The effect of seasonal temperature variation on behaviour and metabolism in the freshwater mussel (Unio tumidus)

Temperature plays a critical role in determining the biology of ectotherms. Many animals have evolved mechanisms that allow them to compensate biological rates, i.e. adjust biological rates to overcome thermodynamic effects. For low energy-organisms, such as bivalves, the costs of thermal compensation may be greater than the benefits, and thus prohibitive. To examine this, two experiments were designed to explore thermal compensation in Unio tumidus. Experiment 1 examined seasonal changes in behaviour in U. tumidus throughout a year. Temperature had a clear effect on burrowing rate with no evidence of compensation. Valve closure duration and frequency were also strongly affected by seasonal temperature change, but there was slight evidence of partial compensation. Experiment 2 examined oxygen consumption during burrowing, immediately following valve opening and at rest in summer (24 °C), autumn (14 °C), winter (4 °C), and spring (14 °C) acclimatized U. tumidus. Again, there was little evidence of burrowing rate compensation, but some evidence of partial compensation of valve closure duration and frequency. None of the oxygen compensation rates showed any evidence of thermal compensation. Thus, in general, there was only very limited evidence of thermal compensation of behaviour and no evidence of thermal compensation of oxygen compensation rates. Based upon this evidence, we argue that there is no evolutionary pressure for these bivalves to compensate these biological rates. Any pressure may be to maintain or even lower oxygen consumption as their only defence against predation is to close their valves and wait. An increase in oxygen consumption will be detrimental in this regard so the cost of thermal compensation may outweigh the benefits.

Photochemical responses of the diatom Skeletonema costatum grown under elevated CO2 concentrations to short-term changes in pH

Variability in pH is a common occurrence in many aquatic environments, due to physical, chemical and biological processes. In coastal waters, lagoons, estuaries and inland waters, pH can change very rapidly (within seconds or hours) in addition to daily and seasonal changes. At the same time, progressive ocean acidification caused by anthropogenic CO2 emissions is superimposed on these spatial and temporal pH changes. Photosynthetic organisms are therefore unavoidably subject to significant pH variations at the cell surface. Whether this will affect their response to long-term ocean acidification is still unknown, nor is it known whether the short-term sensitivity to pH change is affected by the pCO2 to which the cells are acclimated. We posed the latter open question as our experimental hypothesis: Does acclimation to seawater acidification affect the response of phytoplankton to acute pH variations? The diatom Skeletonema costatum, commonly found in coastal and estuarine waters where short-term acute changes in pH frequently occur, was selected to test the hypothesis. Diatoms were grown at both 390 (pH 8.2, low CO2; LC) and 1000 (pH 7.9, high CO2; HC) µatm CO2 for at least 20 generations, and photosynthetic responses to short-term and acute changes in pH (between 8.2 and 7.6) were investigated. The effective quantum yield of LC-grown cells decreased by ca. 70% only when exposed to pH 7.6; this was not observed when exposed to pH 7.9 or 8.2. HC-grown cells did not show significant responses in any pH treatment. Non-photochemical quenching showed opposite trends. In general, our results indicate that while LC-grown cells are rather sensitive to acidification, HC-grown cells are relatively unresponsive in terms of photochemical performance.

Circulation, eddies, oxygen and nutrient changes in the eastern tropical South Pacific Ocean

A large, subsurface oxygen deficiency zone is located in the eastern tropical South Pacific Ocean (ETSP). The large-scale circulation in the eastern equatorial Pacific and off Peru in November/December 2012 shows the influence of the equatorial current system, the eastern boundary currents, and the northern reaches of the subtropical gyre. In November 2012 the Equatorial Undercurrent is centered at 250 m depth, deeper than in earlier observations. In December 2012 the equatorial water is transported southeastward near the shelf in the Peru-Chile Undercurrent with a mean transport of 1.6 Sv. In the oxygen minimum zone (OMZ) the flow is overlaid with strong eddy activity on the poleward side of the OMZ. Floats with parking depth at 400 m show fast westward flow in the mid-depth equatorial channel and sluggish flow in the OMZ. Floats with oxygen sensors clearly show the passage of eddies with oxygen anomalies. The long-term float observations in the upper ocean lead to a net community production estimate at about 18° S of up to 16.7 mmol C m?3 yr1 extrapolated to an annual rate and 7.7 mmol C m?3 yr?1 for the time period below the mixed layer. Oxygen differences between repeated ship sections are influenced by the Interdecadal Pacific Oscillation, by the phase of El Niño, by seasonal changes, and by eddies and hence have to be interpreted with care. At and south of the equator the decrease in oxygen in the upper ocean since 1976 is related to an increase in nitrate, phosphate, and in part in silicate.

Intra-annual patterns of tracheid size in the Mediterranean tree Juniperus thurifera as an indicator of seasonal water stress

Because climate can affect xylem cell anatomy, series of intra-annual cell anatomical features have the potential to retrospectively supply seasonal climatic information. In this study, we explored the ability to extract information about water stress conditions from tracheid features of the Mediterranean conifer Juniperus thurifera L. Tracheidograms of four climatic years from two drought-sensitive sites in Spain were compared to evaluate whether it is possible to link intra-annual cell size patterns to seasonal climatic conditions. Results indicated site-specific anatomical adjustment such as smaller and thicker tracheids at the dryer site but also showed a strong climatic imprint on the intra-annual pattern of tracheid size. Site differences in cell size reflected expected structural adjustments against cavitation failures. Differences between intra-annual patterns, however, indicated a response to seasonal changes in water availability whereby cells formed under drought conditions were smaller and thicker, and vice versa. This relationship was more manifest and stable at the dryer site

Diel and seasonal variation in the use of a nearshore sandflat by a ray community in a near pristine system

Knowledge of movements and habitat use is necessary to assess a species’ ecological role and is especially important for mesopredators because they provide the link between upper and lower trophic levels. Using acoustic telemetry, we examined coarse-scale diel and seasonal movements of elasmobranch mesopredators on a shallow sandflat in Shark Bay, Western Australia. Giant shovelnose rays (Glaucostegus typus) and reticulate whiprays (Himantura uarnak) were most often detected in nearshore microhabitats and were regularly detected throughout the day and year, although reticulate whiprays tended to frequent the monitored array over longer periods. Pink whiprays (H. fai) and cowtail stingrays (Pastinachus atrus) were also detected throughout the day, but were far less frequently detected. Overall, there was no apparent spatial or temporal partitioning of the sandflats, but residency to the area varied between species. In addition, ray presence throughout the year suggests that previously observed differences in seasonal abundance are likely because of seasonal changes in habitat use rather than large-scale migrations. Continuous use of the sandflats and limited movements within this ray community suggests that rays have the potential to be a structuring force on this system and that focusing on nearshore habitats is important for managing subtropical ray populations.

Progressive changes in the Western English Channel foster a reorganization in the plankton food web

Growing evidence has shown a profound modification of plankton communities of the North East Atlantic and adjacent seas over the past decades. This drastic change has been attributed to a modification of the environmental conditions that regulate the dynamics and the spatial distribution of ectothermic species in the ocean. Recently, several studies have highlighted modifications of the regional climate station L4 (50° 15.00′N, 4° 13.02′W) in the Western English Channel. We here focus on the modification of the plankton community by studying the long-term, annual and seasonal changes of five zooplankton groups and eight copepod genera. We detail the main composition and the phenology of the plankton communities during four climatic periods identified at the L4 station: 1988–1994, 1995–2000, 2001–2007 and 2008–2012. Our results show that long-term environmental changes underlined by Molinero et al. (2013) drive a profound restructuration of the plankton community modifying the phenology and the dominance of key planktonic groups including fish larvae. Consequently, the slow but deep modifications detected in the plankton community highlight a climate driven ecosystem shift in the Western English Channel.

Progressive changes in the Western English Channel foster a reorganization in the plankton food web

Growing evidence has shown a profound modification of plankton communities of the North East Atlantic and adjacent seas over the past decades. This drastic change has been attributed to a modification of the environmental conditions that regulate the dynamics and the spatial distribution of ectothermic species in the ocean. Recently, several studies have highlighted modifications of the regional climate station L4 (50° 15.00′N, 4° 13.02′W) in the Western English Channel. We here focus on the modification of the plankton community by studying the long-term, annual and seasonal changes of five zooplankton groups and eight copepod genera. We detail the main composition and the phenology of the plankton communities during four climatic periods identified at the L4 station: 1988–1994, 1995–2000, 2001–2007 and 2008–2012. Our results show that long-term environmental changes underlined by Molinero et al. (2013) drive a profound restructuration of the plankton community modifying the phenology and the dominance of key planktonic groups including fish larvae. Consequently, the slow but deep modifications detected in the plankton community highlight a climate driven ecosystem shift in the Western English Channel.

Seasonal variation of acetylcholinesterase, catalase, glutathione s transferase in different size of Pinctada radiata and metal pollution (Pb, Cd, Ni) in Persian Gulf

There are various tools for monitoring the concentration of pollutants on aquatic ecosystems. Today these studies are based on biological monitoring and biomarkers. The aim of this study was to measure the concentration of the acetylcholinesterase (AChE), glutathione S-transferase and catalase as biomarkers of heavy metal contamination in pearl oyster Pinctada radiata and their mechanism in aquatic ecosystems. Heavy metals lead, cadmium and nickel were measured in soft tissue and studied stations in four seasons. Samples were collected seasonally in Lavan stations, Hendurabi and Nakhilo (in the northern Persian Gulf) from spring 2013 to winter of that year by scuba diving. Pearl oysters are divided according to their shells size; shells separated from soft tissues and were transferred to the laboratory for analysis of heavy metals and enzymes. Moopam standard method for were used for measuring the concentration of heavy metals and for analyzing tissue concentrations of glutathione S-transferase in Clam the method recommended by Habig et al in 1974 were used. For measuring acetylcholinesterase Ellman method were used. Catalase contamination in pearl oyster in the supernatant obtained from the study based on the method homogeate soft tissue of mussels (Abei, 1974) was evaluated. The results showed that the concentration of lead has significant difference in sediments station, the concentration of lead in Lavan is significantly higher than the other two stations, This could be due to the movement of tanker, boats and floating refueling and with a considerable amount of wastewater containing oil and Petroleum into the water, and also due to precipitation and industrial discharges the lead in the region is increasing, land-disposed sewage sludge, has large concentrations of lead. Compare the results of this study with standards related and other similar studies at the regional and international level showed that pollutant concentration of heavy metals in all cases significantly less than all the standards and guide values associated. And also compared to other world research results have been far less than others, Being Less of the conclusion given in this research according that nickel is one of the indicators of oil pollution in the study area and emissions have been relatively low of oil. The concentration of acetylcholinesterase at several stations, in large and small sizes and in the seasons had no significant difference. Variations of catalase, and glutathione S-transferase were almost similar to each other and parameters, station and seasons were significantly different in the concentrations of these enzymes. The effects and interaction between various parameters indicate that following parameters has impact on the concentration of catalase and glutathione S-transferase. Stations; Seasonal changes in antioxidant enzymes related to (assuming a constant in salinity and oxygen) to age, reproductive cycle, availability of food and water temperature. With increasing temperature at warm season, antioxidant enzymes were increase, with increasing temperature and abundance of food in the environment the amount of antioxidant enzymes may increase. The presence of the enzyme concentration may indicate that the higher levels of the enzyme to eliminate ROS activities to be any healthier situation. At the time of gonads maturation and spawning season catalase activity increases. This study also indicates that catalase was significantly higher in the warm season. Due to low pollutants of heavy metals in the study area, a lower level of contaminants were observed in shellfish tissue incidents of international standards and strong correlation between the amount of heavy metal contamination in pearl oyster tissue and enzymes was not observed. Therefore, we can say that the pearl oyster remains in a healthy condition and the amount of enzyme is normal.

Amazon forest structure generates diurnal and seasonal variability in light utilization.

The complex three-dimensional (3-D) structure of tropical forests generates a diversity of light environments for canopy and understory trees. Understanding diurnal and seasonal changes in light availability is critical for interpreting measurements of net ecosystem exchange and improving ecosystem models. Here, we used the Discrete Anisotropic Radiative Transfer (DART) model to simulate leaf absorption of photosynthetically active radiation (lAPAR) for an Amazon forest. The 3-D model scene was developed from airborne lidar data, and local measurements of leaf reflectance, aerosols, and PAR were used to model lAPAR under direct and diffuse illumination conditions. Simulated lAPAR under clear-sky and cloudy conditions was corrected for light saturation effects to estimate light utilization, the fraction of lAPAR available for photosynthesis. Although the fraction of incoming PAR absorbed by leaves was consistent throughout the year (0.80?0.82), light utilization varied seasonally (0.67?0.74), with minimum values during the Amazon dry season. Shadowing and light saturation effects moderated potential gains in forest productivity from increasing PAR during dry-season months when the diffuse fraction from clouds and aerosols was low. Comparisons between DART and other models highlighted the role of 3-D forest structure to account for seasonal changes in light utilization. Our findings highlight how directional illumination and forest 3-D structure combine to influence diurnal and seasonal variability in light utilization, independent of further changes in leaf area, leaf age, or environmental controls on canopy photosynthesis. Changing illumination geometry constitutes an alternative biophysical explanation for observed seasonality in Amazon forest productivity without changes in canopy phenology.

Variabilidade espacial e sazonal da concentração de elementos-traço em sedimentos do sistema estuarino de Santos-Cubatão (SP)

Multi-element analyses of sediment samples from the Santos-Cubatão Estuarine System were carried out to investigate the spatial and seasonal variability of trace-element concentrations. The study area contains a rich mangrove ecosystem that is a habitat for tens of thousands of resident and migratory birds, some of them endangered globally. Enrichments of metals in fine-grained surface sediments are, in decreasing order, Hg, Mn, La, Ca, Sr, Cd, Zn, Pb, Ba, Cu, Cr, Fe, Nb, Y, Ni and Ga, relative to pre-industrial background levels. The maximum enrichment ranged from 49 (Hg) to 3.1 (Ga). Mercury concentrations were greater in the Cubatão river than in other sites, while the other elements showed greater concentrations in the Morrão river. Concentrations of Mn were significantly greater in winter and autumn than in summer and spring. However, other elements (e.g. Cd and Pb) showed the opposite, with greater concentrations in summer and spring. This study suggests that seasonal changes in physical and chemical conditions may affect the degree of sediment enrichment and therefore make the assessment of contamination difficult. Consequently, these processes need to be considered when assessing water quality and the potential contamination of biota.

Urban air pollution and chronic obstructive pulmonary disease-related emergency department visits

Background: Patients with chronic obstructive pulmonary disease (COPD) can have recurrent disease exacerbations triggered by several factors, including air pollution. Visits to the emergency respiratory department can be a direct result of short-term exposure to air pollution. The aim of this study was to investigate the relationship between the daily number of COPD emergency department visits and the daily environmental air concentrations of PM(10), SO(2), NO(2), CO and O(3) in the City of Sao Paulo, Brazil. Methods: The sample data were collected between 2001 and 2003 and are categorised by gender and age. Generalised linear Poisson regression models were adopted to control for both short-and long-term seasonal changes as well as for temperature and relative humidity. The non-linear dependencies were controlled using a natural cubic spline function. Third-degree polynomial distributed lag models were adopted to estimate both lag structures and the cumulative effects of air pollutants. Results: PM(10) and SO(2) readings showed both acute and lagged effects on COPD emergency department visits. Interquartile range increases in their concentration (28.3 mg/m(3) and 7.8 mg/m(3), respectively) were associated with a cumulative 6-day increase of 19% and 16% in COPD admissions, respectively. An effect on women was observed at lag 0, and among the elderly the lag period was noted to be longer. Increases in CO concentration showed impacts in the female and elderly groups. NO(2) and O(3) presented mild effects on the elderly and in women, respectively. Conclusion: These results indicate that air pollution affects health in a gender-and age-specific manner and should be considered a relevant risk factor that exacerbates COPD in urban environments.

Transport, storage and mobilization of nitrogen by trees and shrubs in the wet/dry tropics of northern Australia

Xylem sap from woody species in the wet/dry tropics of northern Australia was analyzed for N compounds. At the peak of the dry season, arginine was the main N compound in sap of most species of woodlands and deciduous monsoon forest. In the wet season, a marked change occurred with amides becoming the main sap N constituents of most species. Species from an evergreen monsoon forest, with a permanent water source, transported amides in the dry season. In the dry season, nitrate accounted for 7 and 12% of total xylem sap N in species of deciduous and evergreen monsoon forests, respectively In the wet season, the proportion of N present as nitrate increased to 22% in deciduous monsoon forest species. These results suggest that N is taken up and assimilated mainly in the wet season and that this newly assimilated N is mostly transported as amide-N (woodland species, monsoon forest species) and nitrate (monsoon forest species). Arginine is the form in which stored N is remobilized and transported by woodland and deciduous monsoon forest species in the dry season. Several proteins, which may represent bark storage proteins, were detected in inner bark tissue from a range of trees in the dry season, indicating that, although N uptake appears to be limited in the dry season, the many tree and shrub species that produce flowers, fruit or leaves in the dry season use stored N to support growth. Nitrogen characteristics of the studied species are discussed in relation to the tropical environment.

Reproduction in the squirrel glider, Petaurus norfolcensis (Petauridae) in south-east Queensland

Reproduction was studied across a three-year period in two south-east Queensland populations of the squirrel glider, Petaurus norfolcensis, by measuring morphological (body weight, scrotal diameter, cutaneous scent-gland activity, condition index) and physiological (plasma steroid levels) variables. Reproduction showed a seasonal pattern, with peak numbers of pouch young recorded in late autumn and winter. Declines in oestrogen concentrations outside the breeding period indicate that females are anoestrous in the summer months. Most (83%) reproductive females captured during the study were 2-3 years old, but all individuals over one year of age were found to have bred. Average litter size was 1.73 +/- 0.01 (n = 23). Scrotal diameter and testosterone concentrations showed no significant seasonal variation. It is suggested that this is due to the presence of both socially dominant and subordinate males in the data set. Maximum testosterone concentrations did coincide with periods of mating. The condition index showed no relationship with reproductive variables, but it is likely that this results from the manner in which the index was generated.

Leaf water relations of Eucalyptus cloeziana and Eucalyptus argophloia in response to water deficit

Leaf water relations responses to limited water supply were determined in 7-month-old plants of a dry inland provenance of Eucalyptus argophloia Blakely and in a humid coastal provenance (Gympie) and a dry inland provenance (Hungry Hills) of Eucalyptus cloeziana F. Muell. Each provenance of E. cloeziana exhibited a lower relative water content at the turgor loss point, a lower apoplastic water content, a smaller ratio of dry mass to turgid mass and a lower bulk modulus of elasticity than the single provenance of E. argophloia. Osmotic potential at full turgor and water potential at the turgor loss point were significantly lower in E. argophloia and the inland provenance of E. cloeziana than in the coastal provenance of E. cloeziana. There was limited osmotic adjustment in response to soil drying in E. cloeziana, but not in E. argophloia. Between-species differences in water relations parameters were larger than those between the E. cloeziana provenances. Both E. cloeziana provenances maintained turgor under moderate water stress through a combination of osmotic and elastic adjustments. Eucalyptus argophloia had more rigid cell walls and reached lower water potentials with less reduction in relative water content than either of the E. cloeziana provenances, thereby enabling it to extract water from dryer soils.