled burrows which terminated in an open chamber. All three species created ovoid to ellipsoidal chambers when preparing for pupation. During their adult stage, T. molitor and Z. morio created conical traces and chambers, while Phyllophaga sp. produced loosely backfilled burrows. The environmental stresses tested were related to sediment sand and water content as well as sediment compactness. Higher trace abundance was produced in sediments with decreased sand content, increased water content, and low compactness, although trace morphologies did not change. Highly compacted substrates had little activity, but distinct trace morphologies. The total level of bioturbation, quantified with the ichnofabric index, produced by multiple specimens of each species in large enclosures filled with layered sediment varied from 1 (T. molitor and Phyllophaga sp.) to 2-5 (Z. morio). Quantitative analyses of the quantitative properties of the different traces showed that, despite having similar morphologies, the traces produced by the three species were dissimilar, but also showed variation within species. Understanding extan (open full item for complete abstract)

Committee: Daniel Hembree Ph.D (Advisor); Alycia Stigall Ph.D (Committee Member); Xizhen Schenk Ph.D (Committee Member) Subjects: Geology; Paleontology

Master of Science (MS), Bowling Green State University, 2020, Biological Sciences

As headwaters transporting agricultural runoff to streams and lakes, agricultural ditches may be a key component to reducing nutrient loading and harmful algal blooms. While conventional trapezoidal ditches are the most widely used, two stage ditches and self-forming streams are starting to be constructed as a means of management. Two stage ditches and self-forming streams may be useful for their wider floodplains, allowing slower movement of water and less erosion, promoting environments that retain and remove more nutrients than the more narrow conventional ditches. Here I examined multiple nutrient pools and fluxes (plants, invertebrates, sediments, water, and biofilm) of phosphorus and nitrogen in both May and July of 2018. I also tested the effects of isopods on nutrient cycling in ditch sediments in laboratory experiments. The results showed that ditch morphology did little to impact the concentration of nutrients, but did alter nutrient density and total nutrient retention, which was related to the width of the ditch. Plant and sediment pools were found to retain the most nutrients. Self-forming streams retained the most nutrients but supported a low biomass and diversity of invertebrates which can be important in nutrient cycling and multiple ecosystem functions. Bioturbation was found to be less important than excretion with invertebrates that rework surface sediments. Overall, my results suggest two stage ditches may balance increased nutrient retention while at the same time maintain aquatic habitat quality.

Committee: Kevin McCluney Dr. (Advisor); Enrique Gomezdelcampo Dr. (Committee Member); James Hood Dr. (Committee Member); Helen Michaels Dr. (Committee Member) Subjects: Agricultural Chemicals; Agriculture; Biology; Ecology; Geomorphology; Hydrology; Water Resource Management

BA, Oberlin College, 2019, Geology

Sediments collect in reef lagoons, and the shells within these can record changes in the environment as they accumulate. Smuggler's Cove (St. Croix, USVI) has been accumulating a sediment package for at least 5,000 years based on radiocarbon ages. Callianassid shrimp severely bioturbate this lagoon's sediment package by moving shell material into shelly, subsurface lags that have a high chance of becoming fossilized. Shell condition (taphonomy) was compared between surface and lag to see whether the lag is an accurate representation of the living surface fauna. Guild membership, taxon, and mollusk size between surface and lag assemblages were analyzed. It was found that the surface beds were more similar to each other than to lags regardless of habitat, and subsurface beds were also more like one another. The dominance of infaunal guilds and the scarcity of epifaunal guilds in the subsurface suggests that it is difficult for callianassids to bring down surface shells. The decrease in taphonomic alteration in the lower beds suggests that shrimp are not pulling shells down by size alone but rather by life guild, favoring infaunal over epifaunal organisms. Since infaunal organisms are less subject to taphonomic alteration than epifaunal ones and tend to be small, guild membership is driving the overall taphonomic signal and influences the results for species and size. Therefore, infaunal species may be overrepresented in the fossil record in these types of environments. The epifaunal surface shells on the other hand, may persist there until degraded into sand.

Committee: Karla Parsons-Hubbard (Advisor); Steven F. Wojtal (Committee Member); Dennis K. Hubbard (Committee Member) Subjects: Geology; Paleoecology; Paleontology

Doctor of Philosophy, Case Western Reserve University, 2016, Geological Sciences

Sediment is an important sink for many anthropogenic and naturally occurring contaminants in aquatic systems. Physical and biogeochemical processes near the sediment-water interface control the fate of these pollutants, which can be either buried and therefore removed from the system or returned to the water column and biosphere through a variety of processes. Sediment-water interactions are often further complicated by the presence of macrobenthos, which can both alter the physical and chemical conditions in the sediment and be affected by the presence of contaminants. This research investigated the influence of PCB pollution on the bioturbative behavior of Leptocheirus plumulosus. A significant decrease in the rate of particle and solute mixing, measured using radioactive tracers, was observed in New Bedford Harbor sediment contaminated with polychlorinated biphenyls (PCBs) and heavy metals, when compared to a control. Dose-response experiments revealed that the burrowing behavior of L. plumulosus was relatively unchanged up to about 60 mg PCB/kg d.w., above which a strong decrease in the mixing rate was observed. This work also explored the possibility of using non-toxic, fluorescent luminophores to measure 2-dimensional particle redistribution as a substitute for 1-dimensional measurements obtained with particle radiotracers. Good agreement between the two tracers was obtained for 4 marine/estuarine benthos with different styles of mixing, with the best agreement observed for the biodiffusive species. The 2-dimensional capability of the luminophore methodology helped determine whether uniform mixing assumption of the biodiffusive model, used for both tracers, was met. Finally, a new method for measuring the diffusive flux of phosphorus from sediment was developed. The method involves using Diffusive Equilibrium in Thin films (DET) to obtain high resolution overlying and pore water soluble reactive phosphorus (SRP; phosphate) concentrations. Two-dimensi (open full item for complete abstract)

Committee: Gerald Matisoff Dr. (Advisor) Subjects: Environmental Science; Geochemistry; Toxicology

Master of Science, University of Toledo, 2006, Biology (Ecology)

It is well known that invasive species, such as the dreissenid mussels in the Great Lakes, play significant roles in changing the substrate, community species composition, and habitat. This study examined the role of Dreissena, (zebra mussel, D. polymorpha and quagga mussel, D. bugensis) as an invasive “paver”, which compacts the sediment, and its effects on two native bioturbators, Hexagenia (burrowing mayflies; H. limbata and H. rigida) and unionid bivalve mollusks. Resulting consequences on sediment properties, infaunal invertebrates, and microbial community composition were analyzed. I further examined the spatial relationship between Dreissena and Hexagenia. Experiments showed that Hexagenia density increased in the presence of Dreissena, nematodes decreased, and oligochaetes and microbes were unaltered. In the absence of Dreissena, bioturbating species altered sediment water content and increased infaunal invertebrate densities, microbial activity, and microbial functional diversity. In further exploration of the relationship between Dreissena and Hexagenia, Hexagenia preferred habitat with 50-100% spatial coverage of live Dreissena clusters. These experiments thus revealed habitat facilitation by an invasive ecosystem engineer on a native ecosystem engineer, Hexagenia, with opposite effects on invertebrates, microbes, and sediment properties.

Committee: Christine Mayer (Advisor) Subjects: