Geology topics

Leah Kammel

Publications and source records attributed to Leah Kammel.

4 recordsLinked to original sources

USGS2023

Hydrodynamics structure plankton communities and interactions in a freshwater tidal estuary

Drivers of phytoplankton and zooplankton dynamics vary spatially and temporally in estuaries due to variation in hydrodynamic exchange and residence time, complicating efforts to understand controls on food web productivity. We conducted approximately monthly (2012–2019; n = 74) longitudinal sampling at 10 fixed stations along a freshwater tidal terminal channel in the San Francisco Estuary, California, characterized by seaward to landward gradients in water residence time, turbidity, nutrient concentrations, and plankton community composition. We used multivariate autoregressive state space (MARSS) models to quantify environmental (abiotic) and biotic controls on phytoplankton and mesozooplankton biomass. The importance of specific abiotic drivers (e.g., water temperature, turbidity, nutrients) and trophic interactions differed significantly among hydrodynamic exchange zones with different mean residence times. Abiotic drivers explained more variation in phytoplankton and zooplankton dynamics than a model including only trophic interactions, but individual phytoplankton–zooplankton interactions explained more variation than individual abiotic drivers. Interactions between zooplankton and phytoplankton were strongest in landward reaches with the longest residence times and the highest zooplankton biomass. Interactions between cryptophytes and both copepods and cladocerans were stronger than interactions between bacillariophytes (diatoms) and zooplankton taxa, despite contributing less biovolume in all but the most landward reaches. Our results demonstrate that trophic interactions and their relative strengths vary in a hydrodynamic context, contributing to food web heterogeneity within estuaries at spatial scales smaller than the freshwater to marine transition.

California↗

USGS2022

Stream corridor and upland sources of fluvial sediment and phosphorus from a mixed urban-agricultural tributary to the Great Lakes

Like many impaired Great Lakes tributaries, Apple Creek, Wisconsin (119 km 2 ) has Total Maximum Daily Load (TMDL) targets for reducing suspended sediment and total phosphorus by 51.2 % and 64.2 %, respectively. From August 2017 - October 2018, a stream sediment budget and fingerprinting integrated study was conducted to quantify upland and stream corridor sources of suspended sediment and sediment-bound phosphorus. Phosphorus concentrations varied among source groups and fluvial sediments, with higher concentrations among suspended sediment and cropland soils. Eroding streambanks identified in the stream corridor sediment budget accounted for 100 % of the TMDL Soil and Water Assessment Tool (SWAT) suspended sediment load but only 20 % of the total phosphorus load. Fine-grained streambed sediment equated to approximately-three years of modeled suspended sediment load but only one third of total phosphorus load. The two primary sources of fine-grained streambed sediment were streambanks and cropland, with relative streambank contributions increasing with downstream direction and watershed area. The relative proportion of suspended sediment varied by season and streamflow; however, cropland and streambank erosion accounted for 54 % and 23 % of the suspended sediment when weighted by of the proportion for representative streamflow. Urban land was a source in the upper watershed, but the signature was sequestered by a mid-watershed detention basin. Contributions from construction sites were higher in the fall 2018, likely corresponding to increased activity following a wet spring. These integrated techniques helped describe sources, transport, and sinks of fluvial sediment and phosphorus throughout the watershed at a range of spatial and temporal scales.

Wisconsin↗

USGS2021

Assessment of multiple ecosystem metabolism methods in an estuary

Ecosystem metabolism is a key ecological attribute and easy to describe, but quantifying metabolism in estuaries is challenging. Properly scaling measurements through time and space requires consideration of hydrodynamics and mixing water from heterogeneous sources, making any estimation uncertain. Here, we compared three methods for modeling ecosystem metabolism in a portion of the Sacramento-San Joaquin Delta. Metabolism estimates based on laboratory incubations, continuous in situ buoys, and an oxygen isotope approach all indicated the system was net heterotrophic, and calculated rates were comparable in magnitude when averaged over the 2-month study. Daily metabolic rates based on in situ buoys were the most variable, likely due to horizontal and vertical advection and poor portrayal of the dissolved oxygen budget. After temporally averaging in situ buoy estimates or smoothing the dissolved oxygen time series for tidal effects, rates were more comparable to the other methods, which may be necessary to account for tidal advection and unbalanced contributions from subhabitats within the metabolic footprint. Incubation-based rates represent the finest temporal and spatial scale and only account for pelagic processes, which may explain why incubation-based rates were lower than the other two methods. The oxygen isotope method provided temporally and spatially integrated rates that were bracketed by the other two methods and may be a valuable tool in systems matching the model requirements. Because uncertainty arises in each method from a number of assumptions and scaling calculations, the resolution of metabolic rates in estuaries is likely coarser and more variable than in other aquatic ecosystems.

California↗

USGS2019

Stream corridor sources of suspended sediment and phosphorus from an agricultural tributary to the Great Lakes

Fine-grained sediment and phosphorous are major contaminants in the Great Lakes and their tributaries. Plum Creek, Wisconsin (92 km2), a tributary to the Lower Fox River, has a Total Maximum Daily Load (TMDL) requiring reductions of suspended sediment and phosphorus loading by 70% and 77%, respectively. In 2016-18, an integrated sediment fingerprinting and stream corridor-based sediment budget study was conducted to help quantify upland and stream corridor sources of suspended sediment and phosphorus at a loads monitoring station on Plum Creek. Sediment fingerprinting results indicated that the proportion of upland and stream corridor sources of suspended sediment in Plum Creek varied by season and the amount of runoff; however, bank and gully erosion accounted for 51% and 24% of the suspended sediment annual load, with one or both sources present in all seasons. The next most common source was roadside ditches (11%), which was also present in all seasons. Cropland and woodland sources accounted for small proportions of the suspended sediment, with cropland mainly in summer and woodland in winter, spring, and summer. Relative source proportions for sediment-bound phosphorus were similar to suspended sediment but made up less of the overall loading because on average 27% of the phosphorus load resides in the dissolved phase. Soft fine-grained streambed sediment had source signatures of mainly bank, gully, and ditches (ordered by decreasing proportion). Results from the field-based rapid geomorphic assessment supported the sediment fingerprinting results and in general showed that the amount of bank erosion increases in a downstream direction. The high proportion of sources from banks and gullies is due, in part, to a 20-km long, deeply entrenched valley and steep eroding bluffs between the majority of cropland and the Plum Creek water monitoring station.

Wisconsin↗