Rickard Stenow, Malin Olofsson, Martin J. Whitehouse, Helle Ploug
{"title":"Chain forming diatoms use different strategies to avoid diffusion limited N assimilation","authors":"Rickard Stenow, Malin Olofsson, Martin J. Whitehouse, Helle Ploug","doi":"10.1002/lno.12677","DOIUrl":null,"url":null,"abstract":"<p>Formation of large colonies by phytoplankton is considered a disadvantage during low nutrient and non-turbulent conditions because of diffusion limitation and competition by neighboring cells. This is assumed by diffusion models and not empirical measurements. Here, we measured cell-specific dissolved inorganic carbon (DIC) and nitrate (<span></span><math>\n <mrow>\n <msubsup>\n <mi>NO</mi>\n <mn>3</mn>\n <mo>−</mo>\n </msubsup>\n </mrow></math>) assimilation in two chain-forming <i>Skeletonema marinoi</i> strains by combining secondary ion mass spectrometry with stable isotopic tracer incubations. The pelagic strains were recently germinated from resting stages and thus not adapted to high nutrient regimes of laboratory cultures. During the exponential phase, the cells assimilated excess <span></span><math>\n <mrow>\n <msubsup>\n <mi>NO</mi>\n <mn>3</mn>\n <mo>−</mo>\n </msubsup>\n </mrow></math> relative to DIC. The DIC and <span></span><math>\n <mrow>\n <msubsup>\n <mi>NO</mi>\n <mn>3</mn>\n <mo>−</mo>\n </msubsup>\n </mrow></math> assimilation varied with chain length or the position of the cell within chains but did not follow any consistent trend. Solitary cells were rare and did not exceed 6% of all cells. During the nitrogen-limited stationary phase, <span></span><math>\n <mrow>\n <msubsup>\n <mi>NO</mi>\n <mn>3</mn>\n <mo>−</mo>\n </msubsup>\n </mrow></math> assimilation was lower than modeled by mass transfer theory at diffusion limitation. <span></span><math>\n <mrow>\n <msubsup>\n <mi>NO</mi>\n <mn>3</mn>\n <mo>−</mo>\n </msubsup>\n </mrow></math> assimilation rates were apparently limited by the biological uptake rate at nitrate concentrations < 0.46 <i>μ</i>mol L<sup>−1</sup>. We conclude that <i>S. marinoi</i> is adapted to high nutrient concentrations and may seldom be diffusion limited in coastal waters with ambient <span></span><math>\n <mrow>\n <msubsup>\n <mi>NO</mi>\n <mn>3</mn>\n <mo>−</mo>\n </msubsup>\n </mrow></math> concentrations > 0.46 <i>μ</i>mol L<sup>−1</sup>. These findings contrast those previously reported in larger chain forming diatoms, for example, <i>Chaetoceros</i>, which appear to circumvent diffusion limitation at low ambient <span></span><math>\n <mrow>\n <msubsup>\n <mi>NO</mi>\n <mn>3</mn>\n <mo>−</mo>\n </msubsup>\n </mrow></math> concentrations and succeed <i>S. marinoi</i> during spring blooms.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 10","pages":"2391-2405"},"PeriodicalIF":3.8000,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12677","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Limnology and Oceanography","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/lno.12677","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"LIMNOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Formation of large colonies by phytoplankton is considered a disadvantage during low nutrient and non-turbulent conditions because of diffusion limitation and competition by neighboring cells. This is assumed by diffusion models and not empirical measurements. Here, we measured cell-specific dissolved inorganic carbon (DIC) and nitrate () assimilation in two chain-forming Skeletonema marinoi strains by combining secondary ion mass spectrometry with stable isotopic tracer incubations. The pelagic strains were recently germinated from resting stages and thus not adapted to high nutrient regimes of laboratory cultures. During the exponential phase, the cells assimilated excess relative to DIC. The DIC and assimilation varied with chain length or the position of the cell within chains but did not follow any consistent trend. Solitary cells were rare and did not exceed 6% of all cells. During the nitrogen-limited stationary phase, assimilation was lower than modeled by mass transfer theory at diffusion limitation. assimilation rates were apparently limited by the biological uptake rate at nitrate concentrations < 0.46 μmol L−1. We conclude that S. marinoi is adapted to high nutrient concentrations and may seldom be diffusion limited in coastal waters with ambient concentrations > 0.46 μmol L−1. These findings contrast those previously reported in larger chain forming diatoms, for example, Chaetoceros, which appear to circumvent diffusion limitation at low ambient concentrations and succeed S. marinoi during spring blooms.
期刊介绍:
Limnology and Oceanography (L&O; print ISSN 0024-3590, online ISSN 1939-5590) publishes original articles, including scholarly reviews, about all aspects of limnology and oceanography. The journal''s unifying theme is the understanding of aquatic systems. Submissions are judged on the originality of their data, interpretations, and ideas, and on the degree to which they can be generalized beyond the particular aquatic system examined. Laboratory and modeling studies must demonstrate relevance to field environments; typically this means that they are bolstered by substantial "real-world" data. Few purely theoretical or purely empirical papers are accepted for review.