Changes In Environmental Parameters Research Articles

Mowing influences community‐level variation in resource‐use strategies and flowering phenology along an ecological succession on Mediterranean road slopes

AbstractQuestionsHow do species composition, resource‐use strategy and flowering phenology change and relate to each other in road slope plant communities along an ecological succession after construction work? How does recurrent mowing influence resource‐use successional trajectory and flowering phenology in communities? Does intraspecific variation contribute to these community‐level functional responses?LocationRoad slopes in Mediterranean southern France.MethodsWe designed a chronosequence of 25 road slopes, each including both unmown and yearly mown parts. We analysed the influence of age and mowing on community‐level trait values (CWM) of LDMC, SLA, onset of flowering Date (OFD), end of flowering date (EFD) and flowering duration (FDur). We tested for contribution of intraspecific variation of traits to these functional variations. We also tested for relationship between changes in taxonomic composition, environmental parameters and functional responses.ResultsWe found slower successional variation of resource‐use strategies in communities undergoing recurrent mowing, compared to unmown vegetation. Onset of flowering was earlier in mown communities. End of flowering and flowering duration did not directly depend on successional stage or mowing but related to resource‐use strategies. Species turnover was an important driver of functional variation and the major components of plant taxonomic variation were primarily related to environmental and functional changes.ConclusionsOn road slopes, successional changes in functional and taxonomic composition were influenced by mowing, which did not totally prevent vegetation changes. Disturbance by mowing impacted resource‐use strategy and indirectly influenced flowering phenology by limiting plant investment into resource conservation in aerial parts. Community‐level relationship between resource‐use strategy and flowering phenology suggests a consistent trade‐off between vegetative growth and flowering phenology among plant species within communities. Our findings help to understand how recurrent disturbances can influence successional trajectories in mediterranean ecosystems.

Spatial variation in the phytoplankton standing stock and diversity in relation to the prevailing environmental conditions along the Saudi Arabian coast of the northern Red Sea

Variations in phytoplankton biomass and diversity in relation to the changing environmental parameters have been studied extensively during the summer season from three different regions (Al Wajh, Duba and Al Khoraeyba) on the northern Red Sea coast of Saudi Arabia. The temperature fluctuated between 25.2 and 31.5 °C with a salinity level between 39.58 and 40.16 PSU. The nutrients did not show any wide fluctuation between the regions and always remained, low which directly influenced the chlorophyll a (0.038–1.87 mg m−3). The higher phytoplankton densities were observed from stations A6 to A15 (average 4738 ± 2351 × 103 cells m−3) in Al Wajh due to the proliferation of diatom species (Hemiaulus hauckii, Proboscia alata and Thalassiothrix longissima). A total of 283 phytoplankton species was encountered from the whole area (129 diatoms, 152 dinoflagellates and 2 cyanophytes) of which 118 species were new to the Red Sea. Maximum species diversity was observed from Al Wajh (267) followed by Duba (113) and Al Khoraeyba (97). Of these species, 7 diatoms and 20 dinoflagellates have been previously reported to produce harmful algal blooms worldwide.Trichodesmium, which is a dominant diazotrophic genus in the Red Sea, was present at the majority of the stations.

Plant-phytopathogen interactions: bacterial responses to environmental and plant stimuli.

Plant pathogenic bacteria attack numerous agricultural crops, causing devastating effects on plant productivity and yield. They survive in diverse environments, both in plants, as pathogens, and also outside their hosts as saprophytes. Hence, they are confronted with numerous changing environmental parameters. During infection, plant pathogens have to deal with stressful conditions, such as acidic, oxidative and osmotic stresses; anaerobiosis; plant defenses; and contact with antimicrobial compounds. These adverse conditions can reduce bacterial survival and compromise disease initiation and propagation. Successful bacterial plant pathogens must detect potential hosts and also coordinate their possibly conflicting programs for survival and virulence. Consequently, these bacteria have a strong and finely tuned capacity for sensing and responding to environmental and plant stimuli. This review summarizes our current knowledge of the signals and genetic circuits that affect survival and virulence factor expression in three important and well-studied plant pathogenic bacteria with wide host ranges and the capacity for long-term environmental survival. These are: Ralstonia solanacerarum, a vascular pathogen that causes wilt disease; Agrobacterium tumefaciens, a biotrophic tumorigenic pathogen responsible for crown gall disease and Dickeya, a brute force apoplastic pathogen responsible for soft-rot disease.

Impact of physical aquatic parameters on the annual rhythmicity of sex steroid and cortisol and their interrelationship in two distantly related fish population

A chronological relationship between the annual profiles of stress hormone cortisol and male (testosterone and 11-keto testosterone) and female (17β-estradiol) sex steroids, the key regulator of annual reproductive cycle has been sought in two different group of fish (Mystus gulio and Parambassis ranga) under natural photothermal conditions. The serum samples were collected at two different times in each month (from January to December) and the same was repeated for two consecutive years throughout an annual cycle. The fluctuations of major physical factors (temperature, salinity, pH, dissolved oxygen and carbon dioxide) and presence of three important heavy metals were also estimated accordingly. Therefore, the present study aims to explore the rhythmic responses of sex steroids and cortisol to assess the impact of different environmental stressors on selected fish species. We tried to develop a realistic conceptual idea to analyze and predict the effect of changing environmental parameters on the possible shift in the rhythmicity of aforesaid hormones in two different groups of fish and their adaptive responses to thrive in such environment. Our results indicated that the fluctuation of circannual rhythms of testosterone, 17-β estradiol and 11-KT varied according to species, was related with the physical factors of the aquatic system and temperature was the most important factor among them. This information might help to frame the reproductive strategies for different fish species, as well.

Application of numerical model of the photovoltaic module to the practical comparative analysis

This paper includes a model of photovoltaic module based on a basic catalogue data, taking into account the analysis of series and shunt resistance. These resistances are searched with accuracy 0.001 Ohms, but their influence is taken into account in the electrical parameters for each iteration. In addition, the model takes into account changes in environmental parameters: solar radiation intensity and the operating temperature, for which is sought the optimal operating point of the module. This allows to perform a step towards practical applications of the model, including comparative analysis. In the literature numerical models are used to verify the functioning of the PV modules as a function of voltage or current. In the paper is included description of searching the voltage at which the operating point will achieve maximum power for given environmental parameters. This approach to the issue allows to determine the power plane, on which the inverter should move, and this was the first aim of the work. Moreover, it is therefore possible to compare different PV modules without necessity to build the test stands. The output numerical data for different PV modules can be compared with each other and the best model can be chosen to fulfil the condition of the maximum power per day for the desired geographical location. The ability to perform this kind of analysis is the second aim of the work.

Shielding in biology and biophysics: Methodology, dosimetry, interpretation

An interdisciplinary review of the publications on the shielding of organisms by different materials is presented. The authors show that some discrepancies between the results of different researchers might be attributed to methodological reasons, including purely biological (neglect of rhythms) and technical (specific features of the design or material of the screen) ones. In some cases, an important factor is the instability of control indices due to the variations in space weather. According to the modern concept of biological exposure to microdoses, any isolation of a biological object by any material necessarily leads to several simultaneous changes in environmental parameters, and this undermines the principle of “all other conditions being equal” in the classical differential scheme of an experiment. The shielding effects of water solution are universally recognized and their influence is to be observed for all organisms. Data on the exposure of living organisms to weak combined magnetic fields and on the influence of space weather enabled the development of theoretical models generally explaining the effect of shielding for bioorganisms. Ferromagnetic shielding results in changes of both the static magnetic field and the field of radio waves within the area protected by the screen. When screens are nonmagnetic, changes are due to the isolation from the radio waves. In both cases, some contribution to the fluctuations of measured parameters can be made by variations in the level of ionizing radiation.

Stem water storage dynamics of Vochysia divergens in a seasonally flooded environment

Stem radius measurements can vary over the short and medium-term in relation to changes in certain environmental parameters, providing useful information about the impacts of climate variation on tree physiology and growth processes. Here, use a variety of approaches to identify the main environmental variables that influence annual stem water dynamics in the tree Vochysia divergens in a seasonally flooded forest in Northwest Pantanal, Brazil. The circadian stem cycle and diel phases of stem radius (contraction, recovery and increment) was quantified over two growth seasons (2013–2015) using high resolution dendrometer measurements. Our results demonstrate that stem radial variation is strongly linked to water availability which, in turn, is significantly associated with soil water content (SWC) and actual vapor pressure (ea). Our data suggest that the duration of contraction and recovery phases are related to SWC, whereas the increment phase is more influenced by the phenological cycle of the tree. The contraction phase has a limiting association with high vapor pressure deficit (VPD) (decoupled from SWC), indicating stomatal regulation. The circadian stem cycle was characterized by monthly fluctuations reflecting atmospheric water demand status. Monthly mean actual vapor pressure (eamean) was strongly associated with annual variation in the amplitude of the circadian stem cycle.

Predictive modeling of European flat oyster (Ostrea edulis L.) fatty acid composition

This study investigates polyunsaturated fatty acids (PUFAs) of European flat oyster (Ostrea edulis L.) and their composition shift in relation to the interaction of selected factors in the marine environment of the Adriatic Sea, over an annual farming cycle. We advance the hypothesis that fatty acid composition may be predicted regarding the changes of abiotic environment parameters. Novel approach was developed as a tool for interpretation of PUFA ratio using mathematical models and algorithms, providing association and better prediction of observed variables compared to standard statistical techniques. Data analysis using R language package resulted in models that primarily provide the possibility to predict the PUFA value based on certain fluctuations in the environment. In addition to predictions, results present a useful tool for insight into the oysters’ quality and understanding of their basic biology in different environments. This is the first report of using mathematical modeling to investigate interactions between PUFA compositions of oyster meat relative to interactions of particular environmental variables. We furthermore discuss the potential of environmental variables in affecting the oyster PUFA composition and apply an approach providing a better insight into the health status and quality of oysters throughout the season. Model projection showed a nonlinear, parabolic dependence between the tested variables and dissolved oxygen. Both, the n-3 PUFA and DHA alone, were associated with an open-down parabolic relationship; the maximum levels were reached by 95 % oxygen saturation. The n-3 PUFAs and n-3/n-6 ratio were likely negatively affected by increase in sea water temperature, where a 15 % reduction in n-3 PUFAs content and 50 % reduction in n-3/n-6 proportion were predicted. Also, we detected FA ratios (AA/DHA, AA/EPA) and AA positively affected by increase in sulphate concentration and dissolved oxygen, respectively, and strongly negative prediction of ammonia level and sea water pH with AA, DHA and ARA/EPA ratio, respectively. These models might be applied to other aquatic species, for promotion of sea food quality, improvement of farming conditions and production, as well as for optimizing conditions in controlled trails.

Environmental Drivers of Differences in Microbial Community Structure in Crude Oil Reservoirs across a Methanogenic Gradient.

Stimulating in situ microbial communities in oil reservoirs to produce natural gas is a potentially viable strategy for recovering additional fossil fuel resources following traditional recovery operations. Little is known about what geochemical parameters drive microbial population dynamics in biodegraded, methanogenic oil reservoirs. We investigated if microbial community structure was significantly impacted by the extent of crude oil biodegradation, extent of biogenic methane production, and formation water chemistry. Twenty-two oil production wells from north central Louisiana, USA, were sampled for analysis of microbial community structure and fluid geochemistry. Archaea were the dominant microbial community in the majority of the wells sampled. Methanogens, including hydrogenotrophic and methylotrophic organisms, were numerically dominant in every well, accounting for, on average, over 98% of the total Archaea present. The dominant Bacteria groups were Pseudomonas, Acinetobacter, Enterobacteriaceae, and Clostridiales, which have also been identified in other microbially-altered oil reservoirs. Comparing microbial community structure to fluid (gas, water, and oil) geochemistry revealed that the relative extent of biodegradation, salinity, and spatial location were the major drivers of microbial diversity. Archaeal relative abundance was independent of the extent of methanogenesis, but closely correlated to the extent of crude oil biodegradation; therefore, microbial community structure is likely not a good sole predictor of methanogenic activity, but may predict the extent of crude oil biodegradation. However, when the shallow, highly biodegraded, low salinity wells were excluded from the statistical analysis, no environmental parameters could explain the differences in microbial community structure. This suggests that the microbial community structure of the 5 shallow, up-dip wells was different than the 17 deeper, down-dip wells. Also, the 17 down-dip wells had statistically similar microbial communities despite significant changes in environmental parameters between oil fields. Together, this implies that no single microbial population is a reliable indicator of a reservoir's ability to degrade crude oil to methane, and that geochemistry may be a more important indicator for selecting a reservoir suitable for microbial enhancement of natural gas generation.

Fine-scale monitoring of fish movements and multiple environmental parameters around a decommissioned offshore oil platform: A pilot study in the North Sea

A new underwater monitoring system was constructed using time-lapse photography and a suite of oceanographic instruments to characterise the dynamic relationships between changing environmental conditions, biological activities and the physical presence of offshore infrastructure. This article reports the results from a pilot study on fine-scale monitoring of fish movements in relation to changes in multiple environmental parameters observed at an offshore oil platform in the North Sea. Temporal changes in the number of saithe Pollachius virens were readily observed with a strong indication of diurnal rhythm of vertical movements. Key environmental parameters such as temperature, salinity, currents, tidal cycle, illumination, chlorophyll and dissolved oxygen also varied spatially (i.e. different depths) and/or temporally. If the monitoring system is to be deployed systematically at multiple offshore locations for longer duration as appropriately controlled experiments, this approach may greatly help understand the influence of redundant offshore man-made structures on the marine ecosystem.

Community structure, population dynamics and diversity of fungi in a full-scale membrane bioreactor (MBR) for urban wastewater treatment

Community structure, population dynamics and diversity of fungi were monitored in a full-scale membrane bioreactor (MBR) operated throughout four experimental phases (Summer 2009, Autumn 2009, Summer 2010 and Winter, 2012) under different conditions, using the 18S-rRNA gene and the intergenic transcribed spacer (ITS2-region) as molecular markers, and a combination of temperature-gradient gel electrophoresis and 454-pyrosequencing. Both total and metabolically-active fungal populations were fingerprinted, by amplification of molecular markers from community DNA and retrotranscribed RNA, respectively. Fingerprinting and 454-pyrosequencing evidenced that the MBR sheltered a dynamic fungal community composed of a low number of species, in accordance with the knowledge of fungal diversity in freshwater environments, and displaying a medium-high level of functional organization with few numerically dominant phylotypes. Population shifts were experienced in strong correlation with the changes of environmental variables and operation parameters, with pH contributing the highest level of explanation. Phylotypes assigned to nine different fungal Phyla were detected, although the community was mainly composed of Ascomycota, Basidiomycota and Chytridiomycota/Blastocladiomycota. Prevailing fungal phylotypes were affiliated to Saccharomycetes and Chytridiomycetes/Blastocladiomycetes, which displayed antagonistic trends in their relative abundance throughout the experimental period. Fungi identified in the activated sludge were closely related to genera of relevance for the degradation of organic matter and trace-organic contaminants, as well as genera of dimorphic fungi potentially able to produce plant operational issues such as foaming or biofouling. Phylotypes closely related to genera of human and plant pathogenic fungi were also detected.

Optimal PAR intensity for spring bloom in the Northwest Pacific marginal seas

Using ten years (2003–2012) of satellite Chlorophyll-a data, we report that annual phytoplankton bloom climax in the Northwest Pacific marginal seas (17°–58°N) delays northward at a rate of 22.98±2.86kmday−1. The spring bloom is a dominant feature of the phytoplankton seasonal cycle in this region, except for the northern South China Sea, which features a winter bloom. The sea surface hourly Photosynthetically Available Radiation (PAR) intensity averaged over the bloom peak duration is nearly uniform (1.04±0.10Wm−2h−1) among the four sub-regions (i.e. the northern South China Sea, the Kuroshio waters, the Sea of Japan and the Sea of Okhotsk), although different algal species in these four distinct ecological provinces could adapt to a much larger change in other environmental parameters (including total daily PAR, day length, sea surface temperature, net surface heat flux, mixed layer depth, wind speed and euphotic depth). The differences of the hourly PAR intensity between the four provinces during their bloom periods are smaller than those during non-bloom seasons. In contrast, an increasing total daily PAR (Wm−2day−1), due to the longer day length at higher latitudes, may balance decreasing sea surface temperature and induce algal flowering. Our results point to an optimal hourly light intensity for the annual phytoplankton bloom peak timing in this entire region, which could potentially become an indicator for the requirement of these annual bloom peaks.

An Energy Efficient Routing Protocol using ABC to Increase Survivability of WSN

days proficient design and realization of wireless sensor networks has turn into a hot area of research in recent time, due to the immense potential of sensor networks to enable applications that bond the substantial world to the virtual world. Wireless sensor network (WSN) is being used in surveillance, medical monitoring etc. Sensors nodes are typically built of few sensors and a mote unit. A Sensor is a piece of equipment which wits the information and passes it on to mote. Sensors are usually used to compute the changes in substantial environmental parameters like warmth, strain, moisture, noise, tremor and changes in the fitness parameter of person e.g. blood pressure and the rate at which the heart beats. In this research a technique named ABC Based Energy Efficient Protocol (ABCEEP) is projected to apply Artificial Bee Colony (ABC) to the problem of electing the cluster heads in the cluster set-up phase based on minimizing the cluster's consistency/break up/compactness (intra remoteness) and maximizing the cluster separation (inter remoteness) to proficiently increase the network life span and to get better stability period.

Environmental effects on natural frequencies of the San Pietro bell tower in Perugia, Italy, and their removal for structural performance assessment

Continuously identified natural frequencies of vibration can provide unique information for low-cost automated condition assessment of civil constructions and infrastructures. However, the effects of changes in environmental parameters, such as temperature and humidity, need to be effectively investigated and accurately removed from identified frequency data for an effective performance assessment. This task is particularly challenging in the case of historical constructions that are typically massive and heterogeneous masonry structures characterized by complex variations of materials' properties with varying environmental parameters and by a differential heat conduction process where thermal capacity plays a major role.While there is abundance of documented monitoring data highlighting correlations between environmental parameters and natural frequencies in the case of new structures, such as long-span bridges, similar studies for historical constructions are still missing, with only a few literature works occasionally reporting increments in natural frequencies with increasing temperature of construction materials due to the closure of internal micro-cracks in the mortar layers caused by thermal expansion.In order to gain some knowledge on the effects of changes in temperature and humidity on the natural frequencies of slender masonry buildings, the paper focuses on the case study of an Italian monumental bell tower that has been monitored by the authors for more than nine months. Correlations between natural frequencies and environmental parameters are investigated in detail and the predictive capabilities of linear statistical regressive models based on the use of several environmental continuous monitoring sensors are assessed. At the end, three basic mechanisms governing environmentally-induced changes in the dynamic behavior of the tower are identified and essential information is achieved on the optimal location and minimum number of environmental sensors that are necessary in a structural health monitoring perspective.

The transition from evolutionary stability to branching: A catastrophic evolutionary shift.

Evolutionary branching—resident-mutant coexistence under disruptive selection—is one of the main contributions of Adaptive Dynamics (AD), the mathematical framework introduced by S.A.H. Geritz, J.A.J. Metz, and coauthors to model the long-term evolution of coevolving multi-species communities. It has been shown to be the basic mechanism for sympatric and parapatric speciation, despite the essential asexual nature of AD. After 20 years from its introduction, we unfold the transition from evolutionary stability (ESS) to branching, along with gradual change in environmental, control, or exploitation parameters. The transition is a catastrophic evolutionary shift, the branching dynamics driving the system to a nonlocal evolutionary attractor that is viable before the transition, but unreachable from the ESS. Weak evolutionary stability hence qualifies as an early-warning signal for branching and a testable measure of the community’s resilience against biodiversity. We clarify a controversial theoretical question about the smoothness of the mutant invasion fitness at incipient branching. While a supposed nonsmoothness at third order long prevented the analysis of the ESS-branching transition, we argue that smoothness is generally expected and derive a local canonical model in terms of the geometry of the invasion fitness before branching. Any generic AD model undergoing the transition qualitatively behaves like our canonical model.

Individualistic weight perception from motion on a slope.

Perception of an object’s weight is linked to its form and motion. Studies have shown the relationship between weight perception and motion in horizontal and vertical environments to be universally identical across subjects during passive observation. Here we show a contradicting finding in that not all humans share the same motion-weight pairing. A virtual environment where participants control the steepness of a slope was used to investigate the relationship between sliding motion and weight perception. Our findings showed that distinct, albeit subjective, motion-weight relationships in perception could be identified for slope environments. These individualistic perceptions were found when changes in environmental parameters governing motion were introduced, specifically inclination and surface texture. Differences in environmental parameters, combined with individual factors such as experience, affected participants’ weight perception. This phenomenon may offer evidence of the central nervous system’s ability to choose and combine internal models based on information from the sensory system. The results also point toward the possibility of controlling human perception by presenting strong sensory cues to manipulate the mechanisms managing internal models.

Effect of hydrological variability on diatom distribution in Poyang Lake, China

Poyang Lake is the largest freshwater lake in China, and it has a seasonal flooding cycle that significantly changes the water level every year. The aim of this paper was to explain how these hydrological changes influence diatom populations in Poyang Lake. The yearly hydrological cycle can be divided into 4 phases: low water-level phase, increasing water-level phase, high water-level phase and decreasing water-level phase. Variations in the abundance of planktonic diatoms were studied using quarterly monitoring data collected from January 2009 to October 2013. Generally, diatoms were dominant in Poyang Lake and accounted for more than 50% of the total phytoplankton biomass except in July 2009 (26%) and January 2012 (35%). Aulacoseira granulata and Surirella robusta were the predominant species in all four phases, and they accounted for 25.02% to 56.89% and 5.07% to 14.78% of the total phytoplankton biomass, respectively. A redundancy analysis (RDA) showed that changes in physico-chemical parameter were related to the water level, and changes in diatom biomass were related to nitrite levels and pH. These results indicate that changes in environmental parameters related to both seasonal variations and water-level fluctuations caused variations in diatom biomass and community composition in Poyang Lake. Furthermore, extreme hydrological events can have different influences on the diatom community composition in the main channel and lentic regions. This research provides data on the diatom variations in Poyang Lake and will be useful for establishing biological indicators of environmental change and protecting Poyang Lake in the future.

Real-Time Wildfire Monitoring and Alert System Using GSM Technology

Environmental related issues and parameters are of utmost importance to man, and is essential to his existence and influence and thus he alwaysseeks for an improved system that would be able to capture and monitor the changes in environmental parameters irrespective of time and location so as to provide for measures that will forestall abnormalities and cater for emergencies.This paper presents research work on a system that is capable of providing real time remote wildfire monitoring and SMS alert. Thework aimed at the design and implementation of a low cost but efficient and flexible wildfire monitoring and alert system using GSM technology. It was designed in such a way that the Monitoring of wildfire would be achieved with the use of temperature and smoke sensorscoupled with a control unit and transmitter module all of which are battery powered. Fire and smoke are sensed and measured by the sensors which send the signals to the control unit for proper processing and determination of the smoke rate.This is displayed on an LCD screen, then an alert is sent to the mobile phone of the environmental personnel via SMS while simultaneously triggering an alarm in control room. Thus this system presents a continuous, real time, remote, safe and accurate monitoring of wildfires and smoke rate hence ensuring the conservation and preservation of wildlife, natural habitats and the ecosystem, and at the same time, helping tocurb high impact human, industrial and environmental damage

Dynamics of abundance of the mid- to late Pridoli conodonts from the eastern part of the Silurian Baltic basin: Multifractals, state shifts, and oscillations

The Pridoli epoch is one of the most geobiologically unstable intervals in the Silurian period. However, the ecological and evolutionary dynamics of the biota from this time are still poorly understood. Here we present a comprehensive quantitative time-series analyses of conodont abundances during the middle and the upper parts of the Pridoli epoch. The study reveals that the stratigraphic series of conodont abundances has a multifractal structure. This feature implies the presence of multiple serially correlated processes hierarchically operating on different time scales and interacting in a multiplicative fashion. Estimation of a maximal Lyapunov exponent and a test for presence of determinism also revealed a chaotic and non-linear low-dimensional nature of long-term conodont abundance dynamics. The most probable (but not exclusive) mechanism for the origin of chaos in the time series of conodont abundance is that conodont abundances tracked changes in crucial environmental parameters, most probably related to the climate that exhibits long term chaos. The complex and non-linear nature of the conodont dynamics is also revealed by a moving-window correlation analyses of conodont abundances and by an environmental proxy time series. We found three alternating episodes of different correlation patterns between conodont abundances and the δ13C record. In the middle and upper most Pridoli interval there are positive but statistically non-significant correlations between these two variables. In contrast the lower part of the upper Pridoli (middle of the Jūra formation) exhibits negative and statistically significant correlation between the variables. In addition moving-window standard deviation analyses reveals that during the transitions between these episodes, there were abrupt changes in the variance in both the carbon isotopes and the conodont abundances, which implies that these episodes represent alternative states in the way the earth system functioned that were punctuated by the critical transitions between them. The interval with negative correlations between abundances and isotopes was also marked by a profound evolutionary turnover of acanthodians and to lesser extent conodonts. This interval most probably represented an anomalous time, with differing ecological rules and increased macroevolutionary rates, which can be interpreted as a turnover pulse. The spectral cyclostratigraphic analyses of the abundance data reveals that conodont abundances also exhibited periodic oscillations at several frequencies. The cycles determined for the analysis have the period lengths of 56, 99, 127 and 950 Ka, which probably were caused by the periodic changes in the obliquity and eccentricity of Earth9s orbit. The proposed proximate mechanism that controlled cyclic changes in the abundances of conodonts, based on the climatological deductions, was a variation in nutrients supplies that was due to changes in the degree of seasonality in the tropics, driven by Milankovitch cycles. It is probable that the described state shifts in the way that the ecosystem functioned were also forced by long-term Milankovitch cycles.

Effects of metal contamination in situ on osmoregulation and oxygen consumption in the mudflat fiddler crab Uca rapax (Ocypodidae, Brachyura)

The contamination of estuaries by metals can impose additional stresses on estuarine species, which may exhibit a limited capability to adjust their regulatory processes and maintain physiological homeostasis. The mudflat fiddler crab Uca rapax is a typical estuarine crab, abundant in both pristine and contaminated areas along the Atlantic coast of Brazil. This study evaluates osmotic and ionic regulatory ability and gill Na+/K+-ATPase activity in different salinities (<0.5, 25 and 60‰ S) and oxygen consumption rates at different temperatures (15, 25 and 35°C) in U. rapax collected from localities along the coast of São Paulo State showing different histories of metal contamination (most contaminated Ilha Diana, Santos>Rio Itapanhaú, Bertioga>Picinguaba, Ubatuba [pristine reference site]). Our findings show that the contamination of U. rapax by metals in situ leads to bioaccumulation and induces biochemical and physiological changes compared to crabs from the pristine locality. U. rapax from the contaminated sites exhibit stronger hyper- and hypo-osmotic regulatory abilities and show greater gill Na+/K+-ATPase activities than crabs from the pristine site, revealing that the underlying biochemical machinery can maintain systemic physiological processes functioning well. However, oxygen consumption, particularly at elevated temperatures, decreases in crabs showing high bioaccumulation titers but increases in crabs with low/moderate bioaccumulation levels. These data show that U. rapax chronically contaminated in situ exhibits compensatory biochemical and physiological adjustments, and reveal the importance of studies on organisms exposed to metals in situ, particularly estuarine invertebrates subject to frequent changes in natural environmental parameters like salinity and temperature.