scholarly journals Deep maxima of phytoplankton biomass, primary production and bacterial production in the Mediterranean Sea during late spring

2020 ◽  
Author(s):  
Emilio Marañón ◽  
France Van Wambeke ◽  
Julia Uitz ◽  
Emmanuel S. Boss ◽  
María Pérez-Lorenzo ◽  
...  
Keyword(s):  
Primary Production ◽  
Mediterranean Sea ◽  
Chlorophyll A ◽  
Phytoplankton Biomass ◽  
Specific Productivity ◽  
Relative Role ◽  
Central Mediterranean ◽  
Euphotic Layer ◽  
Carbon Biomass ◽  
The Mediterranean

Abstract. The deep chlorophyll maximum (DCM) is a ubiquitous feature of phytoplankton vertical distribution in stratified waters that is relevant for our understanding of the mechanisms that underpin the variability in photoautotroph ecophysiology across environmental gradients and has implications for remote sensing of aquatic productivity. During the PEACETIME (Process studies at the air-sea interface after dust deposition in the Mediterranean Sea) cruise, carried out from 10 May to 11 June 2017, we obtained 23 concurrent vertical profiles of phytoplankton chlorophyll a, carbon biomass and primary production, as well as heterotrophic prokaryotic production, in the western and central Mediterranean basins. Our main aims were to quantify the relative role of photoacclimation and enhanced growth as underlying mechanisms of the DCM and to assess the trophic coupling between phytoplankton and heterotrophic prokaryotic production. We found that the DCM coincided with a maximum in both biomass and primary production but not in growth rate of phytoplankton, which averaged 0.3 d−1 and was relatively constant across the euphotic layer. Photoacclimation explained most of the increased chlorophyll a at the DCM, as the carbon to chlorophyll a ratio (C:Chl a) decreased from ca. 90–100 (g:g) at the surface to 20–30 at the base of the euphotic layer, while phytoplankton carbon biomass increased from ca. 6 mgC m−3 at the surface to 10–15 mgC m−3 at the DCM. As a result of photoacclimation, there was an uncoupling between chlorophyll a-specific and carbon-specific productivity across the euphotic layer. The fucoxanthin to total chlorophyll a ratio increased markedly with depth, as did the biomass contribution of large cells, suggesting a dominance of diatoms at the DCM. The increased biomass and carbon fixation at the base of the euphotic zone was associated with enhanced rates of heterotrophic prokaryotic activity, which also showed a surface peak linked with warmer temperatures. Considering the phytoplankton biomass and turnover rates measured at the DCM, nutrient diffusive fluxes across the nutricline were able to supply only a minor fraction of the photoautotroph nitrogen and phosphorus requirements. Thus the deep maxima in biomass and primary production were not fueled by new nutrients, but likely resulted from cell sinking from the upper layers in combination with the high photosynthetic efficiency of a diatom-rich, low-light acclimated community largely sustained by regenerated nutrients. Further studies with increased temporal and spatial resolution will be required to ascertain if the deep primary production peaks associated with the DCM persist across the western and central Mediterranean Sea throughout the stratification season.

scholarly journals Deep maxima of phytoplankton biomass, primary production and bacterial production in the Mediterranean Sea

2021 ◽  
Vol 18 (5) ◽  
pp. 1749-1767 ◽  
Author(s):  
Emilio Marañón ◽  
France Van Wambeke ◽  
Julia Uitz ◽  
Emmanuel S. Boss ◽  
Céline Dimier ◽  
...  
Keyword(s):  
Primary Production ◽  
Mediterranean Sea ◽  
Chlorophyll A ◽  
Phytoplankton Biomass ◽  
Specific Productivity ◽  
Relative Role ◽  
Central Mediterranean ◽  
Euphotic Layer ◽  
Carbon Biomass ◽  
The Mediterranean

Abstract. The deep chlorophyll maximum (DCM) is a ubiquitous feature of phytoplankton vertical distribution in stratified waters that is relevant to our understanding of the mechanisms that underpin the variability in photoautotroph ecophysiology across environmental gradients and has implications for remote sensing of aquatic productivity. During the PEACETIME (Process studies at the air-sea interface after dust deposition in the Mediterranean Sea) cruise, carried out from 10 May to 11 June 2017, we obtained 23 concurrent vertical profiles of phytoplankton chlorophyll a, carbon biomass and primary production, as well as heterotrophic prokaryotic production, in the western and central Mediterranean basins. Our main aims were to quantify the relative role of photoacclimation and enhanced growth as underlying mechanisms of the DCM and to assess the trophic coupling between phytoplankton and heterotrophic prokaryotic production. We found that the DCM coincided with a maximum in both the biomass and primary production but not in the growth rate of phytoplankton, which averaged 0.3 d−1 and was relatively constant across the euphotic layer. Photoacclimation explained most of the increased chlorophyll a at the DCM, as the ratio of carbon to chlorophyll a (C:Chl a) decreased from ca. 90–100 (g:g) at the surface to 20–30 at the base of the euphotic layer, while phytoplankton carbon biomass increased from ca. 6 mg C m−3 at the surface to 10–15 mg C m−3 at the DCM. As a result of photoacclimation, there was an uncoupling between chlorophyll a-specific and carbon-specific productivity across the euphotic layer. The ratio of fucoxanthin to total chlorophyll a increased markedly with depth, suggesting an increased contribution of diatoms at the DCM. The increased biomass and carbon fixation at the base of the euphotic zone was associated with enhanced rates of heterotrophic prokaryotic activity, which also showed a surface peak linked with warmer temperatures. Considering the phytoplankton biomass and turnover rates measured at the DCM, nutrient diffusive fluxes across the nutricline were able to supply only a minor fraction of the photoautotroph nitrogen and phosphorus requirements. Thus the deep maxima in biomass and primary production were not fuelled by new nutrients but likely resulted from cell sinking from the upper layers in combination with the high photosynthetic efficiency of a diatom-rich, low-light acclimated community largely sustained by regenerated nutrients. Further studies with increased temporal and spatial resolution will be required to ascertain if the peaks of deep primary production associated with the DCM persist across the western and central Mediterranean Sea throughout the stratification season.

scholarly journals Dissolved and particulate primary production along a longitudinal gradient in the Mediterranean Sea

2011 ◽  
Vol 8 (3) ◽  
pp. 815-825 ◽  
Author(s):  
D. C. López-Sandoval ◽  
A. Fernández ◽  
E. Marañón
Keyword(s):  
Primary Production ◽  
Mediterranean Sea ◽  
Small Degree ◽  
Euphotic Layer ◽  
Relative Contribution ◽  
Carbon Demand ◽  
Extracellular Release ◽  
Photosynthetic Production ◽  
Longitudinal Pattern ◽  
The Mediterranean

Abstract. We have determined the photosynthetic production of dissolved (DOCp) and particulate organic carbon (POCp) along a longitudinal transect in the Mediterranean Sea during the summer stratification period. The euphotic layer-integrated rates of DOCp and POCp ranged between approximately 50–130 and 95–210 mgC m−2 d−1, respectively, and showed an east to west increasing trend. For the whole transect, the relative contribution of DOCp to total, euphotic layer-integrated primary production (percentage of extracellular release, PER) averaged ~37% and did not show any clear longitudinal pattern. In spite of the relatively high PER values, the measured DOCp rates were much lower than the estimated bacterial carbon demand, suggesting a small degree of coupling between phytoplankton exudation and bacterial metabolism. Our results, when compared with previous measurements obtained with the same methods in several ecosystems of contrasting productivity, support the view that the relative importance of DOCp increases under strong nutrient limitation.

scholarly journals Dissolved and particulate primary production along a longitudinal gradient in the Mediterranean Sea

2010 ◽  
Vol 7 (6) ◽  
pp. 8591-8617 ◽  
Author(s):  
D. C. López-Sandoval ◽  
A. Fernández ◽  
E. Marañón
Keyword(s):  
Primary Production ◽  
Mediterranean Sea ◽  
Small Degree ◽  
Euphotic Layer ◽  
Relative Contribution ◽  
Carbon Demand ◽  
Extracellular Release ◽  
Photosynthetic Production ◽  
Longitudinal Pattern ◽  
The Mediterranean

Abstract. We have determined the photosynthetic production of dissolved (DOCp) and particulate organic carbon (POCp) along a longitudinal transect in the Mediterranean Sea during the summer stratification period. The euphotic layer-integrated rates of DOCp and POCp ranged between approximately 50–130 and 95–210 mgC m−2 d−1, respectively, and showed an east to west increasing trend. For the whole transect, the relative contribution of DOCp to total, euphotic layer-integrated primary production (percentage of extracellular release, PER) averaged ~37% and did not show any clear longitudinal pattern. In spite of the relatively high PER values, the measured DOCp rates were much lower than the estimated bacterial carbon demand, suggesting a small degree of coupling between phytoplankton exudation and bacterial metbolism. Our results, when compared with previous measurements obtained with the same methods in several ecosystems of contrasting productivity, support the view that the relative importance of DOCp increases under strong nutrient limitation.

In Vivo Fluorescence of Chlorophyll A: Estimation of Phytoplankton Biomass and Activity in Římov Reservoir (Czech Republic)

1993 ◽  
Vol 28 (6) ◽  
pp. 29-33 ◽  
Author(s):  
V. Vyhnálek ◽  
Z. Fišar ◽  
A. Fišarová ◽  
J. Komárková
Keyword(s):  
Czech Republic ◽  
Chlorophyll Fluorescence ◽  
Primary Production ◽  
Chlorophyll A ◽  
Phytoplankton Biomass ◽  
In Vivo Fluorescence ◽  
Fluorescence Of Chlorophyll A ◽  
Římov Reservoir ◽  
Natural Phytoplankton

The in vivo fluorescence of chlorophyll a was measured in samples of natural phytoplankton taken from the Římov Reservoir (Czech Republic) during the years 1987 and 1988. The fluorescence intensities of samples either with or without addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron, DCMU) were found reliable for calculating the concentration of chlorophyll a during periods when cyanobacteria were not abundant. The correction for background non-chlorophyll fluorescence appeared to be essential. No distinct correlation between a DCMU-induced increase of the fluorescence and primary production of phytoplankton was found.

scholarly journals Primary marine aerosol emissions from the Mediterranean Sea during pre-bloom and oligotrophic conditions: correlations to seawater chlorophyll <i>a</i> from a mesocosm study

2015 ◽  
Vol 15 (14) ◽  
pp. 7961-7976 ◽  
Author(s):  
A. N. Schwier ◽  
C. Rose ◽  
E. Asmi ◽  
A. M. Ebling ◽  
W. M. Landing ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Size Distribution ◽  
Chlorophyll A ◽  
Aerosol Size Distribution ◽  
Marine Aerosol ◽  
Organic Fraction ◽  
Condensation Nuclei ◽  
Bloom Period ◽  
The Mediterranean ◽  
Aerosol Emissions

Abstract. The effect of ocean acidification and changing water conditions on primary (and secondary) marine aerosol emissions is not well understood on a regional or a global scale. To investigate this effect as well as the indirect effect on aerosol that changing biogeochemical parameters can have, ~ 52 m3 pelagic mesocosms were deployed for several weeks in the Mediterranean Sea during both winter pre-bloom and summer oligotrophic conditions and were subjected to various levels of CO2 to simulate the conditions foreseen in this region for the coming decades. After seawater sampling, primary bubble-bursting aerosol experiments were performed using a plunging water jet system to test both chemical and physical aerosol parameters (10–400 nm). Comparing results obtained during pre-bloom and oligotrophic conditions, we find the same four log-normal modal diameters (18.5 ± 0.6, 37.5 ± 1.4, 91.5 ± 2.0, 260 ± 3.2 nm) describing the aerosol size distribution during both campaigns, yet pre-bloom conditions significantly increased the number fraction of the second (Aitken) mode, with an amplitude correlated to virus-like particles, heterotrophic prokaryotes, TEPs (transparent exopolymeric particles), chlorophyll a and other pigments. Organic fractions determined from kappa closure calculations for the diameter, Dp ~ 50 nm, were much larger during the pre-bloom period (64 %) than during the oligotrophic period (38 %), and the organic fraction decreased as the particle size increased. Combining data from both campaigns together, strong positive correlations were found between the organic fraction of the aerosol and chlorophyll a concentrations, heterotrophic and autotrophic bacteria abundance, and dissolved organic carbon (DOC) concentrations. As a consequence of the changes in the organic fraction and the size distributions between pre-bloom and oligotrophic periods, we find that the ratio of cloud condensation nuclei (CCN) to condensation nuclei (CN) slightly decreased during the pre-bloom period. The enrichment of the seawater samples with microlayer samples did not have any effect on the size distribution, organic content or the CCN activity of the generated primary aerosol. Partial pressure of CO2, pCO2, perturbations had little effect on the physical or chemical parameters of the aerosol emissions, with larger effects observed due to the differences between a pre-bloom and oligotrophic environment.

Erosional landforms and biological structures in tectonically stable areas in the Mediterranean basin

2021 ◽  
Author(s):  
Valeria Vaccher ◽  
Stefano Furlani ◽  
Sara Biolchi ◽  
Chiara Boccali ◽  
Alice Busetti ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Sea Level ◽  
Mediterranean Basin ◽  
Vertical Position ◽  
Structural Constraints ◽  
Last Interglacial ◽  
Central Mediterranean ◽  
Biological Structures ◽  
The Mediterranean ◽  
The Mediterranean Basin

&lt;p&gt;The Mediterranean basin displays a variety of neotectonics scenarios leading to positive or negative vertical displacement, which change the vertical position of former coastlines. As a result, the best locations to evaluate former sea levels and validate sea-level models are tectonically stable areas. There are a number of coastal areas considered to be stable based on the elevation of paleo sea-level markers, the absence of historical seismicity, and by their position far from major Mediterranean faults. We report here the results of swim surveys carried out at such locations following the Geoswim approach described by Furlani (2020) in nine coastal sectors of the central Mediterranean Sea (Egadi Island - Marettimo, Favignana, Levanzo, Gaeta Promontory, Circeo Promontory, North Sardinia - Razzoli, Budelli, Santa Maria, NW Sardinia &amp;#8211; Capocaccia, Maddalena Archipelago, Tavolara Island, East of Malta - Ahrax Point, Bugibba-Qawra, Delimara, Addura, Palermo, Ansedonia Promontory). All the sites are considered to be tectonically stable, as validated by the elevation of sea-level indicators. In fact, modern and MIS5.5 (last interglacial) m.s.l. altitudes fit well with accepted figures based upon field data and model projections. Starting from precise morphometric parameters such as the size of tidal notches and indicative landforms and biological structures, we have developed a procedure that integrates multiple geomorphological and biological descriptors applicable to the vast spectrum of locally diverse coastal situations occurring in the Mediterranean Sea. We took detailed measurements of features such as modern and MIS5.5 tidal notches at 146 sites in all the areas, the absence of modern tidal notch at Circeo promontory, shore platforms, and MIS5.5 marine terraces at Egadi islands, Malta, and Palermo. Biological structures were also measured. In particular, vermetid platforms at Egadi, Palermo and Malta. The morphometric characteristics of these indicators depend on 1) local geological and structural constraints, 2) local geomorphotypes, 3) climate, sea, and weather conditions that affect geomorphic and biological processes, and 4) the sea level change history.&lt;/p&gt;

Relationships of Phytoplankton Biomass with Soluble Nutrients, Primary Production, and Chlorophyll a in Lake Erie, 1970

1976 ◽  
Vol 33 (3) ◽  
pp. 601-611 ◽  
Author(s):  
M. Munawar ◽  
N. M. Burns
Keyword(s):  
Primary Production ◽  
Chlorophyll A ◽  
Phytoplankton Biomass ◽  
Lake Erie ◽  
Soluble Reactive Phosphorus ◽  
Distribution Patterns ◽  
Statistical Procedure ◽  
Annual Average ◽  
Average Distribution ◽  
Reactive Phosphorus

Comparison of the annual average distribution patterns of phytoplankton biomass, chlorophyll a, primary production, soluble reactive phosphorus, nitrate + nitrite, and ammonia concentrations revealed that these six variables had very similar distributions in Lake Erie during 1970. However, statistical analysis of the data only revealed a few consistent relationships between these variables. The phytoplankton biomass was correlated with chlorophyll a only in the summer and fall as was primary production with chlorophyll a and biomass. There was no correlation between these three variables during the spring. Also, there was no consistent relationship between biomass and soluble nutrients. The primary production and activity coefficient (mg Cassimilated per milligram phytoplankton biomass per day) were found to be unrelated to temperature. The statistical procedure of factor analysis showed that in the spring, primary production correlated with the phosphorus and nitrogen soluble nutrients only, whereas during summer, primary production correlated with biomass, chlorophyll a, the major plankton groups (Cyanophyta, Chlorophyta, Chrysomonadinae, and Diatomeae), and the phosphorus nutrients. In the fall, production was positively correlated with phytoplankton biomass and with the Chlorophyta in particular. The use of chlorophyll a and temperature as variables in the equation to estimate phytoplankton growth in Lake Erie was found to be questionable.

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