Posts Tagged 'physiology'

Photoprotective responses in a brown macroalgae Cystoseira tamariscifolia to increases in CO2 and temperature

Global warming and ocean acidification are increasingly affecting coastal ecosystems, with impacts that vary regionally depending upon local biogeography. Ocean acidification drives shifts in seaweed community dominance that depend on interactions with other factors such as light and nutrients. In this study, we investigated the photophysiological responses in the brown macroalgae species Cystoseira tamariscifolia (Hudson) Papenfuss with important structural role in the coastal Mediterranean communities. These algae were collected in the Cabo de Gata-Nijar Natural Park in ultraoligotrophic waters (algae exposed under high irradiance and less nutrient conditions) vs. those collected in the La Araña beach in oligotrophic waters (algae exposed at middle nutrient and irradiance conditions) in the Mediterranean Sea. They were incubated in mesocosms, under two levels of CO2; ambient (400-500 ppm) and high CO2 (1200-1300 ppm), combined with two temperatures (ambient temperature; 20 °C and ambient temperature + 4 °C; 24 °C) and the same nutrient conditions of the waters of the origin of macroalgae. Thalli from two sites on the Spanish Mediterranean coast were significantly affected by increases in pCO2 and temperature. The carotenoids (fucoxanthin, violaxanthin and β-carotene) contents were higher in algae from oligotrophic than that from ultraoligotrophic water, i.e., algae collected under higher nutrient conditions respect to less conditions, increase photoprotective pigments content. Thalli from both locations upregulated photosynthesis (as Fv/Fm) at increased pCO2 levels. Our study shows that ongoing ocean acidification and warming can increase photoprotection and photosynthesis in intertidal macroalgae.

Continue reading ‘Photoprotective responses in a brown macroalgae Cystoseira tamariscifolia to increases in CO2 and temperature’

Influence of environmental conditions on the toxicokinetics of cadmium in the marine copepod Acartia tonsa

Marine and estuarine ecosystems are highly productive areas that often act as a final sink for several pollutants, such as cadmium. Environmental conditions in these habitats can affect metal speciation, as well as its uptake and depuration by living organisms. The aim of this study was to assess cadmium uptake and depuration rates in the euryhaline calanoid copepod Acartia tonsa under different pH, salinity and temperature conditions. Cadmium speciation did not vary with changing pH or temperature, but varied with salinity. Free Cd2+ ion activity increased with decreasing salinities resulting in increased cadmium concentrations in A. tonsa. However, uptake rate, derived using free Cd2+ ion activity, showed no significant differences at different salinities indicating a simultaneous combined effect of Cd2+ speciation and metabolic rates for osmoregulation. Cadmium concentration in A. tonsa and uptake rate increased with increasing pH, showing a peak at the intermediate pH of 7.5, while depuration rate fluctuated, thus suggesting that both parameters are mediated by metabolic processes (to maintain homeostasis at pH levels lower than normal) and ion competition at membrane binding sites. Cadmium concentration in A. tonsa, uptake and depuration rates increased with increasing temperature, a trend that can be attributed to an increase in metabolic energy demand at higher temperatures. The present study shows that cadmium uptake and depuration rates in the marine copepod A. tonsa is mostly affected by biological processes, mainly driven by metabolic mechanisms, and to a lesser extent by metal speciation in the exposure medium.

Continue reading ‘Influence of environmental conditions on the toxicokinetics of cadmium in the marine copepod Acartia tonsa’

Ocean acidification alters the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and gene expression of a bivalve species, Sinonovacula constricta

Although the impacts of ocean acidification on fertilization, embryonic development, calcification, immune response, and behaviour have been well studied in a variety of marine organisms, the physiological and molecular mechanism manifesting acidification stress on behavioural response remains poorly understood. Therefore, the impacts of future ocean acidification scenarios (pH at 7.8, 7.6, and 7.4) on the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and expression of energy-producing-related genes of the razor clam Sinonovacula constricta were investigated in the present study. The results showed that elevated CO2 partial pressure ( pCO2) (pH at 7.6 and 7.4) led to a significant reduction in the digging depth of the razor clam. In addition, exposure to pCO2-acidified seawater depressed the metabolism and activity of Ca2+/Mg2+-ATPase, which may partially contribute to the reduced digging depth detected. Furthermore, the expression of energy-producing-related genes was generally induced by exposure to acidified seawater and could be accounted for by an increased energy demand under acidification stress. The results obtained suggest ocean acidification may exert a behavioural impact through altering physiological condition in the razor clam.

Continue reading ‘Ocean acidification alters the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and gene expression of a bivalve species, Sinonovacula constricta’

Effects of ocean acidification and eutrophication on the macroalgae Ulva spp.

Ocean acidification is the increased absorption of atmospheric CO2 in seawater and the consequent decrease in pH. This phenomenon is occurring throughout the global oceans while land use changes and large human populations near coasts are linked to increased nutrient concentrations in seawater. Ulva spp. blooms caused by nutrient enrichment occur regularly in some parts of the world and are known as green tides. There is concern that ocean acidification may increase green tides and intensify ecological and economic damages. Ulva spp. can utilize bicarbonate (HCO3-) as an inorganic carbon source, but this comes at an energetic cost as HCO3- must be converted to CO2 before it can be used for carbon fixation. Therefore, increased utilization of pCO2 with ocean acidification may benefit Ulva spp. Ocean acidification and eutrophication will occur simultaneously in many coastal ecosystems. The goal of the following investigations was to determine the effects of ocean acidification and nutrient enrichment alone and their interaction on photosynthetic, nutrient, and growth physiology of Ulva spp. In Chapter 2, the response of Ulva australis to pHT and ammonium (NH4+) enrichment were investigated in a seven day growth experiment using a range of pHT (7.56 – 7.84) and ambient and enriched NH4+ concentrations. I measured relative growth rates (RGRs), NH4+ uptake rates and pools, photosynthetic characteristics, and tissue carbon and nitrogen content. There was no interaction of pHT and NH4+ enrichment on the physiological parameters. The RGR was not affected by pHT, but was an average of two times higher in the enriched NH4+ treatment. rETRmax, total chlorophyll, and tissue nitrogen increased with both NH4+ enrichment and decreased pHT. The C:N ratio decreased with decreasing pH and with NH4+ enrichment. Although rETRmax increased and the C:N ratio decreased under decreased pH, these metabolic changes did not translate to higher growth rates. The results show that U. australis growth and physiology is more sensitive to NH4+ than it is to pH and that there is no interactive effect of NH4+ enrichment and decreasing pH. In Chapter 3, Ulva lactuca was grown for 22 days under a range of pCO2 and NH4+ concentrations and a multiple linear regression was used to analyze RGRs, NH4+ and NO3- pools, in situ NH4+ and NO3- uptake rates, tissue carbon and nitrogen content, carbohydrate and protein concentrations, and photosynthesis irradiance curves (P-I curves). The results from model selection and model-averaging techniques allowed me to make predictive models across a range of relevant ocean acidification and eutrophication scenarios and measure the effect sizes of pCO2, NH4+ enrichment, and their interaction. Overall, there was no effect of pCO2 and NH4+ on RGRs after day 5. However, there was a synergistic effect of pCO2 and NH4+ enrichment on the growth rates during days 0 – 5. When pCO2 and NH4+ concentrations increased simultaneously, NO3- uptake rates increased, which may have contributed to increased growth as seen in days 0 – 5. Maximum photosynthetic rates (Pmax) decreased with increasing pCO2 and there was a positive interaction of pCO2 and NH4+ on indicating CCMs were altered under these conditions. This shows that under high light intensities, Pmax was negatively affected by pCO2 and CCMs are not altered when nutrients are limited. Ultimately, there was no longer-term effect of ocean acidification and eutrophication on Ulva lactuca growth. Nutrient enrichment is a major cause of green tide blooms around the world and Ulva australis had the ability to enhance nutrient, photosynthetic, and growth physiology with NH4+ enrichment. Conversely, Ulva lactuca collected from a eutrophic environment, did not respond to NH4+ in terms of growth. Both chapters provided evidence that ocean acidification is unlikely to affect the growth rates of Ulva spp. However, the exception was a positive interactive effect of pCO2 and NH4+ enrichment on the growth rate of U. lactuca during the first five days, suggesting ocean acidification could play a role in initiating Ulva spp. blooms in a eutrophic environment. This could be an important consideration for determining how green tides will be affected by ocean acidification in coastal areas where nutrient enrichment occurs in pulses, resulting in transiently increased nitrogen concentrations.

Continue reading ‘Effects of ocean acidification and eutrophication on the macroalgae Ulva spp.’

Genome-wide identification, characterization and expression analyses of TLRs in Yesso scallop (Patinopecten yessoensis) provide insight into the disparity of responses to acidifying exposure in bivalves


  • Eighteen TLR superfamily members were identified in the P. yessoensis genome.
  • Phylogenetic analysis confirmed duplication and expansion of TLR genes in mollusk.
  • The 18 PyTLRs showed different immune response patterns to acidifying exposure.
  • Adaptive recruitment of tandem duplication of TLR genes have been arisen to the immune stress.


Toll-like receptors (TLRs) play a crucial role in innate immunity by recognizing specific pathogen-associated molecular patterns, including lipoproteins, lipopeptides, lipopolysaccharide, flagellin, dsRNA, ssRNA and CpG DNA motifs. Although significant effects of TLRs on immunity have been reported in most vertebrates and some invertebrates, the complete TLR superfamily has not been systematically characterized in scallops. In this study, 18 TLR genes were identified from Yesso scallop (Patinopecten yessoensis) using whole-genome scanning. Phylogenetic and protein structural analyses were performed to determine the identities and evolutionary relationships of the 18 genes. Extensive expansion of TLR genes from the Yesso scallop genome indicated gene duplication events. In addition, expression profiling of PyTLRs was performed at different acidifying exposure levels (pH = 6.50, 7.50) with different challenge durations (3, 6, 12 and 24 h) via in silico analysis using transcriptome and genome databases. Our results confirmed the inducible expression patterns of PyTLRs under acidifying exposure, and the responses to immune stress may have arisen through adaptive recruitment of tandem duplications of TLR genes. Collectively, this study provides novel insight into PyTLRs as well as the specific role and response of TLR signaling pathways in host immune responses against acidifying exposure in bivalves.


Continue reading ‘Genome-wide identification, characterization and expression analyses of TLRs in Yesso scallop (Patinopecten yessoensis) provide insight into the disparity of responses to acidifying exposure in bivalves’

Effects of hypoxia and ocean acidification on the upper thermal niche boundaries of coral reef fishes

Rising ocean temperatures are predicted to cause a poleward shift in the distribution of marine fishes occupying the extent of latitudes tolerable within their thermal range boundaries. A prevailing theory suggests that the upper thermal limits of fishes are constrained by hypoxia and ocean acidification. However, some eurythermal fish species do not conform to this theory, and maintain their upper thermal limits in hypoxia. Here we determine if the same is true for stenothermal species. In three coral reef fish species we tested the effect of hypoxia on upper thermal limits, measured as critical thermal maximum (CTmax). In one of these species we also quantified the effect of hypoxia on oxygen supply capacity, measured as aerobic scope (AS). In this species we also tested the effect of elevated CO2 (simulated ocean acidification) on the hypoxia sensitivity of CTmax. We found that CTmax was unaffected by progressive hypoxia down to approximately 35 mmHg, despite a substantial hypoxia-induced reduction in AS. Below approximately 35 mmHg, CTmax declined sharply with water oxygen tension (PwO2). Furthermore, the hypoxia sensitivity of CTmax was unaffected by elevated CO2. Our findings show that moderate hypoxia and ocean acidification do not constrain the upper thermal limits of these tropical, stenothermal fishes.

Continue reading ‘Effects of hypoxia and ocean acidification on the upper thermal niche boundaries of coral reef fishes’

Trade-offs in a high CO2 habitat on a subsea volcano: condition and reproductive features of a bathymodioline mussel

Northwest Eifuku submarine volcano (Mariana Volcanic Arc) emits very high concentrations of CO2 at a vent where the mussel Bathymodiolus septemdierum experiences pH as low as 5.2. We examined how this natural setting of high pCO2 influences shell, body, and reproductive condition. Calcification is highly compromised: at a given shell volume, shells from NW Eifuku weigh about half those from reference sites in the south Pacific, and dissolution of the inner shell is evident. However, the condition indices of some NW Eifuku mussels were equal to or higher than those from Lau back-arc basin and the New Hebrides Island Arc. NW Eifuku mussels in pH 5.2 fluids had the highest symbiont abundances in gill bacteriocytes, probably due to greater dissolved sulphide access. Excess energy demands imposed by high pCO2 conditions appears moderated by adequate food availability through symbiont chemosynthesis. In the sample with the lowest body condition, gametogenesis was lagging, although all mussels in high pCO2 had developing gonads and the complete gametogenic cycle was present in our samples. Gamete development is synchronous between sexes and is possibly periodic. While mussels are functionally dioecious, protogynous hermaphroditism can occur—a first record for the genus—which may be an adaptation to resource availability. B. septemdierum likely makes energy allocation trade-offs among calcification, body mass maintenance, reproduction and other processes to maximize fitness. We suggest that flexibility to divert energy from shell formation, combined with good food supply, can mitigate the manifestation of high CO2 stress on B. septemdierum.

Continue reading ‘Trade-offs in a high CO2 habitat on a subsea volcano: condition and reproductive features of a bathymodioline mussel’

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Ocean acidification in the IPCC AR5 WG II

OUP book