Climate change driven alterations in salinity and carbonate chemistry are predicted to have significant implications particularly for northern costal organisms, including the economically important filter feeders Mytilus edulis and Ciona intestinalis. However, despite a growing number of studies investigating the biological effects of multiple environmental stressors, the combined effects of elevated pCO2 and reduced salinity remain comparatively understudied. Changes in metabolic costs associated with homeostasis and feeding/digestion in response to environmental stressors may reallocate energy from growth and reproduction, affecting performance. Although these energetic trade-offs in response to changes in routine metabolic rates have been well demonstrated fewer studies have investigated how these are affected by changes in feeding plasticity. Consequently, the present study investigated the combined effects of 26 days’ exposure to elevated pCO2 (500 µatm and 1000 µatm) and reduced salinity (30, 23, and 16) on the energy available for growth and performance (Scope for Growth) in M. edulis and C. intestinalis, and the role of metabolic rate (oxygen uptake) and feeding plasticity [clearance rate (CR) and absorption efficiency] in this process. In M. edulis exposure to elevated pCO2 resulted in a 50% reduction in Scope for Growth. However, elevated pCO2 had a much greater effect on C. intestinalis, with more than a 70% reduction in Scope for Growth. In M. edulis negative responses to elevated pCO2 are also unlikely be further affected by changes in salinity between 16 and 30. Whereas, under future predicted levels of pCO2C. intestinalis showed 100% mortality at a salinity of 16, and a >90% decrease in Scope for Growth with reduced biomass at a salinity of 23. Importantly, this work demonstrates energy available for production is more dependent on feeding plasticity, i.e. the ability to regulate CR and absorption efficiency, in response to multiple stressors than on more commonly studied changes in metabolic rates.
Posts Tagged 'salinity'
Feeding plasticity more than metabolic rate drives the productivity of economically important filter feeders in response to elevated CO2 and reduced salinity
Published 20 December 2018 Science ClosedTags: biological response, chordata, laboratory, mollusks, multiple factors, North Atlantic, physiology, salinity
Sensitivity to near-future CO2 conditions in marine crabs depends on their compensatory capacities for salinity change
Published 26 October 2018 Science ClosedTags: biological response, crustaceans, laboratory, molecular biology, morphology, multiple factors, physiology, salinity
Marine crabs inhabit shallow coastal/estuarine habitats particularly sensitive to climate change, and yet we know very little about the diversity of their responses to environmental change. We report the effects of a rarely studied, but increasingly prevalent, combination of environmental factors, that of near-future pCO2 (~1000 µatm) and a physiologically relevant 20% reduction in salinity. We focused on two crab species with differing abilities to cope with natural salinity change, and revealed via physiological and molecular studies that salinity had an overriding effect on ion exchange in the osmoregulating shore crab, Carcinus maenas. This species was unaffected by elevated CO2, and was able to hyper-osmoregulate and maintain haemolymph pH homeostasis for at least one year. By contrast, the commercially important edible crab, Cancer pagurus, an osmoconformer, had limited ion-transporting capacities, which were unresponsive to dilute seawater. Elevated CO2 disrupted haemolymph pH homeostasis, but there was some respite in dilute seawater due to a salinity-induced metabolic alkalosis (increase in HCO3− at constant pCO2). Ultimately, Cancer pagurus was poorly equipped to compensate for change, and exposures were limited to 9 months. Failure to understand the full spectrum of species-related vulnerabilities could lead to erroneous predictions of the impacts of a changing marine climate.
Effects of ocean acidification on salinity tolerance and seawater growth of Atlantic salmon Salmo salar smolts
Published 15 October 2018 Science ClosedTags: biological response, fish, laboratory, multiple factors, physiology, salinity
Human activity has resulted in increasing atmospheric carbon dioxide (CO2), which will result in reduced pH and higher levels of CO2 in the ocean, a process known as ocean acidification. Understanding the effects of ocean acidification (OA) on fishes will be important to predicting and mitigating its consequences. Anadromous species such as salmonids may be especially at risk because of their rapid movements between fresh water and seawater, which could minimize their ability to acclimate. In the present study, we examine the effect of future OA on the salinity tolerance and early seawater growth of Atlantic salmon Salmo salar smolts. Exposure to 610 and 1010 μatm CO2 did not alter salinity tolerance but did result in slightly lower plasma chloride levels in smolts exposed to seawater compared with controls (390 μatm). Gill Na+–K+‐ATPase activity, plasma cortisol, glucose and haematocrit after seawater exposure were not altered by elevated CO2. Growth rate in the first 2 weeks of seawater exposure was greater at 1010 μatm CO2 than under control conditions. This study of the effects of OA on S. salar during the transition from fresh water to seawater indicates that elevated CO2 is not likely to affect osmoregulation negatively and may improve early growth in seawater.
Trophic functioning of macrobenthic fauna in a tropical acidified Bornean estuary (Southeast Asia)
Published 29 August 2018 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, field, multiple factors, North Pacific, otherprocess, salinity
The trophic structure of a community is used to infer ecosystem functioning (e.g. energy transfer and nutrient cycling). Here the trophic structure of the benthic infaunal and epifaunal communities in the Brunei Estuary are characterized, and their distribution along an estuarine pH gradient is analyzed using univariate and multivariate techniques. This analysis revealed that surface deposit feeders (e.g., polychaetes) were numerically dominant within the infaunal communities whereas in the epifaunal communities filter feeders (e.g., bivalves) were highly abundant. Species richness for almost all trophic groups increased toward the lower estuary, except for omnivores in the epifaunal communities, which decreased markedly. Both Analysis of Variance (ANOVA) and Analysis of Similarities (ANOSIM) detected significant differences in the density of respective trophic groups among stations. Within infaunal communities, both Biological and Environmental procedure (BIO-ENV) and Canonical Correspondence Analysis (CCA) showed that trophic shifts were associated with environmental gradients. Surface-deposit feeders and omnivores were the most abundant macrobenthos of the upper estuary characterized by low salinity, low pH, and a higher percentage of mud particles. The proportion of filter feeders and carnivores increased with salinity/pH and sand. A more uniform distribution of trophic structure was found in the lower estuary, with high salinity and pH over sandy habitat. In contrast, within epifaunal trophic groups, the percentage of surface deposit feeders and omnivores declined, but filter feeders remarkably increased toward the sea. The proportion of carnivores remained similar at all stations. Non-Metric Multidimensional Scaling (nMDS) ordination for epifaunal trophic groups clearly demarcated higher salinity/pH stations from lower salinity/pH stations, suggesting different trophic compositions along the estuarine pH gradient.
Analysis of Na+/K+ -ATPase gene expression and physiological parameters in the crab Callinectes danae submitted to future scenarios of ocean acidification in the laboratory (in Portuguese)
Published 31 July 2018 Science ClosedTags: biological response, crustaceans, laboratory, molecular biology, multiple factors, physiology, salinity, South Atlantic
Oceanic acidification, a process resulting from the emission of carbon dioxide (CO2) in the atmosphere by activities of anthropic nature, has been causing in recent decades a change in the chemical balance of the bicarbonate / carbonate system and consequently a decrease in the pH of the oceans. Estimates indicate that this decrease can be 0.7 units per year of 2300, which can affect the growth, reproduction and even survival of the species. In this sense, studies are needed to evaluate the impact of oceanic acidification on physiological and molecular levels in different marine species. The Callinectes danae crab is an important ecological and economic resource of the Region of the Baixada Santista and inhabitant of different ranges of salinity. The present study evaluated the effects of ocean acidification on C. danae crab on a set of physiological parameters (oxygen consumption, ammonia excretion, O: N ratio, hepatosomatic index and osmo-and ionoregulatory capacity of hemolymph), and gene expression of Na + / K + – ATPase, an important enzyme in the process of osmoregulation and acid base balance. The animals were kept at different salinities (20, 25, 30, 35 and 40) and at pHs 8.0 (control) and 7.3 (acidified) for a period of three and thirty days. It was observed an increase in the oxygen consumption in salinities 25 (3 days), 20 and 40 (30 days) probably due to a greater energy requirement for the maintenance of systems related to acid-base regulation. Metabolic depression was also observed at the salinity of 30 (30 days). Ammonia excretion decreased in salinities 30 (3 days), 25, 30 and 35 (30 days) possibly due to competition between Na + / H + and Na + / NH + 4 transporters. The hepatosomatic index had an increase in salinities of 30 (3 days) and 40 (30 days) due to a possible accumulation of reserves in stressful situations. The energy substrate and the osmoregulatory pattern remained unchanged in all treatments. However, the Cl- and Na + concentrations were reduced at the salinity of 25 and 35 (30 days), probably due to some changes in their transporters. Molecularly, a regulation of Na + / K + ATPase expression was observed, with a decrease in salinities of 35 and 40 (3 days), and a subsequent increase in the period of 30 days. The work was the first to evaluate the physiological and molecular parameters of C.danae in different salinities. Animals that remained longer on exposure to high pCO2 are more negatively affected than animals that were exposed in 3 days. The observed changes may indicate that although C. danae is an eurialan animal and inhabits different environments, ocean acidification can alter its physiological and molecular patterns, taking organisms out of their homeostasis, having consequences on the growth, development and distribution of the species.
Effects of ocean acidification and salinity variations on the physiology of osmoregulating and osmoconforming crustaceans
Published 26 June 2018 Science ClosedTags: biological response, crustaceans, laboratory, mortality, multiple factors, physiology, salinity
Survival, osmoregulatory pattern, oxygen consumption, energy spent on metabolism, ammonia excretion, type of oxidized energy substrate, and hepatosomatic index were evaluated in decapods (an osmoregulating crab, Callinectes danae, and an osmoconforming seabob shrimp, Xiphopenaeus kroyeri) exposed to carbon dioxide-induced water acidification (pH 7.3, control pH 8.0) and different salinities (20, 25, 30, 35, and 40‰) for 3 days. Compared to the animals kept at controlled pH, exposure to reduced pH resulted in the loss of osmoregulatory capacity in C. danae at all salinities, except for some hyporegulation at 40‰, and reduced oxygen consumption and ammonia excretion at 20 and 40‰. Xiphopenaeus kroyeri remained an osmoconformer in all evaluated conditions, except for some hyporegulation at 40‰, and when exposed to the reduced pH, it presented changes in oxygen consumption at all salinities and reductions in ammonia excretion at 20 and 35‰ compared to the control animals. Both species use protein as the main energy substrate and decrease the hepatosomatic index when exposed to reduced pH relative to the control. The observed changes may be associated with changes in the activity of enzymes related to osmoregulation, the use of amino acids as osmotic effectors of cell volume control and recovery, and the Bohr effect, and, because the gills are multifunctional organs related to osmoregulation, the changes may be related to acid–base control, nitrogen excretion, and respiration, with a change in one of these functions bringing about changes in the others.
Will temperature and salinity changes exacerbate the effects of seawater acidification on the marine microalga Phaeodactylum tricornutum?
Published 10 April 2018 Science ClosedTags: abundance, biological response, growth, laboratory, methods, morphology, multiple factors, otherprocess, physiology, phytoplankton, salinity, temperature
Highlights
• Combined effects of pH, temperature and salinity were studied on a marine diatom.
• A novel CO2 injection system was used for performing microalgae toxicity test.
• Synergistic effects were found on cell viability, cell size and autofluorescence.
• Results are useful to address the potential impact of climate change.
Abstract
To evaluate the effects related to the combination of potential future changes in pH, temperature and salinity on microalgae, a laboratory experiment was performed using the marine diatom Phaeodactylum tricornutum. Populations of this species were exposed during 48 h to a three-factor experimental design (3 × 2 × 2) with two artificial pH values (6, 7.4), two levels of temperature (23 °C, 28 °C), two levels of salinity (34 psu, 40 psu) and a control (pH 8, Temp 23 °C, Sal 34 psu). The effects on growth, cell viability, metabolic activity, and inherent cell properties (size, complexity and autofluorescence) of P. tricornutum were studied using flow cytometry. The results showed adverse effects on cultures exposed to pH 6 and high temperature and salinity, being the inherent cell properties the most sensitive response. Also, linked effects of these parameters resulted on cell viability and cell size decrease and an increase of cell autofluorescence. The conclusions obtained from this work are useful to address the potential effects of climate change (in terms of changes on pH, salinity and temperature) in microalgae.
Decalcification and survival of benthic foraminifera under the combined impacts of varying pH and salinity
Published 5 April 2018 Science ClosedTags: biological response, dissolution, laboratory, morphology, mortality, multiple factors, protists, salinity
- Coastal ocean acidification did not enhance apparent test dissolution or affect survival in the short term of the benthic foraminifera species Ammonia sp. and Elphidium crispum.
- Ωcalc <1 caused by low salinity decreases resistance to dissolution of the foraminifera.
- The response of foraminifera to the combined impact of low pH and desalination was species-specific.
- Living, decalcified juvenile specimens of Ammonia sp. were observed after one month at salinity 5.
Abstract
Coastal areas display natural large environmental variability such as frequent changes in salinity, pH, and carbonate chemistry. Anthropogenic impacts – especially ocean acidification – increase this variability, which may affect the living conditions of coastal species, particularly, calcifiers. We performed culture experiments on living benthic foraminifera to study the combined effects of lowered pH and salinity on the calcification abilities and survival of the coastal, calcitic species Ammonia sp. and Elphidium crispum. We found that in open ocean conditions (salinity ∼35) and lower pH than usual values for these species, the specimens displayed resistance to shell (test) dissolution for a longer time than in brackish conditions (salinity ∼5 to 20). However, the response was species specific as Ammonia sp. specimens survived longer than E. crispum specimens when placed in the same conditions of salinity and pH. Living, decalcified juveniles of Ammonia sp. were observed and we show that desalination is one cause for the decalcification. Finally, we highlight the ability of foraminifera to survive under Ωcalc < 1, and that high salinity and [Ca2+] as building blocks are crucial for the foraminiferal calcification process.
Ocean acidification and desalination: climate-driven change in a Baltic Sea summer microplanktonic community
Published 20 March 2018 Science ClosedTags: abundance, Baltic, biogeochemistry, biological response, BRcommunity, chemistry, community composition, field, laboratory, multiple factors, otherprocess, photosynthesis, phytoplankton, primary production, prokaryotes, salinity
Helcom scenario modelling suggests that the Baltic Sea, one of the largest brackish-water bodies in the world, could expect increased precipitation (decreased salinity) and increased concentration of atmospheric CO2 over the next 100 years. These changes are expected to affect the microplanktonic food web, and thereby nutrient and carbon cycling, in a complex and possibly synergistic manner. In the Baltic Proper, the extensive summer blooms dominated by the filamentous cyanobacteria Aphanizomenon sp., Dolichospermum spp. and the toxic Nodularia spumigena contribute up to 30% of the yearly new nitrogen and carbon exported to the sediment. In a 12 days outdoor microcosm experiment, we tested the combined effects of decreased salinity (from 6 to 3) and elevated CO2 concentrations (380 and 960 µatm) on a natural summer microplanktonic community, focusing on diazotrophic filamentous cyanobacteria. Elevated pCO2 had no significant effects on the natural microplanktonic community except for higher biovolume of Dolichospermum spp. and lower biomass of heterotrophic bacteria. At the end of the experimental period, heterotrophic bacterial abundance was correlated to the biovolume of N. spumigena. Lower salinity significantly affected cyanobacteria together with biovolumes of dinoflagellates, diatoms, ciliates and heterotrophic bacteria, with higher biovolume of Dolichospermum spp. and lower biovolume of N. spumigena, dinoflagellates, diatoms, ciliates and heterotrophic bacteria in reduced salinity. Although the salinity effects on diatoms were apparent, they could not clearly be separated from the influence of inorganic nutrients. We found a clear diurnal cycle in photosynthetic activity and pH, but without significant treatment effects. The same diurnal pattern was also observed in situ (pCO2, pH). Thus, considering the Baltic Proper, we do not expect any dramatic effects of increased pCO2 in combination with decreased salinity on the microplanktonic food web. However, long-term effects of the experimental treatments need to be further studied, and indirect effects of the lower salinity treatments could not be ruled out. Our study adds one piece to the complicated puzzle to reveal the combined effects of increased pCO2 and reduced salinity levels on the Baltic microplanktonic community.
Short-term exposure of Mytilus coruscus to decreased pH and salinity change impacts immune parameters of their haemocytes
Published 7 March 2018 Science ClosedTags: biological response, laboratory, mollusks, multiple factors, physiology, salinity
With the release of large amounts of CO2, ocean acidification is intensifying and affecting aquatic organisms. In addition, salinity also plays an important role for marine organisms and fluctuates greatly in estuarine and coastal ecosystem, where ocean acidification frequently occurs. In present study, flow cytometry was used to investigate immune parameters of haemocytes in the thick shell mussel Mytilus coruscus exposed to different salinities (15, 25, and 35‰) and two pH levels (7.3 and 8.1). A 7-day in vivo and a 5-h in vitro experiments were performed. In both experiments, low pH had significant effects on all tested immune parameters. When exposed to decreased pH, total haemocyte count (THC), phagocytosis (Pha), esterase (Est), and lysosomal content (Lyso) were significantly decreased, whereas haemocyte mortality (HM) and reactive oxygen species (ROS) were increased. High salinity had no significant effects on the immune parameters of haemocytes as compared with low salinity. However, an interaction between pH and salinity was observed in both experiments for most tested haemocyte parameters. This study showed that high salinity, low salinity and low pH have negative and interactive effects on haemocytes of mussels. As a consequence, it can be expected that the combined effect of low pH and changed salinity will have more severe effects on mussel health than predicted by single exposure.
DISCO – Drivers and impacts of coastal ocean acidification
Published 6 December 2017 Science ClosedTags: Baltic, biological response, chemistry, community composition, dissolution, field, multiple factors, North Atlantic, otherprocess, paleo, protists, salinity
Ocean acidification, mainly attributed to the increasing anthropogenic CO2 in the atmosphere, is characterised by a lowering pH together with a shift in the sea water carbonate chemistry toward lower concentration of carbonate ions. On the coasts, where the environmental variability is high due to natural and human impacts, ocean acidification mainly affects the frequency, magnitude, and duration of lower pH and lower calcium carbonate saturation events. Coastal ecosystems are adapted to environmental variability such as frequent changes in salinity, temperature, pH, oxygen levels and organic matter content. However, the effects of an increase of the range of this variability on coastal species, and especially on calcifiers, are still not clear. In this context, this thesis explores the impacts of coastal ocean acidification combined with other environmental stressors on benthic foraminifera.
In the Skagerrak-Baltic Sea region, foraminifera faunas varied along a strong gradient in terms of salinity, pH, and dissolved oxygen concentration, and species were adapted to local environmental stressors. However, the specimens of Ammonia spp. and Elphidium spp. observed in the south Baltic Sea were partially to completely dissolved, probably due to a combination of different stressors affecting the required energy for biomineralisation.
In a culture study, the coastal species Ammonia spp. and E. crispum were found to be resistant to dissolution under varying salinity and pH, which reflects the environmental variations in their natural habitats. However, their resistance to lower pH is decreased when cultured in brackish water conditions, and living decalcified specimens were also observed under a salinity of 5. This underlines the importance of a high salinity in the calcification process of foraminifera.
At the entrance of the Baltic Sea, environmental changes during the last 200 years were reconstructed using foraminiferal faunas. Four periods were identified with varying oxygen levels, salinity, organic matter content, and pollution with lower pH. This highlights that foraminiferal faunas were able to adapt to multiple environmental stressors.
This thesis concludes that, even if coastal species of foraminifera can tolerate extremely varying conditions in their environment on the short term, it is likely that tolerance thresholds will be passed for benthic ecosystems under the future increase in anthropogenic impacts such as coastal ocean acidification.
Further studies of micro-organisms such as foraminifera will be necessary to improve our understanding of past environmental changes and to put present and future changes into a larger context.
Continue reading ‘DISCO – Drivers and impacts of coastal ocean acidification’
Effects of alkalinity and salinity at low and high light intensity on hydrogen isotope fractionation of long-chain alkenones produced by Emiliania huxleyi
Published 21 August 2017 Science ClosedTags: biological response, growth, laboratory, light, multiple factors, physiology, phytoplankton, salinity
Over the last decade, hydrogen isotope fractionation of long-chain alkenones have been shown to be a promising proxy for reconstructing paleo sea surface salinity due to a strong hydrogen isotope fractionation response to salinity across different environmental conditions. However, to date, the decoupling of the effects of alkalinity and salinity, parameters that co-vary in the surface ocean, on hydrogen isotope fractionation of alkenones has not been assessed. Furthermore, as the alkenone-producing haptophyte, Emiliania huxleyi, is known to grow in large blooms under high light intensities, the effect of salinity on hydrogen isotope fractionation under these high irradiances is important to constrain before using hydrogen isotope fractionation to reconstruct paleosalinity. Batch cultures of the marine haptophyte E. huxleyi strain CCMP 1516 were grown to investigate the hydrogen isotope fractionation response to salinity at high light intensity and independently assess the effects of salinity and alkalinity. Our results suggest that alkalinity does not significantly influence hydrogen isotope fractionation of alkenones, but salinity does have a strong effect. Additionally, no significant difference was observed between the fractionation responses to salinity recorded in alkenones grown under both high and low light conditions. Comparison with previous studies suggests that the fractionation response to salinity in culture is similar under different environmental conditions, strengthening the applicability of hydrogen isotope fractionation as a paleosalinity proxy.
The future for microplankton in the Baltic Sea – Effects of SWS and climate change
Published 2 May 2017 Science ClosedTags: abundance, Baltic, biological response, BRcommunity, chemistry, community composition, field, laboratory, multiple factors, otherprocess, photosynthesis, phytoplankton, prokaryotes, protists, salinity, temperature, zooplankton
The Baltic Sea is located between 53°N to 66°N and from 10°E to 30°E and is the second largest brackish water body in the world. It consists of several basins where the Baltic Proper is the major water mass. Around 85 million people live in the catchment area of the Baltic Sea, which subjects it to a range of environmental pressures, such as increased nutrient inputs from human activities (eutrophication), shipping, over-fishing, acid rain and trace metals released from anti-fouling paint. All these stressors, combined with low alkalinity, variable salinity and limited water exchange, makes the Baltic Sea a very sensitive area that may be less resilient to future stressors such as climate change or increased shipping activities. Microplankton communities consist of small heterotrophic bacteria, picoplankton, phytoplankton, cyanobacteria and smaller grazers, such as ciliates and zooplankton. In the Baltic Proper, there is a succession of blooms, within the microplankton community, from diatoms and dinoflagellates in the early spring to cyanobacteria during summer and ending with a second diatom and dinoflagellate bloom in the autumn. The cyanobacteria of the Baltic Proper bloom every summer and are dominated by Aphanizomenon sp. and Nodularia spumigena. Dolichospermum spp. is present but is less abundant. The effects of climate change were tested on a natural microplankton community, as well as on isolated cyanobacteria species from the Baltic Sea. To simulate effects of climate change, the temperature was increased from 12°C to 16°C, salinity decreased from 6-7 to 3-4 and atmospheric pCO2-levels was increased from 380 ppm to 960 ppm. The biovolume of Aphanizomenon sp. and N. spumigena increased when temperature was increased by 4°C. When salinity was decreased by three units, both the growth and photosynthetic activity of N. spumigena were reduced while Aphanizomenon sp. was unaffected, and the growth of Dolichospermum sp. was increased. Furthermore, present-day salinities were beneficial, in terms of increased biovolumes, of diatoms, dinoflagellates and ciliates, compared to reduced future salinity. Increased atmospheric pCO2 had no effect on any of the species in the microplankton community. These results show that the future microplankton community may be positive, in terms of increased biovolume, for the cyanobacteria species Aphanizomenon sp. and Dolichospermum spp. An increase of cyanobacteria blooms may open up to the possibility to grow and/or harvest these species as a source of biofuel or fatty acids (FA). Dolichospermum sp. yielded higher total FA content per biovolume, compared to the other two cyanobacteria species in phosphorus-depleted medium and Aphanizomenon sp. in nitrogen-depleted medium. Natural nutrient levels in the Baltic Proper are low both in nitrogen and phosphorus, which indicates a possible future market for biofuel and FA technologies. Additionally, the effects of seawater scrubbing (SWS) were tested on a natural summer-bloom microplankton community. Three different concentrations of scrubber water were added; 1%, 3% and 10%. To elucidate effects of decreased pH alone, water acidified with H2SO4 was added in equal concentrations. The six treatments were compared to a control without acidifying substances. SWS or the corresponding pH treatments, did not have a direct effect on microplankton species composition and biovolume. However, the increased amount of Cu and Zn in the scrubber water, combined with significant decrease in pH and alkalinity already at the 1% scrubber water treatment calls for precaution when implementing scrubber units on the shipping fleet of the Baltic Sea. The accumulated effects of long-term repeated addition constantly throughout the year, i.e. in a shipping lane, are yet to be elucidated.
A combination of salinity and pH affects the recruitment of Gladioferens pectinatus (Brady) (Copepoda; Calanoida)
Published 18 April 2017 Science ClosedTags: biological response, crustaceans, laboratory, morphology, multiple factors, physiology, reproduction, salinity, zooplankton
Carbon dioxide levels in many estuaries fluctuate and, in several cases, reach extremes much higher than those predicted for oceans by the end of the century. Moreover, estuaries are characterized by natural fluctuations in salinity, and reduced pH, from increased pCO2, exposes estuarine organisms to multiple stresses. Although the effects of low pH on the reproduction of several marine copepod species have been assessed, studies examining effects of pH in estuarine copepod species are extremely scarce. Here, we aim at understanding the reproductive response of Gladioferens pectinatus to the stress posed by both salinity and pH. G. pectinatus was exposed to salinities 2 and 10, at four different pH levels each. Our results show no impairment in the brood size, embryonic development time and hatching success under low pH levels at either salinities. However, at salinity 2, the percentage of nauplii growing into adults significantly decreased at low pH, whereas at salinity 10, no major effect was observed. We argue that the combination of osmoregulation and acidity induced stress response can affect the development of nauplii and copepodites, as well as adult recruitment, likely due to energy reallocation and molting impairment. We also argue that resilience and phenotypic plasticity highly influence the ability of different copepod species and populations to reproduce and grow under stressful combinations of environmental parameters. This study points out the importance of understanding the effects of multiple stresses or parameters on the adaptability of organisms to water acidification.
The effects of salinity and pH on fertilization, early development, and hatching in the crown-of-thorns seastar
Published 28 February 2017 Science ClosedTags: biological response, echinoderms, laboratory, morphology, multiple factors, reproduction, salinity, South Pacific
Understanding the influence of environmental factors on the development and dispersal of crown-of-thorns seastars is critical to predicting when and where outbreaks of these coral-eating seastars will occur. Outbreaks of crown-of-thorns seastars are hypothesized to be driven by terrestrial runoff events that increase nutrients and the phytoplankton food for the larvae. In addition to increasing larval food supply, terrestrial runoff may also reduce salinity in the waters where seastars develop. We investigated the effects of reduced salinity on the fertilization and early development of seastars. We also tested the interactive effects of reduced salinity and reduced pH on the hatching of crown-of-thorns seastars. Overall, we found that reduced salinity has strong negative effects on fertilization and early development, as shown in other echinoderm species. We also found that reduced salinity delays hatching, but that reduced pH, in isolation or in combination with lower salinity, had no detectable effects on this developmental milestone. Models that assess the positive effects of terrestrial runoff on the development of crown-of-thorns seastars should also consider the strong negative effects of lower salinity on early development including lower levels of fertilization, increased frequency of abnormal development, and delayed time to hatching.
Adult exposure to ocean acidification is maladaptive for larvae of the Sydney rock oyster Saccostrea glomerata in the presence of multiple stressors
Published 16 February 2017 Science ClosedTags: biological response, laboratory, mollusks, morphology, mortality, multiple factors, nutrients, physiology, salinity, South Pacific, temperature
Parental effects passed from adults to their offspring have been identified as a source of rapid acclimation that may allow marine populations to persist as our surface oceans continue to decrease in pH. Little is known, however, whether parental effects are beneficial for offspring in the presence of multiple stressors. We exposed adults of the oyster Saccostrea glomerata to elevated CO2 and examined the impacts of elevated CO2 (control = 392; 856 µatm) combined with elevated temperature (control = 24; 28°C), reduced salinity (control = 35; 25) and reduced food concentration (control = full; half diet) on their larvae. Adult exposure to elevated CO2 had a positive impact on larvae reared at elevated CO2 as a sole stressor, which were 8% larger and developed faster at elevated CO2 compared with larvae from adults exposed to ambient CO2. These larvae, however, had significantly reduced survival in all multistressor treatments. This was particularly evident for larvae reared at elevated CO2 combined with elevated temperature or reduced food concentration, with no larvae surviving in some treatment combinations. Larvae from CO2-exposed adults had a higher standard metabolic rate. Our results provide evidence that parental exposure to ocean acidification may be maladaptive when larvae experience multiple stressors.
Plasticity and inter-population variability in physiological and life-history traits of the mussel Mytilus chilensis: A reciprocal transplant experiment
Published 13 February 2017 Science ClosedTags: biological response, calcification, field, molecular biology, mollusks, morphology, multiple factors, physiology, salinity
Geographically widespread species must cope with environmental differences between habitats. Information concerning geographic variations in response to climate variability is critical because many morphological, life-history and physiological traits show variation across space. Reciprocal transplant experiments have shown to be relevant to evaluate the role of phenotypic plasticity and potential local adaptation in ecophysiological responses when coping with environmental variability. In this study, we characterize through reciprocal transplant experiments the reaction norms of morphological, biochemical, physiological and life-history traits between two intertidal populations of the socioeconomically important mussel Mytilus chilensis, inhabiting contrasting local environments (estuarine vs coastal habitats). We found a gradient in phenotypic plasticity with plastic trait responses in metabolic, ingestion and clearance rates, and in HsP70 gene expression, and some traits with responses more canalized as growth and calcification rates. This emphasizes that responses not only vary across different local populations but also in different traits in M. chilensis, thus it is difficult to establish an overall trend of the responses at integrated organismal level. Moreover, the synergistic interaction of factors such as salinity and carbonate system parameters evaluated make it necessary to study the response at the population level with emphasis on benthic species important in aquaculture. Finally, field studies such as this one are useful for documenting the patterns of traits variation that occur in nature, identifying possible causes of such variation, and generating testable hypotheses for future controlled experiments.
Environmental drivers of coccolithophore abundance and calcification across Drake Passage (Southern Ocean) (update)
Published 2 November 2016 Science ClosedTags: abundance, Antarctic, biological response, BRcommunity, calcification, chemistry, community composition, field, light, morphology, multiple factors, nutrients, otherprocess, phytoplankton, primary production, salinity, temperature
Although coccolithophores are not as numerically common or as diverse in the Southern Ocean as they are in subpolar waters of the North Atlantic, a few species, such as Emiliania huxleyi, are found during the summer months. Little is actually known about the calcite production (CP) of these communities or how their distribution and physiology relate to environmental variables in this region. In February 2009, we made observations across Drake Passage (between South America and the Antarctic Peninsula) of coccolithophore distribution, CP, primary production, chlorophyll a and macronutrient concentrations, irradiance and carbonate chemistry. Although CP represented less than 1 % of total carbon fixation, coccolithophores were widespread across Drake Passage. The B/C morphotype of E. huxleyi was the dominant coccolithophore, with low estimates of coccolith calcite (∼ 0.01 pmol C coccolith−1) from biometric measurements. Both cell-normalised calcification (0.01–0.16 pmol C cell−1 d−1) and total CP (< 20 µmol C m−3 d−1) were much lower than those observed in the subpolar North Atlantic where E. huxleyi morphotype A is dominant. However, estimates of coccolith production rates were similar (0.1–1.2 coccoliths cell−1 h−1) to previous measurements made in the subpolar North Atlantic. A multivariate statistical approach found that temperature and irradiance together were best able to explain the observed variation in species distribution and abundance (Spearman’s rank correlation ρ = 0.4, p < 0.01). Rates of calcification per cell and coccolith production, as well as community CP and E. huxleyi abundance, were all positively correlated (p < 0.05) to the strong latitudinal gradient in temperature, irradiance and calcite saturation states across Drake Passage. Broadly, our results lend support to recent suggestions that coccolithophores, especially E. huxleyi, are advancing polewards. However, our in situ observations indicate that this may owe more to sea-surface warming and increasing irradiance rather than increasing CO2 concentrations.
Effects of pH and salinity on juvenile hatchery-reared red drum
Published 14 October 2016 Science ClosedTags: biological response, fish, growth, laboratory, mortality, multiple factors, physiology, salinity
Climate change with concomitant ocean acidification presents a problem to coastal ecosystems, including estuaries. It is well-documented that fish growth, development, and survival are dependent on environmental factors such as temperature and salinity. Considering the economic and recreational importance of red drum (Sciaenops ocellatus), it is important to understand both acute and long-term effects of environmental change on juveniles released into native waters as part of stock enhancement programs. Experiments were designed to compare survival, growth and body composition of juvenile red drum grown under different salinity and pH treatments.
Research was conducted in a closed recirculating system with juvenile red drum (42±9.9 mm) randomly stocked at a density of 13 fish/tank and fed daily to satiation (∼6% body weight). Fish were subjected to salinity treatments of 40 or 30 and a pH of either7.5, 8.1, 8.5, or 9.0 (n = 8 replicates per treatment). Each trial was conducted for 14 days.
Results show that at a salinity of 40, there was a significant difference between survival of the juvenile red drum at pH 7.5 and 9.0 (p=0.03). Survival was not significant between pH levels at salinity of 30. Results indicated pH had no significant effect on specific growth rate (SGR, p ≥ 0.05); however, increased salinity significantly decreased growth (p< 0.05), and there was a significant interaction between pH and salinity. There was no significant impact from pH or salinity on protein retention (p≥0.05). At 40 the whole body ash increased as pH increased (p=0.003). Ash was also significantly different between pH values at salinity 30 (p=0.02). Whole body energy was not significantly affected by pH (p ≥ 0.05); but increased salinity caused a significant decrease in energy retention (p < 0.05), and there was no significant interaction between pH and salinity affecting energy retention.
These results indicate that salinity is a more critical factor to consider than pH when engaging in stock enhancement efforts, especially at high salinity. The results of this study will help fisheries managers increase the rate of survival of hatchery-reared red drum when released into the wild. The results indicate that research should be conducted to investigate the effects of hypersalinity (>40) and pH on juvenile red drum as related to growth rates, and growth hormone production. Future research should also focus on the long term effects of low and high pH exposure of juveniles to adult life stages, and should examine otolith development, behavior and the effects on reproduction of red drum.
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Quantitative analysis of oyster larval proteome provides new insights into the effects of multiple climate change stressors
Published 7 July 2016 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, morphology, multiple factors, North Pacific, physiology, salinity, temperature
The metamorphosis of planktonic larvae of the Pacific oyster (Crassostrea gigas) underpins their complex life-history strategy by switching on the molecular machinery required for sessile life and building calcite shells. Metamorphosis becomes a survival bottleneck, which will be pressured by different anthropogenically induced climate change-related variables. Therefore, it is important to understand how metamorphosing larvae interact with emerging climate change stressors. To predict how larvae might be affected in a future ocean, we examined changes in the proteome of metamorphosing larvae under multiple stressors: decreased pH (pH 7.4), increased temperature (30 °C), and reduced salinity (15 psu). Quantitative protein expression profiling using iTRAQ-LC-MS/MS identified more than 1300 proteins. Decreased pH had a negative effect on metamorphosis by down-regulating several proteins involved in energy production, metabolism, and protein synthesis. However, warming switched on these down-regulated pathways at pH 7.4. Under multiple stressors, cell signaling, energy production, growth, and developmental pathways were up-regulated, although metamorphosis was still reduced. Despite the lack of lethal effects, significant physiological responses to both individual and interacting climate change related stressors were observed at proteome level. The metamorphosing larvae of the C. gigas population in the Yellow Sea appear to have adequate phenotypic plasticity at the proteome level to survive in future coastal oceans, but with developmental and physiological costs.
