Field measurements reveal exposure risk to microplastic ingestion by filter-feeding megafauna.

Microparticles, such as microplastics and microfibers, are ubiquitous in marine food webs. Filter-feeding megafauna may be at extreme risk of exposure to microplastics, but neither the amount nor pathway of microplastic ingestion are well understood. Here, we combine depth-integrated microplastic data from the California Current Ecosystem with high-resolution foraging measurements from 191 tag deployments on blue, fin, and humpback whales to quantify plastic ingestion rates and routes of exposure. We find that baleen whales predominantly feed at depths of 50-250 m, coinciding with the highest measured microplastic concentrations in the pelagic ecosystem. Nearly all (99%) microplastic ingestion is predicted to occur via trophic transfer. We predict that fish-feeding whales are less exposed to microplastic ingestion than krill-feeding whales. Per day, a krill-obligate blue whale may ingest 10 million pieces of microplastic, while a fish-feeding humpback whale likely ingests 200,000 pieces of microplastic. For species struggling to recover from historical whaling alongside other anthropogenic pressures, our findings suggest that the cumulative impacts of multiple stressors require further attention.

Lunge filter feeding biomechanics constrain rorqual foraging ecology across scale.

Fundamental scaling relationships influence the physiology of vital rates, which in turn shape the ecology and evolution of organisms. For diving mammals, benefits conferred by large body size include reduced transport costs and enhanced breath-holding capacity, thereby increasing overall foraging efficiency. Rorqual whales feed by engulfing a large mass of prey-laden water at high speed and filtering it through baleen plates. However, as engulfment capacity increases with body length (engulfment volume∝body length3.57), the surface area of the baleen filter does not increase proportionally (baleen area∝body length1.82), and thus the filtration time of larger rorquals predictably increases as the baleen surface area must filter a disproportionally large amount of water. We predicted that filtration time should scale with body length to the power of 1.75 (filter time∝body length1.75). We tested this hypothesis on four rorqual species using multi-sensor tags with corresponding unoccupied aircraft systems-based body length estimates. We found that filter time scales with body length to the power of 1.79 (95% CI: 1.61-1.97). This result highlights a scale-dependent trade-off between engulfment capacity and baleen area that creates a biomechanical constraint to foraging through increased filtration time. Consequently, larger whales must target high-density prey patches commensurate to the gulp size to meet their increased energetic demands. If these optimal patches are absent, larger rorquals may experience reduced foraging efficiency compared with smaller whales if they do not match their engulfment capacity to the size of targeted prey aggregations.

Why whales are big but not bigger: Physiological drivers and ecological limits in the age of ocean giants.

The largest animals are marine filter feeders, but the underlying mechanism of their large size remains unexplained. We measured feeding performance and prey quality to demonstrate how whale gigantism is driven by the interplay of prey abundance and harvesting mechanisms that increase prey capture rates and energy intake. The foraging efficiency of toothed whales that feed on single prey is constrained by the abundance of large prey, whereas filter-feeding baleen whales seasonally exploit vast swarms of small prey at high efficiencies. Given temporally and spatially aggregated prey, filter feeding provides an evolutionary pathway to extremes in body size that are not available to lineages that must feed on one prey at a time. Maximum size in filter feeders is likely constrained by prey availability across space and time.

Extreme bradycardia and tachycardia in the world's largest animal.

The biology of the blue whale has long fascinated physiologists because of the animal's extreme size. Despite high energetic demands from a large body, low mass-specific metabolic rates are likely powered by low heart rates. Diving bradycardia should slow blood oxygen depletion and enhance dive time available for foraging at depth. However, blue whales exhibit a high-cost feeding mechanism, lunge feeding, whereby large volumes of prey-laden water are intermittently engulfed and filtered during dives. This paradox of such a large, slowly beating heart and the high cost of lunge feeding represents a unique test of our understanding of cardiac function, hemodynamics, and physiological limits to body size. Here, we used an electrocardiogram (ECG)-depth recorder tag to measure blue whale heart rates during foraging dives as deep as 184 m and as long as 16.5 min. Heart rates during dives were typically 4 to 8 beats min-1 (bpm) and as low as 2 bpm, while after-dive surface heart rates were 25 to 37 bpm, near the estimated maximum heart rate possible. Despite extreme bradycardia, we recorded a 2.5-fold increase above diving heart rate minima during the powered ascent phase of feeding lunges followed by a gradual decrease of heart rate during the prolonged glide as engulfed water is filtered. These heart rate dynamics explain the unique hemodynamic design in rorqual whales consisting of a large-diameter, highly compliant, elastic aortic arch that allows the aorta to accommodate blood ejected by the heart and maintain blood flow during the long and variable pauses between heartbeats.

Cardiopulmonary bypass considerations for pediatric patients on the ketogenic diet.

BACKGROUND: There is a population of children with epilepsy that is refractory to anti-epileptic drugs. The ketogenic diet, a high-fat, low-carbohydrate regimen, is one alternative treatment to decrease seizure activity. Special considerations are required for patients on the ketogenic diet undergoing cardiopulmonary bypass (CPB) to prevent exposure to glucose substrates that could alter ketosis, increasing the risk of recurrent seizures. CASE STUDY: A 2-year-old, 9 kilogram male with a history of infantile spasms with intractable epilepsy, trisomy 21 status post tetralogy of Fallot repair, presented to the cardiac operating room for closure of a residual atrial septal defect. All disciplines of the surgical case minimized the use of carbohydrate-containing and contraindicated medications. Changes to the standard protocol and metabolic monitoring ensured the patient maintained ketosis. DISCUSSION: All disciplines within cardiac surgery need to be cognizant of patients on the ketogenic diet and prepare a modified protocol. Future monitoring considerations include thromboelastography, electroencephalography and continuous glucose measurement. Key areas of focus with this patient population in the cardiac surgical theater are to maintain a multidisciplinary approach, alter the required CPB prime components, address cardiac pharmacological concerns and limit any abnormal hematological occurrences.

Food selection and eating patterns: themes found among people with type 2 diabetes mellitus.

OBJECTIVE: The objective of this study was to examine the beliefs and perspectives among people with type 2 diabetes mellitus about dietary requirements, food selection and eating patterns, and attitudes about self-management practices. DESIGN: Semistructured, in-depth interviews explored participants' experiences with diabetes prior to their diagnosis, participants' understanding of the guidelines for the nutritional management of diabetes, how participants applied their understanding of dietary guidelines to daily food selection and eating patterns, and the social and personal themes influencing participants' food selection and eating patterns. SUBJECTS: Interviews were conducted with members of a convenience sample of 45 men and women diagnosed with type 2 diabetes for at least 1 year. ANALYSES PERFORMED: Interviews were coded using a conceptual matrix derived from participants' statements. Common characteristics were grouped, and broad themes were identified. RESULTS: Eating patterns were influenced by participants' knowledge of diabetes management. Challenges that participants encountered when applying nutrition recommendations were linked to their prior eating practices. Dietary self-efficacy, social support, and time management were identified as mediating variables that can influence dietary behaviors. IMPLICATIONS: Diabetes nutrition education programs should increase awareness of eating history, spousal support, and time management practices. Future research should include the refinement and validation of a nutritional management model of diabetes.