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Despite the importance of marine megafauna on ecosystem functioning, their contribution to the oceanic carbon cycle is still poorly known. Here, we explored the role of baleen whales in the biological carbon pump across the southern hemisphere based on the historical and forecasted abundance of five baleen whale species. We modelled whale-mediated carbon sequestration through the sinking of their carcasses after natural death. We provide the first temporal dynamics of this carbon pump from 1890 to 2100, considering both the effects of exploitation and climate change on whale populations. We reveal that at their pre-exploitation abundance, the five species of southern whales could sequester 4.0 × 10 5 tonnes of carbon per year (tC yr −1 ). This estimate dropped to 0.6 × 10 5 tC yr −1 by 1972 following commercial whaling. However, with the projected restoration of whale populations under a RCP8.5 climate scenario, the sequestration would reach 1.7 × 10 5 tC yr −1 by 2100, while without climate change, recovered whale populations could sequester nearly twice as much (3.2 × 10 5 tC yr −1 ) by 2100. This highlights the persistence of whaling damages on whale populations and associated services as well as the predicted harmful impacts of climate change on whale ecosystem services.

Wild-capture fisheries help provide food security to billions of people, yet bycatch of non-target species threatens ecosystem health and fishery sustainability. Appropriate monitoring and fisheries management can mitigate bycatch but require standardized bycatch data to be robustly recorded and effectively disseminated. Here we integrated and analysed 30,473 species-specific bycatch records from 95 US fisheries in 2010–2015. We examined patterns in fish and invertebrate, marine mammal, seabird and sea turtle bycatch and developed a standardized scoring system, the relative bycatch index, to assess bycatch performance of each fishery. The estimated amount of fish and invertebrate discards totalled 1.93 million tonnes (4.26 billion pounds) over the 6-year period. We found that the national discard rate is 10.5%, considerably lower than past estimates. Results from our relative bycatch index analysis can be used to facilitate management intervention strategies for particular fisheries or gear types, such as shrimp and otter trawls and several pelagic longline and gillnet fisheries, which had the poorest bycatch performance. These findings underscore the need for continued, high-quality, easily accessible bycatch information to better support fisheries management in the United States and globally. The sustainability of wild fisheries is limited by the capture of non-target species. This study estimates that such ‘bycatch’ from US fisheries totalled 1.93 million tonnes in 2010–2015, with a 10.5% discard rate. Despite considerable improvements, certain longline, trawl and gillnet fisheries have persistent bycatch issues.

The great whales (baleen and sperm whales), through their massive size and wide distribution, influence ecosystem and carbon dynamics. Whales directly store carbon in their biomass and contribute to carbon export through sinking carcasses. Whale excreta may stimulate phytoplankton growth and capture atmospheric CO

Synopsis Although gigantic body size and obligate filter feeding mechanisms have evolved in multiple vertebrate lineages (mammals and fishes), intermittent ram (lunge) filter feeding is unique to a specific family of baleen whales: rorquals. Lunge feeding is a high cost, high benefit feeding mechanism that requires the integration of unsteady locomotion (i.e., accelerations and maneuvers); the impact of scale on the biomechanics and energetics of this foraging mode continues to be the subject of intense study. The goal of our investigation was to use a combination of multi-sensor tags paired with UAS footage to determine the impact of morphometrics such as body size on kinematic lunging parameters such as fluking timing, maximum lunging speed, and deceleration during the engulfment period for a range of species from minke to blue whales. Our results show that, in the case of krill-feeding lunges and regardless of size, animals exhibit a skewed gradient between powered and fully unpowered engulfment, with fluking generally ending at the point of both the maximum lunging speed and mouth opening. In all cases, the small amounts of propulsive thrust generated by the tail were unable to overcome the high drag forces experienced during engulfment. Assuming this thrust to be minimal, we predicted the minimum speed of lunging across scale. To minimize the energetic cost of lunge feeding, hydrodynamic theory predicts slower lunge feeding speeds regardless of body size, with a lower boundary set by the ability of the prey to avoid capture. We used empirical data to test this theory and instead found that maximum foraging speeds remain constant and high (∼4 m s–1) across body size, even as higher speeds result in lower foraging efficiency. Regardless, we found an increasing relationship between body size and this foraging efficiency, estimated as the ratio of energetic gain from prey to energetic cost. This trend held across timescales ranging from a single lunge to a single day and suggests that larger whales are capturing more prey—and more energy—at a lower cost.

Marine debris is now a ubiquitous component of the Anthropocene global ocean. Plastic ingestion by marine wildlife was first reported in the 1960s and since that time, roughly one thousand marine species have been reported to consume this debris. This study focuses on plastic ingestion by marine invertebrates and vertebrates in the North Pacific Ocean. Specifically, we reviewed the scientific literature to assess the scope of the problem, identified key bioindicator species, and proposed guidelines for future monitoring of plastic debris in North Pacific marine ecosystems. Our meta-analysis confirmed that the North Pacific is among the most polluted ocean regions globally; roughly half of all fish and seabird specimens and more than three-quarters of sea turtles and bivalve specimens examined in this region had consumed plastic. While there are not enough standardized data to assess if these ingestion rates are changing, sampling standardization and reporting of methods are improving over time. Using a rubric-evaluation approach, we evaluated 352 species for their potential to serve as bioindicators of the prevalence of plastic pollution in the North Pacific. This analysis revealed a suite of 12 bioindicator species candidates which sample a variety of ecosystem components and cover a wide range of plastic size classes. Thus, we contend that these bioindicator candidates provide a key foundation for developing a comprehensive plastic monitoring program in the region. To enhance the utility of these bioindicators, we developed a framework for standardized data collection to minimize methodological variability across different studies and to facilitate the assessment of temporal trends over space and time. Tracking plastic ingestion by these bioindicators will help to assess the effectiveness of mitigation actions in the region, a critical step to evaluate progress towards sustainability and improved ocean health in the 21st century.

This research was funded in part by grants from the National Science Foundation (IOS-1656676, IOS-1656656; OPP-1644209 and 07-39483), the Office of Naval Research (N000141612477), and a Terman Fellowship from Stanford University. All procedures in USA were conducted under approval of the National Marine Fisheries Service (Permits 781-1824, 16163, 14809, 16111, 19116, 15271, 20430), Canada DFO SARA/MML 2010-01/SARA-106B, National Marine Sanctuaries (MULTI-2017-007), Antarctic Conservation Act (2009-014, 2015-011) and institutional IACUC committee protocols. Fieldwork, data collection and data processing for M. densirostris were funded by the Office of Naval Research grants N00014-07-10988, N00014-07-11023, N00014-08-10990, N00014-18-1-2062, and 00014-15-1-2553, and the U.S. Strategic Environmental Research and Development Program Grant SI-1539. PLT gratefully acknowledges funding from funding the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland). MASTS is funded by the Scottish Funding Council (HR09011) and contributing institutions. 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. Postprint

Significance We present a major advancement in our ability to bring the physiological laboratory to the open ocean through the noninvasive use of a suction cup-attached tag equipped with surface electrodes. Our study provides heart rate data of a large, free-diving whale (blue whale) without prior capture or restraint. We recorded a wide range of heart rates from the tag, reaching only several beats per minute during deep foraging dives (bradycardia) and nearly 40 beats per minute at the sea surface (tachycardia) as the whale recovered from its oxygen debt. The latter likely represents maximal heart rate given the measured duration of the heart beat itself, thereby demonstrating the greatest dynamic range in cardiac activity at this scale., 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.

Anthropogenic noise is a pervasive and increasing source of disturbance to wildlife. Marine mammals exhibit behavioural and physiological responses to naval sonar and other sound sources. The lost foraging opportunities and elevated locomotor effort associated with sonar disturbance likely carry energetic costs, which may lead to population-level consequences.We modelled the energetic costs associated with behavioural responses using (a) empirical datasets of cetacean feeding rates and prey characteristics and (b) allometry of swimming performance and metabolic rates.We applied our model to compare the short-term (i.e. the scale of the disturbance response; hours to days) energetic costs of a variety of observed behavioural responses. Efficient foragers (e.g. baleen whales) incur a greater relative energetic cost for mild behavioural responses as compared to the most extreme observed response for larger odontocetes (e.g. beaked whales). Energetic costs are more sensitive to lost feeding opportunities than increased energy expenditure from elevated locomotor effort.To scale up from short-term costs to long-term effects (months to years), future research should address individuals’ capacity to compensate for energetic losses as well as energetic thresholds for demographic rates (survival, fecundity). We discuss how relative energetic costs correlate with species’ pace of life and the implications for conservation planning.Synthesis and applications. Current approaches towards understanding the Population Consequences of Disturbance (PCoD) often must rely on expert opinion due to data deficiency. Our model provides an empirical method for linking behaviour to energetics, which is critical for managers to make informed decisions on actions that may affect marine mammal species. Furthermore, our model is applicable to other forms of disturbance, such as vessel traffic or seismic exploration, and our scaling approach enables risk projections for understudied species.

High efficiency lunate-tail swimming with high-aspect-ratio lifting surfaces has evolved in many vertebrate lineages, from fish to cetaceans. Baleen whales (Mysticeti) are the largest swimming animals that exhibit this locomotor strategy, and present an ideal study system to examine how morphology and the kinematics of swimming scale to the largest body sizes. We used data from whale-borne inertial sensors coupled with morphometric measurements from aerial drones to calculate the hydrodynamic performance of oscillatory swimming in six baleen whale species ranging in body length from 5 to 25 m (fin whale, Balaenoptera physalus; Bryde's whale, Balaenoptera edeni; sei whale, Balaenoptera borealis; Antarctic minke whale, Balaenoptera bonaerensis; humpback whale, Megaptera novaeangliae; and blue whale, Balaenoptera musculus). We found that mass-specific thrust increased with both swimming speed and body size. Froude efficiency, defined as the ratio of useful power output to the rate of energy input ( Sloop, 1978), generally increased with swimming speed but decreased on average with increasing body size. This finding is contrary to previous results in smaller animals, where Froude efficiency increased with body size. Although our empirically parameterized estimates for swimming baleen whale drag were higher than those of a simple gliding model, oscillatory locomotion at this scale exhibits generally high Froude efficiency as in other adept swimmers. Our results quantify the fine-scale kinematics and estimate the hydrodynamics of routine and energetically expensive swimming modes at the largest scale., Summary: Tags attached to baleen whales demonstrate how thrust power output, drag coefficient and Froude efficiency scale with swimming speed and body length.

Following rapid environmental change, why do some animals thrive, while others struggle? We present an expanded, cue–response framework for predicting variation in behavioral responses to novel situations. We show how signal detection theory can be used when individuals have three behavioral options (approach, avoid, or ignore). Based on this theory, we outline predictions about which animals are more likely to make mistakes around novel conditions (i.e., fall for a trap or fail to use an undervalued resource) and the intensity of that mismatch (i.e., severe versus moderate). Explicitly considering three options provides a more holistic perspective and allows us to distinguish between severe and moderate traps, which could guide management strategies in a changing world.

Plastic pollution has pervaded almost every facet of the biosphere, yet we lack an understanding of consumption risk by marine species at the global scale. To address this, we compile data from research documenting plastic debris ingestion by marine fish, totaling 171,774 individuals of 555 species. Overall, 386 marine fish species have ingested plastic debris including 210 species of commercial importance. However, 148 species studied had no records of plastic consumption, suggesting that while this evolutionary trap is widespread, it is not yet universal. Across all studies that accounted for microplastics, the incidence rate of plastic ingested by fish was 26%. Over the last decade this incidence has doubled, increasing by 2.4 ± 0.4% per year. This is driven both by increasing detection of smaller sized particles as a result of improved methodologies, as well as an increase in fish consuming plastic. Further, we investigated the role of geographic, ecological, and behavioral factors in the ingestion of plastic across species. These analyses revealed that the abundance of plastic in surface waters was positively correlated to plastic ingestion. Demersal species are more likely to ingest plastic in shallow waters; in contrast, pelagic species were most likely to consume plastic below the mixed layer. Mobile predatory species had the highest likelihood to ingest plastic; similarly, we found a positive relationship between trophic level and plastic ingestion. We also find evidence that surface ingestion‐deep sea egestion of microplastics by mesopelagic myctophids is likely a key mechanism for the export of microplastics from the surface ocean to the seafloor, a sink for marine debris. These results elucidate the role of ecology and biogeography underlying plastic ingestion by marine fish and point toward species and regions in urgent need of study., Our global analysis found 386 marine fish species that have ingested plastic debris, including 210 species of commercial importance. However, 148 species studied had no records of plastic consumption. Over the last decade the prevalence of plastic ingestion by marine fish has doubled, increasing by 2.4% per year, as a result of improved detection methodologies as well as an increase in fish consuming plastic. The projected increase in plastic production and disposal in the coming decades is expected to exacerbate this issue globally.

Despite a recent report of high concentrations of microplastics and microfibers in the mesopelagic waters of Monterey Bay National Marine Sanctuary (MBNMS), little is known about these particles in surface waters. From 2017 to 2019, we sampled two nearshore and two offshore locations within MBNMS using a manta trawl and analyzed these samples for microplastics and microfibers. We found an average concentration of 1.32 ± 0.70 (SE) particles per m3. We found the highest concentration of particles closest to shore, and the lowest concentration above the remote Davidson Seamount. Fiber-like debris was more common in offshore, as compared to nearshore, sites. Overall, particles in our samples were primarily buoyant synthetic polymers, including polypropylene and polyethylene. Our results provide baseline data on the degree of microplastic and microfiber pollution in MBNMS surface waters and confirm that this pollution can be found in waters from the surface to at least 1000 m depth.

Baleen whales influence their ecosystems through immense prey consumption and nutrient recycling1–3. It is difficult to accurately gauge the magnitude of their current or historic ecosystem role without measuring feeding rates and prey consumed. To date, prey consumption of the largest species has been estimated using metabolic models3–9 based on extrapolations that lack empirical validation. Here, we used tags deployed on seven baleen whale (Mysticeti) species (n = 321 tag deployments) in conjunction with acoustic measurements of prey density to calculate prey consumption at daily to annual scales from the Atlantic, Pacific, and Southern Oceans. Our results suggest that previous studies3–9 have underestimated baleen whale prey consumption by threefold or more in some ecosystems. In the Southern Ocean alone, we calculate that pre-whaling populations of mysticetes annually consumed 430 million tonnes of Antarctic krill (Euphausia superba), twice the current estimated total biomass of E. superba10, and more than twice the global catch of marine fisheries today11. Larger whale populations may have supported higher productivity in large marine regions through enhanced nutrient recycling: our findings suggest mysticetes recycled 1.2 × 104 tonnes iron yr−1 in the Southern Ocean before whaling compared to 1.2 × 103 tonnes iron yr−1 recycled by whales today. The recovery of baleen whales and their nutrient recycling services2,3,7 could augment productivity and restore ecosystem function lost during 20th century whaling12,13. A combination of 3D whale locations and acoustic measurements of prey density is used here to show that whales’ consumption of krill is several times larger than often thought.

Pfaller et al. report that sea turtles respond to odors from biofouled plastic debris with the same behavior that is elicited by food odors, providing a possible unifying explanation for why sea turtles interact with marine plastic.

Large marine regions, including the exceptionally productive Southern Ocean, are iron-limited. As a result, there has been substantial interest in iron-fertilizing high nutrient low chlorophyll (HNLC) areas in an effort to sequester atmospheric carbon dioxide. More recently, research has shifted to quantifying the beneficial effects of iron recycling by marine biota. Marine top predators such as whales and seabirds have been examined specifically in this regard as they have high biomass, form dense aggregations, and excrete bioavailable iron in concentrations seven orders of magnitude higher than ambient seawater. Despite it being well established that marine fauna link the iron and carbon cycles, the connection of this process to the sulfur cycle has rarely been considered. The chemoattraction of specific marine fauna to algal-derived dimethyl sulfide (DMS) is key in triggering dense, multi-species foraging aggregations that induce iron recycling, augmenting carbon assimilation. The goal of this paper is twofold; first, to highlight DMS chemoattraction as a behavior that catalyzes carbon sequestration via natural iron fertilization, and second, to identify knowledge gaps that recent biogeochemical advances can address. Fostering this interdisciplinary research will enhance our understanding of global climate regulation, ecosystem services provided by marine top predators, and the biogeochemical cycles of carbon, iron, and sulfur in HNLC waters.

The scale dependence of locomotor factors has long been studied in comparative biomechanics, but remains poorly understood for animals at the upper extremes of body size. Rorqual baleen whales include the largest animals, but we lack basic kinematic data about their movements and behavior below the ocean surface. Here, we combined morphometrics from aerial drone photogrammetry, whale-borne inertial sensing tag data and hydrodynamic modeling to study the locomotion of five rorqual species. We quantified changes in tail oscillatory frequency and cruising speed for individual whales spanning a threefold variation in body length, corresponding to an order of magnitude variation in estimated body mass. Our results showed that oscillatory frequency decreases with body length (∝length-0.53) while cruising speed remains roughly invariant (∝length0.08) at 2 m s-1 We compared these measured results for oscillatory frequency against simplified models of an oscillating cantilever beam (∝length-1) and an optimized oscillating Strouhal vortex generator (∝length-1). The difference between our length-scaling exponent and the simplified models suggests that animals are often swimming non-optimally in order to feed or perform other routine behaviors. Cruising speed aligned more closely with an estimate of the optimal speed required to minimize the energetic cost of swimming (∝length0.07). Our results are among the first to elucidate the relationships between both oscillatory frequency and cruising speed and body size for free-swimming animals at the largest scale.

Identifying terrestrial sources of debris is essential to suppress the flow of plastic to the ocean. Here, we report a novel source of debris to the marine environment. From May 2016 to June 2018, we collected golf balls from coastal environments associated with five courses in Carmel, California. Our 75 collections recovered 39,602 balls from intertidal and nearshore environments adjacent to, or downriver from, the golf courses. Combining our collections with concurrent efforts of the Monterey Bay National Marine Sanctuary and the Pebble Beach Corporation, we report the retrieval of 50,681 balls, totaling approximately 2.5 tons of debris. We also examined decomposition patterns in the collected balls, which illustrate that degradation and loss of microplastic from golf balls to the marine environment may be of concern. Our findings will help to develop and direct mitigation procedures for this region and others with coastal golf courses.

The potential for extirpation of extremely small populations (ESPs) is high due to their vulnerability to demographic and environmental stochasticity and negative impacts of human activity. We argue that conservation actions that could aid ESPs are sometimes delayed because of a fear of failure. In human psychology, the fear of failure is composed of several distinct cognitive elements, including “uncertainty about the future” and “upsetting important others.” Uncertainty about the future is often driven by information obstacles in conservation: information is either not easily shared among practitioners or information is lacking. Whereas, fear of upsetting important others can be due to apprehension about angering constituents, peers, funders, and other stakeholders. We present several ways to address these fears in hopes of improving the conservation process. We describe methods for increased information sharing and improved decision-making in the face of uncertainty, and recommend a shift in focus to cooperative actions and improving methods for evaluating success. Our hope is that by tackling stumbling blocks due to the apprehension of failure, conservation and management organizations can take steps to move from fear to action.

An infochemical found on marine plastic debris elucidates a novel mechanism for plastic ingestion by marine wildlife., Plastic debris is ingested by hundreds of species of organisms, from zooplankton to baleen whales, but how such a diversity of consumers can mistake plastic for their natural prey is largely unknown. The sensory mechanisms underlying plastic detection and consumption have rarely been examined within the context of sensory signals driving marine food web dynamics. We demonstrate experimentally that marine-seasoned microplastics produce a dimethyl sulfide (DMS) signature that is also a keystone odorant for natural trophic interactions. We further demonstrate a positive relationship between DMS responsiveness and plastic ingestion frequency using procellariiform seabirds as a model taxonomic group. Together, these results suggest that plastic debris emits the scent of a marine infochemical, creating an olfactory trap for susceptible marine wildlife.

Cat predation of birds in residential landscapes is ephemeral, unpredictable, and spatially dispersed, and thus requires many person-hours to observe. We sought to identify whether specific behaviors, traits, or feeding ecologies of birds contribute to their probability of cat-caused mortality around residences across temperate North America. In addressing this question, we evaluated citizen science data with respect to peer-reviewed species accounts (Birds of North America, BNA). Using information on cat predation from the BNA, we found that species that glean their prey from the ground or breed in nest boxes were three times more likely to be depredated by cats, while birds that hawk were over two times less likely to become cat prey than would be predicted by random chance. Data from citizen science sources also showed that birds using nest boxes had increased susceptibility to cat predation, as did those that use feeders and that glean from foliage. We caution that observations of predation by citizen science volunteers may be biased towards detection at feeders. Future research should focus on developing volunteer survey techniques for improving estimates of bird mortality rates and sources.

The causes and consequences of coloniality in seabirds, and larids in particular, have received extensive study. Here, we use the Herring Gull (Larus argentatus) as a model organism to investigate the effect of nest density on chicks' growth rate and survival. On Appledore Island, Maine, Herring Gulls nest both in dense subcolonies and in more isolated situations, affording a unique opportunity for comparison of reproductive success of pairs nesting in both contexts on the same island. Chicks reared in dense subcolonies grew at a rate significantly higher than that of those reared in more isolated settings. Using mark-recapture analysis, we found that a chick's expected survival is dependent on hatch weight, hatch date, hatch order, and context (nest in dense or loose subcolony). The first chick to hatch in each nest had a significantly greater probability of surviving to fledging than the last-hatched chick. Last-hatched chicks had a significantly greater chance of survival from hatching to fle...

Tritrophic mutualistic interactions have been best studied in plant–insect systems. During these interactions, plants release volatiles in response to herbivore damage, which, in turn, facilitates predation on primary consumers or benefits the primary producer by providing nutrients. Here we explore a similar interaction in the Southern Ocean food web, where soluble iron limits primary productivity. Dimethyl sulfide has been studied in the context of global climate regulation and is an established foraging cue for marine top predators. We present evidence that procellariiform seabird species that use dimethyl sulfide as a foraging cue selectively forage on phytoplankton grazers. Their contribution of beneficial iron recycled to marine phytoplankton via excretion suggests a chemically mediated link between marine top predators and oceanic primary production.