DOI: 10.5061/dryad.jm63xsjkq
title: Equatorial upwelling of phosphorus drives Atlantic N<sub>2</sub> fixation and <em>Sargassum</em> blooms

description: The Great Atlantic Sargassum Belt (GASB) first appeared in 2011 and
 quickly became the largest interconnected floating biome globally.
 Sargassum spp. requires both phosphorus (P) and nitrogen (N) for growth,
 yet the sources fueling the GASB are unclear. Here, we use coral–bound
 nitrogen isotopes from six coral cores to reconstruct N2 fixation, the
 primary source of bioavailable N to the surface ocean across the wider
 Caribbean over the past 120 years. Our data indicate that changes in N2
 fixation were controlled by multidecadal and interannual changes in the
 supply of excess P from equatorial upwelling in the Atlantic. We show that
 the supply of P from equatorial upwelling and N from the N2 fixation
 response can explain the extent of the GASB since 2011.
description: # Equatorial upwelling of phosphorus drives Atlantic N~2~ fixation and
 *Sargassum* blooms This Excel file contains time series data combining
 coral geochemical records (δ¹⁵N and δ¹⁸O), climate indices, Sargassum
 biomass, and major riverine outflows. The dataset integrates multiple
 spatially distributed records to examine long-term variability in nutrient
 dynamics, climate forcing, and ecological responses in the Caribbean and
 tropical Atlantic. Values that were not available or are missing are
 indicated as N/A. ## Column Reference Table File:
 Caribbean_data_for_DRYAD.xlsx | Column Name | Description | |
 :----------------------------------- |
 :------------------------------------------------------------------------------------------------- | | **Year\_CR\_Turneffe** | Calendar year of sampling for coral records from Turneffe Atoll (Belize) and Cahuita (Costa Rica). | | **Cahuita Costa Rica\_d18O\_ts** | Coral δ¹⁸O time series from Cahuita, Costa Rica (proxy for SST and freshwater input). | | **d15N\_CR** | Coral-bound δ¹⁵N from Cahuita, Costa Rica (proxy for nitrogen source/processing). | | **Turneffe Atoll\_d18O\_ts** | Coral δ¹⁸O time series from Turneffe Atoll, Belize. | | **d15N\_Turneffe** | Coral-bound δ¹⁵N from Turneffe Atoll. | | **Date\_MQ** | Sampling date for Martinique (MQ) site. | | **d18O\_MQ** | Coral δ¹⁸O from Martinique. | | **d15N\_MQ** | Coral δ¹⁵N from Martinique. | | **Year Bermuda** | Calendar year for Bermuda coral samples. | | **d15N Bermuda** | Coral δ¹⁵N from Bermuda. | | **Year\_CUBA** | Calendar year for Cuban coral records. | | **d15N\_CUBA** | Coral δ¹⁵N from Cuba. | | **d15N\_Mexico** | Coral δ¹⁵N from Mexico. | | **Year\_Tobago** | Calendar year for Tobago coral samples. | | **d15N\_Tobago** | Coral δ¹⁵N from Tobago. | | **Year AMM** | Year corresponding to Atlantic Meridional Mode (AMM) values. | | **AMM\_SST** | Sea Surface Temperature anomalies associated with the AMM. | | **AMM\_Wind** | Wind anomalies associated with the AMM. | | **AMO** | Atlantic Multidecadal Oscillation index value. | | **average\_year** | Averaged year across all coral records included. | | **AVERAGE\_rescaled** | Composite δ¹⁵N record rescaled across sites. | | **error\_propagated** | Propagated error estimate for the rescaled average. | | **AVERAGE\_rescaled\_noCR\_BM\_TB** | Rescaled δ¹⁵N average excluding Costa Rica, Bermuda, and Tobago. | | **error\_propagated2** | Propagated error for the reduced-site average. | | **Months Sargassum** | Month of Sargassum observation. | | **Monthly Sargassum biomass (tons)** | Monthly biomass estimates of pelagic Sargassum (tons). | | **Year\_SST\_SSS** | Year corresponding to SST/SSS data. | | **SST\_10-20N\_20-60W** | Sea Surface Temperature average over 10–20°N, 20–60°W. | | **SSS\_10-20N\_20-60W** | Sea Surface Salinity average over the same region. | | **U\_windstress\_10\_20N\_58\_62W** | Zonal wind stress (10–20°N, 58–62°W). | | **windspeed\_0\_20N\_20\_50W** | Mean wind speed (0–20°N, 20–50°W). | | **Geo\_u\_12\_18N\_60\_80W (CC)** | Geostrophic zonal velocity (12–18°N, 60–80°W), Caribbean Current proxy. | | **DU\_scav\_areaweight** | Dust deposition (scavenging flux, area-weighted). | | **DU\_ddep\_areaweight** | Dust dry deposition (area-weighted). | | **BC\_scav\_areaweight** | Black carbon scavenging flux (area-weighted). | | **Bc\_ddep\_areaweight** | Black carbon dry deposition (area-weighted). | | **BC\_total\_areaweight** | Total black carbon deposition (area-weighted). | | **DU\_total\_areaweight** | Total dust deposition (area-weighted). | | **Obidos\_Amazon\_m3\_s** | Amazon River discharge at Óbidos station (m³/s). | | **Ciudad Bolivar\_Orinoco\_m3\_s** | Orinoco River discharge at Ciudad Bolívar (m³/s). | | **Year Pstar** | Year corresponding to P\* (phosphorus excess) record. | | **Pstar** | Phosphorus excess (indicator of nutrient balance, micro Molar). | | **Amazon\_outflow\_date** | Date of Amazon outflow measurement. | | **Amazon\_outflow\_km3** | Amazon River outflow volume (km³). | | **Orinoco\_outflow\_date** | Date of Orinoco outflow measurement. | | **Orinoco\_outflow\_km3** | Orinoco River outflow volume (km³). | Links to other publicly accessible locations of the data: * [https://climexp.knmi.nl](http://...) Data was derived from the following sources: * Climate Explorer was used for gridded satellite-derived products (SST, SSS, windspeed, windstress) by using the geographical extent as indicated in the manuscript ## Code/Software No software was used for data analysis, and the codes used for figures and data analyses are available on GitHub ([https://github.com/marinejon/](https://github.com/marinejon/))