Short-term changes of the mesozooplankton community and copepod gut pigment in the Chukchi Sea in autumn

Abstract. In the Chukchi Sea, due to the recent drastic reduction of sea-ice during the summer, an increasing formation of atmospheric turbulence has been reported. However, the importance and effects of atmospheric turbulence on the marine ecosystem are not fully understood in this region. To evaluate the effect of atmospheric turbulence on the marine ecosystem, high-frequent sampling (two to four times per day) on the mesozooplankton community and the gut pigment of dominant copepods were made at a fixed station in the Chukchi Sea from 10 to 25 September 2013. During the study period, a strong wind event (SWE) was observed on 18 September. After the SWE, the standing stock of chlorophyll a (chl a) was increased, especially for micro-size (> 10 μm) fractions. Zooplankton abundance ranged 23 610–56 809 ind. m−2 and exhibited no clear changes with SWE. In terms of abundance, calanoid copepods constituted the most dominated taxa (mean: 57%), followed by barnacle larvae (31%). Within the calanoid copepods, small-sized Pseudocalanus spp. (65%) and large-sized Calanus glacialis (30%) dominated. In the population structure of C. glacialis, copepodid stage 5 (C5) dominated, and the mean copepodid stage did not vary with SWE. The dominance of accumulated lipids in C5 and C6 females with immature gonads indicated that they were preparing for seasonal diapause. The gut pigment of C. glacialis C5 was higher at night and was correlated with ambient chl a, and a significant increase was observed after SWE (2.6 vs. 4.5 ng pigment ind.−1). Assuming C : Chl a ratio, the grazing impact by C. glacialis C5 was estimated to be 4.14 mg C m−2 day−1, which corresponded to 0.5–4.6% of the standing stock of micro-size phytoplankton. Compared with the metabolic food requirement, their feeding on phytoplankton accounted for 12.6% of their total food requirement. These facts suggest that C. glacialis could not maintain their population on solely phytoplankton food, and other food sources (i.e., microzooplankton) are important in autumn. As observed for the increase in gut pigment, temporal phytoplankton bloom, which is enhanced by the atmospheric turbulence (SWE) in autumn, may have a positive effect on copepod nutrition. However, because of the relatively long generation length of copepods, a smaller effect was detected for their abundance, population structure, lipid accumulation and gonad maturation within the short-term period (16 days).

Download Full-text

Short-term changes in the mesozooplankton community and copepod gut pigment in the Chukchi Sea in autumn: reflections of a strong wind event

Biogeosciences ◽

10.5194/bg-12-4005-2015 ◽

2015 ◽

Vol 12 (13) ◽

pp. 4005-4015 ◽

Cited By ~ 8

Author(s):

K. Matsuno ◽

A. Yamaguchi ◽

S. Nishino ◽

J. Inoue ◽

T. Kikuchi

Keyword(s):

Atmospheric Turbulence ◽

Chukchi Sea ◽

Strong Wind ◽

Calanoid Copepods ◽

Mesozooplankton Community ◽

Chl A ◽

Wind Event ◽

Food Requirement ◽

Copepodid Stage ◽

Gut Pigment

Abstract. To evaluate the effect of atmospheric turbulence on a marine ecosystem, high-frequency samplings (two to four times per day) of a mesozooplankton community and the gut pigment of dominant copepods were performed at a fixed station in the Chukchi Sea from 10 to 25 September 2013. During the study period, a strong wind event (SWE) was observed on 18 September. After the SWE, the biomass of chlorophyll a (Chl a) increased, especially for micro-size (> 10 μm) fractions. The zooplankton abundance ranged from 23 610 to 56 809 ind. m−2 and exhibited no clear changes as a result of the SWE. In terms of abundance, calanoid copepods constituted the dominant taxa (mean: 57 %), followed by barnacle larvae (31 %). Within the calanoid copepods, small-sized Pseudocalanus spp. (65 %) and large-sized C. glacialis (30 %) dominated. In the population structure of C. glacialis, copepodid stage 5 (C5) dominated, and the mean copepodid stage did not vary with the SWE. The dominance of accumulated lipids in C5 and C6 females with immature gonads indicated that they were preparing for seasonal diapause. The gut pigment of C. glacialis C5 was higher at night and was correlated with ambient Chl a (Chl a, and a significant increase was observed after the SWE (2.6 vs. 4.5 ng pigment ind.−1). The grazing impact by C. glacialis C5 was estimated to be 4.14 mg C m−2 day−1, which corresponded to 0.5−4.6 % of the biomass of the micro-size phytoplankton. Compared with the metabolic food requirement, C. glacialis feeding on phytoplankton accounted for 12.6 % of their total food requirement. These facts suggest that C. glacialis could not maintain their population by feeding solely on phytoplankton and that other food sources (i.e., microzooplankton) must be important in autumn. As observed by the increase in gut pigment, the temporal phytoplankton bloom, which is enhanced by the atmospheric turbulence (SWE) in autumn, may have a positive effect on copepod nutrition.

Download Full-text

Short-term changes in a microplankton community in the Chukchi Sea during autumn: consequences of a strong wind event

Biogeosciences Discussions ◽

10.5194/bgd-12-8789-2015 ◽

2015 ◽

Vol 12 (11) ◽

pp. 8789-8817 ◽

Cited By ~ 3

Author(s):

N. Yokoi ◽

K. Matsuno ◽

M. Ichinomiya ◽

A. Yamaguchi ◽

S. Nishino ◽

...

Keyword(s):

Atmospheric Turbulence ◽

Chukchi Sea ◽

Marine Ecosystem ◽

Seasonal Succession ◽

Centric Diatom ◽

Strong Wind ◽

Cylindrotheca Closterium ◽

Wind Event ◽

Weak Stratification ◽

High Frequency Sampling

Abstract. An increase in atmospheric turbulence in the Chukchi Sea due to the recent drastic sea-ice reduction during summer months has been reported. The importance of the effects of this atmospheric turbulence on the marine ecosystem in this region, however, is not fully understood. To evaluate the effects of atmospheric turbulence on the marine ecosystem, high-frequency sampling (daily) from five layers of the microplankton community between 0 and 30 m at a fixed station in the Chukchi Sea from 10 through 25 September 2013 was conducted. During the study period, a strong wind event (SWE) was observed on 18 and 19 September. The abundance of microplankton was 2.6 to 17.6 cells mL−1, with a maximum abundance reported at 20 m on 22 September, while diatoms were the most dominant taxa throughout the study period. The abundances of diatoms, dinoflagellates and ciliates ranged between 1.6 and 14.1, 0.5 and 2.4 cells mL−1 and 0.1 and 2.8 cells mL−1, respectively. Diatoms belonging to seven genera consisting of 35 species (Cylindrotheca closterium and Leptocylindrus danicus were dominant), dinoflagellates belonging to seven genera consisting of 25 species (Prorocentrum balticum and Gymnodinium spp. were dominant) and ciliates belonging to seven genera consisting of eight species (Strobilidium spp. and Strombidium spp. were dominant) were identified. Within the microplankton species, there were 11 species whose abundance increased after the SWE, while there was no species whose abundance decreased following the SWE. It is conjectured that atmospheric turbulences, such as that of an SWE, may supply sufficient nutrients to the surface layer that then enhance the small bloom under the weak stratification of the Chukchi Sea shelf during the autumn months. After the bloom, the dominant diatom community then shifts from a centric diatom to a pennate diatom, thus suggesting that an SWE accelerates the seasonal succession of the microplankton community from summer to winter.

Download Full-text

Short-term changes in a microplankton community in the Chukchi Sea during autumn: consequences of a strong wind event

Biogeosciences ◽

10.5194/bg-13-913-2016 ◽

2016 ◽

Vol 13 (4) ◽

pp. 913-923 ◽

Cited By ~ 8

Author(s):

Naoya Yokoi ◽

Kohei Matsuno ◽

Mutsuo Ichinomiya ◽

Atsushi Yamaguchi ◽

Shigeto Nishino ◽

...

Keyword(s):

Atmospheric Turbulence ◽

High Frequency ◽

Chukchi Sea ◽

Marine Ecosystem ◽

Strong Wind ◽

Short Term ◽

Cylindrotheca Closterium ◽

Wind Event ◽

Weak Stratification ◽

High Frequency Sampling

Abstract. Recent studies indicate an increase in atmospheric turbulence in the Chukchi Sea due to the recent drastic sea-ice reduction during summer months. The importance of the effects of this atmospheric turbulence on the marine ecosystem in this region, however, is not fully understood. To evaluate the effects of atmospheric turbulence on the marine ecosystem, high-frequency sampling (daily) from five layers of the microplankton community between 0 and 30 m at a fixed station in the Chukchi Sea from 10 through 25 September 2013 was conducted. During the study period, a strong wind event (SWE) was observed on 18 and 19 September. The abundance of microplankton was 2.6 to 17.6 cells mL−1, with a maximum abundance being reported at 20 m on 22 September, while diatoms were the most dominant taxa throughout the study period. The abundance of diatoms, dinoflagellates and ciliates ranged between 1.6 and 14.1, 0.5 and 2.4 and 0.1 and 2.8 cells mL−1, respectively. Diatoms belonging to 7 genera consisting of 35 species (Cylindrotheca closterium and Leptocylindrus danicus were dominant), dinoflagellates belonging to 7 genera consisting of 25 species (Prorocentrum balticum and Gymnodinium spp. were dominant) and ciliates belonging to 7 genera consisting of 8 species (Strobilidium spp. and Strombidium spp. were dominant) were identified. Within the microplankton species, there were 11 species with abundances that increased after the SWE, while there was no species with an abundance that decreased following the SWE. It is conjectured that atmospheric turbulences, such as that of an SWE, may supply sufficient nutrients to the surface layer that subsequently enhance the small bloom under the weak stratification of the Chukchi Sea Shelf during the autumn months. After the bloom, the dominant diatom community then shifts from centric-dominated to one where centric/pennate are more equal in abundance.

Download Full-text

Microzooplankton grazing and phytoplankton growth in marine mesocosms with increased CO<sub>2</sub> levels

Biogeosciences Discussions ◽

10.5194/bgd-5-411-2008 ◽

2008 ◽

Vol 5 (1) ◽

pp. 411-433 ◽

Cited By ~ 6

Author(s):

K. Suffrian ◽

P. Simonelli ◽

J. C. Nejstgaard ◽

S. Putzeys ◽

Y. Carotenuto ◽

...

Keyword(s):

Growth Rates ◽

Standing Stock ◽

Measured Parameter ◽

Growth Responses ◽

Dilution Technique ◽

Pigment Analysis ◽

Chl A ◽

Co2 Levels ◽

Algae Growth ◽

Microzooplankton Grazing

Abstract. Microzooplankton grazing and algae growth responses to increasing pCO2 levels (350, 700 and 1050 μatm) were investigated in nitrate and phosphate fertilized mesocosms during the PeECE III experiment 2005. Grazing and growth rates were estimated by the dilution technique combined with taxon specific HPLC pigment analysis. Phytoplankton and microzooplankton composition were determined by light microscopy. Despite a range up to 3 times the present CO2 levels, there were no clear differences in any measured parameter between the different CO2 treatments. Thus, during the first 9 days of the experiment the algae community standing stock (SS), measured as chlorophyll a (Chl a), showed the highest instantaneous grow rates (0.02–0.99 d-1) and increased from ca 2–3 to 6–12 μg l−1, in all mesocosms. Afterwards the phytoplankton SS decreased in all mesocosms until the end of the experiment. The microzooplankton SS, that was mainly dinoflagellates and ciliates varied between 23 and 130 μg C l−1, peaking on day 13–15, apparently responding to the phytoplankton development. Instantaneous Chl a growth rates were generally higher than the grazing rates, indicating only a limited overall effect of microzooplankton grazing on the most dominant phytoplankton. Diatoms and prymnesiophytes were significantly grazed (14–43% of the SS d-1) only in the pre-bloom phase when they were in low numbers and in the post-bloom phase when they were already limited by low nutrients and/or virus lysis. The cyanobacteria populations appeared more effected by microzooplankton grazing, generally removing 20–65% of the SS d−1.

Download Full-text

Assessing Bioresources and Standing Stock of Zoobenthos (Key Species, High Taxa, Trophic Groups) in the Chukchi Sea

Oceanography ◽

10.5670/oceanog.2015.63 ◽

2015 ◽

Vol 28 (3) ◽

pp. 146-157 ◽

Cited By ~ 4

Author(s):

Stanislav Denisenko ◽

Jacqueline Grebmeier ◽

Lee Cooper

Keyword(s):

Chukchi Sea ◽

Standing Stock ◽

Trophic Groups ◽

Key Species

Download Full-text

Wave induced turbulence effect on oceanic biogeochemistry and study of ocean color response to changing wave climate

10.5194/egusphere-egu21-9364 ◽

2021 ◽

Author(s):

Chinglen Meetei Tensubam ◽

Alexander V. Babanin

Keyword(s):

Net Primary Productivity ◽

Mixed Layer Depth ◽

Marine Ecosystem ◽

Ocean Color ◽

Ocean Waves ◽

Wave Climate ◽

Upper Ocean ◽

P Value ◽

Chl A ◽

Wave Induced

<p>The role of surface ocean waves becomes substantial in the upper ocean layer mixing. Due to turbulence induced by the surface waves (both broken and unbroken waves), the upper ocean mixing is enhanced, and important upper ocean parameters are affected such as lowering of sea surface temperature (SST), deepening of mixed layer depth (MLD) and most interestingly, the changes in oceanic biogeochemistry. The main objective of this study is to analyze the effect of wave induced turbulence on oceanic biogeochemistry such as the supply and distribution of nutrients to tiny plants in the ocean called phytoplanktons, and how it affects their concentrations. Marine phytoplanktons formed the basis of marine ecosystem which accounts for about 45 percent of global net primary productivity and play an important part in global carbon cycle. The population of phytoplanktons depends mainly on nutrients (both micro and macro), availability of sunlight and grazing organisms. For this study, we use global coupled ocean-sea ice model ACCESS-OM2 with biogeochemical module called WOMBAT to estimate the effect of wave induced turbulence and study the difference between &#8216;with waves&#8217; and &#8216;without waves&#8217; effect on oceanic biogeochemistry. The same effect of wave induced turbulence on oceanic biogeochemistry are also studied by incorporating the change in wave climate such as increase in significant wave height and wind speed. From the investigation of merged satellite ocean color data from ESA&#8217;s GlobColour project for the period of 23 years between 1997 and 2019, it was found that chlorophyll-a (Chl-a, an index of phytoplankton biomass) concentration showed increasing trend of 0.015 mg/m3 globally and 0.062 mg/m3 in the Southern Ocean (SO) for the study period with p-value less than 0.01. It was also found that most of the increasing trends are shown spatially in the open ocean and decreasing trend in the coastal regions during the study period.</p>

Download Full-text

From sea ice to seals: a moored marine ecosystem observatory in the Arctic

Ocean Science ◽

10.5194/os-14-1423-2018 ◽

2018 ◽

Vol 14 (6) ◽

pp. 1423-1433 ◽

Cited By ~ 5

Author(s):

Claudine Hauri ◽

Seth Danielson ◽

Andrew M. P. McDonnell ◽

Russell R. Hopcroft ◽

Peter Winsor ◽

...

Keyword(s):

Sea Ice ◽

Marine Mammals ◽

Chukchi Sea ◽

Marine Ecosystem ◽

Extreme Environment ◽

The Arctic ◽

Zooplankton Abundance ◽

Test Bed ◽

Ecosystem Monitoring ◽

Cold Temperatures

Abstract. Although Arctic marine ecosystems are changing rapidly, year-round monitoring is currently very limited and presents multiple challenges unique to this region. The Chukchi Ecosystem Observatory (CEO) described here uses new sensor technologies to meet needs for continuous, high-resolution, and year-round observations across all levels of the ecosystem in the biologically productive and seasonally ice-covered Chukchi Sea off the northwest coast of Alaska. This mooring array records a broad suite of variables that facilitate observations, yielding better understanding of physical, chemical, and biological couplings, phenologies, and the overall state of this Arctic shelf marine ecosystem. While cold temperatures and 8 months of sea ice cover present challenging conditions for the operation of the CEO, this extreme environment also serves as a rigorous test bed for innovative ecosystem monitoring strategies. Here, we present data from the 2015–2016 CEO deployments that provide new perspectives on the seasonal evolution of sea ice, water column structure, and physical properties, annual cycles in nitrate, dissolved oxygen, phytoplankton blooms, and export, zooplankton abundance and vertical migration, the occurrence of Arctic cod, and vocalizations of marine mammals such as bearded seals. These integrated ecosystem observations are being combined with ship-based observations and modeling to produce a time series that documents biological community responses to changing seasonal sea ice and water temperatures while establishing a scientific basis for ecosystem management.

Download Full-text

From sea ice to seals: A moored marine ecosystem observatory in the Arctic

10.5194/os-2018-82 ◽

2018 ◽

Author(s):

Claudine Hauri ◽

Seth Danielson ◽

Andrew M. P. McDonnell ◽

Russell R. Hopcroft ◽

Peter Winsor ◽

...

Keyword(s):

Sea Ice ◽

Marine Mammals ◽

Chukchi Sea ◽

Marine Ecosystem ◽

Extreme Environment ◽

The Arctic ◽

Zooplankton Abundance ◽

Test Bed ◽

Ecosystem Monitoring ◽

Cold Temperatures

Abstract. Although Arctic marine ecosystems are changing rapidly, year-round monitoring is currently very limited and presents multiple challenges unique to this region. The Chukchi Ecosystem Observatory (CEO) described here uses new sensor technologies to meet needs for continuous, high resolution, and year-round observations across all levels of the ecosystem in the biologically productive and seasonally ice-covered Chukchi Sea off the northwest coast of Alaska. This mooring array records a broad suite of parameters that facilitate observations, yielding better understanding of physical, chemical and biological couplings, phenologies, and the overall state of this Arctic shelf marine ecosystem. While cold temperatures and eight months of sea ice cover present challenging conditions for the operation of the CEO, this extreme environment also serves as a rigorous test bed for innovative ecosystem monitoring strategies. Here, we present data from the 2015–16 CEO deployments that provide new perspectives on the seasonal evolution of sea ice, water column structure and physical properties, annual cycles in nitrate, dissolved oxygen, phytoplankton blooms and export, zooplankton abundance and vertical migration, the occurrence of Arctic cod, and vocalizations of marine mammals such as bearded seals. These integrated ecosystem observations are being combined with ship-based observations and modeling to produce a time-series that documents biological community responses to changing seasonal sea ice and water temperatures while establishing a scientific basis for ecosystem management.

Download Full-text

Delineation of marine ecosystem zones in the northern Arabian Sea during winter

Biogeosciences ◽

10.5194/bg-15-1395-2018 ◽

2018 ◽

Vol 15 (5) ◽

pp. 1395-1414 ◽

Cited By ~ 1

Author(s):

Saleem Shalin ◽

Annette Samuelsen ◽

Anton Korosov ◽

Nandini Menon ◽

Björn C. Backeberg ◽

...

Keyword(s):

Mixed Layer ◽

Temporal Variability ◽

Arabian Sea ◽

Mixed Layer Depth ◽

Marine Ecosystem ◽

Chlorophyll Concentration ◽

Spatial And Temporal Variability ◽

Chl A ◽

Northern Arabian Sea ◽

Cross Correlation Analysis

Abstract. The spatial and temporal variability of marine autotrophic abundance, expressed as chlorophyll concentration, is monitored from space and used to delineate the surface signature of marine ecosystem zones with distinct optical characteristics. An objective zoning method is presented and applied to satellite-derived Chlorophyll a (Chl a) data from the northern Arabian Sea (50–75∘ E and 15–30∘ N) during the winter months (November–March). Principal component analysis (PCA) and cluster analysis (CA) were used to statistically delineate the Chl a into zones with similar surface distribution patterns and temporal variability. The PCA identifies principal components of variability and the CA splits these into zones based on similar characteristics. Based on the temporal variability of the Chl a pattern within the study area, the statistical clustering revealed six distinct ecological zones. The obtained zones are related to the Longhurst provinces to evaluate how these compared to established ecological provinces. The Chl a variability within each zone was then compared with the variability of oceanic and atmospheric properties viz. mixed-layer depth (MLD), wind speed, sea-surface temperature (SST), photosynthetically active radiation (PAR), nitrate and dust optical thickness (DOT) as an indication of atmospheric input of iron to the ocean. The analysis showed that in all zones, peak values of Chl a coincided with low SST and deep MLD. The rate of decrease in SST and the deepening of MLD are observed to trigger the algae bloom events in the first four zones. Lagged cross-correlation analysis shows that peak Chl a follows peak MLD and SST minima. The MLD time lag is shorter than the SST lag by 8 days, indicating that the cool surface conditions might have enhanced mixing, leading to increased primary production in the study area. An analysis of monthly climatological nitrate values showed increased concentrations associated with the deepening of the mixed layer. The input of iron seems to be important in both the open-ocean and coastal areas of the northern and north-western parts of the northern Arabian Sea, where the seasonal variability of the Chl a pattern closely follows the variability of iron deposition.

Download Full-text

Phytoplankton biomass, composition, and productivity along a temperature and stratification gradient in the Northeast Atlantic Ocean

Biogeosciences Discussions ◽

10.5194/bgd-10-1793-2013 ◽

2013 ◽

Vol 10 (1) ◽

pp. 1793-1829 ◽

Cited By ~ 1

Author(s):

W. H. van de Poll ◽

G. Kulk ◽

K. R. Timmermans ◽

C. P. D. Brussaard ◽

H. J. van der Woerd ◽

...

Keyword(s):

Atlantic Ocean ◽

Phytoplankton Biomass ◽

Nutrient Concentration ◽

North Atlantic Ocean ◽

Standing Stock ◽

Biomass Composition ◽

Nutrient Concentrations ◽

Exponential Relationship ◽

Near Surface ◽

Chl A

Abstract. The North Atlantic Ocean experiences considerable variability in sea surface temperature (SST, >10 m) on seasonal and inter-annual time-scales. Relationships between SST and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and absorption were assessed in spring and summer from latitudes 30–62° N. Furthermore, a bio-optical model was used to estimate productivity for five phytoplankton groups. Nutrient concentration (integrated from 0–125 m) was inversely correlated with SST in spring and summer. SST was also inversely correlated with near surface (0–50 m) Chl a and productivity for stratified stations. However, near surface Chl a showed an exponential relationship with SST, whereas a linear relationship was found for productivity and SST. The response of phytoplankton to changes in SST is therefore most likely to be observed by changes in Chl a rather than productivity. The discrepancy between relationships of Chl a and productivity were probably related to changes in phytoplankton cell size. The contribution of cyanobacteria to water column productivity correlated positively with SST and inversely with nutrient concentration. This suggests that a rise in SST (over a 13–23 °C range) stimulates productivity by cyanobacteria at the expense of haptophytes, which showed an inverse relationship to SST. At higher latitudes, where rising SST may prolong the stratified season, haptophyte productivity may expand at the expense of diatom productivity. Depth integrated Chl a (0–410 m) was greatest in the spring at higher latitudes, where stratification in the upper 200 m was weakest. This suggests that stronger stratification does not necessarily result in higher phytoplankton biomass standing stock in this region.

Download Full-text