Posts Tagged 'physiology'



Contrasting responses of photosynthesis and photochemical efficiency to ocean acidification under different light environments in a calcifying alga

Ocean acidification (OA) is predicted to enhance photosynthesis in many marine taxa. However, photophysiology has multiple components that OA may affect differently, especially under different light environments, with potentially contrasting consequences for photosynthetic performance. Furthermore, because photosynthesis affects energetic budgets and internal acid-base dynamics, changes in it due to OA or light could mediate the sensitivity of other biological processes to OA (e.g. respiration and calcification). To better understand these effects, we conducted experiments on Porolithon onkodes, a common crustose coralline alga in Pacific coral reefs, crossing pCO2 and light treatments. Results indicate OA inhibited some aspects of photophysiology (maximum photochemical efficiency), facilitated others (α, the responsiveness of photosynthesis to sub-saturating light), and had no effect on others (maximum gross photosynthesis), with the first two effects depending on treatment light level. Light also exacerbated the increase in dark-adapted respiration under OA, but did not alter the decline in calcification. Light-adapted respiration did not respond to OA, potentially due to indirect effects of photosynthesis. Combined, results indicate OA will interact with light to alter energetic budgets and potentially resource allocation among photosynthetic processes in P. onkodes, likely shifting its light tolerance, and constraining it to a narrower range of light environments.

Continue reading ‘Contrasting responses of photosynthesis and photochemical efficiency to ocean acidification under different light environments in a calcifying alga’

Greenhouse gases, nutrients and the carbonate system in the Reloncaví Fjord (Northern Chilean Patagonia): implications on aquaculture of the mussel, Mytilus chilensis, during an episodic volcanic eruption

Highlights
• A large bloom of phytoplankton was detected in the surface waters of the Reloncaví fjord following the Calbuco volcano eruption.

• Subsequent to the Calbuco volcano eruption, higher N2O, CH4 and SO42− concentrations were observed in Fjord surface waters close to areas of river discharge.

• Optimal juvenile mussel growth was observed in refugee subsurface depths coinciding with increased aragonite saturation.

• Thus, the observed trends in the carbonate system and nutrient outputs may be valuable for developing effective management strategies for mussel aquaculture in the Reloncaví Fjord.

Abstract
This study investigates the immediate and mid-term effects of the biogeochemical variables input into the Reloncaví fjord (41°40′S; 72°23′O) as a result of the eruption of Calbuco volcano. Reloncaví is an estuarine system supporting one of the largest mussels farming production within Northern Chilean-Patagonia. Field-surveys were conducted immediately after the volcanic eruption (23–30 April 2015), one month (May 2015), and five months posterior to the event (September 2015). Water samples were collected from three stations along the fjord to determine greenhouse gases [GHG: methane (CH4), nitrous oxide (N2O)], nutrients [NO3−, NO2−, PO43−, Si(OH)4, sulphate (SO42−)], and carbonate systems parameters [total pH (pHT), temperature, salinity, dissolved oxygen (O2), and total alkalinity (AT)]. Additionally, the impact of physicochemical changes in the water column on juveniles of the produced Chilean blue mussel, Mytilus chilensis, was also studied. Following the eruption, a large phytoplankton bloom led to an increase in pHT, due to the uptake of dissolved-inorganic carbon in photic waters, potentially associated with the runoff of continental soil covered in volcanic ash. Indeed, high surface SO42− and GHG were observed to be associated with river discharges. No direct evidence of the eruption was observed within the carbonate system. Notwithstanding, a vertical pattern was observed, with an undersaturation of aragonite (ΩAr < 1) both in brackish surface (10 m), and saturated values in subsurface waters (3 to 7 m). Simultaneously, juvenile mussel shells showed maximized length and weight at 4 m depth. Results suggest a localized impact of the volcanic eruption on surface GHG, nutrients and short-term effects on the carbonate system. Optimal conditions for mussel calcification were identified within a subsurface refuge in the fjord. These specific attributes can be integrated into adaptation strategies by the mussel aquaculture industry to confront ocean acidification and changing runoff conditions.

Continue reading ‘Greenhouse gases, nutrients and the carbonate system in the Reloncaví Fjord (Northern Chilean Patagonia): implications on aquaculture of the mussel, Mytilus chilensis, during an episodic volcanic eruption’

Ocean acidification increases the accumulation of titanium dioxide nanoparticles (nTiO2) in edible bivalve mollusks and poses a potential threat to seafood safety

Large amounts of anthropogenic CO2 in the atmosphere are taken up by the ocean, which leads to ‘ocean acidification’ (OA). In addition, the increasing application of nanoparticles inevitably leads to their increased release into the aquatic environment. However, the impact of OA on the bioaccumulation of nanoparticles in marine organisms still remains unknown. This study investigated the effects of OA on the bioaccumulation of a model nanoparticle, titanium dioxide nanoparticles (nTiO2), in three edible bivalves. All species tested accumulated significantly greater amount of nTiO2 in pCO2-acidified seawater. Furthermore, the potential health threats of realistic nTiO2 quantities accumulated in bivalves under future OA scenarios were evaluated with a mouse assay, which revealed evident organ edema and alterations in hematologic indices and blood chemistry values under future OA scenario (pH at 7.4). Overall, this study suggests that OA would enhance the accumulation of nTiO2 in edible bivalves and may therefore increase the health risk for seafood consumers.

Continue reading ‘Ocean acidification increases the accumulation of titanium dioxide nanoparticles (nTiO2) in edible bivalve mollusks and poses a potential threat to seafood safety’

Seawater acidification increases copper toxicity: a multi-biomarker approach with a key marine invertebrate, the Pacific Oyster Crassostrea gigas

Highlights

• Cu concentration was elevated in Cu-exposed oysters under OA.
• Seawater acidification could exacerbate the toxicity caused by Cu in oysters.
• Disturbed physiological functions were observed in oysters under Cu and/or OA.
• IBR results suggested that co-exposure was the most stressful condition.

Abstract

Ocean acidification (OA) has been found to increase the release of free Cu2+ in seawater. However, only a handful of studies have investigated the influence of OA on Cu accumulation and cellular toxicity in bivalve species. In this study, Pacific oysters, Crassostrea gigas, were exposed to 25 μg/L Cu2+ at three pH levels (8.1, 7.8 and 7.6) for 14 and 28 days. Physiological and histopathological parameters [(clearance rate (CR), respiration rate (RR), histopathological damage and condition index (CI)), oxidative stress and neurotoxicity biomarkers [superoxide dismutase (SOD) and glutathione transferase (GST) activities, lipid peroxidation (LPO) and acetylcholinesterase (AChE) activity], combined with glycolytic enzyme activities [pyruvate kinase (PK) and hexokinase (HK)] were investigated in C. gigas. The bioconcentration of Cu was increased in soft tissues of Cu-exposed oysters under OA. Our results suggest that both OA and Cu could lead to physiological disturbance, oxidative stress, cellular damage, disturbance in energy metabolism and neurotoxicity in oysters. The inhibited CR, increased glycolytic enzymes activities and decreased CI suggested that the energy metabolism strategy adopted by oysters was not sustainable in the long term. Furthermore, integrated biomarker response (IBR) results found that OA and Cu exposure lead to severe stress to oysters, and co-exposure was the most stressful condition. Results from this study highlight the need to include OA in future environmental assessments of pollutants and hazardous materials to better elucidate the risks of those environmental perturbations.

Continue reading ‘Seawater acidification increases copper toxicity: a multi-biomarker approach with a key marine invertebrate, the Pacific Oyster Crassostrea gigas’

Future ocean warming may prove beneficial for the northern population of European seabass, but ocean acidification does not

The world’s oceans are acidifying and warming due to increasing amounts of atmospheric CO2. Thermal tolerance of fish much depends on the cardiovascular ability to supply the tissues with oxygen. The heart itself is highly dependent on oxygen and heart mitochondria thus might play a key role in shaping an organism’s tolerance to temperature. The present study aimed to investigate the effects of acute and chronic warming on respiratory capacities of European sea bass (Dicentrarchus labrax L.) heart mitochondria. We hypothesized that acute warming would impair mitochondrial respiratory capacities, but be compensated after long-term. Increasing PCO2 may cause intracellular changes, likely further constricting cellular energy metabolism. We found increased leak respiration rates in acutely warmed heart mitochondria of cold-conditioned fish in comparison to measurements at their rearing temperature, suggesting a lower aerobic capacity to synthesize ATP. However, thermal acclimation led to increased mitochondrial functionality, e.g. higher RCRo in heart mitochondria of warm-conditioned compared to cold-conditioned fish. Exposure to high PCO2 synergistically amplified the effects of acute and long-term warming, but did not result in changes by itself. We explained the high ability to maintain mitochondrial function under OA with the fact that seabass are moving between various environmental conditions. Improved mitochondrial capacities after warm conditioning could be due to the origin of this species in the warm waters of the Mediterranean. Our results also indicate that seabass are not yet fully adapted to the colder temperatures in their northern distribution range and might benefit from warmer temperatures.

Continue reading ‘Future ocean warming may prove beneficial for the northern population of European seabass, but ocean acidification does not’

Saxitoxin and tetrodotoxin bioavailability increases in future oceans

Increasing atmospheric levels of carbon dioxide are largely absorbed by the world’s oceans, decreasing surface water pH. In combination with increasing ocean temperatures, these changes have been identified as a major sustainability threat to future marine life. Interactions between marine organisms are known to depend on biomolecules, but the influence of oceanic pH on their bioavailability and functionality remains unexplored. Here we show that global change significantly impacts two ecological keystone molecules in the ocean, the paralytic toxins saxitoxin (STX) and tetrodotoxin (TTX). Increasing temperatures and declining pH increase the abundance of the toxic forms of these two neurotoxins in the water. Our geospatial global model highlights where this increased toxicity could intensify the devastating impact of harmful algal blooms on ecosystems in the future, for example through an increased incidence of paralytic shellfish poisoning (PSP). We also use these results to calculate future saxitoxin toxicity levels in Alaskan clams, Saxidomus gigantea, showing critical exceedance of limits save for consumption. Our findings for TTX and STX exemplarily highlight potential consequences of changing pH and temperature on chemicals dissolved in the sea. This reveals major implications not only for ecotoxicology, but also for chemical signals mediating species interactions such as foraging, reproduction, or predation in the ocean with unexplored consequences for ecosystem stability and ecosystem services.

Continue reading ‘Saxitoxin and tetrodotoxin bioavailability increases in future oceans’

Physiological and biochemical responses of Thalassiosira weissflogii (diatom) to seawater acidification and alkalization

Increasing atmospheric pCO2 leads to seawater acidification, which has attracted considerable attention due to its potential impact on the marine biological carbon pump and function of marine ecosystems. Alternatively, phytoplankton cells living in coastal waters might experience increased pH/decreased pCO2 (seawater alkalization) caused by metabolic activities of other photoautotrophs, or after microalgal blooms. Here we grew Thalassiosira weissflogii (diatom) at seven pCO2 levels, including habitat-related lowered levels (25, 50, 100, and 200 µatm) as well as present-day (400 µatm) and elevated (800 and 1600 µatm) levels. Effects of seawater acidification and alkalization on growth, photosynthesis, dark respiration, cell geometry, and biogenic silica content of T. weissflogii were investigated. Elevated pCO2 and associated seawater acidification had no detectable effects. However, the lowered pCO2 levels (25 ∼ 100 µatm), which might be experienced by coastal diatoms in post-bloom scenarios, significantly limited growth and photosynthesis of this species. In addition, seawater alkalization resulted in more silicified cells with higher dark respiration rates. Thus, a negative correlation of biogenic silica content and growth rate was evident over the pCO2 range tested here. Taken together, seawater alkalization, rather than acidification, could have stronger effects on the ballasting efficiency and carbon export of T. weissflogii.

Continue reading ‘Physiological and biochemical responses of Thalassiosira weissflogii (diatom) to seawater acidification and alkalization’


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