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opencc-zeroJan 2020View details →

Exploring variability in the diet of depredating sperm whales in the Gulf of Alaska through stable isotope analysis

Sperm whales interact with commercially important groundfish fisheries offshore in the Gulf of Alaska (GOA). This study aims to use stable isotope analysis to better understand the trophic variability of sperm whales and their potential prey, and to use dietary mixing models to estimate the importance of prey species to sperm whale diets. We analyzed tissue samples from sperm whales and seven potential prey (five groundfish and two squid species). Samples were analyzed for stable carbon and nitrogen isotope ratios, and diet composition was estimated using Bayesian isotopic mixing models. Mixing model results suggest that an isotopically combined sablefish/dogfish group, skates, and rockfish make up the largest proportion of sperm whale diets (35%, 28% and 12%) in the GOA. The top prey items of whales that interact more frequently with fishing vessels consisted of skates (49%) and the sablefish/dogfish group (24%). This is the first known study to provide an isotopic baseline of adult male sperm whales and these adult groundfish and offshore squid species, and to assign contributions of prey to whale diets in the GOA. This study provides information to commercial fishermen and fisheries managers to better understand trophic connections of important commercial species.

opencc-zeroJan 2024View details →

Stable isotope analysis reveals shifts in diet of a breeding montane bird

Insectivorous breeding birds require access to high quality prey to produce a successful nest. A lack of suitable prey (e.g., low nutritional quality or low invertebrate availability) that fulfill energetic demands can negatively affect nestling growth and survival. In high elevation ecosystems (>900 m), cooler and wetter climates can have negative influences on invertebrate availability which in turn can affect bird diets. Yet we lack studies of how diet composition changes over elevation gradients. Here, we assessed the diet of Swainson's Thrush (Catharus ustulaus) within the White Mountains, New Hampshire using stable isotope analysis and DNA metabarcoding. We found that the proportion of detritivore arthropods in thrush diets increased with elevation, while the proportion of predatory arthropods and overall niche-width declined. Further, we show that high-elevation thrushes had diets that were different in composition, but similar in diversity to thrushes at low-elevation sites. Lepidoptera, araneae, and coleoptera were important diet items across all elevations, but increases in woodlice and ghost spiders contributed to familial-level differences in diet composition at high-elevation sites. This research suggests montane breeding birds may be consuming low quality prey (i.e., millipedes) at high elevation sites, due to either availability or preference. With considerations due to climate change, environmental contamination, and residual impacts on the diet and nutrient availability for breeding montane birds, understanding diet composition changes along environmental gradients can provide information on nutrient availability for species that breed in harsh climatic conditions. Future work on invertebrate availability and nutritional composition, daily energy expenditure, and dietary niche would help contribute to important context to conserving montane birds within these sensitive, high elevation systems.

opencc-zeroSep 2022View details →

Diet composition based on stable isotopic analysis of fecal samples revealed the preference of Black-faced Spoonbill (Platalea minor) for natural wetlands and fishponds

Background: Black-faced spoonbill (BFS) is a global endangered species, distributed only in the coastal zones of East Asia. Xinghua Bay is one of the main wintering sites and migration stopovers of BFS in mainland China. However, with the reduction and degradation of natural wetlands, it is uncertain whether the constructed wetland can provide habitat for the endangered BFS. Research on diet of BFS will help to understand their preference between natural and artificial wetlands, and also provide reference for their conservation and habitat restoration. Results: In the early winter, the proportion of Palaemonidae in BFS's food was as high as 74.4%, while that of other food was only 3.0% to 6.0%. In the late winter, the food contribution of BFS was as follow: Portunidae 39.3% > Palaemonidae 26.1% > Cyprinidae 8.8% > Mugilidae 8.5% > Gobiidae 7.3% > Crucian 5.1% > Whiteshrimp 4.8%. The proportion of Portunidae exceeded that of Palaemonidae, and together with Palaemonidae, it has become the main food of BFS in late winter. Conclusion: The diet composition of BFS between the early and late winter was significantly different, which may be due to seasonal changes in food resources. Natural wetlands are the main feeding grounds of BFS, but artificial wetlands also provide them with supplementary feeding grounds and resting places. Aquaculture ponds play an important ecological function in maintaining the overwintering population of BFS in Xinghua Bay.

opencc-zeroSep 2022View details →

Can diet composition estimates using stable isotope analysis of feathers predict growth and condition in nestling mountain bluebirds (Sialia currucoides)

Insectivorous birds breeding in seasonal environments provision their dependent young during periods when prey diversity and abundance vary. Consequently, the composition and nutritional value of diets parents feed to their offspring may differ within and among broods, potentially affecting the condition of nestlings. In a population of mountain bluebirds (Sialia currucoides), we used two methods to estimate diet composition for individual nestlings: direct observation of provisioning using video recordings at 5 and 9 days post-hatch, and stable isotopes of the δ13C and δ15N in nestling feathers and prey followed by analysis with mixing models. We determined the macronutrient content (% fat and lean mass) and estimated the metabolized energy from each type of prey. We evaluated whether different methods of estimating diet composition would produce similar results, and if the types of prey nestlings ate at one or both ages affected their morphology, growth rates, or blood ketone concentration. We found that bluebirds fed their young 5 main types of prey: beetles, cicadas, grasshoppers, insect larvae, and spiders. Both observational and mixing model estimates of diet composition indicated that larvae are traded-off with grasshoppers, and that fewer larvae are provided to nestlings as the season progresses. In evaluating how diet influences individual growth and condition, estimates from direct observations had greater explanatory power than those from mixing models, indicating that diets rich in the most energy-dense prey (greatest fat content; cicadas and larvae) were associated with larger size and higher body condition, and faster rate of mass gain and growth of tarsus. Lower value prey had more limited, specific effects on nestlings, but may still be important dietary components. While isotopic methods produced estimates of diet composition that were generally informative, when applied to explain the growth and condition of nestlings they proved less useful.

opencc-by-sa-4.0Nov 2017View details →

Data archive: Trophic structure of cold-water coral communities revealed from the analysis of tissue isotopes and fatty acid composition

Data belonging to the paper:  Dick van Oevelen, Gerard C. A. Duineveld, Marc S. S. Lavaleye, Tina Kutti and Karline Soetaert (2017) Trophic structure of cold-water coral communities revealed from the analysis of 55 tissue isotopes and fatty acid composition. Marine Biology Research, DOI: https://doi.org/10.1080/17451000.2017.1398404 Abstract: The trophic structure of cold-water coral reef communities at two contrasting locations, the 800- m deep Belgica Mounds (Irish margin) and 300-m deep Træna reefs (Norwegian Shelf), was investigated using stable isotope (δ13C and δ15N) and fatty-acid composition analysis. A broad range of specimens, with emphasis on (commercial) fish species, and organic matter sources were sampled using a variety of tools. Irrespective of the environmental and geographical setting, the δ15N values indicated that the food web encompasses roughly 1.5 to 3 trophic levels. Mobile echinoderms, i.e. sea urchins and sea stars, had highest δ15N values, indicative of a high trophic position in the food web. The fraction of bacterial fatty acids in reef fauna was generally low (<5%), indicating that enhanced bacterial production in the water column through seafloor seepage of nutrients (‘hydraulic theory’) does not form a significant energy pathway into the food web. The high fraction of algal and essential fatty acids in reef fauna and fish at both locations indicates a close coupling with surface productivity, but the transport mechanism depends on the hydrographic setting. At Træna, Calanus copepods and euphausiids form an additional link between primary production and fish, which is largely absent at Belgica Mounds. At Belgica Mounds, the reef community is primarily supported by phytodetritus, as evidenced by the high contribution of algal fatty acids in faunal tissue and seasonal chlorophyll a deposition and marine snow at the reef. The environmental setting of cold-water coral reefs influences the structure of the associated food web.

Fig. 5 in Towards incorporating insect isotope analysis using cavity ring-down spectroscopy into area-wide insect pest management programs

Fig. 5. Cumulative standard deviation of the mean carbon isotope signature of individual moths, field-caught LBAM (circles), mass-reared pink bollworm (squares) and mass-reared LBAM (triangles), analysed using the CM-CRDS module.

Fig. 3 in Towards incorporating insect isotope analysis using cavity ring-down spectroscopy into area-wide insect pest management programs

Fig. 3. Carbon isotope signature of common cutworm leg samples from different moths reared on the artificial laboratory diet or caught in the wild (circles, n = 5, Bars +/- 3 SD). The spermatophore data point (triangle) is the carbon isotope signature of spermatophores dissected from laboratory-reared females mated with field-caught males (n = 5, Bars +/- 3 SD). All samples measured using CM-CRDS.

Fig. 1 in Towards incorporating insect isotope analysis using cavity ring-down spectroscopy into area-wide insect pest management programs

Fig. 1. Carbon isotope ratios of 16 different common dietary components measured using either elemental analysis isotope ratio mass spectrometry (EAIRMS) or combustion module cavity ring down spectrometry (CM-CDRS).

Fig. 2 in Towards incorporating insect isotope analysis using cavity ring-down spectroscopy into area-wide insect pest management programs

Fig. 2. Carbon isotope ratios of 3 populations of the common cutworm measured using either elemental analysis isotope ratio mass spectrometry (EA-IRMS) or combustion module cavity ring down spectrometry (CM-CDRS): Field-caught moths: squares; synthetic diet-reared moths: circles and laboratory-reared on castor diet moths: triangles.

opencc-by-4.0Apr 2015View details →

Fig. 2 in Enhanced understanding of ectoparasite-host trophic linkages on coral reefs through stable isotope analysis

Fig. 2. Stable carbon and nitrogen isotope data for Haemulon flavolineatum blood vs. P3 (A and B), blood vs. adult gnathiids (C and D), and P3 vs. adult gnathiids (E and F). Solid triangles represent males and P3s, open triangles represent females. Error bars represent 1 SE of N = 5 individual P3 gnathiids analysed from each fish. Dashed line represents 1:1 linear relationship.

opencc-by-4.0Apr 2015View details →

Fig. 1 in Enhanced understanding of ectoparasite-host trophic linkages on coral reefs through stable isotope analysis

Fig. 1. Mean δ13C and δ15N (±1 Standard Error) values of gnathiids (open squares), (A) Haemulon flavolineatum heart (grey diamond), blood (white diamond), and muscle (black diamond), Pederson shrimp (Ancylomenes pedersoni, open triangle), and Anilocra isopods (cross), (B) Stegastes diencaeus heart (grey diamond), and muscle (black diamond), and Pederson shrimp (open triangle), and (c) Holocentrus adscenscionis heart (grey diamond), and muscle (black diamond), and Anilocra isopods (cross).

opencc-by-4.0Aug 2018View details →

Fig. 2 in Parasites in Myodes glareolus and their association with diet assessed by stable isotope analysis

Fig. 2. The relationship between parasite intensity and δ 15N values for the mite Listrophorus brevipes in September (S1) and October (S2) samples of Myodes glareolus. Note the log-scale for parasite abundance.

opencc-by-4.0Aug 2018View details →

Fig. 3 in Parasites in Myodes glareolus and their association with diet assessed by stable isotope analysis

Fig. 3. The average Pearsons Correlation Coefficient (error bars: SE) between abundance and δ 13C and δ 15N for the two parasite groups: ecto and endoparasite for females (left) and males (right). The data includes 13 parasites occurring on 5 or more individuals and indicate consistent correlations for endoparasites and δ 15 N, while this is not the case for δ 13C.