Benthic nitrogen fixation in Zostera marina meadows in an upwelling-influenced coastal lagoon

Benthic nitrogen fixation in Zostera marina meadows in an upwelling-influenced coastal lagoon

Dinitrogen (N2) fixation rates were determined in the phyllosphere and in sediments with and without the presence of eelgrass (Zostera marina) in San Quintín Bay, an upwelling-influenced coastal lagoon in the NE Pacific. Samples were collected during winter 2015 at 4 sites with a gradient of oceanic...

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Autores principales: Hernández-López, Julieta, Camacho-Ibar, Víctor F, Macías-Tapia, Alfonso, McGlathery, Karen J, Daesslé, Luis W, Sandoval-Gil, Jose M
Formato: Online
Idioma:eng
Publicado: Iniversidad Autónoma de Baja California 2017
Acceso en liña:https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/2700
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institution Ciencias Marinas
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language eng
format Online
author Hernández-López, Julieta
Camacho-Ibar, Víctor F
Macías-Tapia, Alfonso
McGlathery, Karen J
Daesslé, Luis W
Sandoval-Gil, Jose M
spellingShingle Hernández-López, Julieta
Camacho-Ibar, Víctor F
Macías-Tapia, Alfonso
McGlathery, Karen J
Daesslé, Luis W
Sandoval-Gil, Jose M
Benthic nitrogen fixation in Zostera marina meadows in an upwelling-influenced coastal lagoon
author_facet Hernández-López, Julieta
Camacho-Ibar, Víctor F
Macías-Tapia, Alfonso
McGlathery, Karen J
Daesslé, Luis W
Sandoval-Gil, Jose M
author_sort Hernández-López, Julieta
title Benthic nitrogen fixation in Zostera marina meadows in an upwelling-influenced coastal lagoon
title_short Benthic nitrogen fixation in Zostera marina meadows in an upwelling-influenced coastal lagoon
title_full Benthic nitrogen fixation in Zostera marina meadows in an upwelling-influenced coastal lagoon
title_fullStr Benthic nitrogen fixation in Zostera marina meadows in an upwelling-influenced coastal lagoon
title_full_unstemmed Benthic nitrogen fixation in Zostera marina meadows in an upwelling-influenced coastal lagoon
title_sort benthic nitrogen fixation in zostera marina meadows in an upwelling-influenced coastal lagoon
description Dinitrogen (N2) fixation rates were determined in the phyllosphere and in sediments with and without the presence of eelgrass (Zostera marina) in San Quintín Bay, an upwelling-influenced coastal lagoon in the NE Pacific. Samples were collected during winter 2015 at 4 sites with a gradient of oceanic influence and contrasting impact from oyster aquaculture. N2 fixation rates were determined with the acetylene reduction assay. Treatments under light and in the dark, and with and without sodium molybdate resulted in similar fixation rates, suggesting that heterotrophic nonsulfate-reducing bacteria made the largest contribution to N2 fixation, while sulfate-reducing bacteria had low fixation activity at most stations. N2-fixation rates in sediments ranged from 7 to 12 micrometers mol m–2 h–1 and were similar to those in other temperate seagrass-dominated estuaries. Winter conditions were likely responsible for small spatial differences in N2 fixation rates throughout the lagoon, even between vegetated and unvegetated sites and among depth sections of sediment cores. During winter, Z. marina growth rates and biomass are low, resulting in low and less variable release of labile organic carbon, which acts as substrate for diazotrophs. The lowest N2 fixation rates were measured at a site where high denitrification rates have been observed, probably reflecting a competition between diazotrophs and denitrifiers. The highest fixation rates were measured at the innermost station where oceanic nitrate is scarce. Epiphytic bacteria contributed ~7% of the total N2 fixation, with rates of <0.5 micrometers mol m–2 h–1. N2 fixation potentially supplied 5–10% of Z. marina N requirements and could supply ~30% of the N loss via denitrification in winter.
publisher Iniversidad Autónoma de Baja California
publishDate 2017
url https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/2700
_version_ 1797332411174879232
spelling oai:cienciasmarinas.com.mx:article-27002024-04-05T19:16:48Z Benthic nitrogen fixation in Zostera marina meadows in an upwelling-influenced coastal lagoon Fijación bentónica de nitrógeno en praderas de Zostera marina de una laguna costera influenciada por surgencias Hernández-López, Julieta Camacho-Ibar, Víctor F Macías-Tapia, Alfonso McGlathery, Karen J Daesslé, Luis W Sandoval-Gil, Jose M Dinitrogen (N2) fixation rates were determined in the phyllosphere and in sediments with and without the presence of eelgrass (Zostera marina) in San Quintín Bay, an upwelling-influenced coastal lagoon in the NE Pacific. Samples were collected during winter 2015 at 4 sites with a gradient of oceanic influence and contrasting impact from oyster aquaculture. N2 fixation rates were determined with the acetylene reduction assay. Treatments under light and in the dark, and with and without sodium molybdate resulted in similar fixation rates, suggesting that heterotrophic nonsulfate-reducing bacteria made the largest contribution to N2 fixation, while sulfate-reducing bacteria had low fixation activity at most stations. N2-fixation rates in sediments ranged from 7 to 12 micrometers mol m–2 h–1 and were similar to those in other temperate seagrass-dominated estuaries. Winter conditions were likely responsible for small spatial differences in N2 fixation rates throughout the lagoon, even between vegetated and unvegetated sites and among depth sections of sediment cores. During winter, Z. marina growth rates and biomass are low, resulting in low and less variable release of labile organic carbon, which acts as substrate for diazotrophs. The lowest N2 fixation rates were measured at a site where high denitrification rates have been observed, probably reflecting a competition between diazotrophs and denitrifiers. The highest fixation rates were measured at the innermost station where oceanic nitrate is scarce. Epiphytic bacteria contributed ~7% of the total N2 fixation, with rates of <0.5 micrometers mol m–2 h–1. N2 fixation potentially supplied 5–10% of Z. marina N requirements and could supply ~30% of the N loss via denitrification in winter. Se determinaron las tasas de fijación de nitrógeno molecular (N2) en la filosfera y en sedimentos con y sin presencia de pasto marino (Zostera marina) en bahía San Quintín, una laguna costera del Pacífico nororiental influenciada por surgencias. Se recolectaron muestras durante el invierno de 2015 en 4 sitios a lo largo de un gradiente de influencia oceánica y con diferente grado de impacto por la ostricultura. Las tasas de fijación de N2 se determinaron con el método de reducción de acetileno. Las tasas de fijación en los tratamientos con luz y en oscuridad, y en los tratamientos con y sin molibdato de sodio fueron similares, lo que sugiere que las bacterias heterótrofas no sulfatoreductoras fueron las principales contribuyentes a la fijación de N2, mientras que las sulfatoreductoras presentaron baja actividad de fijación en la mayoría de los sitios. Las tasas de fijación de N2 presentaron un intervalo de 7 a 12 micrómetros mol m–2 h–1 y fueron similares a las reportadas para otros estuarios dominados por praderas de pastos marinos en zonas templadas. Las condiciones ambientales de invierno probablemente determinaron las pequeñas diferencias en las tasas de fijación de N2 a lo largo de la laguna, incluso entre sitios con y sin vegetación o entre las diferentes secciones de los núcleos de sedimento. Durante el invierno, las tasas de crecimiento y las biomasas de Z. marina son bajas, lo que resulta en una liberación baja y poco variable de carbono orgánico lábil, sustrato importante para los diazótrofos. Las tasas de fijación de N2 más bajas se midieron en el sitio donde aparentemente se presentan altas tasas de desnitrificación, lo que probablemente refleja una competencia entre diazótrofos y desnitrificadores. Las tasas de fijación más altas se midieron en la estación más interna, donde es escaso el aporte de nitrato oceánico. Las bacterias epífitas contribuyeron alrededor del 7% de la fijación total de N2, con tasas <0.5 micrómetros mol m–2 h–1. La fijación de N2 potencialmente abasteció entre el 5% y 10% del N requerido por Z. marina y podría abastecer ~30% del N que se pierde vía la desnitrificación en invierno. Iniversidad Autónoma de Baja California 2017-03-31 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Peer-reviewed Article Artículo Arbitrado application/pdf text/xml text/xml https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/2700 10.7773/cm.v43i1.2700 Ciencias Marinas; Vol. 43 No. 1 (2017); 35-53 Ciencias Marinas; Vol. 43 Núm. 1 (2017); 35-53 2395-9053 0185-3880 eng https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/2700/1619 https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/2700/420420593 https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/2700/420420770 Copyright (c) 2017 Ciencias Marinas https://creativecommons.org/licenses/by/4.0

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