Posts Tagged 'salinity'

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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How do fungi survive in the sea and respond to climate change?

With the over 2000 marine fungi and fungal-like organisms documented so far, some have adapted fully to life in the sea, while some have the ability to tolerate environmental conditions in the marine milieu. These organisms have evolved various mechanisms for growth in the marine environment, especially against salinity gradients. This review highlights the response of marine fungi, fungal-like organisms and terrestrial fungi (for comparison) towards salinity variations in terms of their growth, spore germination, sporulation, physiology, and genetic adaptability. Marine, freshwater and terrestrial fungi and fungal-like organisms vary greatly in their response to salinity. Generally, terrestrial and freshwater fungi grow, germinate and sporulate better at lower salinities, while marine fungi do so over a wide range of salinities. Zoosporic fungal-like organisms are more sensitive to salinity than true fungi, especially Ascomycota and Basidiomycota. Labyrinthulomycota and marine Oomycota are more salinity tolerant than saprolegniaceous organisms in terms of growth and reproduction. Wide adaptability to saline conditions in marine or marine-related habitats requires mechanisms for maintaining accumulation of ions in the vacuoles, the exclusion of high levels of sodium chloride, the maintenance of turgor in the mycelium, optimal growth at alkaline pH, a broad temperature growth range from polar to tropical waters, and growth at depths and often under anoxic conditions, and these properties may allow marine fungi to positively respond to the challenges that climate change will bring. Other related topics will also be discussed in this article, such as the effect of salinity on secondary metabolite production by marine fungi, their evolution in the sea, and marine endophytes.

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Seasonal carbonate system vis-a-vis pH and salinity in selected tropical estuaries: implications on polychaete diversity and composition towards predicting ecological health

Highlights

  • The role of salinity-pH gradient coupled with carbonate species on the polychaete community distribution was studied.
  • Salinity-pH was positively correlated with carbonate and DOC.
  • pCO2 was positively correlated with POC, DIC and CO2.
  • High levels of carbonate species and low pH have a greater impact on polychaete diversity and richness.

Abstract

Salinity and pH play a fundamental role in structuring spatial patterns of physical properties, biota, and biogeochemical processes in the estuarine ecosystem. In this study, the influence of salinity-pH gradient and carbonate system on polychaete diversity in Ennore, Uppanar, Vellar, and Kaduvaiyar estuaries was investigated. Water and sediment samples were collected from September 2017 to August 2018. Univariate and multivariate statistical analyses were employed to define ecological status. Temperature, Salinity, pH, and partial pressure of carbon-di-oxide varied between 21 and 30°C; 29 and 39 ppt; 7.4 and 8.3; and 89.216 and 1702.558 µatm, respectively. PCA and CCA results revealed that DO, chlorophyll, carbonate species, and sediment TOC have a higher influence on polychaete community structure. Forty-two species such as Ancistrosyllis parva, Cossura coasta, Eunice pennata, Euclymene annandalei, Lumbrineris albidentata, Capitella capitata, Prionospio cirrifera, P. pinnata, P. cirrobranchiata, and Notomastus sp. were found dominantly in all estuaries. Shannon index values ranged between 1.619 (UE-1) and 3.376 (VE-2). Based on these findings, high levels of carbonate species and low pH have a greater impact on polychaete diversity and richness values. The results of the AMBI Index revealed that stations UE-1, UE-2, UE-3 in Uppanar, EC-1, EC-2 in Ennore indicate “moderately disturbed”, while other stations are under the “slightly disturbed” category. This trend was quite evident in M-AMBI as well.

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Can heat shock protein 70 (HSP70) serve as biomarkers in Antarctica for future ocean acidification, warming and salinity stress?

The Antarctic Peninsula is one of the fastest-warming places on Earth. Elevated sea water temperatures cause glacier and sea ice melting. When icebergs melt into the ocean, it “freshens” the saltwater around them, reducing its salinity. The oceans absorb excess anthropogenic carbon dioxide (CO2) causing decline in ocean pH, a process known as ocean acidification. Many marine organisms are specifically affected by ocean warming, freshening and acidification. Due to the sensitivity of Antarctica to global warming, using biomarkers is the best way for scientists to predict more accurately future climate change and provide useful information or ecological risk assessments. The 70-kilodalton (kDa) heat shock protein (HSP70) chaperones have been used as biomarkers of stress in temperate and tropical environments. The induction of the HSP70 genes (Hsp70) that alter intracellular proteins in living organisms is a signal triggered by environmental temperature changes. Induction of Hsp70 has been observed both in eukaryotes and in prokaryotes as response to environmental stressors including increased and decreased temperature, salinity, pH and the combined effects of changes in temperature, acidification and salinity stress. Generally, HSP70s play critical roles in numerous complex processes of metabolism; their synthesis can usually be increased or decreased during stressful conditions. However, there is a question as to whether HSP70s may serve as excellent biomarkers in the Antarctic considering the long residence time of Antarctic organisms in a cold polar environment which appears to have greatly modified the response of heat responding transcriptional systems. This review provides insight into the vital roles of HSP70 that make them ideal candidates as biomarkers for identifying resistance and resilience in response to abiotic stressors associated with climate change, which are the effects of ocean warming, freshening and acidification in Antarctic organisms.

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How does ocean acidification affect the early life history of Zostera marina? A series of experiments find parental carryover can benefit viability or germination

Elevated partial pressure of carbon dioxide (pCO2) as a concomitant of global climate change may facilitate the establishment of future seagrass meadows and subsequently its benefit could be incorporated into techniques to increase restoration success. In five manipulative experiments, we determined how increased CO2 affects the maturation of flowers, and the development of seeds and seedlings for the foundation species Zostera marina. Experiments tested the development from both seeds collected from non-treated flowering shoots (direct) and seeds harvested from flowering shoots after CO2 exposure (parental carryover). Flowering shoots were collected along the western coast of Sweden near the island of Skafto. The seeds produced were used in experiments conducted at Kristineberg, Sweden and Dauphin Island, AL, United States. Experiments varied in temperature (16, 18°C) and salinity (19, 33 ppt), as well as duration and magnitude of elevated CO2 exposure. Flowering maturation, spathe number, seed production, and indicators of seed quality did not appear to be affected by 39–69 days of exposure to CO2 conditions outside of natural variability (pCO2 = 1547.2 ± 267.60 μatm; pHT = 7.53 ± 0.07). Yet, seeds produced from these flowers showed twofold greater germination success. In another experiment, flowering shoots were exposed to an extreme CO2 condition (pCO2 = 5950.7 ± 1,849.82 μatm; pHT = 6.96 ± 0.15). In this case, flowers generated seeds that demonstrated a fivefold increase in an indicator for seed viability (sinking velocity). In the latter experiment, however, germination appeared unaffected. Direct CO2 effects on germination and seedling production were not observed. Our results provide evidence of a parental CO2 effect that can benefit germination or seed viability, but early benefits may not lead to bed establishment if other environmental conditions are not well suited for seedling development. Outcomes have implications for restoration; CO2 can be supplied to flowering shoot holding tanks to bolster success when the purpose is to redistribute seeds to locations where beds are extant and water quality is adequate.

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Chapter five – Interactive effects of ocean acidification and other environmental factors on marine organisms

In recent decades, the marine environment has been seriously affected by various anthropogenic activities (e.g., deforestation, fossil fuel combustion, and disordered discharges of pollutants). As a consequence, a range of changes in seawater environmental factors have taken place in oceans around the world, including increased temperature, reduced pH and dissolved oxygen, salinity fluctuation, and many other anomalous alterations in environmental factors, and these changes have aroused concerns from scientists. It has been widely reported that these changes in environmental factors would impact marine organisms severely. Meanwhile, it is worth noting that the environmental stressors mentioned above are rarely occurring independently in nature. Thus marine organisms are usually threatened by many different environmental stressors, and there would be complex and unpredicted interactions among the stressors. Generally, the interactive effects varied among additive (total effect equal to the sum of individual effects), synergistic (total effect greater than the sum of individual effects), or antagonistic (total effect less than the sum of individual effects), depending on the species and life stages of the studied organism, and the nature of the stressors themselves. It is necessary to figure out the interactive effects among various environmental stressors on specific marine organisms to accurately predict their physiological states and population dynamics under future climate scenarios. Therefore in this chapter, we summarize the related experiments in the last 20 years to discuss the interactive effects of ocean acidification (OA) combined with four other typical environmental stressors, namely ocean warming, hypoxia, salinity fluctuation, and heavy metal pollution, on marine organisms according to previously published studies. The authors hope that the contents of this chapter provide some basic information about the interactive effects of OA and the other four environmental factors for readers who are interested in this subject area.

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Climate change increases susceptibility to grazers in a foundation seaweed

Climate change leads to multiple effects caused by simultaneous shifts in several physical factors which will interact with species and ecosystems in complex ways. In marine systems the effects of climate change include altered salinity, increased temperature, and elevated pCO2 which are currently affecting and will continue to affect marine species and ecosystems. Seaweeds are primary producers and foundation species in coastal ecosystems, which are particularly vulnerable to climate change. The brown seaweed Fucus vesiculosus (bladderwrack) is an important foundation species in nearshore ecosystems throughout its natural range in the North Atlantic Ocean and the Baltic Sea. This study investigates how individual and interactive effects of temperature, salinity, and pCO2 affect F. vesiculosus, using a fully crossed experimental design. We assessed the effects on F. vesiculosus in terms of growth, biochemical composition (phlorotannin content, C:N ratio, and ∂13C), and susceptibility to the specialized grazer Littorina obtusata. We observed that elevated pCO2 had a positive effect on seaweed growth in ambient temperature, but not in elevated temperature, while growth increased in low salinity at ambient but not high temperature, regardless of pCO2-level. In parallel to the statistically significant, but relatively small, positive effects on F. vesiculosus growth, we found that the seaweeds became much more susceptible to grazing in elevated pCO2 and reduced salinity, regardless of temperature. Furthermore, the ability of the seaweeds to induce chemical defenses (phlorotannins) was strongly reduced by all the climate stressors. Seaweeds exposed to ambient conditions more than doubled their phlorotannin content in the presence of grazers, while seaweeds exposed to any single or combined stress conditions showed only minor increases in phlorotannin content, or none at all. Despite the minor positive effects on seaweed growth, the results of this study imply that climate change can strongly affect the ability of fucoid seaweeds to induce chemical defenses and increase their susceptibility to grazers. This will likely lead to widespread consequences under future climate conditions, considering the important role of F. vesiculosus and other fucoids in many coastal ecosystems.

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Primary, secondary, and tertiary stress responses of juvenile seahorse Hippocampus reidi exposed to acute acid stress in brackish and seawater

Highlights

• Activity of antioxidant enzymes was harmed in seahorse juveniles exposed to acidic environment in brackish water.

• Lower tolerance for acidification in brackish water triggered lipid peroxidation in seahorse juveniles.

• Seahorse juvenile survival was not influenced by pH neither in brackish nor in sea water.

Abstract

Seahorse Hippocampus reidi is a vulnerable species, inhabiting estuarine and coastal waters. The safety of acidic environments for fish has been considered in terms of ocean acidification in nature and decreasing pH in intensive aquaculture systems. This study aimed to investigate the effects of acute exposition (96 h) of juvenile seahorses to different pH (5, 6, 7, and 8) in brackish (BW – salinity 11) or seawater (SW – salinity 33). For that, we studied the responses of cortisol, oxidative stress, and survival, thus covering primary, secondary, and tertiary stress responses. In SW, cortisol levels were not altered for fish maintained at pH 5 and 8. However, in BW, cortisol was higher for fish kept at pH 5. Regarding secondary stress responses, only GST activity increased with acidification in SW. However, acidification in BW caused biochemical alterations at enzymatic level (SOD, GST, GPx) and glutathione metabolism, accompanied by reduction of antioxidant capacity (TEAC) and increased lipid peroxidation (TBARS). Survival was always above 90% and it did not differ significantly among pH levels. Our results suggest that H. reidi juveniles are more vulnerable to acidic exposure in BW than in SW.

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Effects of salinity, pH and alkalinity on hatching rate of fertilized eggs of Penaeus monodon

The fertilized eggs of “Nanhai 2” Penaeus monodon bred by our research group were incubated at the same temperature (30°C), different salinity (20, 25, 30, 35, 40), different pH (7.0, 7.5, 8.0, 8.5, 9.0) and different alkalinity (2.0 mmol/L, 2.5 mmol/L, 3.0 mmol/L, 3.5 mmol/L, 4.0 mmol/L) to explore the effects of salinity, pH and alkalinity on hatching rate of fertilized eggs of P. monodon. The results showed that the hatching rate of fertilization rate of P. monodon was closely related to salinity, and the best hatching rate was obtained when the seawater salinity was 30 with the average hatching rate was 82.60%. The hatching rate was very low when the salinity was as low as 20 or as high as 40, which was significantly lower than that of other treatments (P<0.05). The hatching effect of the fertilized eggs of P. monodon was closely related to the pH value of seawater, and the slightly alkaline seawater was conducive to the normal development of the fertilized eggs. Among them, the hatching effect of the seawater pH value of 8.0 was the best, and the average hatching rate of the fertilized eggs was 80.62%. Too low or too high pH value of the seawater was not conducive to the development of the embryo, and the hatching rate of the fertilized eggs decreased in varying degrees. There was no significant correlation between the hatching effect of fertilized eggs and the change of seawater alkalinity. The average hatching rate of fertilized eggs ranged from 78.65% to 83.12% in the alkalinity range of 2.0-4.0 mmol/L

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Long-term environmental tolerance of the non-indigenous Pacific oyster to expected contemporary climate change conditions

Highlights

  • Long-term effects of climate change on non-indigenous species are rarely studied
  • Pacific oysters were exposed to warming, ocean acidification and reduced salinity
  • Warming and ocean acidification predicted for the year 2100 did not affect fitness
  • Low salinity reduced clearance rates and increased oxygen consumption rates
  • Long-term observations highlighted potential seasonal trends in physiological rates

Abstract

The current global redistribution of biota is often attributed to two main drivers: contemporary climate change (CCC) and non-indigenous species (NIS). Despite evidence of synergetic effects, however, studies assessing long-term effects of CCC conditions on NIS fitness remain rare. We examined the interactive effects of warming, ocean acidification and reduced salinity on the globally distributed marine NIS Magallana gigas(Pacific oyster) over a ten-month period. Growth, clearance and oxygen consumption rates were measured monthly to assess individual fitness. Lower salinity had a significant, permanent effect on M. gigas, reducing and increasing clearance and oxygen consumption rates, respectively. Neither predicted increases in seawater temperature nor reduced pH had a long-term physiological effect, indicating conditions predicted for 2100 will not affect adult physiology and survival. These results suggest that M. gigas will remain a globally successful NIS and predicted CCC will continue to facilitate their competitive dominance in the near future.

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Decoupling salinity and carbonate chemistry: low calcium ion concentration rather than salinity limits calcification in Baltic Sea mussels

The Baltic Sea has a salinity gradient decreasing from fully marine (> 25) in the West to below 7 in the Central Baltic Proper. Reef forming mytilid mussels exhibit decreasing growth when salinity < 11, however the mechanisms underlying reduced calcification rates in dilute seawater are not fully understood. In fact, both [HCO3] and [Ca2+] also decrease with salinity, challenging calcifying organisms through CaCO3 undersaturation (Ω ≤ 1) and unfavourable ratios of calcification substrate (Ca2+ and HCO3) to inhibitor (H+). In this study we assessed the impact of isolated individual factors (salinity, [Ca2+], [HCO3] and pH) on calcification and growth of mytilid mussel populations along the Baltic salinity gradient. Laboratory experiments rearing juvenile Baltic Mytilus at a range of salinities (6, 11 and 16), HCO3 concentrations (300–2100 µmol kg−1) and Ca2+ concentrations (0.5–4 mmol kg−1) were coupled with field monitoring in three Baltic mussel reefs. Results reveal that as individual factors, low [HCO3], pH and salinity cannot explain low calcification rates in the Baltic Sea. Calcification rates are impeded when Ωaragonite ≤ 1 or the substrate inhibitor ratio ≤ 0.7, primarily due to [Ca2+] limitation which corresponds to a salinity of ca. 11. Increased food availability may be able to mask these negative impacts, but not when seawater conditions are permanently adverse, as observed in two Baltic reefs at salinities < 11. Future climatic models predict rapid desalination of the southwest and Central Baltic and potentially a reduction in [Ca2+] which may lead to a westward distribution shift of marine calcifiers. It is therefore vital to understand the mechanisms by which the ionic composition of seawater impacts bivalve calcification for better predicting the future of benthic Baltic ecosystems.

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

Highlights

  • Glacial retreat induced by global warming can decrease salinity and pH of the Antarctic ocean.
  • The Antarctic amphipod Gondogeneia antarctica was exposed to low salinity (27 psu) and low pH (7.6) conditions.
  • Low salinity increased cannibalism and induced adjusted swimming.
  • Low pH increased mortality, impaired food detection and reduced daytime shelter use.
  • Ocean freshening and acidification 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 psu) 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.

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Effects of low pH and low salinity induced by meltwater inflow on the behavior and physical condition of the Antarctic limpet, Nacella concinna

Seawater acidification and freshening in the intertidal zone of Marian Cove, Antarctica, which occurs by the freshwater inflow from snow fields and glaciers, could affect the physiology and behavior of intertidal marine organisms. In this study, we exposed Antarctic limpets, Nacella concinna, to two different pH (8.00 and 7.55) and salinity (34.0 and 27.0 psu) levels and measured their righting ability after being flipped over, mortality, condition factor, and shell dissolution. During the 35-day exposure, there was no significant difference in behavior and mortality between different treatments. However, the condition factor was negatively affected by low salinity. Both low pH and low salinity negatively influenced shell formation by decreasing the aragonite saturation state (Ωarg) and enhancing shell dissolution. Our results suggest that, though limpets can tolerate short-term low pH and salinity conditions, intrusions of meltwater accompanied by the glacial retreat may act as a serious threat to the population of N. concinna.

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Contrasting responses to salinity and future ocean acidification in arctic populations of the amphipod Gammarus setosus

Highlights

  • Climate change is leading to changes in salinity and pCO2 in arctic/sub-arctic coastal ecosystems.

  • We examined Gammarus setosus at 3 sites along a salinity gradient in the field and laboratory.

  • Reduced salinity had more of an effect than elevated pCO2 by reducing energy budgets.

  • Lower salinities increased ion transporting capacities in the laboratory but not in the field.

  • G. setosus at lower salinity sites have lower energy budgets suggesting impacts on performance.

Abstract

Climate change is leading to alterations in salinity and carbonate chemistry in arctic/sub-arctic marine ecosystems. We examined three nominal populations of the circumpolar arctic/subarctic amphipod, Gammarus setosus, along a salinity gradient in the Kongsfjorden-/Krossfjorden area of Svalbard. Field and laboratory experiments assessed physiological (haemolymph osmolality and gill Na+/K+-ATPase activity, NKA) and energetic responses (metabolic rates, MO2, and Cellular Energy Allocation, CEA). In the field, all populations had similar osmregulatory capacities and MO2, but lower-salinity populations had lower CEA. Reduced salinity (S = 23) and elevated pCO2 (∼1000 μatm) in the laboratory for one month increased gill NKA activities and reduced CEA in all populations, but increased MO2 in the higher-salinity population. Elevated pCO2 did not interact with salinity and had no effect on NKA activities or CEA, but reduced MO2 in all populations. Reduced CEA in lower-rather than higher-salinity populations may have longer term effects on other energy demanding processes (growth and reproduction).

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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.

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Temperature and salinity, not acidification, predict near-future larval growth and larval habitat suitability of Olympia oysters in the Salish Sea

Most invertebrates in the ocean begin their lives with planktonic larval phases that are critical for dispersal and distribution of these species. Larvae are particularly vulnerable to environmental change, so understanding interactive effects of environmental stressors on larval life is essential in predicting population persistence and vulnerability of species. Here, we use a novel experimental approach to rear larvae under interacting gradients of temperature, salinity, and ocean acidification, then model growth rate and duration of Olympia oyster larvae and predict the suitability of habitats for larval survival. We find that temperature and salinity are closely linked to larval growth and larval habitat suitability, but larvae are tolerant to acidification at this scale. We discover that present conditions in the Salish Sea are actually suboptimal for Olympia oyster larvae from populations in the region, and that larvae from these populations might actually benefit from some degree of global ocean change. Our models predict a vast decrease in mean pelagic larval duration by the year 2095, which has the potential to alter population dynamics for this species in future oceans. Additionally, we find that larval tolerance can explain large-scale biogeographic patterns for this species across its range.

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Effects of salinity and pH of seawater on the reproduction of the sea urchin Paracentrotus lividus

Fertilization and early development are usually the most vulnerable stages in the life of marine animals, and the biological processes during this period are highly sensitive to the environment. In nature, sea urchin gametes are shed in seawater, where they undergo external fertilization and embryonic development. In a laboratory, it is possible to follow the exact morphological and biochemical changes taking place in the fertilized eggs and the developing embryos. Thus, observation of successful fertilization and the subsequent embryonic development of sea urchin eggs can be used as a convenient biosensor to assess the quality of the marine environment. In this paper, we have examined how salinity and pH changes affect the normal fertilization process and the following development of Paracentrotus lividus. The results of our studies using confocal microscopy, scanning and transmission electron microscopy, and time-lapse Ca2+ image recording indicated that both dilution and acidification of seawater have subtle but detrimental effects on many aspects of the fertilization process. They include Ca2+ signaling and coordinated actin cytoskeletal changes, leading to a significantly reduced rate of successful fertilization and, eventually, to abnormal or delayed embryonic development.

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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.

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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’


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