scholarly journals Propagation of the 2014–2016 Northeast Pacific Marine Heatwave Through the Salish Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Tarang Khangaonkar ◽  
Adi Nugraha ◽  
Su Kyong Yun ◽  
Lakshitha Premathilake ◽  
Julie E. Keister ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Elevated Temperatures ◽  
Zooplankton Biomass ◽  
Direct Result ◽  
Biogeochemical Model ◽  
Nutrient Loads ◽  
Salish Sea ◽  
Northeast Pacific ◽  
Mesozooplankton Biomass ◽  
Estuarine Exchange

Effects and impacts of the Northeast Pacific marine heatwave of 2014–2016 on the inner coastal estuarine waters of the Salish Sea were examined using a combination of monitoring data and an established three-dimensional hydrodynamic and biogeochemical model of the region. The anomalous high temperatures reached the U.S. Pacific Northwest continental shelf toward the end of 2014 and primarily entered the Salish Sea waters through an existing strong estuarine exchange. Elevated temperatures up to + 2.3°C were observed at the monitoring stations throughout 2015 and 2016 relative to 2013 before dissipating in 2017. The hydrodynamic and biogeochemical responses to this circulating high-temperature event were examined using the Salish Sea Model over a 5-year window from 2013 to 2017. Responses of conventional water-quality indicator variables, such as temperature and salinity, nutrients and phytoplankton, zooplankton, dissolved oxygen, and pH, were evaluated relative to a baseline without the marine heatwave forcing. The simulation results relative to 2014 show an increase in biological activity (+14%, and 6% Δ phytoplankton biomass, respectively) during the peak heatwave year 2015 and 2016 propagating toward higher zooplankton biomass (+14%, +18% Δ mesozooplankton biomass). However, sensitivity tests show that this increase was a direct result of higher freshwater and associated nutrient loads accompanied by stronger estuarine exchange with the Pacific Ocean rather than warming due to the heatwave. Strong vertical circulation and mixing provided mitigation with only ≈+0.6°C domain-wide annual average temperature increase within Salish Sea, and served as a physical buffer to keep waters cooler relative to the continental shelf during the marine heatwave.

scholarly journals Quantifying spatiotemporal variability in zooplankton dynamics in the Gulf of Mexico with a physical–biogeochemical model

2020 ◽  
Vol 17 (13) ◽  
pp. 3385-3407 ◽  
Author(s):  
Taylor A. Shropshire ◽  
Steven L. Morey ◽  
Eric P. Chassignet ◽  
Alexandra Bozec ◽  
Victoria J. Coles ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Secondary Production ◽  
Food Source ◽  
Net Primary Production ◽  
Zooplankton Biomass ◽  
Spatiotemporal Variability ◽  
Biogeochemical Model ◽  
Feeding Mode ◽  
Mesozooplankton Biomass ◽  
Biogeochemical Models

Abstract. Zooplankton play an important role in global biogeochemistry, and their secondary production supports valuable fisheries of the world's oceans. Currently, zooplankton standing stocks cannot be estimated using remote sensing techniques. Hence, coupled physical–biogeochemical models (PBMs) provide an important tool for studying zooplankton on regional and global scales. However, evaluating the accuracy of zooplankton biomass estimates from PBMs has been a major challenge due to sparse observations. In this study, we configure a PBM for the Gulf of Mexico (GoM) from 1993 to 2012 and validate the model against an extensive combination of biomass and rate measurements. Spatial variability in a multidecadal database of mesozooplankton biomass for the northern GoM is well resolved by the model with a statistically significant (p < 0.01) correlation of 0.90. Mesozooplankton secondary production for the region averaged 66±8×109 kg C yr−1, equivalent to ∼10 % of net primary production (NPP), and ranged from 51 to 82×109 kg C yr−1, with higher secondary production inside cyclonic eddies and substantially reduced secondary production in anticyclonic eddies. Model results from the shelf regions suggest that herbivory is the dominant feeding mode for small mesozooplankton (< 1 mm), whereas larger mesozooplankton are primarily carnivorous. In open-ocean oligotrophic waters, however, both mesozooplankton groups show proportionally greater reliance on heterotrophic protists as a food source. This highlights an important role of microbial and protistan food webs in sustaining mesozooplankton biomass in the GoM, which serves as the primary food source for early life stages of many commercially important fish species, including tuna.

Consequences of nutrient load reductions for carbon and alkalinity dynamics within the region of freshwater influence of River Elbe

2021 ◽  
Author(s):  
Johannes Paetsch ◽  
Helmuth Thomas
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Sulfate Reduction ◽  
Biogeochemical Model ◽  
Time Interval ◽  
Nutrient Loads ◽  
Organic Matter Degradation ◽  
Strong Decrease ◽  
Nitrogen And Phosphorus ◽  
River Elbe

&lt;p&gt;Since the early eighties of the 20&lt;sup&gt;th&lt;/sup&gt; century nitrogen and phosphorus loads of the River Elbe, a river entering the North European Shelf at the southeastern coast, have decreased by a factor of about four. This resulted in a reduction of the eutrophication status in the adjacent German Bight and the coastal waters west of Denmark. In addition, benthic carbon and alkalinity pools have changed due to 1- changed carbon loads and, 2- changed decay pathways of benthic organic carbon.&lt;/p&gt;&lt;p&gt;We investigate the consequences of observed nutrient and organic loads by rivers with a 3D-biogeochemical model including a 3D-early diageneses model within the sediment for the time 1979 - 2014. &amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;The results show a strong decrease of benthic carbon rather due to decreasing nutrient loads and subsequent autochthonous biological production than changes in organic loads. The export of inorganic carbon from the sediment is related to the magnitude of benthic organic carbon and cannot explain the strong decrease of the benthic POC pool.&amp;#160;During the time until the early nineties aerobic degradation increases, whereas denitrification and sulfate reduction as organic matter degradation pathway decreases.&lt;/p&gt;&lt;p&gt;Alkalinity production due to benthic organic matter degradation decreases over the first half of the investigated time interval and keeps constant during the second half. Denitrification and sulfate reduction dominate the mechanisms decreasing the alkalinity export. Benthic nitrification consuming alkalinity strongly increases during the first half of the time dampening the decrease of alkalinity export.&lt;/p&gt;

Mesozooplankton biomass, grazing and trophic structure in the bluefin tuna spawning area of the oceanic Gulf of Mexico

2021 ◽  
Author(s):  
Michael R Landry ◽  
Rasmus Swalethorp
Keyword(s):  
Gulf Of Mexico ◽  
Trophic Structure ◽  
Euphotic Zone ◽  
Bluefin Tuna ◽  
Zooplankton Biomass ◽  
Larval Habitat ◽  
Suspension Feeding ◽  
Atlantic Bluefin Tuna ◽  
Mesozooplankton Biomass ◽  
Coastal Margin

Abstract We investigated size-fractioned biomass, isotopes and grazing of mesozooplankton communities in the larval habitat of Atlantic bluefin tuna (ABT) in the oceanic Gulf of Mexico (GoM) during the peak spawning month of May. Euphotic-zone biomass ranged from 101 to 513 mg C m−2 during the day and 216 to 798 mg C m−2 at night. Grazing varied from 0.1 to 1.0 mg Chla m−2 d−1, averaging 1–3% of phytoplankton Chla consumed d−1. Carnivorous taxa dominated the biomass of &gt; 1-mm zooplankton (78% day; 60% night), while only 13% of smaller zooplankton were carnivores. δ15N enrichment between small and large sizes indicates a 0.5–0.6 trophic-step difference. Although characteristics of GoM zooplankton are generally similar to those of remote oligotrophic subtropical regions, zooplankton stocks in the ABT larval habitat are disproportionately high relative to primary production, compared with HOT and BATS averages. Growth-grazing balances for phytoplankton were resolved with a statistically insignificant residual, and trophic fluxes from local productivity were sufficient to satisfy C demand of suspension feeding mesozooplankton. While carnivore C demand was met by local processes in the central GoM, experiments closer to the coastal margin suggest the need for a lateral subsidy of zooplankton biomass to the oceanic region.

scholarly journals Contribution of Calanus species to the mesozooplankton biomass in the Barents Sea

2017 ◽  
Vol 75 (7) ◽  
pp. 2342-2354 ◽  
Author(s):  
Johanna Myrseth Aarflot ◽  
Hein Rune Skjoldal ◽  
Padmini Dalpadado ◽  
Mette Skern-Mauritzen
Keyword(s):  
Barents Sea ◽  
Zooplankton Community ◽  
Zooplankton Biomass ◽  
Calanus Finmarchicus ◽  
The Arctic ◽  
Arctic Water ◽  
Mesozooplankton Biomass ◽  
The Barents Sea ◽  
Main Driver ◽  
Calanus Species

Abstract Copepods from the genus Calanus are crucial prey for fish, seabirds and mammals in the Nordic and Barents Sea ecosystems. The objective of this study is to determine the contribution of Calanus species to the mesozooplankton biomass in the Barents Sea. We analyse an extensive dataset of Calanus finmarchicus, Calanus glacialis, and Calanus hyperboreus, collected at various research surveys over a 30-year period. Our results show that the Calanus species are a main driver of variation in the mesozooplankton biomass in the Barents Sea, and constitutes around 80% of the total. The proportion of Calanus decreases at low zooplankton biomass, possibly due to a combination of advective processes (low C. finmarchicus in winter) and size selective foraging. Though the Calanus species co-occur in most regions, C. glacialis dominates in the Arctic water masses, while C. finmarchicus dominates in Atlantic waters. The larger C. hyperboreus has considerably lower biomass in the Barents Sea than the other Calanus species. Stages CIV and CV have the largest contribution to Calanus species biomass, whereas stages CI-CIII have an overall low impact on the biomass. In the western area of the Barents Sea, we observe indications of an ongoing borealization of the zooplankton community, with a decreasing proportion of the Arctic C. glacialis over the past 20 years. Atlantic C. finmarchicus have increased during the same period.

Evidence that increased nitrogen efflux from wave-influenced marine sediment enhances pelagic phytoplankton production on the inner continental shelf of Western Australia

2010 ◽  
Vol 61 (5) ◽  
pp. 625 ◽  
Author(s):  
Jim Greenwood
Keyword(s):  
Continental Shelf ◽  
Surface Waves ◽  
Water Column ◽  
Chlorophyll A ◽  
Wave Height ◽  
Western Australia ◽  
Regional Scale ◽  
Reaction Rates ◽  
Phytoplankton Production ◽  
Biogeochemical Model

Increased biological and chemical reaction rates within permeable continental-shelf sediment can result from the action of passing surface waves, especially when the seabed is rippled. The effect of this on the exchange of nitrogen between the sediment and water column is the focus of the present paper. The continental shelf of Western Australia is used as an example. A time series of chlorophyll a is compared with surface-wave height revealing seasonal and sub-seasonal correlation between the two variables. At the same time, results from a coupled pelagic–benthic biogeochemical model show that temperature-controlled changes in sedimentary nitrogen efflux cannot account for the observed seasonal changes in chlorophyll a in the overlying water column. It is proposed that enhanced pore-water circulation within the sediment, caused by the action of passing surface waves, results in an increase in the efflux of nitrogen from the sediment during winter, supporting higher pelagic phytoplankton production. The parameterisation of sedimentary nitrogen mineralisation as a function of the square of wave height is suggested for the inclusion of this effect in regional-scale continental shelf models.

scholarly journals Material properties of Northeast Pacific zooplankton

2014 ◽  
Vol 71 (9) ◽  
pp. 2550-2563 ◽  
Author(s):  
Kaylyn N. Becker ◽  
Joseph D. Warren
Keyword(s):  
Sound Speed ◽  
Larval Fish ◽  
Acoustic Scattering ◽  
Geographic Location ◽  
Geographic Area ◽  
Zooplankton Biomass ◽  
Density Contrast ◽  
Northeast Pacific ◽  
Dimensional Measurements ◽  
The Mean

Abstract We measured the density and sound speed contrasts relative to seawater of Northeast Pacific zooplankton. The density contrast (g) was measured for euphausiids, decapods (Sergestes similis), amphipods (Primno macropa, Phronima sp., and Hyperiid spp.), siphonophore bracts, chaetognaths, larval fish, crab megalopae, larval squid, and medusae. Morphometric data (length, width, and height) were collected for these taxa. Density contrasts varied within and between zooplankton taxa. The mean and standard deviation (s.d.) for euphausiid density contrast were 1.059 ± 0.009. Relationships between zooplankton density contrast and morphometric measurements, geographic location, and environmental conditions were investigated. Site had a significant effect on euphausiid density contrast. Density contrasts of euphausiids collected in the same geographic area ∼4–10 d apart were significantly higher (p< 0.001). Sound speed contrast (h) was measured for euphausiids and pelagic decapods (S. similis) and it varied between taxa. The mean and s.d. for euphausiid sound speed were 1.019 ± 0.009. Euphausiid mass was calculated from measured density and volume, and a relationship between euphausiid mass and length was produced. We determined that euphausiid volume could be accurately estimated from two-dimensional measurements of animal body shape, and that biomass (or biovolume) could be accurately calculated from digital photographs of animals. Data from this study can improve the accuracy of theoretical acoustic scattering models for these taxa, resulting in more accurate estimates of zooplankton biomass in this region.

scholarly journals Environmental Drivers of Benthic Flux Variation and Ecosystem Functioning in Salish Sea and Northeast Pacific Sediments

PLoS ONE ◽  
2016 ◽  
Vol 11 (3) ◽  
pp. e0151110 ◽  
Author(s):  
Rénald Belley ◽  
Paul V. R. Snelgrove ◽  
Philippe Archambault ◽  
S. Kim Juniper
Keyword(s):  
Ecosystem Functioning ◽  
Benthic Flux ◽  
Environmental Drivers ◽  
Salish Sea ◽  
Flux Variation ◽  
Northeast Pacific

Controls on oxygen response to climate change on the Northwest European Continental Shelf

2020 ◽  
Author(s):  
Sarah L. Wakelin ◽  
Yuri Artioli ◽  
Momme Butenschön ◽  
Jason Holt ◽  
Jeremy Blackford
Keyword(s):  
Climate Change ◽  
Continental Shelf ◽  
Water Column ◽  
Ecosystem Processes ◽  
Phytoplankton Production ◽  
Biogeochemical Model ◽  
Biological Cycling ◽  
Increasing Temperature ◽  
The Impact ◽  
Oxygen Concentrations

&lt;p&gt;Dissolved oxygen in the ocean is an indicator of water quality and low concentrations can threaten ecosystem health. The main sources of marine oxygen are diffusion from the atmosphere and phytoplankton photosynthesis. Biological respiration and decomposition act to reduce oxygen concentrations. Under conditions of vertical stratification, the water column below the pycnocline is isolated from oxygen exchange with the atmosphere, photosynthesis may be limited by light availability and oxygen concentrations decrease. Climate change influences the oxygen cycle in two ways: 1) changing the hydrodynamic climate and 2) affecting rates of biogeochemical processes. The hydrodynamic climate affects the nutrient supply and so controls phytoplankton production while changes to water column stratification affects vertical mixing. Gas solubility decreases with increasing temperature so that oxygen uptake from the atmosphere is expected to decrease under increasing oceanic temperatures. Biological cycling rates increase with increasing temperature affecting photosynthesis, respiration and bacterial decomposition. It is not obvious whether changes in oxygen concentrations due to changing ecosystem processes will mitigate or reinforce the projected reduction from solubility changes.&lt;/p&gt;&lt;p&gt;The Northwest European Continental shelf (NWES) is a region of the northeast Atlantic that experiences seasonal stratification. We use the physics-biogeochemical model NEMO-ERSEM to study near-bed oxygen concentrations on the NWES under a high greenhouse gas emissions scenario (Representative Concentration Pathway (RCP) 8.5). We show that much of the NWES could experience low oxygen concentrations by 2100 and assess the relative impacts of changing temperature and ecosystem processes. Until about 2040 the impact of solubility dominates the oxygen change. The mean near-bed oxygen concentration is projected to decrease by 6.3% by 2100, of which 73% is due to solubility changes and the remainder to changes in the ecosystem. In the oxygen-depleted region in the eastern North Sea, 77% of the near-bed oxygen reduction is due to ecosystem processes.&lt;/p&gt;

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