scholarly journals Selective top-down control of epiphytic biomass by amphipods from Posidonia oceanica meadows: implications for ecosystem functioning

2020 ◽  
Vol 145 (2) ◽  
Author(s):  
Loïc N. Michel ◽  
Patrick Dauby ◽  
Alessandra Dupont ◽  
Sylvie Gobert
Keyword(s):  
Ecosystem Functioning ◽  
Posidonia Oceanica ◽  
Seagrass Species ◽  
Coastal Zones ◽  
Top Down ◽  
Essential Components ◽  
Mutualistic Relationship ◽  
N Enrichment ◽  
Adequate Data ◽  
Endangered Ecosystems

Mediterranean Posidonia oceanica meadows shelter an important biomass and biodiversity of amphipod crustaceans that graze on epiphytes. However, their actual significance for ecosystem functional processes is hard to estimate, due to the lack of adequate data. Here, a field microcosm-based inclusion experiment was used to test if three of the dominant taxa of the amphipod community (Apherusa chiereghinii, Dexamine spiniventris and Gammarus spp.) could exert top-down control on seagrass leaf epiphytes. Influence of amphipod activity on nutrient availability for the host species was also investigated. All grazer taxa significantly reduced biomasses of erect macroalgae and erect sessile animals present on leaves. None of them consumed encrusting epiflora or epifauna. This selective top-down control could have important implications for the structure of the epiphytic community on leaves of P. oceanica, which is one of the most diverse and abundant of all seagrass species. Grazing activity of all taxa caused higher N content of seagrass leaves, likely through amphipod excretion and/or sloppy feeding. Since P. oceanica meadows often grow in oligotrophic zones where plant growth can be nutrient-limited, this N enrichment could enhance seagrass production. Overall, the ecological interaction between P. oceanica and amphipods could be seen as a facultative mutualistic relationship. Our results suggest that amphipod mesograzers are key-elements in some of the functional processes regulating these complex and yet endangered ecosystems, which are essential components of Mediterranean coastal zones.

scholarly journals A Comparison of Abundance and Diversity of Epiphytic Microalgal Assemblages on the Leaves of the SeagrassesPosidonia oceanica(L.) andCymodocea nodosa(Ucria) Asch in Eastern Tunisia

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Lotfi Mabrouk ◽  
Mounir Ben Brahim ◽  
Asma Hamza ◽  
Mabrouka Mahfoudhi ◽  
Med Najmeddine Bradai
Keyword(s):  
Growth Rate ◽  
Species Composition ◽  
Posidonia Oceanica ◽  
Cymodocea Nodosa ◽  
Seagrass Species ◽  
Light Penetration ◽  
Grazing Effect ◽  
Abundance And Diversity ◽  
Fast Growing Species ◽  
Host Characteristics

We studied spatial patterns in assemblages of epiphytic microalgae on the leaves of two seagrass species with different morphologies and longevity,Cymodocea nodosaandPosidonia oceanica, which cooccur in Chebba in Eastern Tunisia. Epiphyte assemblages were described for each species in summer. Epiphyte microalgal assemblages were more abundant on the leaves ofC. nodosabut more diversified on the leaves ofP. oceanica. We suggest that the differences in species composition and abundance between those seagrass species may reflect an interaction of timescales of seagrass longevity with timescales of algal reproductive biology. Short-livedC. nodosawas dominated by fast growing species such as the cyanobacteria speciesOscillatoriasp., whileP. oceanicaleaves were colonized by more mature and diversified species such as Prorocentrales. Local environmental conditions (hydrodynamics, light penetration), host characteristics (meadow type, shapes forms of leaves, life span, and growth rate), and grazing effect seem also to be responsible for these dissimilarities in epiphytic microalgae communities.

Thermo-chemical properties of biomass from Posidonia oceanica

2014 ◽  
Vol 68 (7) ◽  
Author(s):  
Agnieszka Plis ◽  
Janusz Lasek ◽  
Agnieszka Skawińska ◽  
Marcin Kopczyński
Keyword(s):  
Mediterranean Basin ◽  
Oxidative Degradation ◽  
Chemical Properties ◽  
Posidonia Oceanica ◽  
Coastal Zones ◽  
Infrared Spectrometer ◽  
The Mediterranean ◽  
Diffuse Reflectance Infrared ◽  
The Mediterranean Basin ◽  
Thermo Oxidative Degradation

AbstractPosidonia oceanica (PO) is a marine plant endemic to the Mediterranean basin, forming extensive grasslands. Onshore residues represent a major environmental, economic, social and hygienic problem in all coastal zones of the Mediterranean basin due to the great disturbance they cause to bathers and beachfront populations. This work sought to evaluate the thermo-chemical properties of PO in pyrolysis and thermo-oxidative degradation processes. The investigations were carried out using a thermogravimetric analyser (TGA) coupled to a quadrupole mass spectrometer (MS) and an infrared spectrometer (FTIR). In addition, proximate, ultimate, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and biodegradability analyses were carried out on PO. The biodegradability analysis confirmed that residues of PO were a biodegradable material. Accordingly, the application of PO as a feedstock for combustion/co-combustion or biorefining is recommended.

scholarly journals Photosynthetic activity buffers ocean acidification in seagrass meadows

2013 ◽  
Vol 10 (7) ◽  
pp. 12313-12346 ◽  
Author(s):  
I. E. Hendriks ◽  
Y. S. Olsen ◽  
L. Ramajo ◽  
L. Basso ◽  
A. Steckbauer ◽  
...  
Keyword(s):  
Metabolic Activity ◽  
Structural Parameters ◽  
Vertical Mixing ◽  
Posidonia Oceanica ◽  
Shoot Density ◽  
Coastal Zones ◽  
Carbonate System ◽  
Saturation State ◽  
Seagrass Meadows ◽  
Density And Biomass

Abstract. Macrophytes growing in shallow coastal zones characterized by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH ranges is in shallow (5–12 m) seagrass (Posidonia oceanica) meadows from 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean and max pHNBS and max ΩAr. Oxygen production positively influenced the range and maximum pHNBS and the range of ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. ΩAr was positively correlated with the calcium carbonate load of the leaves, demonstrating a direct link between structural parameters, ΩAr and carbonate deposition. There was a direct relationship between ΩAr, influenced directly by meadow LAI, and CaCO3 content of the leaves. Therefore, calcifying organisms, e.g. epiphytes with carbonate skeletons, might benefit from the modification of the carbonate system by the meadow. The meadow might be capable of providing refugia for calcifiers by increasing pH and ΩAr through metabolic activity. There is, however, concern for the ability of seagrasses to provide this refugia function in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, both strongly linked to LAI. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.

Mediterranean Tapeweed Posidonia oceanica (L.) Delile, an Endangered Seagrass Species

2021 ◽  
Vol 0 (0) ◽  
pp. 0-0
Author(s):  
Laila M.M. Bidak ◽  
Selim Z. Heneidy ◽  
Li Wenzhao ◽  
Amal M. Fakhry ◽  
Eman T. El-Kenany ◽  
...  
Keyword(s):  
Posidonia Oceanica ◽  
Seagrass Species

scholarly journals Photosynthetic activity buffers ocean acidification in seagrass meadows

2014 ◽  
Vol 11 (2) ◽  
pp. 333-346 ◽  
Author(s):  
I. E. Hendriks ◽  
Y. S. Olsen ◽  
L. Ramajo ◽  
L. Basso ◽  
A. Steckbauer ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Vertical Mixing ◽  
Posidonia Oceanica ◽  
Shoot Density ◽  
Positive Trend ◽  
Coastal Zones ◽  
Carbonate System ◽  
Saturation State ◽  
Seagrass Meadows ◽  
Density And Biomass

Abstract. Macrophytes growing in shallow coastal zones characterised by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH changes in shallow (5–12 m) seagrass (Posidonia oceanica) meadows spanning 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr)) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean, max and range pHNBS and max and range ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced max and min ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. Max and range ΩAr within the meadow showed a positive trend with the calcium carbonate load of the leaves, pointing to a possible link between structural parameters, ΩAr and carbonate deposition. Calcifying organisms, e.g. epiphytes with carbonate skeletons, may benefit from the modification of the carbonate system by the meadow. There is, however, concern for the ability of seagrasses to provide modifications of similar importance in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, on which LAI is based. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.

scholarly journals The meaning of functional trait composition of food webs for ecosystem functioning

2016 ◽  
Vol 371 (1694) ◽  
pp. 20150268 ◽  
Author(s):  
Dominique Gravel ◽  
Camille Albouy ◽  
Wilfried Thuiller
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Functional Diversity ◽  
Ecosystem Functioning ◽  
Functional Trait ◽  
Plant Ecology ◽  
Functional Composition ◽  
Top Down ◽  
Bottom Up ◽  
Functional Trait Diversity

There is a growing interest in using trait-based approaches to characterize the functional structure of animal communities. Quantitative methods have been derived mostly for plant ecology, but it is now common to characterize the functional composition of various systems such as soils, coral reefs, pelagic food webs or terrestrial vertebrate communities. With the ever-increasing availability of distribution and trait data, a quantitative method to represent the different roles of animals in a community promise to find generalities that will facilitate cross-system comparisons. There is, however, currently no theory relating the functional composition of food webs to their dynamics and properties. The intuitive interpretation that more functional diversity leads to higher resource exploitation and better ecosystem functioning was brought from plant ecology and does not apply readily to food webs. Here we appraise whether there are interpretable metrics to describe the functional composition of food webs that could foster a better understanding of their structure and functioning. We first distinguish the various roles that traits have on food web topology, resource extraction (bottom-up effects), trophic regulation (top-down effects), and the ability to keep energy and materials within the community. We then discuss positive effects of functional trait diversity on food webs, such as niche construction and bottom-up effects. We follow with a discussion on the negative effects of functional diversity, such as enhanced competition (both exploitation and apparent) and top-down control. Our review reveals that most of our current understanding of the impact of functional trait diversity on food web properties and functioning comes from an over-simplistic representation of network structure with well-defined levels. We, therefore, conclude with propositions for new research avenues for both theoreticians and empiricists.

scholarly journals Mediterranean seagrasses as carbon sinks: Methodological and regional differences

2021 ◽  
Author(s):  
Anna Escolano-Moltó ◽  
Susana Flecha ◽  
Raquel Vaquer-Sunyer ◽  
Marlene Wesselmann ◽  
Núria Marbà ◽  
...  
Keyword(s):  
Anthropogenic Activities ◽  
Posidonia Oceanica ◽  
Western Mediterranean ◽  
Species Level ◽  
Published Data ◽  
Seagrass Species ◽  
Carbon Sinks ◽  
Western Basin ◽  
Seagrass Community ◽  
Benthic Chambers

Abstract. The increasing rates of CO2 due to anthropogenic activities are causing important potential climate threats for the Mediterranean Sea: ocean acidification and warming. In this region, two seagrass species, Posidonia oceanica and Cymodocea nodosa can play a crucial role in climate change mitigation. Through their metabolic activity, they can act as carbon sinks; buffer lowering pH values during the day and store carbon in the sediment underneath their meadows. In this study we analyse the metabolism synthesized from published data on seagrass community metabolism and from own results to evaluate trends through time of these two species comparing two methodologies: benthic chambers and multiparametric sensors. Furthermore, we analysed seasonal trends of both seagrass species´ metabolic rates and their variation between the Eastern and Western Mediterranean basins, with no significant results despite the clear visual trends. Our analysis revealed that there are significant differences between methodologies, with multiparametric sensors estimating higher rates, but unable to differentiate between habitats and useful to assess seagrass metabolism at a community level whereas benthic chambers are capable to evaluate rates at a seagrass species level. We found significant differences between the two Mediterranean regions for both methodologies, with highest rates of Net Community Production found in the Easter basin. At a species level, we found that Posidonia was more productive compared to Cymodocea. Furthermore, 86.7 % of the metabolic values reflected that the meadows were acting as carbon sinks in the Western basin.

Tissue-specific transcriptomic profiling provides new insights into the reproductive ecology and biology of the iconic seagrass species Posidonia oceanica

2017 ◽  
Vol 35 ◽  
pp. 51-61 ◽  
Author(s):  
Laura Entrambasaguas ◽  
Marlene Jahnke ◽  
Elio Biffali ◽  
Marco Borra ◽  
Remo Sanges ◽  
...  
Keyword(s):  
Reproductive Ecology ◽  
Posidonia Oceanica ◽  
Seagrass Species ◽  
Transcriptomic Profiling ◽  
Tissue Specific
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