Kelton W Mcmahon

Kelton W Mcmahon
University of Rhode Island | URI · Graduate School of Oceanography

Ph.D.

About

38
Publications
15,835
Reads
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2,745
Citations
Introduction
I am broadly interested in understanding what drives ecosystem structure, function, and resilience, especially in light of climate change and anthropogenic disturbance. In particular, I develop and apply compound-specific stable isotope techniques to address questions about population connectivity, trophic dynamics, and carbon flow pathways in the marine environment. My research combines fieldwork, laboratory analyses, and modeling approaches across a wide range of species and ecosystems.
Additional affiliations
October 2017 - present
University of Rhode Island
Position
  • Instructor
Description
  • OCG106G: You, Me, and Life in the Sea. An introductory gen ed (A1, B4) Grand Challenge course exploring the relationships between humans and marine biodiversity.
August 2017 - present
University of Rhode Island
Position
  • Professor (Assistant)
April 2016 - April 2016
University of California, Santa Cruz
Position
  • Lecturer
Description
  • Ocea01: The Oceans
Education
September 2005 - February 2011
Massachusetts Institute of Technology
Field of study
  • Biological Oceanography
September 2005 - February 2011
Woods Hole Oceanographic Institution
Field of study
  • Biological Oceanography
September 2001 - May 2005
Bates College
Field of study
  • Biology (Summa cum laude)

Publications

Publications (38)
Article
Full-text available
Climate change is predicted to alter marine phytoplankton communities and affect productivity, biogeochemistry, and the efficacy of the biological pump. We reconstructed high-resolution records of changing plankton community composition in the North Pacific Ocean over the past millennium. Amino acid–specific δ13C records preserved in long-lived dee...
Article
Full-text available
Coral reefs support spectacularly productive and diverse communities in tropical and sub-tropical waters throughout the world's oceans. Debate continues, however, on the degree to which reef biomass is supported by new water column production, benthic primary production, and recycled detrital carbon (C). We coupled compound-specific stable C isotop...
Article
Full-text available
Analysis of individual amino acid (AA) δ15N values is increasingly common in studies of food web architecture, movement ecology, and biogeochemical cycling. However, observations that nitrogen isotope fractionation of AAs may vary across species and trophic positions (TP) complicate the application of compound-specific stable isotope analysis (CSIA...
Article
Full-text available
Tropical marine ecosystems are under mounting anthropogenic pressure from overfishing and habitat destruction, leading to declines in their structure and function on a global scale. Although maintaining connectivity among habitats within a seascape is necessary for preserving population resistance and resilience, quantifying movements of individual...
Article
Full-text available
1. Analysis of stable carbon isotopes is a valuable tool for studies of diet, habitat use and migration. However, significant variability in the degree of trophic fractionation (Δ13CC-D) between consumer (C) and diet (D) has highlighted our lack of understanding of the biochemical and physiological underpinnings of stable isotope ratios in tissues....
Article
Full-text available
Compound‐specific stable isotope analysis of individual amino acids (CSIA‐AA) has emerged as a transformative approach to estimate consumer trophic positions (TPCSIA) that are internally indexed to primary producer nitrogen isotope baselines. Central to accurate TPCSIA estimation is an understanding of beta (β) values—the differences between trophi...
Article
Full-text available
Characterizing energy flow and trophic linkages is fundamental to understanding the functioning and resilience of Arctic ecosystems under increasing pressure from climate change and anthropogenic exploitation. We used carbon and nitrogen stable isotopes to examine trophic dynamics and the relative contribution of terrestrial organic matter, water c...
Article
Full-text available
The Southern Ocean is in an era of significant change. Historic overharvesting of marine mammals and recent climatic warming have cascading impacts on resource availability and, in turn, ecosystem structure and function. We examined trophic responses of sympatric chinstrap ( Pygoscelis antarctica ) and gentoo ( Pygoscelis papua ) penguins to nearly...
Article
Full-text available
Spatial refuges in peripheral habitats will become increasingly important for species persistence as climate change and other disturbances progressively impact habitat quality and assemblage compositions. However, the capacity for persistence will be determined in part by species‐specific abilities to absorb costs related to altered or decreased qu...
Article
The North Pacific Subtropical Gyre (NPSG) is the largest continuous ecosystem on Earth and is a critical component of global oceanic biogeochemical cycling and carbon sequestration. We report here multi-millennial-scale, sub-decadal-resolution records of bulk stable nitrogen (δ15N) and carbon (δ13C) isotope records from proteinaceous deep-sea coral...
Article
Full-text available
Ross seals Ommatophoca rossii are one of the least studied marine mammals, with little known about their foraging ecology. Research to date using bulk stable isotope analysis suggests that Ross seals have a trophic position intermediate between that of Weddell Leptonychotes weddellii and crabeater Lobodon carcinophaga seals. However, consumer bulk...
Article
Full-text available
Stable isotopes are important ecological tools, because the carbon and nitrogen isotopic composition of consumer tissue reflects the diet. Measurements of isotopes of individual amino acids can disentangle the effects of consumer physiology from spatiotemporal variation in dietary isotopic values. However, this approach requires knowledge of assimi...
Article
Full-text available
Antarctic marine ecosystems are spatially and temporally dynamic. Regional climate change is significantly altering the patterns and magnitudes of this dynamism with cascading impacts on biogeochemistry, productivity, and food web architecture. Isoscapes (or isotopic maps) provide a valuable analytical framework to characterize ecosystem processes...
Article
The stable isotope geochemistry of gorgonian octocoral skeletons facilitates detailed time series reconstructions of nutrient biogeochemistry. However, comparisons among reconstructions from different locations require realistic estimates of the uncertainty surrounding each measured geochemical value. Here, we determine quantitative uncertainties r...
Article
Compound-specific stable isotopes of amino acids (CSI-AA) from proteinaceous deep-sea coral skeletons have the potential to improve paleoreconstructions of plankton community composition, and our understanding of the trophic dynamics and biogeochemical cycling of sinking organic matter in the Ocean. However, the assumption that the molecular isotop...
Article
Compound-specific isotopic analysis of amino acids (CSIA-AA) has emerged in the last decade as a powerful approach for tracing the origins and fate of nitrogen in ecological and biogeochemical studies. This approach is based on the empirical observation that source amino acids (AAs)s (i.e., phenylalanine), fractionate ¹⁵N very little (< 0.5‰) durin...
Article
Full-text available
Compound-specific stable isotope analysis (CSIA) of individual amino acids (AAs) has become a powerful analytical tool in trophic ecology. Heavily fractionating “trophic” AAs (e.g., glutamic acid: Glu) provide a robust indicator of trophic transfer, while minimally fractionating “source” AAs (e.g., phenylalanine: Phe) closely reflect the δ15N value...
Article
Full-text available
Compound-specific stable isotope analysis (CSIA) of amino acids (AA) has rapidly become a powerful tool in studies of food web architecture, resource use, and biogeochemical cycling. However, applications to avian ecology have been limited because no controlled studies have examined the patterns in AA isotope fractionation in birds. We conducted a...
Article
Deep-sea proteinaceous corals represent high-resolution paleoarchives, extending biogeochemical time series far beyond recent instrumental data. While recent studies have applied compound specific amino acid δ15N (δ15N-AA) measurements of their organic skeletal layers to investigate Holocene nitrogen cycling, potential applications of amino acid δ1...
Article
Full-text available
Ecogeochemistry—the application of geochemical techniques to fundamental questions in population and community ecology—has been used in animal migration studies in terrestrial environments for several decades; however, the approach has received far less attention in marine systems. This review includes comprehensive meta-analyses of organic zooplan...
Article
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Animal movements and the acquisition and allocation of resources provide mechanisms for individual behavioural traits to propagate through population, community and ecosystem levels of biological organization. Recent developments in analytical geochemistry have provided ecologists with new opportunities to examine movements and trophic dynamics and...
Article
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This study explored the potential for otolith geochemistry in snapper (Family: Lutjanidae) to identify residency in juvenile nursery habitats with distinctive carbon isotope values. Conventional bulk otolith and muscle stable isotope analyses (SIA) and essential amino acid (AA) SIA were conducted on snapper collected from seagrass beds, mangroves,...
Article
Full-text available
Fish ecologists have used geochemical values in otoliths to examine habitat use, migration, and population connectivity for decades. However, it remains difficult to determine an unambiguous dietary δ13C signature from bulk analysis of otolith. Studies to date have focused on the aragonite component of otoliths with less attention paid to the organ...
Article
The ecological integrity of tropical habitats, including mangroves, seagrass beds and coral reefs, is coming under increasing pressure from human activities. Many coral reef fish species are thought to use mangroves and seagrass beds as juvenile nurseries before migrating to coral reefs as adults. Identifying essential habitats and preserving funct...
Chapter
Full-text available
The stable isotope composition of animal tissues can provide intrinsic tags to study the foraging and migratory ecology of predators in the open ocean. Chapter 13 (this volume) demonstrated that by comparing the isotope values of an animal and its local prey or environment, the animal’s movements can be estimated, given that isotopic variation exis...
Article
Full-text available
Stable isotope analyses (SIA) of carbon and nitrogen are used routinely in food-web studies to determine diet and trophic position. We tested several common assumptions of SIA by rearing juvenile mummichog Fundulus heteroclitus on 5 isotopically distinct diets under controlled laboratory conditions. We determined the effect of diet type and lipid e...
Article
Full-text available
The world's second largest fish, the basking shark (Cetorhinus maximus), is broadly distributed in boreal to warm temperate latitudes of the Atlantic and Pacific oceans from shallow coastal waters to the open ocean. Previous satellite archival tagging in the North Atlantic has shown that basking sharks move seasonally, are often associated with pro...
Article
Identifying patterns and drivers of natural variability in populations is necessary to gauge potential effects of climatic change and the expected increases in commercial activities in the Arctic on communities and ecosystems. We analyzed growth rates and shell geochemistry of the circumpolar Greenland smooth cockle, Serripes groenlandicus, from th...
Article
Full-text available
In order to quantify the impacts of human induced climate change on Arctic marine ecosystems it is crucial to establish high-resolution proxies to record regional environmental variability. The Barents Sea region is highly influenced by the annual recession and precession of Arctic sea ice and, as an ecosystem is extremely sensitive to seasonal to...
Article
We examined the growth rate of the circumpolar Greenland Cockle (Serripes groenlandicus) over a period of 20 years (1983-2002) from Rijpfjord, a high-Arctic fjord in northeast Svalbard (80°10′N, 22°15′E). This period encompassed different phases of large-scale climatic oscillations with accompanying variations in local physical variables (temperatu...
Article
Full-text available
We assessed the digestibility and utilization of ice algae and phytoplankton by the shallow, subtidal benthos in Ny Ålesund (Kongsfjord) on Svalbard (79° N, 12°E) using chlorophyll a (chl a), essential fatty acids (EFAs) and stable isotopes as tracers of food consumption and assimilation. Intact benthic communities in sediment cores and individuals...
Article
Full-text available
Killifish are ecologically important components of salt marsh ecosystems, but no studies have determined the importance of locally produced versus allochthonous food sources on a scale of less than multiple kilometers. The goal of our study was to examine diet and movement of the killifish,Fundulus heteroclitus, collected from a Maine salt marsh to...
Article
Ecological and geochemical analyses of bivalve shells provide potentially complimentary information on patterns and drivers of natural variability in Arctic marine populations, yet are rarely considered together. We analyzed growth rates and shell geochemistry of the Greenland Smooth Cockle (Serripes groenlandicus) from the southern Barents Sea bet...

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Project (1)
Project
Much of our understanding on how marine microplastic pollution impacts marine organisms has been derived from laboratory trials utilizing extremely high concentrations of plastics, much higher than those found in the marine environment. To understand how to manage microplastic pollution, more information is needed on how they are distributed within the marine environment and how environmentally relevant concentrations may impact marine organisms. This project aims to address these knowledge gaps.