Life Sciences Commons^™

Evaluating Benthic Macroinvertebrate Populations In Response To Scouring Events In The Trinity River, Ca, Liam Hay, Michael W. O'Neil, Chloe Pieper-Wasem

Environmental Science & Management Senior Capstones

River systems across California have been impacted by appurtenant structures such as dams and diversions. These structures have had an adverse impact on Benthic invertebrate (BMI) communities by regulating river systems and changing the natural hydraulic pulses that follow seasonal precipitation. Benthic invertebrates are a critical food resource for salmonids and serve as an indicator of ecosystem health. Our study was interested in seeing the effects of scouring events on BMI in the Trinity River of Trinity County, C.A. Following a large precipitation event that occurred in the region in December 2022, an influx of water entered the river through …

Host-Plant Specialization And Nesting Biology Of Anthidium Placitum (Megachilidae) In Northwest California, Christopher Pow

Cal Poly Humboldt theses and projects

Premise of the study: Although the study of bees and their pollination services has grown immensely in recent years, the natural history of most solitary bee species is still largely unknown. The goal of this study was to contribute to the natural history dossier of a late-season wool carder bee, Anthidium placitum Cresson (Megachilidae), by establishing which plants it uses as sources of nectar and pollen as well as documenting details of its flower-handling behavior, mating behavior, and nesting biology in northwestern California.

• Methods: Field observations were made at five sites in Del Norte, Humboldt, Siskiyou, and Trinity counties. …

A Comparison Of Community Structure In Regulated And Unregulated Reaches In The Upper Eel River, California, Lara Stephanie Jansen

Cal Poly Humboldt theses and projects

Flow regulation of rivers by impoundments and diversions can reduce hydrological variability. As a result, densities of algae and benthic macroinvertebrates often increase, but many sensitive taxa are lost, causing shifts across the food web. In Northern California, dams that reduce winter peak floods can result in the primary consumer community becoming dominated by grazers that are relatively invulnerable to predation, which can reduce the amount of energy transferred up the trophic levels. The steeper slope of the spring hydrograph recession limb downstream of a dam can also greatly impact instream diversity of periphyton, invertebrates and fish. The dam and …

Jeweled Spider Flies (Eulonchus Tristis) Are Important Pollinators Of Iris Bracteata, A Rare Siskiyou Mountain Endemic, Jean-Paul E. Ponte

Cal Poly Humboldt theses and projects

Little is known about the pollination biology of the Pacific Coast Irises (Iris: series Californicae, hereafter PCI), especially who visits and pollinates their flowers. In general, Iris flowers are considered bee-pollinated, however, flies in the genus Eulonchus (Acroceridae) are known to visit some PCI members. Therefore, I assessed the relative importance of Eulonchus and other insect visitors to the pollination of a rare PCI species native to the Siskiyou Mountains, I. bracteata.

Methods. I quantified pollinator importance for all flower visitors at sites in northern California and southern Oregon as the product of average visit rate and …

A Comparison Of Benthic Macroinvertebrate Assemblages Between Perennial And Intermittent Headwater Streams Of The Mattole River In Northern California, Usa, Mason S. London

Cal Poly Humboldt theses and projects

Intermittent streams are common throughout the world and comprise 60% or more of total river lengths in the conterminous United States. Despite their prevalence, intermittent streams are understudied, particularly first-order headwater streams, which are vital for maintaining the function, health and biotic diversity of river networks. In June 2016, I sampled five intermittent and five perennial headwater streams in the Mattole River watershed in northwestern coastal California, USA, to compare benthic macroinvertebrate (BMI) assemblages between intermittent and perennial streams. BMI samples were collected using a 500µm mesh D-net at eight randomly located riffles along a 150-m reach, and then composited, …