Geology topics

Daryl J. McGoldrick

Publications and source records attributed to Daryl J. McGoldrick.

4 recordsLinked to original sources

USGS2021

Legacy contaminant-stable isotope-age relationships in Lake Ontario year-class Alewife (Alosa pseudoharengus)

Alewife ( Alosa pseudoharengus ) are the preferred prey species of the top piscivore predators in the Lake Ontario food web and are an essential constituent in the bioaccumulation of persistent organic contaminants. Year-class samples collected in 2016 represent the alewife age ranges of 2015 (Age-01) sequentially dating back to 2008 (Age-08). The most abundant contaminant measured in Lake Ontario alewife (151.5 ng/g) were total polychlorinated biphenyls (PCBs), increasing at a rate of 11.8 ng/g per year on an age-averaged concentration basis. Total mercury demonstrated the largest percent increase (240%) accumulated over alewife ages of 1–8 years. Average total concentrations of the most abundant polychlorinated dibenzo-p-dioxin isomer (2378-tetrachlorinated dibenzo-p-dioxin (TCDD), 1.3 pg/g) and polychlorinated dibenzofuran isomer (2378-tetrachlorinated dibenzofuran (2378-TCDF), 6.6 pg/g) comprised most of the overall total dioxin (2.5 pg/g) and total furan concentrations (8.7 pg/g). The vast majority (69%) of alewife total toxic equivalence (TEQ) was comprised of the non-ortho coplanar PCBs. Both mammal and avian wildlife protection values based on total TEQ were uniformly exceeded for the dioxin-like compounds measured in Lake Ontario alewife. Ontogenetic dietary influences expressed a significant impact on Age-01 alewife age-contaminant relationships and age-stable isotope concentrations and trends for legacy contaminants. Total Hg and all dioxin-like contaminants did not demonstrate the Age-01 ontogenetic dietary effects found in legacy contaminants. A prominent polychlorinated naphthalene (PCN) concentration peak measured in year-class Age-04 alewife was followed by a corresponding lake trout peak 3–4 years later illustrating a unique example of trophic-level contaminant uptake and concomitant integration delay.

New York, Ohio↗

USGS2014

Ecological tracers reveal resource convergence among prey fish species in a large lake ecosystem

1. We measured stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) and fatty acid profiles in Lake Ontario alewife ( Alosa pseudoharengus ), rainbow smelt ( Osmerus mordax ), slimy sculpin ( Cottus cognatus ) and round goby ( Neogobius melanostomus ) collected from 1982 to 2008 to investigate how temporal variability in these ecological tracers can relate to ecosystem-level changes associated with the establishment of highly invasive dreissenid mussels. 2. Prey fish δ 15 N values remained relatively constant, with only slimy sculpin exhibiting a temporal increase in δ 15 N. In contrast, δ 13 C values for alewife, rainbow smelt and, especially, slimy sculpin became less negative over time and were consistent with the benthification of the Lake Ontario food web associated with dreissenids. 3. Principal components analysis revealed higher contributions of 14:0 and 16:1n-7 fatty acids and increasingly negative δ 13 C values in older samples in agreement with the greater historical importance of pelagic production for alewife, rainbow smelt and slimy sculpin. 4. Temporal declines in fatty acid unsaturation indices and Σn-3/Σn-6 ratios, and also increased 24:0/14:0 ratios for alewife, rainbow smelt and slimy sculpin, indicated the increasing importance of nearshore production pathways for more recently collected fish and resulted in values more similar to those for round goby. 5. These results indicate a temporal convergence of the food niche, whereas food partitioning has historically supported the coexistence of prey fish species in Lake Ontario. This convergence is consistent with changes in food-web processes associated with the invasion of dreissenid mussels.

Lake Ontario↗

USGS2012

Long-term impacts of invasive species on a native top predator in a large lake system

1. Declining abundances of forage fish and the introduction and establishment of non-indigenous species have the potential to substantially alter resource and habitat exploitation by top predators in large lakes. 2. We measured stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) in field-collected and archived samples of Lake Ontario lake trout ( Salvelinus namaycush ) and five species of prey fish and compared current trophic relationships of this top predator with historical samples. 3. Relationships between δ 15 N and lake trout age were temporally consistent throughout Lake Ontario and confirmed the role of lake trout as a top predator in this food web. However, δ 13 C values for age classes of lake trout collected in 2008 ranged from 1.0 to 3.9‰ higher than those reported for the population sampled in 1992. 4. Isotope mixing models predicted that these changes in resource assimilation were owing to the replacement of rainbow smelt ( Osmerus mordax ) by round goby ( Neogobius melanostomus ) in lake trout diet and increased reliance on carbon resources derived from nearshore production. This contrasts with the historical situation in Lake Ontario where δ 13 C values of the lake trout population were dominated by a reliance on offshore carbon production. 5. These results indicate a reduced capacity of the Lake Ontario offshore food web to support the energetic requirements of lake trout and that this top predator has become increasingly reliant on prey resources that are derived from nearshore carbon pathways.

Freshwater Biology↗

USGS2011

Polymethylene-interrupted fatty acids: Biomarkers for native and exotic mussels in the Laurentian Great Lakes

Freshwater organisms synthesize a wide variety of fatty acids (FAs); however, the ability to synthesize and/or subsequently modify a particular FA is not universal, making it possible to use certain FAs as biomarkers. Herein we document the occurrence of unusual FAs (polymethylene-interrupted fatty acids; PMI-FAs) in select freshwater organisms in the Laurentian Great Lakes. We did not detect PMI-FAs in: (a) natural seston from Lake Erie and Hamilton Harbor (Lake Ontario), (b) various species of laboratory-cultured algae including a green alga ( Scenedesmus obliquus ), two cyanobacteria ( Aphanizomenon flos-aquae and Synechococystis sp.), two diatoms ( Asterionella formosa , Diatoma elongatum ) and a chrysophyte ( Dinobryon cylindricum ) or, (c) zooplankton ( Daphnia spp., calanoid or cyclopoid copepods) from Lake Ontario, suggesting that PMI-FAs are not substantively incorporated into consumers at the phytoplankton–zooplankton interface. However, these unusual FAs comprised 4-6% of total fatty acids (on a dry tissue weight basis) of native fat mucket ( Lampsilis siliquoidea ) and plain pocketbook ( L. cardium ) mussels and in invasive zebra ( Dreissena polymorpha ) and quagga ( D. bugensis ) mussels. We were able to clearly partition Great Lakes' mussels into three separate groups (zebra, quagga, and native mussels) based solely on their PMI-FA profiles. We also provide evidence for the trophic transfer of PMI-FAs from mussels to various fishes in Lakes Ontario and Michigan, further underlining the potential usefulness of PMI-FAs for tracking the dietary contribution of mollusks in food web and contaminant-fate studies.

Michigan, Ontario, Prince Edward Island, Wisconsin↗