High-resolution sampling of particulate organic carbon in a coastal upwelling system

Summertime, wind-driven upwelling off the Oregon coast delivers nutrient rich water to the surface that fuels the autotrophic production of particulate organic carbon (POC). This POC can be transported horizontally by fluid motions and vertically by sinking to the bottom where it can be entrained in the benthic boundary layer (BBL). POC can be transformed during transport by heterotrophic metabolism, thus changing its concentration and composition. To better understand the dynamics of POC within the water column of this highly variable system, we developed a semi-automated filtration system that, when coupled to a towed profiling/sampling vehicle, allowed us to collect POC samples at higher spatial and temporal resolution than previously possible. During late May of 2009 we used this system to collect around 400 POC samples from two cross-shelf transects off the central Oregon coast spanning the ranges between BBL and surface mixed layer, and shelfbreak to shoreline. These samples were collected in conjunction with in-situ measurements of temperature, salinity, chlorophyll fluorescence, optical backscatter, and beam attenuation coefficients. Analyses of both the optical and bulk measurements indicate the presence of three distinct particle pools. The first pool is rich in POC and shows elevated fluorescence and beam-c relative to optical backscatter. The second pool is elevated in both fluorescence and optical backscatter, and is rich in POC relative to beam-c. The third pool is depleted in POC and shows proportionately elevated backscatter. Using variations in the optical properties of these three particle pools, we created multiple POC – beam-c calibrations, which allowed us to derive high-resolution POC distributions within the water column. This derived distribution indicates a decoupling between sediment and carbon in the BBL, and an unanticipated elevation of POC in the mid water column

Changes in serum adipokines during natural extended fasts in female northern elephant seals

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rzucidlo, C. L., Sperou, E. S., Holser, R. R., Khudyakov, J., Costa, D. P., & Crocker, D. E. Changes in serum adipokines during natural extended fasts in female northern elephant seals. General and Comparative Endocrinology, 308, (2021): 113760, https://doi.org/10.1016/j.ygcen.2021.113760.Adipose tissue is essential to endotherms for thermoregulation and energy storage as well as functioning as an endocrine organ. Adipose derived hormones, or adipokines, regulate metabolism, energy expenditure, reproduction, and immune function in model systems but are less well studied in wildlife. Female northern elephant seals (NES) achieve high adiposity during foraging and then undergo natural fasts up to five weeks long during haul-outs associated with reproduction and molting, resulting in large changes in adipose reserves. We measured circulating levels of four adipokines: leptin, resistin, adiponectin, and kisspeptin-54, in 196 serum samples from female NES at the beginning and end of their breeding and molting fasts. We examined the relationships between these adipokines and life-history stage, adiposity, mass, cortisol, and an immune cytokine involved in the innate immune response interleukin 6 (IL-6). All four adipokines varied with life-history stage. Leptin concentrations were highest at the beginning of the breeding haul-out. Resistin concentrations were higher throughout the breeding haul-out compared to the molt haul-out. Adiponectin concentrations were highest at the beginning of both haul-outs. Kisspeptin-54 concentrations were highest at the end of the breeding haul-out. Leptin, resistin, and adiponectin were associated with measures of body condition, either adiposity, mass, or both. Resistin, adiponectin, and kisspeptin-54 were associated with circulating cortisol concentrations. Resistin was strongly associated with circulating IL-6, a multifunctional cytokine. Adiponectin was associated with glucose concentrations, suggesting a potential role in tissue-specific insulin sensitivity during life-history stages categorized by high adiposity. Increased cortisol concentrations late in lactation were associated with increased kisspeptin-54, suggesting a link to ovulation initiation in NES. This study suggests dramatic changes in circulating adipokines with life-history and body condition that may exert important regulatory roles in NES. The positive relationship between adiponectin and adiposity as well as the lack of a relationship between leptin and kisspeptin-54 differed from model systems. These differences from biomedical model systems suggest the potential for modifications of expression and function of adipose-derived hormones in species that undergo natural changes in adiposity as part of their life-history.This project was supported by a grant from the Office of Naval Research (#N00014-18-1-2822) to DPC and DEC and the Marine Life Joint Industry Program of the IAGOP. We thank the Año Nuevo State Reserve rangers for logistical support

Body condition changes at sea: onboard calculation and telemetry of body density in diving animals

This study was supported by grants from the Office of Naval Research N00014-18-1-2822, DoD SERDP contract W912HQ20C0056, IPEV (Institut Paul Emile Victor) under the Antarctic research program 109 (C. Barbraud) and 1201 (C. Gilbert & C. Guinet), and CNES-TOSCA as part of the SNO-MEMO.The ability of marine mammals to accumulate sufficient lipid energy reserves is vital for mammals' survival and successful reproduction. However, long-term monitoring of at-sea changes in body condition, specifically lipid stores, has only been possible in elephant seals performing prolonged drift dives (low-density lipids alter the rates of depth change while drifting). This approach has limited applicability to other species. Using hydrodynamic performance analysis during transit glides, we developed and validated a novel satellite-linked data logger that calculates real-time changes in body density (∝lipid stores). As gliding is ubiquitous amongst divers, the system can assess body condition in a broad array of diving animals. The tag processes high sampling rate depth and three-axis acceleration data to identify 5 s high pitch angle glide segments at depths >100 m. Body density is estimated for each glide using gliding speed and pitch to quantify drag versus buoyancy forces acting on the gliding animal. We used tag data from 24 elephant seals (Mirounga spp.) to validate the onboard calculation of body density relative to drift rate. The new tags relayed body density estimates over 200 days and documented lipid store accumulation during migration with good correspondence between changes in body density and drift rate. Our study provided updated drag coefficient values for gliding (Cd,f = 0.03) and drifting (Cd,s = 0.12) elephant seals, both substantially lower than previous estimates. We also demonstrated post-hoc estimation of the gliding drag coefficient and body density using transmitted data, which is especially useful when drag parameters cannot be estimated with sufficient accuracy before tag deployment. Our method has the potential to advance the field of marine biology by switching the research paradigm from indirectly inferring animal body condition from foraging effort to directly measuring changes in body condition relative to foraging effort, habitat, ecological factors and anthropogenic stressors in the changing oceans. Expanding the method to account for diving air volumes will expand the system's applicability to shallower-diving (<100 m) species, facilitating real-time monitoring of body condition in a broad range of breath-hold divers.Publisher PDFPeer reviewe

First observations of Weddell seals foraging in sponges in Erebus Bay, Antarctica

Attaching cameras to marine mammals allows for first-hand observation of underwater behaviours that may otherwise go unseen. While studying the foraging behaviour of 26 lactating Weddell seals (Leptonychotes weddellii) in Erebus Bay during the austral spring of 2018 and 2019, we witnessed three adults and one pup investigating the cavities of Rossellidae glass sponges, with one seal visibly chewing when she removed her head from the sponge. To our knowledge, this is the first report of such behaviour. While the prey item was not identifiable, some Trematomus fish (a known Weddell seal prey) use glass sponges for shelter and in which to lay their eggs. Three of the four sponge foraging observations occurred around 13:00 (NZDT). Two of the three sponge foraging adults had higher-than-average reproductive rates, and the greatest number of previous pups of any seal in our study population, each having ten pups in 12 years. This is far higher than the study population average of three previous pups (± 2.6 SD). This novel foraging strategy may have evolved in response to changes in prey availability, and could offer an evolutionary advantage to some individuals that exploit prey resources that others may not. Our observations offer new insight into the foraging behaviours of one of the world’s most studied marine mammals. Further research on the social aspects of Weddell seal behaviour may increase our understanding of the extent and mechanisms of behavioural transfer between conspecifics. Research into the specific foraging behaviour of especially successful or experienced breeders is also warranted

Extent and Magnitude of Subsurface Anomalies During the Northeast Pacific Blob as Measured by Animal‐Borne Sensors

Marine heatwaves (MHWs) are prolonged warm water events that are increasing in frequency and magnitude due to rising global temperatures. The Northeast Pacific Blob was an unusually widespread MHW that affected ecosystems across the Northeast Pacific, from producers to top predators. Temperature and salinity data collected by northern elephant seals (Mirounga angustirostris) from 2014 to 2017 show significant (&gt;2 sd) warm anomalies throughout the top 1,000&nbsp;m of the water column, with peak warming in late 2015. Using temperature and salinity as a tracer of layers of constant density, we looked at how lateral advection may have contributed to the development of the Blob. Temperature and salinity anomalies and the expansion of the water column at the base of the pycnocline both indicate that northward advection of warm, salty water played an important role in the observed accumulation of warm water, in addition to surface warming. These findings contribute to our understanding of the physical dynamics of the Blob, especially the thermal content and structure of the water column, and offer mechanisms for its formation and maintenance, which are crucial to assessing the ecological effects of MHWs now and in the future

Density-dependent effects on reproductive output in a capital breeding carnivore, the northern elephant seal (Mirounga angustirostris).

All organisms face resource limitations that will ultimately restrict population growth, but the controlling mechanisms vary across ecosystems, taxa, and reproductive strategies. Using four decades of data, we examine how variation in the environment and population density affect reproductive outcomes in a capital-breeding carnivore, the northern elephant seal (Mirounga angustirostris). This species provides a unique opportunity to examine the relative importance of resource acquisition and density-dependence on breeding success. Capital breeders accrue resources over large temporal and spatial scales for use during an abbreviated reproductive period. This strategy may have evolved, in part, to confer resilience to short-term environmental variability. We observed density-dependent effects on weaning mass, and maternal age (experience) was more important than oceanographic conditions or maternal mass in determining offspring weaning mass. Together these findings show that the mechanisms controlling reproductive output are conserved across terrestrial and marine systems and vary with population dynamics, an important consideration when assessing the effect of extrinsic changes, such as climate change, on a population