Posts Tagged 'salinity'

Effects of seawater salinity and pH on cellular metabolism and enzyme activities in biomineralizing tissues of marine bivalves

Highlights

•Effects of salinity and pH on cellular metabolism were studied in bivalves.

•Biomineralizing cells had robust metabolism in the studied salinity and pH range.

•Oxygen consumption and protein synthesis rates declined at low pH.

•Na+/K+ ATPase activity increased at low salinity.

•H+ and Ca2+ transport activities were little affected by salinity and pH variation.

Abstract

Molluscan shell formation is a complex energy demanding process sensitive to the shifts in seawater CaCO3 saturation due to changes in salinity and pH. We studied the effects of salinity and pH on energy demand and enzyme activities of biomineralizing cells of the Pacific oyster (Crassostrea gigas) and the hard-shell clam (Mercenaria mercenaria). Adult animals were exposed for 14 days to high (30), intermediate (18), or low (10) salinity at either high (8.0-8.2) or low (7.8) pH. Basal metabolic cost as well as the energy cost of the biomineralization-related cellular processes were determined in isolated mantle edge cells and hemocytes. The total metabolic rates were similar in the hemocytes of the two studied species, but considerably higher in the mantle cells of C. gigas compared with those of M. mercenaria. Cellular respiration was unaffected by salinity in the clams’ cells, while in oysters’ cells the highest respiration rate was observed at intermediate salinity (18). In both studied species, low pH suppressed cellular respiration. Low pH led to an upregulation of Na+/K+ ATPase activity in biomineralizing cells of oysters and clams. Activities of Ca2+ ATPase and H+ ATPase, as well as the cellular energy costs of Ca2+ and H+ transport in the biomineralizing cells were insensitive to the variation in salinity and pH in the clams and oysters. Species-specific variability in cellular response to low salinity and pH indicates that the disturbance of shell formation under these conditions has different underlying mechanisms in the two studied species.

Continue reading ‘Effects of seawater salinity and pH on cellular metabolism and enzyme activities in biomineralizing tissues of marine bivalves’

The combined effects of salinity and pH on shell biomineralization of the edible mussel Mytilus chilensis

Highlights

• Coastal habitats such as estuaries show high environmental variability.

• pH and salinity impact on the periostracum organic composition.

• pH and salinity impact on the shell mineral organization.

• Salinity modulates the impact of pH on shell weight.

• The level of plasticity in shell properties differs with time exposure.

Abstract

Coastal ecosystems influenced by river discharges are subjected to important environmental changes. Understanding how marine biota cope with its environment is relevant in predicting the responses to future conditions imposed by climate change. To date, a large number of studies have addressed the role of pH on shell and biomineralization properties on multiple calcifying species; however the role of salinity in combination with other stressors has been poorly studied. In particular, the edible mussel Mytilus chilensis, an important marine resource of the Chilean coasts, inhabits estuarine areas which show high natural variability in terms of pH and salinity. Here, we studied how M. chilensis shell periostracum, shell organic matrix and crystal orientation are affected by different pH (8.1 and 7.7) and salinity conditions (30, 25 and 20 psu), isolated and in combination, at different time intervals. Our results show differences in the plasticity of the different biomineralogical properties studied during the experiment under the different pH and salinity treatments. While the periostracum thickness and the total shell organic matter were not affected by pH and salinity, the periostracum organic composition did. Higher amounts of polysaccharides were observed under low pH conditions after 20 days of experiment, while after 60 days, low salinity was responsible for the decrease of the polysaccharides and proteins in the periostracum. Low salinity also produced a major disorder in crystal organization at the outer shell surface. Finally, total shell weight was only affected by low pH conditions under lower salinity conditions (20 psu). From the results, in the majority of the shell properties observed we did not observe any combined effect of pH and salinity. Also, we detected that the magnitude of the impacts of salinity and pH are variable and time-dependent. This would be suggesting some level of acclimatization of M. chilensis to lower pH and salinity conditions.

Continue reading ‘The combined effects of salinity and pH on shell biomineralization of the edible mussel Mytilus chilensis’

Effects of multiple stressors on the development and performance of decapod crustaceans

Many marine crustacean larvae develop in a relatively stable pelagic environment; therefore, they are likely to be sensitive to perturbations in their surrounding environmental conditions. Ocean Acidification (OA) is occurring on a globalised scale and may cause disruptions to crustacean larval survival. However, species and/or life history stages are not expected to respond uniformly to these near-future predicted changes. The performance of species that lack a compensatory capacity to cope with the changing conditions may potentially be detrimentally affected, which in turn may impact recruitment. In addition to this, little information exists surrounding the impacts of ocean acidification in conjunction with additional environmental stressors, such as salinity, temperature and food availability, which are predicted to covary with OA, upon brachyuran crustacean larvae. This research focused on the effects of elevated CO2, in combination with other environmental stressors, upon rates of larval development, performance and survival of a brachyuran crustacean species common to Europe (Carcinus maenas) and two species of shrimp (Palaemon serratus and Palaemon varians). These species have varying physiological abilities to cope with salinity change and such attributes may influence their capacities to survive elevated CO2 in combination with other environmental changes. Exposure of early larval stages to combinations of salinity, temperature and food limitation in C. maenas revealed that high temperature ameliorated the effect of low salinity on survival and developmental duration. Limited access to food also affected developmental duration, but exposure to elevated CO2 alone in a second experiment only affected survival, and low salinity alone had no effect. Exposure of early juvenile stages of C. maenas to CO2 and salinity, revealed that developmental duration was significantly affected by elevated CO2 and/or salinity at varying levels, whereas, for survival, such influences were only observed in later juvenile stages. These results suggest the possibility of a physiologically sensitive bottleneck within the life cycle of C. maenas. Exposure of early larval stages of the estuarine species, P. varians, to CO2 and salinity had no effect on either survival or developmental duration. For the predominantly coastal species, P. serratus, developmental duration was negatively influenced by the interaction of elevated CO2 and low salinity, but there was limited observed effect on overall survival at the early stages studied. Overall, evaluations of the effects of climate driven variables on physiological performance demonstrated that differences can occur among broods. In future, further studies are required to incorporate seasonal (and possibly spatial) variability in responses, due to maternal effects or phenotypic variation, as conclusions based on individuals collected over a short time frame are unlikely to fully represent population level responses.

Continue reading ‘Effects of multiple stressors on the development and performance of decapod crustaceans’

pH and other upwelling hydrographic drivers in regulating copepod reproduction during the 2015 El Niño event: a follow-up study

Highlights

• High salinity El Niño 2015 overlaid continuous low pH values observed in the upwelling site.

• Environmental pH-salinity and phenological regulation were detected in copepod reproduction.

• Upwelling pH-variations and high salinity El Niño events can underpin plankton responses to climate change.

Abstract

The combined upwelling-El Niño (EN) event regulation of the numerically dominant Acartia tonsa (Crustacea, Copepoda) reproduction was examined in a year-round upwelling system (23°S) of the Humboldt Eastern Boundary Upwelling System (EBUS) during the EN 2015. A previous analysis of the environmental regulation of this system is extended here by considering complementary oceanographic information (sea level, stratification indexes) and additional reproductive traits, such as maximum (MaxEPR), median (MedianEPR) and prevalence of egg producing females over a period of six months. Furthermore, field minimum-maximum pH levels were reproduced in three 96-h incubation experiments conducted under variable salinity conditions to evaluate copepod mean EPR, egg size and hatching success. Supporting previous assertions, the warm-high salinity EN 2015 was observed in the study site separately from hydrographic conditions associated with upwelling to non-upwelling regimes. Analysis of similarity-distance (Distance based Linear Model (DistLM)) and normalized data (separate-slope comparison under a General Linear Model (GLM)) showed that reproductive traits were regulated by specific combinations of ambient conditions, and that this regulation was also sensitive to the prevailing hydrographic regime. Thus, upwelling to non-upwelling transitions changing the pH, and EN-associated salinity and stratification shifts, were significantly and strongly linked to almost all reproductive traits (DistLM). Slope comparison (GLM) indicated MaxEPR and MedianEPR variations also underlie the phenology, highlighting the relationship between pH and salinity with biological variations. In conjunction with experimental observations, the current study consistently suggests that pH-variations in the upwelling realm, and EN hydrographic perturbations might underpin responses of plankton populations to climate change in productive EBUS.

Continue reading ‘pH and other upwelling hydrographic drivers in regulating copepod reproduction during the 2015 El Niño event: a follow-up study’

Impacts of temperature, CO2, and salinity on phytoplankton community composition in the western Arctic Ocean

The Arctic Ocean has been experiencing rapid warming, which accelerates sea ice melt. Further, the increasing area and duration of sea ice-free conditions enhance ocean uptake of CO2. We conducted two shipboard experiments in September 2015 and 2016 to examine the effects of temperature, CO2, and salinity on phytoplankton dynamics to better understand the impacts of rapid environmental changes on the Arctic ecosystem. Two temperature conditions (control: <3 and 5°C above the control), two CO2 levels (control: ∼300 and 300/450 μatm above the control; i.e., 600/750 μatm), and two salinity conditions (control: 29 in 2015 and 27 in 2016, and 1.4 below the control) conditions were fully factorially manipulated in eight treatments. Higher temperatures enhanced almost all phytoplankton traits in both experiments in terms of chl-a, accessory pigments and diatom biomass. The diatom diversity index decreased due to the replacement of chain-forming Thalassiosira spp. by solitary Cylindrotheca closterium or Pseudo-nitzschia spp. under higher temperature and lower salinity in combination. Higher CO2 levels significantly increased the growth of small-sized phytoplankton (<10 μm) in both years. Decreased salinity had marginal effects but significantly increased the growth of small-sized phytoplankton under higher CO2 levels in terms of chl-a in 2015. Our results suggest that the smaller phytoplankton tend to dominate in the shelf edge region of the Chukchi Sea in the western Arctic Ocean under multiple environmental perturbations.

Continue reading ‘Impacts of temperature, CO2, and salinity on phytoplankton community composition in the western Arctic Ocean’

Analysis of effects of environmental fluctuations on the marine mysid Neomysis awatschensis and its development as an experimental model animal

Highlights

• Investigation of optimized culture conditions in temperature, salinity, and pH for mysid mass-culture and development as a laboratory model

• Identification of strong correlations between growth parameter and 20E level in environmental fluctuations

• Measurement of maternal effects of environmental fluctuations on second generation

Abstract

Mysids are experimental models and are among the most important food items for animals in aquaria and that support fisheries, and even for humans, but information on their performance in controlled culture systems is still limited. We reared the marine mysid Neomysis awatschensis in a controlled laboratory system, and measured its growth, 20–hydroxyecdysone (20E) levels, molting, and survival in response to environmental fluctuations in temperature, pH, and salinity, and inferred their potential associations based on annual field sampling. The 20E levels were significantly elevated during the postnauplioid stages, and even higher levels of 20E were maintained in the adult stages than in the nauplioid stages. Values of growth parameters (i.e. total length and the lengths of the antennal scale, expod, endopod, and telson) and 20E levels were higher during a 40-day period at 25 °C than at other temperatures, with shorter intermolt intervals, although morality was also increased. Among the surviving mysids, the number of newly hatched juveniles produced was higher for females exposed to 20 °C than that in other groups. Relatively higher growth and survival rates were measured at salinities over 25 practical salinity, while lower salinities under 15 practical salinity significantly reduced growth and survival. The number of newly hatched juveniles was lower at salinities under 15 practical salinity compared to those over 20 practical salinity. Overall, low temperature and salinity reduced mysid reproduction and the maintenance of the second generation. In the case of pH variation (pH of 7.0–8.0), there were no significant effects on growth and the number of newly hatched juveniles, although the survival rate was slightly lower and the 20E level fluctuated at a pH of 7.0. We believe that these associations between growth and environmental conditions can provide crucial information for optimizing mass mysid culture for experimental and ecotoxicological usage in the laboratory.

Continue reading ‘Analysis of effects of environmental fluctuations on the marine mysid Neomysis awatschensis and its development as an experimental model animal’

Ocean freshening and acidification differentially influences mortality and behavior of the Antarctic amphipod Gondogeneia antarctica

Highlights

• Glacier retreat induced by global warming can decrease pH and salinity of the Antarctic ocean.

• The Antarctic amphipod Gondogeneia antarctica was exposed to low pH (7.6) and low salinity (27 psμ) conditions.

• Low pH increased mortality, impaired food detection, reduced shelter-use during daytime. .

• Low salinity increased cannibalism and induced abnormal swimming.

• Ocean acidification and freshening act as independent stressors influencing behavior and physiology of Antarctic amphipods.

Abstract

The Western Antarctic Peninsula (WAP) has experienced rapid atmospheric and ocean warming over the past few decades and many marine-terminating glaciers have considerably retreated. Glacial retreat is accompanied by fresh meltwater intrusion, which may result in the freshening and acidification of coastal waters. Marian Cove (MC), on King George Island in the WAP, undergoes one of the highest rates of glacial retreat. Intertidal and shallow subtidal waters are likely more susceptible to these processes, and sensitive biological responses are expected from the organisms inhabiting this area. The gammarid amphipod Gondogeneia antarctica is one of the most abundant species in the shallow, nearshore Antarctic waters, and it occupies an essential ecological niche in the coastal marine WAP ecosystem. In this study, we tested the sensitivity of G. antarctica to lowered salinity and pH by meltwater intrusion following glacial retreat. We exposed G. antarctica to four different treatments combining two salinities (34 and 27 psμ) and pH (8.0 and 7.6) levels for 26 days. Mortality, excluding cannibalized individuals, increased under low pH but decreased under low salinity conditions. Meanwhile, low salinity increased cannibalism, whereas low pH reduced food detection. Shelter use during the daytime decreased under each low salinity and pH condition, indicating that the two stressors act as disruptors of amphipod behavior. Under low salinity conditions, swimming increased during the daytime but decreased at night. Although interactions between low salinity and low pH were not observed during the experiment, the results suggest that each stressor, likely induced by glacial melting, causes altered behaviors in amphipods. These environmental factors may threaten population persistence in Marian Cove and possibly other similar glacial embayments.

Continue reading ‘Ocean freshening and acidification differentially influences mortality and behavior of the Antarctic amphipod Gondogeneia antarctica’

Elevated carbon dioxide and reduced salinity enhance mangrove seedling establishment in an artificial saltmarsh community

The global phenomenon of mangrove encroachment into saltmarshes has been observed across five continents. It has been proposed that this encroachment is driven in part by rising atmospheric CO2 concentration and reduced salinity in saltmarshes resulting from rising sea levels enhancing the establishment success of mangrove seedlings. However, this theory is yet to be empirically tested at the community-level. In this study, we examined the effect of CO2 and salinity on seedling growth of two mangrove species, Aegiceras corniculatum and Avicennia marina, grown individually and in a model saltmarsh community in a glasshouse experiment. We found that the shoot (210%) and root (91%) biomass of the saltmarsh species was significantly greater under elevated CO2. As a result, both mangrove species experienced a stronger competitive effect from the saltmarsh species under elevated CO2. Nevertheless, A. marina seedlings produced on average 48% more biomass under elevated CO2 when grown in competition with the saltmarsh species. The seedlings tended to allocate this additional biomass to growing taller suggesting they were light limited. In contrast, A. corniculatum growth did not significantly differ between CO2 treatments. However, it had on average 36% greater growth under seawater salinity compared to hypersaline conditions. Avicennia marina seedlings were not affected by salinity. From these results, we suggest that although CO2 and salinity are not universal drivers determining saltmarsh–mangrove boundaries, it is likely that rising atmospheric CO2 concentration and reduced salinity associated with sea level rise will enhance the establishment success of mangrove seedlings in saltmarshes, which may facilitate mangrove encroachment in the future.

Continue reading ‘Elevated carbon dioxide and reduced salinity enhance mangrove seedling establishment in an artificial saltmarsh community’

Reduced pH and elevated salinities affect the physiology of intertidal crab Minuca mordax (Crustacea, Decapoda)

Minuca mordax is a model for studies on ocean acidification and sea-level rise because lives in mangroves and riverbanks with low pH. We investigated the physiology of the crabs exposed to differents pH (6.5 and 5.8) and salinity (25, 30, 35, 40 45S). There was not mortality or alterations in the hypo-osmoregulation, suggesting that the factors did not affect salt absorption/secretion. Reduced pH changed metabolism, ammonia excretion, and hepatosomatic index in relation to the animals kept in control pH. At elevated salinities, metabolism increased when animals were kept in control pH, but it decreased when they were exposed to acidified pH. energy substrate, varied between proteins to a mixture of proteins and lipids. Important physiological parameters, related to the catabolism of amino acids and to the energy demand are changed and the consequences might include alterations in growth and reproduction due to the energy channeling to limiting processes of homeostasis.

Continue reading ‘Reduced pH and elevated salinities affect the physiology of intertidal crab Minuca mordax (Crustacea, Decapoda)’

Anthropogenic impacts on mangrove and saltmarsh communities in eastern Australia

The global phenomenon of mangrove encroachment into saltmarshes has been observed across five continents. It has been proposed that this encroachment is driven in part by rising atmospheric CO2 concentration and reduced salinity in saltmarshes resulting from rising sea levels enhancing the establishment success of mangrove seedlings. However, this is yet to be empirically tested at the community-level. In this study, we examined the effect of CO2 and salinity on seedling growth of two mangrove species, Aegiceras corniculatum and Avicennia
marina, grown individually and in a model saltmarsh community in a glasshouse experiment. We found that the shoot (210%) and root (91%) biomass of the saltmarsh species was significantly greater under elevated CO2. As a result, both mangrove species experienced a stronger competitive effect from the saltmarsh species under elevated CO2. Nevertheless, A. marina seedlings produced on average 48% more biomass under elevated CO2 when grown in competition with the saltmarsh species which they used to grow taller suggesting they were light
limited. In contrast, A. corniculatum growth did not significantly differ between CO2 treatments. However, it had on average 36% greater growth under seawater salinity compared to hypersaline conditions. Avicenna marina seedlings were not affected by salinity. From these results, we suggest that although CO2 and salinity are not universal drivers determining saltmarsh-mangrove boundaries, it is likely that rising atmospheric CO2 concentration and reduced salinity associated with sea level rise will enhance the establishment success of mangrove seedlings in saltmarshes, which may facilitate mangrove encroachment in the future.

Continue reading ‘Anthropogenic impacts on mangrove and saltmarsh communities in eastern Australia’


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Ocean acidification in the IPCC AR5 WG II

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