Evaluation of phosphorus distribution and bioavailability in sediments of a subtropical wetland reserve in southeast China

The phosphorus (P) fractions and bioavailable P in the sediments from the Quanzhou Bay Estuarine Wetland Nature Reserve were investigated using chemical extraction methods for the first time to study the distribution and bioavailability of P in the reserve sediments. A hypothesis was presented suggesting that the bioavailable P in the sediments could be evaluated using the P fractions. The total phosphorus (TP), inorganic phosphorus (IP), organic phosphorus (OP), non-apatite phosphorus (NAIP), and apatite phosphorus (AP) contents in the sediments were in the ranges of 303.87–761.59 mg kg⁻¹, 201.22–577.66 mg kg⁻¹, 75.83–179.16 mg kg⁻¹, 28.86–277.90 mg kg⁻¹, and 127.36–289.94 mg kg⁻¹, respectively. The water soluble phosphorus (WSP), readily desorbable phosphorus (RDP), algal available phosphorus (AAP), and NaHCO₃ extractable phosphorus (Olsen-P) contents in the sediments were in the ranges of 0.58–357.17 mg kg⁻¹, 80.77–586.75 mg kg⁻¹, 1.09–24.12 mg kg⁻¹, and 54.96–676.82 mg kg⁻¹, respectively. The correlation analysis results showed that the NAIP was the major component of the bioavailable P and that the impact of the AP on the bioavailable phosphorus may be minimal. Due to the low TP content in the sediments of the Quanzhou Bay Estuarine Wetland Nature Reserve, the potential pollution risks of P in the sediments may not be very high. The results also show that the bioavailable P concentrations in the sediments of the Quanzhou Bay Estuarine Wetland Nature Reserve could not be evaluated by measuring the P fractions and that the hypothesis was untenable.     

The distribution of carbohydrate side chains along the polypeptide chain of glucoamylase

Glucoamylase is a starch-hydrolyzing enzyme with a glycoprotein structure, used industrially for the conversion of starch to glucose, citric acid, corn syrups, and high-fructose sweeteners. This enzyme possesses an unusual type of structure in which many carbohydrate side chains are linked O-glycosidically to serine and threonine residues of the polypeptide chain. The carbohydrate side chains may be single monosaccharide residues or oligosaccharides of mannose, glucose, galactose, and in some cases N-acetylglucosamine. New data from experiments on the CNBr fragmentation of glucoamylase followed by chemical and immunological characterization of the fragments show that the carbohydrate side chains are distributed randomly along the polypeptide chain. Such a structure is appropriately termed a random model reprensentation for the glucoamylase molecule.     

The ichthyoplankton of a seasonally closed estuary in temperate Australia. Does an extended period of opening influence species composition?

Fish eggs and larvae were collected monthly between September 1987 and April 1989 from sites throughout the main basin and within the saline regions of the two main tributary rivers of Wilson Inlet, a seasonally closed estuary in south-western Australia. Of the eggs, 43.7% belonged to Engraulis australis (Shaw) and the rest to unidentified teleosts. The larval fish assemblage comprised 17 families represented by 25 species. The Gobiidae contained the highest number of species (four) and contributed approximately 57% of all larvae caught. Pseudogobius olorum (Sauvage) and E. australis were the most abundant species, contributing 43.9 and 27.9% to the total larval catch, respectively. The larvae of species which breed within Wilson Inlet dominated the assemblage, both in terms of number of species (64%) and contribution to total catch (99.9%). The numbers of the eight marine species and one freshwater species represented in the ichthyoplankton were very low. Classification and multi-dimensional scaling ordination showed that the composition of the larval fish fauna at the various sites during a period when the estuary remained open to the sea (December 1988-April 1989) was similar to that of the corresponding sites during the same period in the previous year when the estuary had become closed (December 1987-April 1988). This can be attributed to the spatial distribution, time of occurrence and abundance of estuarine-spawned larvae being similar in the two periods and to the rarity of marine-spawned larvae, even in the spring and summer of 1988/1989 when the estuary was open for the whole time when most marine teleosts spawn in south-western Australia. The low occurrence of marine-spawned larvae in Wilson Inlet reflects the fact that tidal water movement within the basin of the system is so small that it is unable to facilitate the transport and dispersion of larvae. The ichthyoplankton of Wilson Inlet resembles that of other poorly-flushed estuaries in that it is low in species richness and dominated by estuarine-spawned larvae.     

Co‐occurrence patterns of trees along macro‐climatic gradients and their potential influence on the present and future distribution of Fagus sylvatica L.

Aim During recent and future climate change, shifts in large‐scale species ranges are expected due to the hypothesized major role of climatic factors in regulating species distributions. The stress‐gradient hypothesis suggests that biotic interactions may act as major constraints on species distributions under more favourable growing conditions, while climatic constraints may dominate under unfavourable conditions. We tested this hypothesis for one focal tree species having three major competitors using broad‐scale environmental data. We evaluated the variation of species co‐occurrence patterns in climate space and estimated the influence of these patterns on the distribution of the focal species for current and projected future climates. Location Europe. Methods We used ICP Forest Level 1 data as well as climatic, topographic and edaphic variables. First, correlations between the relative abundance of European beech (Fagus sylvatica) and three major competitor species (Picea abies, Pinus sylvestris and Quercus robur) were analysed in environmental space, and then projected to geographic space. Second, a sensitivity analysis was performed using generalized additive models (GAM) to evaluate where and how much the predicted F. sylvatica distribution varied under current and future climates if potential competitor species were included or excluded. We evaluated if these areas coincide with current species co‐occurrence patterns. Results Correlation analyses supported the stress‐gradient hypothesis: towards favourable growing conditions of F. sylvatica, its abundance was strongly linked to the abundance of its competitors, while this link weakened towards unfavourable growing conditions, with stronger correlations in the south and at low elevations than in the north and at high elevations. The sensitivity analysis showed a potential spatial segregation of species with changing climate and a pronounced shift of zones where co‐occurrence patterns may play a major role. Main conclusions Our results demonstrate the importance of species co‐occurrence patterns for calibrating improved species distribution models for use in projections of climate effects. The correlation approach is able to localize European areas where inclusion of biotic predictors is effective. The climate‐induced spatial segregation of the major tree species could have ecological and economic consequences.     

Stereological Determination of Orientations,Second-Order Quantities and Correlations for Random Spatial Fibre Systems

This paper presents methods for the stereological analysis of spatial fibre systems on the base of planar or thin sections. Under the assumption that the cross-section figures of the tubular fibres can be measured, the orientation distribution of the fibre system and its line density L_v can be determined from one section only and without distributional assumptions. A simple way to study the degree of randomness of fibre systems consists in the statistical analysis of the point pattern of centres of intersection figures. More sophisticated methods are of stereological nature and yield the spatial reduced second moment measure. Similarly also correlations between two fibre systems can be quantified. The methods are demonstrated by two examples concerning samples of human brain.     

The Exact Distribution of the Anderson-Kannemann Statistic

The Anderson-Kannemann test is a rank test for treatment effects in a randomized block design with K treatments and N blocks. In this paper, an algorithm for computing the exact distribution of the Anderson-Kannemann test statistic under the null hypothesis is deduced. Then, the exact distribution is compared with the asymptotic χ²-distribution, and it is shown that the exact distribution is approximated fairly well by the asymptotic distribution. Tables of the exact distribution are given for K = 3, N = 3(1)15; K = 4, N = 3(1)11; K = 5, N = 3(1)7; and K = 6, N = 3(1)5.     

Halobates collected during the circumnavigational expedition 'Operation Drake'

Samples of marine pleuston were collected from the sea-surface along considerable sections of the track of Eye of the Wind during its 2-year circumnavigational expedition 'Operation Drake' from November 1978 to October 1980. One hundred and eleven of the tow samples contained insects of the genus Halobates . They were assigned to four oceanic species: H. micans, H. sericeus, H. germanus and H. splendens; two coastal species: H. maculatus, H. princeps, and one undescribed species. Various development stages of the oceanic species were found. The locations, time of collection and surface temperatures where sea-skaters were collected are tabulated. Distributional boundaries and population densities of the oceanic species collected are discussed.     

The use of breeding sites of Tilapia congica (Thys & van Audenaerde 1960) to delineate conservation sites in the Lake Tumba,Democratic Republic of Congo: toward the conservation of the lake ecosystem

To guide the zoning process in Lake Tumba, Democratic Republic of Congo, breeding sites of Tilapia congica were studied. Physical metrics measured were: nest depths, exposure to sun rays, distance from the edges, site spreads, and habitat types. Mean nest depth = 0.23 m ± 0.08 (SD), range = 0.04–2.2 m (n = 553 nests); 100% (n = 70 sites) sites were exposed to the sun and the polynomial regression analysis showed 90% sites were within the range 51–250 m from the lake shores (y = ?1.7143x² + 10.371x? 1.8; R² = 0.597, n = 70 sites), with 60% clumped within the range of 51–150 m, indicating a relationship between nesting sites and the distance from edges. The largest group spread group was 300 m, and among the four breeding sites identified, one was ～10 km long, meaning a zonal spatial spread ∏ = 300 ha and a core reproduction zone ∏′ = 100 ha. T. congica built 87.30% of their nest in habitats where Hippo grass Vossia cuspidata (48.20%) and Water lily Nympheae stellata (39.10%) dominated. T. congica shared 41.81% of its nesting sites with other fish species, leading to the conclusion that protecting the species habitats would provide the umbrella for the conservation of other species.