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1. State of the California Current 2019–2020: Back to the Future With Marine Heatwaves?

   https://doi.org/10.3389/fmars.2021.709454  

   Weber, Edward D. ; Auth, Toby D. ; Baumann-Pickering, Simone ; Baumgartner, Timothy R. ; Bjorkstedt, Eric P. ; Bograd, Steven J. ; Burke, Brian J. ; Cadena-Ramírez, José L. ; Daly, Elizabeth A. ; de la Cruz, Martin ; et al ( August 2021 , Frontiers in Marine Science)

   The California Current System (CCS) has experienced large fluctuations in environmental conditions in recent years that have dramatically affected the biological community. Here we synthesize remotely sensed, hydrographic, and biological survey data from throughout the CCS in 2019–2020 to evaluate how recent changes in environmental conditions have affected community dynamics at multiple trophic levels. A marine heatwave formed in the north Pacific in 2019 and reached the second greatest area ever recorded by the end of summer 2020. However, high atmospheric pressure in early 2020 drove relatively strong Ekman-driven coastal upwelling in the northern portion of the CCS and warm temperature anomalies remained far offshore. Upwelling and cooler temperatures in the northern CCS created relatively productive conditions in which the biomass of lipid-rich copepod species increased, adult krill size increased, and several seabird species experienced positive reproductive success. Despite these conditions, the composition of the fish community in the northern CCS remained a mixture of both warm- and cool-water-associated species. In the southern CCS, ocean temperatures remained above average for the seventh consecutive year. Abundances of juvenile fish species associated with productive conditions were relatively low, and the ichthyoplankton community was dominated by a mixture of oceanic warm-water and cosmopolitan species. Seabird species associated with warm water also occurred at greater densities than cool-water species in the southern CCS. The population of northern anchovy, which has been resurgent since 2017, continued to provide an important forage base for piscivorous fishes, offshore colonies of seabirds, and marine mammals throughout the CCS. Coastal upwelling in the north, and a longer-term trend in warming in the south, appeared to be controlling the community to a much greater extent than the marine heatwave itself. 

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2. Predator–prey dynamics of bald eagles and glaucous‐winged gulls at Protection Island, Washington, USA

   https://doi.org/10.1002/ece3.5011  

   Henson, Shandelle M. ; Desharnais, Robert A. ; Funasaki, Eric T. ; Galusha, Joseph G. ; Watson, James W. ; Hayward, James L. ( March 2019 , Ecology and Evolution)

   Bald eagle (Haliaeetus leucocephalus) populations in North America rebounded in the latter part of the twentieth century, the result of tightened protection and outlawing of pesticides such as DDT. An unintended consequence of recovery may be a negative impact on seabirds. During the 1980s, few bald eagles disturbed a large glaucous‐winged gull (Larus glaucescens) colony on Protection Island, Washington, USA, in the Salish Sea. Breeding gull numbers in this colony rose nearly 50% during the 1980s and early 1990s. Beginning in the 1990s, a dramatic increase in bald eagle activity ensued within the colony, after which began a significant decline in gull numbers.

   To examine whether trends in the gull colony could be explained by eagle activity, we fit a Lotka–Volterra‐type predator–prey model to gull nest count data and Washington State eagle territory data collected in most years between 1980 and 2016. Both species were assumed to grow logistically in the absence of the other.

   The model fits the data with generalizedR² = 0.82, supporting the hypothesis that gull dynamics were due largely to eagle population dynamics.

   Point estimates of the model parameters indicated approach to stable coexistence. Within the 95% confidence intervals for the parameters, however, 11.0% of bootstrapped parameter vectors predicted gull colony extinction.

   Our results suggest that the effects of bald eagle activity on the dynamics of a large gull colony were explained by a predator–prey relationship that included the possibility of coexistence but also the possibility of gull colony extinction. This study serves as a cautionary exploration of the future, not only for gulls on Protection Island, but for other seabirds in the Salish Sea. Managers should monitor numbers of nests in seabird colonies as well as eagle activity within colonies to document trends that may lead to colony extinction.

    

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3. Persistence of southern California giant kelp beds and alongshore variation in nutrient exposure driven by seasonal upwelling and internal waves

   https://doi.org/10.3389/fmars.2023.1007789  

   Leichter, James J. ; Ladah, Lydia B. ; Parnell, P. Ed ; Stokes, M. Dale ; Costa, Matthew T. ; Fumo, James ; Dayton, Paul K. ( March 2023 , Frontiers in Marine Science)

   Kelp beds provide significant ecosystem services and socioeconomic benefits globally, and prominently in coastal zones of the California Current. Their distributions and abundance, however, vary greatly over space and time. Here, we describe long-term patterns of Giant Kelp (Macrocystis pyrifera) sea surface canopy area off the coast of San Diego County from 1983 through 2019 along with recent patterns of water column nitrate (NO₃^-) exposure inferred fromin situtemperature data in 2014 and 2015 at sites spanning 30 km of the coastline near San Diego California, USA. Site-specific patterns of kelp persistence and resilience were associated with ocean and climate dynamics, with total sea surface kelp canopy area varying approximately 33-fold over the almost 4 decades (min 0.34 km²in 1984; max 11.25 km²in 2008, median 4.79 km²). Site-normalized canopy areas showed that recent kelp persistence since 2014 was greater at Point Loma and La Jolla, the largest kelp beds off California, than at the much smaller kelp bed off Cardiff. NO₃^-exposure was estimated from an 11-month time series ofin situwater column temperature collected in 2014 and 2015 at 4 kelp beds, using a relationship between temperature and NO₃^-concentration previously established for the region. The vertical position of the 14.5°C isotherm, an indicator of the main thermocline and nutricline, varied across the entire water column at semidiurnal to seasonal frequencies. We use a novel means of quantifying estimated water column NO₃^-exposure integrated through time (mol-days m^-2) adapted from degree days approaches commonly used to characterize thermal exposures. Water column integrated NO₃^-exposure binned by quarters of the time series showed strong seasonal differences with highest exposure in Mar - May 2015, lowest exposure in Sep - Dec 2014, with consistently highest exposure off Point Loma. The water column integrated NO₃^-signal was filtered to provide estimates of the contribution to total nitrate exposure from high frequency variability (ƒ >= 1 cycle 30 hr^-1) associated predominantly with internal waves, and low frequency variability driven predominantly by seasonal upwelling. While seasonal upwelling accounted for > 90% of NO₃^-exposure across the full year, during warm periods when seasonal upwelling was reduced or absent and NO₃^-exposure was low overall, the proportion due to internal waves increased markedly to 84 to 100% of the site-specific total exposure. The high frequency variability associated with internal waves may supply critical nutrient availability during anomalously warm periods. Overall, these analyses support a hypothesis that differences in NO₃^-exposure among sites due to seasonal upwelling and higher frequency internal wave forcing contribute to spatial patterns in Giant Kelp persistence in southern California. The study period includes anomalously warm surface conditions and the marine heatwave associated with the “Pacific Warm Blob” superimposed on the seasonal thermal signal and corresponding to the onset of a multi-year decline in kelp canopy area and marked differences in kelp persistence among sites. Our analysis suggests that, particularly during periods of warm surface conditions, variation in NO₃^-exposure associated with processes occurring at higher frequencies, including internal waves can be a significant source of NO₃^-exposure to kelp beds in this region. The patterns described here also offer a view of the potential roles of seasonal and higher frequency nutrient dynamics for Giant Kelp persistence in southern California under continuing ocean surface warming and increasing frequency and intensity of marine heatwaves.

    

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4. Effects of wind on the movement, behavior, energetics, and life history of seabirds

   https://doi.org/10.3354/meps14417  

   Thorne, LH ; Clay, TA ; Phillips, RA ; Silvers, LG ; Wakefield, ED ( November 2023 , Marine Ecology Progress Series)

   For decades, studies have highlighted links between wind patterns and the behavior, ecology, distribution, energetics and life history of seabirds. However, only relatively recently have advancements in tracking technologies and improvements in the resolution of globally-available wind data allowed wind impacts on seabirds to be quantified across multiple spatiotemporal scales. Here, we review and synthesize current knowledge of the effects of wind on seabirds. We first describe global patterns of wind circulation and relevant atmospheric processes and discuss the relationship between seabird morphology, flight performance and behavior relative to wind. We then develop a conceptual model linking seabird movement strategies to wind, morphology, flight capabilities and central-place constraint. Finally, we examine how wind influences seabird populations via effects on flight efficiency and energetics, and wind impacts associated with climate variability and severe weather. We conclude by highlighting research priorities for advancing our understanding of the effects of wind on seabird ecology and behavior; these include assessing how and to what extent seabirds use ocean waves for efficient flight, understanding how seabirds sense and anticipate wind patterns, and examining how wind has shaped seabird evolution. Future research should also focus on assessing how wind modulates habitat accessibility, and how this knowledge could be incorporated into theory of seabird habitat use. Moreover, approaches that focus on mechanistic links between climate, wind and demography are needed to assess population-level effects, and will be imperative to understanding how seabirds may be impacted by climate-driven changes to wind patterns.

    

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5. Effects of age, sex, and ENSO phase on foraging and flight performance in Nazca boobies

   https://doi.org/10.1002/ece3.7308  

   Howard, Jennifer L. ; Tompkins, Emily M. ; Anderson, David J. ( March 2021 , Ecology and Evolution)

   Age‐related changes in survival and reproduction are common in seabirds; however, the underlying causes remain elusive. A lack of experience for young individuals, and a decline in foraging performance for old birds, could underlie age‐related variation in reproduction because reproductive success is connected closely to provisioning offspring. For seabirds, flapping flight during foraging trips is physiologically costly; inexperience or senescent decline in performance of this demanding activity might cap delivery of food to the nest, providing a proximate explanation for poor breeding success in young and old age, respectively. We evaluated the hypothesis that young and old Nazca boobies (Sula granti), a Galápagos seabird, demonstrate deficits in foraging outcomes and flight performance. We tagged incubating male and female adults across the life span with both accelerometer and GPS loggers during the incubation periods of two breeding seasons (years), during the 2015 El Niño and the following weak La Niña. We tested the ability of age, sex, and environment to explain variation in foraging outcomes (e.g., mass gained) and flight variables (e.g., wingbeat frequency). Consistent with senescence, old birds gained less mass while foraging than middle‐aged individuals, a marginal effect, and achieved a slower airspeed late in a foraging trip. Contrary to expectations, young birds showed no deficit in foraging outcomes or flight performance, except for airspeed (contingent on environment). Young birds flew slower than middle‐aged birds in 2015, but faster than middle‐aged birds in 2016. Wingbeat frequency, flap–glide ratio, and body displacement (approximating wingbeat strength) failed to predict airspeed and were unaffected by age. Sex influenced nearly all aspects of performance. Environment affected flight performance and foraging outcomes. Boobies' foraging outcomes were better during the extreme 2015 El Niño than during the 2016 weak La Niña, a surprising result given the negative effects tropical seabirds often experience during extreme El Niños.

    

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