Posts Tagged 'growth'

Recoverable impacts of ocean acidification on the tubeworm, Hydroides elegans: implication for biofouling in future coastal oceans

Ocean uptake of anthropogenic CO2 causes ocean acidification (OA), which not only decreases the calcification rate, but also impairs the formation of calcareous shells or tubes in marine invertebrates such as the dominant biofouling tubeworm species, Hydroides elegans. This study examined the ability of tubeworms to resume normal tube calcification when returned to ambient pH 8.1 from a projected near-future OA level of pH 7.8. Tubeworms produced structurally impaired and mechanically weaker calcareous tubes at pH 7.8 compared to at pH 8.1, but were able to recover when the pH was restored to ambient levels. This suggests that tubeworms can physiologically recover from the impacts of OA on tube calcification, composition, density, hardness and stiffness when returned to optimal conditions. These results help understanding of the progression of biofouling communities dominated by tubeworms in future oceans with low pH induced by OA.

Continue reading ‘Recoverable impacts of ocean acidification on the tubeworm, Hydroides elegans: implication for biofouling in future coastal oceans’

Elevated pCO2 does not impair performance in autotomised individuals of the intertidal predatory starfish Asterias rubens (Linnaeus, 1758)

Highlights

• Ocean acidification research requires further understanding on the interactions with other stressors.

• We examined the combined effects of pCO2 and arm autotomisation on Asterias rubens.

• Neither stressor affected mortality, growth, arm regeneration, righting time or arm calcium content.

• Lipid content in the pyloric caeca increased in response to elevated pCO2.

• A. rubens appears unaffected by short-term exposure to pCO2 levels predicted for 2100.

Abstract

The impacts of ocean acidification remain less well-studied in starfish compared to other echinoderm groups. This study examined the combined effects of elevated pCO2 and arm regeneration on the performance of the intertidal predatory starfish Asterias rubens, as both are predicted to come at a cost to the individual. A two-way factorial experiment (~400 μatm vs ~1000 μatm; autotomised vs non-automised individuals) was used to examine growth rates, lipid content (pyloric caeca and gonads), and calcium content (body wall) in both intact and regenerating arms, as well as subsequent effects on rate of arm regeneration, righting time (behaviour) and mortality over 120 days. Autotomised individuals tended to show lower (not significant), survival and growth. Elevated pCO2 had no effect on mortality, body growth, arm regeneration, righting time or arm calcium content. Lipid content was higher in the pyloric caeca, but not in the gonads, in response to elevated pCO2 irrespective of autotomisation. The results of the study suggest that adult A. rubens remain unaffected by increased pCO2 and/or arm autotomy for 120 days, although longer term experiments are necessary as the results indicated that survival, growth and calcification may be impaired with longer-term exposure to elevated pCO2.

Continue reading ‘Elevated pCO2 does not impair performance in autotomised individuals of the intertidal predatory starfish Asterias rubens (Linnaeus, 1758)’

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’

Effects of pH on growth and biochemical responses in Agarophyton vermiculophyllum under different temperature conditions

The effects of pH (6.2, 7.2, 8.2, 9.2, and 10.2) under rising temperature (30 °C vs 20 °C) on Agarophyton vermiculophyllum growth and bio-physiology were investigated. Results showed that A. vermiculophyllum exhibited lower growth rates under elevated temperature in all pH values. Chlorophyll a, carotenoid, and phycocyanin levels were significantly enhanced by temperature elevation (p < 0.05). Enhanced H2O2 production either at lower or higher pH values correlated with lipid peroxidation (LPO) levels under elevated temperature, which suggested oxidative stress development. Oxidative damage was more severe at elevated pH values, which is confirmed by higher reactive oxygen species (ROS) levels. Compared with ambient pH 8.2 value, lower pH values under elevated temperature lead to increase activities of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST), indicating that these enzymes played an important role to combat stress. However, decreased glutathione reductase (GR) and glutathione peroxidase (GPx) activities indicate least contribution for ROS scavenging at lower pH values. On contrary, SOD and CAT declined at elevated pH values compared with ambient pH, suggesting least contribution for ROS removal. Moreover, enhanced GR and GPx activities at elevated pH and temperature are not enough to scavenge ROS production. These data are consistent with higher H2O2 and LPO levels, and lower GST activities. Collectively, our results indicated that either pH fluctuations or elevated temperature displayed a disadvantageous influence on growth and bio-physiology of A. vermiculophyllum. Therefore, rising temperature alleviates adverse effects of seawater acidification, but it aggravates the negative effects of seawater alkalization on growth and bio-physiology of A. vermiculophyllum.

Continue reading ‘Effects of pH on growth and biochemical responses in Agarophyton vermiculophyllum under different temperature conditions’

Combined effects of CO2-driven ocean acidification and Cd stress in the marine environment: enhanced tolerance of Phaeodactylum tricornutum to Cd exposure

Highlights

• Combined effects of OA and Cd exposure on Phaeodactylum tricornutum were analyzed.

• Either OA (1500 ppm) or Cd stress (1.2 mg/L) alone inhibited the growth of P. tricornutum.

• A significantly enhanced tolerance of P. tricornutum to Cd of 1.2 mg/L occurred under OA.

Abstract

Ocean acidification (OA) and heavy metals are common stress factors for marine ecosystems subject to anthropogenic impacts. OA coupled with the heavy metal is likely to affect marine species. This study investigated the single and combined effects of OA (1500 ppm) and cadmium (Cd; 0.4, 1.2 mg/L) on the marine diatom Phaeodactylum tricornutum under 7 d exposure. The results clearly indicated that either OA or Cd stress (1.2 mg/L) alone inhibited the growth of P. tricornutum. However, under the combined OA-Cd stress, the growth inhibition disappeared, and the intracellular oxidative damage was mitigated. These results indicated a significantly enhanced tolerance of P. tricornutum to Cd while under OA conditions, which could be beneficial to the survival of this diatom. This study will ultimately help us understand the responses of marine organisms to multiple stressors and have broad implications for the potential ecological risks of Cd under future OA conditions.

Continue reading ‘Combined effects of CO2-driven ocean acidification and Cd stress in the marine environment: enhanced tolerance of Phaeodactylum tricornutum to Cd exposure’

A metabolomic approach to investigate effects of ocean acidification on a polar microalga Chlorella sp.

Highlights

• Future ocean acidification levels have little effect on the growth and photosynthesis of Chlorella sp.

• Ocean acidification promoted saturation of fatty acids and amino acid synthesis of Chlorella sp.

• Enhancement of energy production and trehalose synthesis could be the acclimation strategies of marine picochlorophytes.

Abstract

Ocean acidification, due to increased levels of anthropogenic carbon dioxide, is known to affect the physiology and growth of marine phytoplankton, especially in polar regions. However, the effect of acidification or carbonation on cellular metabolism in polar marine phytoplankton still remains an open question. There is some evidence that small chlorophytes may benefit more than other taxa of phytoplankton. To understand further how green polar picoplankton could acclimate to high oceanic CO2, studies were conducted on an Antarctic Chlorella sp. Chlorella sp. maintained its growth rate (∼0.180 d-1), photosynthetic quantum yield (Fv/Fm = ∼0.69) and chlorophyll a (0.145 fg cell-1) and carotenoid (0.06 fg cell-1) contents under high CO2, while maximum rates of electron transport decreased and non-photochemical quenching increased under elevated CO2. GCMS-based metabolomic analysis reveal that this polar Chlorella strain modulated the levels of metabolites associated with energy, amino acid, fatty acid and carbohydrate production, which could favour its survival in an increasingly acidified ocean.

Continue reading ‘A metabolomic approach to investigate effects of ocean acidification on a polar microalga Chlorella sp.’

Futuristic ocean acidification levels reduce growth and reproductive viability in the Pacific Oyster (Crassostrea gigas)

In this study, we investigated the effects of futuristic pH because of climate change on the growth and reproductive viability of the Pacific oysters. The futuristic pH levels to which adult oysters were exposed are 7.5 and 7.8 (as extreme case) and 8.1 (as moderate case), with pH 8.2 serving as the control. We monitored growth and reproductive viability over a four-week exposure period. The reproductive viability of the oysters exposed to each pH level were assessed based on the sperm motility and egg viability. Throughout the exposure period, the induced acidified nature of each treatment aquaria was maintained. Data obtained from this investigation revealed significant decrease in weight of oysters exposed to pH 7.5 and 7.8 compared to the groups exposed to pH levels 8.1 and 8.2 (p < 0.05). Groups of oysters exposed to pH 7.5 recorded as much as 10.49% decrease in weight, with specific growth rate (SGR) of -0.4 %/day. Reproductive viability was significantly compromised in groups exposed to pH 7.5 and 7.8 as evident with reduced sperm motility and percentage of ruptured eggs in these groups of oysters. We therefore postulate that climate change will have significant impact on the recruitment of oysters in coastal waters as growth and reproduction will be impaired at extreme levels of futuristic ocean acidification.

Continue reading ‘Futuristic ocean acidification levels reduce growth and reproductive viability in the Pacific Oyster (Crassostrea gigas)’


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Ocean acidification in the IPCC AR5 WG II

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