scholarly journals Major contribution of prokaryotes to carbon fluxes in the pelagic microbial food webs of the Mediterranean Sea

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Luca Zoccarato ◽  
Anna Malusà ◽  
Serena Fonda Umani
Keyword(s):  
Food Web ◽  
Mediterranean Sea ◽  
Trophic Levels ◽  
Trophic Conditions ◽  
Major Pathway ◽  
Carbon Transfer ◽  
Wide Range ◽  
Autotrophic Biomass ◽  
Heterotrophic Prokaryotes ◽  
The Mediterranean

<p>In this study, we carried out dilution experiments at the surface and in the mesopelagic and bathypelagic layers at 15 sites in the Mediterranean Sea that covered a wide range of trophic conditions. The main aim was to test the hypothesis that prokaryotes, and particularly heterotrophic prokaryotes, are pivotal in sustaining both nanoplankton and microzooplankton energy requirements at all of the considered trophic states. These data highlight that bacterivory is the major pathway of organic carbon transfer in the oligotrophic and meso-eutrophic environments. The microzooplankton mostly feed on prokaryotes, directly or indirectly (through nanoplankton exploitation), rather than on microalgae. Under eutrophic conditions, herbivory is the main trophic pathway; however, the heterotrophic prokaryotes always represent an important source of carbon. The lowest food-web efficiency <em>(i.e</em>., ratio between productivity of the highest trophic level and productivity of the lower trophic levels) was determined for the eutrophic status due to possible grazer satiation, which translates into an excess of autotrophic biomass available for export or transfer to higher trophic levels. The food-web efficiency is higher under mesoeutrophic and oligotrophic conditions, where the main pathway is bacterivory. In the mesopelagic and bathypelagic layers, only nanoplankton predation on heterotrophic prokaryotes was investigated. The food-web efficiency in these layers was relatively high and nanoplankton appear to efficiently exploit the available biomass of heterotrophic prokaryotes.</p>

scholarly journals Plankton in the open Mediterranean Sea: a review

2009 ◽  
Vol 6 (6) ◽  
pp. 11187-11292 ◽  
Author(s):  
I. Siokou-Frangou ◽  
U. Christaki ◽  
M. G. Mazzocchi ◽  
M. Montresor ◽  
M. Ribera d'Alcalá ◽  
...  
Keyword(s):  
Food Web ◽  
Mediterranean Sea ◽  
Deep Convection ◽  
Trophic Levels ◽  
Grazing Impact ◽  
Late Winter ◽  
Amazon Forest ◽  
Chl A ◽  
Spatial And Temporal Scales ◽  
The Mediterranean

Abstract. We present an overview of the plankton studies conducted during the last 25 years in the epipelagic offshore waters of the Mediterranean Sea. This quasi-enclosed sea is characterized by a rich and complex physical dynamics that includes unique thermohaline features, particular multilayer circulation, topographic gyres, and meso- and sub-mesoscale activity. Recent investigations have basically confirmed the long-recognised oligotrophic character of this sea, which enhances along both the west-east, and the north-south directions. Nutrient availability is low, especially for phosphorous (N:P up to 60), although limitation may be relaxed by inputs from highly populated coasts and from the atmosphere. Phytoplankton biomass as chl-a, generally displays low values (less than 0.2 μg chl-a l-1) over large areas, with a modest late winter increase. A large bloom (up to 3 μg l-1) throughout the late winter and early spring is only observed in the NW area. Relatively high biomass peaks are also recorded in fronts and cyclonic gyres. A deep chlorophyll maximum is a~permanent feature for the whole basin (except during the late winter mixing). It progressively deepens from the Alboran Sea (30 m) to the easternmost Levantine basin (120 m). Primary production reveals a similar west-east decreasing trend and ranges from 59 to 150 g C m-2 y-1 (in situ measurements). Overall the basin is largely dominated by small-sized autotrophs, microheterotrophs and egg-carrying copepod species. The phytoplankton, the microbial (both autotrophic and heterotrophic) and the zooplankton components reveal a considerable diversity and variability over spatial and temporal scales, the latter less explored though. Examples are the wide diversity of dinoflagellates and coccolithophores, the multifarious role of diatoms or picoeukaryotes, and the distinct seasonal or spatial patterns of the species-reach copepod genera or families which dominate in the basin. Major dissimilarities between western and eastern basins have been highlighted in species composition of phytoplankton and mesozooplankton, but also in the microbial components and in their relationships. Superimposed to these longitudinal differences, a pronounced biological heterogeneity is also observed in areas hosting deep convection, fronts, cyclonic and anti-cyclonic gyres or eddies. There, the intermittent nutrient enrichment promotes switches from a small-sized microbial community to diatom-dominated populations. A classical food web is ready to substitute the microbial food web in these cases. These switches, likely occurring within a continuum of trophic pathways, may greatly enhance the flux towards high trophic levels, in spite of an apparent heterotrophy. Basically, the system seems to be top-down controlled and characterised by a ‘multivorous web’, as shown by the great variety of feeding modes and preferences and by the significant and simultaneous grazing impact on phytoplankton and ciliates by mesozooplankton. ‘La Mediterrània, o almenys la seva zona pelàgica, seria comparable a una Amazònia marina.’ (Margalef, 1995) (The Mediterranean, or at least its pelagic zone, would be like a marine version of the Amazon forest.)

scholarly journals Anchovy (Engraulis encrasicolus) otoliths reveal growth differences between two areas of the Spanish Mediterranean Sea

2017 ◽  
Vol 81 (3) ◽  
pp. 327 ◽  
Author(s):  
Ana Ventero ◽  
Magdalena Iglesias ◽  
Begoña Villamor
Keyword(s):  
Food Web ◽  
Mediterranean Sea ◽  
Essential Element ◽  
Trophic Levels ◽  
Ebro Delta ◽  
Alboran Sea ◽  
Pelagic Food Web ◽  
The Mediterranean ◽  
Growth Differences ◽  
Alborán Sea

Anchovy is a commercial species that supports large fisheries in the Mediterranean Sea. In addition, anchovy is an essential element of the pelagic food web, playing a considerable role in connecting the lower and upper trophic levels. Comparisons made regarding length frequency distribution, demographic structure, growth during the first year inferred from otoliths, and the condition factor of anchovy inhabiting the Spanish Mediterranean Sea (General Fisheries Commission for the Mediterranean management units, GSA06-Ebro Delta and 01-Alboran Sea), based on five-year data, clearly showed significant growth differences between areas and evidenced the existence of two independent anchovy stocks in the Spanish Mediterranean Sea. The anchovies inhabiting the Alboran Sea had higher growth than the anchovies inhabiting the Ebro Delta for the same age (one year old). The dramatic decline of the Alboran Sea anchovy could be related to the current management legislation in the Spanish Mediterranean Sea, based mainly on a common minimum catch size (9 cm), which should be revised given that sustainable anchovy exploitation is crucial for the pelagic food web equilibrium.

scholarly journals Perfuorooctane Sulfonate (PFOS), Perfluorooctanoic Acid (PFOA), Brominated Dioxins (PBDDs) and Furans (PBDFs) in Wild and Farmed Organisms at Different Trophic Levels in the Mediterranean Sea

Toxics ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 50 ◽  
Author(s):  
Elena Fattore ◽  
Renzo Bagnati ◽  
Andrea Colombo ◽  
Roberto Fanelli ◽  
Roberto Miniero ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Limit Of Detection ◽  
Perfluorooctanoic Acid ◽  
Trophic Levels ◽  
Sea Bream ◽  
Farmed Fish ◽  
European Sea Bass ◽  
Marine Aquaculture ◽  
Fishery Products ◽  
The Mediterranean

The present study shows the results of perfuorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), brominated dioxins (PBDDs) and furans (PBDFs) measured in several marine fish and seafood of commercial interest at different trophic levels of the food chain. The aims were to investigate the level of the contamination in Mediterranean aquatic wildlife, and in farmed fish, to assess human exposure associated to fishery products consumption. Samples of wild fish were collected during three different sampling campaigns in different Food and Agriculture Organization (FAO) 37 areas of the Mediterranean Sea. In addition, farmed fish (gilthead sea bream and European sea bass) from off-shore cages from different marine aquaculture plants. Results showed contamination values of PFOS and PFOA were lower than those detected in sea basins other than the Mediterranean Sea. Concentration values of PFOS were generally higher than those of PFOA; moreover, levels in farmed fish were lower than in wild samples from the Mediterranean Sea. Intake of PFOS and PFOA through fishery products consumption was estimated to be 2.12 and 0.24 ng/kg·BW·day, respectively, for high consumers (95th percentile). Results of 2,3,7,8-substituted congeners of PBDDs and PBDFs were almost all below the limit of detection (LOD), making it difficult to establish the contribution of these compounds to the total contamination of dioxin-like compounds in fish and fishery products.

scholarly journals Mesoscale variations in the assemblage structure and trophodynamics of mesozooplankton communities of the Adriatic basin (Mediterranean Sea)

2021 ◽  
Author(s):  
Emanuela Fanelli ◽  
Samuele Menicucci ◽  
Sara Malavolti ◽  
Andrea De Felice ◽  
Iole Leonori
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Mediterranean Sea ◽  
Environmental Variables ◽  
Complex Structure ◽  
Assemblage Structure ◽  
Trophic Levels ◽  
Ecosystem Functions ◽  
Food Web Structure ◽  
Adriatic Basin

Abstract. Zooplankton are critical to the functioning of ocean food webs because of their utter abundance and vital ecosystem roles. Zooplankton communities are highly diverse and thus perform a variety of ecosystem functions, thus changes in their community or food web structure may provide evidence of ecosystem alteration. Assemblage structure and trophodynamics of mesozooplantkon communities were examined across the Adriatic basin, the northernmost and most productive basin of the Mediterranean Sea. Samples were collected in June–July 2019 along coast-offshore transects covering the whole western Adriatic side, consistently environmental variables were also recorded. Results showed a clear separation between samples from the northern-central Adriatic and the southern ones, with a further segregation, although less clear, of inshore vs. off-shore stations, the latter mostly dominated in the central and southern stations by gelatinous plankton. Such patterns were mainly driven by chlorophyll-a concentration (as a proxy of primary production) for northern-central stations, i.e. closer to the Po river input, and by temperature and salinity, for southern ones, with the DistLM model explaining 46 % of total variance. The analysis of stable isotopes of nitrogen and carbon allowed to identify a complex food web characterized by 3 trophic levels from herbivores to carnivores, passing through the mixed feeding behavior of omnivores, shifting from phytoplankton/detritus ingestion to microzooplankton. Trophic structure also spatially varied according to sub-area, with the northern-central sub-areas differing from each other and from the southern stations. Our results highlighted the importance of environmental variables as drivers of zooplanktonic communities and the complex structure of their food webs. Disentangling and considering such complexity is crucial to generate realistic predictions on the functioning of aquatic ecosystems, especially in high productive and, at the same time, overexploited area such as the Adriatic Sea.

scholarly journals Multivariate Sub-Regional Ocean Indicators in the Mediterranean Sea: From Event Detection to Climate Change Estimations

2021 ◽  
Vol 8 ◽  
Author(s):  
Mélanie Juza ◽  
Joaquín Tintoré
Keyword(s):  
Climate Change ◽  
Mediterranean Sea ◽  
Ocean Circulation ◽  
Heat Waves ◽  
Mesoscale Eddy ◽  
Value Added ◽  
Policy Decision ◽  
Balearic Islands ◽  
Wide Range ◽  
The Mediterranean

The increasing science and society requests for ocean monitoring from global to regional and local scales, the need for integration and convergence into a globally consistent ocean observing system as well as the need for improvement of access to information are now internationally recognized goals to progress toward the sustainable management of a healthy ocean. To respond to these challenges at regional level, the Balearic Islands Coastal Observing and Forecasting System (SOCIB) is developing a comprehensive set of ocean indicators in the Mediterranean Sea and around the Balearic Islands, key environments that are strongly affected by climate change and human pressure. This new SOCIB value-added product addresses the sub-regional ocean variability from daily (events) to interannual/decadal (climate) scales. A user-friendly interface has been implemented to monitor, visualize and communicate ocean information that is relevant for a wide range of sectors, applications and regional end-users. These sub-regional indicators allowed us to detect specific events in real time. Remarkable events and features identified include marine heat waves, atmospheric storm, extreme river discharge, mesoscale eddy, deep convection among others, all of them being oceanic phenomena that directly impact the ocean circulation and marine ecosystems. The long-term variations, in response to climate change, are also addressed highlighting and quantifying trends in physical and biogeochemical components of the ocean as well as sub-regional differences. At both (sub-) regional, national and international levels, a society-aligned science will have stronger impact on policy decision-makings and will support society to implement specific actions to address worldwide environmental challenges.

Impacts of macrozoobenthic invasions on a temperate coastal food web

2020 ◽  
Vol 653 ◽  
pp. 19-39
Author(s):  
AS Jung ◽  
HW van der Veer ◽  
CJM Philippart ◽  
AM Waser ◽  
BJ Ens ◽  
...  
Keyword(s):  
Food Web ◽  
Native Species ◽  
Wadden Sea ◽  
Marine Species ◽  
Trophic Levels ◽  
Food Web Structure ◽  
Total Consumption ◽  
Predator Prey ◽  
Carbon Transfer ◽  
The Impact

Invasions of marine species are changing coastal food webs worldwide, impacting on trophic interactions between native species (e.g. predator-prey relationships). Here, the impact of 3 macrozoobenthic invasive species on food web structure and functioning at Balgzand (western Wadden Sea) is quantified by using ecological network analysis (ENA). The bivalves Ensis leei and Magallana gigas were observed for the first time in 1984 and 2001, respectively, and the polychaete Marenzelleria viridis appeared in 1989. Although E. leei and M. viridis reached similar peak biomasses in the 2000s (ca. 1700 and 2000 mg C m-2, respectively), the bivalve consumption was higher (>45% of total consumption) than that of the polychaete (<10%). Biomass and impact of M. gigas remained relatively low. E. leei occupied an ecological niche that was relatively unoccupied, which led to competitive advantage with respect to other suspension feeders. Increasing biomass of E. leei coincided with a 70% increase of trophic carbon transfer from primary to secondary producers and an 80% increase from secondary producers to detritus. Carbon flows from secondary producers to higher trophic levels were reduced by more than 60%. These shifts in trophic transfer were stronger than those observed during the invasion of M. gigas in the NE Wadden Sea. At Balgzand, biomass of M. gigas and M. viridis rapidly declined to low values in the 2010s, implying a temporally limited impact. In the 2010s, E. leei was still responsible for 30% of the total consumption in the 2010s, indicating a longer-term impact.

scholarly journals Distribution and host diversity of Amoebophryidae parasites across oligotrophic waters of the Mediterranean Sea

2011 ◽  
Vol 8 (2) ◽  
pp. 267-278 ◽  
Author(s):  
R. Siano ◽  
C. Alves-de-Souza ◽  
E. Foulon ◽  
El M. Bendif ◽  
N. Simon ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Marine Ecosystems ◽  
Natural Environments ◽  
Coastal Station ◽  
Host Diversity ◽  
Eukaryotic Community ◽  
Wide Range ◽  
The Mediterranean ◽  
Host Infection

Abstract. Sequences affiliated to Syndiniales (Marine alveolate, MALV) regularly dominate 18S rDNA genetic libraries of nearly all marine ecosystems investigated so far. Among them, Amoebophryidae (MALV group II) is composed of numerous and genetically distant environmental sequences, where Amoebophrya is the only known and formally described genus. Amoebophrya species include virulent pathogens for a wide range of dinoflagellate species. Beside their regular occurrence in marine ecosystems, their quantitative distribution and the environmental factors triggering host infection have barely been studied in open oligotrophic waters. In order to understand the functional role of these parasites in natural environments, we studied the distribution and contribution to the eukaryotic community of the small free-living stage of Amoebophryidae (the dinospores) along a transect in the Mediterranean Sea, as well as their host diversity at three oligotrophic stations. Dinospores were more abundant at a coastal station (max. 1.5 × 103 cells ml−1) than in oligotrophic waters (max. 51 ± 16.3 cells ml−1), where they represented 10.3 to 34.9% of the total eukaryotic community at 40 and 30 m depth, respectively and 21.2% on average along the water column. Positive correlation was found between dinospore occurrence and higher concentration of NO3 + NO2 at the coastal station. At selected stations, out of 38 different dinoflagellates taxa identified, 15 were infected, among which a majority were not recognized as Amoebophryidae host so far. Prevalences (percentage of infected cells) generally varied between 1% and 10%, with a notable exception for Blepharocysta paulsenii for which 25% of cells were infected at the most oligotrophic station. The present study shows that dinospores are able to thrive and infect dinoflagellates both in coastal and ultra-oligotrophic open waters. Our results emphasize the role of parasitism in microbial food web dynamics and ultimately on biogeochemical cycles.

scholarly journals Development of BFMCOUPLER (v1.0), the coupling scheme that links the MITgcm and BFM models for ocean biogeochemistry simulations

2017 ◽  
Vol 10 (4) ◽  
pp. 1423-1445 ◽  
Author(s):  
Gianpiero Cossarini ◽  
Stefano Querin ◽  
Cosimo Solidoro ◽  
Gianmaria Sannino ◽  
Paolo Lazzari ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Biogeochemical Model ◽  
Coupling Scheme ◽  
Integration Schemes ◽  
Wide Range ◽  
Ocean Biogeochemistry ◽  
The Mediterranean

Abstract. In this paper, we present a coupling scheme between the Massachusetts Institute of Technology general circulation model (MITgcm) and the Biogeochemical Flux Model (BFM). The MITgcm and BFM are widely used models for geophysical fluid dynamics and for ocean biogeochemistry, respectively, and they benefit from the support of active developers and user communities. The MITgcm is a state-of-the-art general circulation model for simulating the ocean and the atmosphere. This model is fully 3-D (including the non-hydrostatic term of momentum equations) and is characterized by a finite-volume discretization and a number of additional features enabling simulations from global (O(107) m) to local scales (O(100) m). The BFM is a biogeochemical model based on plankton functional type formulations, and it simulates the cycling of a number of constituents and nutrients within marine ecosystems. The online coupling presented in this paper is based on an open-source code, and it is characterized by a modular structure. Modularity preserves the potentials of the two models, allowing for a sustainable programming effort to handle future evolutions in the two codes. We also tested specific model options and integration schemes to balance the numerical accuracy against the computational performance. The coupling scheme allows us to solve several processes that are not considered by each of the models alone, including light attenuation parameterizations along the water column, phytoplankton and detritus sinking, external inputs, and surface and bottom fluxes. Moreover, this new coupled hydrodynamic–biogeochemical model has been configured and tested against an idealized problem (a cyclonic gyre in a mid-latitude closed basin) and a realistic case study (central part of the Mediterranean Sea in 2006–2012). The numerical results consistently reproduce the interplay of hydrodynamics and biogeochemistry in both the idealized case and Mediterranean Sea experiments. The former reproduces correctly the alternation of surface bloom and deep chlorophyll maximum dynamics driven by the seasonal cycle of winter vertical mixing and summer stratification; the latter simulates the main basin-wide and mesoscale spatial features of the physical and biochemical variables in the Mediterranean, thus demonstrating the applicability of the new coupled model to a wide range of ocean biogeochemistry problems.

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