scholarly journals Sources of nutrients driving production in the Gulf of Carpentaria, Australia: a shallow tropical shelf system

2009 ◽  
Vol 60 (10) ◽  
pp. 1044 ◽  
Author(s):  
Michele A. Burford ◽  
Peter C. Rothlisberg ◽  
Andrew T. Revill
Keyword(s):  
Primary Productivity ◽  
Euphotic Zone ◽  
N Fixation ◽  
Boundary Current ◽  
N Budget ◽  
Pristine Area ◽  
Summer Bloom ◽  
Abundant Genus ◽  
Marine Areas ◽  
Coastal Boundary

The tropical Gulf of Carpentaria, Australia, has recently been identified as one of the world’s least impacted marine areas, presenting a unique opportunity to understand the nutrient drivers of productivity. The present study examined the nitrogen (N) sources and transformations in this pristine area and the role of N in fuelling primary productivity, principally based on summer data. The N budget estimates on a whole-of-Gulf basis suggest that river N inputs are unlikely to be major contributors to primary productivity. In the deeper waters of the Gulf, beyond the coastal boundary current, the main source of N is estimated to be N fixation by cyanobacteria, principally the abundant genus Trichodesmium. The present study measured high N fixation rates and depleted δ15N–N ratios in the particulate matter in the water column during a summer bloom. During summer, bottom N concentrations increased and δ15N–N ratios were depleted, suggesting that benthic mineralisation is occurring. It is therefore likely that detrital material from N-rich Trichodesmium is an important contributor to benthic processes. During winter, wind-driven mixing results in N from the bottom waters reaching the euphotic zone, and fuelling primary productivity. Therefore, Trichodesmium has an important direct and indirect role in contributing to primary productivity in this pristine tropical ecosystem.

scholarly journals Nitrogen cycling in Sandusky Bay, Lake Erie: oscillations between strong and weak export and implications for harmful algal blooms

2018 ◽  
Vol 15 (9) ◽  
pp. 2891-2907 ◽  
Author(s):  
Kateri R. Salk ◽  
George S. Bullerjahn ◽  
Robert Michael L. McKay ◽  
Justin D. Chaffin ◽  
Nathaniel E. Ostrom
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Lake Erie ◽  
N Uptake ◽  
N Fixation ◽  
N Budget ◽  
N2o Production ◽  
N Removal ◽  
Uptake Rates ◽  
N Loading

Abstract. Recent global water quality crises point to an urgent need for greater understanding of cyanobacterial harmful algal blooms (cHABs) and their drivers. Nearshore areas of Lake Erie such as Sandusky Bay may become seasonally limited by nitrogen (N) and are characterized by distinct cHAB compositions (i.e., Planktothrix over Microcystis). This study investigated phytoplankton N uptake pathways, determined drivers of N depletion, and characterized the N budget in Sandusky Bay. Nitrate (NO3-) and ammonium (NH4+) uptake, N fixation, and N removal processes were quantified by stable isotopic approaches. Dissimilatory N reduction was a relatively modest N sink, with denitrification, anammox, and N2O production accounting for 84, 14, and 2 % of sediment N removal, respectively. Phytoplankton assimilation was the dominant N uptake mechanism, and NO3- uptake rates were higher than NH4+ uptake rates. Riverine N loading was sometimes insufficient to meet assimilatory and dissimilatory demands, but N fixation alleviated this deficit. N fixation made up 23.7–85.4 % of total phytoplankton N acquisition and indirectly supports Planktothrix blooms. However, N fixation rates were surprisingly uncorrelated with NO3- or NH4+ concentrations. Owing to temporal separation in sources and sinks of N to Lake Erie, Sandusky Bay oscillates between a conduit and a filter of downstream N loading to Lake Erie, delivering extensively recycled forms of N during periods of low export. Drowned river mouths such as Sandusky Bay are mediators of downstream N loading, but climate-change-induced increases in precipitation and N loading will likely intensify N export from these systems.

scholarly journals Short‐term variability in euphotic zone biogeochemistry and primary productivity at Station ALOHA: A case study of summer 2012

2015 ◽  
Vol 29 (8) ◽  
pp. 1145-1164 ◽  
Author(s):  
Samuel T. Wilson ◽  
Benedetto Barone ◽  
Francois Ascani ◽  
Robert R. Bidigare ◽  
Matthew J. Church ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Euphotic Zone ◽  
Short Term ◽  
Station Aloha ◽  
Short Term Variability

Nitrogen cycling in microbial mat communities: The quantitative importance of N-fixation and other sources of N for primary productivity

1994 ◽  
pp. 265-271 ◽  
Author(s):  
Brad M. Bebout ◽  
Hans W. Paerl ◽  
James E. Bauer ◽  
Donald E. Canfield ◽  
David J. Des Marais
Keyword(s):  
Nitrogen Cycling ◽  
Primary Productivity ◽  
Microbial Mat ◽  
N Fixation ◽  
Quantitative Importance

Sinking particle fluxes from the euphotic zone over the continental slope of an eastern boundary current region

1996 ◽  
Vol 54 (6) ◽  
pp. 1097-1122 ◽  
Author(s):  
M. A. Pena ◽  
K. L. Denman ◽  
J. R. Forbes ◽  
S. E. Calvert ◽  
R. E. Thomson
Keyword(s):  
Continental Slope ◽  
Euphotic Zone ◽  
Boundary Current ◽  
Eastern Boundary ◽  
Eastern Boundary Current ◽  
Current Region ◽  
Particle Fluxes

scholarly journals ESTIMASI PRODUKTIVITAS PRIMER PERAIRAN BERDASARKAN KONSENTRASI KLOROFIL-A YANG DIEKSTRAK DARI CITRA SATELIT LANDSAT-8 DI PERAIRAN KEPULAUAN KARIMUN JAWA

2017 ◽  
Vol 14 (1) ◽  
Author(s):  
Mulkan Nuzapril ◽  
Setyo Budi Susilo ◽  
James Parlindungan Panjaitan
Keyword(s):  
Chlorophyll A ◽  
Attenuation Coefficient ◽  
Primary Productivity ◽  
Chlorophyll Concentration ◽  
Euphotic Zone ◽  
Landsat 8 ◽  
Secchi Disk ◽  
Estimation Model ◽  
Chlorophyll A Concentration ◽  
Average Value

Sea primary productivity is an important factor in monitoring the quality of sea waters due to his role in the carbon cycle and the food chain for heterotrophic organisms. Estimation of sea primary productivity may be suspected through the values of chlorophyll-a concentration, but surface chlorophyll-a concentration was only able to explain 30% of the primary productivity of the sea. This research aims to build primary productivity estimation model based on chlorophyll-a concentration value of a surface layer of depth until depth compensation. Primary productivity model of relationships with chlorophyll concentration were extracted from Landsat-8 imagery then it could be used to calculated of sea primary productivity. The determination of the depth classification were done by measuring the attenuation coefficient values using the luxmeter underwater datalogger 2000 and secchi disk. The attenuation coefficient values by the luxmeter underwater, ranges between of 0.13-0.21 m-1 and secchi disk ranged, of 0.12 – 0.21 m-1. The penetration of light that through into the water column where  primary productivity is still in progress or where the depth of compensation ranged from 28.75 – 30.67 m. The simple linier regression model between average value of chlorophyll- concentration in all euphotic zone with sea primary productivity has high correlation, it greater than of surface chlorophyll-a concentration (R2 = 0.65). Model validation of sea primary productivity has high accuracy with the RMSD value of 0.09 and satellite-derived sea primary productivity were not significantly different. The satellite derived of chlorophyll-a could be calculated into sea primary productivity.Abstrak Produktivitas primer perairan merupakan faktor penting dalam pemantauan kualitas perairan laut karena berperan dalam siklus karbon dan rantai makanan bagi organisme heterotrof. Estimasi produktivitas primer perairan dapat diduga melalui nilai konsentrasi klorofil-a, namun konsentrasi klorofil-a permukaan laut hanya mampu menjelaskan 30% produktivitas primer laut. Penelitian ini bertujuan untuk membangun model estimasi produktivitas primer berdasarkan nilai konsentrasi klorofil-a dari lapisan kedalaman permukaan sampai kedalaman kompensasi. Model hubungan produktivitas primer dengan konsentrasi klorofil-a yang diekstrak dari citra satelit Landsat-8 kemudian dapat digunakan untuk mengestimasi produktivitas primer satelit. Penentuan klasifikasi kedalaman dilakukan dengan mengukur nilai koefisien atenuasi menggunakan luxmeter underwater datalogger 2000  dan secchi disk. Nilai koefisien atenuasi dengan menggunakan luxmeter underwater berkisar antara 0,13 -0,21m-1 dan secchi disk berkisar antara 0,12 – 0,21 m-1. Penetrasi cahaya yang masuk ke kolom perairan dimana produksi primer masih berlangsung atau kedalaman kompensasi berkisar antara 28,75 – 30,67 m. Model regresi linier sederhana antara konsentrasi klorofil-a rata-rata seluruh zona eufotik dengan produktivitas primer perairan memiliki korelasi yang lebih tinggi dibandingkan konsentrasi klorofil-a permukaan dengan R2= 0,65. Validasi model produktivitas primer memiliki keakuratan yang tinggi dengan RMSD sebesar 0,09 dan produktivitas primer satelit secara signifikan tidak berbeda nyata dengan produktivitas primer data insitu. Sehingga  nilai konsentrasi klorofil-a satelit dapat ditransformasi menjadi produktivitas primer satelit.

scholarly journals Revisiting Biological Nitrogen Fixation Dynamics in Soybeans

2021 ◽  
Vol 12 ◽  
Author(s):  
Ignacio A. Ciampitti ◽  
André Froes de Borja Reis ◽  
S. Carolina Córdova ◽  
Michael J. Castellano ◽  
Sotirios V. Archontoulis ◽  
...  
Keyword(s):  
Maximum Rate ◽  
Seasonal Pattern ◽  
Single Point ◽  
Clay Content ◽  
Growth Stages ◽  
N Fixation ◽  
N Budget ◽  
Fixation Rate ◽  
N Removal ◽  
Biological Nitrogen

Biological nitrogen (N) fixation is the most relevant process in soybeans (Glycine max L.) to satisfy plant N demand and sustain seed protein formation. Past studies describing N fixation for field-grown soybeans mainly focused on a single point time measurement (mainly toward the end of the season) and on the partial N budget (fixed-N minus seed N removal), overlooking the seasonal pattern of this process. Therefore, this study synthesized field datasets involving multiple temporal measurements during the crop growing season to characterize N fixation dynamics using both fixed-N (kg ha−1) and N derived from the atmosphere [Ndfa (%)] to define: (i) time to the maximum rate of N fixation (β2), (ii) time to the maximum Ndfa (α2), and (iii) the cumulative fixed-N. The main outcomes of this study are that (1) the maximum rate of N fixation was around the beginning of pod formation (R3 stage), (2) time to the maximum Ndfa (%) was after full pod formation (R4), and (3) cumulative fixation was positively associated with the seasonal vapor-pressure deficit (VPD) and growth cycle length but negatively associated with soil clay content, and (4) time to the maximum N fixation rate (β2) was positively impacted by season length and negatively impacted by high temperatures during vegetative growth (but positively for VPD, during the same period). Overall, variation in the timing of the maximum rate of N fixation occurred within a much narrower range of growth stages (R3) than the timing of the maximum Ndfa (%), which varied broadly from flowering (R1) to seed filing (R5–R6) depending on the evaluated studies. From a phenotyping standpoint, N fixation determinations after the R4 growth stage would most likely permit capturing both maximum fixed-N rate and maximum Ndfa (%). Further investigations that more closely screen the interplay between N fixation with soil-plant-environment factors should be pursued.

scholarly journals Primary productivity measurements in the Ross Sea, Antarctica: A regional synthesis

2021 ◽  
Author(s):  
Walker O. Smith Jr.
Keyword(s):  
Primary Productivity ◽  
Ross Sea ◽  
Chlorophyll Concentration ◽  
Euphotic Zone ◽  
Data Set ◽  
Phaeocystis Antarctica ◽  
Ecological Importance ◽  
Global Biogeochemical Cycles ◽  
Critical Components ◽  
Productivity Measurements

Abstract. Polar systems are undersampled due to the difficulty of sampling remote and challenging environments; however, these systems are critical components of global biogeochemical cycles. Measurements on primary productivity in specific areas can quantify the input of organic matter to food webs, and so are of critical ecological importance as well. However, long-term measurements using the same methodology are available only for a few polar systems. Primary productivity measurements using 14C-uptake incubations from the Ross Sea, Antarctica, are synthesized, along with chlorophyll concentrations at the same depths and locations. A total of 19 independent cruises were completed, and 449 stations occupied where measurements of primary productivity (each with 7 depths) were completed. The incubations used the same basic simulated in situ methodology for all. Integrated water column productivity for all stations averaged 1.10 ± 1.20 g C m−2 d−1, and the maximum was 13.1 g C m−2 d−1. Annual productivity calculated from the means throughout the growing season equalled 146 g C m−2 yr−1. Mean chlorophyll concentration in the euphotic zone (the 1 % irradiance level) was 2.85 ± 2.68 mg m−3 (maximum concentration was 19.1 mg m−3). Maximum photosynthetic rates at the surface (normalized to chlorophyll) averaged 0.94 ± 0.71 mg C (mg chl)−1 h−1, similar to the maximum rate found in photosynthesis/irradiance measurements. Productivity measurements are consistent with the temporal patterns of biomass found previously, with biomass and productivity peaking in late December; mixed layers were at a minimum at this time as well. Estimates of plankton composition also suggest that pre-January productivity was largely driven by the haptophyte Phaeocystis antarctica, and summer productivity by diatoms. The data set will be useful for a comparison to other Antarctic regions and provide a basis for refined bio-optical models of regional primary productivity.

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