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1. Skin in the game: Epidermal molt as a driver of long‐distance migration in whales

   https://doi.org/10.1111/mms.12661  

   Pitman, Robert L. ; Durban, John W. ; Joyce, Trevor ; Fearnbach, Holly ; Panigada, Simone ; Lauriano, Giancarlo ( December 2019 , Marine Mammal Science)

   Long‐distance migration in whales has historically been described as an annual, round‐trip movement between high‐latitude, summer feeding grounds, and low‐latitude, winter breeding areas, but there is no consensus about why whales travel to the tropics to breed. Between January 2009 and February 2016, we satellite‐tagged 62 antarctic killer whales (Orcinus orca) of four different ecotypes, of which at least three made short‐term (6–8 weeks), long‐distance (maximum 11,000 km, round trip), essentially nonstop, migrations to warm waters (SST 20°C–24°C), and back. We previously suggested that antarctic killer whales could conserve body heat in subfreezing (to −1.9°C) waters by reducing blood flow to their skin, but that this might preclude normal (i.e., continuous) epidermal molt, and necessitate periodic trips to warm waters for routine skin maintenance (“skin molt migration,” SMM). In contrast to the century‐old “feeding/breeding” migration paradigm, but consistent with a “feeding/molting” hypothesis, the current study provides additional evidence that deferred skin molt could be the main driver of long‐distance migration for antarctic killer whales. Furthermore, we argue that for all whales that forage in polar latitudes and migrate to tropical waters, SMM might also allow them to exploit rich prey resources in a physiologically challenging environment and maintain healthy skin.

    

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2. Combining Regional Habitat Selection Models for Large-Scale Prediction: Circumpolar Habitat Selection of Southern Ocean Humpback Whales

   https://doi.org/10.3390/rs13112074  

   Reisinger, Ryan R. ; Friedlaender, Ari S. ; Zerbini, Alexandre N. ; Palacios, Daniel M. ; Andrews-Goff, Virginia ; Dalla Rosa, Luciano ; Double, Mike ; Findlay, Ken ; Garrigue, Claire ; How, Jason ; et al ( June 2021 , Remote Sensing)

   Machine learning algorithms are often used to model and predict animal habitat selection—the relationships between animal occurrences and habitat characteristics. For broadly distributed species, habitat selection often varies among populations and regions; thus, it would seem preferable to fit region- or population-specific models of habitat selection for more accurate inference and prediction, rather than fitting large-scale models using pooled data. However, where the aim is to make range-wide predictions, including areas for which there are no existing data or models of habitat selection, how can regional models best be combined? We propose that ensemble approaches commonly used to combine different algorithms for a single region can be reframed, treating regional habitat selection models as the candidate models. By doing so, we can incorporate regional variation when fitting predictive models of animal habitat selection across large ranges. We test this approach using satellite telemetry data from 168 humpback whales across five geographic regions in the Southern Ocean. Using random forests, we fitted a large-scale model relating humpback whale locations, versus background locations, to 10 environmental covariates, and made a circumpolar prediction of humpback whale habitat selection. We also fitted five regional models, the predictions of which we used as input features for four ensemble approaches: an unweighted ensemble, an ensemble weighted by environmental similarity in each cell, stacked generalization, and a hybrid approach wherein the environmental covariates and regional predictions were used as input features in a new model. We tested the predictive performance of these approaches on an independent validation dataset of humpback whale sightings and whaling catches. These multiregional ensemble approaches resulted in models with higher predictive performance than the circumpolar naive model. These approaches can be used to incorporate regional variation in animal habitat selection when fitting range-wide predictive models using machine learning algorithms. This can yield more accurate predictions across regions or populations of animals that may show variation in habitat selection. 

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3. Exploring the impact of climate change on the global distribution of non‐spinose planktonic foraminifera using a trait‐based ecosystem model

   https://doi.org/10.1111/gcb.15964  

   Grigoratou, Maria ; Monteiro, Fanny M. ; Wilson, Jamie D. ; Ridgwell, Andy ; Schmidt, Daniela N. ( November 2021 , Global Change Biology)

   Planktonic foraminifera are one of the primary calcifiers in the modern ocean, contributing 23%–56% of total global pelagic carbonate production. However, a mechanistic understanding of how physiology and environmental conditions control their abundance and distribution is lacking, hindering the projection of the impact of future climate change. This understanding is important, not only for ecosystem dynamics, but also for marine carbon cycling because of foraminifera's key role in carbonate production. Here we present and apply a global trait‐based ecosystem model of non‐spinose planktonic foraminifera (‘ForamEcoGEnIE’) to assess their ecology and global distribution under future climate change. ForamEcoGEnIE considers the traits of calcium carbonate production, shell size, and foraging. It captures the main characteristic of biogeographical patterns of non‐spinose species – with maximum biomass concentrations found in mid‐ to high‐latitude waters and upwelling areas. The model also reproduces the magnitude of global carbonate production relatively well, although the foraminifera standing stock is systematically overestimated. In response to future scenarios of rising atmospheric CO₂(RCP6 and RCP8.5), on a regional scale, the modelled foraminifera biomass and export flux increases in the subpolar regions of the North Atlantic and the Southern Ocean while it decreases everywhere else. In the absence of adaptation, the biomass decline in the low‐latitude South Pacific suggests extirpation. The model projects a global average loss in non‐spinose foraminifera biomass between 8% (RCP6) and 11% (RCP8.5) by 2050 and between 14% and 18% by 2100 as a response to ocean warming and associated changes in primary production and ecological dynamics. Global calcium carbonate flux associated with non‐spinose foraminifera declines by 13%–18% by 2100. That decline can slow down the ocean carbonate pump and create short‐term positive feedback on rising atmosphericpCO₂.

    

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4. Tracking Southern Ocean Sea Ice Extent With Winter Water: A New Method Based on the Oxygen Isotopic Signature of Foraminifera

   https://doi.org/10.1029/2020PA004095  

   Lund, David C. ; Chase, Zanna ; Kohfeld, Karen E. ; Wilson, Earle A. ( May 2021 , Paleoceanography and Paleoclimatology)

   Southern Ocean sea ice plays a central role in the oceanic meridional overturning circulation, transforming globally prevalent watermasses through surface buoyancy loss and gain. Buoyancy loss due to surface cooling and sea ice growth promotes the formation of bottom water that flows into the Atlantic, Indian, and Pacific basins, while buoyancy gain due to sea ice melt helps transform the returning deep flow into intermediate and mode waters. Because northward expansion of Southern Ocean sea ice during the Last Glacial Maximum (LGM; 19–23 kyr BP) may have enhanced deep ocean stratification and contributed to lower atmospheric CO₂levels, reconstructions of sea ice extent are critical to understanding the LGM climate state. Here, we present a new sea ice proxy based on the¹⁸O/¹⁶O ratio of foraminifera (δ¹⁸O_c). In the seasonal sea ice zone, sea ice formation during austral winter creates a cold surface mixed layer that persists in the sub‐surface during spring and summer. The cold sub‐surface layer, known as winter water, sits above relatively warm deep water, creating an inverted temperature profile. The unique surface‐to‐deep temperature contrast is reflected in estimates of equilibrium δ¹⁸O_c, implying that paired analysis of planktonic and benthic foraminifera can be used to infer sea ice extent. To demonstrate the feasibility of the δ¹⁸O_cmethod, we present a compilation ofN. pachydermaandCibicidoidesspp. results from the Atlantic sector that yields an estimate of winter sea ice extent consistent with modern observations.

    

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5. Investigation and Design of a Towable Hydrophone Array for General Ocean Sensing

   https://doi.org/10.1109/OCEANSE.2019.8867239  

   Schinault, Matthew E. ; Penna, Seth M. ; Garcia, Heriberto A. ; Ratilal, Purnima ( June 2019 , IEEE OCEANS 2019 - Marseille)

   An eight-element oil-filled hydrophone array is used to measure the acoustic field in littoral waters. This prototype array was deployed during an experiment between Jeffrey’s Ledge and the Stellwagen Bank region off the coast of Rockport, Massachusetts USA. During the experiment, several humpback whale vocalizations, distant ship tonals and high frequency conventional echosounder pings were recorded. Visual confirmation of humpback moving in bearing relative to the array verifies the directional sensing from array beamforming. During deployment, the array is towed at speeds varying from 4-7 kts in water depths of roughly 100 m with conditions at sea state 2 to 3. This array system consists of a portable winch with array, tow cable and 3 water-resistant boxes housing electronics. This system is deployed and operated by 2 crew members onboard a 13 m commercial fishing vessel during the experiment. Non-acoustic sensor (NAS) information is obtained to provide depth, temperature, and heading data using commercial off the shelf (COTS) components utilizing RS485/232 data communications. Acoustic data sampling was performed at 8 kHz, 30 kHz and 100 kHz with near real-time processing of data and enhanced Signal to Noise Ratio (SNR) from beamforming. The electrical system components are deployed with 3 stacked electronics boxes housing power, data acquisition and data processing components in water resistant compartments. A laptop computer with 8 TB of external storage and an independent Global Positioning System (GPS) antenna is used to run Passive Ocean Acoustic Waveguide Remote Sensing (POAWRS) software providing beamformed spectrogram data and live NAS data with capability of capturing several days of data. The acquisition system consists of Surface Mount Device (SMD) pre-amplifiers with filter to an analog differential pair shipboard COTS acquisition system. Pre-amplifiers are constructed using SMD technology where components are pressure tolerant and potting is not necessary. Potting of connectors, electronics and hydrophones via 3D printed molding techniques will be discussed. Array internal components are manufactured with Thermoplastic Polyurethane (TPU) 3D printed material to dampen array vibrations with forward and aft vibration isolation modules (VIM). Polyurethane foam (PUF) used to scatter breathing waves and dampen contact from wires inside the array without attenuating high frequencies and allowing for significant noise reduction. A single Tygon array section with a length of 7.5 m and diameter of 38 mm contains 8 transducer elements with a spacing of 75 cm (1 kHz design frequency). Pre- amplifiers and NAS modules are affixed using Vectran and steel wire rope positioned by swaged stops along the strength member. The tow cable length is 100 m with a diameter of 22 mm that is potted to a hose adapter to break out 12 braided copper wire twisted pair conductors and terminates the tow cable Vectran braid. This array in its current state of development is a low-cost alternative to obtain quality acoustic data from a towed array system. Used here for observation of whale vocalizations, this type of array also has many applications in military sonar and seismic surveying. Maintenance on the array can be performed without the use of special facilities or equipment for dehosing and conveniently uses castor oil as an environmentally safe pressure compensating and coupling fluid. Array development including selection of transducers, NAS modules, acoustic acquisition system, array materials and method of construction with results from several deployments will be discussed. We also present beamformed spectrograms containing humpback whale downsweep moans and underwater blowing (bubbles) sounds associated with feeding on sand lance (Ammodytes dubius). 

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