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Metal Pollution, Uptake and Effect on the Australian Saltmarsh Plant Sarcocornia quinqueflora

Vårhammar, Angelica (2013) BIOP31 20122
Degree Projects in Biology
Abstract
Abstract

Saltmarshes are saline wetlands on intertidal shores and their anoxic sediments function as sinks for metals and other pollutants. Saltmarshes are listed as an endangered ecological community in Australia as a result of declines across their range, due to a number of factors including habitat destruction and pollutants. However, while saltmarshes have a high level of legislative protection, the community remains poorly studied, as compared to saltmarshes on other continents. There is therefore a need for investigations of biogeochemical properties in Australian saltmarshes, relationships among metals in the soil and in biota as well as potential mobility through the foodweb. Consequently, this study aimed to investigate the... (More)
Abstract

Saltmarshes are saline wetlands on intertidal shores and their anoxic sediments function as sinks for metals and other pollutants. Saltmarshes are listed as an endangered ecological community in Australia as a result of declines across their range, due to a number of factors including habitat destruction and pollutants. However, while saltmarshes have a high level of legislative protection, the community remains poorly studied, as compared to saltmarshes on other continents. There is therefore a need for investigations of biogeochemical properties in Australian saltmarshes, relationships among metals in the soil and in biota as well as potential mobility through the foodweb. Consequently, this study aimed to investigate the contamination load in each of the locations chosen and to test whether the metals present are taken up by the vegetation and also what relative effect increased soil metal concentration has on plant growth.

Sampling occurred across 50 sites in 10 different locations, within three estuaries in southeast Australia. Individual plants of the common saltmarsh plant Samphire (Sarcocornia quinqueflora) were sampled along with the soil associated with the roots of each plant. A number of soil properties were tested and soil and plant root, stem and leaf samples were digested using hot acid, prior to analysis via ICP-MS and ICP-AES for Cd, Cu, Pb and Zn content. A number of multivariate statistical analyses were then performed on the recorded data.

Differences in metal loading were found among the estuaries, locations and sites, where some estuaries, locations and sites had higher metal loading than others. The uptake patterns together with allocation patterns, i.e. comparisons of metal concentrations in the different plant parts, indicated that the metals are mostly partitioned in the root with limited translocation to the leaf and stem. The essential metals Zn and Cu were also found to be more mobile through the plant than the non-essential Cd and Pb. The relative effect of soil metal concentration on plant height and coverage, as surrogates for plant growth, was low. However, some negative effects were discovered when soil variables including salinity and clay content was considered, potentially causing increased availability and uptake.

Substantial contamination was recorded at a number of sites in this study, with 18 out of 50 sites having metal concentrations above limits specified in the Australian sediment quality guidelines. While some negative effects of high metal concentrations on plant coverage were found in a proportion of the sites where salinity was high, no direct correlation between soil metal concentration and plant growth was observed, perhaps due to metals being mainly phytostabilized in the roots or due to reduced bioavailability in the soil. The limited effects observed on growth does however not eliminate the possibility of metals having significant effects on other factors that affect plant survival, such as seed production, germination, seedling survival or other aspects of the saltmarsh ecology, where fauna may be affected and thus have indirect effects on the survival of the plants. Further studies are required to quantify the impacts of metal pollution on Australian saltmarsh communities and also to further investigate ecotype differences among plants from different locations to determine what soil and plant factors drive uptake, translocation and negative impacts on plant survival.

Popular science summary:

Metal pollution, uptake and effects on Australian Saltmarsh

Human activities have, since the start of the industrial revolution, elevated and depleted the concentrations of all elements throughout the world. These relatively rapid changes have resulted in impacts on all living organisms as some metals can be toxic even at low concentrations. It is therefore important to monitor areas that have been identified as being particularly sensitive to pollution, so that industry and development can sustainably continue.

One of these sensitive areas is saltmarshes. They are intertidal, estuarine areas which are frequently inundated with salt water. The regular flooding makes them act as sinks for pollutants, such as heavy metals, as suspended particles with adsorbed metals are deposited and accumulated. There are many threats to saltmarshes but accumulation of metals in the soil and potential uptake by vegetation and accumulation within the food web is considered the one of most concern. Saltmarshes are threatened throughout Australia, and thus have a high level of legislative protection. However, this also brings an obligation to monitor their health.
This study therefore aimed to determine the effect of metals commonly elevated by human activities (Cd, Cu, Pb and Zn) on the most common Australian saltmarsh plant, across a contamination gradient including metal levels up to and beyond the Australian sediment quality guidelines. This means that impacts on organisms are likely to occur in many of the sites and so the effect on plant growth was investigated. The uptake and translocation of the metals within the plant was also quantified to determine if accumulation or exclusion of metal uptake occur and also the risk of introducing the accumulated metals in the soils, through this plant, into the food web.

Results
All four metals were found to mainly accumulate in the roots of the plant, with limited transport to stems and leaves. Introducing metals into the food web via this species is hence not considerable, except for possibly Zn, which had high rates of translocation to the shoot. Further investigations on the toxicity and accumulation of Zn through the food web are therefore needed.
The effect of metals on growth was generally also found to be low, possibly due to soil properties making the metals less available for uptake at majority of the sites as well as the limited transport found within the plant, reducing possible impacts on sensitive photosynthetic parts. Some negative effects were however found as a consequence of increased Zn levels in areas with greater salinity. Further studies are therefore required to determine the sensitivity of this plant to Zn and also the sensitivity of other plant properties such as seed germination, seedling survival as well as internal cellular systems of the plant to metal exposure to fully conclude the effects of metals on this species.

Advisor: Geoffrey MacFarlane, School of Environmental and Life Sciences, University of Newcastle, Australia
Master´s Degree Project in Plant Ecology and Systematicst 60 credits 2013
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Vårhammar, Angelica
supervisor
organization
course
BIOP31 20122
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
3810264
date added to LUP
2013-06-11 12:18:02
date last changed
2013-06-11 12:18:02
@misc{3810264,
  abstract     = {Abstract 

Saltmarshes are saline wetlands on intertidal shores and their anoxic sediments function as sinks for metals and other pollutants. Saltmarshes are listed as an endangered ecological community in Australia as a result of declines across their range, due to a number of factors including habitat destruction and pollutants. However, while saltmarshes have a high level of legislative protection, the community remains poorly studied, as compared to saltmarshes on other continents. There is therefore a need for investigations of biogeochemical properties in Australian saltmarshes, relationships among metals in the soil and in biota as well as potential mobility through the foodweb. Consequently, this study aimed to investigate the contamination load in each of the locations chosen and to test whether the metals present are taken up by the vegetation and also what relative effect increased soil metal concentration has on plant growth.

Sampling occurred across 50 sites in 10 different locations, within three estuaries in southeast Australia. Individual plants of the common saltmarsh plant Samphire (Sarcocornia quinqueflora) were sampled along with the soil associated with the roots of each plant. A number of soil properties were tested and soil and plant root, stem and leaf samples were digested using hot acid, prior to analysis via ICP-MS and ICP-AES for Cd, Cu, Pb and Zn content. A number of multivariate statistical analyses were then performed on the recorded data.

Differences in metal loading were found among the estuaries, locations and sites, where some estuaries, locations and sites had higher metal loading than others. The uptake patterns together with allocation patterns, i.e. comparisons of metal concentrations in the different plant parts, indicated that the metals are mostly partitioned in the root with limited translocation to the leaf and stem. The essential metals Zn and Cu were also found to be more mobile through the plant than the non-essential Cd and Pb. The relative effect of soil metal concentration on plant height and coverage, as surrogates for plant growth, was low. However, some negative effects were discovered when soil variables including salinity and clay content was considered, potentially causing increased availability and uptake.

Substantial contamination was recorded at a number of sites in this study, with 18 out of 50 sites having metal concentrations above limits specified in the Australian sediment quality guidelines. While some negative effects of high metal concentrations on plant coverage were found in a proportion of the sites where salinity was high, no direct correlation between soil metal concentration and plant growth was observed, perhaps due to metals being mainly phytostabilized in the roots or due to reduced bioavailability in the soil. The limited effects observed on growth does however not eliminate the possibility of metals having significant effects on other factors that affect plant survival, such as seed production, germination, seedling survival or other aspects of the saltmarsh ecology, where fauna may be affected and thus have indirect effects on the survival of the plants. Further studies are required to quantify the impacts of metal pollution on Australian saltmarsh communities and also to further investigate ecotype differences among plants from different locations to determine what soil and plant factors drive uptake, translocation and negative impacts on plant survival.

Popular science summary:

Metal pollution, uptake and effects on Australian Saltmarsh 

Human activities have, since the start of the industrial revolution, elevated and depleted the concentrations of all elements throughout the world. These relatively rapid changes have resulted in impacts on all living organisms as some metals can be toxic even at low concentrations. It is therefore important to monitor areas that have been identified as being particularly sensitive to pollution, so that industry and development can sustainably continue. 

One of these sensitive areas is saltmarshes. They are intertidal, estuarine areas which are frequently inundated with salt water. The regular flooding makes them act as sinks for pollutants, such as heavy metals, as suspended particles with adsorbed metals are deposited and accumulated. There are many threats to saltmarshes but accumulation of metals in the soil and potential uptake by vegetation and accumulation within the food web is considered the one of most concern. Saltmarshes are threatened throughout Australia, and thus have a high level of legislative protection. However, this also brings an obligation to monitor their health. 
This study therefore aimed to determine the effect of metals commonly elevated by human activities (Cd, Cu, Pb and Zn) on the most common Australian saltmarsh plant, across a contamination gradient including metal levels up to and beyond the Australian sediment quality guidelines. This means that impacts on organisms are likely to occur in many of the sites and so the effect on plant growth was investigated. The uptake and translocation of the metals within the plant was also quantified to determine if accumulation or exclusion of metal uptake occur and also the risk of introducing the accumulated metals in the soils, through this plant, into the food web. 

Results 
All four metals were found to mainly accumulate in the roots of the plant, with limited transport to stems and leaves. Introducing metals into the food web via this species is hence not considerable, except for possibly Zn, which had high rates of translocation to the shoot. Further investigations on the toxicity and accumulation of Zn through the food web are therefore needed. 
The effect of metals on growth was generally also found to be low, possibly due to soil properties making the metals less available for uptake at majority of the sites as well as the limited transport found within the plant, reducing possible impacts on sensitive photosynthetic parts. Some negative effects were however found as a consequence of increased Zn levels in areas with greater salinity. Further studies are therefore required to determine the sensitivity of this plant to Zn and also the sensitivity of other plant properties such as seed germination, seedling survival as well as internal cellular systems of the plant to metal exposure to fully conclude the effects of metals on this species. 

Advisor: Geoffrey MacFarlane, School of Environmental and Life Sciences, University of Newcastle, Australia 
Master´s Degree Project in Plant Ecology and Systematicst 60 credits 2013 
Department of Biology, Lund University},
  author       = {Vårhammar, Angelica},
  language     = {eng},
  note         = {Student Paper},
  title        = {Metal Pollution, Uptake and Effect on the Australian Saltmarsh Plant Sarcocornia quinqueflora},
  year         = {2013},
}