http://lod.bco-dmo.org/id/dataset/995456 eng; USA utf8 dataset Highest level of data collection, from a common set of sensors or instrumentation, usually within the same research project Biological and Chemical Oceanography Data Management Office (BCO-DMO) Unavailable 508-289-2009 WHOI MS#36 Woods Hole MA 02543 USA info@bco-dmo.org http://www.bco-dmo.org Monday - Friday 8:00am - 5:00pm For questions regarding this resource, please contact BCO-DMO via the email address provided. pointOfContact 2026-03-24 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) Bulk percentage of 14C, ATP, prokaryote and protist abundances from mesopelagic decay experiments with Thalassiosira weissflogii, Emiliania huxleyi, and Tetraselmis sp. 2026-03-24 publication 2026-03-24 revision BCO-DMO Linked Data URI 2026-03-24 creation http://lod.bco-dmo.org/id/dataset/995456 Alexander Boris Bochdansky Old Dominion University principalInvestigator Biological and Chemical Oceanography Data Management Office (BCO-DMO) Unavailable 508-289-2009 WHOI MS#36 Woods Hole MA 02543 USA info@bco-dmo.org http://www.bco-dmo.org Monday - Friday 8:00am - 5:00pm For questions regarding this resource, please contact BCO-DMO via the email address provided. publisher Cite this dataset as: Bochdansky, A. B. (2026) Bulk percentage of 14C, ATP, prokaryote and protist abundances from mesopelagic decay experiments with Thalassiosira weissflogii, Emiliania huxleyi, and Tetraselmis sp. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2026-03-24 [if applicable, indicate subset used]. http://lod.bco-dmo.org/id/dataset/995456 [access date] Mesopelagic decay experiments: bulk 14C, ATP, and prokaryote and protist abundances Dataset Description: &lt;p&gt;This dataset is part of a group of related datasets from the same mesopleagic decay experiments. See the &quot;Related Datasets&quot; section on this page for access to other related datasets in this group.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Datasets from these experiments:&lt;/strong&gt;&lt;br /&gt; - Bulk percentage of 14C, ATP, and prokaryote and protist abundances&lt;br /&gt; - Biochemical percentages (protein, polysaccharides, and lipids)&lt;br /&gt; - Biochemical decay rates&lt;/p&gt; Methods and Sampling: &lt;p&gt;&lt;strong&gt;Experimental overview and design of treatments&lt;/strong&gt;:&lt;br /&gt; In the first experiment, live cells of the diatom &lt;em&gt;Thalassiosira weissflogii&lt;/em&gt; were added to the mesopelagic community; in the second, live cells and nonliving organic matter (both POC and DOC) from &lt;em&gt;T. weissflogii&lt;/em&gt; were added; and in the third, nonliving organic matter from three species was used. In each experiment, at least one treatment was set up the same way to allow direct comparisons from experiment to experiment, as mesopelagic water was collected at different times of the year and might include different microbial communities. To simulate decay, we used model material (live cells, POC, and DOC) in a state where they could be easily mixed to obtain representative subsamples and at low concentrations so that the addition of organic material would not lead to the depletion of oxygen. Carbon-14-labeled algal cultures (&lt;em&gt;E. huxleyi &lt;/em&gt;CCMP374, &lt;em&gt;T. weissflogii&lt;/em&gt; CCMP374 or &lt;em&gt;Tetraselmis&lt;/em&gt; sp. UTEX SP22) in the early stationary phases were first gently filtered onto 0.8 micrometer (μm) polycarbonate filters (Isopore) to remove remaining inorganic &lt;sup&gt;14&lt;/sup&gt;C and then resuspended in 0.2-μm-filtered artificial seawater. The preparation of the POC and DOC fractions was similar to the methods described by Cabrera-Brufau et al. (2021). The resuspended cells were frozen at -80 degrees Celsius (°C) for at least one hour to kill the cells and break them up to release DOC. Before the experiments, a sample of this culture was thawed and vacuum-filtered through a 0.2 μm filter, an operational cutoff for the separation of POC and DOC. The PO&lt;sup&gt;14&lt;/sup&gt;C fraction on the filter was resuspended in filtered artificial seawater of the same volume, while the filtrate became the DO&lt;sup&gt;14&lt;/sup&gt;C fraction. For the live treatments, &lt;em&gt;T. weissflogii&lt;/em&gt; cultures were gently filtered (using 0.8 μm filters and low vacuum, &amp;lt; 10 millibars (mbar)), washed and resuspended in unlabeled seawater, and added to the experimental flasks immediately without further processing.&lt;/p&gt; &lt;p&gt;The mesopelagic water was collected at three different times from the same site at a depth of 300 meters (m), 115 kilometers (km) offshore of Virginia Beach (36.788° N, 74.629° W) using four 5-liter (L) Niskin bottles. The water temperature at the collection depth was consistently 12 ± 0.5 °C, regardless of the season. The water was gently transferred (i.e., with minimum turbulence and air bubbles) from the Niskin bottles through a hose into two 20-L plastic bladder tanks, which were immediately placed into a temperature-controlled cooler at either 8 °C (experiment 1) or 12 °C (experiments 2 and 3). Upon arrival at the lab and on the same day of collection, the water was moved to a dark temperature-controlled room in which the experiments were performed and set to either 8 °C (experiment 1) or 12 °C (experiments 2 and 3). The algal treatments were added the day after the water collection. All experimental treatments were conducted in triplicates. Thirteen milliliters (ml) of either the live algal suspension, PO&lt;sup&gt;14&lt;/sup&gt;C, or DO&lt;sup&gt;14&lt;/sup&gt;C were added to 1.7 L of mesopelagic water in each 4-L aspirator flask. Unlabeled cultures of &lt;em&gt;T. weissflogii&lt;/em&gt; grown under the same conditions were filtered onto muffled GF/F filters and analyzed for particulate carbon with a Europa 20-20 isotope ratio mass spectrometer to determine the total carbon content of the cultures at the time of harvest. Since all cultures were grown under the same conditions over many division cycles, these cells can be considered uniformly labeled. Consequently, the relative amount of added carbon can be calculated from the apportionment of disintegrations per minute (dpm) values. Samples were collected through a tube and a plastic ball valve connected to the aspirator flask to measure PO&lt;sup&gt;14&lt;/sup&gt;C, DO&lt;sup&gt;14&lt;/sup&gt;C, ATP, prokaryote abundance, and biochemical fractions. We also monitored the mesopelagic microbial community over three weeks without the addition of substrates, in a separate collection taken from the same site and depth, to confirm that both ATP and cell abundances changed relatively little during this time period.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Sample Collection:&lt;/strong&gt;&lt;br /&gt; Before sampling at each time point, the water in the flasks was swirled until well mixed through without excessive shaking. Preliminary experiments with similar additions of unlabeled substrates, in which we measured oxygen concentrations using a polarographic oxygen sensor, revealed that the oxygen concentrations remained near saturation (data not shown). The geometry of the flasks was such that a large surface area of the water was exposed to air, and the agitation before sampling additionally mixed oxygen into the incubation water. Aggregates that could have created microzones of low oxygen were also not observed during the experiments. From each flask, 10–30 ml of water was purged from the valves, and then 30–40 ml of samples were collected into 50-ml Falcon centrifuge tubes. The protocol and rationale for sampling the carbon pools followed Bochdansky et al. (2010). From the collected water, four 5-ml samples were immediately vacuum-filtered onto GF/F filters. The first three filters were placed into plastic pony vials for PO&lt;sup&gt;14&lt;/sup&gt;C analysis. The fourth filter (for ATP) was placed into a cryovial that contained 1 ml of phosphoric acid-benzalkonium chloride extractant (P-BAC), left at room temperature for 20–30 minutes for extraction, and subsequently kept in a -80 °C freezer until analysis (Bochdansky et al. 2021). Three 0.5-ml allotments of the filtrate were placed into separate pony vials for analysis of the DO&lt;sup&gt;14&lt;/sup&gt;C fractions. The vials containing the POC and DOC fractions were acidified overnight with 0.25 ml of 0.2 N perchloric acid to eliminate inorganic carbon (Bochdansky et al. 2010). Four ml of scintillation cocktail (Bio-Safe II, Research Products International) was added to the vials the next day, which were then capped, inverted to ensure homogeneity, and analyzed on a liquid scintillation counter (LSC) (Perkin Elmer Tri-Carb model 3110) using a 20-minute count setting per vial to ensure sufficient time for accurate readings at low activity. Three blanks with only scintillation cocktail were run at every other time point; their values were averaged and subtracted from the sample values. The remainder of the liquid samples kept in the Falcon tubes were fixed for cell counts. Buffered 0.2-µm-filtered 37% formaldehyde was added to each sample at a final concentration of 0.2% and left overnight. The next day, subsamples of 5 ml were filtered onto black polycarbonate membranes (Isopore GTBP) and stored in a -80 °C freezer until analysis under the epifluorescence microscope. Depending on the experiment, one or two filters were prepared for each flask at each time point.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;ATP Analysis:&lt;/strong&gt;&lt;br /&gt; The analysis of ATP samples followed the procedure of Bochdansky et al. (2021), which was modified from Holm-Hansen and Booth (1966). From each cryovial, 10 microliters (µl) of sample was placed into triplicate scintillation vials along with 3 ml of ~18.2 MΩ ultrapure water (Barnstaed) and 50 µl of CellTiter-Glo 2.0 (Promega, protocol modified as in Bochdansky et al. 2021). A standard solution made with 50 µl of an ATP standard of 16.4 nanomolar (nM) concentration was added along with the sample, water, and CellTiter-Glo to a fourth vial. The standards were interspersed with the samples during counting on the LSC to track the slow (i.e., over many hours) decay in luminescence over time, which allowed for a precise calculation of the ATP values.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Cell Counts:&lt;/strong&gt;&lt;br /&gt; The polycarbonate filter membranes were embedded in a mounting medium that contained 4',6-diamidino-2-phenylindole dihydrochloride (Fluoroshield with DAPI, F6057, Sigma-Aldrich) to detect double-stranded DNA using an Olympus BX51 epifluorescence microscope with a 100x immersion oil objective, 2x loupe, and 10x ocular lenses to obtain a 2000x total magnification (Hobbie et al. 1977; Porter and Feig 1980). Protist grazers were identified by their conspicuous round or oval nuclei that were larger than prokaryote cells.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Carbon decay models and statistics:&lt;/strong&gt;&lt;br /&gt; Visually, the trajectory of carbon decay over time appeared to consist of at least two phases. Therefore, piecewise regressions were used with the natural-log-transformed percentages of remaining PO&lt;sup&gt;14&lt;/sup&gt;C and DO&lt;sup&gt;14&lt;/sup&gt;C over time. We calculated exponential decay rate constants for each phase as the slopes of the linear regressions with the natural-log-transformed data. Analysis of Covariance (ANCOVA) homogeneity of slope tests were used on natural-log-transformed values to assess significance between treatments, variables, and biochemical fractions.&lt;/p&gt; &lt;p&gt;To capture a more highly resolved change in decay rates through the course of the experiments, we calculated first-order kinetics for each pair of time points (equation 1):&lt;/p&gt; &lt;p&gt;D = ln(dpm&lt;sub&gt;t1&lt;/sub&gt;/dpm&lt;sub&gt;t2&lt;/sub&gt;) (t&lt;sub&gt;2&lt;/sub&gt;-t&lt;sub&gt;1&lt;/sub&gt;)-1, (equation 1)&lt;/p&gt; &lt;p&gt;where D is the instantaneous rate of decay (d-1), dpm&lt;sub&gt;t1&lt;/sub&gt; and dpm&lt;sub&gt;t2&lt;/sub&gt; are the initial and final values, respectively, of &lt;sup&gt;14&lt;/sup&gt;C in the POC or DOC fractions, and t&lt;sub&gt;1&lt;/sub&gt; and t&lt;sub&gt;2&lt;/sub&gt; are the time points of the paired samples (d).&lt;br /&gt; &lt;br /&gt; &lt;strong&gt;Organism Identifiers:&lt;/strong&gt;&lt;br /&gt; Scientific Name (Life Science Identifier [LSID])&lt;br /&gt; &lt;br /&gt; &lt;em&gt;Thalassiosira weissflogii&lt;/em&gt; (urn:lsid:marinespecies.org:taxname:&lt;a href=&quot;https://marinespecies.org/aphia.php?p=taxdetails&amp;amp;id=163513&quot; target=&quot;_blank&quot;&gt;163513&lt;/a&gt;)&lt;br /&gt; &lt;em&gt;Tetraselmis sp.&lt;/em&gt; (urn:lsid:marinespecies.org:taxname:&lt;a href=&quot;https://marinespecies.org/aphia.php?p=taxdetails&amp;amp;id=134526&quot; target=&quot;_blank&quot;&gt;134526&lt;/a&gt;)&lt;br /&gt; &lt;em&gt;Emiliania huxleyi&lt;/em&gt; (urn:lsid:marinespecies.org:taxname:&lt;a href=&quot;https://marinespecies.org/aphia.php?p=taxdetails&amp;amp;id=115104&quot; target=&quot;_blank&quot;&gt;115104&lt;/a&gt;)&lt;/p&gt; Funding provided by NSF Division of Ocean Sciences (NSF OCE) Award Number: OCE-1851368 Award URL: https://www.nsf.gov/awardsearch/show-award?AWD_ID=1851368 onGoing Alexander Boris Bochdansky Old Dominion University 757-683-4933 Ocean, Earth and Atmospheric Sciences 4600 Elkhorn Ave. Norfolk VA 23529 USA abochdan@odu.edu pointOfContact asNeeded Dataset Version: 1 Unknown Experiment Algal_substrate Carbon_pool Elapsed_days Pcnt_14C_flask1 Pcnt_14C_flask2 Pcnt_14C_flask3 Decay_1 Decay_2 Decay_3 ATP_flask1 ATP_flask2 ATP_flask3 Prok_flask1_filter1 Prok_flask2_filter1 Prok_flask3_filter1 Prok_flask1_filter2 Prok_flask2_filter2 Prok_flask3_filter2 Prot_flask1 Prot_flask2 Prot_flask3 Olympus BX51 epifluorescence microscope Europa 20-20 isotope ratio mass spectrometer Perkin Elmer Tri-Carb model 3110 theme None, User defined experiment id species scientific name (binomial) treatment time_elapsed 14C rate_measurements Adenosinetriphosphate cell_concentration featureType BCO-DMO Standard Parameters Fluorescence Microscope PDZ Europa 20-20 isotope ratio mass spectrometer PerkinElmer Tri-Carb 3110TR low activity liquid scintillation analyzer instrument BCO-DMO Standard Instruments otherRestrictions otherRestrictions Access Constraints: none. Use Constraints: Please follow guidelines at: http://www.bco-dmo.org/terms-use Distribution liability: Under no circumstances shall BCO-DMO be liable for any direct, incidental, special, consequential, indirect, or punitive damages that result from the use of, or the inability to use, the materials in this data submission. If you are dissatisfied with any materials in this data submission your sole and exclusive remedy is to discontinue use. Collaborative Research: Transforming Carbon in the Deep Sea https://osprey.bco-dmo.org/project/817462 Collaborative Research: Transforming Carbon in the Deep Sea <p><em>NSF Award Abstract:</em><br /> Through understanding the biological pump (the ocean's biologically driven sequestration of carbon from the atmosphere to the ocean interior and seafloor sediments), scientists know that the world's oceans absorb more carbon dioxide than it returns to the atmosphere. While much is known about the biological processes largely responsible for the transfer of carbon into the deep sea, very little is known about the microbial decay and subsequent remineralization processes that occur when the carbon reaches the deep sea. Using newly-designed deep-sea incubators deployed off the east coast of the United States, researchers will explore the microbial communities and remineralization processes that transform carbon in the deep sea. The incubators will be filled with tracer-labeled algae or fecal material mimicking the diet and waste products of animal plankton. The tracers allow the researchers to follow the material through the microbial food web, and simultaneously determine the net release of carbon dioxide during the incubations. Using a combination of genetic analysis and novel analytical techniques, the researchers will be able to identify the organisms involved in the decay processes and rates at which changes occur at the single-cell level. Results will shed light on these understudied biological phenomena and contribute to an improved understanding of the global carbon cycle. In addition to novel advancements in oceanographic technology, the research supports graduate and undergraduate student education, and public outreach through partnerships with the Virginia Aquarium and National Ocean Sciences Bowl to increase ocean science literacy.</p> <p>In this project, researchers will study the organisms, mechanisms, and physical and ecological factors that modulate the remineralization of organic material in the deep sea. The methods include using in situ incubations of well-defined and stable isotope-labeled sources of organic carbon (live and dead phytoplankton and fecal pellets of zooplankton) with natural microbial communities. The incubations will take place northeast of Cape Hatteras, a region characterized by strong offshore transport of phytoplankton carbon. Net carbon dioxide release rates will be measured over time by conversion of Carbon-13 labeled organic carbon to 13CO2 . The dependence of degradation rates on the source material, seasonality, oxygen concentration, and the type of microbial colonizers will be assessed. Parallel laboratory experiments will elucidate the exact shape of the time course of carbon release by phytoplankton into dissolved organic and inorganic fractions as well as determine how representative laboratory and ship-board generated values are relative to those obtained in situ. Target eukaryotic and prokaryotic taxa are identified by fluorescence in-situ hybridization (FISH) after the incubations and individually interrogated using Raman microspectrometry to investigate the relative Carbon-13-enrichment rates in organisms assimilating labeled detrital carbon. This multi-faceted approach will provide better constrained parameters for ecosystem and biological pump models and shed light on carbon balances of the deep sea. The research contributes to the development of new oceanographic technology, including new deep-sea incubators and application of single-cell Raman microspectrometry to natural microbial communities.</p> Carbon in the Deep Sea largerWorkCitation project eng; USA oceans -74.629 -74.629 36.788 36.788 2020-10-06 2021-05-27 Mesopelagic North Atlantic 0 BCO-DMO catalogue of parameters from Bulk percentage of 14C, ATP, prokaryote and protist abundances from mesopelagic decay experiments with Thalassiosira weissflogii, Emiliania huxleyi, and Tetraselmis sp. Biological and Chemical Oceanography Data Management Office (BCO-DMO) Unavailable 508-289-2009 WHOI MS#36 Woods Hole MA 02543 USA info@bco-dmo.org http://www.bco-dmo.org Monday - Friday 8:00am - 5:00pm For questions regarding this resource, please contact BCO-DMO via the email address provided. pointOfContact http://lod.bco-dmo.org/id/dataset-parameter/995496.rdf Name: Experiment Units: unitless Description: <p>Experiment number 1-3</p> http://lod.bco-dmo.org/id/dataset-parameter/995497.rdf Name: Algal_substrate Units: unitless Description: <p>One of three algal sources of carbon: Tw = Thalassiosira weissflogii, Eh = Emiliania huxleyi, Ts = Tetraselmis sp.</p> http://lod.bco-dmo.org/id/dataset-parameter/995498.rdf Name: Carbon_pool Units: unitless Description: <p>One of three carbon pools: Live = live algae, POC = particulate organic carbon, DOC = dissolved organic carbon</p> http://lod.bco-dmo.org/id/dataset-parameter/995499.rdf Name: Elapsed_days Units: days Description: <p>Number of days elapsed</p> http://lod.bco-dmo.org/id/dataset-parameter/995500.rdf Name: Pcnt_14C_flask1 Units: percent (%) Description: <p>Percentage of labeled 14C remaining in the first replicate flask</p> http://lod.bco-dmo.org/id/dataset-parameter/995501.rdf Name: Pcnt_14C_flask2 Units: percent (%) Description: <p>Percentage of labeled 14C remaining in the second replicate flask</p> http://lod.bco-dmo.org/id/dataset-parameter/995502.rdf Name: Pcnt_14C_flask3 Units: percent (%) Description: <p>Percentage of labeled 14C remaining in the third replicate flask</p> http://lod.bco-dmo.org/id/dataset-parameter/995503.rdf Name: Decay_1 Units: per day (d-1) Description: <p>Instantaneous rate of decay in the first replicate</p> http://lod.bco-dmo.org/id/dataset-parameter/995504.rdf Name: Decay_2 Units: per day (d-1) Description: <p>Instantaneous rate of decay in the second replicate</p> http://lod.bco-dmo.org/id/dataset-parameter/995505.rdf Name: Decay_3 Units: per day (d-1) Description: <p>Instantaneous rate of decay in the third replicate</p> http://lod.bco-dmo.org/id/dataset-parameter/995506.rdf Name: ATP_flask1 Units: nM (nanomolar) Description: <p>Adenosine triphosphate concentration in replicate flask 1</p> http://lod.bco-dmo.org/id/dataset-parameter/995507.rdf Name: ATP_flask2 Units: nM (nanomolar) Description: <p>Adenosine triphosphate concentration in replicate flask 2</p> http://lod.bco-dmo.org/id/dataset-parameter/995508.rdf Name: ATP_flask3 Units: nM (nanomolar) Description: <p>Adenosine triphosphate concentration in replicate flask 3</p> http://lod.bco-dmo.org/id/dataset-parameter/995509.rdf Name: Prok_flask1_filter1 Units: cells per milliliter (cells ml-1) Description: <p>Microscopic counts of prokaryotes in replicate flask 1 filter #1</p> http://lod.bco-dmo.org/id/dataset-parameter/995510.rdf Name: Prok_flask2_filter1 Units: cells per milliliter (cells ml-1) Description: <p>Microscopic counts of prokaryotes in replicate flask 2 filter #1</p> http://lod.bco-dmo.org/id/dataset-parameter/995511.rdf Name: Prok_flask3_filter1 Units: cells per milliliter (cells ml-1) Description: <p>Microscopic counts of prokaryotes in replicate flask 3 filter #1</p> http://lod.bco-dmo.org/id/dataset-parameter/995512.rdf Name: Prok_flask1_filter2 Units: cells per milliliter (cells ml-1) Description: <p>Microscopic counts of prokaryotes in replicate flask 1 filter #2</p> http://lod.bco-dmo.org/id/dataset-parameter/995513.rdf Name: Prok_flask2_filter2 Units: cells per milliliter (cells ml-1) Description: <p>Microscopic counts of prokaryotes in replicate flask 2 filter #2</p> http://lod.bco-dmo.org/id/dataset-parameter/995514.rdf Name: Prok_flask3_filter2 Units: cells per milliliter (cells ml-1) Description: <p>Microscopic counts of prokaryotes in replicate flask 3 filter #2</p> http://lod.bco-dmo.org/id/dataset-parameter/995515.rdf Name: Prot_flask1 Units: cells per milliliter (cells ml-1) Description: <p>Microscopic counts of protists in replicate flask 1</p> http://lod.bco-dmo.org/id/dataset-parameter/995516.rdf Name: Prot_flask2 Units: cells per milliliter (cells ml-1) Description: <p>Microscopic counts of protists in replicate flask 2</p> http://lod.bco-dmo.org/id/dataset-parameter/995517.rdf Name: Prot_flask3 Units: cells per milliliter (cells ml-1) Description: <p>Microscopic counts of protists in replicate flask 3</p> GB/NERC/BODC > British Oceanographic Data Centre, Natural Environment Research Council, United Kingdom Biological and Chemical Oceanography Data Management Office (BCO-DMO) Unavailable 508-289-2009 WHOI MS#36 Woods Hole MA 02543 USA info@bco-dmo.org http://www.bco-dmo.org Monday - Friday 8:00am - 5:00pm For questions regarding this resource, please contact BCO-DMO via the email address provided. pointOfContact https://osprey.bco-dmo.org/dataset/995456/data/download download onLine dataset &lt;p&gt;&lt;strong&gt;Experimental overview and design of treatments&lt;/strong&gt;:&lt;br /&gt; In the first experiment, live cells of the diatom &lt;em&gt;Thalassiosira weissflogii&lt;/em&gt; were added to the mesopelagic community; in the second, live cells and nonliving organic matter (both POC and DOC) from &lt;em&gt;T. weissflogii&lt;/em&gt; were added; and in the third, nonliving organic matter from three species was used. In each experiment, at least one treatment was set up the same way to allow direct comparisons from experiment to experiment, as mesopelagic water was collected at different times of the year and might include different microbial communities. To simulate decay, we used model material (live cells, POC, and DOC) in a state where they could be easily mixed to obtain representative subsamples and at low concentrations so that the addition of organic material would not lead to the depletion of oxygen. Carbon-14-labeled algal cultures (&lt;em&gt;E. huxleyi &lt;/em&gt;CCMP374, &lt;em&gt;T. weissflogii&lt;/em&gt; CCMP374 or &lt;em&gt;Tetraselmis&lt;/em&gt; sp. UTEX SP22) in the early stationary phases were first gently filtered onto 0.8 micrometer (μm) polycarbonate filters (Isopore) to remove remaining inorganic &lt;sup&gt;14&lt;/sup&gt;C and then resuspended in 0.2-μm-filtered artificial seawater. The preparation of the POC and DOC fractions was similar to the methods described by Cabrera-Brufau et al. (2021). The resuspended cells were frozen at -80 degrees Celsius (°C) for at least one hour to kill the cells and break them up to release DOC. Before the experiments, a sample of this culture was thawed and vacuum-filtered through a 0.2 μm filter, an operational cutoff for the separation of POC and DOC. The PO&lt;sup&gt;14&lt;/sup&gt;C fraction on the filter was resuspended in filtered artificial seawater of the same volume, while the filtrate became the DO&lt;sup&gt;14&lt;/sup&gt;C fraction. For the live treatments, &lt;em&gt;T. weissflogii&lt;/em&gt; cultures were gently filtered (using 0.8 μm filters and low vacuum, &amp;lt; 10 millibars (mbar)), washed and resuspended in unlabeled seawater, and added to the experimental flasks immediately without further processing.&lt;/p&gt; &lt;p&gt;The mesopelagic water was collected at three different times from the same site at a depth of 300 meters (m), 115 kilometers (km) offshore of Virginia Beach (36.788° N, 74.629° W) using four 5-liter (L) Niskin bottles. The water temperature at the collection depth was consistently 12 ± 0.5 °C, regardless of the season. The water was gently transferred (i.e., with minimum turbulence and air bubbles) from the Niskin bottles through a hose into two 20-L plastic bladder tanks, which were immediately placed into a temperature-controlled cooler at either 8 °C (experiment 1) or 12 °C (experiments 2 and 3). Upon arrival at the lab and on the same day of collection, the water was moved to a dark temperature-controlled room in which the experiments were performed and set to either 8 °C (experiment 1) or 12 °C (experiments 2 and 3). The algal treatments were added the day after the water collection. All experimental treatments were conducted in triplicates. Thirteen milliliters (ml) of either the live algal suspension, PO&lt;sup&gt;14&lt;/sup&gt;C, or DO&lt;sup&gt;14&lt;/sup&gt;C were added to 1.7 L of mesopelagic water in each 4-L aspirator flask. Unlabeled cultures of &lt;em&gt;T. weissflogii&lt;/em&gt; grown under the same conditions were filtered onto muffled GF/F filters and analyzed for particulate carbon with a Europa 20-20 isotope ratio mass spectrometer to determine the total carbon content of the cultures at the time of harvest. Since all cultures were grown under the same conditions over many division cycles, these cells can be considered uniformly labeled. Consequently, the relative amount of added carbon can be calculated from the apportionment of disintegrations per minute (dpm) values. Samples were collected through a tube and a plastic ball valve connected to the aspirator flask to measure PO&lt;sup&gt;14&lt;/sup&gt;C, DO&lt;sup&gt;14&lt;/sup&gt;C, ATP, prokaryote abundance, and biochemical fractions. We also monitored the mesopelagic microbial community over three weeks without the addition of substrates, in a separate collection taken from the same site and depth, to confirm that both ATP and cell abundances changed relatively little during this time period.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Sample Collection:&lt;/strong&gt;&lt;br /&gt; Before sampling at each time point, the water in the flasks was swirled until well mixed through without excessive shaking. Preliminary experiments with similar additions of unlabeled substrates, in which we measured oxygen concentrations using a polarographic oxygen sensor, revealed that the oxygen concentrations remained near saturation (data not shown). The geometry of the flasks was such that a large surface area of the water was exposed to air, and the agitation before sampling additionally mixed oxygen into the incubation water. Aggregates that could have created microzones of low oxygen were also not observed during the experiments. From each flask, 10–30 ml of water was purged from the valves, and then 30–40 ml of samples were collected into 50-ml Falcon centrifuge tubes. The protocol and rationale for sampling the carbon pools followed Bochdansky et al. (2010). From the collected water, four 5-ml samples were immediately vacuum-filtered onto GF/F filters. The first three filters were placed into plastic pony vials for PO&lt;sup&gt;14&lt;/sup&gt;C analysis. The fourth filter (for ATP) was placed into a cryovial that contained 1 ml of phosphoric acid-benzalkonium chloride extractant (P-BAC), left at room temperature for 20–30 minutes for extraction, and subsequently kept in a -80 °C freezer until analysis (Bochdansky et al. 2021). Three 0.5-ml allotments of the filtrate were placed into separate pony vials for analysis of the DO&lt;sup&gt;14&lt;/sup&gt;C fractions. The vials containing the POC and DOC fractions were acidified overnight with 0.25 ml of 0.2 N perchloric acid to eliminate inorganic carbon (Bochdansky et al. 2010). Four ml of scintillation cocktail (Bio-Safe II, Research Products International) was added to the vials the next day, which were then capped, inverted to ensure homogeneity, and analyzed on a liquid scintillation counter (LSC) (Perkin Elmer Tri-Carb model 3110) using a 20-minute count setting per vial to ensure sufficient time for accurate readings at low activity. Three blanks with only scintillation cocktail were run at every other time point; their values were averaged and subtracted from the sample values. The remainder of the liquid samples kept in the Falcon tubes were fixed for cell counts. Buffered 0.2-µm-filtered 37% formaldehyde was added to each sample at a final concentration of 0.2% and left overnight. The next day, subsamples of 5 ml were filtered onto black polycarbonate membranes (Isopore GTBP) and stored in a -80 °C freezer until analysis under the epifluorescence microscope. Depending on the experiment, one or two filters were prepared for each flask at each time point.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;ATP Analysis:&lt;/strong&gt;&lt;br /&gt; The analysis of ATP samples followed the procedure of Bochdansky et al. (2021), which was modified from Holm-Hansen and Booth (1966). From each cryovial, 10 microliters (µl) of sample was placed into triplicate scintillation vials along with 3 ml of ~18.2 MΩ ultrapure water (Barnstaed) and 50 µl of CellTiter-Glo 2.0 (Promega, protocol modified as in Bochdansky et al. 2021). A standard solution made with 50 µl of an ATP standard of 16.4 nanomolar (nM) concentration was added along with the sample, water, and CellTiter-Glo to a fourth vial. The standards were interspersed with the samples during counting on the LSC to track the slow (i.e., over many hours) decay in luminescence over time, which allowed for a precise calculation of the ATP values.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Cell Counts:&lt;/strong&gt;&lt;br /&gt; The polycarbonate filter membranes were embedded in a mounting medium that contained 4',6-diamidino-2-phenylindole dihydrochloride (Fluoroshield with DAPI, F6057, Sigma-Aldrich) to detect double-stranded DNA using an Olympus BX51 epifluorescence microscope with a 100x immersion oil objective, 2x loupe, and 10x ocular lenses to obtain a 2000x total magnification (Hobbie et al. 1977; Porter and Feig 1980). Protist grazers were identified by their conspicuous round or oval nuclei that were larger than prokaryote cells.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Carbon decay models and statistics:&lt;/strong&gt;&lt;br /&gt; Visually, the trajectory of carbon decay over time appeared to consist of at least two phases. Therefore, piecewise regressions were used with the natural-log-transformed percentages of remaining PO&lt;sup&gt;14&lt;/sup&gt;C and DO&lt;sup&gt;14&lt;/sup&gt;C over time. We calculated exponential decay rate constants for each phase as the slopes of the linear regressions with the natural-log-transformed data. Analysis of Covariance (ANCOVA) homogeneity of slope tests were used on natural-log-transformed values to assess significance between treatments, variables, and biochemical fractions.&lt;/p&gt; &lt;p&gt;To capture a more highly resolved change in decay rates through the course of the experiments, we calculated first-order kinetics for each pair of time points (equation 1):&lt;/p&gt; &lt;p&gt;D = ln(dpm&lt;sub&gt;t1&lt;/sub&gt;/dpm&lt;sub&gt;t2&lt;/sub&gt;) (t&lt;sub&gt;2&lt;/sub&gt;-t&lt;sub&gt;1&lt;/sub&gt;)-1, (equation 1)&lt;/p&gt; &lt;p&gt;where D is the instantaneous rate of decay (d-1), dpm&lt;sub&gt;t1&lt;/sub&gt; and dpm&lt;sub&gt;t2&lt;/sub&gt; are the initial and final values, respectively, of &lt;sup&gt;14&lt;/sup&gt;C in the POC or DOC fractions, and t&lt;sub&gt;1&lt;/sub&gt; and t&lt;sub&gt;2&lt;/sub&gt; are the time points of the paired samples (d).&lt;br /&gt; &lt;br /&gt; &lt;strong&gt;Organism Identifiers:&lt;/strong&gt;&lt;br /&gt; Scientific Name (Life Science Identifier [LSID])&lt;br /&gt; &lt;br /&gt; &lt;em&gt;Thalassiosira weissflogii&lt;/em&gt; (urn:lsid:marinespecies.org:taxname:&lt;a href=&quot;https://marinespecies.org/aphia.php?p=taxdetails&amp;amp;id=163513&quot; target=&quot;_blank&quot;&gt;163513&lt;/a&gt;)&lt;br /&gt; &lt;em&gt;Tetraselmis sp.&lt;/em&gt; (urn:lsid:marinespecies.org:taxname:&lt;a href=&quot;https://marinespecies.org/aphia.php?p=taxdetails&amp;amp;id=134526&quot; target=&quot;_blank&quot;&gt;134526&lt;/a&gt;)&lt;br /&gt; &lt;em&gt;Emiliania huxleyi&lt;/em&gt; (urn:lsid:marinespecies.org:taxname:&lt;a href=&quot;https://marinespecies.org/aphia.php?p=taxdetails&amp;amp;id=115104&quot; target=&quot;_blank&quot;&gt;115104&lt;/a&gt;)&lt;/p&gt; Specified by the Principal Investigator(s) &lt;p&gt;Analysis of the data (reported Craft &amp;amp; Bochdansky, 2025) was performed using the Statistics and Machine Learning Toolbox in MATLAB (The MathWorks, Inc.) for the piecewise regressions and the Analysis of Covariance (ANCOVA) homogeneity of slopes tests, and a custom randomization program was also written in MATLAB to obtain p-values without the requirement of normality and homoscedasticity in the distributions of the residuals. Both sets of results are reported.&lt;/p&gt; Specified by the Principal Investigator(s) - Imported original file &quot;Mesopelagic Experiment Data 1Apr2025.csv&quot; into the BCO-DMO processing system. - Treated &quot;NaN&quot; as a missing data value (missing data are empty/blank in the final CSV file). - Renamed fields to comply with BCO-DMO naming conventions. - Saved the final file as &quot;995456_v1_bulk14c_atp_abundances.csv&quot;. Specified by BCO-DMO Data Managers asNeeded 7.x-1.1 Biological and Chemical Oceanography Data Management Office (BCO-DMO) Unavailable 508-289-2009 WHOI MS#36 Woods Hole MA 02543 USA info@bco-dmo.org http://www.bco-dmo.org Monday - Friday 8:00am - 5:00pm For questions regarding this resource, please contact BCO-DMO via the email address provided. pointOfContact Olympus BX51 epifluorescence microscope Olympus BX51 epifluorescence microscope PI Supplied Instrument Name: Olympus BX51 epifluorescence microscope PI Supplied Instrument Description:Used for cell counts with DAPI staining at 2000x magnification to enumerate prokaryotes and protist grazers on polycarbonate filters Instrument Name: Fluorescence Microscope Instrument Short Name: Instrument Description: Instruments that generate enlarged images of samples using the phenomena of fluorescence and phosphorescence instead of, or in addition to, reflection and absorption of visible light. Includes conventional and inverted instruments. Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/LAB06/ Europa 20-20 isotope ratio mass spectrometer Europa 20-20 isotope ratio mass spectrometer PI Supplied Instrument Name: Europa 20-20 isotope ratio mass spectrometer PI Supplied Instrument Description:Used for the analysis of bulk carbon Instrument Name: PDZ Europa 20-20 isotope ratio mass spectrometer Instrument Short Name:Europa 20-20 IRMS Instrument Description: The PDZ Europa 20-20 is a dedicated continuous flow isotope ratio mass spectrometer for hyphenated stable isotope analyses able to measure 15N, 13C, 18O, and 34S in a host of applications. The analyzer has been purposely designed to measure 2H by continuous flow methodology and is also suitable to analyze the light stable isotopes in all the commonly measured gases: H2, N2, NO, N2O, O2, CO, CO2, SO, and SO2. Perkin Elmer Tri-Carb model 3110 Perkin Elmer Tri-Carb model 3110 PI Supplied Instrument Name: Perkin Elmer Tri-Carb model 3110 PI Supplied Instrument Description:Used for the analysis of 14C Instrument Name: PerkinElmer Tri-Carb 3110TR low activity liquid scintillation analyzer Instrument Short Name:Tri-Carb 3110TR Instrument Description: The PerkinElmer Tri-Carb 3110TR is a benchtop liquid scintillation analyzer for detecting small amounts of alpha, beta, and gamma radioactivity. It features a Multichannel Analyzer with an effective resolution of 1/10 keV and an extended dynamic quench range. Sample capacity is either 408 standard 20 mL vials, or 720 small 4 or 7 mL vials. The instrument includes a barium-133 low-energy external standard source centered under the sample vial which eliminates the effects of volume variations. It has an energy range of 0-2000 keV and an operating ambient temperature range of 15-35 degrees Celsius.