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Little is known regarding potential uptake of metals in Australian saltmarsh flora, thus the current study endeavored to examine patterns of Zn, Cu, Pb and Cd uptake and partitioning in the dominant saltmarsh halophyte, Samphire (Sarcocornia quinqueflora), across three contaminated estuaries in New South Wales, Australia. Average sediment concentrations ranged from 62 to 764 μg/g for Zn, 20–52 μg/g for Cu, 27–311 μg/g for Pb and 0.45–1.90 μg/g for Cd across estuaries. Lake Macquarie was the most contaminated estuary, with the Hunter River estuary and Sydney Olympic Park exhibiting intermediate levels of sediment metal contamination. Bioconcentration factors for metal uptake from sediment to roots were ≥ 1 (except for Cu). Translocation within the plant was low for most metals, with apparent barriers to transport identified at the root: non-photosynthetic stem interface for Zn, Cu, Pb and Cd, and at the non-photosynthetic stem: photosynthetic stem transition for Pb and Cd. All metals accumulated in roots with increasing sediment exposure, and lower soil organic matter predicted greater Pb and Cu uptake to roots. Further, increases in sediment pH predicted greater Cd root accumulation. However, transport was regulated to the non-photosynthetic stem for Zn, and to the PS stem for Zn and Pb. In terms of employing S. quinqueflora as a bioindicator, all root metals, and Pb and Cd in non-photosynthetic stem tissue exhibited relationships with sediment metal loads, though high variability made their predictive ability limited.

A glasshouse study investigated the effect of salinity on growth and competitive interactions between two closely related rush species, an Australian native ( Juncus kraussii ) and an exotic ( J. acutus ) species. Overall, both species exhibited decreases in height and total biomass with increasing salinity, although tolerance of J. acutus was marginally lower. We observed asymmetric responses at each salinity, due to the presence of the other species. In fresh-water, co-presence of J. kraussii facilitated the growth (increases in height and total biomass) of J. acutus . However, at 10 ppt salinity direct interspecific competition with J. kraussii adversely affected total biomass of J. acutus . When grown with J. acutus , at 5 ppt but not at 10 ppt, salinity reduced total biomass of J. kraussii . We suggest that interspecific interactions vary with salinity, dependant on relative salinity tolerance of each species. It would appear that in areas receiving regular fresh-water inputs, which reduce salinity stress, J. acutus has the potential to displace J. kraussii .

The distribution and excretion of Cu, Pb and Zn in the root and leaf tissue of the grey mangrove, Avicennia marina was studied using scanning electron microscope (SEM) X-ray microanalysis and atomic absorption spectroscopy. SEM X-ray microanalysis of nutritive root tissue in seedlings dosed with 4 g/l Cu, Pb and Zn revealed accumulation of all metals predominantly in cell walls. The root epidermis provided a major barrier to the transport of Pb only. The endodermal casparian strip was shown to provide a barrier to movement of all three metals into the stele. Washings from mature leaves contained significantly higher amounts of Zn and Cu than control plants after 1 month, suggesting excretion of both metals from the glandular trichomes. In addition, salt crystals exuded from the glands on the adaxial surface of mature leaves were composed of alkaline metals: Zn in Zn-treated plants, and Cu in Cu-treated plants. Leaf tissue in seedlings dosed with 4 g/l Zn showed a decreasing gradient of the metal from xylem tissue, through photosynthetic mesophyll, to hypodermal (water) tissue, with a subsequent increase in concentration in the glandular tissue. A similar gradient was observed across leaf tissue in seedlings dosed with 4 g/l Cu, however, there was no subsequent increase in Cu concentration in glandular tissue. For both metals leaf cell wall metal concentrations were consistently higher than intracellular concentrations.