A gulf-wide synoptic isoscape of zooplankton isotope ratios reveals the importance of nitrogen fixation in supporting secondary production in the central Gulf of Mexico
A synoptic gulf-wide isoscape of carbon (δ13C) and nitrogen (δ15N) in the Gulf of Mexico based on mesozooplankton (335-1000 um) was used as a proxy for the isotopic baseline and for calculating regional contributions of dissolved inorganic nitrogen sources. Mesozooplankton were sampled at 0-200 m (d...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Frontiers Media S.A.
2023-01-01
|
| Series: | Frontiers in Marine Science |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/articles/10.3389/fmars.2022.1025387/full |
| _version_ | 1797955182021050368 |
|---|---|
| author | Oscar Gabriel Hernández-Sánchez Víctor F. Camacho-Ibar Leticia Barbero Juan Carlos Herguera Sharon Z. Herzka |
| author_facet | Oscar Gabriel Hernández-Sánchez Víctor F. Camacho-Ibar Leticia Barbero Juan Carlos Herguera Sharon Z. Herzka |
| author_sort | Oscar Gabriel Hernández-Sánchez |
| collection | DOAJ |
| description | A synoptic gulf-wide isoscape of carbon (δ13C) and nitrogen (δ15N) in the Gulf of Mexico based on mesozooplankton (335-1000 um) was used as a proxy for the isotopic baseline and for calculating regional contributions of dissolved inorganic nitrogen sources. Mesozooplankton were sampled at 0-200 m (depth permitting) during the XIXIMI-06 and GOMECC-3 cruises held during the summer of 2017. A striking latitudinal gradient was found in δ15N values of zooplankton, with the highest values (10.4 ± 1.2‰) found over the northern shelf, and lowest values in the central, oligotrophic gulf (1.9 ± 0.5‰). To estimate the fractional contribution of potential nitrogen sources, the gulf was divided into six regions based on the spatial distribution of surface Chl-a, SST from remote sensing products and likely region-specific source contributions. A literature survey of (δ13C and δ15N values of particulate organic matter was used to characterize region-specific endpoint isotope ratios for use in a Bayesian isotope mixing model. Regional differences in δ15N values and the results of mixing models indicated nitrogen fixation is most likely an important source (45-74% contribution) of new nitrogen in the oceanic regions of the Gulf, the Loop Current and the Yucatan Shelf. In the oligotrophic gulf, the potential input of relatively light nitrate that reflects remineralization of surface layer POM or the excretion of light nitrogen by heterotrophs was insufficient to explain the low δ15N values found in the central Gulf, although it could account for about 40% of the N supporting secondary production. The high nitrogen isotope ratios found in the northern shelf were attributed to denitrified N (60%) and the inflow of heavy nitrogen from the Mississippi-Atchafalaya river system. Our results support the potential importance of fixed nitrogen in the deep waters of the Gulf of Mexico during the summer, characteristic for its highly stratified surface waters. |
| first_indexed | 2024-04-10T23:30:16Z |
| format | Article |
| id | doaj.art-10179fd62f6b4ee0bb6fa94dfebb7807 |
| institution | Directory Open Access Journal |
| issn | 2296-7745 |
| language | English |
| last_indexed | 2024-04-10T23:30:16Z |
| publishDate | 2023-01-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Marine Science |
| spelling | doaj.art-10179fd62f6b4ee0bb6fa94dfebb78072023-01-12T06:58:38ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452023-01-01910.3389/fmars.2022.10253871025387A gulf-wide synoptic isoscape of zooplankton isotope ratios reveals the importance of nitrogen fixation in supporting secondary production in the central Gulf of MexicoOscar Gabriel Hernández-Sánchez0Víctor F. Camacho-Ibar1Leticia Barbero2Juan Carlos Herguera3Sharon Z. Herzka4Departamento de Oceanografía Biológica, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), 3918 Carretera Ensenada-Tijuana, Zona Playitas, Ensenada, Baja California, MexicoInstituto de Investigaciones Oceanológicas, Universidad Autónoma de Baja California (UABC), Ensenada, Baja California, MexicoCooperative Institute for Marine and Atmospheric Studies (CIMAS), University of Miami, and National Oceanic and Atmospheric Administration (NOAAs) Atlantic Oceanographic and Meteorological Laboratory, Miami, FL, United StatesDepartamento de Ecología Marina, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, Baja California, MexicoDepartamento de Oceanografía Biológica, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), 3918 Carretera Ensenada-Tijuana, Zona Playitas, Ensenada, Baja California, MexicoA synoptic gulf-wide isoscape of carbon (δ13C) and nitrogen (δ15N) in the Gulf of Mexico based on mesozooplankton (335-1000 um) was used as a proxy for the isotopic baseline and for calculating regional contributions of dissolved inorganic nitrogen sources. Mesozooplankton were sampled at 0-200 m (depth permitting) during the XIXIMI-06 and GOMECC-3 cruises held during the summer of 2017. A striking latitudinal gradient was found in δ15N values of zooplankton, with the highest values (10.4 ± 1.2‰) found over the northern shelf, and lowest values in the central, oligotrophic gulf (1.9 ± 0.5‰). To estimate the fractional contribution of potential nitrogen sources, the gulf was divided into six regions based on the spatial distribution of surface Chl-a, SST from remote sensing products and likely region-specific source contributions. A literature survey of (δ13C and δ15N values of particulate organic matter was used to characterize region-specific endpoint isotope ratios for use in a Bayesian isotope mixing model. Regional differences in δ15N values and the results of mixing models indicated nitrogen fixation is most likely an important source (45-74% contribution) of new nitrogen in the oceanic regions of the Gulf, the Loop Current and the Yucatan Shelf. In the oligotrophic gulf, the potential input of relatively light nitrate that reflects remineralization of surface layer POM or the excretion of light nitrogen by heterotrophs was insufficient to explain the low δ15N values found in the central Gulf, although it could account for about 40% of the N supporting secondary production. The high nitrogen isotope ratios found in the northern shelf were attributed to denitrified N (60%) and the inflow of heavy nitrogen from the Mississippi-Atchafalaya river system. Our results support the potential importance of fixed nitrogen in the deep waters of the Gulf of Mexico during the summer, characteristic for its highly stratified surface waters.https://www.frontiersin.org/articles/10.3389/fmars.2022.1025387/fullmesozooplanktonisoscapenitrogen sourcesBayesian mixing modelN2 fixationGulf of Mexico (GOM) |
| spellingShingle | Oscar Gabriel Hernández-Sánchez Víctor F. Camacho-Ibar Leticia Barbero Juan Carlos Herguera Sharon Z. Herzka A gulf-wide synoptic isoscape of zooplankton isotope ratios reveals the importance of nitrogen fixation in supporting secondary production in the central Gulf of Mexico Frontiers in Marine Science mesozooplankton isoscape nitrogen sources Bayesian mixing model N2 fixation Gulf of Mexico (GOM) |
| title | A gulf-wide synoptic isoscape of zooplankton isotope ratios reveals the importance of nitrogen fixation in supporting secondary production in the central Gulf of Mexico |
| title_full | A gulf-wide synoptic isoscape of zooplankton isotope ratios reveals the importance of nitrogen fixation in supporting secondary production in the central Gulf of Mexico |
| title_fullStr | A gulf-wide synoptic isoscape of zooplankton isotope ratios reveals the importance of nitrogen fixation in supporting secondary production in the central Gulf of Mexico |
| title_full_unstemmed | A gulf-wide synoptic isoscape of zooplankton isotope ratios reveals the importance of nitrogen fixation in supporting secondary production in the central Gulf of Mexico |
| title_short | A gulf-wide synoptic isoscape of zooplankton isotope ratios reveals the importance of nitrogen fixation in supporting secondary production in the central Gulf of Mexico |
| title_sort | gulf wide synoptic isoscape of zooplankton isotope ratios reveals the importance of nitrogen fixation in supporting secondary production in the central gulf of mexico |
| topic | mesozooplankton isoscape nitrogen sources Bayesian mixing model N2 fixation Gulf of Mexico (GOM) |
| url | https://www.frontiersin.org/articles/10.3389/fmars.2022.1025387/full |
| work_keys_str_mv | AT oscargabrielhernandezsanchez agulfwidesynopticisoscapeofzooplanktonisotoperatiosrevealstheimportanceofnitrogenfixationinsupportingsecondaryproductioninthecentralgulfofmexico AT victorfcamachoibar agulfwidesynopticisoscapeofzooplanktonisotoperatiosrevealstheimportanceofnitrogenfixationinsupportingsecondaryproductioninthecentralgulfofmexico AT leticiabarbero agulfwidesynopticisoscapeofzooplanktonisotoperatiosrevealstheimportanceofnitrogenfixationinsupportingsecondaryproductioninthecentralgulfofmexico AT juancarlosherguera agulfwidesynopticisoscapeofzooplanktonisotoperatiosrevealstheimportanceofnitrogenfixationinsupportingsecondaryproductioninthecentralgulfofmexico AT sharonzherzka agulfwidesynopticisoscapeofzooplanktonisotoperatiosrevealstheimportanceofnitrogenfixationinsupportingsecondaryproductioninthecentralgulfofmexico AT oscargabrielhernandezsanchez gulfwidesynopticisoscapeofzooplanktonisotoperatiosrevealstheimportanceofnitrogenfixationinsupportingsecondaryproductioninthecentralgulfofmexico AT victorfcamachoibar gulfwidesynopticisoscapeofzooplanktonisotoperatiosrevealstheimportanceofnitrogenfixationinsupportingsecondaryproductioninthecentralgulfofmexico AT leticiabarbero gulfwidesynopticisoscapeofzooplanktonisotoperatiosrevealstheimportanceofnitrogenfixationinsupportingsecondaryproductioninthecentralgulfofmexico AT juancarlosherguera gulfwidesynopticisoscapeofzooplanktonisotoperatiosrevealstheimportanceofnitrogenfixationinsupportingsecondaryproductioninthecentralgulfofmexico AT sharonzherzka gulfwidesynopticisoscapeofzooplanktonisotoperatiosrevealstheimportanceofnitrogenfixationinsupportingsecondaryproductioninthecentralgulfofmexico |