Seasonal and spatial variation in the distribution of mangrove macroalgae in the Clyde River, Australia

The objective of this study was to determine whether there was significant spatial and temporal variation in macroalgae epiphytic on pneumatophores of the Grey Mangrove, Avicennia marina (Forsk.) Vierh., in the Clyde River, located 280 km south of Sydney, Australia. Three estuarine sites in the Clyde River were surveyed seasonally on four occasions over a two-year period, and algal distribution and abundance assessed in respect to temporal, inter-site, intertidal (from front to back of mangrove stand) and vertical (from bottom to top of pneumatophores) variation. Sediment and water characteristics, including nutrient levels, were also assessed in order to examine all variables of potential influence on algal distribution and abundance. The results indicated that intertidal position within sites, and vertical height along the length of the pneumatophore, were the greatest influence on algal frequency and biomass. Individual species dominated in different intertidal and vertical zones. These observations, together with the identification of three species of macroalgae that fulfil the criteria for bioindicators/biomonitors of environmental impacts are discussed. © 2006

Seasonal and spatial variation in the distribution of mangrove macroalgae in the Clyde River, Australia

The objective of this study was to determine whether there was significant spatial and temporal variation in macroalgae epiphytic on pneumatophores of the Grey Mangrove, Avicennia marina (Forsk.) Vierh., in the Clyde River, located 280 km south of Sydney, Australia. Three estuarine sites in the Clyde River were surveyed seasonally on four occasions over a two-year period, and algal distribution and abundance assessed in respect to temporal, inter-site, intertidal (from front to back of mangrove stand) and vertical (from bottom to top of pneumatophores) variation. Sediment and water characteristics, including nutrient levels, were also assessed in order to examine all variables of potential influence on algal distribution and abundance. The results indicated that intertidal position within sites, and vertical height along the length of the pneumatophore, were the greatest influence on algal frequency and biomass. Individual species dominated in different intertidal and vertical zones. These observations, together with the identification of three species of macroalgae that fulfil the criteria for bioindicators/biomonitors of environmental impacts are discussed

Isolation and characterization of polymorphic microsatellite loci from Wilsonia backhousei (Convolvulaceae)

Wilsonia backhousei is a clonal saltmarsh plant restricted to the southern latitudes of Australasia and threatened in New South Wales. We have identified eight informative microsatellite loci in the species from (AG)n- and (AC)n-enriched libraries. In 48 samples from two populations we detected an average of five alleles per locus (range 2-8, average HE = 0.45), of which 72% were unique to one population or the other. Six of the eight loci were also amplifiable in Wilsonia rotundifolia under the same reaction conditions. The markers will be excellent tools for use in the management and conservation of both species. © 2006 Blackwell Publishing Ltd

Genetic variation among age-classes of the mangrove Avicennia marina in clean and contaminated sediments

An examination was made of the genetic variation with age in mangrove populations in two estuaries in south-east Australia, one contaminated, the other uncontaminated. Sediment nutrient and metal levels, and isozyme/allozyme complements were measured in three age-classes in four stands in each estuary, to identify site and intergenerational genetic composition, and influences of sediment contamination. Within each river, there were greater genetic distances among the age-classes than among sampling sites. A downstream gradient of genetic distance was found in the uncontaminated river, but not the contaminated one, where genetic distances seemed to reflect site-specific factors, though apparently not the present sediment metal or nutrient levels. It appears that genetic distances in the polluted river may reflect past fluctuations in pollution pressures. In both rivers, genetic distances indicate that the mangroves within one estuary form one population, with 'neighbourhood' differentiation. © 2004 Elsevier Ltd. All rights reserved

Maximising adaptive potential in translocated populations of clonal saltmarsh plants: A case study on Wilsonia backhousei, Convolvulaceae

We investigated the implications of clonality for translocation of Wilsonia backhousei, a threatened, outbreeding, saltmarsh plant with tidally-dispersed fruit. Eight microsatellite loci were used to characterise samples from three estuaries in New South Wales, Australia, and to determine the size and distribution of genetically distinct individuals (genets). Within-population diversity was compared to the presence or absence of seed production using the t test. Ordinal logistic regression was used to investigate the relative influence on seed yield of soil characteristics (soil moisture, salinity, pH) and the number of clonal lineages within a 5 and 10 m radius. Principal coordinate analysis, analysis of molecular variance and Bayesian analysis were used to investigate the extent of gene flow within and among the three estuaries. We found individual genets could cover extensive areas (up to 225 m2) and apparently large populations could consist of only a few individuals. Populations that failed to produce seed had significantly less genetic diversity than populations that produced seed (P = 0.001). Seed yield showed a significant positive response to both increasing soil moisture content (P = 0.003) and increasing genetic diversity in a 5 m radius (P = 0.003). Gene flow was found to occur chiefly within estuaries though occasional longer-distance gene transfer was evident. To maximise adaptive potential in translocated populations of W. backhousei, we recommend sourcing propagules from multiple populations and planting representatives of the different populations in close proximity to facilitate sexual reproduction. These findings are likely to be applicable to other outbreeding clonal saltmarsh plants with tidally-dispersed fruit or seed. © 2013 Springer Science+Business Media Dordrecht

Zonal and seasonal variation in the distribution and abundance of mangrove macroalgae in the Parramatta River, Australia

The purpose of this study was to examine the spatial and temporal variation of macroalgae epiphytic on pneumatophores of the Grey mangrove, Avicennia marina (Forsk.) Vierh., in the Parramatta River, the major estuarine system flowing into Sydney Harbour. No previous studies have examined algal distribution in three spatial dimensions (along the mid-saline length of a river, from front to back of mangrove stand, and from bottom to top of pneumatophores), simultaneously with their temporal variation within mangrove stands. Three sites in the Parramatta River, Australia, were surveyed seasonally on four occasions over a two-year period, and algal distribution and biomass assessed with respect to temporal, site, intertidal and vertical variation. Sediment and water characteristics, including nutrient levels, were also assessed in order to examine all variables that may be influencing algal distribution and abundance. The results indicated that intertidal position within sites (front, middle and back zones of the intertidal mangrove stands) was the factor of greatest influence on algal frequency and biomass, with individual species dominating in different zones. This observation together with the identification of four species of macroalgae that fulfill the criteria for bioindicators of environmental impacts are discussed. © 2005 Elsevier Ltd. All rights reserved

Accumulation and distribution of heavy metals in the grey mangrove, Avicennia marina (Forsk.)Vierh.: Biological indication potential

The accumulative partitioning of the heavy metals Cu, Pb and Zn in the grey mangrove, Avicennia marina, were studied under field conditions. Copper and Pb were accumulated in root tissue to levels higher than surrounding sediment levels. Zinc was accumulated to levels reflecting sediment concentrations. Strong linear relationships existed for all metals in sediments with metals in root tissue. Accumulation of Cu in leaf tissue followed a linear relationship at lower sediment concentrations, with an exclusion or saturation mechanism at higher sediment concentrations. Lead showed little mobility to leaf tissue. Zn showed restricted accumulation in leaf tissue, which correlated with sediment concentrations. Decreases in sediment pH were found to increase Zn accumulation to root tissue. Increasing concentrations of Pb and Zn in sediments resulted in a greater accumulation of Pb to both root and leaf tissue. A. marina roots may be employed as a biological indicator of environmental exposure of Cu, Pb and Zn and leaves for Zn, with temporal monitoring. © 2003 Elsevier Science Ltd. All rights reserved

Assessment of heavy metals in sediments and aquatic organisms in West Lake (Ho Tay), Hanoi, Vietnam

West Lake (Ho Tay) is the largest freshlake in Hanoi, Vietnam. It has a surface area of ≈ 500 ha and a total volume of >107 m3, and is 1-3.5 m in depth. West Lake has been classified as needing protection because of its valuable freshwater genetic resources. Noting that it has been extensively affected by pollution, the objective of the present study was to examine the extent of heavy metal contamination of the sediments and commercially important biota in the lake. Heavy metal concentrations in the sediment from most of 24 samples in West Lake exceeded the Ontario Ministry of Environment Screening Level for chromium (Cr), copper (Cu), manganese (Mn), lead (Pb) and zinc (Zn) concentrations. Aquatic organisms from the lake also were found to be contaminated by heavy metals. The average Zn concentrations in snails and mussels tissues ranged between 174 and 415.μg g-1, and the Pb concentrations between 3.5 and 5.2 μg g-1. The Cu concentration in shrimp (52 μg g-1) and snail (189 μg g-1), and the Pb concentration in all fish species and shrimp from the lake (2.0-5.2 μg g-1) exceeded the Food Standard Australia-New Zealand (FSANZ) health standards for human consumption. The Cd concentration in Cyprinus carpio also exceeded the FSANZ standard. The implications of these study findings for the effective management of the food and ecological resources of West Lake are discussed. © 2007 The Authors. Journal compilation © 2007 Blackwell Publishing Asia Pty Ltd

Reproductive biology of a threatened Australian saltmarsh plant - Wilsonia backhousei

The reproductive biology of a threatened saltmarsh plant, Wilsonia backhousei Hook.f., was investigated with a view to improving conservation and restoration outcomes for the species. Population phenology was studied every two weeks, over two consecutive flowering seasons, in three to six 0.25m 2 quadrats set in monocultures of the species at each of eight sites in New South Wales, Australia. Floral density (flowersm -2) ranged from 0 to 5800±1400m -2 and varied significantly among sites (P70% germination in both fresh seed and seed aged for 6 years); however, seed germination is limited by physical dormancy and is significantly reduced by salinity levels ≥40dSm -1 (6±2.4% after 28 days, P<0.001). Based on these outcomes, recommendations are made for maximising the reproductive potential of remnant and restored populations. © 2012