BGC‐Argo Floats Observe Nitrate Injection and Spring Phytoplankton Increase in the Surface Layer of Levantine Sea (Eastern Mediterranean)

D’Ortenzio, Fabrizio; Taillandier, Vincent; Claustre, Hervé; Coppola, Laurent; Conan, Pascal; Dumas, Franck; Madron, X. Durrieu Du; Fourrier, Marine; Gogou, Alexandra; Karageorgis, A. P.; Lefèvre, D.; Leymarie, Édouard; Oviedo, Angela Maria; Pavlidou, Alexandra; Poteau, Antoine; Poulain, Pierre-Marie; Prieur, Louis; Psarra, Stella; Puyo‐pay, M.; d’Alcalà, Maurizio Ribera; Schmechtig, Catherine; Terrats, L.; Velaoras, Dimitris; Wagener, Thibaut; Wimart-Rousseau, Cathy

doi:10.1029/2020gl091649

Cited by 13 publications

(5 citation statements)

References 58 publications

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“…However, it is important to note that surface Chl-a as seen by satellites, is not representative of the total phytoplankton biomass in the Mediterranean waters, i.e. subsurface phytoplankton dynamics, in particular those associated with the Deep Chlorophyll Maximum (DCM) at the base of the upper mixed layer (Barbieux et al, 2019;D'Ortenzio et al, 2021) could be highly underestimated.…”

Section: Biogeochemical Settingmentioning

confidence: 99%

Optical Properties and Biochemical Indices of Marine Particles in the Open Mediterranean Sea: The R/V Maria S. Merian Cruise, March 2018

et al. 2021

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A rich data set on particulate matter optical properties and parameters (beam attenuation coefficient, volume concentration, particle size and PSD slope), accompanied by measurements of biochemical indices (particulate organic carbon, particulate nitrogen and their stable isotopic composition) was obtained from the surface to deep waters across the Mediterranean Sea, in March-April 2018. A decrease of beam attenuation coefficients, total particle volume concentrations, particulate organic carbon and nitrogen concentrations was noted towards the eastern Mediterranean Sea (EMed) in comparison to the western Mediterranean Sea (WMed). LISST-derived optical properties were significantly correlated with water mass characteristics. Overall, the most turbid water mass identified in the Mediterranean Sea was the Surface Atlantic water (AW), and the most transparent was the Transitional Mediterranean Water (TMW) in the Cretan Sea, whereas a general decrease in particulate matter concentration is observed from the WMed towards the EMed. Relatively depleted δ13C-POC values in the particle pool of the open Mediterranean Sea can be attributed to contribution from terrestrial inputs, mainly via atmospheric deposition. Throughout the entire water column, a significant positive correlation between particle beam attenuation coefficient and particulate organic carbon concentration is observed in the open Mediterranean Sea. Such relationship suggests the predominance of organic particles with biogenic origin. POC concentration and particle median diameter D50 are significantly and negatively correlated both in the WMed and the EMed Sea, confirming that small particles are POC-rich. At depth, a prominent decrease of most measured parameters was observed, with the exception of particle median diameter that increased substantially in the EMed towards the deep sea, suggesting potentially enhanced aggregation processes. The low particle size distribution slope ξ observed in the EMed, corresponding to larger particle populations, supports the above notion. Basin-wide Rayleigh-type isotopic fractionation in vertical profiles of δ15N-PN across the Mediterranean Sea, underlines the differences in the trophic characters of the two sub-basins and highlights the role of circulation changes on biogeochemical parameters and the redistribution of particulate matter as a source of nutrients in the water column.

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Section: Biogeochemical Settingmentioning

confidence: 99%

Optical Properties and Biochemical Indices of Marine Particles in the Open Mediterranean Sea: The R/V Maria S. Merian Cruise, March 2018

et al. 2021

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“…In the frame of the PERLE project (the Pelagic Ecosystem Response to deep water formation in the Levant Experiment), an intense in situ survey of the Levantine area was carried out during 2018(D'Ortenzio et al, 2020. This study reports on a new oceanic inorganic carbon dataset acquired over three different periods of the year in the South Cretan area (described as the North Western Levantine Basin or NWLB hereafter) (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Seasonal and Interannual Variability of the CO2 System in the Eastern Mediterranean Sea: A Case Study in the North Western Levantine Basin

et al. 2021

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The seasonal variability of the carbonate system in the eastern Mediterranean Sea (EMed) was investigated based on discrete total alkalinity (AT), total dissolved inorganic carbon (CT), and pH measurements collected during three cruises around Crete between June 2018 and March 2019. This study presents a detailed description of this new carbonate chemistry dataset in the eastern Mediterranean Sea. We show that the North Western Levantine Basin (NWLB) is unique in terms of range of AT variation vs. CT variation in the upper water column over an annual cycle. The reasons for this singularity of the NWLB can be explained by the interplay between strong evaporation and the concomitant consumption of CT by autotrophic processes. The high range of AT variations, combined to temperature changes, has a strong impact on the variability of the seawater pCO2 (pCO2SW). Based on Argo float data, an entire annual cycle for pCO2SW in the NWLB has been reconstructed in order to estimate the temporal sequence of the potential “source” and “sink” of atmospheric CO2. By combining this dataset with previous observations in the NWLB, this study shows a significant ocean acidification and a decrease in the oceanic surface pHT25 of −0.0024 ± 0.0004 pHT25 units.a–1. The changes in the carbonate system are driven by the increase of atmospheric CO2 but also by unexplained temporal changes in the surface AT content. If we consider that the EMed will, in the future, encounter longer, more intense and warmer summer seasons, this study proposes some perspectives on the carbonate system functioning of the “future” EMed.

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“…In situ measurements obtained from scientific cruises 103 , 104 revealed that Chl-a concentrations in Rhodes gyre show a seasonal pattern with maximum values during late winter-early spring (0.12–0.47 mg/m 3 ) and minimum during late summer-early autumn (0.05–0.16 mg/m 3 ), which is consistent with our results. A recent study by D’Ortenzio et al 99 , based on Argo-floats, in situ and satellite data, indicated a similar phytoplankton growing period initiating during late November and ending in late April. In early March, a biomass peak was observed (Chl-a 0.6 mg/m 3 ) as indicated by in situ HPLC data, confirming that the phytoplankton increase is affected by mixed layer depth and nutrients dynamics related to winter mixing.…”

Section: Resultsmentioning

confidence: 81%

“…The Rhodes Gyre is a permanent cyclonic gyre in the general circulation of the Levantine Basin in the EMS. 99 , 100 . Despite being situated in the Mediterranean’s most oligotrophic basin, it has relatively high primary productivity, linked to the formation of Levantine Intermediate Water 101 , affecting the distribution of nutrients, the biological activity and the mesozooplankton communities 102 .…”

Section: Resultsmentioning

confidence: 99%

Atlas of phytoplankton phenology indices in selected Eastern Mediterranean marine ecosystems

Kournopoulou,

Kikaki,

Varkitzi

et al. 2024

Sci Rep

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Phytoplankton is a fundamental component of marine food webs and play a crucial role in marine ecosystem functioning. The phenology (timing of growth) of these microscopic algae is an important ecological indicator that can be utilized to observe its seasonal dynamics, and assess its response to environmental perturbations. Ocean colour remote sensing is currently the only means of obtaining synoptic estimates of chlorophyll-a (a proxy of phytoplankton biomass) at high temporal and spatial resolution, enabling the calculation of phenology metrics. However, ocean colour observations have acknowledged weaknesses compromising its reliability, while the scarcity of long-term in situ data has impeded the validation of satellite-derived phenology estimates. To address this issue, we compared one of the longest available in situ time series (20 years) of chlorophyll-a concentrations in the Eastern Mediterranean Sea (EMS), along with concurrent remotely-sensed observations. The comparison revealed a marked coherence between the two datasets, indicating the capability of satellite-based measurements in accurately capturing the phytoplankton seasonality and phenology metrics (i.e., timing of initiation, duration, peak and termination) in the studied area. Furthermore, by studying and validating these metrics we constructed a satellite-derived phytoplankton phenology atlas, reporting in detail the seasonal patterns in several sub-regions in coastal and open seas over the EMS. The open waters host higher concentrations from late October to April, with maximum levels recorded during February and lowest during the summer period. The phytoplankton growth over the Northern Aegean Sea appeared to initiate at least a month later than the rest of the EMS (initiating in late November and terminating in late May). The coastal waters and enclosed gulfs (such as Amvrakikos and Maliakos), exhibit a distinct seasonal pattern with consistently higher levels of chlorophyll-a and prolonged growth period compared to the open seas. The proposed phenology atlas represents a useful resource for monitoring phytoplankton growth periods in the EMS, supporting water quality management practices, while enhancing our current comprehension on the relationships between phytoplankton biomass and higher trophic levels (as a food source).

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BGC‐Argo Floats Observe Nitrate Injection and Spring Phytoplankton Increase in the Surface Layer of Levantine Sea (Eastern Mediterranean)

Abstract: In the Levantine, low-to-very-low values of phytoplankton primary production and chlorophyll-a (CHL) concentration have been obtained from both satellite (Bosc et al., 2004) and in situ (Manca et al., 2004)

Cited by 13 publications

References 58 publications

Optical Properties and Biochemical Indices of Marine Particles in the Open Mediterranean Sea: The R/V Maria S. Merian Cruise, March 2018

Optical Properties and Biochemical Indices of Marine Particles in the Open Mediterranean Sea: The R/V Maria S. Merian Cruise, March 2018

Seasonal and Interannual Variability of the CO2 System in the Eastern Mediterranean Sea: A Case Study in the North Western Levantine Basin

Atlas of phytoplankton phenology indices in selected Eastern Mediterranean marine ecosystems

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