Photosynthetic and growth responses of Japanese sasabamo (Potamogeton wrightii Morong) under different photoperiods and nutrient conditions

Controlled laboratory experiments were conducted to examine how photosynthesis and growth occur in Potamogeton wrightii Morong under different photoperiods and nutrient conditions. The experiment was based on a 3×2 factorial design with three photoperiods (16, 12 and 8 h) of 200 μE · m^?2·s^?1 irradiance and two nutrient conditions, high (90 μmol N · L^?1·d^?1 and 9 μmol P · L^?1·d^?1) and low (30 μmol N L^?1·d^?1 and 3 μmol P · L^?1·d^?1). After 14, 28, 56 and 70 days of growth, plants were harvested to determine net photosynthesis rate and various growth parameters. Above- and below-ground biomass were investigated on days 56 and 70 only. Plants under low nutrient conditions had greater leaf area, more chlorophyll a, a higher rate of net photosynthesis and accumulated more above- and below-ground biomass than plants in the high nutrient condition. Plants with an 8 h photoperiod in the low nutrient condition had a significantly higher rate of net photosynthesis, whereas 8 h photoperiod plants in the high nutrient condition had a lower rate of net photosynthesis and their photosynthetic capacity collapsed on day 70. We conclude that P. wrightii has the photosynthetic plasticity to overcome the effects of a shorter photoperiod under a tolerable nutrient state.     

Combination system of full-scale constructed wetlands and wetland paddy fields to remove nitrogen and phosphorus from rural unregulated non-point sources

Constructed wetlands (CWs) have been used effectively to remove nitrogen (N) and phosphorus (P) from non-point sources. Effluents of some CWs were, however, still with high N and P concentrations and remained to be pollution sources. Widely distributed paddy fields can be exploited to alleviate this concern. We were the first to investigate a combination system of three-level CWs with wetland paddy fields in a full scale to remove N and P from rural unregulated non-point sources. The removal efficiencies (REs) of CWs reached 57.3 % (37.4–75.1 %) for N and 76.3 % (62.0–98.4 %) for P. The CWs retained about 1,278 kg N ha^?1 year^?1 and 121 kg P ha^?1 year^?1. There was a notable seasonal change in REs of N and P, and the REs were different in different processing components of CWs. The removal rates of wetland paddy fields adopt “zero-drainage” water management according to local rainfall forecast and physiological water demand of crop growth reached 93.2 kg N ha^?1 year^?1 and 5.4 kg P ha^?1 year^?1. The rice season had higher potential in removing N and P than that in the wheat season. The whole combined system (0.56 ha CWs and 5.5 ha wetland paddy fields) removed 1,790 kg N year^?1 and 151 kg P year^?1, which were higher than those from CWs functioned alone. However, another 4.7-ha paddy fields were needed to fully remove the N and P in the effluents of CWs. The combination of CWs and paddy fields proved to be a more efficient nutrient removal system.     

Predicting the spatial distribution of mangroves in a South African estuary in response to sea level rise,substrate elevation change and a sea storm event

The spatial distribution of mangroves in the Mngazana Estuary under sea level rise induced by climate change, together with different substrate elevation change scenarios was predicted for 2020, 2050 and 2100. The present inundation frequency tolerance range was from 0.8 to 31.2 %, equivalent to substrate elevation thresholds of 1.1 and 1.7 m amsl. These thresholds were measured by field surveys and analysis of a gauge station situated near the mouth of the estuary. The predictions were based on the assumption that the inundation frequency tolerance range of mangrove stands remains constant in the future. Through the use of a digital elevation model an initial increase of 2.10 ha year^?1 was found in mangrove area between present and 2020 (from 122.6 to 143.6 ha). This was due to habitat becoming available that is currently too compacted for seedling establishment to occur. This compaction resulted from human and cattle traffic for grazing. Thereafter there would be a mean loss of 0.66 ha year^?1 from 2020 through 2100. Landward migration of mangroves would not take place due to the elevation limit of adjacent non-mangrove areas. In addition, the loss rate would increase to 1.01 ha year^?1 under insufficient sediment accretion, but would decrease to 0.18 ha year^?1 under thriving mangroves condition. The analysis of sea storm event in September 2008 showed that local water level increased by 28 cm and maximum affected area was 87.0 ha (about 71 % of mangrove stands). The inundation continued over 5 days. The results indicated that the combination impact of sea level rise, substrate elevation change and sea storm would possibly be a threat to tropical African estuaries with large flat intertidal areas and mangroves.     

Biomass and carbon budgeting of sustainable agroforestry systems as ecosystem service in Indian Himalayas

Adoption of agroforestry is paramount as a climate change mitigation and adaptation strategy. The assessment of plant biomass is crucial for understanding the vulnerability of biological systems to climate change. In the present study, agroforestry systems viz., agrisilviculture (AS), agrihorticulture (AH), agrihortisilviculture (AHS) and agrisilvihorticulture (ASH) were investigated for biomass production and carbon stock in vegetation as well as in soil in the Indian central Himalaya along the elevation i.e. E₁ (<1100 m), E₂ (1100–1400 m), E₃ (1400–1700 m), E₄ (1700–2000 m) and E₅ (>2000 m). Mean aboveground and belowground biomass were 73.9% and 26.1%, respectively, of total biomass (64.4 t ha^?1) in agroforestry systems. Fodder and/or timber trees accounted for 31% (in AHS) to 74% (in AS) of total biomass, while fruit trees accounted for 18% (in ASH) to 73% (in AH) of total biomass. The contribution of agriculture crops to total biomass fluctuated between 19% (in ASH) and 26% (in AH). Total vegetation biomass, soil carbon and total carbon density in agroforestry systems increased significantly along the elevation, with maximum biomass at elevation E₅ (32.0 t ha^?1, 64.7 t C ha^?1 and 96.7 t C ha^?1). Total biomass of vegetation among agroforestry systems differed significantly. Soil carbon stock was highest in AHS (59.5 t C ha^?1) and total carbon density (vegetation + soil) was highest in ASH (93.0 t C ha^?1). Thus, in Indian Himalayas, vegetation biomass, carbon stock, soil and total carbon (vegetation + soil) stock increased along the elevation.

Abbrviations: AG: aboveground; BG: belowground; WD: wood density; VOB: volume over bark; BEF: biomass expansion factor; AS: agrisilviculture; AH: agrihorticulture; ASH: agrisilvihorticulture; AHS: agrihortisilviculture; E: elevation; C: carbon; CO₂: carbon-di-oxide; IPCC: Intergovernmental Panel on Climate Change; DBH: diameter at breast height; AGBD: aboveground biomass density; BGBD: belowground biomass density; GSVD: growing stock volume density     

Positive relationships between phenol oxidase activity and extractable phenolics in estuarine soils

Decomposition of recalcitrant materials such as phenolics is known to play a pivotal role in organic matter decomposition and nutrient cycling in estuaries. The specific goals of this study were to determine temporal and spatial variations of phenol oxidase and phenolics in estuarine soils, and to elucidate controlling factors for phenol oxidase activity. To achieve these goals, phenol oxidase activity and phenolic content were measured in soils developed along the side of an estuary in the Han River, Korea. Soil samples were collected in three locations with different vegetation: mud flats, Zizania-dominated soils, and Salix-dominated soils. Monthly measurements were also made in a Zizania-dominated site over a year period. Phenol oxidase activity varied between 0.00 and 0.28 diqc min^?1 g^?1, whilst phenolic content ranged from 0.0–10.5 μg g^?1. A correlation analysis revealed that phenol oxidase activity exhibited positive correlations with phenolic content in both seasonal and spatial data. The same relationship was found when the data were analysed separately for each site. Unlike peatlands or upland forest soils where negative correlations were often found between phenol oxidase activity and phenolics, substrate induction appears to account for the positive correlation in the present study.     

Sedimentary records of anthropogenic contribution to heavy metal content in Oum Er Bia estuary (Morocco)

Levels of heavy metals (Cd, Hg, Cr, Cu, Fe, Mn, Ni, Pb and Zn), organic carbon content and textural characteristics in the superficial and cored sediments of Oum Er Bia estuary have been studied. The anthropogenic fluxes of heavy metals were determined in two sediment cores collected in the estuary, facing urban sewages. A dated estuarine core from the inter-tidal area was assessed using ²¹⁰Pb and ¹³⁷Cs data. These data indicate that the mean sedimentation rates are 0.38–68 cm year^?1. The analytical results and the radio-dating of sediment cores show extremely high concentrations of Zn, Pb and Cu in the sediments that can be ascribed mostly to the discharge of the liquid effluent from the sewage since the late 1960s, decreasing towards the present day. The pollution intensity of the estuary is determined by the enrichment factors, which show that the Oum Er Bia estuary is moderately polluted to polluted.     

Lights and shadows: growth patterns in three sympatric and congeneric sponges (Ircinia spp.) with contrasting abundances of photosymbionts

The life-history traits of long-lived benthic littoral invertebrates remain poorly understood. In this study, we analysed patterns of growth in three abundant sublittoral sponges from the western Mediterranean Sea, chosen for their close phylogenetic relatedness, sympatric distribution, and contrasting amounts of photosymbionts: high in Ircinia fasciculata, lower in I. variabilis, and absent in I. oros. Sponge area, perimeter, number of oscula, and epibiont abundance were quantified from in situ digital images taken monthly for 1.5 years and volumetric growth rates were calculated from empirical area–volume relationships. Volumetric growth rates were different among species and coherent with the photosymbiont abundance: high in I. fasciculata (40.03 ± 4.81 % year^?1, mean ± SE), low in I. variabilis (5.65 ± 6.11 % year^?1), and almost nil in I. oros (?0.04 ± 3.02 % year^?1). Furthermore, a marked seasonality was observed in the first two species, with greater growth during the warm season. The high growth rates of I. fasciculata were likely fuelled by symbiont-derived photosynthates and required to compete in the well-lit, algal-dominated habitats this species prefers. In contrast, I. variabilis and I. oros tended to dwell in shaded habitats, where competition from slow-growing invertebrates is intense, and featured lower growth rates. The flattened morphology and lower circularity of I. variabilis indicates a capacity for adaptation to any space that is freed, while I. oros had less oscula and was more massive and circular, suggesting a strategy of passive occupation and minimisation of biological interactions. The results show that even congeneric species living sympatrically can achieve important biomass using different growth and substrate occupation strategies.     

Estimation and validation of biomass of a mountainous agroecosystem by means of sampling,spectral data and QuickBird satellite image

Biomass estimation in agroecosystems (AESs) is important to understand their role in carbon exchange for a sustainable environment. We used field spectra and sampled biomass of an AES including cultivated and abandoned croplands to develop a simple biomass estimation model. The digital number (DN) of a QuickBird (QB) satellite image was converted to a reflectance factor using the dark object subtraction method and the spectral reflectance of asphalt. The relationship between the reflectance factor of field-based spectra and the QB image obtained in early July 2007 was insignificant in the blue (R ² = 0.15) and green (R ² = 0.18) bands but was significant (p < 0.05) in the red (R ² = 0.57) and near-infrared (NIR, R ² = 0.45) bands in the AES. Better correlations were obtained between field-based and QB-based vegetation indices (VIs). The best correlations were obtained with the normalized difference vegetation index (NDVI) (R ² = 0.97, p < 0.001) and the ratio vegetation index (RVI) (R ² = 0.99, p < 0.001). Biomass was significantly correlated with both field-based NDVI and RVI (R ² = 0.79 and 0.72, respectively, p < 0.001). Although RVI saturated at higher biomass densities (>600 g m^?2), NDVI showed a linear relationship. Other field-based VIs showed poorer correlations with biomass. The model was evaluated by incorporating it into high-resolution QB images to obtain the observed biomass. The relationship between field-estimated and QB-observed biomass appeared to be a one-to-one linear relationship (R ² = 0.79). Thus, models using field spectra and sampled biomass can be applied to QB images for remote estimation of biomass in an AES.     

Seasonal variations in physicochemical characteristics and cyanobacterial diversity of a lake in Northern India

Physicochemical analyses and cyanobacterial diversity of Ramgarh Lake water were performed at five sampling sites during winter, summer, and monsoon seasons. Higher load of solids, carbon, and nutrients were persistent throughout the analysis that indicates the conversion of lake from oligotrophic to eutrophic nature. High nutrients load enhanced cyanobacterial biomass, while low nutrients load produced relatively less biomass. The physicochemical parameters of water samples revealed minimum 2.9 mg L^?1 dissolved oxygen (DO) at site-1 during summer, while maximum (5.6 mg L^?1) at site-4 in monsoon season. Maximum biochemical oxygen demand (BOD) (40 mg L^?1) and chemical oxygen demand (COD) (126 mg L^?1) were recorded at site-1 during summer, whereas minimum BOD (18 mg L^?1) and COD (52 mg L^?1) were evident at site-3 in monsoon season. Minimum concentration of nitrate (0.72 mg L^?1) was recorded at site-3 in summer, whereas maximum 2.7 mg L^?1 was present at site-5 in winter season. The phosphate concentration was maximum (0.52 mg L^?1) at site-5 in summer, and minimum (0.18 mg L^?1) was observed at site-4 in monsoon season. Cyanobacterial diversity was higher during all the seasons, and dominated by the species of Microcystis at all the five sampling sites.     

Effects of zinc stress on growth and antioxidant enzyme responses of Kandelia obovata seedlings

This study evaluated the tolerance and accumulation potential in the mangrove Kandelia obovata under moderate and high levels of external Zn. A greenhouse experiment was conducted to investigate the effects of a range of external Zn concentrations (0–400 mg L^?1) on the growth of this species by counting the lateral root number and measuring the root length, leaf area, and total dry biomass. We also determined the Zn accumulation in plant tissues. K. obovata survived with external Zn concentrations of up to 400 mg L^?1, although the excess metal resulted in a biomass reduction of 34%. A significant increase in antioxidant enzyme activities occurred in roots of plants under high-level Zn stress, suggesting that K. obovata seedlings could tolerate up to 200 mg L^?1 zinc treatment.     

Morphological plasticity of submerged macrophyte Potamogeton wrightii Morong under different photoperiods and nutrient conditions

The morphological plasticity of the submerged macrophyte Potamogeton wrightii under different nutrient conditions and photoperiods was measured in a laboratory controlled experiment for 70 days in Japan. Six treatments were used in this experiment (3 × 2 factorial design with three replications) which consisted of three photoperiods and two nutrient conditions. Both photoperiod and nutrient condition had a pronounced effect on shoot and leaf morphology in P. wrightii. New shoot recruitment, and the length of main and new shoots gradually decreased with shortening photoperiod under both nutrient treatments. Plants under an 8 h photoperiod and high nutrient levels generated significantly more dead leaves (7.42 leaf·shoot^?1) and decomposed shoots (1.3 shoots·pot^?1) than plants under other treatments. Under short photoperiods (12 and 8 h) plants failed to produce flowering spikes in both nutrient conditions. In high nutrient conditions, P. wrightii produced shorter shoots, fewer leaves with shorter and narrower laminas, and smaller petioles compared with plants in the low nutrient condition. This may be adaptive under high nutrient conditions because it lowers foliar uptake and, thus, nutrient toxicity.     

Important organic matter sources and trophic pathways for the nutrition of Hilsa kelee (Cuvier, 1829) and Valamugil buchanani (Bleeker, 1853) in Pangani macro-tidal estuary,Tanzania

The study investigated the spatial variation in the main sources of organic matter (OM) and trophic pathways for zooplanktivorous Hilsa kelee and phytodetritivorous Valamugil buchanani in fresh-water-influenced zone versus sea-water-dominated zone of Pangani estuary. The findings indicated significant inter-specific variations in δ¹³C and δ¹⁵N values (ANOVA, F?≥?84.3, p?F?≥?9.4, p?=?0.001) in both estuarine zones. Results also showed significant zonal-intraspecific variations in stable isotopes (δ¹³C and δ¹⁵N), FA profile and marginal differences in diet for the V. buchanani while no considerable differences were observed for H. kelee from two estuarine zones. The isotope mixing models and FA biomarkers revealed that the most important carbon sources to the nutrition of H. kelee were derived from microphytobenthos, macro-algae and sea grasses transferred through phytoplankton and detrital trophic pathways. In contrast, C₃ terrestrial plants and microphytobenthos were the main carbon source to the diet of V. buchanani; and were transferred via the benthic and detrital trophic pathways. Therefore, both terrestrial and in-situ OM sources were the main trophic resources base fuelling the planktonic and benthic food webs in Pangani estuary.     

Nitrogen limitation in the coastal heath at Anholt,Denmark

The purpose of the study was to investigate, whether the coastal grey dune vegetation at Anholt, Denmark, is limited by nitrogen or phosphorus. The island Anholt (22,37 km²) is situated in the centre of Kattegat A two factor fertilization experiment with nitrogen as NH₄NO₃ (N-addition) and phosphorus as KH₂PO₄ (P-addition) was carried out in the coastal grey dune vegetation of Anholt. The N-addition corresponded to 40 kg N ha^?1 year^?1 and the P-addition to 7 kg P ha^?1 year^?1 The experiment included N-, P-, N + P-addition and control. Lichens (genera: mainly Cladonia, Stereocaulon, Cetraria, Hypogymnia) and bryophytes (genera: Polytrichum, Racomitrium) cover most of the surface. Only two plant species, Corynephorus canescens and Empetrum nigrum, constitute nearly all vascular plant cover and biomass of this calcium poor coastal heath community. Corynephorus and Empetrum increased their cover significantly following N and N + P addition. No effect was observed by P addition alone. N limitation of this coastal heath vegetation remote from agricultural and industrial activities was evident. The effect on the plant species of the single application was short-lived. After two-three years of enhanced cover, the Corynephorus and Empetrum cover had returned to their level before the experiment. The lichen vegetation, however, changed more permanently, and after 12 years the subplots with N + P addition was dominated by rich growth of Cladina and Cetraria species. The results are discussed in relation to anthropogenic nitrogen deposition and conservation of this high priority ecosystem.     

The Influence of Varying Algal Biomass On Contaminant Exposure in Benthic-Planktonic Mesocosms: Copper (Ii)

Abstract

A series of mesocosms was exposed to a suite of light treatments and nutrient enrichment in order to generate algal communities of varying biomass. the influence of this biomass on the speciation of copper (II) was studied. Distribution coefficients ( _Kd,Lkg?1) were relatively high (log _Kd = 5 to 7), indicative of robust trace metal sequestration, and were likely controlled by the particulate organic carbon content (foc). Differences in _Kd over time and among treatments were significant, as was the relationship between _Kd and foc. Fluorescence quenching was used to determine binding capacities ( _Lt , M) and their associated binding constants ( _Kcond ,M^?1) in order to model the solid phase copper speciation. the _Kcond ranged between 2.1 and 5.2 × 10¹²M^?1, indicating a very strong copper-ligand complex, and was higher in mesocosms that received more light. the light _Lt increased over time, dramatically after the nutrient enrichment, but did not vary systematically among light treatments. _Lt ranged from 7.2 × 10? 7 to 4.9 × 10? 5 M. the large magnitudes of _Kd , _Kcond and _Lt ensured that greater than 97% of total copper in the mesocosms was complexed by organic matter. the total copper concentration ([Cu]_T, M) needed to reach a target dissolved copper concentration of 10^?12.5 M (pCu = 12.5) was determined for each mesocosm over time. [Cu]_T was between 8.02 × 10^?5 and 3.41 × 10^?2 M, and increased over time. the [Cu]_T normalized to the target pCu (Effective Dose Ratio, EDR) increased directly with increases in algal biomass, indicating a direct link between system productivity and copper exposure. Approximately 45% of the variance in EDR was explained by variance in total biomass, while the residual variance in EDR was due likely to differences in the strengths of particle associations and magnitude of binding capacities.     

Phytotoxicity assessment of phenanthrene and pyrene in soil using two barley genotypes

This study investigated the toxicity extent of phenanthrene and pyrene to two cultivars (CM-72 and Gairdner) of barley (Hordeum vulgare). Germination of barley seeds was evaluated in 69-d aged soil, separately spiked with phenanthrene at extractable concentrations of 0.95, 6.3, 59, and 300 mg kg^?1 (dry soil) and pyrene at 1.0, 9.0, 73, and 400 mg kg^?1 (dry soil). Although germination was not inhibited, significant (P < 0.05) reduction in root and shoot length occurred at concentrations of phenanthrene ≥6.3 mg kg^?1 and pyrene ≥9.0 mg kg^?1 after both 72 and 240 h. Fresh and dry biomass of both cultivars reduced with increasing concentrations of both polycyclic aromatic hydrocarbons (PAHs). Barley cultivar CM-72 was more sensitive than Gairdner, and it can be considered suitable for toxicity assessment of PAH-contaminated soils.     

Benthic vegetation,chlorophyllα and physical-chemical variables in a protected zone of a Mediterranean coastal lagoon (Lesina,Italy)

Phytoplankton and benthic vegetation biomass undergoes spatial-temporal changes in relation to their life cycle, but also to meteorological conditions, physical-chemical variables, organic input and internal dynamism. The main aim of this work was to observe the effect of all environmental variables on the vegetative dynamic process in a protected zone of a Mediterranean costal lagoon (Lesina lagoon, SE Italy). Seven samplings were performed from 2010 to 2012 at 30 sites for nutrient and chlorophyll analyses, while TOC measurements and wet biomass evaluation were performed at 10 sites. Temperature, salinity and oxygen saturation were also measured by multiparametric probe and a visual census for vegetation was performed. Sites close to freshwater inflow were characterized by lower temperature and salinity, and high nitrate, with maxima of 191.05 μM in May 2010 and more than 250 μM in October 2010. Silicates drastically decreased from May 2010 (87.57 μM) to July 2010 (6.15 μM) and increased again in October (74.99 μM). Chl a concentrations were not on average higher than 6 mg m^?3, but peaks of 20 mg m^?3 were observed during May 2011 and May 2012. Benthic vegetation wet biomass collected in 2010 was approximately twice that collected in 2012, with a maximum of 27,554 g m^?2 and a dominance of macroalgae (70 % in May 2010 and 40 % in August 2010). During period 2010, a simultaneous and drastic decreasing of both mean values of wet biomass and chl a was observed from May to October 2010. During period 2012 a shift of vegetation biomass was shown from May (phytoplankton prevalence) to August 2012, with angiosperm prevalence (more than 30 %).     

New estimates of microalgae production based upon nitrate reductions under sea ice in Canadian shelf seas and the Canada Basin of the Arctic Ocean

New estimates of production of sub-ice and ice microalgae in the shelf seas of the Canadian Arctic and in the Canada Basin of the Arctic Ocean derived from reduction of nitrates in the water column, as recorded in time series available in publicly held data bases, suggest that it is of greater magnitude (up to 30 g C m^?2 year^?1) and represent a higher proportion (up to 50 % on the shelf and 90 % in the Canada Basin) of net community production than previously estimated for both areas.     

Age and growth rates of Hawaiian hawksbill turtles (Eretmochelys imbricata) using skeletochronology

The Hawaiian hawksbill population has fewer than 20 females nesting per year; hence, there is a need to monitor this population closely and basic biological information on individual growth and age to maturity is critical. We present a skeletochronology analysis of Hawaiian hawksbills using humeri recovered from 30 dead stranded hawksbills, plus 10 dead hatchlings. Growth mark morphology shows readily distinguishable marks similar in appearance to other species, though some animals displayed more diffuse marks. Growth rates remained high (average 2.24–4.77 cm year^?1) from 20 to 80 cm straight carapace length (SCL). Hawksbills larger than 80 cm SCL had average growth rates of 0.3 cm year^?1. There were few adult turtles in the sample; however, results indicate hawksbills have faster growth rates than loggerhead or green turtles, with probable average age to maturity (at size 78.6 cm SCL) occurring between 17 and 22 years.     

Contaminated lead environments of man: reviewing the lead isotopic evidence in sediments,peat, and soils for the temporal and spatial patterns of atmospheric lead pollution in Sweden

Clair Patterson and colleagues demonstrated already four decades ago that the lead cycle was greatly altered on a global scale by humans. Moreover, this change occurred long before the implementation of monitoring programs designed to study lead and other trace metals. Patterson and colleagues also developed stable lead isotope analyses as a tool to differentiate between natural and pollution-derived lead. Since then, stable isotope analyses of sediment, peat, herbaria collections, soils, and forest plants have given us new insights into lead biogeochemical cycling in space and time. Three important conclusions from our studies of lead in the Swedish environment conducted over the past 15 years, which are well supported by extensive results from elsewhere in Europe and in North America, are: (1) lead deposition rates at sites removed from major point sources during the twentieth century were about 1,000 times higher than natural background deposition rates a few thousand years ago (~10 mg Pb m^?2 year^?1 vs. 0.01 mg Pb m^?2 year^?1), and even today (~1 mg Pb m^?2 year^?1) are still almost 100 times greater than natural rates. This increase from natural background to maximum fluxes is similar to estimated changes in body burdens of lead from ancient times to the twentieth century. (2) Stable lead isotopes (²⁰⁶Pb/²⁰⁷Pb ratios shown in this paper) are an effective tool to distinguish anthropogenic lead from the natural lead present in sediments, peat, and soils for both the majority of sites receiving diffuse inputs from long range and regional sources and for sites in close proximity to point sources. In sediments >3,500 years and in the parent soil material of the C-horizon, ²⁰⁶Pb/²⁰⁷Pb ratios are higher, 1.3 to >2.0, whereas pollution sources and surface soils and peat have lower ratios that have been in the range 1.14–1.18. (3) Using stable lead isotopes, we have estimated that in southern Sweden the cumulative anthropogenic burden of atmospherically deposited lead is ~2–5 g Pb m^?2 and ~1 g Pb m^?2 in the “pristine” north. Half of this cumulative total was deposited before industrialization. (4) In the vicinity of the Rönnskär smelter in northern Sweden, a major point source during the twentieth century, there is an isotopic pattern that deviates from the general trends elsewhere, reflecting the particular history of ore usage at Rönnskär, which further demonstrates the chronological record of lead loading recorded in peat and in soil mor horizons.     

Seasonal and diel variation in movement rhythms of sand dollar, Peronella lesueuri (Valenciennes 1841), in Cockburn Sound, Western Australia

Rates and direction of movement in the sand dollar Peronella lesueuri were measured in summer and winter in Cockburn Sound, a large coastal embayment in south-western Australia. P. lesueuri was found to have a diurnal activity pattern throughout the year and had a greater movement rate in the summer (mean of 5.3 cm h^?1, day; 3.9 cm h^?1, night) than in the winter (mean of 2.7 cm h^?1, day; 2.0 cm h^?1, night). Seasonal change in temperature and physiological requirements by the sand dollar are the most likely reason for the seasonal differences. Reasons for diurnal variation were not clear. Direction of movement was found to be random at both times of the year. Based on these movement rates, one sand dollar can bioturbate an approximate area of 0.1 m² day^?1 and 36.4 m² year^?1. At a conservative density estimate of 0.5 sand dollars per m² it takes approximately 20 days for the sand dollars to rework the entire area of the sediments in the habitats they occupy.