Posts Tagged 'temperature'

A triple threat: ocean warming, acidification and rare earth elements exposure triggers a superior antioxidant response and pigment production in the adaptable Ulva rigida

Highlights

  • La and Gd were accumulated in 24h;
  • Elimination of La and Gd did not occur in U. rigida;
  • La and Gd showed different accumulation and elimination patterns in future predicted scenarios;
  • La and Gd triggered an efficient antioxidant defence response in U. rigida;
  • REE and climate change exposure requested a superior antioxidant response.

Abstract

Anthropogenic increased atmospheric CO2 concentrations will lead to a drop of 0.4 units of seawater pH and ocean warming up to 4.8°C by 2100. Contaminant’s toxicity is known to increase under a climate change scenario. Rare earth elements (REE) are emerging contaminants, that until now have no regulation regarding maximum concentration and discharge into the environment and have become vital to new technologies such as electric and hybrid-electric vehicle batteries, wind turbine generators and low-energy lighting. Studies of REE, namely Lanthanum (La) and Gadolinium (Gd), bioaccumulation, elimination, and toxicity in a multi-stressor environment (e.g., warming and acidification) are lacking. Hence, we investigated the algae phytoremediation capacity, the ecotoxicological responses and total chlorophyll and carotenoid contents in Ulva rigida during 7 days of co-exposure to La or Gd (15 µg L−1 or 10 µg L−1, respectively), and warming and acidification. Additionally, we assessed these metals elimination, after a 7-day phase. After one day of experiment La and Gd clearly showed accumulation/adsorption in different patterns, at future conditions. Unlikely for Gd, Warming and Acidification contributed to the lowest La accumulation, and increased elimination. Lanthanum and Gd triggered an adequate activation of the antioxidant defence system, by avoiding lipid damage. Nevertheless, REE exposure in a near-future scenario triggered an overproduction of ROS that requested an enhanced antioxidant response. Additionally, an increase in total chlorophyll and carotenoids could also indicate an unforeseen energy expense, as a response to a multi-stressor environment.

Continue reading ‘A triple threat: ocean warming, acidification and rare earth elements exposure triggers a superior antioxidant response and pigment production in the adaptable Ulva rigida’

Understanding the impacts of environment and parasitism on Eastern oyster (Crassostrea virginica) vulnerability to ocean acidification

The global process of ocean acidification caused by the absorption of increased atmospheric carbon dioxide decreases the concentration of carbonate ions and reduces the associated seawater saturation state (ΩCaCO3) – making it more energetically costly for marine calcifying organisms to build their shells or skeletons. Bivalves are particularly vulnerable to the adverse effects of ocean acidification on calcification, and they inhabit estuaries and coastal zones – regions most susceptible to ocean acidification. However, the response of an individual to elevated pCO2 can depend on the carbonate chemistry dynamics of its current environment and the environment of its parents. Additionally, an organism’s response to ocean acidification can depend on its ability to control the chemistry at the site of calcification. Biotic and abiotic stressors can modify bivalves’ control of calcifying fluid chemistry – known as extrapallial fluid (EPF). Understanding the responses of bivalves – which are foundation species – to ocean acidification is essential for predicting the impacts of oceanic change on marine communities. This dissertation uses a culturally, ecologically, and economically important bivalve in the northwest Atlantic – the Eastern oyster (Crassostrea virginica) – to explore the effects of environment and species interactions on responses to elevated pCO2.

Chapter 2 describes a field study that characterized diurnal and seasonal carbonate chemistry dynamics of two estuaries in the Gulf of Maine that support Eastern oyster populations. The estuaries were monitored at high temporal resolution (half-hourly) over four years (2018-2021) using pH and conductivity loggers. Measured pH, salinity, and temperature were used to calculate carbonate chemistry parameters. Both estuaries exhibited strong seasonal and diurnal fluctuations in carbonate chemistry. They also experienced pCO2 values that greatly exceeded current atmospheric carbon dioxide levels and those projected for the year 2100.

Chapter 3 describes a laboratory experiment that examined the capacity of intergenerational exposure to mitigate the adverse effects of ocean acidification on larval growth, shell morphology, and survival. Adult oysters were cultured in control or elevated pCO2 conditions for 30 days then crossed using a North Carolina II cross design. Larvae were grown for three days under control and elevated pCO2 conditions. Intergenerational exposure to elevated pCO2 conditions benefited early larval growth and shell morphology, but not survival. However, parental exposure was insufficient to completely counteract the adverse effects of the elevated pCO2 treatment on shell formation and survival.

Chapter 4 describes a laboratory experiment that examined the interplay between ocean acidification and parasite-host dynamics. Eastern oysters infested and not infested with bioeroding sponge (Cliona sp.) were cultured under three pCO2 conditions (539, 1040, 3294 ppm) and two temperatures (23, 27˚C) for 70 days to assess oyster control of EPF chemistry, growth, and survival. Bioeroding sponge infestation and elevated pCO2 reduced oyster net calcification and EPF pH but did not affect condition or survival. Infested oyster EPF pH was consistently lower than seawater pH, while EPF dissolved inorganic carbon was consistently elevated relative to seawater. These findings suggested that infested oysters effectively precipitated repair shell to prevent seawater intrusion into extrapallial fluid through bore holes across all treatments.

Chapter 5 characterizes the concentration of a suite of 56 elements normalized to calcium in EPF and shell of Crassostrea virginica grown under three pCO2 conditions (570, 990, 2912 ppm) and sampled at four timepoints (days 2, 9, 79, 101) to assess effects of pCO2 on organismal control of EPF and shell elemental composition and EPF-to-shell elemental partitioning. Elevated pCO2 significantly influenced the relative abundance of elements in the EPF (29) and shell (13) and altered EPF-to-shell elemental partitioning for 45 elements. Importantly, elevated pCO2 significantly influenced the concentration of several elements in C. virginica shell that are used in other biogenic carbonates as paleo-proxies for other environmental parameters. This result suggests that elevated pCO2 could influence the accuracy of paleo reconstructions.

Overall, this dissertation provides insights that can help improve our understanding of past, present, and future ocean environments. Understanding current local carbonate chemistry dynamics and the capacity for C. virginica to acclimate intergenerationally to elevated pCO2 can inform site and stock selection for aquaculture and restoration efforts. Studying parasite-host environment interactions provides critical insights into the potential for parasitism to alter responses to future ocean acidification. Finally, exploring the impact of elevated pCO2 on elemental composition of EPF and shell allowed us to understand better biomineralization processes, identify potential proxies for seawater pCO2 in bivalves, and offer insights that could help improve the accuracy of paleo reconstructions.

Continue reading ‘Understanding the impacts of environment and parasitism on Eastern oyster (Crassostrea virginica) vulnerability to ocean acidification’

Ocean acidification impacts fish larvae but warming could compensate juveniles

Related content

A related article has been published: Effects of ocean acidification over successive generations decrease resilience of larval European sea bass to ocean acidification and warming but juveniles could benefit from higher temperatures in the NE Atlantic

A 40 day old European sea bass (Dicentrarchus labrax) larva: Photo credit: Sarah Howald.

As we pump more CO2 into the atmosphere, the pH of the oceans is decreasing and although a reduction of 0.1 pH units may not sound much, the reality is that the acidity of the seas has increased by 30% since the start of the Industrial Revolution in the 18th century. But no one knew how much of an impact decreasing pH might have on long-lived fish species. ‘Fish had been thought to be less vulnerable to ocean acidification due to well-developed acid–base regulation systems’, says Sarah Howald from the Alfred Wegener Institute for Polar and Marine Research (AWI), Germany. However, scientists have recently discovered that fish larvae may be more vulnerable than thought. Some grew faster in more acidic waters, while others suffered tissue and hearing damage in addition to growing more slowly. Yet, no one knew how ocean acidification might impact subsequent generations. Felix Mark from AWI, with colleagues from Germany and France, embarked on an ambitious 5.5 year investigation to find out how European sea bass (Dicentrarchus labrax) larvae and their eventual offspring deal with acidic conditions.

In October 2013, at the Ifremer-Centre de Bretagne, France, Guy Claireaux (University of Brest, France), José Zambonino and David Mazurais (both from Ifremer), Myron Peck (University of Hamburg, Germany) and Mark allocated recently hatched sea bass larvae to small tanks of seawater pumped in from the Bay of Brest at summer temperatures (19°C) while other larvae lived in tanks of seawater where the acidity had been raised to 1700 μatm CO2, the IPCC’s prediction for seawater CO2 concentrations 120 years in the future. Once the larvae had developed into juveniles (∼2.5 months old), the team relocated the youngsters to larger cool (15°C) tanks, maintaining the two different pH levels until the fish were adult (spring 2017), when the researchers selected ∼30 adult fish each from the two water conditions to rehome in palatial 3000 l tanks. Then, in March 2018, the 5 year old adults spawned to produce the next generation of larvae. But this time the scientists added a twist, dividing the offspring of the parents from the modern day (current CO2) seawater conditions and those of the parents raised in the acidic future water conditions (1700 μatm CO2) into cool and warm tanks, to simulate climate change. Meanwhile, the team kept track of the first and the second generations as they grew and developed.

Initially, the first generation of sea bass youngsters didn’t seem to be affected by their acidic start in life and neither did their offspring. However, when the team altered the water temperature as the second generation developed in the acidic future water, they found the larvae from the warmer (20°C) tank were much smaller when they metamorphosed into juveniles than those in cool acidic seawater and those that developed in modern warm water. Mark suspects that the warmer high-CO2 conditions in the future could impair energy production by the youngsters’ mitochondria, limiting their growth. However, once the larvae developed into juvenile fish, they seemed to benefit, growing faster, although the team isn’t sure whether the warmth was accelerating the fish’s growth or whether the acidity failed to impair the growing juveniles.

The team warns that the faster growth of larvae in a warmer more acidic world could place them at risk if there is insufficient food for the rapidly growing youngsters. But it seems that if the youngsters develop successfully into juvenile fish, their chances may improve.

Continue reading ‘Ocean acidification impacts fish larvae but warming could compensate juveniles’

Effects of seawater pCO2 on the skeletal morphology of massive Porites spp. corals

Ocean acidification alters the dissolved inorganic carbon chemistry of seawater and can reduce the calcification rates of tropical corals. Here we explore the effect of altering seawater pCO2 on the skeletal morphology of 4 genotypes of massive Porites spp. which display widely different calcification rates. Increasing seawater pCO2 causes significant changes in in the skeletal morphology of all Porites spp. studied regardless of whether or not calcification was significantly affected by seawater pCO2. Both the median calyx size and the proportion of skeletal surface occupied by the calices decreased significantly at 750 µatm compared to 400 µatm indicating that polyp size shrinks in this genus in response to ocean acidification. The coenosteum, connecting calices, expands to occupy a larger proportion of the coral surface to compensate for this decrease in calyx area. At high seawater pCO2 the spines deposited at the skeletal surface became more numerous and the trabeculae (vertical skeletal pillars) became significantly thinner in 2 of the 4 genotypes. The effect of high seawater pCO2 is most pronounced in the fastest growing coral and the regular placement of trabeculae and synapticulae is disturbed in this genotype resulting in a skeleton that is more randomly organised. The study demonstrates that ocean acidification decreases the polyp size and fundamentally alters the architecture of the skeleton in this major reef building species from the Indo-Pacific Ocean.

Continue reading ‘Effects of seawater pCO2 on the skeletal morphology of massive Porites spp. corals’

Caribbean king crab larvae and juveniles show tolerance to ocean acidification and ocean warming

Coastal habitats are experiencing decreases in seawater pH and increases in temperature due to anthropogenic climate change. The Caribbean king crab, Maguimithrax spinosissimus, plays a vital role on Western Atlantic reefs by grazing macroalgae that competes for space with coral recruits. Therefore, identifying its tolerance to anthropogenic stressors is critically needed if this species is to be considered as a potential restoration management strategy in coral reef environments. We examined the effects of temperature (control: 28 °C and elevated: 31 °C) and pH (control: 8.0 and reduced pH: 7.7) on the king crab’s larval and early juvenile survival, molt-stage duration, and morphology in a fully crossed laboratory experiment. Survival to the megalopal stage was reduced (13.5% lower) in the combined reduced pH and elevated temperature treatment relative to the control. First-stage (J1) juveniles delayed molting by 1.5 days in the reduced pH treatment, while second-stage (J2) crabs molted 3 days earlier when exposed to elevated temperature. Juvenile morphology did not differ among treatments. These results suggests that juvenile king crabs are tolerant to changes associated with climate change. Given the important role of the king crab as a grazer of macroalgae, its tolerance to climate stressors suggests that it could benefit restoration efforts aimed at making coral reefs more resilient to increasingly warm and acidic oceans into the future.

Continue reading ‘Caribbean king crab larvae and juveniles show tolerance to ocean acidification and ocean warming’

Effect of temperature and pH on the Millepora alcicornis and Mussismilia harttii corals in light of a spectral reflectance response

The increase in carbon dioxide (CO2) atmospheric levels contributes to the rise in temperature and ocean acidification; consequently, it directly impacts coral reefs. The increase in seawater temperature is the primary factor that causes the collapse of coral-algal symbiosis, which can be followed by coral death and, generally, ocean acidification impairs biogenic calcification and promotes dissolution of carbonate substrata. These harmful effects on corals associated with the continuous increase in CO2 atmospheric levels raise widespread concerns about the coral reef decline, intensifying the efforts to understand/monitor their effects on these organisms. The objective of this study was to evaluate the physiological effect of temperature increase, water acidification (i.e. decrease in pH), and their effects combined (temperature increase with water acidification), through the reflectance analyses and maximum photosynthetic capacity of zooxanthellae (Fv/Fm) in two coral species: Millepora alcicornis and Mussismilia harttii. Fragments of four large colonies of each specie were collected, fragmented, and submitted to four different treatments for 15 days: (i) control treatment (under identical temperature and pH conditions observed in the sampling seawater site), (ii) temperature treatment (with an increase temperature of around ≅2ºC); (iii) water acidification treatment (with a decrease of nearly 0.3 in pH); and (iv) a treatment of combined effects from water temperature rising and acidification. Spectral reflectance and Fv/Fm were measured from samples of these species in a marine mesocosm. Data of reflectance, first and second-order derivative, area under the curve, full width at half maximum (FWHM), depth values and the Fv/Fm were used to classify the coral species and treatments through the linear discriminant analysis (LDA). Coral samples were exposed to the increased temperature bleached, whilst decreased pH caused a slight reduction in reflectance albedo with minimal effects on Fv/Fm. The combined factors (treatment iv) triggered a bleaching response, presenting spectral reflectance and colouring patterns similar to those observed in bleached corals, especially for M. alcicornis. The two-way ANOVA indicated statistically meaningful spectral differences between treatments for the second-order derivatives at 634 nm and for Fv/Fm values. However, there was no statistically meaningful interaction effect due to the treatment type and coral species response for the second-order derivative at 670 nm and to the Fv/Fm values. LDA classified the corals’ species and the corals in different treatment, using their spectral responses and Fv/Fm results, with high accuracy (96.7% and 73.3%, respectively), reinforcing its application for coral physiology evaluation and species classification. The control and combined groups achieved the best classification scores, with only one misclassification.

Continue reading ‘Effect of temperature and pH on the Millepora alcicornis and Mussismilia harttii corals in light of a spectral reflectance response’

Predicted changes in temperature, more than acidification, affect the shell morphology and survival of the girdled dogwhelk, Trochia cingulata (Linnaeus, 1771)

Despite the existing body of research that considers altered ocean temperature and acidification as co-occurring stressors, our understanding of the consequences of such shifts remains limited. This is particularly problematic in relation to predators such as whelks, as they can exert strong top-down control of communities yet, as calcifying ectotherms, they are likely to be vulnerable to climate change. This study assessed the effects of simultaneous changes in water temperature and pH on the South African girdled dogwhelk Trochia cingulata. For 12 weeks, whelks were exposed to three temperatures, 9 °C (cooling), 13 °C (current) and 17 °C (warming), each at three target pH levels, 8.0 (current), 7.7 (intermediate) and 7.5 (extreme). For each treatment shell thickness, strength and shape were measured after 6 and 12 weeks, while mortality was recorded daily. Survival was not affected by pH and was highest at 9 °C. Almost all whelks exposed to warming died within 2 weeks. After 6 weeks, shell strength declined significantly as acidity increased, regardless of temperature, and shells of whelks held at 9 °C were thinner. By 12 weeks, whelks exposed to cooling and extreme pH had the weakest shells. Notably, temperature no longer influenced shell thickness, but whelks held at 9 °C became globular in shape. These changes in shell morphology likely resulted from the increased cost of shell maintenance in cool, acidic conditions. The differences observed at 6 and 12 weeks demonstrate how responses can change over time, a point that should be kept in mind when assessing species sensitivities to changing environments. The dominant effect of temperature highlights that T. cingulata is particularly vulnerable to warming, while regional cooling may pose a challenge with respect to shell morphology.

Continue reading ‘Predicted changes in temperature, more than acidification, affect the shell morphology and survival of the girdled dogwhelk, Trochia cingulata (Linnaeus, 1771)’

Temperature coefficient of seawater pH as a function of temperature, pH, DIC and salinity

pH is a measure of the hydrogen ion activity in solution, which is a function of temperature. Under normal seawater conditions, it is well constrained. Nowadays, with an increasing interest in complex environments (e.g., sea ice), a better understanding of the temperature change on pH under extreme conditions is needed. The objective of this paper was to investigate the temperature coefficient of the seawater pH (∆pH/∆T) over a wide range of temperature, pH, dissolved inorganic carbon (DIC) and salinity by a method of continuous pH measurement with the temperature change and to verify the application of CO2SYS for pH conversion under extreme conditions (on the NBS scale and the total proton scale). Both experimental results and CO2SYS calculations showed that ∆pH/∆T was slightly affected by temperature over the range of 0 to 40°C and by pH (at 25°C) from 7.8 to 8.5. However, when pH was out of this range, ∆pH/∆T varied greatly with pH value. According to the experimental results, changes in DIC from 1 mmol/kg to 5 mmol/kg and salinity from 20 to 105 had no significant effect on ∆pH/∆T. CO2SYS calculations showed a slight increase in ∆pH/∆T with DIC on both the NBS scale and the total proton scale; and underestimated ∆pH/∆T at high salinity (i.e., beyond the oceanographic range) on the NBS scale. Nevertheless, CO2SYS is still suitable for pH conversion even under extreme conditions by simply setting the input values of DIC and salinity in CO2SYS within the oceanographic range (e.g., DIC=2 mmol/kg and S=35).

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Increasing arsenic accumulation as an implication of climate change: a case study using red algae

Climate change due to an increasing concentration of carbon dioxide in the atmosphere is a global issue. It can impact aquatic environments by affecting water flow, pollutant transformation and migration, and other toxicant-related effects. We assessed the interactive effects of temperature warming and pH changes on variations in accumulation of total arsenic (AsT) in the red alga Sarcodia suae at different levels of arsenite (AsIII). Result showed that AsT variations in the alga were moderated by significant joint effects of warming temperature and/or increasing pH levels and their interactions with increasing AsIII concentrations. Our study suggests possible deleterious impacts on macroalgal populations due to toxicological effects associated with prevailing environmental conditions. Therefore, improved pollution management, climate change adaptation, and mitigation strategies are needed to deal with current environmental issues and As aggravation.

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Effects of ocean acidification over successive generations decrease larval resilience to ocean acidification & warming but juvenile European sea bass could benefit from higher temperatures in the NE Atlantic

European sea bass (Dicentrarchus labrax) is a large, economically important fish species with a long generation time whose long-term resilience to ocean acidification (OA) and warming (OW) is not clear. We incubated sea bass from Brittany (France) for two generations (>5 years in total) under ambient and predicted OA conditions (PCO2: 650 and 1700 µatm) crossed with ambient and predicted ocean OW conditions in F1 (temperature: 15-18°C and 20-23°C) to investigate the effects of climate change on larval and juvenile growth and metabolic rate.

We found that in F1, OA as single stressor at ambient temperature did not affect larval or juvenile growth and OW increased developmental time and growth rates, but OAW decreased larval size at metamorphosis. Larval routine and juvenile standard metabolic rates were significantly lower in cold compared to warm conditioned fish and also lower in F0 compared to F1 fish. We did not find any effect of OA as a single stressor on metabolic rates. Juvenile PO2crit was not affected by OA or OAW in both generations.

We discuss the potential underlying mechanisms resulting in the resilience of F0 and F1 larvae and juveniles to OA and in the beneficial effects of OW on F1 larval growth and metabolic rate, but on the other hand in the vulnerability of F1, but not F0 larvae to OAW. With regard to the ecological perspective, we conclude that recruitment of larvae and early juveniles to nursery areas might decrease under OAW conditions but individuals reaching juvenile phase might benefit from increased performance at higher temperatures.

Continue reading ‘Effects of ocean acidification over successive generations decrease larval resilience to ocean acidification & warming but juvenile European sea bass could benefit from higher temperatures in the NE Atlantic’

Impaired hatching exacerbates the high CO2 sensitivity of embryonic sand lance Ammodytes dubius

Rising oceanic pCO2 levels could affect many traits in fish early life stages, but only few species to date have shown direct CO2-induced survival reductions. This might partly be because species from less CO2-variable, offshore environments in higher latitudes are currently underrepresented in the literature. We conducted new experimental work on northern sand lance Ammodytes dubius, a keystone forage fish on offshore Northwest Atlantic sand banks, which was recently suggested to be highly CO2-sensitive. In two complementary trials, we produced embryos from wild, Gulf of Maine (GoM) spawners and reared them at several pCO2 levels (~400–2000 µatm) in combination with static (6, 7, 10°C) and dynamic (10 → 5°C) temperature treatments. Again, we consistently observed large, CO2-induced reductions in hatching success (–23% at 1000 µatm, -61% at ~2000 µatm), and the effects were temperature-independent. To distinguish pCO2 effects during development from potential impacts on hatching itself, some embryos were switched between high and control pCO2 treatments just prior to hatch. This indeed altered hatching patterns consistent with the CO2-impaired hatching hypothesis. High CO2 also delayed the day of first hatch in one trial and peak hatch in the other, where later-hatched larvae were of similar size but with progressively less endogenous energy reserves. For context, we extracted seasonal pCO2 projections for Stellwagen Bank (GoM) from regional ensemble simulations, which indicated a CO2-induced reduction in sand lance hatching success to 71% of contemporary levels by 2100. The species’ unusual CO2 sensitivity has large ecological and scientific ramifications that warrant future in-depth research.

Continue reading ‘Impaired hatching exacerbates the high CO2 sensitivity of embryonic sand lance Ammodytes dubius’

Dynamic energy budget modeling of Atlantic surfclam, Spisula solidissima, under future ocean acidification and warming

Highlights

  • Surfclams were exposed to OA levels inducing effects on physiological rates
  • A DEB model was calibrated integrating effects on ingestion and maintenance costs
  • The model was validated on Georges Bank and Mid-Atlantic Bight population data
  • Effects of future OA and warming conditions projected by RCP scenarios were simulated
  • Under high pCO2 emissions, DEB projects effects on growth and reproduction by 2100

Abstract

A dynamic energy budget (DEB) model integrating pCO2 was used to describe ocean acidification (OA) effects on Atlantic surfclam, Spisula solidissima, bioenergetics. Effects of elevated pCO2 on ingestion and somatic maintenance costs were simulated, validated, and adapted in the DEB model based upon growth and biological rates acquired during a 12-week laboratory experiment. Temperature and pCO2 were projected for the next 100 years following the intergovernmental panel on climate change representative concentration pathways scenarios (2.6, 6.0, and 8.5) and used as forcing variables to project surfclam growth and reproduction. End-of-century water warming and acidification conditions resulted in simulated faster growth for young surfclams and more energy allocated to reproduction until the beginning of the 22nd century when a reduction in maximum shell length and energy allocated to reproduction was observed for the RCP 8.5 scenario.

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Predicted future changes in ocean temperature and pH do not affect prey selection by the girdled dogwhelk Trochia cingulata

Predator–prey relationships can drive community dynamics in marine systems, but it remains unclear how future changes in seawater temperatures and pH will influence these relationships. This study assessed the effect of predicted future temperatures and pH on the prey choice of the girdled dogwhelk Trochia cingulata (family Muricidae) when offered native (Aulacomya atraChoromytilus meridionalis) and alien (Semimytilus algosus) mussels. Whelks were exposed to three pH levels: 8.0 (current), 7.7 (intermediate) and 7.5 (extreme), at each of three temperatures: 9 °C (cooling), 13 °C (current) and 17 °C (warming) for 6 weeks. Thereafter, the prey preference and predation rate were compared among treatments. Within two weeks, 98% of whelks exposed to warming died, precluding assessment of how warming affects their prey preference. Despite high mortality, the highest predation rates were recorded at 17 °C regardless of the pH level, likely reflecting increased energy costs and ingestion rates associated with warming. In the remaining treatments whelks preferred S. algosus irrespective of the levels of seawater cooling or acidification. These results align with previous work that demonstrated a preference by T. cingulata for S. algosus and suggest that the predator–prey relationship between this whelk and its mussel prey is unlikely to be disrupted under future marine conditions.

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Coral calcification mechanisms in a warming ocean and the interactive effects of temperature and light

Ocean warming is transforming the world’s coral reefs, which are governed by the growth of marine calcifiers, most notably branching corals. Critical to skeletal growth is the corals’ regulation of their internal chemistry to promote calcification. Here we investigate the effects of temperature and light on the calcifying fluid chemistry (using boron isotope systematics), calcification rates, metabolic rates and photo-physiology of Acropora nasuta during two mesocosm experiments simulating seasonal and static temperature and light regimes. Under the seasonal regime, coral calcification rates, calcifying fluid carbonate chemistry, photo-physiology and metabolic productivity responded to both changes in temperature and light. However, under static conditions the artificially prolonged exposure to summer temperatures resulted in heat stress and a heightened sensitivity to light. Our results indicate that temperature and light effects on coral physiology and calcification mechanisms are interactive and context-specific, making it essential to conduct realistic multi-variate dynamic experiments in order to predict how coral calcification will respond to ocean warming.

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Response of Cymodocea nodosa to ocean acidification and warming in the Canary Islands: direct and indirect effects

Hightlights

  • Ocean acidification increase growth and gross primary production of Cymodocea nodosa.
  • The rise of temperature limited the net and gross primary production of Cymodocea nodosa.
  • A positive effect of decrased pH on greater vulnerability to consumption by Paracentrotus lividus.
  • A future scenario of climate change will affect metabolic rates of C.nodosa.
  • Different responses to climate change have been observed by C. nodosa from Canary Islands.

Abstract

As detected in warming and ocean acidification, global change can have profound impact on marine life. Its effects on seagrasses are becoming increasingly well-known, since several studies have focused on the responses of these species to global change conditions. However a few studies have assessed the combined effect of temperature and acidification on seagrasses. Overall in this study, the combined effects of increased ocean temperature and pH levels expected at the end of this century (+5 °C and pH 7.5) on Cymodocea nodosa from Canary Islands, were evaluated for one month through manipulative laboratory experiments. Growth, net production, respiration, gross primary production, chlorophyll-a concentration and its vulnerability to herbivory were quantified. Results showed a positive effect of decreased pH on growth and gross primary production, as well as greater vulnerability to consumption by the sea urchin Paracentrotus lividus. In contrast, increased temperature limited net and gross primary production. This study shows than in future scenarios, C. nodosa from the Canary Islands may be a losing species in the global change stakes.

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Circadian rhythm and neurotransmitters are potential pathways through which ocean acidification and warming affect the metabolism of thick-shell mussels

Although the impacts of ocean acidification and warming on marine organisms have been increasingly documented, little is known about the affecting mechanism underpinning their interactive impacts on physiological processes such as metabolism. Therefore, the effects of these two stressors on metabolism were investigated in thick-shell mussel Mytilus coruscus in this study. In addition, because metabolism is primarily regulated by circadian rhythm and neurotransmitters, the impacts of acidification and warming on these two regulatory processes were also analyzed. The data obtained demonstrated that the metabolism of mussels (indicated by the clearance rate, oxygen consumption rate, ammonia excretion rate, O:N ratio, ATP content, activity of pyruvate kinase, and expression of metabolism-related genes) were significantly affected by acidification and warming, resulting in a shortage of energy supply (indicated by the in vivo content of ATP). In addition, exposure to acidification and warming led to evident disruption in circadian rhythm (indicated by the heartrate and the expression rhythm of Per2Cry, and BMAL1) and neurotransmitters (indicated by the activity of acetyl cholinesterase and in vivo contents of ACh, GABA, and DA). These findings suggest that circadian rhythms and neurotransmitters might be potential routes through which acidification and warming interactively affect the metabolism of mussels.

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Temperature effects on leaf and epiphyte photosynthesis, bicarbonate use and diel O2 budgets of the seagrass Zostera marina L.

Ocean warming along with nutrient enrichment are major stressors causing global seagrass decline. While the effects of global warming on metabolic parameters in seagrasses are well described, the effect of increasing temperature on the epiphytic overgrowth of seagrass leaves and the consequences for the seagrass plant are poorly understood. Here, we investigated the effects of elevating temperature on the photosynthetic efficiency of the seagrass species Zostera marina L. and its associated epiphytes, to explore how ocean warming might affect epiphytism in seagrasses. Gas exchange and final pH measurements on bare seagrass leaves, leaves with epiphytes, and epiphytes separated from seagrass leaves were used to quantify photosynthesis and respiration rates, and the inorganic carbon extraction capacity of leaves and epiphytes as a function of photon scalar irradiance and temperature (12, 17, 22, and 27°C). Seagrass without epiphytic biofilm had a high ability to exploit the incoming irradiance regardless of the light intensity and temperature, shown as continuously high light use efficiency and maximum net photosynthesis rates. The presence of epiphytic biofilm on the seagrass leaves impaired plant photosynthesis by increasing light requirements and reducing the photosynthetic efficiency (especially at 27°C). Epiphytes showed the lowest respiration rates in darkness and had the highest oxygen surplus over diel cycles up to 22°C, whereas bare leaves had the highest diel oxygen surplus at 27°C. Both bare leaves and epiphytes lost the ability to utilize bicarbonate at 27°C, and epiphytes also did not show use of bicarbonate at 12°C. Our results indicate a competitive advantage for epiphytes in cold CO2-rich environments, whereas seagrass with bare leaves could be less affected under elevated seawater temperatures.

Continue reading ‘Temperature effects on leaf and epiphyte photosynthesis, bicarbonate use and diel O2 budgets of the seagrass Zostera marina L.’

Ocean acidification stimulation of phytoplankton growth depends on the extent of departure from the optimal growth temperature

Highlights

  • Growth enhancement by HC was most prominent at temperatures close to optimum.
  • Cellular POC and PON were significantly reduced in HC than in LC near optimum.
  • High CO2-grown cells endured more stress at high and low growth temperatures.

Abstract

Ocean acidification and warming are two major environmental stressors; however, the generality of how warming will alter growth responses of phytoplankton to ocean acidification is less known. Here, enhancement of growth by high CO2 (HC) in Phaeodactylum tricornutum and Thalassiosira weissflogii was most prominent at optimum temperature. The extent to which growth rates in HC cultures were raised compared to low CO2 (LC) cultures tended to decrease with increasing or decreasing temperature, compared to the optimum. Further mechanistic studies in P. tricornutum revealed that cellular carbon and nitrogen content, superoxide dismutase activity, and respiration were generally higher in HC than those in LC at high and low temperatures, whereas PSII photochemical parameters were generally lower in HC than in LC at high and low temperatures. These results indicate that HC-grown cells needed to invest more energy and materials to maintain intracellular homeostasis and repair damage induced by the unsuitable temperatures.

Continue reading ‘Ocean acidification stimulation of phytoplankton growth depends on the extent of departure from the optimal growth temperature’

Elevated temperature and low pH affect the development, reproduction, and feeding preference of the tropical cyclopoid copepod Oithona rigida

The copepod genus Oithona is among the most abundant mesozooplankton in both eutrophic and oligotrophic waters. This paper reports the individual and combined effect of temperature and pH on the development, reproduction success, and feeding preference of the tropical species Oithona rigida. Experiments were conducted at different temperature (28, 30, 31, and 32°C) and pH (7.7, 7.9, and 8.1) conditions. Effects on vital rates were observed for different developmental stages and adult males. Sex ratio varied from near 1:1 at 28°C to almost entirely female at 32°C. Egg production and hatching success were maximum at 30°C and pH at 7.9. O. rigida preferred the motile green alga Dunaliella salina in terms of ingestion rate, feed selectivity, and egg production across all the temperature and pH conditions. Long-term studies are needed to validate the adaptability of this species to a variety of climate impacts.

Continue reading ‘Elevated temperature and low pH affect the development, reproduction, and feeding preference of the tropical cyclopoid copepod Oithona rigida’

An integrated multiple driver mesocosm experiment reveals the effect of global change on planktonic food web structure

Global change puts coastal marine systems under pressure, affecting community structure and functioning. Here, we conducted a mesocosm experiment with an integrated multiple driver design to assess the impact of future global change scenarios on plankton, a key component of marine food webs. The experimental treatments were based on the RCP 6.0 and 8.5 scenarios developed by the IPCC, which were Extended (ERCP) to integrate the future predicted changing nutrient inputs into coastal waters. We show that simultaneous influence of warming, acidification, and increased N:P ratios alter plankton dynamics, favours smaller phytoplankton species, benefits microzooplankton, and impairs mesozooplankton. We observed that future environmental conditions may lead to the rise of Emiliania huxleyi and demise of Noctiluca scintillans, key species for coastal planktonic food webs. In this study, we identified a tipping point between ERCP 6.0 and ERCP 8.5 scenarios, beyond which alterations of food web structure and dynamics are substantial.

Continue reading ‘An integrated multiple driver mesocosm experiment reveals the effect of global change on planktonic food web structure’

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