Seasonal variations of biochemical and optical properties, physical dynamics and N stable isotopic composition in three northeastern Mediterranean basins (Aegean, Cretan and Ionian Seas)

Pavlidou, Alexandra; Velaoras, Dimitris; Karageorgis, Aristomenis P.; Rousselaki, Eleni; Parinos, Constantine; Dähnke, Kirstin; Möbius, Jürgen; Meador, Travis B.; Psarra, Stella; Frangoulis, Constantin; Souvermezoglou, Ekaterini; Androni, A.; Assimakopoulou, Georgia; Chaikalis, Spyros; Kanellopoulos, Theodore D.; Lagaria, Anna; Zachioti, P.; Gogou, Alexandra

doi:10.1016/j.dsr2.2019.104704

Cited by 13 publications

(10 citation statements)

References 63 publications

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“…Both attributed the higher δ 15 N-PN values in deep waters to the enrichment of residual 15 N during progressive decay of organic matter, whereas the latter for the first time described a systematic relationship to PN concentrations. In contrast to Pavlidou et al (2020), our EMed data show several (less enriched) outliers in the δ 15 N-PN of deep waters. Together with lower POC/PN ratios, these values imply less degraded organic matter (Figure 8A).…”

Section: Particle Dynamics In the Mediterranean Sea As Inferred From Optical Properties And Biochemical Indicescontrasting

confidence: 87%

“…The striking segregation of relatively depleted δ 15 N-PN in the surface or mixed layer waters and enriched values in deep Mediterranean waters has been also observed by Emeis et al (2010) and Pavlidou et al (2020). Both attributed the higher δ 15 N-PN values in deep waters to the enrichment of residual 15 N during progressive decay of organic matter, whereas the latter for the first time described a systematic relationship to PN concentrations.…”

Section: Particle Dynamics In the Mediterranean Sea As Inferred From Optical Properties And Biochemical Indicesmentioning

confidence: 61%

“…Vertical differences in organic matter quality and quantity are also reflected in lower N concentrations and the increase of the POC/PN ratio in deep waters of all studied sites. Following the approach of Pavlidou et al (2020), we assume a Rayleigh type isotope fractionation discriminating 15 N during the decomposition of sinking and suspended PN (Möbius, 2013). Evidenced by their data, basic assumptions of Pavlidou et al (2020) are: 1) PN distribution in the water column is almost solely driven by vertical transport (sinking) from sea surface to bottom waters and 2) additional sources and sinks of PN are negligible.…”

Section: Particle Dynamics In the Mediterranean Sea As Inferred From Optical Properties And Biochemical Indicesmentioning

confidence: 99%

“…So far, the studies that have been performed on δ 13 C-POC and δ 15 N-PN in the Mediterranean Sea were focused mainly on sinking organic matter (Kerhervé et al, 2001;Çoban-Yildiz et al, 2006;Emeis et al, 2010;Möbius et al, 2010;Pedrosa-Pàmies et al, 2016). To the best of our knowledge, there are only a few studies reporting on the isotopic composition of PN in suspended particles in the Mediterranean Sea (Struck et al, 2001;Pantoja et al, 2002;Çoban-Yildiz et al, 2006;Koppelmann et al, 2009;Emeis et al, 2010;Pavlidou et al, 2020) and none that provide the isotopic composition of POC in suspended particles along the entire water column, from the surface to deep waters, across the open Mediterranean Sea.…”

Section: Introductionmentioning

confidence: 99%

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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: Particle Dynamics In the Mediterranean Sea As Inferred From Optical Properties And Biochemical Indicescontrasting

confidence: 87%

Section: Particle Dynamics In the Mediterranean Sea As Inferred From Optical Properties And Biochemical Indicesmentioning

confidence: 61%

Section: Particle Dynamics In the Mediterranean Sea As Inferred From Optical Properties And Biochemical Indicesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…It exhibits ultra-oligotrophic characteristics, related to: 1) a net outflow of nutrients due to its anti-estuarine circulation, 2) nutrient-depleted surface Atlantic Water flowing in through the Strait of Sicily and nutrient-rich Levantine Intermediate Water flowing out at intermediate depths (Ribera d'Alcalà, 2003;Huertas et al, 2012), and 3) extremely low phosphorus levels, which strongly limits both primary and secondary productions (Krom et al, 1991). Carbon vertical flux was found to be differentiated along a north-south oligotrophy gradient and "hot spots" for CO 2 sequestration to the ocean interior on long time scales were detected in the less oligotrophic area (Siokou-Frangou et al, 2002;Gogou et al, 2014;Pedrosa-Pàmies et al, 2016;Pavlidou et al, 2020). The weak seasonality of the phytoplankton biomass and production drives NPP rates below 200 mg C m −2 d −1 (Psarra et al, 2000;Moutin and Raimbault, 2002;Bosc, 2004), while very low amounts of POC (<0.5% of NPP) reach the deep sea floor (Warnken, 2003;Koppelmann et al, 2004;Stavrakakis et al, 2013;Gogou et al, 2014;Pedrosa-Pàmies et al, 2016;Karageorgis et al, 2018).…”

Section: Introductionmentioning

confidence: 98%

Atmospheric and Oceanographic Forcing Impact Particle Flux Composition and Carbon Sequestration in the Eastern Mediterranean Sea: A Three-Year Time-Series Study in the Deep Ierapetra Basin

et al. 2021

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Sinking particles are a critical conduit for the export of organic material from surface waters to the deep ocean. Despite their importance in oceanic carbon cycling, little is known about the biotic composition and seasonal variability of sinking particles reaching abyssal depths. Herein, sinking particle flux data, collected in the deep Ierapetra Basin for a three-year period (June 2010 to June 2013), have been examined at the light of atmospheric and oceanographic parameters and main mass components (lithogenic, opal, carbonates, nitrogen, and organic carbon), stable isotopes of particulate organic carbon (POC) and source-specific lipid biomarkers. Our aim is to improve the current understanding of the dynamics of particle fluxes and the linkages between atmospheric dynamics and ocean biogeochemistry shaping the export of organic matter in the deep Eastern Mediterranean Sea. Overall, particle fluxes showed seasonality and interannual variability over the studied period. POC fluxes peaked in spring April–May 2012 (12.2 mg m−2 d−1) related with extreme atmospheric forcing. Summer export was approximately fourfold higher than mean wintertime, fall and springtime (except for the episodic event of spring 2012), fueling efficient organic carbon sequestration. Lipid biomarkers indicate a high relative contribution of natural and anthropogenic, marine- and land-derived POC during both spring (April–May) and summer (June–July) reaching the deep-sea floor. Moreover, our results highlight that both seasonal and episodic pulses are crucial for POC export, while the coupling of extreme weather events and atmospheric deposition can trigger the influx of both marine labile carbon and anthropogenic compounds to the deep Levantine Sea. Finally, the comparison of time series data of sinking particulate flux with the corresponding biogeochemical parameters data previously reported for surface sediment samples from the deep-sea shed light on the benthic–pelagic coupling in the study area. Thus, this study underscores that accounting the seasonal and episodic pulses of organic carbon into the deep sea is critical in modeling the depth and intensity of natural and anthropogenic POC sequestration, and for a better understanding of the global carbon cycle.

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The Physical Characteristics and Dynamics of the Aegean Water Masses

Velaoras

Zervakis

Theocharis

2021

The Handbook of Environmental Chemistry

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Seasonal variations of biochemical and optical properties, physical dynamics and N stable isotopic composition in three northeastern Mediterranean basins (Aegean, Cretan and Ionian Seas)

Cited by 13 publications

References 63 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

Atmospheric and Oceanographic Forcing Impact Particle Flux Composition and Carbon Sequestration in the Eastern Mediterranean Sea: A Three-Year Time-Series Study in the Deep Ierapetra Basin

The Physical Characteristics and Dynamics of the Aegean Water Masses

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