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Alice Della Penna

Research Associate

Email

adella@apl.washington.edu

Phone

206-543-9891

Education

B.S. Physics, University of Turin, 2010

M.S. Physics of Complex Systems, University of Turin, 2012

Ph.D. Interdisciplinary Approaches to Life Sciences, Paris Diderot University, 2016

Ph.D. Quantitative Marine Science, University of Tasmania, 2016

Publications

2000-present and while at APL-UW

Global satellite-observed daily vertical migrations of ocean animals

Behrenfeld, M.J., P. Gaube, A. Della Penna, R.T. O'Malley, W.J. Burt, Y. Hu, P.S. Bontempi, D.K. Steinberg, E.S. Boss, D.A. Siegel, C.A. Hostetler, P.D. Torfell, and S.C. Doney, "Global satellite-observed daily vertical migrations of ocean animals," Nature, 576, 257-261, doi:10.1038/s41586-019-1796-9, 2019.

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27 Nov 2019

Every night across the world's oceans, numerous marine animals arrive at the surface of the ocean to feed on plankton after an upward migration of hundreds of metres. Just before sunrise, this migration is reversed and the animals return to their daytime residence in the dark mesopelagic zone (at a depth of 200–1,000 m). This daily excursion, referred to as diel vertical migration (DVM), is thought of primarily as an adaptation to avoid visual predators in the sunlit surface layer and was first recorded using ship-net hauls nearly 200 years ago. Nowadays, DVMs are routinely recorded by ship-mounted acoustic systems (for example, acoustic Doppler current profilers). These data show that night-time arrival and departure times are highly conserved across ocean regions and that daytime descent depths increase with water clarity, indicating that animals have faster swimming speeds in clearer waters. However, after decades of acoustic measurements, vast ocean areas remain unsampled and places for which data are available typically provide information for only a few months, resulting in an incomplete understanding of DVMs. Addressing this issue is important, because DVMs have a crucial role in global ocean biogeochemistry. Night-time feeding at the surface and daytime metabolism of this food at depth provide an efficient pathway for carbon and nutrient export.

Here we use observations from a satellite-mounted light-detection-and-ranging (lidar) instrument to describe global distributions of an optical signal from DVM animals that arrive in the surface ocean at night. Our findings reveal that these animals generally constitute a greater fraction of total plankton abundance in the clear subtropical gyres, consistent with the idea that the avoidance of visual predators is an important life strategy in these regions. Total DVM biomass, on the other hand, is higher in more productive regions in which the availability of food is increased. Furthermore, the 10-year satellite record reveals significant temporal trends in DVM biomass and correlated variations in DVM biomass and surface productivity. These results provide a detailed view of DVM activities globally and a path for refining the quantification of their biogeochemical importance.

Vertical motions and their effects on a biogeochemical tracer in a cyclonic structure finely observed in the Ligurian Sea

Rousselet, L., and 14 others including A. Della Penna, "Vertical motions and their effects on a biogeochemical tracer in a cyclonic structure finely observed in the Ligurian Sea," J. Geophys. Res., 124, 3561-3574, doi:10.1029/2018JC014392, 2019.

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1 Jun 2019

Vertical velocities can be estimated indirectly from in situ observations by theoretical frameworks like the ω‐equation. Direct measures of vertical exchanges are challenging due to their typically ephemeral spatiotemporal scales. In this study we address this problem with an adaptive sampling strategy coupling various biophysical instruments. We analyze the 3‐D organization of a cyclonic mesoscale structure finely sampled during the Observing Submesoscale Coupling At High Resolution cruise in the Ligurian Sea during fall 2015. The observations, acquired with a moving vessel profiler, highlight a subsurface low‐salinity layer (≅50 m), as well as rising isopycnals, generated by geostrophic cyclonic circulation, in the structure's center. Reconstructed 3‐D fields of density and horizontal velocities are used to estimate the vertical velocity field down to 250 m by applying the adiabatic QG ω‐equation, for the first time in this region. The vertical motions are characterized by multipolar patterns of downward and upward velocities on the edges of the structure and significantly smaller vertical velocities in its center. Both the 3‐D distribution of particles (size ≥100 μm), measured with a laser optical plankton counter, and the Synechococcus and Prochlorococcus abundances (cell per cubic meter) measured by flow cytometry are consistent with the 3‐D velocity field. In particular, a secondary vertical recirculation is identified that upwells particles (from 250 to 100 m) along isohalines to the structure's center. Besides demonstrating the effect of vertical patterns on biogeochemical distributions, this case study suggests to use particle matter as a tracer to assess physical dynamics.

Mesoscale eddies influence the movements of mature female white sharks in the Gulf Stream and Sargasso Sea

Gaube, P., C.D. Braun, G.L. Lawson, D.J. McGillicuddy Jr., A. Della Penna, G.B. Skomal, C. Fischer, and S.R. Thorrold, "Mesoscale eddies influence the movements of mature female white sharks in the Gulf Stream and Sargasso Sea," Sci. Rep., 8, 7363, doi:10.1038/s41598-018-25565-8, 2018.

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9 May 2018

Satellite-tracking of mature white sharks (Carcharodon carcharias) has revealed open-ocean movements spanning months and covering tens of thousands of kilometers. But how are the energetic demands of these active apex predators met as they leave coastal areas with relatively high prey abundance to swim across the open ocean through waters often characterized as biological deserts? Here we investigate mesoscale oceanographic variability encountered by two white sharks as they moved through the Gulf Stream region and Sargasso Sea in the North Atlantic Ocean. In the vicinity of the Gulf Stream, the two mature female white sharks exhibited extensive use of the interiors of clockwise-rotating anticyclonic eddies, characterized by positive (warm) temperature anomalies. One tagged white shark was also equipped with an archival tag that indicated this individual made frequent dives to nearly 1,000 m in anticyclones, where it was presumably foraging on mesopelagic prey. We propose that warm temperature anomalies in anticyclones make prey more accessible and energetically profitable to adult white sharks in the Gulf Stream region by reducing the physiological costs of thermoregulation in cold water. The results presented here provide valuable new insight into open ocean habitat use by mature, female white sharks that may be applicable to other large pelagic predators.

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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