Papers by Elizabeth W North
Journal of Shellfish Research, Jan 4, 2022
ABSTRACT The continued development of effective mark and recapture tools for marine invertebrates... more ABSTRACT The continued development of effective mark and recapture tools for marine invertebrates is required to better understand fundamental planktonic processes such as larval transport and mortality. Mass chemical marking methods provide researchers with the ability to mark large quantities of individuals at one time with reduced handling stress and costs. Although 3-day-old larvae of Crassostrea virginica (eastern oyster) have been marked with calcein (a fluorochrome dye) and recaptured, pediveligers have not been marked nor has mark retention through metamorphosis been verified. To track mark retention through metamorphosis, 12,000 pediveligers were marked for 24 and 48 h in calcein of 25 and 50 mg L–1 concentrations, and mark retention was tracked every 7 days for 4 wk. Results indicated that calcein did not affect initial settlement rates, that the distinct bands on larval shells were visible after metamorphosis, that individuals marked as larvae were positively identified up to 4 wk postsettlement without sacrificing individuals, and that lower calcein concentrations than previously documented were effective. This study demonstrates that calcein is a reliable method for marking C. virginica pediveligers and suggests that relatively low concentrations of calcein can produce marks and could reduce costs and potential harmful effects.
Journal Of Geophysical Research: Oceans, Aug 1, 2016
Although the effects of chemical dispersants on oil droplet sizes and ascent speeds are well-know... more Although the effects of chemical dispersants on oil droplet sizes and ascent speeds are well-known, the fate and transport of dispersed oil droplets of different sizes under varying hydrodynamic conditions can be difficult to assess with observations alone. We used a particle tracking model to evaluate the effect of changes in droplet sizes due to dispersant application on the short-term transport and surface expression of oil released under conditions similar to those following the 3 June 2010 riser cutting during the Deepwater Horizon event. We used simulated injections of oil droplets of varying size and number under conditions associated with no dispersant application and with dispersant application at 50% and 100% efficiency. Due to larger droplet sizes in the no-dispersant scenario, all of the simulated oil reached the surface within 7 h, while only 61% and 28% of the oil reached the surface after 12 h in the 50% and 100% dispersant efficiency cases, respectively. The length of the surface slick after 6 h was 2 km in the no-dispersant case whereas there was no surface slick after 6 h in the 100% dispersant case, because the smaller oil droplets which resulted from dispersant application had not yet reached the surface. Model results suggest that the application of dispersants at the well head had the following effects: (1) less oil reached the surface in the 6-12 h after application, (2) oil had a longer residence time in the water-column, and (3) oil was more highly influenced by subsurface transport.
CM Documents - ICES, 2000
Estimating spawning locations of the deep-sea red and blue shrimp Aristeus antennatus (Crustacea:... more Estimating spawning locations of the deep-sea red and blue shrimp Aristeus antennatus (Crustacea: Decapoda) in the northwestern Mediterranean Sea with a backward trajectory model Bring it home: An Individual-Based models (IBM) was applied based on: ❖ 3D hydrodynamic model ROMS (Shchepetkin and McWilliams, 2005). ❖ Lagrangian transport model Opendrift with backtracking abilities (Dagestad and Röhrs, 2018).
Deep-sea Research Part I-oceanographic Research Papers, Aug 1, 2021
Abstract The deep-sea red and blue shrimp Aristeus antennatus is a commercially valuable species ... more Abstract The deep-sea red and blue shrimp Aristeus antennatus is a commercially valuable species that occurs in the northwestern Mediterranean Sea where ripe females have been found in fishing areas. In the Palamos harbor, a local management plan restricts fishing in certain locations to sustain the resource. However, little is known about the dispersal of larvae; specifically, it is not known how far larvae are transported from spawning locations and if there could be mixing of larvae between different fishing areas. The objective of this study was to estimate the spawning sites of larvae collected at 35 sampling stations, evaluate uncertainty in the estimates, and determine if larvae could be exchanged between fishing areas. The spawning sites of larvae were estimated by backward simulation of larval trajectories using a 3-dimensional coupled hydrodynamic and Lagrangian transport model. The backtracked larvae were assigned temperature-dependent stage durations based on a literature review of similar species. Results of model simulations indicated that the median distances from sampling to spawning locations were 11 and 38 km when shortest and longest pelagic durations (PD) were implemented, respectively. Sensitivity studies of backward trajectories showed that distance estimates could vary by as much as 27, 3, and 8 km due to differences in simulated PD, sub-grid-scale turbulence, and advection, respectively. Larvae from 13 of the 35 sampling stations were tracked back to multiple fishing grounds, suggesting that mixing of larvae from different fishing areas could occur. For example, for the sampling stations within the restricted area of Palamos, 35% of simulated larvae came from the restricted area itself, and 0.9% and 10% of larvae came from neighboring areas to the north and south, respectively. These results suggest that larval transport may connect subpopulations of A. antennatus across different fishing areas, an idea that may help inform regional management plans.
Source code, license, example input and visualization files for beta-LTRANS-ADCIRC, a particle tr... more Source code, license, example input and visualization files for beta-LTRANS-ADCIRC, a particle tracking model that runs with ADCIRC circulation model prediction.
Marine Ecology Progress Series, Mar 21, 2019
Marine Pollution Bulletin, Jun 1, 2019
Biodegradation is important for the fate of oil spilled in marine environments, yet parameterizat... more Biodegradation is important for the fate of oil spilled in marine environments, yet parameterization of biodegradation varies across oil spill models, which usually apply constant first-order decay rates to multiple pseudocomponents describing an oil. To understand the influence of model parameterization on the fate of subsurface oil droplets, we reviewed existing algorithms and rates and conducted a model sensitivity study. Droplets were simulated from a blowout at 2000 m depth and were either treated with sub-surface dispersant injection (2% dispersant to oil ratio) or untreated. The most important factor affecting oil fate was the size of the droplets, with biodegradation contributing substantially to the fate of droplets ≤0.5 mm. Oil types, which were similar, had limited influence on simulated oil fate. Model results suggest that knowledge of droplet sizes and improved estimation of pseudo-component biodegradation rates and lag times would enhance prediction of the fate and transport of subsurface oil.
Ices Journal of Marine Science, Nov 23, 2019
Striped bass (Morone saxatilis) are anadromous fish that support an important fishery along the e... more Striped bass (Morone saxatilis) are anadromous fish that support an important fishery along the east coast of North America. In Chesapeake Bay, strong juvenile recruitment of striped bass can occur when larvae overlap with high concentrations of their zooplankton prey, but the mechanisms fostering the temporal overlap are unknown. Here, the influence of winter temperature on the peak abundances of a key prey, Eurytemora carolleeae, was estimated with a temperature-dependent developmental model. The role of these peaks in regulating striped bass recruitment was explored in three nursery areas: upper Chesapeake Bay, Choptank River, and Patuxent River. Model results indicated that cold winters delay the timing and increase the size of peak E. carolleeae spring abundance. When the model output was used in regression relationships with striped bass juvenile recruitment and freshwater discharge, the regression models explained up to 78% of annual recruitment variability. Results suggests that cold, wet winters could increase the chance of a match between striped bass larvae and high concentrations of their prey. This mechanistic link between winter temperatures and striped bass production, acting through prey dynamics, could further understanding of fish recruitment variability and indicates that warmer winters could negatively affect some striped bass populations.
Estuaries and Coasts, Jun 16, 2021
Environmental conditions in estuarine systems are undergoing significant changes resulting from c... more Environmental conditions in estuarine systems are undergoing significant changes resulting from climate change and anthropogenic inputs. Yet, information on how changing conditions structure three-dimensional habitats of living resources is not available for many important species, nor is it known how differences in physiological tolerances between species may influence this habitat volume. Hence, the objective of this study was to apply the habitat volume (HabVol) model in a proof-of-concept exercise to (1) quantify interannual changes in the volume of potential habitat for 12 species of estuarine fish and shellfish, (2) discern which parameters—temperature, salinity, or dissolved oxygen—had the most influence on potential habitat, and (3) identify which species’ habitat was most sensitive to environmental variability. Ten years of predictions from a 3D hydrodynamic and dissolved oxygen model of Chesapeake Bay was used with HabVol to estimate daily habitat volumes. Required (constrained by mortality) and optimal (related to growth) habitats were calculated for multiple life stages. The combination of physiological limitations and environmental variability had a wide range of effects that depended on a species’ physiological tolerances. While salinity and dissolved oxygen were the primary constraints on required habitat volumes, salinity and temperature had the strongest constraint on optimal habitat volumes. Predictive relationships between physiological tolerances and changes in habitat volumes were identified and could be used to estimate habitat limitation in estuaries where 3D models are unavailable. Results indicate that this habitat volume modeling approach could be used to quantify essential fish habitat and project the influence of climate change and nutrient loading on living resources.
Journal of Shellfish Research, Apr 1, 2016
Understanding the population dynamics and complete life cycle of bivalves is important for effect... more Understanding the population dynamics and complete life cycle of bivalves is important for effective management of these commercially and ecologically important organisms. Most of the literature and research on bivalves to date has focused on juvenile and adult bivalves, but much less is known about larvae. The larval stage has been difficult to study due to the lack of a rapid automated approach for identifying the species. A new technique, called ShellBi, utilizes color patterns on the larval shell under polarized light to identify bivalve larvae. The objective of our research was to review the scientific basis for ShellBi and to apply it to bivalve larvae from the Choptank River in mesohaline Chesapeake Bay, with the goal of distinguishing larvae of the eastern oyster (Crassostrea virginica) from seven other species that spawn at the same time. A digital camera and polarized light microscope was used to capture images of the larval shells of the eight species under standard and cross-polarized light. Images of C. virginica were distinguishable from those of other species based on color patterns, especially at later stages of development. These images could serve as a visual guide to distinguish larvae of C. virginica from other bivalves inhabiting mesohaline tributaries of Chesapeake Bay.
A user-friendly, web-accessible model has been developed that allows restoration practitioners an... more A user-friendly, web-accessible model has been developed that allows restoration practitioners and resource managers to easily estimate the TMDL-related benefits of oyster reef restoration per unit area, run restoration scenarios in Harris Creek, MD to optimize restoration planning and implementation, and calculate the benefits of the chosen plan. The model is rooted in scientifically defensible data and is readily transferrable to systems throughout the Chesapeake Bay and Eastern Shore. The model operates in five vertically well-mixed boxes along the main axis of the creek. Exchanges among creeks are computed using a tidal prism approach and were compared to exchanges provided from a high resolution 3D hydrodynamic model. Watershed inputs for the model were obtained for the Harris Creek sub-watershed from the Phase V Chesapeake Bay Program Watershed Model. The base model simulates daily concentrations over an annual cycle of chlorophyll-a, dissolved inorganic nitrogen (N) and phosphorus (P), dissolved oxygen, total suspended solids, the biomass of benthic microalgae, and the water column and sediment pools of labile organic carbon (C) and associated N and P. Water quality data for model forcing and calibration were obtained from the Chesapeake Bay Program, the Choptank Riverkeeper, the University of Maryland Center for Environmental Science, and the Maryland Department of Natural Resources. An oyster sub-model has been coupled to this base model and computes the volume of water filtered, removal of phytoplankton, suspended solids, and associated nutrients via filtration, recycling of nutrients and consumption of oxygen by oyster respiration, production of feces, N and P accumulation in oyster tissues and shell, oyster-enhanced denitrification, and N and P burial associated with restored reefs. The completed model is served online and operates through a web browser, enabling users to conduct scenario analysis by entering box-specific values for acres restored, restored oyster density, and restored oyster size, as well as the economic value of associated N and P removal.
Marine Pollution Bulletin, Sep 1, 2017
Biodegradation is an important process for hydrocarbon weathering that influences its fate and tr... more Biodegradation is an important process for hydrocarbon weathering that influences its fate and transport, yet little is known about in situ biodegradation rates of specific hydrocarbon compounds in the deep ocean. Using data collected in the Gulf of Mexico below 700 m during and after the Deepwater Horizon oil spill, we calculated first-order degradation rate constants for 49 hydrocarbons and inferred degradation rate constants for an additional 5 data-deficient hydrocarbons. Resulting calculated (not inferred) half-lives of the hydrocarbons ranged from 0.4 to 36.5 days. The fastest degrading hydrocarbons were toluene (k = −1.716), methylcyclohexane (k = −1.538), benzene (k = −1.333), and C1-naphthalene (k = −1.305). The slowest degrading hydrocarbons were the large straight-chain alkanes, C-26 through C-33 (k = −0.0494 through k = −0.007). Ratios of C-18 to phytane supported the hypothesis that the primary means of degradation in the subsurface was microbial biodegradation. These degradation rate constants can be used to improve models describing the fate and transport of hydrocarbons in the event of an accidental deep ocean oil spill.
Limnology and Oceanography: Methods, 2016
Bivalve larvae are small (50-400 lm) and difficult to identify using standard microscopy, thus li... more Bivalve larvae are small (50-400 lm) and difficult to identify using standard microscopy, thus limiting inferences from samples collected in the field. With the advent of ShellBi, an image analysis technique, accurate identification of bivalve larvae is now possible but rapid image acquisition and processing remains a challenge. The objectives of this research were to (1) develop a benchtop automated image acquisition system for use with ShellBi, (2) evaluate the system, and (3) create a protocol that would maintain high classification accuracies for larvae of the eastern oyster, Crassostrea virginica. The automated system decreased image acquisition time from 2-13 h to 46 min per slide and resulted in the highest classification accuracies at the lowest tested magnification (7X) and shortest image acquisition time (46 min). Quality control tests indicated that classification accuracies were sensitive to camera and light source settings and that measuring changes in light source and color channel intensities over time was an important part of quality control during routine operations. Validation experiments indicated that under proper settings, automated image acquisition coupled with ShellBi could rapidly classify C. virginica larvae with high accuracies (80-93%). Results suggest that this automated image acquisition system coupled with ShellBi can be used to rapidly image plankton samples and classify C. virginica larvae allowing for expanded capability to understand bivalve larval ecology in the field. Additionally, the automated system has application for rapidly imaging other planktonic organisms at high magnification.
Journal of Molluscan Studies, 2022
Techniques for positive re-identification of finfish are well developed and are used to estimate ... more Techniques for positive re-identification of finfish are well developed and are used to estimate vital rates, migration patterns and stock structure. Fluorochrome dyes, like nontoxic calcein, have been used with success to mark hard parts of fish and the shells of some molluscs. Yet, despite the commercial and ecological importance of the eastern oyster Crassostrea virginica, a systematic evaluation of the effectiveness of calcein for marking this species does not exist. In this study, methods that have been used for marking freshwater mussels with calcein were tested on 2-week- and 2-month-old juvenile C. virginica and on 3-year-old adult C. virginica. Individuals were immersed in 250 mg l−1 of calcein for 24 h either once (single treatment) or three times (triple treatment), and then observed to determine whether marks were visible, how long they remained visible and whether calcein influenced growth and mortality of the different age classes. Results indicated that all marked ind...
ICES Journal of Marine Science, 2019
Striped bass (Morone saxatilis) are anadromous fish that support an important fishery along the e... more Striped bass (Morone saxatilis) are anadromous fish that support an important fishery along the east coast of North America. In Chesapeake Bay, strong juvenile recruitment of striped bass can occur when larvae overlap with high concentrations of their zooplankton prey, but the mechanisms fostering the temporal overlap are unknown. Here, the influence of winter temperature on the peak abundances of a key prey, Eurytemora carolleeae, was estimated with a temperature-dependent developmental model. The role of these peaks in regulating striped bass recruitment was explored in three nursery areas: upper Chesapeake Bay, Choptank River, and Patuxent River. Model results indicated that cold winters delay the timing and increase the size of peak E. carolleeae spring abundance. When the model output was used in regression relationships with striped bass juvenile recruitment and freshwater discharge, the regression models explained up to 78% of annual recruitment variability. Results suggests ...
Journal of Shellfish Research
ABSTRACT The continued development of effective mark and recapture tools for marine invertebrates... more ABSTRACT The continued development of effective mark and recapture tools for marine invertebrates is required to better understand fundamental planktonic processes such as larval transport and mortality. Mass chemical marking methods provide researchers with the ability to mark large quantities of individuals at one time with reduced handling stress and costs. Although 3-day-old larvae of Crassostrea virginica (eastern oyster) have been marked with calcein (a fluorochrome dye) and recaptured, pediveligers have not been marked nor has mark retention through metamorphosis been verified. To track mark retention through metamorphosis, 12,000 pediveligers were marked for 24 and 48 h in calcein of 25 and 50 mg L–1 concentrations, and mark retention was tracked every 7 days for 4 wk. Results indicated that calcein did not affect initial settlement rates, that the distinct bands on larval shells were visible after metamorphosis, that individuals marked as larvae were positively identified up to 4 wk postsettlement without sacrificing individuals, and that lower calcein concentrations than previously documented were effective. This study demonstrates that calcein is a reliable method for marking C. virginica pediveligers and suggests that relatively low concentrations of calcein can produce marks and could reduce costs and potential harmful effects.
Marine Pollution Bulletin, 2019
Biodegradation is important for the fate of oil spilled in marine environments, yet parameterizat... more Biodegradation is important for the fate of oil spilled in marine environments, yet parameterization of biodegradation varies across oil spill models, which usually apply constant first-order decay rates to multiple pseudocomponents describing an oil. To understand the influence of model parameterization on the fate of subsurface oil droplets, we reviewed existing algorithms and rates and conducted a model sensitivity study. Droplets were simulated from a blowout at 2000 m depth and were either treated with sub-surface dispersant injection (2% dispersant to oil ratio) or untreated. The most important factor affecting oil fate was the size of the droplets, with biodegradation contributing substantially to the fate of droplets ≤0.5 mm. Oil types, which were similar, had limited influence on simulated oil fate. Model results suggest that knowledge of droplet sizes and improved estimation of pseudo-component biodegradation rates and lag times would enhance prediction of the fate and transport of subsurface oil.
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Papers by Elizabeth W North