Measuring the impact of oceanographic indices on species distribution shifts: The spatially varying effect of cold‐pool extent in the eastern Bering Sea

2019 ◽  
Vol 64 (6) ◽  
pp. 2632-2645 ◽  
Author(s):  
James T. Thorson
Keyword(s):  
Species Distribution ◽  
Bering Sea ◽  
Cold Pool ◽  
Eastern Bering Sea ◽  
Distribution Shifts ◽  
Spatially Varying ◽  
The Impact

scholarly journals Predicted shifts of groundfish distribution in the Eastern Bering Sea under climate change, with implications for fish populations and fisheries management

2020 ◽  
Author(s):  
Christopher N Rooper ◽  
Ivonne Ortiz ◽  
Albert J Hermann ◽  
Ned Laman ◽  
Wei Cheng ◽  
...  
Keyword(s):  
Bering Sea ◽  
Marine Species ◽  
Species Distribution Modelling ◽  
Fish Populations ◽  
Trawl Survey ◽  
Climate Scenarios ◽  
Important Species ◽  
Eastern Bering Sea ◽  
Northern Latitudes ◽  
Distribution Shifts

Abstract Climate-related distribution shifts for marine species are, in general, amplified in northern latitudes. The objective of this study was to predict future distributions of commercially important species in the eastern Bering Sea under six climate scenarios, by incorporating predictions of future oceanographic conditions. We used species distribution modelling to determine potential distribution changes in four time periods (2013–2017, 2030–2039, 2060–2069, and 2090-2099) relative to 1982–2012 for 16 marine fish and invertebrates. Most species were predicted to have significant shifts in the centre of gravity of the predicted abundance, the area occupied, and the proportion of the predicted abundance found in the standard bottom trawl survey area. On average the shifts were modest, averaging 35.2 km (ranging from 1 to 202 km). There were significant differences in the predicted trend for distribution metrics among climate scenarios, with the most extensive changes in distribution resulting from Representative Concentration Pathway 8.5 climate scenarios. The variability in distributional shifts among years and climate scenarios was high, although the magnitudes were low. This study provides a basis for understanding where fish populations might expand or contract in future years. This will provide managers’ information that can help guide appropriate actions under warming conditions.

scholarly journals Modelling spatially dependent predation mortality of eastern Bering Sea walleye pollock, and its implications for stock dynamics under future climate scenarios

2016 ◽  
Vol 73 (5) ◽  
pp. 1330-1342 ◽  
Author(s):  
Paul D. Spencer ◽  
Kirstin K. Holsman ◽  
Stephani Zador ◽  
Nicholas A. Bond ◽  
Franz J. Mueter ◽  
...  
Keyword(s):  
Bering Sea ◽  
Population Model ◽  
Walleye Pollock ◽  
Cold Pool ◽  
Relative Distribution ◽  
Eastern Bering Sea ◽  
Predation Mortality ◽  
Wide Range ◽  
Arrowtooth Flounder ◽  
Pool Area

Abstract Arrowtooth flounder (Atheresthes stomias) are an important predator of juvenile walleye pollock (Gadus chalcogramus) in the eastern Bering Sea (EBS) shelf and have increased 3-fold in biomass from 1977 to 2014. Arrowtooth flounder avoid the summer “cold pool” (bottom water ≤2°C) and variability in cold pool size and location has affected their spatial overlap with juvenile walleye pollock. Developing a method to account for the relationship between climate change and pollock mortality can highlight ecosystem dynamics and contribute to better assessments for fisheries management. Consequently, spatially resolved predation mortality rates were estimated within an age-structured walleye pollock stock assessment population model (based on spatial information on diet and abundance from trawl surveys), along with the effect of sea surface temperature (SST) on pollock recruitment. Projections of SST and cold pool area to 2050 were obtained (or statistically downscaled) from nine global climate models and used within an age-structure population model to project pollock abundance given estimated relationships between environmental variables and predator and prey spatial distributions, pollock recruitment, and maximum rate of arrowtooth flounder consumption. The climate projections show a wide range of variability but an overall trend of increasing SST and decreasing cold pool area. Projected pollock biomass decreased largely due to the negative effect of increased SST on pollock recruitment. A sensitivity analysis indicated that the decline in projected pollock biomass would be exacerbated if arrowtooth flounder increased their relative distribution in the EBS northwest middle shelf (an area of relatively high density of juvenile pollock) in warm years.

Climate warming and the loss of sea ice: the impact of sea-ice variability on the southeastern Bering Sea pelagic ecosystem

2020 ◽  
Author(s):  
George L Hunt ◽  
Ellen M Yasumiishi ◽  
Lisa B Eisner ◽  
Phyllis J Stabeno ◽  
Mary Beth Decker
Keyword(s):  
Sea Ice ◽  
Climate Warming ◽  
Bering Sea ◽  
Ice Cover ◽  
Walleye Pollock ◽  
Pelagic Ecosystem ◽  
Eastern Bering Sea ◽  
Calanus Glacialis ◽  
Class Strength ◽  
The Impact

Abstract We investigated relationships among three metrics of sea-ice cover in eight regions of the eastern Bering Sea and the abundance of Calanus copepods, jellyfish medusae, and year-class strength of walleye pollock (Gadus chalcogrammus). In summer, Calanus spp. were more abundant over the middle shelf when sea ice lingered late into spring, and, to a lesser extent, when February sea-ice cover was heavy. Between 1982 and 1999, there were no significant (p ≤ 0.05) relationships between the amount or timing of sea-ice cover and pollock recruitment. However, between 2000 and 2015, pollock year-class strength was positively correlated with sea ice in the outer and middle shelves, with 17 of 24 regressions significant. Pollock year-class strength was best predicted by days with sea-ice cover after February. Pollock recruitment was positively influenced by copepod numbers, particularly in the middle shelf, with r2 values from 0.36 to 0.47. We hypothesize that the Calanus spp. present in the southeastern Bering Sea are primarily Calanus glacialis that have been advected south in association with sea ice. None of our sea-ice metrics explained the variance in jellyfish biomass. Jellyfish biomass in our study area in the pollock age-0 year was not correlated with pollock recruitment 3 years later.

scholarly journals Absorption and fluorescence properties of chromophoric dissolved organic matter of the eastern Bering Sea in the summer with special reference to the influence of a cold pool

2014 ◽  
Vol 11 (12) ◽  
pp. 3225-3244 ◽  
Author(s):  
E. J. D'Sa ◽  
J. I. Goes ◽  
H. Gomes ◽  
C. Mouw
Keyword(s):  
Bering Sea ◽  
Fluorescence Properties ◽  
Chromophoric Dissolved Organic Matter ◽  
Cold Pool ◽  
Surface Mixed Layer ◽  
Spectral Slope ◽  
Inner Shelf ◽  
Eastern Bering Sea ◽  
Shelf Slope ◽  
The Bering Sea

Abstract. The absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM) are reported for the inner shelf, slope waters and outer shelf regions of the eastern Bering Sea during the summer of 2008, when a warm, thermally stratified surface mixed layer lay over a cold pool (< 2 °C) that occupied the entire middle shelf. CDOM absorption at 355 nm (ag355) and its spectral slope (S) in conjunction with excitation–emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC) revealed large variability in the characteristics of CDOM in different regions of the Bering Sea. PARAFAC analysis aided in the identification of three humic-like (components one, two and five) and two protein-like (a tyrosine-like component three, and a tryptophan-like component four) components. In the extensive shelf region, average absorption coefficients at 355 nm (ag355, m−1) and DOC concentrations (μM) were highest in the inner shelf (0.342 ± 0.11 m−1, 92.67 ± 14.60 μM) and lower in the middle (0.226 ± 0.05 m−1, 78.38 ± 10.64 μM) and outer (0.185 ± 0.05 m−1, 79.24 ± 18.01 μM) shelves, respectively. DOC concentrations, however were not significantly different, suggesting CDOM sources and sinks to be uncoupled from DOC. Mean spectral slopes S were elevated in the middle shelf (24.38 ± 2.25 μm−1) especially in the surface waters (26.87 ± 2.39 μm−1) indicating high rates of photodegradation in the highly stratified surface mixed layer, which intensified northwards in the northern middle shelf likely contributing to greater light penetration and to phytoplankton blooms at deeper depths. The fluorescent humic-like components one, two, and five were most elevated in the inner shelf most likely from riverine inputs. Along the productive "green belt" in the outer shelf/slope region, absorption and fluorescence properties indicated the presence of fresh and degraded autochthonous DOM. Near the Unimak Pass region of the Aleutian Islands, low DOC and ag355 (mean 66.99 ± 7.94 μM; 0.182 ± 0.05 m−1) and a high S (mean 25.95 ± 1.58 μm−1) suggested substantial photobleaching of the Alaska Coastal Water, but high intensities of humic-like and protein-like fluorescence suggested sources of fluorescent DOM from coastal runoff and glacier meltwaters during the summer. The spectral slope S vs. ag355 relationship revealed terrestrial and oceanic end members along with intermediate water masses that were modeled using nonlinear regression equations that could allow water mass differentiation based on CDOM optical properties. Spectral slope S was negatively correlated (r2 = 0.79) with apparent oxygen utilization (AOU) for waters extending from the middle shelf into the deep Bering Sea indicating increasing microbial alteration of CDOM with depth. Although our data show that the CDOM photochemical environment of the Bering Sea is complex, our current information on its optical properties will aid in better understanding of the biogeochemical role of CDOM in carbon budgets in relation to the annual sea ice and phytoplankton dynamics, and to improved algorithms of ocean color remote sensing for this region.

scholarly journals Absorption and fluorescence properties of the eastern Bering Sea in the summer with special reference to the influence of a Cold Pool

2013 ◽  
Vol 10 (12) ◽  
pp. 19109-19154
Author(s):  
E. J. D'Sa ◽  
J. I. Goes ◽  
H. Gomes ◽  
C. Mouw
Keyword(s):  
Mixed Layer ◽  
Bering Sea ◽  
Outer Shelf ◽  
Fluorescence Properties ◽  
Cold Pool ◽  
Surface Mixed Layer ◽  
Inner Shelf ◽  
Eastern Bering Sea ◽  
Shelf Slope ◽  
The Bering Sea

Abstract. The absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM) are reported for the inner shelf, slope waters and outer shelf regions of the eastern Bering Sea during the summer of 2008, when a warm, thermally stratified surface mixed layer lay over a Cold Pool (< 2 °C) that occupied the entire middle shelf. CDOM absorption at 355 nm (ag355) and its spectral slope (S) in conjunction with excitation emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC) revealed large variability in the characteristics of CDOM in different regions of the Bering Sea. PARAFAC analysis aided in the identification of three humic-like (components 1, 2 and 5) and two protein-like (a tyrosine-like component 3, and a tryptophan-like component 4) components. In the extensive shelf region, average absorption coefficients at 355 nm (ag355 m–1) and DOC concentrations (μM) were highest in the inner shelf (0.342 ± 0.11 m–1, 92.67 ± 14.60 μM) and lower in the middle (0.226 ± 0.05 m–1, 78.38 ± 10.64 μM) and outer (0.176 ± 0.05 m–1, 80.73 ± 18.11 μM) shelves, respectively. Mean spectral slopes S were elevated in the middle shelf (24.38 ± 2.25 μm–1) especially in the surface waters (26.87 ± 2.39 μm–1) indicating high rates of photodegradation in the highly stratified surface mixed layer, which intensified northwards in the northern middle shelf likely contributing to greater light penetration and to phytoplankton blooms at deeper depths. The fluorescent humic-like components 1, 2, and 5 were most elevated in the inner shelf most likely from riverine inputs. Measurements at depth in slope waters (> 250 m) revealed low values of ag355 (0.155 ± 0.03 m–1) and S (15.45 ± 1.78 μm–1) indicative of microbial degradation of CDOM in deep waters. DOC concentrations, however were not significantly different suggesting CDOM sources and sinks to be uncoupled from DOC. Along the productive "green belt" in the outer shelf/slope region, absorption and fluorescence properties indicated the presence of fresh and degraded autochthonous DOM. Near the Unimak Pass region of the Aleutian Islands, low DOC and ag355 (mean 66.99 ± 7.94 μM; 0.182 ± 0.05 m–1) and a high S (mean 25.95 ± 1.58 μm–1) suggested substantial photobleaching of the Alaska Coastal Waters, but high intensities of humic-like and protein-like fluorescence suggested sources of fluorescent DOM from coastal runoff and glacier melt waters during the summer. Although our data show that the CDOM photochemical environment of the Bering Sea is complex, our current information on its optical properties will aid in better understanding of the biogeochemical role of CDOM in carbon budgets in relation to the annual sea ice and phytoplankton dynamics, and to improved algorithms of ocean color remote sensing for this region.

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