Temporal dynamics of phytoplankton and heterotrophic protists at station ALOHA

Pasulka, Alexis L.; Landry, Michael R.; Taniguchi, Darcy A. A.; Taylor, Andrew G.; Church, Matthew J.

doi:10.1016/j.dsr2.2013.01.007

Cited by 50 publications

(50 citation statements)

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“…Alternately, if the export ratio is more consistent with measured ratios (e = 0.02-0.15), then either large diazotroph production would need to be an order of magnitude greater than what we have estimated or other N 2 -fixing organisms are directly or indirectly contributing to the summer export pulse. While not observed in our study period, there is precedent in the literature for an order of magnitude increase in the concentration of large diazotrophs as discussed earlier (Venrick, 1974;Church et al, 2009;Pasulka et al, 2013;Shiozaki et al, 2017) and presumably their contribution to production and export. And so, while DDA cell abundances were relatively low over our study period and the disparity between cell-and gene-based abundance needs to be reconciled, there are historical records of abundances that are more consistent with summer DDA-driven export than ours.…”

Section: Discussionmentioning

confidence: 49%

“…In contrast to our findings here, other studies have observed significant contributions of large diazotrophs to bulk organic matter. Specifically, Pasulka et al (2013) microscopically estimated Trichodesmium spp. biovolume at Station ALOHA (2004)(2005)(2006)(2007)(2008)(2009) in small volume samples (0.5 L filtered and a minimum of 10 ml volume imaged) and concluded that Trichodesmium in the upper 50 m could account for 20-50% of total carbon in late summer to early fall.…”

Section: Month-yearmentioning

confidence: 99%

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Temporal Variability of Trichodesmium spp. and Diatom-Diazotroph Assemblages in the North Pacific Subtropical Gyre

2018

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In oligotrophic ocean regions such as the North Pacific Subtropical Gyre (NPSG), N 2 fixation (i.e., diazotrophy) by a diverse consortium of microorganisms has been shown to contribute significantly to new production and particle export. In 2015 and 2016, we measured near-monthly abundances of the large cell-sized (> 10 µm) diazotrophic genera Trichodesmium and diatom-associated Richelia and Calothrix spp. in the NPSG via microscopy and quantitative PCR of nifH genes. Of these genera, we find Trichodesmium to be the more abundant over our study period, with cell concentrations in the upper water column (0-45 m) ranging from 1 to 5,988 cells L −1 , while the sum of Richelia and Calothrix spp. abundances ranged from 4 to 157 heterocysts L −1 . Significant discrepancies between absolute abundances were noted between cell and gene-based approaches to biomass determination (nifH copies L −1 were up to 10 2 -10 3 higher than cell concentrations). Potential explanations for these striking discrepancies are discussed. Using the maximum N fixation rates per cell found in the existing literature for these genera, we estimate potential N 2 fixation rates via these large diazotroph communities to be between 0.01 and 1.5 nmol N L −1 d −1 . When comparing these rates to available 15 N 2 tracer measurements, we conclude that large diazotrophs were generally minor (<10%) contributors to bulk N 2 fixation in the surface ocean during our study period. Conversely, high concentrations of Trichodesmium observed in fall-winter of 2015 and 2016 were estimated to drive >50% of measured N 2 fixation rates. While these large cell-sized and heterogeneously distributed organisms may still disproportionately contribute to export, cell-abundance based rate estimates suggests that other diazotrophs are largely responsible for N 2 fixation rates measured in bottle-based incubations.

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Section: Discussionmentioning

confidence: 49%

Section: Month-yearmentioning

confidence: 99%

Temporal Variability of Trichodesmium spp. and Diatom-Diazotroph Assemblages in the North Pacific Subtropical Gyre

2018

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“…Additionally, Yuras et al (2005) have reported a winter increase in chlorophyll concentration in the offshore surface waters in the southern Pacific off the coast of Chile. Our current study, as well as a recent similar analysis of phytoplankton samples collected by the Hawaii Ocean Time-series Program at Station ALOHA (Pasulka et al, 2013), document that the winter chlorophyll maximum is more than a pigment response, but an actual seasonal, though modest, increase in carbon biomass of the plankton community.…”

Section: Seasonal Phytoplankton Trendsmentioning

confidence: 86%

“…Nonetheless, taxonomic analysis of larger cells by Venrick (1992Venrick ( , 2002Venrick ( , 2009) has shown that species composition in offshore CCE waters is very similar to that of the North Pacific subtropical gyre (NPSG). Additionally, using the same methods as the current study, Pasulka et al (2013) found similar phytoplankton community composition at station ALOHA in the NPSG, which would reasonably constitute the oligotrophic end-member of CCE variability.…”

Section: Community Compositionmentioning

confidence: 89%

Temporal and spatial patterns of microbial community biomass and composition in the Southern California Current Ecosystem

Taylor

Landry

Selph

et al. 2015

Deep Sea Research Part II: Topical Studies in Oceanography

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a b s t r a c tAs part of the California Current Ecosystem Long Term Ecological Research (CCE-LTER) Program, samples for epifluorescence microscopy and flow cytometry (FCM) were collected at ten 'cardinal' stations on the California Cooperative Oceanic Fisheries Investigations (CalCOFI) grid during 25 quarterly cruises from 2004 to 2010 to investigate the biomass, composition and size-structure of microbial communities within the southern CCE. Based on our results, we divided the region into offshore, and inshore northern and southern zones. Mixed-layer phytoplankton communities in the offshore had lower biomass (16 7 2 μg C L � 1 ; all errors represent the 95% confidence interval), smaller size-class cells and biomass was more stable over seasonal cycles. Offshore phytoplankton biomass peaked during the winter months. Mixed-layer phytoplankton communities in the northern and southern inshore zones had higher biomass (78722 and 32 79 μg C L � 1 , respectively), larger size-class cells and stronger seasonal biomass patterns. Inshore communities were often dominated by micro-size (20-200 μm) diatoms; however, autotrophic dinoflagellates dominated during late 2005 to early 2006, corresponding to a year of delayed upwelling in the northern CCE. Biomass trends in mid and deep euphotic zone samples were similar to those seen in the mixed-layer, but with declining biomass with depth, especially for larger size classes in the inshore regions. Mixed-layer ratios of autotrophic carbon to chlorophyll a (AC:Chl a) had a mean value of 51.57 5.3. Variability of nitracline depth, bin-averaged AC:Chl a in the mixed-layer ranged from 40 to 80 and from 22 to 35 for the deep euphotic zone, both with significant positive relationships to nitracline depth. Total living microbial carbon, including auto-and heterotrophs, consistently comprised about half of particulate organic carbon (POC).

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“…Marine picoplankton (<2–3 μm) constitute a microbial community significant in structure and function within pelagic food webs of oligotrophic ecosystems, including the subtropical regions of the Atlantic (DuRand et al, ; Zubkov et al, , ), the Pacific (Campbell et al, ; Pasulka et al, ) and Indian Basins (Garrison et al, ), and some semi‐enclosed basins like the Mediterranean Sea (Vaulot et al, ) or the deep region of the Gulf of Mexico (GoM; Linacre et al, ). Picoplankton communities are composed of autotrophic and heterotrophic microorganisms and play a crucial role in global biogeochemical cycles (Azam & Malfatti, ).…”

Section: Introductionmentioning

confidence: 99%

Picoplankton Carbon Biomass Assessments and Distribution of Prochlorococcus Ecotypes Linked to Loop Current Eddies During Summer in the Southern Gulf of Mexico

et al. 2019

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Assessments of picoplankton carbon biomass in the pelagic ecosystem over the deep region of the southern Gulf of Mexico were conducted during three consecutive summer cruises. Notably, the relationship between carbon distribution of Prochlorococcus (PRO) and Loop Current (LC) dynamics was evaluated. Seawater samples were collected from the euphotic zone (~150 m) for estimating the abundance of the picoplankton populations using flow cytometry analyses. Carbon biomass estimates were based on cell abundance and variable conversion factors computed across stations and depths. On average, about half of the total depth-integrated carbon biomass of picoplankton was attributed to heterotrophic bacteria (HB, 54%) and three autotrophic populations (Prochlorococcus, Synechococcus, and pico-eukaryotes, 46%). In agreement with previous winter assessments, PRO was the dominant component of abundance (~90%) and pico-phytoplankton community biomass (>70%). Based on molecular analyses, distinct ecotypes of high-light PRO and low-light (LL) PRO were found within the euphotic zone, vertically distributed along light and nutrient gradients. Also, PRO distributions were related to hydrographic conditions strongly modulated by mesoscale dynamics. LL-PRO subgroups, located close to the nutricline under LL conditions, were associated with the westward propagation of anticyclonic eddies that episodically detach from the LC. This study highlights the role of the LC and its eddies in the transport and distribution of carbon biomass into the Gulf of Mexico, as represented by the deep subgroups of the dominant, tiniest autotroph within this oligotrophic ecosystem.

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Temporal dynamics of phytoplankton and heterotrophic protists at station ALOHA

Cited by 50 publications

References 51 publications

Temporal Variability of Trichodesmium spp. and Diatom-Diazotroph Assemblages in the North Pacific Subtropical Gyre

Temporal Variability of Trichodesmium spp. and Diatom-Diazotroph Assemblages in the North Pacific Subtropical Gyre

Temporal and spatial patterns of microbial community biomass and composition in the Southern California Current Ecosystem

Picoplankton Carbon Biomass Assessments and Distribution of Prochlorococcus Ecotypes Linked to Loop Current Eddies During Summer in the Southern Gulf of Mexico

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