Posts Tagged 'morphology'

Decreased pH impairs sea urchin resistance to predatory fish: a combined laboratory-field study to understand the fate of top-down processes in future oceans

Highlights

  • Combined laboratory-field approach to study OA effects on predator-prey interactions.

  • Adult sea urchins mechanical defence strategies are compromised by decreased pH.

  • Field data confirm grater vulnerability to predation of sea urchins exposed to lower pH.

  • Future more acidic seawaters will impair sea urchin resistance to predatory fish.

Abstract

Changing oceans represent a serious threat for a wide range of marine organisms, with severe cascading effects on ecosystems and their services. Sea urchins are particularly sensitive to decreased pH expected for the end of the century and their key ecological role in regulating community structure and functioning could be seriously compromised. An integrated approach of laboratory and field experiments has been implemented to investigate the effects of decreased pH on predator-prey interaction involving sea urchins and their predators. Our results suggest that under future Ocean Acidification scenarios adult sea urchins defence strategies, such as spine length, test robustness and oral plate thickness, could be compromised together with their survival chance to natural predators. Sea urchins represent the critical linkage between top-down and bottom-up processes along Mediterranean rocky reefs, and the cumulative impacts of global and local stressors could lead to a decline producing cascading effects on benthic ecosystems.

Continue reading ‘Decreased pH impairs sea urchin resistance to predatory fish: a combined laboratory-field study to understand the fate of top-down processes in future oceans’

Coastal acidification and deoxygenation enhance settlement but do not influence movement behavior of creeping polyps of the irukandji jellyfish, Alatina alata (cubozoa)

Highlights

  • Deoxygenation enhanced the survival of the creeping polyps of Alatina alata.

  • More creeping polyps settled under low pH and low dissolved O2 (DO) treatments than under normal pH and DO conditions.

  • Exposure to low pH and DO did not influence the number of tentacles, mobility or movement velocity of the creeping polyps.

  • The Irukandji jellyfish may persist in coastal areas with coastal deoxygenation and acidification.

Abstract

Deoxygenation and acidification co-occur in many coastal ecosystems because nutrient enrichment produces excess organic matter that intensifies aerobic respiration during decomposition, thereby depleting O2, increasing CO2 and lowering pH. Despite this link between coastal deoxygenation (CD) and acidification (CA), and evidence that both stressors pose a risk to marine fauna, few studies have examined the effects of these drivers in combination on marine animals including invertebrates. Here, we studied the individual and combined effects of CD (∼1.5 mg L−1 O2) and CA (∼7.7 pH) on the survival, number of tentacles, settlement and movement behaviours of creeping polyps of the Irukandji jellyfish, Alatina alata. Low DO increased the survival rate (17% more) of the creeping polyps. 12% more creeping polyps settled in low pH than ambient pH and 16.7% more settled in low DO than ambient DO treatment. Exposure to CA and CD did not influence the number of tentacles, mobility or movement velocity of the creeping polyps, but after 4 h exposure to the treatments, they moved approximately half as fast. Our results indicate that CD can enhance survival and settlement success, but CA does not intensify these outcomes on A. alata creeping polyps.

Continue reading ‘Coastal acidification and deoxygenation enhance settlement but do not influence movement behavior of creeping polyps of the irukandji jellyfish, Alatina alata (cubozoa)’

Effects of ocean acidification on acid-base physiology, skeleton properties, and metal contamination in two echinoderms from vent sites in Deception Island, Antarctica

Highlights

  • Acid-base characteristics of adult Antarctic echinoderms are similar to those of tropical and temperate echionderms
  • Skeleton properties of both species were weaker than those of tropical and temperate echinoderms
  • Reduced seawater pH and metals had no impact on the skeleton mechanical properties of the two investigated species
  • Reduced pH was correlated to increased contamination by most metals but this relation was weak

Abstract

Antarctic surface waters are expected to be the first to experience severe ocean acidification (OA) with carbonate undersaturation and large decreases in pH forecasted before the end of this century. Due to the long stability in environmental conditions and the relatively low daily and seasonal variations to which they are exposed, Antarctic marine organisms, especially those with a supposedly poor machinery to eliminate CO2 and protons and with a heavily calcified skeleton like echinoderms, are hypothesized as highly vulnerable to these environmental shifts. The opportunities offered by the natural pH gradient generated by vent activities in Deception Island caldera, Western Antarctic Peninsula, were used to investigate for the first time the acid-base physiologies, the impact of OA on the skeleton and the impact of pH on metal accumulation in the Antarctic sea star Odontaster validus and sea urchin Sterechinus neumayeri. The two species were sampled in four stations within the caldera, two at pH (total scale) 8.0- 8.1 and two at reduced pH 7.8. Measured variables were pH, alkalinity, and dissolved inorganic carbon of the coelomic fluid; characteristic fracture force, stress and Young’s modulus using Weibull statistics and Cd, Cu, Fe, Pb and Zn concentrations in the integument, gonads and digestive system. Recorded acid-base characteristics of both studied species fit in the general picture deduced from temperate and tropical sea stars and sea urchins but conditions and possibly confounding factors, principally food availability and quality, in the studied stations prevented definitive conclusions. Reduced seawater pH 7.8 and metals had almost no impact on the skeleton mechanical properties of the two investigated species despite very high Cd concentrations in O. validus integument. Reduced pH was correlated to increased contamination by most metals but this relation was weak. Translocation and caging experiments taking into account food parameters are proposed to better understand future processes linked to ocean acidification and metal contamination in Antarctic echinoderms.

Continue reading ‘Effects of ocean acidification on acid-base physiology, skeleton properties, and metal contamination in two echinoderms from vent sites in Deception Island, Antarctica’

The marine gastropod Crepidula fornicata remains resilient to ocean acidification across two life history stages

Rising atmospheric CO2 reduces seawater pH causing ocean acidification (OA). Understanding how resilient marine organisms respond to OA may help predict how community dynamics will shift as CO2 continues rising. The common slipper shell snail Crepidula fornicata is a resilient marine gastropod native to eastern North America, which has been a successful invader along the western European coastline and elsewhere. To examine its potential resilience to OA, we conducted two controlled laboratory experiments. First, we examined several phenotypes and genome-wide gene expression of C. fornicata in response to pH treatments (7.5, 7.6, 8.0) throughout the larval stage and then tested how conditions experienced as larvae influenced juvenile stages (i.e. carryover effects). Second, we examined genome-wide gene expression patterns of C. fornicata larvae in response to acute (4, 10, 24 and 48 hours) pH treatment (7.5, 8.0). Both C. fornicata larvae and juveniles exhibited resilience to OA and gene expression responses highlight the role of transcriptome plasticity in OA resilience. Larvae did not exhibit reduced growth under OA until they were at least 4 days old. These phenotypic effects were preceded by broad transcriptomic changes, which likely serve as an acclimation mechanism for combating reduced pH conditions frequently experienced in littoral zones. Delayed metamorphosis was observed for larvae reared at reduced pH. Although juvenile size reflected larval rearing pH conditions, no carryover effects in juvenile growth rates were observed. Transcriptomic analyses suggest increased metabolism under OA, which may indicate compensation in reduced pH environments. Time course transcriptomic analyses suggest energetic burdens experienced under OA eventually dissipate, allowing C. fornicata to reduce metabolic demands and acclimate to reduced pH. This study highlights the importance of assessing the effects of OA across life history stages and demonstrates how transcriptomic plasticity can allow highly resilient organisms, like C. fornicata, acclimate to reduced pH environments.

Continue reading ‘The marine gastropod Crepidula fornicata remains resilient to ocean acidification across two life history stages’

Increased light availability enhances tolerance against ocean acidification stress in Halimeda opuntia

Although the adverse impacts of ocean acidification (OA) on marine calcifiers have been investigated substantially, the anti-stress abilities regulated by increased light availability are unclear. Herein, the interactive effects of three light levels combined with two pCO2 concentrations on the physiological acclimation of the calcifying macroalga Halimeda opuntia were investigated using a pCO2–light coupling experiment. The results indicate that OA exhibits an adverse role in influencing algal growth, calcification, photosynthesis and other physiological performances in H. opuntia. The relative growth rate in elevated pCO2 significantly declined by 13.14%–41.29%, while net calcification rates decreased by nearly three-fold under OA. Notably, increased light availability could enhance stress resistance by the accumulation of soluble organic molecules, especially soluble carbohydrate, soluble protein and free amino acids, and in combination with metabolic enzyme-driven activities alleviated OA stress. Carotenoid content in low light conditions accumulated remarkably and rapid light curves for relative electron transport rate was significantly enhanced by increasing light intensities, indicating that this new organization of the photosynthetic machinery in H. opuntia accommodated light variations and elevated pCO2 conditions. Taken together, the results describe stress resistance by the enhancement of metabolic performance in marine calcifiers to mitigate OA stress.

Continue reading ‘Increased light availability enhances tolerance against ocean acidification stress in Halimeda opuntia’

Ocean acidification mitigates the negative effects of increased sea temperatures on the biomineralization and crystalline ultrastructure of Mytilus

Negative impacts of global climate change are predicted for a range of taxa. Projections predict marked increases in sea surface temperatures and ocean acidification (OA), arguably placing calcifying organisms at most risk. While detrimental impacts of environmental change on the growth and ultrastructure of bivalve mollusk shells have been shown, rapid and diel fluctuations in pH typical of coastal systems are often not considered. Mytilus edulis, an economically important marine calcifier vulnerable to climate change, were exposed to current and future OA (380 and 1000 ppm pCO2), warming (17 and 20°C), and ocean acidification and warming (OAW) scenarios in a seawater system incorporating natural fluctuations in pH. Both macroscopic morphometrics (length, width, height, volume) and microscopic changes in the crystalline structure of shells (ultrastructure) using electron backscatter diffraction (EBSD) were measured over time. Increases in seawater temperature and OAW scenarios led to increased and decreased shell growth respectively and on marginal changes in cavity volumes. Shell crystal matrices became disordered shifting toward preferred alignment under elevated temperatures indicating restricted growth, whereas Mytilus grown under OAW scenarios maintained single crystal fabrics suggesting OA may ameliorate some of the negative consequences of temperature increases. However, both elevated temperature and OAW led to significant increases in crystal size (grain area and diameter) and misorientation frequencies, suggesting a propensity toward increased shell brittleness. Results suggest adult Mytilus may become more susceptible to biological determinants of survival in the future, altering ecosystem structure and functioning.

Continue reading ‘Ocean acidification mitigates the negative effects of increased sea temperatures on the biomineralization and crystalline ultrastructure of Mytilus’

Lower salinity leads to improved physiological performance in the coccolithophorid Emiliania huxleyi, which partly ameliorates the effects of ocean acidification

While seawater acidification induced by elevated CO2 is known to impact coccolithophores, the effects in combination with decreased salinity caused by sea ice melting and/or hydrological events have not been documented. Here we show the combined effects of seawater acidification and reduced salinity on growth, photosynthesis and calcification of Emiliania huxleyi grown at 2 CO2 concentrations (low CO2 LC:400 μatm; high CO2 HC:1000 μatm) and 3 levels of salinity (25, 30, and 35‰). A decrease of salinity from 35 to 25‰ increased growth rate, cell size and photosynthetic performance under both LC and HC. Calcification rates were relatively insensitive to salinity though they were higher in the LC-grown compared to the HC-grown cells at 25‰ salinity, with insignificant differences under 30 and 35‰. Since salinity and OA treatments did not show interactive effects on calcification, changes in calcification: photosynthesis ratios are attributed to the elevated photosynthetic rates at lower salinities, with higher ratios of calcification to photosynthesis in the cells grown under 35‰ compared with those grown at 25‰. In contrast, photosynthetic carbon fixation increased almost linearly with decreasing salinity, regardless of the pCO2 treatments. When subjected to short-term exposure to high light, the low-salinity-grown cells showed the highest photochemical effective quantum yield with the highest repair rate, though the HC treatment enhanced the PSII damage rate. Our results suggest that, irrespective of pCO2, at low salinity Emiliania huxleyi up-regulates its photosynthetic performance which, despite a relatively insensitive calcification response, may help it better adapt to future ocean global environmental changes, including ocean acidification, especially in the coastal areas of high latitudes.

Continue reading ‘Lower salinity leads to improved physiological performance in the coccolithophorid Emiliania huxleyi, which partly ameliorates the effects of ocean acidification’

Summer and winter MgCO3 levels in the skeletons of Arctic bryozoans

Highlights

  • Summer and winter MgCO3 levels in skeleton of Arctic bryozoans by Anna Iglikowska, Małgorzata Krzemińska, Paul E. Renaud, Jørgen Berge, Haakon Hop and Piotr Kukliński.
  • Arctic seawater differs in carbonate saturation state during polar night and day.

  • During summer carbonate saturation gradient is expected related to depth.

  • Carbonate saturation state may influence Mg accumulation in biogenic calcite.

  • No differences between summer and winter levels of skeletal MgCO3 were found.

  • Bryozoans are able to regulate their skeletal MgCO3 concentrations biologically.

Abstract

In the Arctic, seasonal patterns in seawater biochemical conditions are shaped by physical, chemical, and biological processes related to the alternation of seasons, i.e. winter polar night and summer midnight sun. In summertime, CO2 concentration is driven by photosynthetic activity of autotrophs which raises seawater pH and carbonate saturation state (Ω). In addition, restriction of photosynthetic activity to the euphotic zone and establishment of seasonal stratification often leads to depth gradients in pH and Ω. In winter, however, severely reduced primary production along with respiration processes lead to higher CO2 concentrations which consequently decrease seawater pH and Ω.

Many calcifying invertebrates incorporate other minerals, in addition to calcium, into their skeletons, with potential consequences for stability of the mineral matrix and vulnerability to abrasion of predators. We tested whether changes in seawater chemistry due to light-driven activities of marine biota can influence the uptake of Mg into calcified skeletons of Arctic Bryozoa, a dominant faunal group in polar hard-bottom habitats. Our results indicate no clear differences between summer and winter levels of skeletal MgCO3 in five bryozoan species despite differences in Ω between these two seasons. Furthermore, we could not detect any depth-related differences in MgCO3 content in skeletons of selected bryozoans. These results may indicate that Arctic bryozoans are able to control MgCO3 skeletal concentrations biologically. Yet recorded spatial variability in MgCO3 content in skeletons from stations exhibiting different seawater parameters suggests that environmental factors can also, to some extent, shape the skeletal chemistry of Arctic bryozoans.

Continue reading ‘Summer and winter MgCO3 levels in the skeletons of Arctic bryozoans’

Evolved differences in energy metabolism and growth dictate the impacts of ocean acidification on abalone aquaculture

Ocean acidification (OA) poses a major threat to marine ecosystems and shellfish aquaculture. A promising mitigation strategy is the identification and breeding of shellfish varieties exhibiting resilience to acidification stress. We experimentally compared the effects of OA on two populations of red abalone (Haliotis rufescens), a marine mollusc important to fisheries and global aquaculture. Results from our experiments simulating captive aquaculture conditions demonstrated that abalone sourced from a strong upwelling region were tolerant of ongoing OA, whereas a captive-raised population sourced from a region of weaker upwelling exhibited significant mortality and vulnerability to OA. This difference was linked to population-specific variation in the maternal provisioning of lipids to offspring, with a positive correlation between lipid concentrations and survival under OA. This relationship also persisted in experiments on second-generation animals, and larval lipid consumption rates varied among paternal crosses, which is consistent with the presence of genetic variation for physiological traits relevant for OA survival. Across experimental trials, growth rates differed among family lineages, and the highest mortality under OA occurred in the fastest growing crosses. Identifying traits that convey resilience to OA is critical to the continued success of abalone and other shellfish production, and these mitigation efforts should be incorporated into breeding programs for commercial and restoration aquaculture.

Continue reading ‘Evolved differences in energy metabolism and growth dictate the impacts of ocean acidification on abalone aquaculture’

Ocean acidification causes variable trait shifts in a coral species

High pCO2 habitats and their populations provide an unparalleled opportunity to assess how species may survive under future ocean acidification conditions, and help to reveal the traits that confer tolerance. Here we utilize a unique CO2 vent system to study the effects of exposure to elevated pCO2 on trait‐shifts observed throughout natural populations of Astroides calycularis, an azooxanthellate scleractinian coral endemic to the Mediterranean. Unexpected shifts in skeletal and growth patterns were found. Colonies shifted to a skeletal phenotype characterized by encrusting morphology, smaller size, reduced coenosarc tissue, fewer polyps, and less porous and denser skeletons at low pH. Interestingly, while individual polyps calcified more and extended faster at low pH, whole colonies found at low pH site calcified and extended their skeleton at the same rate as did those at ambient pH sites. Transcriptomic data revealed strong genetic differentiation among local populations of this warm water species whose distribution range is currently expanding northward. We found excess differentiation in the CO2 vent population for genes central to calcification, including genes for calcium management (calmodulin, calcium‐binding proteins), pH regulation (V‐type proton ATPase), and inorganic carbon regulation (carbonic anhydrase). Combined, our results demonstrate how coral populations can persist in high pCO2 environments, making this system a powerful candidate for investigating acclimatization and local adaptation of organisms to global environmental change.

Continue reading ‘Ocean acidification causes variable trait shifts in a coral species’


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Ocean acidification in the IPCC AR5 WG II

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