Brian Roberts

Brian Roberts
Louisiana Universities Marine Consortium · Research

PhD

About

67
Publications
7,653
Reads
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1,626
Citations
Introduction
Current research in the Roberts Lab is broadly focused in three areas: 1) ecosystem ecology and biogeochemistry (particularly focused on terrestrial-aquatic and community-ecosystem linkages along the aquatic continuum), 2) human-induced environmental impacts on aquatic ecosystems, and 3) restoration ecology. Our research team is currently involved in projects in multiple ecosystem types including headwater streams, rivers, baldcypress swamps, salt marshes, estuaries, and coastal oceans.
Additional affiliations
March 2017 - present
Louisiana Universities Marine Consortium
Position
  • Managing Director
January 2015 - present
Louisiana Universities Marine Consortium
Position
  • Professor (Associate)
August 2007 - January 2015
Louisiana Universities Marine Consortium
Position
  • Professor (Assistant)
Education
August 1997 - December 2003
Cornell University
Field of study
  • Ecology and Evolutionary Biology
August 1995 - May 1996
Boston University / Marine Biological Laboratory
Field of study
  • Marine Biology
August 1991 - May 1995
College of William and Mary
Field of study
  • Biology and Philosophy

Publications

Publications (67)
Article
Nature-based coastal defense using bivalve reefs provides a potentially self-sustaining approach for regions facing high coastal land loss, relative sea level rise and increasing frequency and intensity of storms. Success of such nature-based coastal defense depends on the reef-building species' life history, habitat requirements, and ability to th...
Article
Hydrology and salinity regimes of many impounded wetlands are manipulated to provide seasonal habitats for migratory waterfowl, with little-known consequences for ecosystem structure and function. Managed hydrology can alter ecosystems by directly changing soil properties and processes and by influencing plant community dynamics. Additionally, mana...
Article
Full-text available
Salt marshes are globally important sites of carbon burial, but microbial processes in their soil produce potent greenhouse gases such as carbon dioxide (CO2) and methane (CH4) that can be released back to the atmosphere. Although a great deal is known about how shifting seasons, tides, and salinity influence salt marsh greenhouse gas emissions, li...
Article
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Louisiana estuaries are important habitats in the northern Gulf of Mexico, a region undergoing significant and sustained human- and climate-driven changes. This paper synthesizes data collected over multiple years from four Louisiana estuaries – Breton Sound, Terrebonne Bay, the Atchafalaya River Delta Estuary, and Vermilion Bay – to characterize t...
Article
Salt marshes are globally important sites of carbon burial, but microbial processes in their soil produce potent greenhouse gases such as carbon dioxide (CO 2) and methane (CH 4) that can be released back to the atmosphere. Although a great deal is known about how shifting seasons, tides, and salinity influence salt marsh greenhouse gas emissions,...
Article
Estuarine ecosystem balance typically relies on strong food web interconnectedness dependent on a relatively low number of resident taxa, presenting a potential ecological vulnerability to extreme ecosystem disturbances. Following the Deepwater Horizon (DwH) oil spill disaster of the northern Gulf of Mexico (USA), numerous ecotoxicological studies...
Article
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Estuarine ecosystem balance typically relies on strong food web interconnectedness dependent on a relatively low number of resident taxa, presenting a potential ecological vulnerability to extreme ecosystem disturbances. Following the Deepwater Horizon (DwH) oil spill disaster of the northern Gulf of Mexico (USA), numerous ecotoxicological studies...
Article
Smooth cordgrass Spartina alterniflora and Atlantic ribbed mussels Geukensia demissa have a mutualism whereby S. alterniflora provides substrate and shade for G. demissa while G. demissa enhances S. alterniflora growth and drought tolerance. Together, these species im - prove salt marsh stability and function. To better understand if a similar rela...
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Few studies have focused on broad scale biogeographic patterns of ammonia oxidizers in coastal systems, yet understanding the processes that govern them is paramount to understanding the mechanisms that drive biodiversity, and ultimately impact ecosystem processes. Here we present a meta-analysis of 16 years of data of ammonia oxidizer abundance, d...
Article
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Marine oil spills continue to be a global issue, heightened by spill events such as the 2010 Deepwater Horizon spill in the Gulf of Mexico, the largest marine oil spill in US waters and among the largest worldwide, affecting over 1,000 km of sensitive wetland shorelines, primarily salt marshes supporting numerous ecosystem functions. To synthesize...
Article
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Estuarine and coastal geomorphology, biogeochemistry, water quality, and coastal food webs in river-dominated shelves of the Gulf of Mexico (GoM) are modulated by transport processes associated with river inputs, winds, waves, tides, and deepocean/continental shelf interactions. For instance, transport processes control the fate of river-borne sedi...
Article
Coarse woody debris (CWD) addition is a restoration technique that has been used to reduce effects of landscape disturbance on instream habitat. However, efficacy of this technique for improving ecosystem condition is not well established, in part because monitoring designed to evaluate long-term efficacy is rare. We assessed the effectiveness of C...
Article
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Landscape theory for food web architecture (LTFWA) suggests that food webs are hierarchically organized with larger consumers coupling energy from different habitats that would otherwise be functionally isolated. Empirical tests of this theory remain rare and support differs among terrestrial, freshwater, and marine systems. Saltmarshes and their a...
Article
Full-text available
We evaluated the ecological effectiveness of an in-stream restoration project involving coarse woody debris (CWD) additions to streams along an upland soil and vegetation disturbance gradient at the Fort Benning Military Installation near Columbus, GA. We examined short-term (immediate effectiveness) and longer-term (sustainability) responses to CW...
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Bioindicator species are commonly used as proxies to help identify the ecological effects of oil spills and other stressors. However, the utility of taxa as bioindicators is dependent on understanding their trophic niche and life history characteristics, as these factors mediate their ecological responses. Seaside sparrows ( Ammospiza maritima) and...
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Anthropogenic nutrient inputs fuel eutrophication and hypoxia ([O2] < 2 mg L−1), threatening coastal and near shore environments across the globe. The world’s second largest anthropogenic coastal hypoxic zone occurs annually along the Louisiana (LA) shelf. Springtime loading of dissolved inorganic nitrogen (DIN) from the Mississippi River, combined...
Article
Assimilation wetlands are natural, non-constructed, wetlands that are used for the removal of nutrients from treated municipal wastewater. This passive process is comparatively less expensive than other conventional forms of tertiary treatment of wastewater, making it desirable for municipalities. Assimilation wetlands are monitored for a number of...
Article
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Oil spills threaten the structure and function of ecological communities. The Deepwater Horizon spill was predicted to have catastrophic consequences for nearshore fishes, but field studies indicate resilience in populations and communities. Previous research indicates many marsh fishes exhibit avoidance of oil contaminated areas, representing one...
Preprint
Full-text available
Oil spills threaten the structure and function of ecological communities. In the northern Gulf of Mexico, the 2010 Deepwater Horizon spill was among the largest marine disasters in history. While many predicted catastrophic consequences for nearshore fishes, field studies indicate surprising resilience in populations and communities. One potential...
Article
Salt marshes are important sites of nitrogen cycling and removal that straddle the land/ocean interface, allowing them to intercept human-derived nitrogen before it reaches coastal waters where it causes problems like hypoxia and harmful algal blooms. In 2010, the Deepwater Horizon oil spill released an estimated five million barrels of crude oil i...
Article
We characterized ammonia‐oxidizing archaea (AOA) and bacteria (AOB) from salt marsh sediments in the Gulf of Mexico over 5 years to identify environmental drivers of nitrifying community patterns following the Deepwater Horizon oil spill. Samples were collected from oiled and unoiled sites in July of 2012‐2016 from 12 marshes spanning three regions...
Article
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Net community production (NCP) in the surface water of the northern Gulf of Mexico (nGOM) and its coupling with the CO2 system were examined during the productive spring season. NCP was estimated using multiple approaches: (1) underway O2 and Ar ratio, (2) oxygen changes during light/dark bottle oxygen incubations, and (3) non-conservative changes...
Article
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High‐accuracy spectrophotometric pH measurements were taken during a summer cruise to study the pH dynamics and its controlling mechanisms in the northern Gulf of Mexico in hypoxia season. Using the recently available dissociation constants of the purified m‐cresol purple (Douglas & Byrne, 2017, https://doi.org/10.1016/j.marchem.2017.10.001; Müller...
Preprint
Full-text available
Net community production (NCP) in the surface mixed layer of the northern Gulf of Mexico (nGOM) and its coupling with the CO2 system were examined during the productive spring season. NCP was estimated using multiple approaches: (1) underway O2 and Ar ratio, (2) light/dark bottle oxygen incubations, and (3) non-conservative changes in dissolved ino...
Article
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The doi for the dataset mentioned in the acknowledgements is incorrectly cited as doi: https://doi.org/10.7266/N7SF2T32. The correct doi for this dataset is https://doi.org/10.7266/N7NZ85M4.
Article
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The salt marsh periwinkle (Littoraria irrorata) is a common and often abundant mollusk in marshes of the Gulf and Atlantic coasts of the United States. Several studies have focused on the effects of periwinkles on Spartina alterniflora production and the effects of oil on periwinkle survivability, yet the general ecology of the snail has been under...
Article
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Predictions of how salt marsh primary production and carbon storage will respond to environmental change can be improved through detailed datasets documenting responses to real-world environmental variation. To address a shortage of detailed studies of natural variation, we examined drivers of Spartina alterniflora stem allometry and productivity i...
Article
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The processes and biomass that characterize any ecosystem are fundamentally constrained by the total amount of energy that is either fixed within or delivered across its boundaries. Ultimately, ecosystems may be understood and classified by their rates of total and net productivity and by the seasonal patterns of photosynthesis and respiration. Suc...
Article
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Fundulus grandis (Baird and Girard), the Gulf Killifish, is an abundant species throughout the marshes of the northern Gulf of Mexico. Its wide distribution and high site fidelity makes it an ideal indicator species for brackish and salt marshes, which experience a variety of anthropogenic disturbances. Despite the ecological, commercial, and scien...
Article
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Dissolved organic carbon (DOC) is of primary importance to marine ecosystems and the global carbon cycle. Stable carbon (δ13C) and radiocarbon (Δ14C) isotopic measurements are powerful tools for evaluating DOC sources and cycling. However, the isotopic signature of DOC in the Gulf of Mexico (GOM) remains almost completely unknown. Here we present t...
Article
Identifying key taxa in the response of ecosystems to perturbations relies on quantifying both their sensitivity to stressors and their importance in the overall web of interactions. If sensitive taxa occupy key network positions, then they may decrease the capacity of ecosystems to resist perturbations. Despite widespread concern for coastal marsh...
Article
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The Mississippi River (MR) serves as the primary source of freshwater and nutrients to the northern Gulf of Mexico (nGOM). Whether this input of freshwater also enriches microbial diversity as the MR plume migrates and mixes with the nGOM serves as the central question addressed herein. Specifically, in this study physicochemical properties and pla...
Article
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The recent oil spill in the Gulf of Mexico had significant effects on microbial communities in the Gulf, but impacts on nitrifying communities in adjacent salt marshes has not been investigated. We studied persistent effects of oil on ammonia-oxidizing archaeal (AOA) and bacterial (AOB) communities and their relationship to nitrification rates and...
Article
Benthic respiration and nutrient flux rates were quantified during four distinct periods (spring peak in river discharge, summer period of offshore hypoxia, autumn period after breakdown of offshore hypoxia, and the non-hypoxic winter period) over an annual cycle in the Atchafalaya River Delta Estuary (ARDE). The overall mean benthic respiration ra...
Article
We quantified nitrification potential and ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) abundances in 13 salt marshes in three regions across southeast Louisiana (Terrebonne Bay, western and eastern regions of Barataria Bay). Seven marshes were oiled following the 2010 Deepwater Horizon oil spill, and six sites were unoiled m...
Article
Full-text available
As coastal wetlands subside worldwide, there is an urgency to understand the hydrologic drivers and dynamics of plant production and peat accretion. One incidental test of the effects of high rates of discharge on forested wetland production occurred in response to the 2010 Deepwater Horizon Incident, in that all diversions in Louisiana were operat...
Article
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Marsh-resident fishes play important roles as both predators and prey in coastal systems, influence secondary production, and are important trophic links to adjacent coastal waters. As such, they also serve as sentinel species in efforts to understand the magnitude and implications of anthropogenic habitat disturbance or degradation. An evaluation...
Article
On 20 April 2010, the Deepwater Horizon drilling rig lost well control while drilling at the Macondo prospect in the Gulf of Mexico. At the time of the Macondo blowout, the academic scientific community was ill prepared to initiate and rapidly conduct the necessary coordinated interdisciplinary studies of the environments around the discharge area.
Conference Paper
Background/Question/Methods Stream metabolism, the measurement of primary productivity (GPP) and ecosystem respiration (ER) in stream ecosystems, is an important measure of stream health and indicator of climatic and local environmental change. Long-term, continuous monitoring of stream metabolism can enable better understanding of the integrated...
Article
Background/Question/Methods Stream metabolism, the measurement of primary productivity (GPP) and ecosystem respiration (ER) in stream ecosystems, is an important measure of stream health and indicator of climatic and local environmental change. Long-term, continuous monitoring of stream metabolism can enable better understanding of the integrated a...
Article
The Coastal Waters Consortium (CWC) led by Louisiana Universities Marine Consortium is one of eight Gulf of Mexico Research Initiative research consortia. The CWC focuses on: oil transport and fate, chemical evolution and biological degradation, and environmental effects.The following is an overview of a portion of the research conducted within the...
Article
Full-text available
[1] Phosphorus (P) biogeochemistry has been studied in multiple wetland ecosystems, though few data exist on P sorption in U.S. Gulf Coast marshes. There also is a limited understanding of how oil spills in coastal zones can influence P dynamics in wetland soils. In this study, we measured P sorption potential, using the P sorption index (PSI), soi...
Conference Paper
Background/Question/Methods Recent advances in dissolved oxygen sensing and modeling have made continuous measurements of whole-stream metabolism relatively easy to make, allowing ecologists to quantify and evaluate stream ecosystem health at expanded temporal and spatial scales. Long-term monitoring of continuous stream metabolism will enable a b...
Article
Background/Question/Methods Recent advances in dissolved oxygen sensing and modeling have made continuous measurements of whole-stream metabolism relatively easy to make, allowing ecologists to quantify and evaluate stream ecosystem health at expanded temporal and spatial scales. Long-term monitoring of continuous stream metabolism will enable a be...
Conference Paper
Applying ramped pyrolysis 14C analysis to particulate organic carbon (POC) constrains on the spectrum of radiocarbon ages in the POC. We summarize a multi-year sampling effort on both the Mississippi Atchafalaya River System (MARS), in which several different discharge regimes were sampled, and the Narayani River in Nepal, for application of this n...
Article
Applying ramped pyrolysis radiocarbon analysis to suspended river sediments, we generate radiocarbon (14C) age spectra for particulate organic carbon (POC) from the lower Mississippi-Atchafalaya River system (MARS) to better understand a major river system’s role in carbon transport. Ramped pyrolysis 14C analysis generates age distributions of bulk...
Article
Traditional methods for investigating stream solute biogeochemistry measure longitudinal rates of uptake by increasing either the concentration or isotopic composition of solutes. These methods cannot be applied to dissolved organic matter (DOM) because we cannot replicate the heterogeneous native DOM pool. We explored an alternative approach, atte...
Article
Biogeochemically, the role of rivers in transporting carbon to long-term sedimentary reservoirs is important to regulating atmospheric CO2 on several geologic time scales. Physically, sediment transport processes link carbon transport and depositional potential at different flow regimes. In the deltaic depositional setting, both types of processes...
Article
1. Light and nutrients play pivotal roles in determining the growth of autotrophs, yet the potential for synergistic interactions between the two resources in algal communities is poorly understood, especially in stream ecosystems. In this study, light and phosphorus were manipulated in large experimental streams to examine resource colimitation an...
Article
Although regional and global models of nitrogen (N) cycling typically focus on nitrate, dissolved organic nitrogen (DON) is the dominant form of nitrogen export from many watersheds and thus the dominant form of dissolved N in many streams. Our understanding of the processes controlling DON export from temperate forests is poor. In pristine systems...
Article
The Mississippi-Atchafalaya River System (MARS) transports over 40% (4.0 x 109 kg) of the United States' annual input of total organic carbon (OC) from the terrestrial to the marine environment. Assessing the MARS's exact role in the global carbon cycle is challenging because of its temporal variability (i.e. high discharge events and low flow regi...
Article
1. The light : nutrient hypothesis (LNH) states that algal nutrient content is determined by the balance of light and dissolved nutrients available to algae during growth. Light and phosphorus gradients in both laboratory and natural streams were used to examine the relevance of the LNH to stream periphyton. Controlled gradients of light (12–426 μm...
Article
Full-text available
Delivery of water, sediments, nutrients, and organic matter to stream ecosystems is strongly influenced by the catchment of the stream and can be altered greatly by upland soil and vegetation disturbance. At the Fort Benning Military Installation (near Columbus, Georgia), spatial variability in intensity of military training results in a wide range...
Article
Some expected changes in climate resulting from human greenhouse gas emissions are clear and well documented, but others may be harder to predict because they involve extreme weather events or heretofore unusual combinations of weather patterns. One recent example of unusual weather that may become more frequent with climate change occurred in earl...
Article
Simultaneous gradients of phosphorus and light were applied in experimental streams to develop quantitative relationships between these two important abiotic variables and the growth and composition of benthic microalgae. Algal biovolume and whole-stream metabolism responded hyperbolically to phosphorus enrichment, increasing approximately two-fold...
Article
We performed three experiments in indoor streams and one experiment in a natural stream to investigate the effects of growth factors on {delta}{sup 13}C levels in benthic microalgae. In the indoor streams, algae grown under conditions of high light and high phosphorus had {delta}{sup 13}C values that were 16% higher than those in algae grown under...
Article
Full-text available
1] A growing body of evidence demonstrates the importance of in-stream processing in regulating nutrient export, yet the influence of temporal variability in stream metabolism on net nutrient uptake has not been explicitly addressed. Stream water DIN and SRP concentrations in Walker Branch, a first-order deciduous forest stream in eastern Tennessee...
Article
Full-text available
Headwater streams are key sites of nutrient and organic matter processing and retention, but little is known about temporal variability in gross primary production (GPP) and ecosystem respiration (ER) rates as a result of the short duration of most metabolism measurements in lotic ecosystems. We examined temporal variability and controls on ecosyst...
Article
In this study, two main hypotheses were addressed. (1) Bacteria contribute proportionally less than autotrophs to ecosystem respiration as trophic status increases. This hypothesis was examined in a pond phosphorus-fertilization experiment and two microcosm nutrient-fertilization experiments. (2) The relative contribution of autotrophs to ecosystem...
Article
Despite the importance of O2 in biogeochemical processes, relatively few environmental studies have incorporated stable isotope information to assess the origins and cycling of this gas. A major limitation to the routine use of δ18O has been the cost and complexity associated with traditional off-line preparation, dual-inlet techniques. A gas chrom...