Steinberg Deborah K.

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Steinberg

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Deborah K.

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West Antarctic Peninsula : an ice-dependent coastal marine ecosystem in transition

(The Oceanography Society, 2013-09) Ducklow, Hugh W. ; Fraser, William R. ; Meredith, Michael P. ; Stammerjohn, Sharon E. ; Doney, Scott C. ; Martinson, Douglas G. ; Sailley, Sevrine F. ; Schofield, Oscar M. E. ; Steinberg, Deborah K. ; Venables, Hugh J. ; Amsler, Charles D.

The extent, duration, and seasonality of sea ice and glacial discharge strongly influence Antarctic marine ecosystems. Most organisms' life cycles in this region are attuned to ice seasonality. The annual retreat and melting of sea ice in the austral spring stratifies the upper ocean, triggering large phytoplankton blooms. The magnitude of the blooms is proportional to the winter extent of ice cover, which can act as a barrier to wind mixing. Antarctic krill, one of the most abundant metazoan populations on Earth, consume phytoplankton blooms dominated by large diatoms. Krill, in turn, support a large biomass of predators, including penguins, seals, and whales. Human activity has altered even these remote ecosystems. The western Antarctic Peninsula region has warmed by 7°C over the past 50 years, and sea ice duration has declined by almost 100 days since 1978, causing a decrease in phytoplankton productivity in the northern peninsula region. Besides climate change, Antarctic marine systems have been greatly altered by harvesting of the great whales and now krill. It is unclear to what extent the ecosystems we observe today differ from the pristine state.
High particle export over the continental shelf of the west Antarctic Peninsula

(American Geophysical Union, 2010-11-24) Buesseler, Ken O. ; McDonnell, Andrew M. P. ; Schofield, Oscar M. E. ; Steinberg, Deborah K. ; Ducklow, Hugh W.

Drifting cylindrical traps and the flux proxy 234Th indicate more than an order of magnitude higher sinking fluxes of particulate carbon and 234Th in January 2009 than measured by a time-series conical trap used regularly on the shelf of the west Antarctic Peninsula (WAP). The higher fluxes measured in this study have several implications for our understanding of the WAP ecosystem. Larger sinking fluxes result in a revised export efficiency of at least 10% (C flux/net primary production) and a requisite lower regeneration efficiency in surface waters. High fluxes also result in a large supply of sinking organic matter to support subsurface and benthic food webs on the continental shelf. These new findings call into question the magnitude of seasonal and interannual variability in particle flux and reaffirm the difficulty of using moored conical traps as a quantitative flux collector in shallow waters.
WAP-1D-VAR v1.0: development and evaluation of a one-dimensional variational data assimilation model for the marine ecosystem along the West Antarctic Peninsula

(European Geosciences Union, 2021-08-12) Kim, Hyewon Heather ; Luo, Ya-Wei ; Ducklow, Hugh W. ; Schofield, Oscar M. E. ; Steinberg, Deborah K. ; Doney, Scott C.

The West Antarctic Peninsula (WAP) is a rapidly warming region, with substantial ecological and biogeochemical responses to the observed change and variability for the past decades, revealed by multi-decadal observations from the Palmer Antarctica Long-Term Ecological Research (LTER) program. The wealth of these long-term observations provides an important resource for ecosystem modeling, but there has been a lack of focus on the development of numerical models that simulate time-evolving plankton dynamics over the austral growth season along the coastal WAP. Here, we introduce a one-dimensional variational data assimilation planktonic ecosystem model (i.e., the WAP-1D-VAR v1.0 model) equipped with a model parameter optimization scheme. We first demonstrate the modified and newly added model schemes to the pre-existing food web and biogeochemical components of the other ecosystem models that WAP-1D-VAR model was adapted from, including diagnostic sea-ice forcing and trophic interactions specific to the WAP region. We then present the results from model experiments where we assimilate 11 different data types from an example Palmer LTER growth season (October 2002–March 2003) directly related to corresponding model state variables and flows between these variables. The iterative data assimilation procedure reduces the misfits between observations and model results by 58 %, compared to before optimization, via an optimized set of 12 parameters out of a total of 72 free parameters. The optimized model results capture key WAP ecological features, such as blooms during seasonal sea-ice retreat, the lack of macronutrient limitation, and modeled variables and flows comparable to other studies in the WAP region, as well as several important ecosystem metrics. One exception is that the model slightly underestimates particle export flux, for which we discuss potential underlying reasons. The data assimilation scheme of the WAP-1D-VAR model enables the available observational data to constrain previously poorly understood processes, including the partitioning of primary production by different phytoplankton groups, the optimal chlorophyll-to-carbon ratio of the WAP phytoplankton community, and the partitioning of dissolved organic carbon pools with different lability. The WAP-1D-VAR model can be successfully employed to link the snapshots collected by the available data sets together to explain and understand the observed dynamics along the coastal WAP.
Penguin biogeography along the West Antarctic Peninsula : testing the canyon hypothesis with Palmer LTER observations

(The Oceanography Society, 2013-09) Schofield, Oscar M. E. ; Ducklow, Hugh W. ; Bernard, Kim S. ; Doney, Scott C. ; Patterson-Fraser, Donna ; Gorman, Kristen ; Martinson, Douglas G. ; Meredith, Michael P. ; Saba, Grace ; Stammerjohn, Sharon E. ; Steinberg, Deborah K. ; Fraser, William R.

The West Antarctic Peninsula (WAP) is home to large breeding colonies of the ice-dependent Antarctic Adélie penguin (Pygoscelis adeliae). Although the entire inner continental shelf is highly productive, with abundant phytoplankton and krill populations, penguin colonies are distributed heterogeneously along the WAP. This ecological conundrum targets a long-standing question of interest: what environmental factors structure the locations of Adélie penguin "hot spots" throughout the WAP?
Modeling polar marine ecosystem functions guided by bacterial physiological and taxonomic traits

(European Geosciences Union, 2022-01-06) Kim, Hyewon Heather ; Bowman, Jeff S. ; Luo, Ya-Wei ; Ducklow, Hugh W. ; Schofield, Oscar M. E. ; Steinberg, Deborah K. ; Doney, Scott C.

Heterotrophic marine bacteria utilize organic carbon for growth and biomass synthesis. Thus, their physiological variability is key to the balance between the production and consumption of organic matter and ultimately particle export in the ocean. Here we investigate a potential link between bacterial traits and ecosystem functions in the rapidly warming West Antarctic Peninsula (WAP) region based on a bacteria-oriented ecosystem model. Using a data assimilation scheme, we utilize the observations of bacterial groups with different physiological traits to constrain the group-specific bacterial ecosystem functions in the model. We then examine the association of the modeled bacterial and other key ecosystem functions with eight recurrent modes representative of different bacterial taxonomic traits. Both taxonomic and physiological traits reflect the variability in bacterial carbon demand, net primary production, and particle sinking flux. Numerical experiments under perturbed climate conditions demonstrate a potential shift from low nucleic acid bacteria to high nucleic acid bacteria-dominated communities in the coastal WAP. Our study suggests that bacterial diversity via different taxonomic and physiological traits can guide the modeling of the polar marine ecosystem functions under climate change.
Zooplankton taxonomic data from MOCNESS and IONESS tows from VERTIGO cruises KM0414, ZHNG09RR from the Hawaiian Islands HOT Site, NW SubArctic Pacific Ocean K2 Site, 2004-2005 (VERTIGO project)

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-01-16) Steinberg, Deborah K.

Zooplankton taxonomic data from MOCNESS and IONESS tows from VERTIGO cruises KM0414, ZHNG09RR from the Hawaiian Islands HOT Site, NW SubArctic Pacific Ocean K2 Site, 2004-2005 For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/3014
Mesozooplankton biomass estimates from MOCNESS tows collected from R/V Oceanus cruises : OC415-01, OC415-03, OC404-01 and OC404-04 from the Sargasso Sea from June 14, 2004 to August 24, 2005 (EDDIES project)

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2011-10-13) Steinberg, Deborah K. ; Goldthwait, Sarah A.

The Eddies Dynamics, Mixing, Export, and Species composition (EDDIES) mesozooplankton biomass data set includes estimates of mesozooplankton biomass determined from MOCNESS plankton net tows. Zooplankton biomass estimates were determined from 1 m^2, 150 micron mesh MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System) tows. The following discrete depth intervals were sampled on the upcast: 0-50, 50-100, 100-150, 150-200, 200-300, 300-400, 400-500, 500-600, and 600-700 m. Generally paired tows during the day (9:30-15:00 local time) and night (21:30-03:00) were performed at each station. A single tow generally covered 5-15 km. The nominal position (lat_n and lon_n) for each tow is the position at the mid depth 200-300m sampling interval. Table 1 (pg 1362) of Goldthwait and Steinberg (2008) is a sequential list of all MOCNESS mesozooplankton tows and includes eddy identification number and location. Each sample was size-fractionated using nested sieves of 0.15 mm, 0.5 mm, 1 mm, 2mm, and 5 mm mesh. Zooplankton in each size class were transferred onto pre-weighed 0.15 mm nitex mesh filters and rinsed with deionized water. Samples were then dried for 24 hours at 60 degrees C and weighed.
CTD stations from the R/V Atlantic Explorer AE0922 in the North Atlantic, Bermuda BATS region during 2009 (TZEX project)

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-12-09) Buesseler, Kenneth O. ; Lamborg, Carl ; Lomas, Michael W. ; Siegel, David ; Steinberg, Deborah K. ; Valdes, Jim

CTD stations from the R/V Atlantic Explorer AE0922 in the North Atlantic, Bermuda BATS region during 2009 (TZEX project) For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/3457
Cruise event log from the R/V Atlantic Explorer AE0922 cruise in the North Atlantic, Bermuda BATS region during 2009 (TZEX project)

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-12-09) Buesseler, Kenneth O. ; Lamborg, Carl ; Lomas, Michael W. ; Siegel, David ; Steinberg, Deborah K. ; Valdes, Jim

Cruise event log from the R/V Atlantic Explorer AE0922 cruise in the North Atlantic, Bermuda BATS region during 2009 (TZEX project) For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/3454
Changes in fecal pellet characteristics with depth as indicators of zooplankton repackaging of particles in the mesopelagic zone of the subtropical and subarctic North Pacific Ocean

( 2008-01-31) Wilson, Stephanie E. ; Steinberg, Deborah K. ; Buesseler, Ken O.

We investigated how fecal pellet characteristics change with depth in order to quantify the extent of particle repackaging by mesopelagic zooplankton in two contrasting open-ocean systems. Material from neutrally buoyant sediment traps deployed in the summer of 2004 and 2005 at 150, 300, and 500 m was analyzed from both a mesotrophic (Japanese time-series station K2) and an oligotrophic (Hawaii Ocean Time series-HOT station ALOHA) environment in the Pacific Ocean as part of the VERtical Transport In the Global Ocean (VERTIGO) project. We quantified changes in the flux, size, shape, and color of particles recognizable as zooplankton fecal pellets to determine how these parameters varied with depth and location. Flux of K2 fecal pellet particulate organic carbon (POC) at 150 and 300 m was 4-5 times higher than at ALOHA, and at all depths, fecal pellets were 2-5 times larger at K2, reflective of the disparate zooplankton community structure at the two sites. At K2, the proportion of POC flux that consisted of fecal pellets generally decreased with depth from 20% at 150 m to 5% at 500 m, whereas at ALOHA this proportion increased with depth (and was more variable) from 14% to 35%. This difference in the fecal fraction of POC with increasing depth is hypothesized to be due to differences in the extent of zooplankton-mediated fragmentation (coprohexy) and in zooplankton community structure between the two locations. Both regions provided indications of sinking particle repackaging and zooplankton carnivory in the mesopelagic. At ALOHA this was reflected in a significant increase in the mean flux of larvacean fecal pellets from 150 to 500 m of 3 to 46 μg C m-2 d-1, respectively, and at K2 a large peak in larvacean mean pellet flux at 300 m of 3.1 mg C m-2 d-1. Peaks in red pellets produced by carnivores occurred at 300 m at K2, and a variety of other fecal pellet classes showed significant changes in their distribution with depth. There was also evidence of substantially higher pellet fragmentation at K2 with nearly double the ratio of broken:intact pellets at 150 and 300 m (mean of 67% and 64%, respectively ) than at ALOHA where the proportion of broken pellets remained constant with depth (mean 35%). Variations in zooplankton size and community structure within the mesopelagic zone can thus differentially alter the transfer efficiency of sinking POC.
Carbon fluxes and pelagic ecosystem dynamics near two western Antarctic Peninsula Adélie penguin colonies : an inverse model approach

(Inter-Research, 2013-10-31) Sailley, Sevrine F. ; Ducklow, Hugh W. ; Moeller, Holly V. ; Fraser, William R. ; Schofield, Oscar M. E. ; Steinberg, Deborah K. ; Garzio, Lori M. ; Doney, Scott C.

An inverse food-web model for the western Antarctic Peninsula (WAP) pelagic food web was constrained with data from Palmer Long Term Ecological Research (PAL-LTER) project annual austral summer sampling cruises. Model solutions were generated for 2 regions with Adélie penguin Pygoscelis adeliae colonies presenting different population trends (a northern and a southern colony) for a 12 yr period (1995-2006). Counter to the standard paradigm, comparisons of carbon flow through bacteria, microzooplankton, and krill showed that the diatom-krill-top predator food chain is not the dominant pathway for organic carbon exchanges. The food web is more complex, including significant contributions by microzooplankton and the microbial loop. Using both inverse model results and network indices, it appears that in the northern WAP the food web is dominated by the microbial food web, with a temporal trend toward its increasing importance. The dominant pathway for the southern WAP food web varies from year to year, with no detectable temporal trend toward dominance of microzooplankton versus krill. In addition, sensitivity analyses indicated that the northern colony of Adélie penguins, whose population size has been declining over the past 35 yr, appears to have sufficient krill during summer to sustain its basic metabolic needs and rear chicks, suggesting the importance of other processes in regulating the Adélie population decline.
Towards a transformative understanding of the ocean’s biological pump: Priorities for future research - Report on the NSF Biology of the Biological Pump Workshop

(Ocean Carbon & Biogeochemistry (OCB) Program, 2016-08-24) Burd, Adrian B. ; Buchan, Alison ; Church, Matthew J. ; Landry, Michael R. ; McDonnell, Andrew M. P. ; Passow, Uta ; Steinberg, Deborah K. ; Benway, Heather M.

The net transfer of organic matter from the surface to the deep ocean is a key function of ocean food webs. The combination of biological, physical, and chemical processes that contribute to and control this export is collectively known as the “biological pump”, and current estimates of the global magnitude of this export range from 5 – 12 Pg C yr-1. This material can be exported in dissolved or particulate form, and many of the biological processes that regulate the composition, quantity, timing, and distribution of this export are poorly understood or constrained. Export of organic material is of fundamental importance to the biological and chemical functioning of the ocean, supporting deep ocean food webs and controlling the vertical and horizontal segregation of elements throughout the ocean. Remineralization of exported organic matter in the upper mesopelagic zone provides nutrients for surface production, while material exported to depths of 1000 m or more is generally considered to be sequestered — i.e. out of contact with the atmosphere for centuries or longer. The ability to accurately model a system is a reflection of the degree to which the system is understood. In the case of export, semi-empirical and simple mechanistic models show a wide range of predictive skill. This is, in part, due to the sparseness of available data, which impedes our inability to accurately represent, or even include, all relevant processes (sometimes for legitimate computational reasons). Predictions will remain uncertain without improved understanding and parameterization of key biological processes affecting export.
Microzooplankton grazing along the Western Antarctic Peninsula

(Inter-Research, 2013-09-18) Garzio, Lori M. ; Steinberg, Deborah K. ; Erickson, Matthew ; Ducklow, Hugh W.

The significance of microzooplankton as grazers in pelagic ecosystems has been established, yet relatively few studies of microzooplankton grazing, compared to that of macrozooplankton, have been conducted in the Southern Ocean. We report phytoplankton and bacterial growth and grazing mortality rates along the Western Antarctic Peninsula (WAP), a region of rapid climate change. Growth and grazing rates were determined by dilution experiments at select stations along the WAP in January of 2009 to 2011 and in the nearshore waters near Palmer Station in February and March 2011. Microzooplankton exerted higher grazing pressure on bacteria compared to phytoplankton along the WAP and also selectively grazed on smaller phytoplankton (picoautotrophs and nanophytoplankton) and on the more actively growing (high nucleic acid) bacterial cells. Among all phytoplankton size classes, growth rates ranged from undetectable (i.e. not significant; NS) to 0.99 d-1, grazing mortality rates were NS to 0.56 d-1, and microzooplankton removed <100% of daily phytoplankton production in all but one experiment. For high and low nucleic acid content bacteria, growth rates were NS to 0.95 d-1, and grazing mortality rates were NS to 0.43 d-1; microzooplankton often removed >100% of daily bacterial production. There was a significant (albeit weak) exponential relationship between temperature and phytoplankton mortality, although the range of experimental temperatures was small. The present study provides a reference point of microzooplankton grazing impact along the WAP in the summer and contributes valuable information to studies modeling the flow of carbon through the WAP food web, improving our ability to predict climate-induced changes in the WAP ecosystem.
VERTIGO (VERtical Transport In the Global Ocean) : a study of particle sources and flux attenuation in the North Pacific

( 2008-03-21) Buesseler, Ken O. ; Trull, Thomas W. ; Steinberg, Deborah K. ; Silver, Mary W. ; Siegel, David A. ; Saitoh, S.-I. ; Lamborg, Carl H. ; Lam, Phoebe J. ; Karl, David M. ; Jiao, N. Z. ; Honda, Makio C. ; Elskens, Marc ; Dehairs, Frank ; Brown, S. I. ; Boyd, Philip W. ; Bishop, James K. B. ; Bidigare, Robert R.

The VERtical Transport In the Global Ocean (VERTIGO) study examined particle sources and fluxes through the ocean’s “twilight zone” (defined here as depths below the euphotic zone to 1000 m). Interdisciplinary process studies were conducted at contrasting sites off Hawaii (ALOHA) and in the NW Pacific (K2) during 3 week occupations in 2004 and 2005, respectively. We examine in this overview paper the contrasting physical, chemical and biological settings and how these conditions impact the source characteristics of the sinking material and the transport efficiency through the twilight zone. A major finding in VERTIGO is the considerably lower transfer efficiency (Teff) of particulate organic carbon (POC), POC flux 500 / 150 m, at ALOHA (20%) vs. K2 (50%). This efficiency is higher in the diatom-dominated setting at K2 where silica-rich particles dominate the flux at the end of a diatom bloom, and where zooplankton and their pellets are larger. At K2, the drawdown of macronutrients is used to assess export and suggests that shallow remineralization above our 150 m trap is significant, especially for N relative to Si. We explore here also surface export ratios (POC flux/primary production) and possible reasons why this ratio is higher at K2, especially during the first trap deployment. When we compare the 500 m fluxes to deep moored traps, both sites lose about half of the sinking POC by >4000 m, but this comparison is limited in that fluxes at depth may have both a local and distant component. Certainly, the greatest difference in particle flux attenuation is in the mesopelagic, and we highlight other VERTIGO papers that provide a more detailed examination of the particle sources, flux and processes that attenuate the flux of sinking particles. Ultimately, we contend that at least three types of processes need to be considered: heterotrophic degradation of sinking particles, zooplankton migration and surface feeding, and lateral sources of suspended and sinking materials. We have evidence that all of these processes impacted the net attenuation of particle flux vs. depth measured in VERTIGO and would therefore need to be considered and quantified in order to understand the magnitude and efficiency of the ocean’s biological pump.
Revisiting carbon flux through the ocean's twilight zone

(American Association for the Advancement of Science, 2007-04-27) Buesseler, Ken O. ; Lamborg, Carl H. ; Boyd, Philip W. ; Lam, Phoebe J. ; Trull, Thomas W. ; Bidigare, Robert R. ; Bishop, James K. B. ; Casciotti, Karen L. ; Dehairs, Frank ; Elskens, Marc ; Honda, Makio C. ; Karl, David M. ; Siegel, David A. ; Silver, Mary W. ; Steinberg, Deborah K. ; Valdes, James R. ; Van Mooy, Benjamin A. S. ; Wilson, Stephanie E.
Elevated biomass of mesozooplankton and enhanced fecal pellet flux in cyclonic and mode-water eddies in the Sargasso Sea

(Elsevier B.V., 2008-05-07) Goldthwait, Sarah A. ; Steinberg, Deborah K.
An assessment of the use of sediment traps for estimating upper ocean particle fluxes

(Sears Foundation for Marine Research, 2007-05) Buesseler, Ken O. ; Antia, Avan N. ; Chen, Min ; Fowler, Scott W. ; Gardner, Wilford D. ; Gustafsson, Orjan ; Harada, Koh ; Michaels, Anthony F. ; Rutgers van der Loeff, Michiel M. ; Sarin, Manmohan M. ; Steinberg, Deborah K. ; Trull, Thomas W.

This review provides an assessment of sediment trap accuracy issues by gathering data to address trap hydrodynamics, the problem of zooplankton "swimmers," and the solubilization of material after collection. For each topic, the problem is identified, its magnitude and causes reviewed using selected examples, and an update on methods to correct for the potential bias or minimize the problem using new technologies is presented. To minimize hydrodynamic biases due to flow over the trap mouth, the use of neutrally buoyant sediment traps is encouraged. The influence of swimmers is best minimized using traps that limit zooplankton access to the sample collection chamber. New data on the impact of different swimmer removal protocols at the US time-series sites HOT and BATS are compared and shown to be important. Recent data on solubilization are compiled and assessed suggesting selective losses from sinking particles to the trap supernatant after collection, which may alter both fluxes and ratios of elements in long term and typically deeper trap deployments. Different methods are needed to assess shallow and short- term trap solubilization effects, but thus far new incubation experiments suggest these impacts to be small for most elements. A discussion of trap calibration methods reviews independent assessments of flux, including elemental budgets, particle abundance and flux modeling, and emphasizes the utility of U-Th radionuclide calibration methods.
Contributions of long-term research and time-series observations to marine ecology and biogeochemistry

( 2008-05-02) Ducklow, Hugh W. ; Doney, Scott C. ; Steinberg, Deborah K.

Time-series observations form a critical element of oceanography. New interdisciplinary efforts launched in the past two decades complement the few earlier, longer-running time series in building a better, though still poorly-resolved, picture of lower-frequency ocean variability, the climate processes driving it, and its implications for foodweb dynamics, carbon storage and climate feedbacks. Time-series also enlarge our understanding of ecological processes and are integral for improving models of physical-biogeochemical-ecological ocean dynamics. The major time-series observatories go well beyond simple monitoring of core ocean properties, although that important activity forms the critical center of all time-series efforts. Modern ocean time series have major process and experimental components, entrain ancillary programs and have integrated modeling programs for deriving better understanding of the observations and the changing, three-dimensional ocean in which the observatories are embedded.
De novo transcriptome assembly of the Southern Ocean copepod Rhincalanus gigas sheds light on developmental changes in gene expression

(Elsevier, 2021-01-29) Berger, Cory A. ; Steinberg, Deborah K. ; Copley, Nancy ; Tarrant, Ann M.

Copepods are small crustaceans that dominate most zooplankton communities in terms of both abundance and biomass. In the polar oceans, a subset of large lipid-storing copepods occupy central positions in the food web because of their important role in linking phytoplankton and microzooplankton with higher trophic levels. In this paper, we generated a high-quality de novo transcriptome for Rhincalanus gigas, the largest—and among the most abundant—of the Southern Ocean copepods. We then conducted transcriptional profiling to characterize the developmental transition between late-stage juveniles and adult females. We found that juvenile R. gigas substantially upregulate lipid synthesis and glycolysis pathways relative to females, as part of a developmental gene expression program that also implicates processes such as muscle growth, chitin formation, and ion transport. This study provides the first transcriptional profile of a developmental transition within Rhincalanus gigas or any endemic Southern Ocean copepod, thereby extending our understanding of copepod molecular physiology.
Long‐term patterns in ecosystem phenology near Palmer Station, Antarctica, from the perspective of the Adélie penguin

(Ecological Society of America, 2023-02-10) Cimino, Megan A. ; Conroy, John A. ; Connors, Elizabeth ; Bowman, Jeff ; Corso, Andrew ; Ducklow, Hugh ; Fraser, William ; Friedlaender, Ari ; Kim, Heather Hyewon ; Larsen, Gregory D. ; Moffat, Carlos ; Nichols, Ross ; Pallin, Logan ; Patterson‐Fraser, Donna ; Roberts, Darren ; Roberts, Megan ; Steinberg, Deborah K. ; Thibodeau, Patricia ; Trinh, Rebecca ; Schofield, Oscar ; Stammerjohn, Sharon

Climate change is leading to phenological shifts across a wide range of species globally. Polar oceans are hotspots of rapid climate change where sea ice dynamics structure ecosystems and organismal life cycles are attuned to ice seasonality. To anticipate climate change impacts on populations and ecosystem services, it is critical to understand ecosystem phenology to determine species activity patterns, optimal environmental windows for processes like reproduction, and the ramifications of ecological mismatches. Since 1991, the Palmer Antarctica Long‐Term Ecological Research (LTER) program has monitored seasonal dynamics near Palmer Station. Here, we review the species that occupy this region as year‐round residents, seasonal breeders, or periodic visitors. We show that sea ice retreat and increasing photoperiod in the spring trigger a sequence of events from mid‐November to mid‐February, including Adélie penguin clutch initiation, snow melt, calm conditions (low winds and warm air/sea temperature), phytoplankton blooms, shallow mixed layer depths, particulate organic carbon flux, peak humpback whale abundances, nutrient drawdown, and bacterial accumulation. Subsequently, from May to June, snow accumulates, zooplankton indicator species appear, and sea ice advances. The standard deviation in the timing of most events ranged from ~20 to 45 days, which was striking compared with Adélie penguin clutch initiation that varied <1 week. In general, during late sea ice retreat years, events happened later (~5 to >30 days) than mean dates and the variability in timing was low (<20%) compared with early ice retreat years. Statistical models showed the timing of some events were informative predictors (but not sole drivers) of other events. From an Adélie penguin perspective, earlier sea ice retreat and shifts in the timing of suitable conditions or prey characteristics could lead to mismatches, or asynchronies, that ultimately influence chick survival via their mass at fledging. However, more work is needed to understand how phenological shifts affect chick thermoregulatory costs and the abundance, availability, and energy content of key prey species, which support chick growth and survival. While we did not detect many long‐term phenological trends, we expect that when sea ice trends become significant within our LTER time series, phenological trends and negative effects from ecological mismatches will follow.

Steinberg Deborah K.

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