scholarly journals Nitrification in the euphotic zone as a source for nitrite, nitrate, and nitrous oxide at Station ALOHA

1996 ◽  
Vol 41 (8) ◽  
pp. 1619-1628 ◽  
Author(s):  
John E. Dore ◽  
David M. Karl
Keyword(s):  
Nitrous Oxide ◽  
Euphotic Zone ◽  
Station Aloha ◽  
Nitrite Nitrate

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

scholarly journals Vertically migrating phytoplankton drive seasonal formation of subsurface negative preformed nitrate anomalies in the subtropical North Pacific and North Atlantic

2018 ◽  
Author(s):  
Robert T. Letscher ◽  
Tracy A. Villareal
Keyword(s):  
Organic Matter ◽  
Mixed Layer ◽  
North Atlantic ◽  
North Pacific ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Euphotic Zone ◽  
The North ◽  
Station Aloha ◽  
Biological Nitrogen

Abstract. Summertime drawdown of dissolved inorganic carbon in the absence of measurable nutrients from the mixed layer and subsurface negative preformed nitrate (preNO3) anomalies observed for the ocean's subtropical gyres are two biogeochemical phenomena that have thus far eluded complete description. Many processes are thought to contribute including biological nitrogen fixation, lateral nutrient transport, carbon overconsumption or non-Redfield C : N : P organic matter cycling, heterotrophic nutrient uptake, and the actions of vertically migrating phytoplankton. Here we investigate the seasonal formation rates and potential contributing mechanisms for negative preformed nitrate anomalies (oxygen consumption without stoichiometric nitrate release) in the subsurface and positive preformed nitrate anomalies (oxygen production without stoichiometric nitrate drawdown) in the euphotic zone at the subtropical ocean time series stations ALOHA in the North Pacific and BATS in the North Atlantic. Non-Redfield −O2 : N stoichiometry for dissolved organic matter (DOM) remineralization is found to account for up to ~ 15 mmol N m−2 yr−1 of negative preNO3 anomaly formation at both stations. Residual negative preNO3 anomalies in excess of that which can be accounted for by non-Redfield DOM cycling are found to accumulate at a rate of ~ 32–46 mmol N m−2 yr−1 at station ALOHA and ~ 46–87 mmol N m−2 yr−1 at the BATS station. These negative anomaly formation rates are in approximate balance with positive preNO3 anomaly formation rates from the euphotic zone located immediately above the nutricline in the water column. Cycling of transparent exopolymer particles (TEP) and heterotrophic nitrate uptake can contribute to the formation of these preNO3 anomalies, however a significant fraction, estimated at ~ 50–95 %, is unexplained by the sum of these processes. Vertically migrating phytoplankton possess the necessary nutrient acquisition strategy and biogeochemical signature to quantitatively explain both the residual negative and positive preNO3 anomalies as well as the mixed layer dissolved inorganic carbon drawdown at stations ALOHA and BATS. TEP production by the model Rhizosolenia mat system could provide accelerated vertical transport of TEP as well as link the three processes together. Phytoplankton vertical migrators, although rare and easily overlooked, may play a large role in subtropical ocean nutrient cycling and the biological pump.

scholarly journals Microbial respiration in the euphotic zone at Station ALOHA

2015 ◽  
Vol 60 (3) ◽  
pp. 1039-1050 ◽  
Author(s):  
Sandra Martínez‐García ◽  
David M. Karl
Keyword(s):  
Microbial Respiration ◽  
Euphotic Zone ◽  
Station Aloha

scholarly journals Broad phylogenetic and functional diversity among mixotrophic consumers of Prochlorococcus

2021 ◽  
Author(s):  
Qian Li ◽  
Kyle F Edwards ◽  
Christopher R Schvarcz ◽  
Grieg F Steward
Keyword(s):  
Euphotic Zone ◽  
Biogeochemical Cycles ◽  
Body Volume ◽  
North Pacific Subtropical Gyre ◽  
The North ◽  
Quantitative Studies ◽  
Eukaryotic Phytoplankton ◽  
Station Aloha ◽  
Functionally Diverse ◽  
The North Pacific

Small eukaryotic phytoplankton are major contributors to global primary production and marine biogeochemical cycles. Many taxa are thought to be mixotrophic, but quantitative studies of phagotrophy exist for very few. In addition, little is known about consumers of Prochlorococcus, the abundant cyanobacterium at the base of oligotrophic ocean food webs. Here we describe thirty–nine new phytoplankton isolates from the North Pacific Subtropical Gyre (Station ALOHA), all flagellates ~2–5 μm diameter, and we quantify their ability to graze Prochlorococcus. The mixotrophs are from diverse classes (dictyochophytes, haptophytes, chrysophytes, bolidophytes, a dinoflagellate, and a chlorarachniophyte), many from previously uncultured clades. Grazing ability varied substantially, with specific clearance rate (volume cleared per body volume) varying over ten–fold across isolates and six–fold across genera. Slower grazers tend to create more biovolume per prey biovolume consumed. Using qPCR we found that the haptophyte Chrysochromulina was most abundant among the isolated mixotrophs at Station ALOHA, with 76–250 cells mL-1 across depths in the upper euphotic zone. Our results show that within a single ecosystem the phototrophs that ingest bacteria come from many branches of the eukaryotic tree, and are functionally diverse, indicating a broad range of strategies along the spectrum from phototrophy to phagotrophy.

scholarly journals MEASUREMENT OF DISSOLVED INORGANIC NUTRIENT IN EUPHOTIC ZONE THE BANTEN BAY

2010 ◽  
Vol 9 (2) ◽  
pp. 217-225
Author(s):  
Alianto Alianto ◽  
Enan M. Adiwilaga ◽  
Ario Damar ◽  
Enang Harris
Keyword(s):  
Chemical Composition ◽  
Nitrate Solution ◽  
Euphotic Zone ◽  
Inorganic Nutrient ◽  
Low Concentration ◽  
Intensity Measurements ◽  
Yellow Solution ◽  
Nitrite Nitrate

At a few this last years, measurement concentration of dissolved inorganic nutrient is has rapidlyed grow by using various methods. But method anything applied must based on at formation of indicator end of measurement amonia, nitrite, nitrate, orthophosphate and silicate. At measurement of amonia its indicator is formation of blue indophenol, nitrite formation of pink azo, nitrate formation of yellow colored solution, orthophosphate formation of blue molybdenum, and silicate based on formation of yellows silicomolibdate. The intensity of color that is highly dependent on the concentration of each element. Measurement of amonia blue indophenol intensity perfected concentration in the range 0.206-0.396 mg/L. Measurement nitrite the formation of a pink azo easy imperfect because its low concentration. Intensity measurements nitrate solution yellow perfect concentration in the range 0.128-0.989 mg/L. Measurement of imperfect blue molybdenum intensity orthophosphate because its low concentration. While measuring the formation silicate of yellow silicomolibdate  perfect concentration on the range 10.573-26.470 mg/L. As a whole from result of measurement is obtained chemical composition of dissolved inorganic nutrient in euphotic zone the Banten bay is more predominated by silicate 97.27%, nitrate 1.84%, amonia 0.49%, orthophosphate 0.20%, and nitrite 0.18%.   Keywords: blue indophenol, pink azo, yellow solution, blue molybdenum, yellow silicomolibdate

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