Inferences about ecological structure and function are often made using elemental or macromolecular tracers of food web structure. For example, inferences about food chain length are often made using stable isotope ratios of top predators and consumer food sources are often inferred from both stable isotopes and fatty acid (FA) content in consumer tissues. The use of FAs as tracers implies some degree of macromolecular conservation across trophic interactions, but many FAs are critically important for particular physiological functions and animals may selectively retain or extract these critical FAs from food resources. Here, we compared spatial variation in two taxa that feed on the same (or similar) food resources to assess which FAs appear to be responding to a common gradient in food resources. Filter feeding caddisflies (Family Hydropyschidae) and dreissenid mussels (Genus Dreissena) both consume seston, and had similar spatial variation in stable isotopes (C and N) across 13 sites in the Great Lakes region of North America. Only one of forty-one FAs measured showed strong spatial co-variance in these taxa (α-linolenic acid; ALA), indicating other FAs are responding to other environmental gradients in at least one of these taxa. Based on other experimental studies, ALA does appear to be driven by food availability in caddisflies, so it seems likely that ALA spatial co-variance reflects spatial variation in this food resource in this study. We conclude that inferences made using FAs as tracers of food web structure may be very sensitive to the individual taxa studied.

This data was generated from a study in which five experiments were conducted that tested whether and how dissolved chemicals might assist food recognition in two filter-feeding fishes, the silver (Hypophthalmichthys molitrix) and the bighead carp (H. nobilis). The buccal-pharngeal pumping (BPP), a behavior in which fish pump water into their buccal cavities, was observed in both silver and bighead carps after exposure to a a variety of food filtrates and mixtures. In addition, occlusion experiments to determine if the olfactory sense has a very important, but not exclusive, role in bigheaded carp feeding behaviors were conducted.

This data was generated from a study in which five experiments were conducted that tested whether and how dissolved chemicals might assist food recognition in two filter-feeding fishes, the silver (Hypophthalmichthys molitrix) and the bighead carp (H. nobilis). The buccal-pharngeal pumping (BPP), a behavior in which fish pump water into their buccal cavities, was observed in both silver and bighead carps after exposure to a a variety of food filtrates and mixtures. In addition, occlusion experiments to determine if the olfactory sense has a very important, but not exclusive, role in bigheaded carp feeding behaviors were conducted.

Fatty acid analysis is a powerful tool in food web research for estimating dietary sources in marine predators. However, the utility of fatty acids as dietary indicators from whole lipid samples, rather than from separate lipid classes, has been questioned. Samples are often collected at a single time point, precluding seasonal dietary comparisons. We investigated variations in the fatty acid composition of structural (phospholipids) and storage lipids (triacylglycerols) of Antarctic krill (Euphausia superba) using fisheries samples obtained over one year. Seasonal variation was observed in fatty acid biomarkers within triacylglycerol and phospholipid fractions of krill. Fatty acids in krill triacylglycerols (thought to better represent recent diet), reflected omnivorous feeding with highest percentages of flagellate biomarkers (18:4n-3) in summer, and diatom biomarkers (16:1n-7c) in autumn, winter and spring. Carnivory biomarkers (∑ 20:1 + 22:1 and 18:1n-9c/18:1n-7c) in krill were greater in autumn. Phospholipid fatty acids were less variable and higher in 20:5n-3 and 22:6n-3, which are essential components of cell membranes. Sterol composition did not yield detailed dietary information, but percentages of the major krill sterol, cholesterol, were significantly higher in winter and spring compared with summer and autumn. Unexpectedly, 18:4n-3 and copepod markers ∑ 20:1 + 22:1 were not strongly associated with the triacylglycerol fraction during some seasons. Krill may mobilise 18:4n-3 to phospholipids for conversion to long chain polyunsaturated fatty acids, which would have implications for its role as a dietary biomarker. For the first time, we demonstrate the dynamic seasonal relationship between specific biomarkers and krill lipid classes.

This dataset contains measures of density and biomass of the amphipod Diporeia spp. from lake-wide surveys of Lake Superior conducted in 2006, 2011, and 2016. The file also includes site information from the survey design. This dataset is associated with the following publication: Scharold, J., and T. Corry. Status of the amphipod Diporeia spp. in Lake Superior, 2006-2016. JOURNAL OF GREAT LAKES RESEARCH. International Association for Great Lakes Research, Ann Arbor, MI, USA, 47(4): 1033-1039, (2021).

This dataset contains measures of density and biomass of the amphipod Diporeia spp. from lake-wide surveys of Lake Superior conducted in 2006, 2011, and 2016. The file also includes site information from the survey design. This dataset is associated with the following publication: Scharold, J., and T. Corry. Status of the amphipod Diporeia spp. in Lake Superior, 2006-2016. JOURNAL OF GREAT LAKES RESEARCH. International Association for Great Lakes Research, Ann Arbor, MI, USA, 47(4): 1033-1039, (2021).

The Nutritional Ecology Laboratory maintains a database containing all of the biochemical data we collect. The database includes seasonal information regarding size, age, location, date, developmental stage, and maturity status of all the specimens we have examined. Samples range from phytoplankton to whales and seals. Depending on the objectives of specific studies, these data can be matched to measures of energy content, proximate, lipid class, and fatty acid composition.

This dataset contains site information, watershed land cover, water chemistry, and proportions of fatty acids for periphyton and macroinvertebrates collected from stream sites. This dataset is associated with the following publication: Whorley, S., N. Smucker, A. Kuhn, and J. Wehr. Urbanisation alters fatty acids in stream food webs. FRESHWATER BIOLOGY. Blackwell Publishing, Malden, MA, USA, 64(5): 984-996, (2019).

This dataset contains site information, watershed land cover, water chemistry, and proportions of fatty acids for periphyton and macroinvertebrates collected from stream sites. This dataset is associated with the following publication: Whorley, S., N. Smucker, A. Kuhn, and J. Wehr. Urbanisation alters fatty acids in stream food webs. FRESHWATER BIOLOGY. Blackwell Publishing, Malden, MA, USA, 64(5): 984-996, (2019).