Significant Changes In Environmental Conditions Research Articles

Long‐Term Variability of Phytoplankton Primary Production in the Ulleung Basin, East Sea/Japan Sea Using Ocean Color Remote Sensing

AbstractIn recent years, significant changes in environmental conditions and marine ecosystems have been observed in the East Sea/Japan Sea. This study investigates the long‐term environmental dynamics and phytoplankton responses in the Ulleung Basin, situated in the southwestern East Sea/Japan Sea, utilizing satellite and in situ data from 2002 to 2021. Over this period, there was a noticeable increase in sea surface temperature (SST) (r = 0.5739, p < 0.01), accompanied by decreasing mixed layer depth (MLD) and chlorophyll‐a (Chl‐a) concentration (r = −0.6193 and −0.6721, respectively; p < 0.01). Nutrient concentrations within the upper 50 m significantly declined for nitrate and phosphate. A reduction in the N:P ratio indicated a shift from phosphorus‐limited to nitrogen‐limited environment. Moreover, primary production (PP) demonstrated a decreasing trend (r = −0.5840, p < 0.01), coinciding with an increase in small phytoplankton contribution (r = 0.6399, p < 0.01). Rising SST potentially altered the water column's vertical structure, hindering nutrient entrainment from the deep ocean. Consequently, this nutrient limitation may increase small phytoplankton contribution, resulting in a decline in total PP. Under the IPCC's SSP5‐8.5 scenario, small phytoplankton contribution in the Ulleung Basin is projected to rise by over 10%, resulting in a 29% average PP decrease by 2100. This suggests a diminishing energy supply to the food web in a warming ocean, impacting higher trophic levels and major fishery resources. These findings emphasize the critical need for understanding and monitoring these environmental shifts for effective fisheries management and marine ecosystem conservation.

Yield plasticity of new varieties of soft winter wheat (Triticum aestivum L.) in different soil and climatic conditions of Ukraine

Purpose. To determine the level of productivity of new varieties of soft winter wheat, their stability and plasticity when grown in different soil and climatic conditions of Ukraine. Methods. The field trial was carried out in 2022–2023 under the conditions of the research stations of the Ukrainian Institute for Plant Variety Examination (UIPVE) in the Steppe, Forest Steppe and Polissia soilclimatic zones. The peculiarities of plant growth and development, the yield formation of 34 new varieties of soft winter wheat were studied. Plasticity and stability of yield formation were calculated and analyzed according to the Ebergard – Russell method, general homeostaticity and selection value according to Khangildin V.V. and Lytvynenko N.A. In the course of the research, computational and statistical methods were used. Analysis and synthesis were used to draw conclusions. Results. The yield varied from 5.4 to 8.4 t/ha, depending on the soil and climate zone and the location of the trial. The variety ‘LG Optimist’ had the highest average yield (8.1 t/ha) and ‘YUSON’ the lo west (6.0 t/ha). The most favorable conditions for the study of growth and development of genotypes in 2022 were in the Forest-Steppe (Ij = 0.9) and Polissia (Ij = 0.6) zones, in 2023 – Polissia (Ij = 0.2); the worst in 2022 – in the Steppe (Ij = –0.7), in 2023 – in the Steppe (Ij = –0.7) and ForestSteppe (Ij = –0.5) zones. In 2023, the best climatic conditions were in the Polissia zone (Ij = 0.2), the worst were in the points located in the Steppe (Ij = –0.7) and Forest Steppe (Ij = –0.5) zones. The theoretical yield values of the varieties at the research points did not differ from the actual values and averaged 7.1 t/ha, ranging from 6.0 to 8.1 t/ha. High homeostaticity and low level of variation (V ≤ 10.0%) were found in the varieties ‘Yevraziia’ (Hom = 15.6), ‘Dekaster’ (Hom = 15.2), ‘FORSAIT’ (Hom = 13.9) and ‘LG Optimist’ (Hom = 12.1). In addition, ‘LG Optimist’ (Sc = 6.9) and ‘Dekaster’ (Sc = 6.6) had the highest breeding value. The variety ‘FORSAIT’ (bi = 0.2; S2 di = 0.24), with an average yield of 7.4 t/ha, has a high plasticity, so it is recommended to grow it on extensive backgrounds and in unfavorable conditions. Varieties ‘Yevraziia’, ‘Nosivochka’, ‘SOLIFLOR CS’, ‘Mizynka’, ‘Troiana’, ‘LG Optimist’, ‘Biskvit’, ‘MIP Dovira’, ‘Etual’, ‘Tvorchist Odeska’, ‘Attribut’, ‘Epihraf’, ‘Dekaster’, ‘Epitet’, ‘Jannis’, ‘Pamiati Horlacha’, ‘Trembita Bilotserkivska’ and ‘Slava Unavy’ with a combined manifestation of high ecological plasticity bi = 1 and stability S2 di = 0 in average grain yield 7.2 t/ha, according to the genotype respond well to the improvement of growing conditions and are stable, are considered the most practically valuable. Conclusions. New varieties of soft winter wheat, when grown in different soil and climatic conditions, fully develop their genetic potential under significant changes in environmental conditions and produce the highest yield that can be obtained under ideal conditions.

Physico-Chemical Dynamics of Vanname Shrimp (Litopenaeus vannamei) Cultivation Pond Water Quality with A Recirculation System

In 2021 Indonesia was experiencing an increase in shrimp exports. Litopenaeus vannamei shrimp is one of the shrimp with a good increase in exports and a type of shrimp with high resistance to environmental disturbances. Indonesia has land potential of about 2,964,331.24 hectares which can be used to increase shrimp production. The cultivation technique that can maximize this potential is a superintensive technique that uses closed aquaculture system. Recirculating Aquaculture system (RAS) is a closed aquaculture system that is suitable for shrimp farming because the water treatment is separated so that there is no significant change in environmental conditions. In this study, the RAS system was equipped with the use of an ultrafiltration membrane as a tool for the inflow water treatment. This study observe the physico-chemical water dynamics that occur during one cultivation cycle. It was observed that the DO of the pond decreased as the shrimp grew, the salinity increased during the cultivation process if there was no water replacement, the brightness decreased every day until it reached a specified point. Temperatures tended to be low due to weather factors, ammonia levels tended to decrease but nitrite and nitrate levels tended to increase due to the slower transformation rate of nitrite and nitrate. The operating system for this process was carried out by adding CaO and sugar. The addition of CaO ranges from 100-600 g/day. The effective addition of sugar if there was a spike in ammonia levels was 1.25 kg/day.

Improving estimates of sub-daily gross primary production from solar-induced chlorophyll fluorescence by accounting for light distribution within canopy

Solar-induced chlorophyll fluorescence (SIF) has long been regarded as a proxy for photosynthesis and has shown superiority in estimating gross primary production (GPP) compared to traditional vegetation indices, especially in evergreen ecosystems. However, current SIF-based GPP estimations regard the canopy as a large leaf and seldom consider the impact of interactions among light, canopy structure, and leaf physiology. In this study, we proposed GPP estimation models with different descriptions of light–structure–physiology interactions (including the layered model, the two-leaf model, and the layered two-leaf model) and compared their performances with the big-leaf model using half-hourly (or hourly) observations at evergreen needleleaf forest sites. First, we found that the big-leaf model underestimated GPP, especially at noon. All models showed higher accuracy than that of the big-leaf model. Second, we investigated the diurnal dynamics of GPP estimations in each canopy layer and found that models with a two-leaf assumption captured the diurnal variations in GPP better than that with the layered assumption. We also deduced that the poor performance of the big-leaf model was related to its overestimation of the overall light stress on the redox state of PSII reaction centers (qL). Finally, we noticed that the qL at the canopy scale had lower sensitivity to light change than the single-leaf qL and that the light response of canopy-scale qL was influenced by the leaf area index during seasonal cycles. Overall, this study describes methods to accurately estimate sub-daily GPP from SIF in evergreen needleleaf forests and demonstrates that the interactions among light, canopy structure, and leaf physiology regulate the SIF-GPP relationship at the canopy scale. Further, it indicates the need to consider the description of light distribution within the canopy in next-generation terrestrial biosphere models, even if they incorporate SIF to constrain their parameterization. Thus, upscaling the established leaf-scale mechanistic SIF-GPP relationship or findings to canopy-scale applications still requires much work, especially when there are significant changes in environmental conditions and their within-canopy distributions.

Impact of mini-hydropower on the chemical composition of water and phytoplankton of the reservoirs of the Forest-Steppe of Ukraine

The peculiarities of the transformation of river ecosystems in the reservoir at the construction of mini-hydropower plants have been found out. It was also found that the large-scale hydraulic engineering in the second half of the XX century caused significant changes in environmental conditions in the waterbodies, which has led to negative dynamics of species richness of aquatic organisms in general and phytoplankton in particular. Reservoir building has a significant negative impact on river ecosystems: currents slow down and disappear, canals become silted up, harmful substances of household and industrial waste gradually accumulate. The transformation of rivers into lake-type reservoirs is also accompanied by changes in the species composition and structure of phytoplankton. Eutrophication of reservoirs becomes typical. All this leads to significant degradation in aquatic ecosystems.

Changes in Personal Values in Pandemic Times

The COVID-19 pandemic has had immense impact on people’s lives, potentially leading individuals to reevaluate what they prioritize in life (i.e., their values). We report longitudinal data from Australians 3 years prior to the pandemic, at pandemic onset (April 2020, N = 2,321), and in November–December 2020 (n = 1,442). While all higher order values were stable prior to the pandemic, conservation values, emphasizing order and stability, became more important during the pandemic. In contrast, openness to change values, emphasizing self-direction and stimulation, showed a decrease during the pandemic, which was reversed in late 2020. Self-transcendence values, emphasizing care for close others, society, and nature, decreased by late 2020. These changes were amplified among individuals worrying about the pandemic. The results support psychological theory of values as usually stable, but also an adaptive system that responds to significant changes in environmental conditions. They also test a new mechanism for value change, worry.

Groundwater quality changes in peri-urban areas of the Walloon region of Belgium

An extensive survey of groundwater quality was performed at the regional scale in peri-urban and industrial contexts of the Walloon Region (Belgium). To this end, 243 sampling locations from 8 areas located in different geological contexts and different peri-urban areas of the region were sampled outside pollution hotspots related to contaminated sites. Each groundwater sample was analyzed for 19 inorganic trace elements, 59 organic micro-pollutants and 8 major and minor elements. Five physico-chemical parameters were measured in the field, at the time of sampling to determine the environmental conditions prevailing in groundwater. Existing groundwater chemical data available outside such peri-urban and industrial areas were also compiled from existing groundwater quality databases for comparison. Most of the organic and inorganic pollutants are detected and their levels of occurrence are described statistically. Cumulative distribution function plots allow comparing the distributions of inorganic trace elements in and outside the urbanized and industrialized areas and among the different prevailing geological contexts. Two indicators are introduced, one quantifying the impact on inorganic trace elements of diffuse pollution in urban and industrial areas, the other reflecting the influence of lithology on concentrations in groundwater. Results show that the composition of groundwater is altered in peri-urban and industrial areas with increased concentrations for several organic pollutants and for most inorganic trace elements. However, the results clearly indicate that for the inorganic trace elements, anthropogenic influence is not limited to increased discharge of pollutants in the urban and industrial areas but also to significant changes in environmental conditions, with more reducing and acidic conditions observed in groundwater. The influence of lithology is also marked in the data set. From a more pragmatic point of view, the data set has been also used to derive upper limits of pollutant background concentrations to be used in decision-making related to the management of contaminated groundwater in urban and industrial environments in the Walloon Region.

Sensitivity of genital and somatic traits of scorpions to developmental instability caused by increasing urbanization: A 20-year experiment

Urbanization causes the loss of large amounts of habitat and produces significant changes in environmental conditions with consequences in the individual’s behavior, morphology, and physiology in natural populations. The urbanization can impact in the individual’s development instability (DI) that may be measured with the fluctuating asymmetry (FA) level making it an environmental quality bioindicator. In addition, the FA of each trait should be interpreted considering the trait functional importance, morphogenesis and history of selection pressures. In this paper, we evaluated the impact of two decades of increasing urbanization levels over a population of the pampean scorpion Bothriurus bonariensis. We analyze the FA level in somatic and genital traits in adult individuals of both sexes, collected every ~ 10 years (1997, 2008, 2018). Interestingly, in this study the somatic traits (pedipalp chelae) would be under directional selection and are shaped throughout the individual’s growth. In contrast, the genital traits (male’s hemispermatophore) are involved in the sperm transfer process and could be under stabilizing selection. Also, hemispermatophores are affected for less time by environmental stressors since they are formed once the individual has reached sexual maturity. Our results showed a significant increase in the FA levels in somatic traits of males and females, according to the increase of urbanization along years. In contrast, genital traits showed no changes in the level of FA in females, and only a few male genital traits presented an increase in the FA level. This work shows evidence that the measured scorpion traits (under different selective pressures and morphogenesis) might present differences in their susceptibility to environmental stress. We discuss these results in a context of DI of individuals caused by urbanization. We support the idea that the level of FA can be useful as an index to evaluate the effects of environmental stress on invertebrate populations. Furthermore, our paper presents the scorpions as a good model that could be used as an indicator group for studying the impact of the anthropogenic disturbance factors on natural ecosystems.

Estimate of parameters changing of the Lymantria dispar artificial population in different environmental conditions using the quasispecies model

This paper gives an interpretation of the quasispecies concept for an experiment of growing the Lymantria dispar artificial population. The changes estimate in the population parameters for a significant change in environmental conditions at the stage of hatching caterpillars from the eggs was given. Three numerical and two random parameters were used for quantitative analysis. They characterize the development of individuals of the population at this stage. The parameter changes significance was verified with using statistical tests. The results obtained do not contradict the quasispecies model. The use of fuzzy sets describes the transition from one quasispecies to another at a significant change in environmental conditions.

Microgravity Environments: The Physical Exercise in The Space

The human body has a great capacity for adaptation, even in the case of significant changes in environmental conditions; like prolonged microgravity. The force of gravity on the earth produces an acceleration of 1g (g is the symbol that indicates the acceleration due to gravity). The term microgravity indicates a reduced force of gravity and is therefore used to describe conditions in which the force of gravity is less than that on the earth’s surface (less than one g). For example, the gravity force of the moon is only 17% of that of the earth, or 0.17g. The term microgravity is often used to describe conditions in space, because the body may not always be in conditions of weightlessness, i.e. at 0g.

Sedimentary processes and products in a mesotidal salt marsh environment: insights from Groves Creek, Georgia

Southeastern salt marshes are important repositories of sediment and carbon, and their formation is heavily dependent on deposition and accumulation of inorganic sediment. This study examined Groves Creek marsh near Savannah, GA, a typical Spartina alterniflora salt marsh of the southeastern US. Analyses were focused on the character, deposition and accumulation of material within the marsh on daily, monthly, decadal and centennial timescales, to determine the dominant factors in material supply and redistribution, and on its stratigraphy to determine the 1,000-year history of Groves Creek salt marsh development. Modern processes create gradients in grain size, which shows little variation from the tidal channel flanks up to mean sea level, and which coarsens with distance into the marsh from mean sea level to mean high water. This unexpected result suggests that, although floc transport is an important mechanism of sediment supply near the channel margins, energetic events must supply coarser materials to the marsh platform, where they are not readily removed by typical energy regimes. Daily deposition can approach ~3 g/cm2 year; however, centennial accumulation rates are orders of magnitude lower (0.11±0.05 g/cm2 year) and are similar to those present over the past 300 years (0.05–0.2 g/cm2 year), indicating that much of the daily deposition is remobilized. Stable isotopic δ13C (average –18.7‰) and δ15N (average 5.7‰) values most likely indicate a large contribution from S. alterniflora as a carbon source throughout the marsh, although heavier δ15N on the channel flanks suggest that benthic algae may be locally important. Geologic, geochemical and microfossil evidence suggests that depositional conditions in the Groves Creek marsh have changed significantly over the past ~1,000 years, creating a distinct fining-upward sequence. This sequence preserves the signature (from bottom to top) of subtidal flats grading to intertidal sandflats, an erosional lag created by a migrating tidal channel, point bar deposits, channel fill deposits, and a capping salt marsh. A significant change in environmental conditions occurred between 360–500 cal years BP, which changed the character of geological, geochemical and microfossil components in the marsh, and, because this observation is robust throughout the southeastern US, hints at a major change in estuarine and coastal systems at this time.

Microbial attack of archaeological bones versus high concentrations of heavy metals in the burial environment. A case study of animal bones from a mediaeval copper workshop in Paris

Microbial attack is one of the key processes altering archaeological bone during the early stage of diagenesis. Some burial conditions seem more prone to prevent microbial attack in archaeological bone. It is generally admitted that the presence of certain metals in the burial environment such as copper may have an inhibiting effect on microbial destruction of archaeological bone. This study was aimed at evidencing such effects by the investigation of different archaeological animal bones excavated from several activity zones of one French archaeological urban site corresponding to a mediaeval copper alloys workshop in Paris, at Hôtel de Mongelas. The analytical approach combined morphological observations (SEM), structural investigations (FT-IR, XRD, and TEM) and chemical analyses (SEM/EDX and μPIXE/PIGE) of archaeological bones at different scales down to the nanoscale. It permitted the classification of the bones as a function of their contamination with heavy metals, their conservation state and the presence of signs of microbial attack. Correlations between the observed alteration features and the metallurgical activity on this site as well as the underlying alteration processes are discussed. An inhibiting effect of heavy metals on the microbial attack could be deduced from the available, though restricted, data in agreement with the expectation. However, the relationship between heavy metal uptake and microbial alteration of bone depends on other diagenetic factors and their progress such as bone collagen content, crystallinity of bone mineral, soil geochemistry and hydrology. Significant changes in environmental conditions over time, which can especially occur in urban sites, can also influence alteration phenomena. Generally, simultaneous alterations induced by heavy metal uptake and microbial attack seem to take place in the very early stage of diagenesis and influence one another in sites with soils highly contaminated in heavy metals.

Shape Spaces for Prealigned Star-Shaped Objects—Studying the Growth of Plants by Principal Components Analysis

Summary We analyse the shapes of star-shaped objects which are prealigned. This is motivated from two examples studying the growth of leaves, and the temporal evolution of tree rings. In the latter case measurements were taken at fixed angles whereas in the former case the angles were free. Subsequently, this leads to different shape spaces, related to different concepts of size, for the analysis. Whereas several shape spaces already existed in the literature when the angles are fixed, a new shape space for free angles, called spherical shape space, needed to be introduced. We compare these different shape spaces both regarding their mathematical properties and in their adequacy to the data at hand; we then apply suitably defined principal component analysis on these. In both examples we find that the shapes evolve mainly along the first principal component during growth; this is the ‘geodesic hypothesis’ that was formulated by Le and Kume. Moreover, we could link change-points of this evolution to significant changes in environmental conditions.

Shape spaces for prealigned star-shaped objects-studying the growth of plants by principal components analysis

Summary. We analyse the shapes of star-shaped objects which are prealigned. This is motivated from two examples studying the growth of leaves, and the temporal evolution of tree rings. In the latter case measurements were taken at fixed angles whereas in the former case the angles were free. Subsequently, this leads to different shape spaces, related to different concepts of size, for the analysis. Whereas several shape spaces already existed in the literature when the angles are fixed, a new shape space for free angles, called spherical shape space, needed to be introduced. We compare these different shape spaces both regarding their mathematical properties and in their adequacy to the data at hand; we then apply suitably defined principal component analysis on these. In both examples we find that the shapes evolve mainly along the first principal component during growth; this is the ‘geodesic hypothesis’ that was formulated by Le and Kume. Moreover, we could link change-points of this evolution to significant changes in environmental conditions.

High-resolution nannofossil biochronology of middle Paleocene to early Eocene at ODP Site 1262: Implications for calcareous nannoplankton evolution

Over the last several decades debates on the ‘tempo and mode’ of evolution have centered on the question whether morphological evolution preferentially occurs gradually or punctuated, i.e., with long periods of stasis alternating with short periods of rapid morphological change and generation of new species. Another major debate is focused on the question whether long-term evolution is driven by, or at least strongly influenced by changes in the environment, or by interaction with other life forms. Microfossils offer a unique opportunity to obtain the large datasets as well as the precision in dating of subsequent samples to study both these questions. We present high-resolution analyses of selected calcareous nannofossils from the deep-sea section recovered at ODP Site 1262 (Leg 208) in the South-eastern Atlantic. The studied section encompasses nannofossil Zones NP4–NP12 (equivalent to CP3–CP10) and Chrons C27r–C24n.We document more than 70 biohorizons occurring over an about 10 Myr time interval, (∼ 62.5 Ma to ∼ 52.5 Ma), and discuss their reliability and reproducibility with respect to previous data, thus providing an improved biostratigraphic framework, which we relate to magnetostratigraphic information, and present for two possible options of a new Paleocene stratigraphic framework based on cyclostratigraphy. This new framework enabled us to tentatively reconstruct steps in the evolution of early Paleogene calcareous nannoplankton through documentation of transitional morphotypes between genera and/or species and of the phylogenetic relations between the genera Fasciculithus, Heliolithus, Discoasteroides and Discoaster, as well as between Rhomboaster and Tribrachiatus. The exceptional record provided by the continuous, composite sequence recovered at Walvis Ridge allows us to describe the mode of evolution among calcareous nannoplankton: new genera and/or new species usually originated through branching of lineages via gradual, but relatively rapid, morphological transitions, as documented by the presence of intermediate forms between the end-member ancestral and descendant forms. Significant modifications in the calcareous nannofossil assemblages are often “related” to significant changes in environmental conditions, but the appearance of structural innovations and radiations within a single genus also occurred during “stable” environmental conditions. These lines of evidence suggest that nannoplankton evolution is not always directly triggered by stressed environmental conditions but could be also driven by endogenous biotic control.

Biotic and environmental changes in the Permian–Triassic boundary interval recorded on a western Tethyan ramp in the Bükk Mountains, Hungary

Complete, continuous marine Permian–Triassic (P–T) boundary sections in the Bükk Mountains, Northern Hungary, represent a ramp setting on the margin of the western Tethys. The Upper Permian succession comprises limestone rich in calcareous algae, foraminifera, and skeletal fragments of metazoans. A significant reduction of biogenic components occurs in the topmost limestone layers below the “boundary shale bed” (BSB). It coincides with the beginning of a gradual negative shift in δ 13C carb values that continues into the BSB. The BSB consists predominantly of marly siltstones that are similar to the insoluble residue of the underlying limestone. A second biotic decline is recorded in the upper-third of the BSB, where the continuous negative shift in δ 13C values is superimposed by a sharp and quasi-symmetric negative peak. The δ 13C peak is confined to the shale bed and is not correlated with the lithological change, therefore diagenetic or other secondary effects are ruled out. The carbon isotope signal reflects primary processes related to significant changes in environmental conditions. Correlation and comparison of sedimentological, biotic, geochemical and mineralogical features of the studied sections in the Bükk Mountains with other Tethyan P—T sections in the Southern Alps, Dinarides, Iran, Kasmir (India) and southern China are discussed. The continuous shift in δ 13C values is most probably related to a decrease in bioproductivity, whereas the sharp peak is attributed to an addition of C strongly depleted in 13C isotope to the ocean–atmosphere system. The most plausible model is a massive release of methane from gas–hydrate dissociation. This event led to the extinction of the already impoverished biota. Scarcity of metazoans and prolonged unfavourable environmental conditions gave rise to a bloom of microbial communities. Mineralogical and geochemical analyses failed to reveal any evidence for extraterrestrial effects or synchronous volcanism were found in the studied sections.

Adaptive fault-tolerance in complex real-time distributed computer system applications

In many challenging applications, environmental conditions that affect fault-tolerance requirements imposed on computer systems change dynamically. As significant changes in environmental conditions or in internal computing resource conditions occur, the set of fault-tolerance mechanisms that are effective also changes. The purpose of adaptive fault-tolerance (AFT) is to meet the dynamically and widely changing fault-tolerance requirement by efficiently and adaptively utilizing a limited and dynamically changing amount of available redundant processing resources. This paper is an attempt to define the notion of AFT in a reasonably concrete form, identify major technical issues to be resolved for practical realization of AFT, and illustrate some feasible approaches to resolving the major issues. After discussing the basic concept and major research issues, an important case of AFT management, which is to adapt to the change of the environment from the soft-real-time mode to the hard-real-time mode, is examined in some detail.

A Kinetic Study of the Colony Growth of Streptomyces coelicolor A3(2) and J802 on Solid Medium

Summary: Colony growth kinetics of Streptomyces coelicolor A3(2), the wild-type strain, and J802, a mutant incapable of utilizing agar as the sole carbon and energy source, have been studied on solid medium. General features comparable to colony growth of filamentous fungi were observed in both streptomycete strains. Hyphal frequency at the margins of colonies was assessed as the number of hyphae crossing an are of defined length and increased in an exponential manner with distance from the margin, reaching a maximum at approximately 200 μm. Aerial hyphal initials were formed approximately 350 μm from the margin. Colony radial extension was linear, but in the wild-type strain grown at low medium depths, growth was sometimes multiphasic, with successive phases of linear growth each exhibiting a slower radial growth rate than that of the preceding phase. Hyphal frequency at the colony margin decreased as colony diameter increased, indicating significant changes in environmental conditions in the peripheral growth zone during colony growth. In the primary phase of linear growth, the colony radial growth rate of both strains was independent of medium depth and in the absence of a cellophane membrane was independent of glucose concentration. Colony radial growth rate of strain J802 growing on a cellophane underlay increased with glucose concentration. Hyphal frequency of strain A3(2) increased gradually with medium depth but was independent of glucose concentration. In strain J802, hyphal frequency exhibited a strong dependence on both medium depth and glucose concentration. A threshold glucose concentration for growth was not found and inhibition of strain A3(2) occurred above 1 gl−1. The results agree with many aspects of accepted theories for colony growth of both unicells and filamentous fungi, but suggest production of staling products and/or secondary metabolites to be of equal significance to nutrient limitation in controlling colony development.

Tree Mortality in Mangrove Forests

Twenty-eight worldwide reports of massive mangrove tree mortalities are reviewed. Massive mortality is defined as tree mortalities that occur in response to rapid environmental change and affect all size dasses. Massive mortality occurs in addition to normal tree mortality. Normal tree mortality was described using structural data from 114 mangrove stands. This mortality is density dependent, follows orderly time dependent patterns dictated by stand maturation (related to average tree diameter), and usually occurs in the smaller diameter size classes. Disease and other biotic factors do not appear to be primary causes of massive mangrove mortalities. Instead, these factors appear to attack forests weakened by changes in the physical environment. Mangrove environments are dynamic and cyclical and mangrove associations adapt to such environments by both growing and dying fast. Mangrove species' characteristics such as the capacity to produce large quantities of propagules that take advantage of dispersal agents, sharp species zonations, and even-aged populations contribute to the rapid growth-mortality cycles in mangroves. Humans may tilt the balance towards higher mortality rates by introducing chronic stressors that inhibit regeneration mechanisms. MANGROVE FORESTS ARE DYNAMIC ECOSYSTEMS. Factors such as sedimentation rates, soil subsidence, freshwater run-off, tidal forces, and changes in sea level influence mangrove growth and survival. In response, mangrove species arrange themselves in zones that reflect geomorphologic and hydrologic gradients (Lugo 1980). Consequently, significant changes in environmental conditions are generally followed by alterations in the vigor or zonation of vegetation. These alterations may include widespread tree mortality.