Posts Tagged 'multiple factors'



Elevated carbon dioxide and reduced salinity enhance mangrove seedling establishment in an artificial saltmarsh community

The global phenomenon of mangrove encroachment into saltmarshes has been observed across five continents. It has been proposed that this encroachment is driven in part by rising atmospheric CO2 concentration and reduced salinity in saltmarshes resulting from rising sea levels enhancing the establishment success of mangrove seedlings. However, this theory is yet to be empirically tested at the community-level. In this study, we examined the effect of CO2 and salinity on seedling growth of two mangrove species, Aegiceras corniculatum and Avicennia marina, grown individually and in a model saltmarsh community in a glasshouse experiment. We found that the shoot (210%) and root (91%) biomass of the saltmarsh species was significantly greater under elevated CO2. As a result, both mangrove species experienced a stronger competitive effect from the saltmarsh species under elevated CO2. Nevertheless, A. marina seedlings produced on average 48% more biomass under elevated CO2 when grown in competition with the saltmarsh species. The seedlings tended to allocate this additional biomass to growing taller suggesting they were light limited. In contrast, A. corniculatum growth did not significantly differ between CO2 treatments. However, it had on average 36% greater growth under seawater salinity compared to hypersaline conditions. Avicennia marina seedlings were not affected by salinity. From these results, we suggest that although CO2 and salinity are not universal drivers determining saltmarsh–mangrove boundaries, it is likely that rising atmospheric CO2 concentration and reduced salinity associated with sea level rise will enhance the establishment success of mangrove seedlings in saltmarshes, which may facilitate mangrove encroachment in the future.

Continue reading ‘Elevated carbon dioxide and reduced salinity enhance mangrove seedling establishment in an artificial saltmarsh community’

The different responses of growth and photosynthesis to NH4+ enrichments between Gracilariopsis lemaneiformis and its epiphytic alga Ulva lactuca grown at elevated atmospheric CO2

Highlights

  • Responses of two algal species to NH4+ and CO2 enrichments were investigated.
  • 100 μmol L−1 NH4+ enhanced growth and photosynthesis in both algal species.
  • 2500 μmol L−1NH4+ was toxic to Gracilariopsis lemaneiformis but not Ulva lactuca.
  • Elevated CO2 reduced the toxicity of 2500 μmol L−1 NH4+ to G. lemaneiformis.

Abstract

We investigated how elevated CO2 affects the responses of Gracilariopsis lemaneiformis and Ulva lactuca to NH4+ enrichments. All algae were incubated under four nutritional conditions (zero addition, 100, 500, and 2500 μM NH4+), and two CO2 levels (390 ppm and 1000 ppm). The growth, photosynthesis, and soluble protein contents of both species increased under the eutrophication condition (100 μM NH4+). However, the growth and carotenoid contents of the two species declined when NH4+ concentration increased. Under the super eutrophication condition (2500 μM NH4+), all indexes measured in G. lemaneiformis were suppressed, while the growth and photosynthesis in U. lactuca changed indistinctively, both compared with the control. Moreover, under the super eutrophication condition, elevated CO2 reduced the suppression in the growth of G. lemaneiformis, but decreased the growth of U. lactuca. Nonetheless, G. lemaneiformis displayed much lower growth rates than U. lactuca under the super eutrophication and elevated CO2 condition.

Continue reading ‘The different responses of growth and photosynthesis to NH4+ enrichments between Gracilariopsis lemaneiformis and its epiphytic alga Ulva lactuca grown at elevated atmospheric CO2’

The influence of climate change related factors on the response of two clam species to diclofenac

Highlights

• Diclofenac strongly affected clams antioxidant defences, especially in Ruditapes decussatus.

• Cellular damage was prevented by enzymatic and behaviour defence mechanisms.

• Redox balance was most affected in Ruditapes philippinarum.

•Diclofenac bioaccumulation was reduced under forecasted climate change conditions.

Abstract

Diclofenac (DIC) is one of the non-steroidal anti-inflammatory drugs (NSAID) with higher consumption rates, used in both human and veterinary medicine. Previous studies already demonstrated the presence of this drug in aquatic environments and adverse effects towards inhabiting organisms. However, with the predictions of ocean acidification and warming, the impacts induced by DIC may differ from what is presently known and can be species-dependent. Thus, the present study aimed to comparatively assess the effects caused by DIC in the clams Ruditapes philippinarum and Ruditapes decussatus and evaluate if these impacts were influenced by pH and temperature. For this, organisms were acclimated for 30 days at two different temperature and pH (control conditions: pH 8.1, 17 °C; climate change forecasted scenario: pH 7.7, 20 °C) in the absence of drugs (experimental period I) followed by 7 days exposure under the same water physical parameters but in absence or presence of the pharmaceutical drug (at 1 μg/L, experimental period II). Biochemical responses covering metabolic capacity, oxidative stress and damage-related biomarkers were contrasted in clams at the end of the second experimental period. The results showed that under actual conditions, R. philippinarum individuals exposed to DIC presented enhanced antioxidant activities and reduced their respiration rate compared with non-contaminated clams. When exposed to the predicted climate change conditions, a similar response was observed in contaminated clams, but in this case clams increased their metabolic activities probably to fight the stress caused by the combination of both stressors. When R. decussatus was exposed to DIC, even at actual pH and temperature conditions, their antioxidant defences were also elevated but their baseline enzymatic activities were also naturally higher in respect to R. philippinarum. Although clams may use different strategies to prevent DIC damage, both clam species showed under low pH and high temperature limited oxidative stress impacts in line with a lower DIC bioaccumulation. The present findings reveal that predicted climate change related factors may not enhance the impacts of DIC in Ruditapes clams in a species-dependent manner although both displayed particular mechanisms to face stress.

Continue reading ‘The influence of climate change related factors on the response of two clam species to diclofenac’

Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem

The plea for using more “realistic,” community‐level, investigations to assess the ecological impacts of global change has recently intensified. Such experiments are typically more complex, longer, more expensive, and harder to interpret than simple organism‐level benchtop experiments. Are they worth the extra effort? Using outdoor mesocosms, we investigated the effects of ocean warming (OW) and acidification (OA), their combination (OAW), and their natural fluctuations on coastal communities of the western Baltic Sea during all four seasons. These communities are dominated by the perennial and canopy‐forming macrophyte Fucus vesiculosus—an important ecosystem engineer Baltic‐wide. We, additionally, assessed the direct response of organisms to temperature and pH in benchtop experiments, and examined how well organism‐level responses can predict community‐level responses to the dominant driver, OW. OW affected the mesocosm communities substantially stronger than acidification. OW provoked structural and functional shifts in the community that differed in strength and direction among seasons. The organism‐level response to OW matched well the community‐level response of a given species only under warm and cold thermal stress, that is, in summer and winter. In other seasons, shifts in biotic interactions masked the direct OW effects. The combination of direct OW effects and OW‐driven shifts of biotic interactions is likely to jeopardize the future of the habitat‐forming macroalga F. vesiculosus in the Baltic Sea. Furthermore, we conclude that seasonal mesocosm experiments are essential for our understanding of global change impact because they take into account the important fluctuations of abiotic and biotic pressures.

Continue reading ‘Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem’

Effects of dissolved oxygen and pH on the expression of a type HBGA-like in pacific oyster

Objective: To study the effects of dissolved oxygen and pH on the expression of A type HBGA-like in pacific oysters. Methods: The HBGAs-like in the pacific oysters were isolated and extracted, and the human HBGAs were used for typing. The A type HBGAs was detected by ELISA method, and the P/N value was calculated. The content changes of A type HBGA-like in the guts and gills of pacific oysters were detected by changing the dissolved oxygen content and pH of seawater under artificial simulation conditions. Results: The HBGA-like of different tissues of oysters were classified, and the A type HBGA-like of gut and gill were selected as the main research type of subsequent experiments; the artificial simulation experiment results showed that the high pH could improve the expression of A type HBGA-like in pacific oysters gills, and the high dissolved oxygen can also improve the expression of A-type HBGA-like in pacific oysters guts. Conclusion: The results were consistent with the phenomenon that the norovirus outbreak usually occur in winter and spring, indicating that the seasonality of norovirus outbreak was correlated with the expression of A type HBGAs-like in oyster.

Continue reading ‘Effects of dissolved oxygen and pH on the expression of a type HBGA-like in pacific oyster’

Antioxidant responses of triangle sail mussel Hyriopsis cumingii exposed to harmful algae Microcystis aeruginosa and high pH

Highlights

• The comprehensive effects of toxic cyanobacteria and high pH on mussels were assessed.

• Interaction between cyanobacteria and high pH on physiological indicator were found.

• Compare to high pH, toxic M. aeruginosa induce more severe oxidative stress response.

• Toxic algae or high pH exposure history showed latent effects on Hyriopsis cumingii.

Abstract

In lakes and reservoirs, harmful algal blooms and high pH have been deemed to be two important stressors related to eutrophication, especially in the case of CO2 depletion caused by dense blooms. However, the effects of these stressors on the economically important shellfish that inhabit these waters are still not well-understood. This study evaluated the combined effects of the harmful algae Microcystis aeruginosa (0%, 50%, and 100% of total dietary dry weight) and high pH (8.0, 8.5 and 9.0) on the antioxidant responses of the triangle sail mussel H. cumingii. The mussels were exposed to algae and high pH for 14 d, followed by a 7-day depuration period. Reactive oxygen species (ROS) in the mussel hemolymph, antioxidant and detoxifying enzymes, such as glutathione-S-transferase (GST), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) in the digestive glands were analyzed during the experimental period. GST, SOD and GPx activity levels and the content of GSH increased following exposure to toxic M. aeruginosa, whereas CAT activity was inhibited. pH showed no significant effects on the immune defense mechanisms and detoxification processes. However, a high pH could cause increased ROS and MDA levels, resulting in oxidative injury. After a 7-day depuration period, exposure to toxic M. aeruginosa or high pH resulted in latent effects for most of the examined parameters. The treatment group exposed to the highest pH (9.0) displayed an increased oxidation state compared with the other pH treatments (8.0 and 8.5) for the same concentrations of toxic M. aeruginosa. The trends observed for ROS, MDA, GPx, GST, SOD and GSH levels indicated that a high density of toxic algae could result in severe and continuous effects on mussel health.

Continue reading ‘Antioxidant responses of triangle sail mussel Hyriopsis cumingii exposed to harmful algae Microcystis aeruginosa and high pH’

Combination of ocean acidification and warming enhances the competitive advantage of Skeletonema costatum over a green tide alga, Ulva linza

Highlights

• Coculture did not affect growth rate of U. linza but decreased it for S. costatum.

• Elevated CO2 relieved the inhibitory effect of U. linza on growth of S. costatum.

• At elevated CO2, higher temperature increased the growth rate of S. costatum.

• At elevated CO2, higher temperature reduced the growth rate of U. linza.

• Coculture did not affect respiration of U. linza but stimulated it for S. costatum.

Abstract

Red tide and green tide are two common algal blooms that frequently occur in many areas in the global oceans. The algae causing red tide and green tide often interact with each other in costal ecosystems. However, little is known on how future CO2-induced ocean acidification combined with temperature variation would affect the interaction of red and green tides. In this study, we cultured the red tide alga Skeletonema costatum and the green tide alga Ulva linza under ambient (400 ppm) and future CO2 (1000 ppm) levels and three temperatures (12, 18, 24 °C) in both monoculture and coculture systems. Coculture did not affect the growth rate of U. linza but significantly decreased it for S. costatum. Elevated CO2 relieved the inhibitory effect of U. linza on the growth of S. costatum, particularly for higher temperatures. At elevated CO2, higher temperature increased the growth rate of S. costatum but reduced it for U. linza. Coculture with U. linza reduced the net photosynthetic rate of S. costatum, which was relieved by elevated CO2. This pattern was also found in Chl a content, indicating that U. linza may inhibit growth of S. costatum via harming pigment synthesis and thus photosynthesis. In monoculture, higher temperature did not affect respiration rate of S. costatum but increased it in U. linza. Coculture did not affect respiration of U. linza but stimulated it for S. costatum, which was a signal of responding to biotic and/abiotic stress. The increased growth of S. costatum at higher temperature and decreased inhibition of U. linza on S. costatum at elevated CO2 suggest that red tides may have more advantages over green tides in future warmer and CO2-enriched oceans.

Continue reading ‘Combination of ocean acidification and warming enhances the competitive advantage of Skeletonema costatum over a green tide alga, Ulva linza’


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