The Tyrosinase Gene in Gorillas and the Albinism of ‘Snowflake’

The sequence of the tyrosinase (Tyr) gene coding tracts has been obtained for the gorilla (Gorilla gorilla gorilla). The five exons of the gene were sequenced in three gorillas and in a normally pigmented human. The tyrosinase gene has been found to be a very conserved locus with a very low substitution rate. Some nucleotide and amino acid differences were found between the gorilla and human tyrosinase coding sequences. One of the gorillas included in the study is the only known case of albinism in a gorilla (‘Snowflake’). Mutations of the TYR gene lead to Oculocutaneous Albinism type 1 (OCA1), the most common type of albinism in humans (OMIM accession number 203100). The TYR gene encodes the tyrosinase enzyme (E.C. 1.14.18.1), whose activity was found to be completely lacking in ‘Snowflake’, indicating that a mutation in the Tyr gene is the likely cause of his albinism. Nonetheless, no nucleotide changes were detected that could account for the lack of Tyr product or tyrosinase activity in Snowflake, and explanations of these findings are discussed.     

Decomposition of Avicennia marina on an iron‐smelting slag substrate

The present study, conducted near Newcastle, Australia, used a blocked analysis of variance experimental design to compare initial nutrient concentrations and decomposition rates of Avicennia marina (grey mangrove) grown on sand and rock blast furnace slag. There were no significant differences ( ANOVA ; P > 0.05) in mean initial nutrient concentrations of total C, N and P for plants grown on the sand and slag substrates. A litterbag technique was used to estimate decomposition rates. After 360 days of incubation, repeated measures analysis did not identify significant differences between the substrates for the interaction term ‘substrate × time’ or the term ‘substrate’ for percentage weight loss or for C, N and P remaining. Avicennia marina on both substrates had nutrient characteristics and decomposition rates comparable to those found in the literature. Results suggest that initial nutrient concentration and decomposition rates are not dramatically influenced by the presence of slag.     

Fruit misshapen in strawberry cultivars (Fragaria×ananassa) is related to achenes functionality

Fruit deformation is a phenomenon commonly observed in commercial strawberry cultivars (Fragaria×ananassa) with a negative impact on the economic benefit of crop production. To better understand this physiopathy, we evaluated fruit size and the relative amount of ‘small’ (<0.4 mm) and ‘big’ achenes (>0.6 mm) in misshapen (MF) and well‐formed (WF) fruits from ‘Camarosa’, ‘Ventana’ and ‘Medina’ strawberry cultivars growing in the field. In ‘Camarosa’, size‐dependent achenes functionality was assessed by analysing achenes germinability and differences in time to ripening between MF and WF. We found that the occurrence of fruit deformation was not only strongly dependent on the cultivar (i.e. genetic factor) but also was promoted by low temperatures (i.e. environmental factor). Regardless of the cultivar, MF showed higher percentage of ‘small’ non‐functional achenes than WF, indicating a failure in achene development, which could be related to the functional integrity of reproductive structures. To test this hypothesis, we performed an experiment by pollinating strawberry flowers with pollen developed under low and mild temperatures. Low temperatures reduced pollen viability, and flowers pollinated with low quality pollen led to a higher amount of MF. However, fruit deformation was not completely explained by differences in pollen quality, neither by differences in pistil maturity and receptivity nor ovule viability, suggesting that non‐functional achenes might result from a disruption in postfertilisation processes such as embryo abortion as a consequence of low temperatures.     

What is river health?

1. Traditionally the assessment of river water quality has been based solely on the measurement of physical, chemical and some biological characteristics. While these measurements may be efficient for regulating effluent discharges and protecting humans, they are not very useful for large-scale management of catchments or for assessing whether river ecosystems are being protected. 2. Measurements of aquatic biota, to identify structural or functional integrity of ecosystems, have recently gained acceptance for river assessment. Empirical evidence from studies of river ecosystems under stress suggests that a small group of biological ecosystem-level indicators can assess river condition. However, physical and chemical features of the environment affect these indicators, the structure and function of which may be changed by human activities. 3. The term ‘river health’, applied to the assessment of river condition, is often seen as being analogous with human health, giving many a sense of understanding. Unfortunately, the meaning of ‘river health’ remains obscure. It is not clear what aspects of river health sets of ecosystem-level indicators actually identify, nor how physical, chemical and biological characteristics may be integrated into measures rather than just observations of cause and effect. 4. Increased examination of relationships between environmental variables that affect aquatic biota, such as habitat structure, flow regime, energy sources, water quality and biotic interactions and biological condition, are required in the study of river health.     

DECOMPOSITION IN ESTUARINE ECOSYSTEMS

SUMMARY

The varied sources of estuarine plant detritus and the processes and organisms involved in its decomposition are discussed in this review. In the case of emergent and peripheral vegetation, microbial decomposition commences in the phylloplane, with fairly rapid leaching of DOM occurring soon after immersion. Residual POM, largely cellulose, is decomposed more slowly by cellulolytic micro-organisms. Phytoplankton start contributing to the DOM pool before senescence by excreting soluble substances during normal metabolism and interesting regulatory mechanisms are Involved in the bacterial utilization of this material. Bacteria play a more important role than fungi in decomposition and the latter appear to be prominent only in the breakdown of mangrove litter. Predaceous microflagellates and other protists occur in association with the bacteria and feed on them, enhancing decomposition by maintaining optimal bacterial growth rates. They appear to play a more important role in mineralization than do the bacteria, which are more effective in the conservation of nutrients upon which their efficiency of detritus incorporation Is dependent. Aerobic decomposition tends to terminate in complete mineralization, whereas under anaerobic conditions incomplete oxidation yields organic end products such as volatile fatty acids. A comparison of this process with the functioning of the herbivore rumen leads to the conclusion that the latter is more cost-effective in energy terms. Contrary to earlier published statements that estuaries are major exporters of energy in the form of detritus, many export very little of this material, or are net importers. Finally, the methods for studying decomposition in estuaries must be carefully chosen because of the environmental diversity of these systems. This is particularly true of radio-labelled substrates used for uptake and turnover studies; there appears to be no universal substrate or approach.     

Can ecosystem functional recovery be traced to decomposition and nitrogen dynamics in estuaries of the Lower Laguna Madre,Texas?

The biggest incentive to attempt the restoration and protection of estuaries is their widely acknowledged ecological and economic importance. Assessing estuary health and recovery can most accurately come from examining ecosystem processes. The purpose of this study was to explore the potential of mass loss and nitrogen (N) dynamics during leaf litter decomposition, to detect signs of functional recovery in two estuarine systems in south Texas. Submerged litterbags with black mangrove (Avicennia germinans) leaves were retrieved at various dates over 320 days. Decomposition was about 50% slower in one of the recovering systems compared to a reference site. Nitrogen immobilization and release from decaying leaf litter also discriminated among sites. Nitrogen immobilization potentials ranged from 4.15 to 6.89 mgN/g leaf litter, with the reference site exhibiting the highest value and thus the highest potential to conserve N during litter decomposition. The reference site also had a N immobilization time twice as long as the recovering sites, and a slower net release after the immobilization, appearing again as the most conservative in this part of the N cycling, possibly pointing to a less disturbed, or more stable ecosystem. Overall, the N dynamics during decomposition of mangrove leaf litter were similar in both recovering sites, whereas the reference site had a more conservative nutrient dynamics with more N being retained for longer in decomposing litter, coupled with a slower net release. Metrics derived from N dynamics may provide a finer resolution assessment of functional recovery, than only decomposition metrics.     

The Imagined Child: Ambiguity and Agency in Australian Intercountry Adoption

The adoption by Australian couples of children from ‘overseas’ involves claborate processes of bureaucratic assessment, approval and ‘parent education’. This paper explores adults' notions of ‘child’(ren) from ‘overseas’, which help shape and constitute such social processes, not only with couples seeking to adopt, but also with those cultural brokers who assess, regulate and ‘educate’ couples pursuing adoption, such as social workers and psychologists. The ways in which the adoptive ‘child’ is imagined and anticipated by counsellors and would‐be parents alike are explored through ethnographic data from South Australia. However, the proclivities of prospective adoptive parents to imagine their child‐to‐be are attenuated by certain social knowledge in relation to countries of origin. This leads to an exploration of ambiguities and tensions between the intercountry adoptive child as a tabula rasa and as a culturally and historically constituted person. The significance of ambiguities and contradictions for the child's agency and identities is highlighted, within the context of certain social policies around adoption. The chronological age of the child at the time of ‘allocation’ to its adoptive parents is considered as constituting a cultural fulcrum, upon which the identity and situational significance of the ‘origins’ of the child are deemed to subsequently turn.     

Factors regulating carbon sinks in mangrove ecosystems

Mangroves are recognized as one of the richest carbon storage systems. However, the factors regulating carbon sinks in mangrove ecosystems are still unclear, particularly in the subtropical mangroves. The biomass, production, litterfall, detrital export and decomposition of the dominant mangrove vegetation in subtropical (Kandelia obovata) and tropical (Avicennia marina) Taiwan were quantified from October 2011 to July 2014 to construct the carbon budgets. Despite the different tree species, a principal component analysis revealed the site or environmental conditions had a greater influence than the tree species on the carbon processes. For both species, the net production (NP) rates ranged from 10.86 to 27.64 Mg C ha^?1 year^?1 and were higher than the global average rate due to the high tree density. While most of the litterfall remained on the ground, a high percentage (72%–91%) of the ground litter decomposed within 1 year and fluxed out of the mangroves. However, human activities might cause a carbon flux into the mangroves and a lower NP rate. The rates of the organic carbon export and soil heterotrophic respiration were greater than the global mean values and those at other locations. Only a small percentage (3%–12%) of the NP was stored in the sediment. The carbon burial rates were much lower than the global average rate due to their faster decomposition, indicating that decomposition played a critical role in determining the burial rate in the sediment. The summation of the organic and inorganic carbon fluxes and soil heterotrophic respiration well exceeded the amount of litter decomposition, indicating an additional source of organic carbon that was unaccounted for by decomposition in the sediment. Sediment‐stable isotope analyses further suggest that the trapping of organic matter from upstream rivers or adjacent waters contributed more to the mangrove carbon sinks than the actual production of the mangrove trees.     

Bay-scale assessment of eelgrass beds using sidescan and video

The assessment of the status of eelgrass (Zostera marina) beds at the bay-scale in turbid, shallow estuaries is problematic. The bay-scale assessment (i.e., tens of km) of eelgrass beds usually involves remote sensing methods such as aerial photography or satellite imagery. These methods can fail if the water column is turbid, as is the case for many shallow estuaries on Canada’s eastern seaboard. A novel towfish package was developed for the bay-scale assessment of eelgrass beds irrespective of water column turbidity. The towfish consisted of an underwater video camera with scaling lasers, sidescan sonar and a transponder-based positioning system. The towfish was deployed along predetermined transects in three northern New Brunswick estuaries. Maps were created of eelgrass cover and health (epiphyte load) and ancillary bottom features such as benthic algal growth, bacterial mats (Beggiatoa) and oysters. All three estuaries had accumulations of material reminiscent of the oomycete Leptomitus, although it was not positively identified in our study. Tabusintac held the most extensive eelgrass beds of the best health. Cocagne had the lowest scores for eelgrass health, while Bouctouche was slightly better. The towfish method proved to be cost effective and useful for the bay-scale assessment of eelgrass beds to sub-meter precision in real time.     

Exceptionally well‐preserved vegetal remains from the Upper Cretaceous of ‘Lo Hueco’, Cuenca,Spain

Vegetal remains are considered labile structures that quickly become decayed in ecosystems. However, certain lignified tissues (woody plants) can largely resist decomposition, becoming sometimes exceptionally well preserved. At the Upper Cretaceous site of ‘Lo Hueco’ (Cuenca, Spain), those woody remains (trunks and branches) with resinous material in the inner tracheids and parenchyma cells that were buried rapidly under anoxic conditions experienced a low degree of maturation, becoming exceptionally well preserved. Those woody remains deposited under oxic conditions (sub‐aerial or sub‐aquatic exposure) were more intensely biodegraded and subsequently carbonified, partially or completely mineralized in gypsum and covered by a ferruginous crust. These two modes of preservation are scarce, with silicification or carbonification processes much more common, and both can be considered as ‘exceptional preservation’. Other vegetal remains, such as carbonified leaves, stems and roots, were collected in the site. The different modes of preservation depend directly on: depositional micro‐environment (sandy distributary channel, muddy flood plain); and type (trunk, branch, stem, leave, root) and state (presence or absence of resinous material) of the material. The great abundance and diversity of fossils in ‘Lo Hueco’ identify it as Konzentrat‐Lagerstätten, sequentially formed by alternated events of flooding and drying depositional events, but the exceptional quality and rarity of determinate vegetal macroremains preservation suggest that certain deposits of this site can be considered as conservation deposits.     

Soil‐surface CO2 efflux and its spatial and temporal variations in a young ponderosa pine plantation in northern California

Soil‐surface CO₂ efflux and its spatial and temporal variations were examined in an 8‐y‐old ponderosa pine plantation in the Sierra Nevada Mountains in California from June 1998 to August 1999. Continuous measurements of soil CO₂ efflux, soil temperatures and moisture were conducted on two 20 × 20 m sampling plots. Microbial biomass, fine root biomass, and the physical and chemical properties of the soil were also measured at each of the 18 sampling locations on the plots. It was found that the mean soil CO₂ efflux in the plantation was 4.43 µmol m^?2 s^?1 in the growing season and 3.12 µmol m^?2 s^?1 in the nongrowing season. These values are in the upper part of the range of published soil‐surface CO₂ efflux data. The annual maximum and minimum CO₂ efflux were 5.87 and 1.67 µmol m^?2 s^?1, respectively, with the maximum occurring between the end of May and early June and the minimum in December. The diurnal fluctuation of CO₂ efflux was relatively small (< 20%) with the minimum appearing around 09.00 hours and the maximum around 14.00 hours. Using daytime measurements of soil CO₂ efflux tends to overestimate the daily mean soil CO₂ efflux by 4–6%. The measurements taken between 09.00 and 11.00 hours (local time) seem to better represent the daily mean with a reduced sampling error of 0.9–1.5%. The spatial variation of soil CO₂ efflux among the 18 sampling points was high, with a coefficient of variation of approximately 30%. Most (84%) of the spatial variation was explained by fine root biomass, microbial biomass, and soil physical and chemical properties. Although soil temperature and moisture explained most of the temporal variations (76–95%) of soil CO₂ efflux, the two variables together explained less than 34% of the spatial variation. Microbial biomass, fine root biomass, soil nitrogen content, organic matter content, and magnesium content were significantly and positively correlated with soil CO₂ efflux, whereas bulk density and pH value were negatively correlated with CO₂ efflux. The relationship between soil CO₂ efflux and soil temperature was significantly controlled by soil moisture with a Q₁₀ value of 1.4 when soil moisture was <14% and 1.8 when soil moisture was >14%. Understanding the spatial and temporal variations is essential to accurately assessment of carbon budget at whole ecosystem and landscape scales. Thus, this study bears important implications for the study of large‐scale ecosystem dynamics, particularly in response to climatic variations and management regimes.     

Sensitivity of the Welfare Quality® broiler chicken protocol to differences between intensively reared indoor flocks: which factors explain overall classification?

There is a large demand for holistic welfare assessment systems that result in a singular balanced summary of welfare. The Welfare Quality® (WQ) broiler protocol summarizes 18 welfare measures into four principles (‘good feeding’, ‘good housing’, ‘good health’ and ‘appropriate behaviour’), which are then integrated into one overall category (‘excellent’, ‘enhanced’, ‘acceptable’ or ‘not classified’). But the protocol is time consuming which hampers implementation. Furthermore, WQ’s aim to assess animal welfare in a wide range of husbandry systems may decrease its ability to discriminate between flocks from the same system. We applied the protocol in the context of intensive indoor rearing to assess whether it discriminated sufficiently between flocks, could be shortened without losing essential information, and provided a balanced summary of welfare. The vast majority of the flocks (88%) received the same overall classification (acceptable) whilst all other flocks received an adjacent classification (enhanced), suggesting poor discriminative capacity. For 95% of the flocks overall classification was explained by two measures only (‘drinker space’ and ‘stocking density’). A system based on these two measures would reduce assessment time from 3.5 h to a few minutes. However, both measures’ validity can be questioned as they are risk factors for poor welfare rather than animal-based outcome measures and they suffer from methodological weaknesses. Furthermore, the possibility for such an extreme simplification raises doubts on whether the overall classification reflects a balanced summary of different welfare aspects. In line with this, overall classification was not affected by replacing single measures within the ‘good health’ and ‘appropriate behaviour’ principles with realistically attainable minima or maxima for intensively reared flocks. Even replacing either of these two principles entirely with their realistically obtainable minimum or maximum did not affect classification. Such insensitivity to change may discourage attempts to improve the welfare of intensively reared flocks when assessments are made based on the overall classification. This calls for an adjustment of the classification system, which is currently being developed by the Welfare Quality Network.     

Geomorphology of Australian estuaries: Review and prospect

Over the past 30 years there has been a wealth of research examining the geomorphology of Australian estuaries. This paper reviews the major regional controls on estuarine geomorphic development and discusses the focus of research efforts to understand estuarine evolution, configuration and processes controlling geomorphic development and change. The presence and position of estuaries along the Australian coastline is controlled by large-scale climate-led changes in sea-level, the antecedent structure of the coast and tectonic activity. The configuration of Australia’s estuaries is controlled by a number of environmental factors identified by 34 including climate, oceanographic regime, sediment availability, structure and mineralogy, and tectonics. Interaction of these factors produce a range of estuarine configurations around the Australian continent from wave-dominated, microtidal, bar-built estuaries in the south to low energy macrotidal estuaries in the north which have produced extensive low-lying coastal plains. The principle focus of geomorphologists during the past 30 years has been understanding the medium to long-term development of estuaries in response to fluctuating sea-level over the past 125 000 years. Classifications and models of estuarine development and associated biological community response to estuary development have been identified based on lateral and vertical sedimentary sequences. Results have provided essential information on the physical resources and characteristics of estuarine systems including the distribution of sediment facies that host a variety of different ecological communities. There has been a paucity of research examining contemporary processes controlling geomorphic change in Australia’s estuaries. A morphodynamic approach to the study of estuaries is advocated that evaluates morphology-process responses as estuaries evolve. This approach requires increased research efforts to identify regional differences in estuarine geomorphic development, hydrodynamic processes and sedimentation. It is also advocated that studies examine how the morphodynamic behaviour of estuaries over thousands of years has influenced estuary ecology. Such studies will provide a more complete understanding of the factors influencing the morphology and ecology of contemporary estuaries.     

Origins of mangrove ecosystems and the mangrove biodiversity anomaly

1. Mangrove species richness declines dramatically from a maximum in the Indo-West Pacific (IWP) to a minimum in the Caribbean and Western Atlantic. Explaining this ‘anomalous’ biogeographic pattern has been a focus of discussion for most of this century. 2. Two hypotheses have been put forward to explain the mangrove biodiversity anomaly. The ‘centre-of-origin hypothesis’ asserts that all mangrove taxa originated in the IWP and subsequently dispersed to other parts of the world. The ‘vicariance hypothesis’ asserts that mangrove taxa evolved around the Tethys Sea during the Late Cretaceous, and regional species diversity resulted from in situ diversification after continental drift. 3. Five lines of evidence are used to test between these two hypotheses. First, we review the mangrove fossil record. Second, we compare modern and fossil distributions of mangroves and eight genera of gastropods that show high fidelity to the mangrove environment. Third, we describe species-area relationships of mangroves and associated gastropods with respect to area of available habitat. Fourth, we analyse patterns of nestedness of individual plant and gastropod communities in mangrove forests. Fifth, we analyse patterns of nestedness of individual plant and gastropod species. 4. All five lines of evidence support the vicariance hypothesis. The first occurrences in the fossil record of most mangrove genera and many genera of gastropods associated with mangrove forests appear around the Tethys Sea from the Late Cretaceous through the Early Tertiary. Globally, species richness in any given mangrove forest is tightly correlated with available area. Patterns of nestedness at the community and species-level both point towards three independent regions of diversification of mangrove ecosystems: South-east Asia, the Caribbean and Eastern Pacific, and the Indian Ocean region.     

Long-term ecological vulnerability assessment of Indian Sundarban region under present and future climatic conditions under CMIP6 model

Vulnerability assessment of ecosystem bestows an idea about the ecosystem health and its ability to resist environmental stress. Indian Sundarban region situated at the southwest part of Ganga-Brahmaputra-Meghna delta has been under constant threat of frequent climate hazards and long-term climate change. Various attempts have been made for vulnerability assessment of this mangrove ecosystem focusing only on static non-temporal variables. The present work hypothesises that mangrove ecosystems are highly adaptive and respond to the changing environment by various natural resilience strategies at the ecosystem level. So, a better understanding of the dynamics of mangrove ecosystem will provide an idea about the state of vulnerability for this ecosystem. The present study uses 16 parameters to create exposure, sensitivity and adaptive capacity risk indices and constructs the vulnerability status for the Indian Sundarban. The results showed that the sea-level rise will happen between 0.7 m to 0.9 m under baseline climate conditions. The CMIP6 multi-model ensemble showed that the future minimum temperature for the region will go up to 29.48 °C, thereby reducing the max and min temperature difference for the region. The fuzzy AHP-based vulnerability assessment revealed that the western Sundarban is more prone to climate vulnerability. The island-like Surendranagar, Lothian, and West-Ajmalmari are extremely vulnerable. The proximity to human habitat will play an important role in climate change sensitivity to the Sundarban region. The time series analysis of mangrove forests showed the Mann-Kendall ‘τ’ value varies between 0.82 to −0.83. The central Sundarban forests area shows a varying degree of forest health deterioration. The assessments from the present study and the maps will help the environmental and risk-managers to identify the regions needing more climate change adaptation strategy.     

Mangroves of Oman during the late Holocene; climatic implications and impact on human settlements

Pollen and micropalaeontological analyses carried out on mangrove swamp sediments of Suwayh, Oman (22°05.589'N, 50°40.033'E) reveal environmental changes linked both to climate (monsoon) and geomorphological (sea-level) variations during the Late Holocene. A Rhizophora mangrove developed at Suwayh around 6000 years B. P. under climate conditions marked by an increased tropical influence as compared to the modern situation, with dominant summer rains. The later extension of Prosopis cineraria at Suwayh provides evidence for a different rainfall pattern, with a winter rainy season. Pollen and micropalaeontological composition shows three episodes influenced by the sea water at Suwayh. The most important corresponded to the mangrove episode centred ca 6000 B. P. This was followed by two episodes of slight seawater incursion at ca. 5100 and 4500 B. P. responsible for the formation of a brackish laagon. Comparison based on ¹⁴C measurements on shell recovered from both the sedimentary sequence of Suwayh and the nearby archaeological sites demonstrates that close relations existed between man and mangroves during the Neolithic and the Early Bronze Age. Received October 31, 2001 / Accepted January 24, 2002 Correspondence to: Anne-Marie Lézine     

Genetic influences on ‘environmental’ factors

Childhood environment, social environment and behavior, leisure time activities and life events have been hypothesized to contribute to individual differences in cognitive abilities and physical and emotional well‐being. These factors are often labeled ‘environmental’, suggesting they shape but not reflect individual differences in behavior. The aim of this study is to test the hypothesis that these factors are not randomly distributed across the population but reflect heritable individual differences. Self‐report data on Childhood Environment, Social Environment and Behavior, Leisure Time Activities and Life Events were obtained from 560 adult twins and siblings (mean age 47.11 years). Results clearly show considerable genetic influences on these factors with mean broad heritability of 0.49 (0.00–0.87). This suggests that what we think of as measures of ‘environment’ are better described as external factors that might be partly under genetic control. Understanding causes of individual differences in external factors may aid in clarifying the intricate nature between genetic and environmental influences on complex traits.     

An overview of river health assessment: philosophies, practice, problems and prognosis

1. Philosophically, the term ‘river health’ is useful because it is readily interpreted by the general public and evokes societal concern about human impacts on rivers. The common goal of achieving healthy rivers unites ecologists and the general public because the value of the ecologists’ contributions is clear (and, hence, funded). The difficulty arises in the choice of relevant symptoms because there is a wide variety that can be measured with varying accuracy at a broad range of spatial scales. These indicators may respond to impacts at different time scales, and no single indicator is a ‘silver bullet’ that reveals river health unequivocally. 2. In practice, choice of indicator often shows personal bias, technical considerations, and constraints of knowledge. Selection of appropriate spatial and temporal scales for these measures is crucial. Although most measurements are spot samples (e.g. concentration, abundance, species richness), assessment of river health based on changes in ecological processes such as post-disturbance recovery rate or nutrient spiralling lengths may be more suitable in some cases. 3. Problems include validation of the indicator, its response time at a range of scales, and the reliability of its measurement. Assessment of river health should be accurate, timely (warning of deterioration instead of waiting until the patient is terminal), rapid (so that the response is swift), and inexpensive. The connectedness of running waters with their floodplains and catchments must be explicitly recognized. Hydrological and geomorphological modifications of rivers usually affect their health by severing or impairing the linkages, and the ‘cure’ may lie in addressing these causes. Often, we need landscape-level data for management because this is the scale where cumulative effects of impacts are evident. 4. The prognosis is uncertain. We need to explore further the use of integrative measures of river health, and focus on establishing a link between the measure and impaired ecological integrity. Ecosystem-level variables (e.g. estimates of production or respiration) show promise and recent technological advances make these more accessible. Data analytical approaches (e.g. multimetric vs. predictive models) need further debate but must not overlook the importance of high quality and relevant input data. Appropriate choice of indicators, rigorous sampling and analysis, and careful data interpretation must be matched with effective communication to policy-makers and the public. When this occurs, the concept of ‘river health’ becomes more than just a rhetorical tool.‘     

Mangrove associates versus true mangroves: a comparative analysis of leaf litter decomposition in Sundarban

Mangrove species are broadly classified as ‘true mangroves’ and ‘mangrove associates’. We hypothesized that the leaf litter decomposition rates of true mangroves differ significantly from the mangrove associates under the same ecological and bio-climatic conditions. In order to test this hypothesis, the leaf litter decay rates of 24 true mangrove species and 10 mangrove associates along with the concomitant carbon and nitrogen dynamics of the litters were studied in the tropical mangrove forest of Sundarban by means of litter bags. The decomposition was monitored for six consecutive weeks in the pre-monsoon, monsoon and post-monsoon season. All the species in general went through a rapid decay phase in the first 2 weeks, however, the rate substantially decreased in the following 4 weeks. Most of the species studied had significant seasonal variability (p < 0.05) in the decay rate. Species-specific decay was highest throughout the monsoon and least during the post-monsoon season. The mean dry weight composition (i.e. percentage of dry weight of the leaf litters remaining at the end of weekly intervals) of the true mangroves was 10–12 % higher than the mangrove associates throughout the sampling period. The mean decay constants (K in week^?1) of the true mangroves were 0.15 ± 0.05, 0.20 ± 0.06 and 0.16 ± 0.05 in the pre-monsoon, monsoon and post-monsoon season respectively. The mangrove associates had significantly higher decay constants in the respective seasons that followed the order 0.23 ± 0.09, 0.25 ± 0.06 and 0.24 ± 0.09. As a consequence, the computed mean half-life period of the true mangrove litters (32 ± 11 days) was much higher than the mangrove associates (23 ± 11 days). This showed that collectively the leaf litters of mangrove associates degraded at a much faster rate than the true mangroves throughout the annual cycle and thus our hypothesis was justified.