Geology topics

Research about Humboldt Bay

Source-linked reports with geographic coverage including Humboldt Bay.

6 recordsLinked to original sources

USGS2024

California State Waters Map Series—Benthic habitat characterization in the region offshore Humboldt Bay, California

Coastal and Marine Ecological Classification Standard (CMECS) geoform, substrate, and biotic component geographic information system (GIS) products were developed for the California State Waters of northern California in the region offshore of Humboldt Bay. The study was motivated by interest in development of offshore wind-energy capacity and infrastructure in Federal waters offshore. This project, carried out by the U.S. Geological Survey (USGS), resulted in four data releases for individual map blocks that are part of the “California State Waters Map Series”: (1) Offshore of Arcata, (2) Offshore of Eureka, (3) Offshore of the Eel River, and (4) Offshore of Cape Mendocino. The study area consists of 436 square kilometers of multibeam echo sounder (MBES) data acquired by Fugro Pelagos, Inc., in 2007. Towed camera-sled video was acquired in 2009 and 2010 to supervise the classification of the MBES data into habitats, and single channel sparker data were collected to calculate sediment thickness above the transgressive unconformity. Using video observations of habitat as ground truth, derivatives of the MBES data were classified into 3 seafloor character types (hard-rugose, hard-flat, and soft-flat), 26 induration-slope-depth groups, and 15 geoforms. The study area substrate is predominantly soft-flat sediment (mud and fine sand) covering 73.6 percent of the area. Hard-flat substrate areas, predominantly coarse sediment in scour depressions, cover 5.4 percent of the study area. The hard-rugose substrate areas are primarily outcrops of layered sedimentary bedrock and constitute 20.9 percent of the study area. Fifteen geoforms were identified in the analysis. The predominant geoforms mirror the seafloor character results, shelf geoforms, rock outcrop geoforms, and scour depression geoforms. Rock and scour areas are restricted to the southern portion of the study area off Cape Mendocino where uplift has exposed bedrock. On the flat shelf area post-transgressive sediment varies in thickness from 1.7 meters (m) nearshore to 28.1 m offshore.

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USGS2022

A summary of water-quality and salt marsh monitoring, Humboldt Bay, California

This report summarizes data-collection activities associated with the U.S. Geological Survey Humboldt Bay Water-Quality and Salt Marsh Monitoring Project. This work was undertaken to gain a comprehensive understanding of water-quality conditions, salt marsh accretion processes, marsh-edge erosion, and soil-carbon storage in Humboldt Bay, California. Multiparameter sondes recorded water temperature, specific conductance, and turbidity at a 15-minute timestep at two U.S. Geological Survey water-quality stations: (1) Mad River Slough near Arcata, California (U.S. Geological Survey station 405219124085601) and (2) Hookton Slough near Loleta, California (U.S. Geological Survey station 404038124131801). At each station, discrete water samples were collected to develop surrogate regression models that were used to compute a continuous time series of suspended-sediment concentration from continuously measured turbidity. Data loggers recorded water depth at a 6-minute timestep in the primary tidal channels (Mad River Slough and Hookton Slough) in two adjacent marshes (Mad River marsh and Hookton marsh). The marsh monitoring network included five study marshes. Three marshes (Mad River, Manila, and Jacoby) are in the northern embayment of Humboldt Bay and two marshes (White and Hookton) are in the southern embayment. Surface deposition and elevation change were measured using deep rod surface elevation tables and feldspar marker horizons. Sediment characteristics and soil-carbon storage were measured using a total of 10 shallow cores, distributed across 5 study marshes, collected using an Eijkelkamp peat sampler. Rates of marsh edge erosion (2010–19) were quantified in four marshes (Mad River, Manila, Jacoby, and White) by estimating changes in the areal extent of the vegetated marsh plain using repeat aerial imagery and light detection and ranging (LiDAR)-derived elevation data. During the monitoring period (2016–19), the mean suspended-sediment concentration computed for Hookton Slough (50±20 milligrams per liter [mg/L]) was higher than Mad River Slough (18±7 mg/L). Uncertainty in mean suspended-sediment concentration values is reported using a 90-percent confidence interval. Across the five study marshes, elevation change (+1.8±0.6 millimeters per year [mm/yr]) and surface deposition (+2.5±0.5 mm/yr) were lower than published values of local sea-level rise (4.9±0.8 mm/yr), and mean carbon density was 0.029±0.005 grams of carbon per cubic centimeter. From 2010 to 2019, marsh edge erosion and soil carbon loss were greatest in low-elevation marshes with the marsh edge characterized by a gentle transition from mudflat to vegetated marsh (herein, ramped edge morphology) and larger wind-wave exposure. Jacoby Creek marsh experienced the greatest edge erosion. In total, marsh edge erosion was responsible for 62.3 metric tons of estuarine soil carbon storage loss across four study marshes. Salt marshes are an important component of coastal carbon, which is frequently referred to as “blue carbon.” The monitoring data presented in this report provide fundamental information needed to manage blue carbon stocks, assess marsh vulnerability, inform sea-level rise adaptation planning, and build coastal resiliency to climate change.

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USGS2022

Reproducibility and variability of earthquake subsidence estimates from saltmarshes of a Cascadia estuary

We examine fossil foraminiferal assemblages from 20 sediment cores to assess sudden relative sea-level (RSL) changes across three mud-over-peat contacts at three salt marshes in northern Humboldt Bay, California (~44.8°N, -124.2°W). We use a validated foraminiferal-based Bayesian transfer function to evaluate the variability of subsidence stratigraphy at a range of 30-6000 m across an estuary. We use the consistency in RSL reconstructions to support estimates of coseismic subsidence from megathrust earthquakes. To assess the variability of subsidence estimates, we analyzed: nine examples of the 1700 CE earthquake (average of 0.64 ±0.14 m subsidence; range of 0.24 ±0.27 to 1.00 ±0.44 m), five examples of the ca. 875 cal a BP earthquake (average of 0.43 ±0.16 m; range of 0.41 ±0.36 to 0.48 ±0.39 m), and six examples of the ca. 1120 cal a BP earthquake (average of 0.70±0.18 m; range of 0.47 ±0.36 to 0.80 ±0.49 m). Our subsidence estimate results suggest ~±0.3 m of within-site (intra-site) variability, which is consistent with previous research. We also identify inconsistencies between sites (inter-site) at northern Humboldt Bay greater than one-sigma uncertainties, driven by variable foraminiferal assemblages in the mud overlying the 1700 CE subsidence contact. Therefore, we recommend at least two quantitative microfossil reconstructions across the same stratigraphic sequence from different marsh sites within an estuary to account for estimate variability and provide increased confidence in vertical coseismic deformation estimates. Our results have broad implications for quantitative, microfossil-based reconstructions of coseismic subsidence at temperate coastlines globally.

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USGS2021

Timing and amount of southern Cascadia earthquake subsidence over the past 1700 years at northern Humboldt Bay, California, USA

Stratigraphic, lithologic, foraminiferal, and radiocarbon analyses indicate that at least four abrupt mud-over-peat contacts are recorded across three sites (Jacoby Creek, McDaniel Creek, and Mad River Slough) in northern Humboldt Bay, California, USA (∼44.8°N, −124.2°W). The stratigraphy records subsidence during past megathrust earthquakes at the southern Cascadia subduction zone ∼40 km north of the Mendocino Triple Junction. Maximum and minimum radiocarbon ages on plant macrofossils from above and below laterally extensive (>6 km) contacts suggest regional synchroneity of subsidence. The shallowest contact has radiocarbon ages that are consistent with the most recent great earthquake at Cascadia, which occurred at 250 cal yr B.P. (1700 CE). Using Bchron and OxCal software, we model ages for the three older contacts of ca. 875 cal yr B.P., ca. 1120 cal yr B.P., and ca. 1620 cal yr B.P. For each of the four earthquakes, we analyze foraminifera across representative mud-over-peat contacts selected from McDaniel Creek. Changes in fossil foraminiferal assemblages across all four contacts reveal sudden relative sea-level (RSL) rise (land subsidence) with submergence lasting from decades to centuries. To estimate subsidence during each earthquake, we reconstructed RSL rise across the contacts using the fossil foraminiferal assemblages in a Bayesian transfer function. The coseismic subsidence estimates are 0.85 ± 0.46 m for the 1700 CE earthquake, 0.42 ± 0.37 m for the ca. 875 cal yr B.P. earthquake, 0.79 ± 0.47 m for the ca. 1120 cal yr B.P. earthquake, and ≥0.93 m for the ca. 1620 cal yr B.P. earthquake. The subsidence estimate for the ca. 1620 cal yr B.P. earthquake is a minimum because the pre-subsidence paleoenvironment likely was above the upper limit of foraminiferal habitation. The subsidence estimate for the ca. 875 cal yr B.P. earthquake is less than (<50%) the subsidence estimates for other contacts and suggests that subsidence magnitude varied over the past four earthquake cycles in southern Cascadia.

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USGS2019

Changes in breeding population sizes of double-crested Cormorants Phalacrocorax auritus in the Humboldt Bay area, California, 1924–2017

To better understand recent population growth of the Double-crested Cormorant Phalacrocorax auritus along the Pacific coast of North America, we assessed long-term breeding population trends in the Humboldt Bay area, California, using aerial photographic survey data collected since 1989 as well as available prior data. The earliest documentations of breeding (but without nest counts) are from 1924, 1943, and 1947 on the outer coast near Trinidad, and from 1959 in Humboldt Bay at Old Arcata Wharf. The breeding population increased from 188 nests (376 breeding birds) at one colony in 1961 to ~ 350 nests (700 breeding birds) at four colonies by 1980, and then to peaks of nearly 1,700 nests (3,400 breeding birds) in 1997 and 2004 at eight colonies. Breeding was documented at 13 coastal colonies through 2017. The population increased 100% (9 % per annum) from 1989 to 1997, decreased during the strong 1998 El Niño, and rebounded by 2004. After the 2004 peak, three years of available data indicated slight population decline. For the entire 1989–2017 period, the population increased by 91% (2% per annum). Artificial habitats in Humboldt Bay allowed most of the population growth, especially Teal Island, which was colonized in 1993 and became the largest colony in all but one year thereafter. Nest totals on the outer coast decreased, likely because of movements to the Humboldt Bay colonies, which are closer to main foraging areas, and because of competition for nesting space with Common Murres Uria aalge at one colony (False Cape Rocks). Future growth of the population in the Humboldt Bay area appears limited by the availability of disturbance-free breeding habitat. Declines may occur if artificial habitats are lost.

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USGS2015

Predicting effects of environmental change on a migratory herbivore

Changes in climate, food abundance and disturbance from humans threaten the ability of species to successfully use stopover sites and migrate between non‐breeding and breeding areas. To devise successful conservation strategies for migratory species we need to be able to predict how such changes will affect both individuals and populations. Such predictions should ideally be process‐based, focusing on the mechanisms through which changes alter individual physiological state and behavior. In this study we use a process‐based model to evaluate how Black Brant ( Branta bernicla nigricans ) foraging on common eelgrass ( Zostera marina ) at a stopover site (Humboldt Bay, USA), may be affected by changes in sea level, food abundance and disturbance. The model is individual‐based, with empirically based parameters, and incorporates the immigration of birds into the site, tidal changes in availability of eelgrass, seasonal and depth‐related changes in eelgrass biomass, foraging behavior and energetics of the birds, and their mass‐dependent decisions to emigrate. The model is validated by comparing predictions to observations across a range of system properties including the time birds spent foraging, probability of birds emigrating, mean stopover duration, peak bird numbers, rates of mass gain and distribution of birds within the site: all 11 predictions were within 35% of the observed value, and 8 within 20%. The model predicted that the eelgrass within the site could potentially support up to five times as many birds as currently use the site. Future predictions indicated that the rate of mass gain and mean stopover duration were relatively insensitive to sea level rise over the next 100 years, primarily because eelgrass habitat could redistribute shoreward into intertidal mudflats within the site to compensate for higher sea levels. In contrast, the rate of mass gain and mean stopover duration were sensitive to changes in total eelgrass biomass and the percentage of time for which birds were disturbed. We discuss the consequences of these predictions for Black Brant conservation. A wide range of migratory species responses are expected in response to environmental change. Process‐based models are potential tools to predict such responses and understand the mechanisms which underpin them.

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