Posts Tagged 'salinity'

Changes in temperature, pH, and salinity affect the sheltering responses of Caribbean spiny lobsters to chemosensory cues

Florida Bay is home to a network of shallow mud-banks which act as barriers to circulation creating small basins that are often subject to extremes in temperature and salinity. Florida bay is also important juvenile habitat for the Caribbean spiny lobster Panulirus argus. While our understanding of the effect of environmental changes on the survival, growth, and movement of spiny lobsters is growing, the effect on their chemosensory abilities has not yet been investigated. Lobsters rely heavily on chemical cues for many biological and ecological activities, and here we report on the effect of extreme environmental events in temperature (32 °C), salinity (45ppt), and pH (7.65 pH) on social behavior and sheltering preference in P. argus. Under normal conditions, chemical cues from conspecifics are used by spiny lobsters to identify suitable shelter and cues from stone crabs and diseased individuals are used to determine shelters to be avoided. In all altered conditions, lobsters lost the ability to aggregate with conspecifics and avoid stone crabs and diseased conspecifics. Thus, seasonal extreme events, and potentially future climate change conditions, alter the chemosensory-driven behavior of P. argus and may result in decreased survivorship due to impaired shelter selection or other behaviors.

Continue reading ‘Changes in temperature, pH, and salinity affect the sheltering responses of Caribbean spiny lobsters to chemosensory cues’

Hyposalinity tolerance inthecoccolithophorid Emiliania huxleyi under the influence of ocean acidification involves enhanced photosynthetic performance

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 effective photochemical efficiency under both LC or HC. Calcification rates were relatively insensitive to combined effects of salinity and OA treatment but were highest under 3 5‰ and HC conditions, with higher ratios of calcification to photosynthesis (C : P) in the cells grown under 35 ‰ compared with those grown at 25 ‰. In addition, elevated dissolved inorganic carbon (DIC) concentration at the salinity of 35 ‰ stimulated its calcification. 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 HC treatment enhanced PSII damage rate. Our results suggest Emiliania huxleyi can tolerate low salinity plus acidification conditions by up-regulating its photosynthetic performance together with a relatively insensitive calcification response, which may help it better adapt to future ocean global environmental changes, especially in the coastal areas of high latitudes.

Continue reading ‘Hyposalinity tolerance inthecoccolithophorid Emiliania huxleyi under the influence of ocean acidification involves enhanced photosynthetic performance’

Feeding plasticity more than metabolic rate drives the productivity of economically important filter feeders in response to elevated CO2 and reduced salinity

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.

Continue reading ‘Feeding plasticity more than metabolic rate drives the productivity of economically important filter feeders in response to elevated CO2 and reduced salinity’

Sensitivity to near-future CO2 conditions in marine crabs depends on their compensatory capacities for salinity change

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.

Continue reading ‘Sensitivity to near-future CO2 conditions in marine crabs depends on their compensatory capacities for salinity change’

Effects of ocean acidification on salinity tolerance and seawater growth of Atlantic salmon Salmo salar smolts

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.

Continue reading ‘Effects of ocean acidification on salinity tolerance and seawater growth of Atlantic salmon Salmo salar smolts’

Trophic functioning of macrobenthic fauna in a tropical acidified Bornean estuary (Southeast Asia)

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.

Continue reading ‘Trophic functioning of macrobenthic fauna in a tropical acidified Bornean estuary (Southeast Asia)’

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)

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.

Continue reading ‘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)’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,178,819 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book