scholarly journals Effects of <i>in situ</i> CO<sub>2</sub> enrichment on structural characteristics, photosynthesis, and growth of the Mediterranean seagrass <i>Posidonia oceanica</i>

2016 ◽  
Author(s):  
T. E. Cox ◽  
F. Gazeau ◽  
S. Alliouane ◽  
I. E. Hendriks ◽  
P. Mahacek ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Structural Characteristics ◽  
Leaf Growth ◽  
Control Unit ◽  
Posidonia Oceanica ◽  
Seagrass Meadows ◽  
Reference Plot ◽  
Ocean Carbon ◽  
Additional Reference

Abstract. Seagrass are expected to benefit from increased carbon availability under future ocean acidification. This hypothesis has been little tested by in situ manipulation. To test for ocean acidification effects on seagrass meadows under controlled CO2/pH conditions, we used a Free Ocean Carbon Dioxide Enrichment (FOCE) system which allows for the precise manipulation of pH as an offset from the ambient. This system was deployed in a Posidonia oceanica meadow at 11 m depth in the Northwestern Mediterranean Sea. It consisted of two benthic enclosures, an experimental and a control unit both 1.7 m3, and an additional reference plot in the ambient (2 m2) to account for structural artifacts. The meadow was monitored from April to November 2014. The pH of the experimental enclosure was lowered by 0.26 pH units for the second half of the eight-month study. Changes in P. oceanica leaf biometrics, photosynthesis, and leaf growth accompanied seasonal changes recorded in the environment and values were similar between the two enclosures. Leaf thickness may change in response to lower pH but this requires further testing. Results suggest any benefit from ocean acidification, over the next century, on Posidonia physiology and growth may be minimal. The limited stimulation casts doubts on speculations that elevated CO2 would confer resistance to thermal stress and increase buffering capacity of meadows.

scholarly journals Effects of in situ CO<sub>2</sub> enrichment on structural characteristics, photosynthesis, and growth of the Mediterranean seagrass <i>Posidonia oceanica</i>

2016 ◽  
Vol 13 (7) ◽  
pp. 2179-2194 ◽  
Author(s):  
T. Erin Cox ◽  
Frédéric Gazeau ◽  
Samir Alliouane ◽  
Iris E. Hendriks ◽  
Paul Mahacek ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Structural Characteristics ◽  
Leaf Growth ◽  
Control Unit ◽  
Posidonia Oceanica ◽  
Seasonal Effect ◽  
Seagrass Meadows ◽  
Reference Plot ◽  
Wide Range

Abstract. Seagrass is expected to benefit from increased carbon availability under future ocean acidification. This hypothesis has been little tested by in situ manipulation. To test for ocean acidification effects on seagrass meadows under controlled CO2/pH conditions, we used a Free Ocean Carbon Dioxide Enrichment (FOCE) system which allows for the manipulation of pH as continuous offset from ambient. It was deployed in a Posidonia oceanica meadow at 11 m depth in the Northwestern Mediterranean Sea. It consisted of two benthic enclosures, an experimental and a control unit both 1.7 m3, and an additional reference plot in the ambient environment (2 m2) to account for structural artifacts. The meadow was monitored from April to November 2014. The pH of the experimental enclosure was lowered by 0.26 pH units for the second half of the 8-month study. The greatest magnitude of change in P. oceanica leaf biometrics, photosynthesis, and leaf growth accompanied seasonal changes recorded in the environment and values were similar between the two enclosures. Leaf thickness may change in response to lower pH but this requires further testing. Results are congruent with other short-term and natural studies that have investigated the response of P. oceanica over a wide range of pH. They suggest any benefit from ocean acidification, over the next century (at a pH of  ∼ 7.7 on the total scale), on Posidonia physiology and growth may be minimal and difficult to detect without increased replication or longer experimental duration. The limited stimulation, which did not surpass any enclosure or seasonal effect, casts doubts on speculations that elevated CO2 would confer resistance to thermal stress and increase the buffering capacity of meadows.

scholarly journals Patch types in Posidonia oceanica meadows around Corsica: How can we use them in seascape ecology?

2015 ◽  
Author(s):  
Arnaud Abadie ◽  
Marina Bonacorsi ◽  
Sylvie Gobert ◽  
Pierre Lejeune ◽  
Gérard Pergent ◽  
...  
Keyword(s):  
Large Scale ◽  
Water Movement ◽  
Human Impacts ◽  
Structural Characteristics ◽  
Posidonia Oceanica ◽  
Radius Of Gyration ◽  
Index Number ◽  
Fish Farms ◽  
Patch Type ◽  
Seagrass Meadows

The meadows formed by the Mediterranean seagrass Posidonia oceanica are subjected to various natural (e.g., water movement, light availability, sedimentation) and anthropogenic (e.g., anchoring, trawling, fish farms, explosives) phenomena that erode them and create diverse types of patches. The assemblage of the P. oceanica matrix and these patches creates particular seascapes. On the basis of this assessment, we aimed to investigate the importance of the patch type in structuring P. oceanica seascapes and to offer new prospects in the large scale studies of seagrass meadows. Five sites encompassing large P. oceanica meadows ranging from 1.86 km² to 4.42 km² along the Corsican coast (France) were considered. Eleven patch types with different sizes, shapes and origins were identified using side scan sonar images (sonograms). Five were recognized as natural and five as anthropogenic. One can be of both origins. The resolution of the sonograms allowed to detect patches of various sizes ranging from 1 m² to 111 829 m². The relation between structural characteristics of patches and the whole seascape aspect was explored using seven landscape metrics relevant for the study of meadows patchiness (patch area, mean radius of gyration, area-weighted radius of gyration, coefficient of variation of the Euclidean nearest-neighbor distance, area-weighted perimeter-area ratio, landscape division index, number of patches). Only a small number of patch types appears to play the strongest role in the characterization of the P. oceanica seascapes. Furthermore, the use of seascape structures seems to be suitable for the development of new tools like indices for the assessment of human impacts on P. oceanica meadows. In this perspective we propose a new and simple index, the Patchiness Source Index (PaSI), to estimate the origin of the patchiness (natural or anthropogenic) for a given area. A landscape approach, as well as information on patch dynamic, should be integrated in the new indices that aim to assess the state of conservation of the whole P. oceanica ecosystem.

scholarly journals Polychaetes associated with Posidonia oceanica meadows along a gradient of ocean acidification at a CO2 vent system (Ischia, Italy)

2015 ◽  
Author(s):  
Maria Cristina Gambi ◽  
Erica Keppel ◽  
Rosanna Guglielmo ◽  
Adriana Giangrande ◽  
Samantha L. Garrard
Keyword(s):  
Ocean Acidification ◽  
Feeding Habits ◽  
Posidonia Oceanica ◽  
Shoot Density ◽  
Low Ph ◽  
Marine Biota ◽  
The South ◽  
South Side ◽  
Seagrass Meadows ◽  
Ph Conditions

Polychaetes represent one of the most diversified and abundant taxa associated with seagrass meadows. These organisms show various feeding habits at different levels of the complex seagrass food web, representing suitable bioindicators of meadow structure and environmental status and disturbances. Ocean acidification (OA) is today considered one of the most pervasive stressors for marine biota at the level of species, communities and ecosystems. Naturally acidified systems, such as CO2 vents, represent suitable natural laboratories to study the effects of OA on benthic organisms. An analysis of polychaetes associated with Posidonia oceanica meadows located around shallow CO2 vents off the island of Ischia, is presented here. Polychaetes were collected in November 2011 with an air-lift sampler (40x40 cm; 4 replicates per station) along a gradient of OA at the Castello’s vent system at six stations (3 on the south and 3 on the north side), ranging from extreme low pH conditions (mean pH 7.5 occurring only on the south side) to control, normal pH conditions (8.12); a further control station was considered, 600 m from the Castello in similar environmental conditions and ambient pH (S. Anna meadow). A total of 99 taxa and about 4200 individual polychaetes were collected. Taxa richness showed higher values in the acidified stations, especially on the south side; similarly abundances were from two- to four-fold higher under low and extreme low pH conditions, in respect to control ones, due to relatively few dominant taxa. These are represented by Amphiglena mediterranea, Syllis gerlachi, S. prolifera, Exogone dispar, Sphaerosyllis pirifera, Polyophthalmus pictus and Kefersteinia cirrata. Multivariate analysis showed a separation between control and low pH assemblages and a separation between low pH and the extreme low pH site on the south side. Control stations showed higher variability among replicates, while acidified stations, especially those under extreme low pH conditions, showed a more homogeneous assemblage structure. These results demonstrate that many species of polychaetes are robust to OA, however, the high seagrass shoot density, occurring at acidified stations, may buffer the negative effect of this stressor on the biota, and explain both the high diversity and abundance observed there.

scholarly journals Unusually Warm Summer Temperatures Exacerbate Population and Plant Level Response of Posidonia oceanica to Anthropogenic Nutrient Stress

2021 ◽  
Vol 12 ◽  
Author(s):  
Stephanie B. Helber ◽  
Gabriele Procaccini ◽  
E. Fay Belshe ◽  
Alex Santillan-Sarmiento ◽  
Ulisse Cardini ◽  
...  
Keyword(s):  
Ecosystem Engineer ◽  
Population Level ◽  
Posidonia Oceanica ◽  
Anthropogenic Pressure ◽  
Nutrient Inputs ◽  
Area Index ◽  
Seagrass Meadows ◽  
Warm Summer ◽  
Summer Temperatures

Posidonia oceanica is a key foundation species in the Mediterranean providing valuable ecosystem services. However, this species is particularly vulnerable towards high coastal nutrient inputs and the rising frequency of intense summer heat waves, but their combined effect in situ has received little attention so far. Here, we investigated the effects of in situ nutrient addition during an unusually warm summer over a 4-month period, comparing different morphological, physiological and biochemical population metrics of seagrass meadows growing in protected areas (Ischia) with meadows already exposed to significant anthropogenic pressure (Baia – Gulf of Pozzuoli). Our study highlights that the effects of warmer than usual summer temperatures on the population level of seagrass meadows can be exacerbated if the plants are already exposed to higher anthropogenic pressures. Morphological and population level indicators mainly changed over time, possibly impacted by season and the warmer temperatures, and displayed more pronounced reductions in seagrasses from impacted sites. The additional nutrient supply had even more deleterious effects, as shown by a decrease in approximately 67% in cover in fertilized plots at high impacted sites and 33% at low impacted sites. Moreover, while rhizome starch concentration showed a seasonal increase in plants from low impacted sites it displayed a trend of a 27% decrease in fertilized plots of the high impacted sites. Epiphyte biomass was approximately four-fold higher on leaves of plants growing in impacted sites and even doubled with the additional nutrient input. Predicting and anticipating stress in P. oceanica is of crucial importance for conservation and management efforts, given the limited colonizing and reproductive ability and extremely slow growth of this ecosystem engineer. Our results suggest that monitoring efforts should focus especially on leaf area index (LAI), carbohydrate concentrations in the rhizomes, and epiphyte cover on leaves as indicators of the onset of stress in Posidonia oceanica, which can be used by decision makers to take appropriate measures before damage to the ecosystem becomes irreversible, minimize future human interference and strengthen the resilience of these important ecosystems.

scholarly journals Patch types in Posidonia oceanica meadows around Corsica: How can we use them in seascape ecology?

2015 ◽  
Author(s):  
Arnaud Abadie ◽  
Marina Bonacorsi ◽  
Sylvie Gobert ◽  
Pierre Lejeune ◽  
Gérard Pergent ◽  
...  
Keyword(s):  
Large Scale ◽  
Water Movement ◽  
Human Impacts ◽  
Structural Characteristics ◽  
Posidonia Oceanica ◽  
Radius Of Gyration ◽  
Index Number ◽  
Fish Farms ◽  
Patch Type ◽  
Seagrass Meadows

The meadows formed by the Mediterranean seagrass Posidonia oceanica are subjected to various natural (e.g., water movement, light availability, sedimentation) and anthropogenic (e.g., anchoring, trawling, fish farms, explosives) phenomena that erode them and create diverse types of patches. The assemblage of the P. oceanica matrix and these patches creates particular seascapes. On the basis of this assessment, we aimed to investigate the importance of the patch type in structuring P. oceanica seascapes and to offer new prospects in the large scale studies of seagrass meadows. Five sites encompassing large P. oceanica meadows ranging from 1.86 km² to 4.42 km² along the Corsican coast (France) were considered. Eleven patch types with different sizes, shapes and origins were identified using side scan sonar images (sonograms). Five were recognized as natural and five as anthropogenic. One can be of both origins. The resolution of the sonograms allowed to detect patches of various sizes ranging from 1 m² to 111 829 m². The relation between structural characteristics of patches and the whole seascape aspect was explored using seven landscape metrics relevant for the study of meadows patchiness (patch area, mean radius of gyration, area-weighted radius of gyration, coefficient of variation of the Euclidean nearest-neighbor distance, area-weighted perimeter-area ratio, landscape division index, number of patches). Only a small number of patch types appears to play the strongest role in the characterization of the P. oceanica seascapes. Furthermore, the use of seascape structures seems to be suitable for the development of new tools like indices for the assessment of human impacts on P. oceanica meadows. In this perspective we propose a new and simple index, the Patchiness Source Index (PaSI), to estimate the origin of the patchiness (natural or anthropogenic) for a given area. A landscape approach, as well as information on patch dynamic, should be integrated in the new indices that aim to assess the state of conservation of the whole P. oceanica ecosystem.

scholarly journals Polychaetes associated with Posidonia oceanica meadows along a gradient of ocean acidification at a CO2 vent system (Ischia, Italy)

2015 ◽  
Author(s):  
Maria Cristina Gambi ◽  
Erica Keppel ◽  
Rosanna Guglielmo ◽  
Adriana Giangrande ◽  
Samantha L. Garrard
Keyword(s):  
Ocean Acidification ◽  
Feeding Habits ◽  
Posidonia Oceanica ◽  
Shoot Density ◽  
Low Ph ◽  
Marine Biota ◽  
The South ◽  
South Side ◽  
Seagrass Meadows ◽  
Ph Conditions

Polychaetes represent one of the most diversified and abundant taxa associated with seagrass meadows. These organisms show various feeding habits at different levels of the complex seagrass food web, representing suitable bioindicators of meadow structure and environmental status and disturbances. Ocean acidification (OA) is today considered one of the most pervasive stressors for marine biota at the level of species, communities and ecosystems. Naturally acidified systems, such as CO2 vents, represent suitable natural laboratories to study the effects of OA on benthic organisms. An analysis of polychaetes associated with Posidonia oceanica meadows located around shallow CO2 vents off the island of Ischia, is presented here. Polychaetes were collected in November 2011 with an air-lift sampler (40x40 cm; 4 replicates per station) along a gradient of OA at the Castello’s vent system at six stations (3 on the south and 3 on the north side), ranging from extreme low pH conditions (mean pH 7.5 occurring only on the south side) to control, normal pH conditions (8.12); a further control station was considered, 600 m from the Castello in similar environmental conditions and ambient pH (S. Anna meadow). A total of 99 taxa and about 4200 individual polychaetes were collected. Taxa richness showed higher values in the acidified stations, especially on the south side; similarly abundances were from two- to four-fold higher under low and extreme low pH conditions, in respect to control ones, due to relatively few dominant taxa. These are represented by Amphiglena mediterranea, Syllis gerlachi, S. prolifera, Exogone dispar, Sphaerosyllis pirifera, Polyophthalmus pictus and Kefersteinia cirrata. Multivariate analysis showed a separation between control and low pH assemblages and a separation between low pH and the extreme low pH site on the south side. Control stations showed higher variability among replicates, while acidified stations, especially those under extreme low pH conditions, showed a more homogeneous assemblage structure. These results demonstrate that many species of polychaetes are robust to OA, however, the high seagrass shoot density, occurring at acidified stations, may buffer the negative effect of this stressor on the biota, and explain both the high diversity and abundance observed there.

scholarly journals Posidonia oceanica as a Source of Chromophoric Dissolved Organic Matter for the Oligotrophic NW Mediterranean Coast

2020 ◽  
Vol 8 (11) ◽  
pp. 911
Author(s):  
Francesca Iuculano ◽  
Carlos M. Duarte ◽  
Jaime Otero ◽  
Xosé Antón Álvarez-Salgado ◽  
Susana Agustí
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Rocky Shore ◽  
Posidonia Oceanica ◽  
Mediterranean Coast ◽  
Balearic Islands ◽  
Chromophoric Dissolved Organic Matter ◽  
Absorption Increase ◽  
Seagrass Meadows ◽  
Nw Mediterranean

Posidonia oceanica is a well-recognized source of dissolved organic matter (DOM) derived from exudation and leaching of seagrass leaves, but little is known about its impact on the chromophoric fraction of DOM (CDOM). In this study, we monitored for two years the optical properties of CDOM in two contrasting sites in the Mallorca Coast (Balearic Islands). One site was a rocky shore free of seagrass meadows, and the second site was characterized by the accumulation of non-living seagrass material in the form of banquettes. On average, the integrated color over the 250–600 nm range was almost 6-fold higher in the beach compared with the rocky shore. Furthermore, the shapes of the CDOM spectra in the two sites were also different. A short incubation experiment suggested that the spectral differences were due to leaching from P. oceanica leaf decomposition. Furthermore, occasionally the spectra of P. oceanica was distorted by a marked absorption increase at wavelength < 265 nm, presumably related to the release of hydrogen sulfide (HS−) associated with the anaerobic decomposition of seagrass leaves within the banquettes. Our results provide the first evidence that P. oceanica is a source of CDOM to the surrounding waters.

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