Atmospheric deposition (AD) is a significant but poorly understood source of nutrients to many aquatic systems around the world. Accurate characterization of the nutrient budgets of aquatic systems is critical to good management decisions, so a better understanding of AD-related nutrient loads is essential, especially for water bodies where nutrient loads from atmospheric deposition are significant. Due to its large surface area, proximity to Great Basin dust sources, high values of atmospheric particulates due to inversions, and the high phosphorus content of local soils, Utah Lake, in the semi-arid Utah Valley, USA, experiences significant phosphorus loading from AD. The lake is eutrophic and has a history of impaired water quality and HABs, which has motivated significant study and debate over nutrient loads to the lake. Previous studies that measured phosphorus AD to Utah Lake showed a large portion of the AD was associated with a few high-volume deposition events, with the data exhibiting unexpectedly high peaks at some locations on a few dates. These issues cast doubt on the data. We used statistical analyses and machine learning models to characterize AD to Utah Lake. In addition to determining the distribution of AD events, we analyzed the relationship between phosphorus AD and local weather events. We used this analysis to determine whether the high phosphorus measurements were outliers due to sampling errors or represented actual conditions. Our analysis shows that AD events followed an XXX distribution, similar to the distribution of precipitation events on the lake. We found the high phosphorus deposition events were correlated with instances of high wind occurring when the ground was dry. We also observed regular cycles of higher and lower measurements throughout the year that are like measures of atmospheric particulate matter. We conclude that atmospheric phosphorus deposition on Utah Lake is episodic and driven by weather conditions around the lake, with the most important factors being the number of hours with high winds during a collection period and the percentage of those hours where the ground was dry during a collection period followed by dry deposition from particulate matter. This is an important finding for the management of Utah Lake and also has implications for the management of other eutrophic lakes in which atmospheric deposition of nutrients impacts water quality.

Sedimentation rates in sediment cores from Lavaca Bay have been high within the last 1-2 decays within the central portion of the bay, with small fluctuations from river input. Lavaca Bay is a broad, flat, and shallow (<3 m) microtidal estuary within the upper Matagorda Bay system. Marine derived sediment enters the system from Matagorda Bay, while two major rivers (Lavaca & Navidad) supply the majority of terrestrially derived sediment. With continuous sediment supply the bay showed no bathymetric change until the introduction of the shipping channel. Processes that potentially lead to sediment transport and resuspension within the bay include wind driven wave resuspension, storm surges, wind driven blowouts, and river flooding. These processes were assessed using X-radiographs, grain size profiles, and 210Pb and 137Cs geochronology of sediment diver cores. In six cores the upper 10 cm of the seabed has been physically mixed, where as the rest showed a continuous sediment accumulation rate between 0.84-1.22 cm/yr. Sidescan sonar and subbottom chirp sonar data coupled with sedimentological core and grab samples were used to map the location and delineate the sedimentary facies within the estuarine system in depths >1 m. Five sedimentary facies were identified in Lavaca Bay and adjacent bays, they are: 1) estuarine mud; 2) fluvial sand; 3) beach sand; 4) bay mouth sand; and 5) oyster biofacies. Of the five facies, Lavaca Bay consists primarily of estuarine mud (68%). Pre-Hurricane and post-Hurricane Claudette cores were obtained to observe the impact to the sedimentary processes. The north and south Lavaca Bay were eroded by 10 cm and 2-3 cm, respectively. Cox Bay and Keller Bay saw a net deposition of 2-3 cm.