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Seasonal and mesoscale variability of primary production in the deep winter-mixing region of the NW Mediterranean

Seasonal and mesoscale variability of primary production in the deep winter-mixing region of the NW Mediterranean
Seasonal and mesoscale variability of primary production in the deep winter-mixing region of the NW Mediterranean
The phytoplankton bloom in the Liguro-Provençal deep convection region represents one of the main fertilization mechanisms in the Mediterranean. This communication examines nano- and microphytoplankton observations, and measurements of primary production and chlorophyll a concentration (Chl a) in the southwestern part of the deep convection region, where such information is scarce. Data were obtained from four cruises, carried out in 2005 (EFLUBIO project) and 2009 (FAMOSO project), covering the seasonality between mid-March and September in the region. Our aims were to constrain primary production estimates and to ascertain the importance of short-term variability on the photosynthetic response of phytoplankton assemblages during bloom, post-bloom and late-summer stratification periods in the area. Overall, the initial slope of the P-E relationship (αB) increased and the Chl a-normalized photosynthetic rate (PmB) decreased with increasing optical depth of sample origin, but there were exceptions. In general, there were marked seasonal trends, with stratification increasing and Chl a concentration, primary production and dissolved inorganic nitrogen and phosphate fluxes decreasing from winter to late summer. Chl a at 5m depth reached a maximum of 7mgm-3 on 25 March 2005, one of the highest values measured in the region. Average surface values (±SD) ranged from respectively 2.4±2.3mgm-3 and 2±0.7mgm-3 in the March 2005 and March 2009 cruises to 0.12±0.01mgm-3 in the September 2009 cruise. Vertically integrated (0-80m) primary production (PPint) attained 1800mgCm-2d-1 in March 2009, with an average of 1024±523mgCm-2d-1, and decreased to a mean of 141±0.43mgCm-2d-1 in September 2009. Superimposed to the seasonal trends, there was a considerable within-cruise variability of biomass and primary production, especially during the spring-winter bloom and post-bloom periods, when PPint could change more than threefold within a few days. These differences were mainly associated with the intense hydrographic mesoscale and sub-mesoscale heterogeneity in the region and with the differences in the physiological and ecological history of the phytoplankton communities inhabiting the different water bodies. In late summer, most PPint variability could be explained by fluctuations in surface incident irradiance.
Chlorophyll a, Mesoscale, NW Mediterranean, Phytoplankton, Primary production, Seasonal bloom
0967-0637
45-61
Estrada, Marta
c2442b9b-5e51-4f1c-863d-a3af1e3805c9
Latasa, Mikel
e8f88d8c-49e2-4e11-9ec1-a5f9b173a2fd
Emelianov, Mikhail
077687f7-cd07-4da0-a4c6-e758fceb9688
Gutiérrez-Rodríguez, Andrés
465bbe14-84f0-4452-af5f-ba8d32ba91e1
Fernández-Castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Isern-Fontanet, Jordi
95cdd28b-2e00-47a8-b828-f2a6ce2bf5af
Mouriño-Carballido, Beatriz
1bfd941d-9ec6-473f-94bd-bb6faac56fa5
Salat, Jordi
9cb292e6-b185-407c-be29-c98072b189ee
Vidal, Montserrat
00ed9d5f-e097-4e37-a0a4-012e0e4283ca
Estrada, Marta
c2442b9b-5e51-4f1c-863d-a3af1e3805c9
Latasa, Mikel
e8f88d8c-49e2-4e11-9ec1-a5f9b173a2fd
Emelianov, Mikhail
077687f7-cd07-4da0-a4c6-e758fceb9688
Gutiérrez-Rodríguez, Andrés
465bbe14-84f0-4452-af5f-ba8d32ba91e1
Fernández-Castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Isern-Fontanet, Jordi
95cdd28b-2e00-47a8-b828-f2a6ce2bf5af
Mouriño-Carballido, Beatriz
1bfd941d-9ec6-473f-94bd-bb6faac56fa5
Salat, Jordi
9cb292e6-b185-407c-be29-c98072b189ee
Vidal, Montserrat
00ed9d5f-e097-4e37-a0a4-012e0e4283ca

Estrada, Marta, Latasa, Mikel, Emelianov, Mikhail, Gutiérrez-Rodríguez, Andrés, Fernández-Castro, Bieito, Isern-Fontanet, Jordi, Mouriño-Carballido, Beatriz, Salat, Jordi and Vidal, Montserrat (2014) Seasonal and mesoscale variability of primary production in the deep winter-mixing region of the NW Mediterranean. Deep-Sea Research Part I: Oceanographic Research Papers, 94, 45-61. (doi:10.1016/j.dsr.2014.08.003).

Record type: Article

Abstract

The phytoplankton bloom in the Liguro-Provençal deep convection region represents one of the main fertilization mechanisms in the Mediterranean. This communication examines nano- and microphytoplankton observations, and measurements of primary production and chlorophyll a concentration (Chl a) in the southwestern part of the deep convection region, where such information is scarce. Data were obtained from four cruises, carried out in 2005 (EFLUBIO project) and 2009 (FAMOSO project), covering the seasonality between mid-March and September in the region. Our aims were to constrain primary production estimates and to ascertain the importance of short-term variability on the photosynthetic response of phytoplankton assemblages during bloom, post-bloom and late-summer stratification periods in the area. Overall, the initial slope of the P-E relationship (αB) increased and the Chl a-normalized photosynthetic rate (PmB) decreased with increasing optical depth of sample origin, but there were exceptions. In general, there were marked seasonal trends, with stratification increasing and Chl a concentration, primary production and dissolved inorganic nitrogen and phosphate fluxes decreasing from winter to late summer. Chl a at 5m depth reached a maximum of 7mgm-3 on 25 March 2005, one of the highest values measured in the region. Average surface values (±SD) ranged from respectively 2.4±2.3mgm-3 and 2±0.7mgm-3 in the March 2005 and March 2009 cruises to 0.12±0.01mgm-3 in the September 2009 cruise. Vertically integrated (0-80m) primary production (PPint) attained 1800mgCm-2d-1 in March 2009, with an average of 1024±523mgCm-2d-1, and decreased to a mean of 141±0.43mgCm-2d-1 in September 2009. Superimposed to the seasonal trends, there was a considerable within-cruise variability of biomass and primary production, especially during the spring-winter bloom and post-bloom periods, when PPint could change more than threefold within a few days. These differences were mainly associated with the intense hydrographic mesoscale and sub-mesoscale heterogeneity in the region and with the differences in the physiological and ecological history of the phytoplankton communities inhabiting the different water bodies. In late summer, most PPint variability could be explained by fluctuations in surface incident irradiance.

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More information

Published date: 1 December 2014
Keywords: Chlorophyll a, Mesoscale, NW Mediterranean, Phytoplankton, Primary production, Seasonal bloom

Identifiers

Local EPrints ID: 453583
URI: http://eprints.soton.ac.uk/id/eprint/453583
ISSN: 0967-0637
PURE UUID: b1e09281-c263-4421-bffc-547da88820b6
ORCID for Bieito Fernández-Castro: ORCID iD orcid.org/0000-0001-7797-854X

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Date deposited: 20 Jan 2022 17:31
Last modified: 21 Jan 2022 02:54

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Contributors

Author: Marta Estrada
Author: Mikel Latasa
Author: Mikhail Emelianov
Author: Andrés Gutiérrez-Rodríguez
Author: Jordi Isern-Fontanet
Author: Beatriz Mouriño-Carballido
Author: Jordi Salat
Author: Montserrat Vidal

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