Posts Tagged 'Mediterranean'

Ocean acidification affects calcareous tube growth in adult stage and reared offspring of serpulid polychaetes

The energetically costly transition from free-swimming larvae to benthic life stage and maintenance of a calcareous structure can make calcifying marine invertebrates vulnerable to ocean acidification. The first goal of this study was to evaluate the impacts of ocean acidification on calcified tube growth for two Serpulidae polychaete worms. Spirorbis sp. and Spirobranchus triqueter were collected at 11 m depth from the Northwest Mediterranean Sea and maintained for 30 and 90 d, at three mean pHT levels (total scale) of 8.1 (ambient), 7.7, and 7.4. Moderately decreased tube elongation rates were observed in both species at a pHT of 7.7 while severe reductions occurred at pHT 7.4. There was visual evidence of dissolution and tubes were more fragile at lower pH but, fragility was not attributed to changes in fracture toughness. Instead, it appeared to be due to the presence of larger alveoli covered in a thinner calcareous layer. The second objective of the study was to test for effects in offspring development of the species S. triqueter. Spawning was induced, and offspring were reared in the same pH conditions the parents experienced. Trochophore size was reduced at the lowest pH level but settlement success was similar across pH conditions. Post-settlement tube growth was most affected. At 38 d post-settlement, juvenile tubes at pHT of 7.7 and 7.4 were half the size of those at pHT 8.1. Results suggest future carbonate chemistry will negatively affect initiation and persistence of both biofouling and epiphytic polychaete tube worms.

Continue reading ‘Ocean acidification affects calcareous tube growth in adult stage and reared offspring of serpulid polychaetes’

Seawater acidification and emerging contaminants: a dangerous marriage for haemocytes of marine bivalves

Highlights

• Reduced pH and diclofenac affect haemocyte parameters in exposed mussels and clams.

• During exposure effects of pH persisted, those of diclofenac appeared later.

• Different patterns in haemocyte responses were observed in the two species.

• Interaction between pH and diclofenac was more evident in mussels.

Abstract

The combined effects of seawater acidification and the non-steroidal anti-inflammatory drug diclofenac on haemocyte parameters of the mussel Mytilus galloprovincialis and the clam Ruditapes philippinarum were investigated for the first time. Animals were maintained for one week (T0) in natural pH condition (8.1) and two reduced pH values (pH −0.4 units and pH −0.7 units). Bivalves were then exposed for additional 14 days (T1 and T2) to the three experimental pH values in both the presence and absence of environmentally realistic concentrations of diclofenac (0.05 and 0.50 μg/L). To assess potential impairment in immunosurveillance, haemocyte parameters (total haemocyte count, haemocyte volume and diameter, Neutral Red uptake, haemocyte proliferation and lysozyme activity) were measured after 7, 14 and 21 days of exposure to differing pH value or pH/diclofenac combinations. In both species, pH affected the whole haemocyte data set at all sampling times, influencing most of the parameters measured at T0 and T1 in clams, and at T2 in mussels. Conversely, in both species diclofenac affected the overall haemocyte response at T2 only. However, in R. philippinarum a higher number of haemocyte parameters were significantly influenced even at T1. A significant interaction between pH and diclofenac was mainly evident in mussels, affecting haemocyte size and lysozyme activity at both T1 and T2. Overall, the results obtained demonstrated that the experimental conditions tested can alter markedly haemocyte parameters in marine bivalves.

Continue reading ‘Seawater acidification and emerging contaminants: a dangerous marriage for haemocytes of marine bivalves’

Ocean acidification at a coastal CO2 vent induces expression of stress-related transcripts and transposable elements in the sea anemone Anemonia viridis

Ocean acidification threatens to disrupt interactions between organisms throughout marine ecosystems. The diversity of reef-building organisms decreases as seawater CO2 increases along natural gradients, yet soft-bodied animals, such as sea anemones, are often resilient. We sequenced the polyA-enriched transcriptome of adult sea anemone Anemonia viridis and its dinoflagellate symbiont sampled along a natural CO2 gradient in Italy to assess stress levels in these organisms. We found that about 3.1% of the anemone transcripts, but <1% of the Symbiodinium sp. transcripts were differentially expressed. Processes enriched at high seawater CO2 were linked to cellular stress and inflammation, including significant up-regulation of protective cellular functions and down-regulation of metabolic pathways. Transposable elements were differentially expressed at high seawater CO2, with an extreme up-regulation (> 100-fold) of the BEL-family of long terminal repeat retrotransposons. Seawater acidified by CO2 generated a significant stress reaction in A. viridis, but no bleaching was observed and Symbiodinium sp. appeared to be less affected. These observed changes indicate the mechanisms by which A. viridis acclimate to survive chronic exposure to ocean acidification conditions. We conclude that many organisms that are common in acidified conditions may nevertheless incur costs due to hypercapnia and/or lowered carbonate saturation states.

Continue reading ‘Ocean acidification at a coastal CO2 vent induces expression of stress-related transcripts and transposable elements in the sea anemone Anemonia viridis’

Remote monitoring of seawater temperature and pH by low cost sensors

Highlights

• Autonomous system for the remote monitoring of pH and temperature in seawater

• Potentiometric pH sensor based on functionalized reduced graphene oxide

• pH and temperature data published in a database accessible on the web

Abstract

Monitoring chemical and physical properties of seawater is important to assess the status and predict future changes of marine environment. Among possible parameters, pH and temperature are frequently measured since they directly affect chemical and biological systems. Seawater assessment, conventionally performed in situ, is labour intensive and time consuming, but now remote sensor networks promise to become a viable tool to obtain spatial and temporal information over a wide range. Here we describe the development and validation of an autonomous system for the remote monitoring of pH and temperature in seawater. The device consists of a graphene-based pH sensor, a thermistor, an electronic readout, a smartphone and a power unit. After deployment in a marine testing site at the Livorno harbour in Italy, the system published on the web pH and temperature data for more than a week, whose accuracy was confirmed by comparison with a reference system.

Continue reading ‘Remote monitoring of seawater temperature and pH by low cost sensors’

The carbonate system of the Eastern-most Mediterranean Sea, Levantine Sub-basin: variations and drivers

The carbonate system is a vital buffering system that controls the pH of seawater and maintains a healthy environment for marine organisms. As concerns regarding the fate of anthropogenic CO2 in the oceans are rising, it is becoming increasingly urgent to systematically quantify and understand this system’s parameters, particularly in heavily human-impacted areas, such as the Mediterranean Sea. To date, the paucity of time-series stations adopted to monitor the carbonate system in this sea has precluded characterizing the region at an adequate spatial resolution. Here, we present and study the seasonal and annual variability and drivers of the first carbonate system dataset collected for the Lebanese waters, monthly at the upper 80 m between 2012 and 2017 in two time-series stations offshore the North of Lebanon-Levantine Sub-basin, Eastern Mediterranean Sea. Annual trends were calculated for the non-adjusted and the adjusted carbonate system parameters (an adjustment that reduces the influence of simple-dilution-concentration [SDC] processes on the trends). Our results show high carbonate system inventory [total alkalinity (AT), total dissolved inorganic carbon (CT), and pH] compared to other Mediterranean areas. The obtained trends reflect increasing rates for both AT and CT, only significant at surface for CT(+5 ± 2 μmol kg−1.yr−1; p < 0.05). Whereas annual acidification rates were always significant (i.e. from −0.009 ± 0.004 to −0.0021 ± 0.001 pH units.yr−1at 0 m and in the upper 80 m respectively for pHT25adj). Concomitantly, decreasing trends of the saturation states for both CaCO3 minerals were calculated (−0.1 ± 0.04 and −0.07 ± 0.02 yr−1 for calcite and aragonite respectively at surface; p < 0.05). Moreover, our results showed that SDC processes, together with CO2 release/invasion and the active overturning circulation, are controlling this system in the Lebanese seawater, Eastern-most Mediterranean Sea. Contrariwise, the increasing trend of total alkalinity, mainly attributed to SDC processes (i.e. riverine inputs, weathering during extreme events, precipitations), may be buffering the observed acidification rate, which could have been worst in case AT in our area was lower.

Continue reading ‘The carbonate system of the Eastern-most Mediterranean Sea, Levantine Sub-basin: variations and drivers’

Living in future ocean acidification, physiological adaptive responses of the immune systems of sea urchins resident at a CO2 vent system

Highlights

• Paracentrotus lividus living at CO2 vents was compared to those at two control sites.
• Sea urchins are adapted to life at vent site by altering immune cells metabolism.
• Vent animals show a rearrangement of defensive abilities and antioxidant processes.

Abstract

The effects of ocean acidification, a major anthropogenic impact on marine life, have been mainly investigated in laboratory/mesocosm experiments. We used the CO2 vents at Ischia as a natural laboratory to study the long-term effects of ocean acidification on the sea urchin Paracentrotus lividus population resident in low-pH (7.8 ± 0.2) compared to that at two control sites (pH 8.02 ± 0.00; 8.02 ± 0.01). The novelty of the present study is the analysis of the sea urchin immune cells, the sentinels of environmental stress responses, by a wide-ranging approach, including cell morphology, biochemistry and proteomics. Immune cell proteomics showed that 311 proteins were differentially expressed in urchins across sites with a general shift towards antioxidant processes in the vent urchins. The vent urchin immune cells showed higher levels of total antioxidant capacity, up-regulation of phagosome and microsomal proteins, enzymes of ammonium metabolism, amino-acid degradation, and modulation of carbon metabolism proteins. Lipid-hydroperoxides and nitric oxide levels were not different in urchins from the different sites. No differences in the coelomic fluid pH, immune cell composition, animal respiration, nitrogen excretion and skeletal mineralogy were observed. Our results reveal the phenotypic plasticity of the immune system of sea urchins adapted to life at vent site, under conditions commensurate with near-future ocean acidification projections.

Continue reading ‘Living in future ocean acidification, physiological adaptive responses of the immune systems of sea urchins resident at a CO2 vent system’

Spatio-temporal distribution of physicochemical and bacteriological parameters in the north area of Monastir bay, eastern coast of Tunisia

Temporal characterization of physicochemical and bacteriological parameters of the Monastir bay was conducted out on 12 stations, during six sampling periods in 2014. Results showed a seasonal variation on the physicochemical parameters of the water masses (temperature, salinity, oxygen, pH, and turbidity) and well-oxygenated waters. Results indicated the absence of mineral phosphorus and the presence of low concentration of organic phosphorus in the stations close the coastline. Mineral nitrogen represented completely by nitrate, and organic nitrogen was detected everywhere during all sampling periods without any particular distribution. Chlorophyll-a concentrations present at low ratio characterizing an oligotrophic ecosystem showed two peaks, one during spring (April, May) and second in fall (September), and were significantly correlated with temperature (R2 = 0.82). Statistical analysis of different physicochemical parameters showed a correlation between temperature pH and oxygen. ANOVA tests showed a significant difference inter-sampling periods and between stations. Bacterial flora is dominated by halotolerant germs, which showed higher concentrations in the southern part of the studied area and are inversely correlated with salinity, turbidity, oxygen, and organic nitrogen (respectively R2 = − 0.62; − 0.79; − 0.84; − 0.72). The same evolution pattern was observed in mesophilic non-halo-obligate microflora. The Vibrionaceae concentration was correlated with water temperature and was within the standards for marine waters. Fecal coliform bacteria are absent in the studied area during all sampling periods. No particularity in water quality was noticed in this ecosystem, which characterized a good state. However, one can say that the collected data on physicochemical and bacteriological evolution can provide baseline information for assisting management of the Monastir bay, which represented a typical and important model of south Mediterranean Sea.

Continue reading ‘Spatio-temporal distribution of physicochemical and bacteriological parameters in the north area of Monastir bay, eastern coast of Tunisia’


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Ocean acidification in the IPCC AR5 WG II

OUP book