Posts Tagged 'growth'

Diel transcriptional oscillations of a plastid antiporter reflect increased resilience of Thalassiosira pseudonana in elevated CO2

Acidification of the ocean due to high atmospheric CO2 levels may increase the resilience of diatoms causing dramatic shifts in abiotic and biotic cycles with lasting implications on marine ecosystems. Here, we report a potential bioindicator of a shift in the resilience of a coastal and centric model diatom Thalassiosira pseudonana under elevated CO2. Specifically, we have discovered, through EGFP-tagging, a plastid membrane localized putative Na+(K+)/H+ antiporter that is significantly upregulated at >800 ppm CO2, with a potentially important role in maintaining pH homeostasis. Notably, transcript abundance of this antiporter gene was relatively low and constant over the diel cycle under contemporary CO2 conditions. In future acidified oceanic conditions, dramatic oscillation with >10-fold change between nighttime (high) and daytime (low) transcript abundances of the antiporter was associated with increased resilience of T. pseudonana. By analyzing metatranscriptomic data from the Tara Oceans project, we demonstrate that phylogenetically diverse diatoms express homologs of this antiporter across the globe. We propose that the differential between night- and daytime transcript levels of the antiporter could serve as a bioindicator of a shift in the resilience of diatoms in response to high CO2 conditions in marine environments.

Continue reading ‘Diel transcriptional oscillations of a plastid antiporter reflect increased resilience of Thalassiosira pseudonana in elevated CO2’

Combined effects of ocean acidification and elevated temperature on feeding, growth, and physiological processes of Antarctic krill Euphausia superba

Antarctic krill Euphausia superba is a key species in the Southern Ocean, where its habitat is projected to undergo continued warming and increases in pCO2. Experiments during 2 summer field seasons at Palmer Station, Antarctica, investigated the independent and interactive effects of elevated temperature and pCO2 (decreased pH) on feeding, growth, acid-base physiology, metabolic rate, and survival of adult Antarctic krill. Ingestion and clearance rates of chlorophyll were depressed under low pH (7.7) compared to ambient pH (8.1) after a 48 h acclimation period, but this difference disappeared after a 21 d acclimation. Growth rates were negligible and frequently negative, but were significantly more negative at high (3°C, -0.03 mm d-1) compared to ambient temperature (0°C, -0.01 mm d-1) with no effect of pH. Modest elevations in tissue total CO2 and tissue pH were apparent at low pH but were short-lived. Metabolic rate increased with temperature but was suppressed at low pH in smaller but not larger krill. Although effects of elevated temperature and/or decreased pH were mostly sublethal, mortality was higher at high temperature/low pH (58%) compared to ambient temperature/pH or ambient temperature/low pH (>90%). This study identified 3 dominant patterns: (1) shorter-term effects were primarily pH-dependent; (2) krill compensated for lower pH relatively quickly; and (3) longer-term effects on krill growth and survival were strongly driven by temperature with little to no pH effect.

Continue reading ‘Combined effects of ocean acidification and elevated temperature on feeding, growth, and physiological processes of Antarctic krill Euphausia superba’

Elevated CO2 influences competition for growth, photosynthetic performance and biochemical composition in Neopyropia yezoensis and Ulva prolifera

Highlights

  • The growth of Neopyropia yezoensis was significantly inhibited by Ulva prolifera.
  • Elevated CO2 enhanced the resistance of N. yezoensis to the effect of U. prolifera.
  • Elevated CO2 increased the competitive ability of U. prolifera.

Abstract

The occurrence of various marine macroalgae in the same niche will inevitably lead to interspecific competition due to similar environmental requirements. With the increasing global atmospheric CO2 concentration, the resulting ocean acidification can potentially influence competition among macroalgae in the future. Neopyropia yezoensis (Rhodophyta, formerly Pyropia yezoensis) and the epiphytic alga Ulva prolifera (Chlorophyta) were selected for investigating competition among macroalgae grown under different CO2 conditions. The results showed that when cultured with U. proliferaN. yezoensis‘ growth rate was significantly inhibited along with a sharp decrease in net photosynthetic rate. Although CO2 decreased the growth rate of N. yezoensis, it enhanced the resistance of the alga to the allelopathic effect of U. prolifera. While no difference was found between U. prolifera grown in monoculture and biculture, strong competitive ability was observed. CO2 could enhance this ability with higher net photosynthetic rate. However, CO2 significantly inhibited the carotenoid synthesis in both plants. This inhibition in N. yezoensis was more pronounced in the presence of U. prolifera. Biculture promoted the accumulation of soluble protein in N. yezoensis while it inhibited the process in U. prolifera. In addition, it enhanced the inhibitory effect of acidification on soluble carbohydrates of both plants. Elevated CO2 levels alleviated the competition between N. yezoensis and U. prolifera, but the latter can become the more competitive epiphytic alga which can impact the future of nori culture.

Continue reading ‘Elevated CO2 influences competition for growth, photosynthetic performance and biochemical composition in Neopyropia yezoensis and Ulva prolifera’

Epiphytic hydroids on Posidonia oceanica seagrass meadows are winner organisms under future ocean acidification conditions: evidence from a CO2 vent system (Ischia Island, Italy)

Effects of ocean acidification (OA) on the plant phenology and colonization/settlement pattern of the hydrozoan epibiont community of the leaves of the seagrass Posidonia oceanica have been studied at volcanic CO2 vents off Ischia (Italy). The study was conducted in shallow Posidonia stands (2.5–3.5 m depth), in three stations on the north and three on the south sides of the vent’s area (Castello Aragonese vents), distributed along a pH gradient. At each station, 10–15 P. oceanica shoots were collected every three months for one-year cycle (Sept 2009–2010). The shoot density of Posidonia beds in the most acidified stations along the gradient (pH < 7.4) was significantly higher than that in the control area (pH = 8.10). On the other hand, we recorded lower leaf lengths and widths in the acidified stations in the whole year of observations, compared to those in the control stations. However, the overall leaf surface (Leaf Area Index) available for epiphytes under ocean acidification conditions was higher on the south side and on both the most acidified stations because of the higher shoot density under OA conditions. The hydrozoan epibiont community on the leaf canopy accounted for seven species, three of which were relatively abundant and occurring all year around (Sertularia perpusilla, Plumularia obliqua, Clytia hemisphaerica). All hydroids species showed a clear tolerance to low pH levels, including chitinous and non-calcifying forms, likely favoured also by the absence of competition for substratum with the calcareous forms of epiphytes selected against OA.

Continue reading ‘Epiphytic hydroids on Posidonia oceanica seagrass meadows are winner organisms under future ocean acidification conditions: evidence from a CO2 vent system (Ischia Island, Italy)’

Impacts of plastic-made packaging on marine key species: effects following water acidification and ecological implications

This study evaluates the impacts of 16 different leachates of plastic-made packaging on marine species of different trophic levels (bacteria, algae, echinoderms). Standard ecotoxicological endpoints (inhibition of bioluminescence, inhibition of growth, embryo-toxicity) and alterations of ecologically significant parameters (i.e., echinoderms’ body-size) were measured following exposure under different pH water conditions: marine standard (pH 8.1) and two increasingly acidic conditions (pH 7.8 and 7.5) in order to evaluate possible variations induced by ocean acidification. The results obtained in this study evidence that the tested doses are not able to significantly affect bacteria (Vibrio fischeri) and algae (Phaeodactylum tricornutum). On the contrary, Paracentrotus lividus larvae were significantly affected by several packaging types (13 out of 16) with meaningless differences between pH conditions.

Continue reading ‘Impacts of plastic-made packaging on marine key species: effects following water acidification and ecological implications’

Parental whole life cycle exposure modulates progeny responses to ocean acidification in slipper limpets

Multigenerational exposure is needed to assess the evolutionary potential of organisms in the rapidly changing seascape. Here, we investigate if there is a transgenerational effect of ocean acidification exposure on a calyptraeid gastropod such that long‐term exposure elevates offspring resilience. Larvae from wild type Crepidula onyx adults were reared from hatching until sexual maturity for over 36 months under three pH conditions (pH 7.3, 7.7, and 8.0). While the survivorship, growth, and respiration rate of F1 larvae were unaffected by acute ocean acidification (OA), long‐term and whole life‐cycle exposure significantly compromised adult survivorship, growth, and reproductive output of the slipper limpets. When kept under low pH throughout their life cycle, only 6% of the F1 slipper limpets survived pH 7.3 conditions after ~2.5 years and the number of larvae they released was ~10% of those released by the control. However, the F2 progeny from adults kept under the long‐term low pH condition hatched at a comparable size to those in medium and control pH conditions. More importantly, these F2 progeny from low pH adults outperformed F2 slipper limpets from control conditions; they had higher larval survivorship and growth, and reduced respiration rate across pH conditions, even at the extreme low pH of 7.0. The intragenerational negative consequences of OA during long‐term acclimation highlights potential carryover effects and ontogenetic shifts in stress vulnerability, especially prior to and during reproduction. Yet, the presence of a transgenerational effect implies that this slipper limpet, which has been widely introduced along the West Pacific coasts, has the potential to adapt to rapid acidification.

Continue reading ‘Parental whole life cycle exposure modulates progeny responses to ocean acidification in slipper limpets’

Microalgal photosynthesis induces alkalization of aquatic environment as a result of H+ uptake independently from CO2 concentration – new perspectives for environmental applications

Highlights

  • Microalgae photosynthesis induces strongly H+ uptake reversing ocean acidification.
  • Water alkalization through algal H+ uptake is independent from CO2 concentration.
  • New management approaches for reversing ocean acidification using algal H+ uptake.
  • Algal H+ uptake depends on essential nutrients, cell density and light intensity.
  • Acidification of aquatic environment induces microalgal photosynthesis and growth.

Abstract

The photosynthetic process in microalgae and the extracellular proton environment interact with each other. The photosynthetic process in microalgae induces a pH increase in the aquatic environment as a result of cellular protons uptake rather than as an effect of CO2 consumption. The photosynthetic water photolysis and the reduction/oxidation cycle of the plastoquinone pool provide lumen with protons. Weak bases act as “permeant buffers” in lumen during the photosynthetic procedure, converting the ΔpH to Δψ. This is possibly the main reason for continuous light-driven proton uptake from the aquatic environment through cytosol and stroma, into the lumen. The proton uptake rate and, therefore, the microalgal growth is proportional to the light intensity, cell concentration, and extracellular proton concentration. The low pH in microalgae cultures, without limitation factors related to light and nutrients, strongly induces photosynthesis (and proton uptake) and, consequently, growth. In contrast, the mitochondrial respiratory process, in the absence of photosynthetic activity, does not substantially alter the culture pH. Only after intensification of the respiratory process, using exogenous glucose supply leads to significantly reduced pH values in the culture medium, almost exclusively through proton output. Enhanced dissolution of atmospheric CO2 in water causes the phenomenon of ocean acidification, which prevents the process of calcification, a significant process for numerous phytoplankton and zooplankton organisms, as well for corals. The proposed interaction between microalgal photosynthetic activity and proton concentration in the aquatic environment, independently from the CO2 concentration, paves the way for new innovative management strategies for reversing the ocean acidification.

Continue reading ‘Microalgal photosynthesis induces alkalization of aquatic environment as a result of H+ uptake independently from CO2 concentration – new perspectives for environmental applications’

Combined effect of microplastics and global warming factors on early growth and development of the sea urchin (Paracentrotus lividus)

Highlights

  • This work focusses on the effect of a multi-stressor environment in sea urchin.
  • Embryo-larval bioassays were used to determine growth and morphometric parameters.
  • A lower water pH (7.6) reduced larval growth and caused deformities.
  • Microplastics aggravate the effect of water acidification in sea urchin larvae.
  • High temperatures caused an additional stress and reduced larvae stomach volume.

Abstract

The aim of this work was to estimate the potential risk of the combined effect of global change factors (acidification, temperature increase) and microplastic (MP) pollution on the growth and development of the sea urchin P. lividus. Embryo-larval bioassays were conducted to determine growth and morphology after 48 h of incubation with MP (1000 and 3000 particles/mL); with filtered sea water at pH = 7.6; and with their combinations. A second experiment was conducted to study the effect of pH and MP in combination with a temperature increase of 4 °C compared to control (20 °C). We found that the inhibition of growth in embryos reared at pH = 7.6 was around 75%. Larvae incubated at 3000 MP particles/mL showed a 20% decrease in growth compared to controls. The exposure to MP also induced an increase in the postoral arm separation or rounded vertices. The combined exposure to a pH 7.6 and MP caused a significant decrease of larval growth compared to control, to MP and to pH 7.6 treatments. Morphological alterations were observed in these treatments, including the development of only two arms. Increasing the temperature resulted in an increased growth in control, in pH 7.6 and pH 7.6 + MP3000 treatments, but the relative stomach volume decreased. However, when growth parameters were expressed per Degree-Days the lower growth provoked by the thermal stress was evidenced in all treatments. In this work we demonstrated that MP could aggravate the effect of a decreased pH and that an increase in water temperature generated an additional stress on P. lividus larvae, manifested in a lower growth and an altered development. Therefore, the combined stress caused by ocean warming, ocean acidification, and microplastic pollution, could threaten sea urchin populations leading to a potential impact on coastal ecosystems.

Continue reading ‘Combined effect of microplastics and global warming factors on early growth and development of the sea urchin (Paracentrotus lividus)’

Transgenerational responses to seawater pH in the edible oyster, with implications for the mariculture of the species under future ocean acidification

Highlights

• Larval offspring of C. hongkongensis were resilient to OA exposure

• Phenotypic traits in out-planted juveniles improved with parental exposure

• Positive carry-over effect from exposed parents persisted and manifested in the estuary

• Linking multiple life stages is vital to assess OA-induced carry-over capacity

• OA exposure at early life stages revealed potential mariculture application and species fitness

Abstract

The majority of common edible oysters are projected to grow more slowly and have smaller impaired shells because of anthropogenic CO2-induced reductions in seawater carbonate ion concentration and pH, a process called ocean acidification (OA). Recent evidence has shown that OA has carryover effects, for example, larvae exposed to OA will also exhibit either positive or negative effects after metamorphosis. This study examined the hidden carryover effects of OA exposure during parental and larval stages on post-metamorphic traits of the commercially important oyster species Crassostrea hongkongensis. Adults of C. hongkongensis were exposed to control pH (pHNBS 8.0) and OA-induced low pH (pHNBS 7.4) conditions. Their larval offspring were then exposed to the same aquarium conditions before being out-planted as post-metamorphic juveniles at a mariculture site for 10 months. Initially, larval offspring were resilient to low pH with or without parental exposure. The larvae exposed to low pH had significantly faster development and higher percentage of settlement success compared to control groups. The out-planted juveniles with parental exposure had improved survival and growth compared to juveniles without parental exposure, regardless of the larval exposure history. This implies that transgenerational effects due to parental exposure not only persists but also have a greater influence than the within-generational effects of larval exposure. Our results shed light on the importance of linking the various life history stages when assessing the OA-induced carryover capacity of C. hongkongensis in the natural environment. Understanding these linked relationships helps us better predict the species rapid adaptation responses in the face of changing coastal conditions due to OA.

Continue reading ‘Transgenerational responses to seawater pH in the edible oyster, with implications for the mariculture of the species under future ocean acidification’

Impact of increased nutrients and lowered pH on photosynthesis and growth of three marine phytoplankton communities from the coastal South West Atlantic (Patagonia, Argentina)

Effect of global change variables on the structure and photosynthesis of phytoplankton communities was evaluated in three different sites of the Patagonian coast of Argentina: enclosed bay (Puerto Madryn, PM), estuarine (Playa Unión, PU), and open waters (Isla Escondida, IE). We exposed samples to two contrasting scenarios: Present (nutrients at in situ levels) vs. Future (with lowered pH and higher nutrients inputs), and determined growth and photosynthetic responses after 2 days of acclimation. Under the Future condition phytoplankton growth was higher in the estuarine site compared to those in PM and IE. This effect was the most pronounced on large diatoms. While the increase of photosynthetic activity was not always observed in the Future scenario, the lower photosynthetic electron requirement for carbon fixation (Φe,C = ETR/PmB) in this scenario compared to the Present, suggests a more effective energy utilization. Long-term experiments were also conducted to assess the responses along a 4 days acclimation period in PU. Diatoms benefited from the Future conditions and had significantly higher growth rates than in the Present. In addition, Φe,C was lower after the acclimation period in the Future scenario, compared to the Present. Our results suggest that the availability, frequency and amount of nutrients play a key role when evaluating the effects of global change on natural phytoplankton communities. The observed changes in diatom growth under the Future scenario in PU and IE and photosynthesis may have implications in the local trophodynamics by bottom up control.

Continue reading ‘Impact of increased nutrients and lowered pH on photosynthesis and growth of three marine phytoplankton communities from the coastal South West Atlantic (Patagonia, Argentina)’

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Ocean acidification in the IPCC AR5 WG II

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