What a wonderful Planet we live on/in.
What is Saltmarsh?
Saltmarsh is the Salt tolerant vegetation that grows between Mangroves and the terrestrial zone. Saltmarsh is low growing generally less than 1m in height and typically less than 40cm. Tidal inundation is generally during full moon tides (monthly).
Working with Saltmarsh assist in bringing one into a place of being with the tides and the natural rhythm of life. I marvel at how so many beautiful things out in the Saltmarsh and on the mudflats. Including the birds that fly all the way from Mongolia and Siberia to Australia to feed during the southern summer. Now my life is more closely organised with the cycles – especially the Moon.
“Be in Nature, stay in harmony with Nature, it is you…Learn of Nature, then understand yourself!” Grandmother Pa’Ris’Ha
Today here is a little about Saltmarsh the aim is to share studies presenting techniques to rehabilitate Saltmarsh. While this is an example from Australia Saltmarsh grows in the Coastal areas of all mid-latitude countries.
Rehabilitate here means to restore to health and refers to bringing back at least some of the original ecosystems functions of these communities.
Why is Saltmarsh Important?
Original People of Australia have known the importance of Saltmarsh for thousands of years particularly Coastal Peoples who have harvested foods and medicines from Saltmarsh areas.
Today it is generally taught that Saltmarsh is the supermarket of the estuary turning over organic matter at a high rate, being habitat for crab species that release millions of larva back to the estuary (larvae are food for fish) and providing a water cleaning service.
Coastal Saltmarsh is listed as an Endangered Ecological Community under the New South Wales Threatened Species Conservation Act.
Can You Really Create a Saltmarsh?
Upfront it is key to state that while there are great examples of planting and successfully growing Saltmarsh plants that does not mean a Saltmarsh, with all its ecological values, has been created or rehabilitated. It may take hundreds of years, if ever, for all Saltmarsh ecological functions to be present and resembling a natural Saltmarsh.
Why Rehabilitate or Create Saltmarsh?
Saltmarsh is recognised as an important habitat and is known as key fish habitat. Saltmarsh creation and rehabilitation projects are usually undertaken to replace lost Saltmarsh with the aim of ‘bringing back’ the environmental benefits of the original Saltmarsh (Dalby-Ball 2007 and Frenkel, & Morlan, 1991). Restoration of marine ecosystems to benefit Fisheries is discussed in many papers including Seaman (2007).
In Australia the number of Saltmarsh projects has been increasing over the past 10 years. Saltmarsh creation or rehabilitation projects are now common particularly along the New South Wales coast, where around 70% of the pre 1950s Saltmarsh has been destroyed. The idea of creating marshes to off-set development has been debated for over a decade (Race, & Christie, 1982). The appreciation of Saltmarshes has increased and they are now listed as Endangered Ecological Communities. Sea Level Rise is the now a major threat to these intertidal communities.
In many areas Saltmarsh creation may be an only option for retaining Saltmarsh. This is due to urbanisation extending along coastal edges and shores of estuaries and other places. Including the Lower Hawkesbury River, that has rock faces bordering the Saltmarshes. All these conditions provide no place for a landward migration of Saltmarsh.
Saltmarsh rehabilitation and creation projects should continue and the lessons learnt shared. Papers looking substrate characteristics (Lindau, & Hossner, 1981) and succession of macrobenthos in created a Saltmarsh (Levin, et al 1996) provide good information, yet there is still much to understand in this area.
Does Saltmarsh, Mangrove or Seagrass Rehabilitation or Creation Work?
Rehabilitation Projects generally have the aim of resembling the same naturally occurring community (vegetation type) that has had minimal disturbance.
In relation to created Saltmarshes, Mangroves and Seagrasses some values are understood while others are being studied now and it is likely to take decades to collect data that provides information about how well a created or restored area is proceeding relative to some known and defined target condition (see Chapman 2010 and references within).
Co-ordinated, appropriate monitoring across multiple projects is required so that the generalities of findings regarding success of Saltamrsh projects can be known. Plus research and monitoring of projects should be over extended periods (20+ years) and include a range of study areas – not just plants.
Monitoring of environmental rehabilitation and creation projects tends to focus on vegetation as this is easier to measure than fauna or biochemical or biophysical conditions.
Following are case studies of Saltmarsh rehabilitation projects. Case studies present a range of techniques including i) densely planting a created Saltmarsh and translocating (transplanting) Saltamarsh; ii) a mixture of planting and natural colonisation in a created Saltmarsh; iii) plant colonisation of a created Saltmarsh – no planting and iv) natural regeneration in an existing Saltmarsh.
Port Botany the Biggest Saltmarsh Planting Project in the World
As far as we know please tell us if you know of a larger Saltmarsh planting.
This section presents the Saltmarsh creation works accompanying the expansion of the port at Port Botany, Sydney, NSW and the lessons learnt. Acknowledgement is given to Sydney Ports Corporation for allowing this project to be used as a Case Study.
The saltmarsh creation works have been undertaken by Sydney Ports Corporation as part an $8 million investment by the Corporation to expand and rehabilitate Penrhyn Estuary. With over 230,000 Saltmarsh plantings this is the largest recorded Saltmarsh Planting project. A number of findings have resulted from the project, which is in its third year. This paper shares the knowledge gained in the following areas:
Saltmarsh seed collection and plant propagation,
translocation of Saltmarsh,
Saltmarsh planting – the importance of good soil and irrigation,
maximising establishment of Saltmarsh plants from seed,
the influence of wrack in contributing to rapid changes in species distribution in naturally occurring Saltmarsh, as observed through two years of weekly monitoring.
successful control of six hectares of Bitou Bush and,
successful control of Juncus acutus
The Port Botany Saltmarsh creation project includes monitoring of vegetation and macro-invertebrates. This paper covers only the vegetation.
Port expansion includes dredging and reclamation adjacent to the existing port at Botany and Penrhyn Estuary which provided habitat for migratory bird species.
Ecological works accompanying the port expansion include changing Bitou Bush covered sand dunes into mudflats and Saltmarsh and providing areas of dune with native plants and three islands for wading birds to roost. Areas of mangroves were also converted to mudflats and Saltmarsh. The aim was to maximise habitat for migratory birds and generally improve the ecology of the area.
PORT BOTANY SALTMARSH CREATION – CASE STUDY
Saltmarsh Creation with Dense Planting and Saltmarsh Translocation.
Saltmarsh creation involved 2.4 hectares being densely planted with Saltmarsh species. In addition to this 3000m2 of Saltmarsh was translocated (transplanted) within Penrhyn Estuary. The translocation site was a strip of Saltmarsh approximately 10m wide by 300m long growing in an area that was to become mudflat.
Saltmarsh creation was required as part of the expansion of the Port Botany container terminal. The project also included the protection and monitoring of existing Saltmarsh in the Estuary. A key driver in the Saltmarsh design and plant selection was the requirement for the project to provide habitat for Migratory Wading Birds.
Saltmarsh creation involved removal of dune weeds (Bitou-Bush) followed by excavation of land so that it became inundated by monthly high tides. Saltmarsh plants, including Beaded Glasswort, Sarcocornia quinqueflora, and Salt Couch, Sporobolus virginicus, were planted.
Key aspects of the Saltmarsh creation were:
Expert design and pre-works site evaluation by BioAnalysis and Geoff Sainty of Sainty and Associates.
Monitoring existing Saltmarsh and proposed Saltmarsh creation sites prior to, during and post works by Dragonfly Environmental.
Planning involving representatives from different disciplines including those who would be doing the on-ground work and those monitoring migratory birds.
Approvals and licenses identified and obtained early.
Seed collection and plant growing more than a year before plants were required. (NB Saltmarsh plants grow well from seeds and cuttings but are slow to grow, further there is a narrow window of time for seed collection and permits are required to collect seed or pieces).
Saltmarsh weeds in particular Spike Rush, Juncus acutus removed. Large plants were hand removed and or cut and painted with herbicide. Germinating seedlings were irrigated with Saltwater. Monthly inspections undertaken with immediate removal of new plants.
Creation of intertidal areas by excavation.
Monitoring tidal inundation prior to planting. Filling areas that had water pooling in excess of five days.
Application of soil conditioner (organic rich soil) to the sandy substrate.
Translocation of 3000m2 of Saltmarsh to the area Juncus acutus was removed from.
Protecting and monitoring existing areas of Saltmarsh.
Growing over 250,000 Saltmarsh plants, in two nurseries, with stock from local seed.
Irrigation, with fresh water via a sprinkler system, of all Saltmarsh plantings and translocated Saltmarsh.
Ongoing monitoring of Saltmarsh, both planted (created), translocated and existing.
Summary of Key Findings and Recommendations:
Saltmarsh Seed Collection and Plant Propagation
Permits were sought from relevant authorities (Department of Climate Change and Water for license to collect seed/pieces from an Endangered Ecological Community and from NSW Maritime to get Land owners permission to collect some seed that was not available on the Penrhyn Estuary Site) at the beginning of the Planning Phase.
Saltmarsh species generally have a peak seeding time and there is a short time period for collecting seed when it’s at its optimum. On-site observation, however, shows flowering and seeding occur at other times as well. Even at the one site plants in different clumps will flower and seed at different times. Hence it is essential to have permits ready before the season goes.
For this project seed collection and plant growing started 12-24 months before plants were required. Two nurseries were contracted to grow the plants, both had prior experience and demonstrated success in supplying Saltmarsh. Frequent inspections were made of nursery stock.
Saltmarsh plants grow well from seeds and or cuttings but are generally slow to grow. When grown in nurseries the warmth assists in germination and growth.
Translocation (transplanting) of Saltmarsh
A patch of Saltmarsh was growing on an area that was to be excavated to become mudflats. This 3000m2 area of Beaded Glasswort and Salt Couch was cut into ~ 20cm x 20cm blocks with 100mm deep soil and lifted by hand (shovels) and put onto wooden sheets (plywood) and transported to the recipient site. Transportation was chiefly by a small boat with electric motor.
At the recipient site it was planted into the substrate.
Spaces between blocks were filled with soil from the donor site. The entire area was irrigated thoroughly with salt water. Irrigation continued for six months while the transplanted material established.
New growth was observed within 2 weeks of transplanting. Over 2 years later the translocated material is growing well. Both Beaded Glasswort and Salt Couch produced seed in the season following planting.
The translocation site is where the Spiny Mat Rush, Juncus acutus, had been removed.
Saltmarsh Planting – the Importance of Good Soil and Irrigation
Why Use Good Soil?
Saltmarsh vegetation is made up of plants (obvious I know). Plants generally grow better in good soil. Here good soil means high moisture retention (organics) while still being free draining. Good soil also means it has available nutrients suitable to the plants.
Fertiliser tablets alone are not enough in sandy soils and the soil conditioner is required as it enhances soil moisture and thus reduces plant stress.
In the case at Port Botany a few soil conditioners were trialed. The one chosen had high organic content and was observed not to float away (i.e. few large bark pieces). It is recommended to test suitability of soil conditioner for each site.
Soil conditioner was spread over the sand base and mixed in 100mm using cultivation equipment. Two areas including an island were left with no soil conditioner. In these areas growth appeared slower. This is yet to be scientifically tested.
Is Irrigation Required?
Seedlings die without water (yes another obvious one).
Tidal inundation is not adequate to keep soil moist for seedlings.
Saltmarsh at Port Botany was irrigated for at least 6 months
Plants from nurseries need a hardening off period prior to planting, including:
Being irrigated with Saltwater. Concentrations starting at 5ppt. to 35ppt. generally over three months. The speed of salinity increase depends on how plants are responding.
Plants can die if they go from 100% freshwater to 35ppt. Saltwater.
Post planting irrigate with freshwater. Saltwater may also be used if nursery plants have been successfully hardened off. Freshwater is recommended in all cases as it appears the freshwater results in better plant growth. This is yet to be tested via replicated experiments.
When to Plant
Planting should occur in early spring. Planting at other times is possible. Avoid the start of winter because plants grow slower in winter staying small for a number of months. The smaller size can be a problem if there is excessive algae present and smothering plants, or wind blowing sand and deeply burying plants. The Port Botany project had approximately half the plants planted in spring and the other half at the beginning of winter.
The monitoring design is not set up to investigate a question relating to different planting times and rates of growth. Observations are that those plants planted in Spring grew taller faster and there were fewer plant deaths due to algal smothering than those planted in winter. The winter plants however grew rapidly with the on-set of spring and the warmer weather dried out algae that were covering some plants.
How to Plant
How to plant depends on what is being planted and where. Plants from nursery stock must have a good root system. To check this, a plant can pulled from the base out of its pot and the roots should slide out easily bringing with them all the soil in the pot.
Planting technique depends on the scale of planting and if it is in an area with existing plants. For large open sites such as at Port Botany where speed is required then specialist planting drills can be used. Plants must have their roots wholly in the substrate not the mulch. Once plants are put into the hole the space around them must be back filled with soil.
At Port Botany all Saltmarsh works had to be completed within the six months the migratory birds are away. Planting is the last stage and it follows all the on-ground site creation and preparation. One section of Saltmarsh planting required 124,000 plants to be planted in eight days and this was achieved.
Slow release fertilizer tablets and water crystals were put in each hole prior to the plant being planted.
A key to successful planting is to have quality plants, plant them with as much of their soil (nursery or transplanted) as possible. Where a site has no natural Saltmarsh or Saltmarsh soil it can be advantageous to get soil form the nearest Saltmarsh and use this to inoculate the soil of the planting area. NB permits are required and there must be no adverse impact on existing Saltmarsh. A number of scientific papers have been written about the mico-organism that live in and on the Saltmarsh substrate and the influence they have on Saltmarsh health.
Monitoring should be designed to assess whether the project is meeting defined aims of a project. Stated aims for environmental works at Penrhyn Estuary related to migratory birds and saltmarsh, with the saltmarsh targets relating to plant cover, plant health, total area of Saltmarsh, height of plants, species diversity and presents of invertebrates on the Saltmarsh. In addition to this the monitoring being undertaken by Sydney Ports covers other habitats including birds, sea grass, sediment, water quality and more (Penrhyn Estuary Habitat Rehabilitation Plan 2007).
Projects creating or rehabilitating environments generally start with the idea that there is an ‘ideal condition’ that is the equivalent ‘pristine’ natural environment, in this case Saltmarsh. If this is correct then a way to determine if a created or rehabilitated environment has succeeded would be to measure, through time, how well it approaches being equal to the ideal natural environment. This approach however is not the usual see Chapman (1999 and 2010) for a discussion on this topic.
The site was monitored before any works (near the existing Saltmarsh areas) occurred, during works and will continue post works. Monitoring in this phase (during works) has a high focus on checking to see that plants and physical aspects are in a good condition and taking action if they are not.
Monitoring of environmental works at Port Botany is comprehensive in that it includes monitoring before works commenced, high frequency monitoring during the project and a further 5 years of monitoring post construction works.
Weekly Saltmarsh monitoring focused on issues including: erosion post storm events, presence of pest animals (such as dogs/foxes), pest plants such as Juncus acutus and some algae, inappropriate access by people and extent and depth of tidal inundation. Algae were observed to smother small saltmarsh plants many of which regrew again when the algae started to dry out in Spring / Summer. Deaths from algae coverage were low <0.5%.
Monitoring also provides a record of natural changes such as plant distribution in existing Saltmarsh (see below), timing of seed-set and the presence of fauna particularly crabs. Reports are a source of information for those working on the project, the general public and others involved in Saltmarsh creation projects. There is a wide scope for detailed, scientifically replicated, studies in such Saltmarsh creation projects including looking at changes, through time and space, in substrate and in-soil macroinvertebrates and Saltmarsh microfauna and microflora. An interesting observation was that planted Saltmarsh had a huge seed set in its first season. Mature plants then died back but continued to grow.
Maximising Establishment of Saltmarsh Plants from Seed
This section relates to what can be done to maximise establishment success of seeds that naturally occur in the Saltmarsh. This topic is described in other case studies below.
In relation to Port Botany the major seed occurrence was following the mass flowering and seedlings of Beaded Glasswort. Seeds were washed on the high tide line 10cm deep. Lower areas of the planted Saltmarsh were observed to have poor retention of seeds. Higher areas had seeds in areas where there were stationary debris (that is things that do not move around when the tide comes in/out e.g. along the irrigation line) or depressions such cracks in clay areas or footprints.
Clods of germinating seed were planted amongst mature plants. This was done by making a depression in the sediment the same size as the clod then putting it in. Seedlings continue to grow from these clods.
Probably the greatest factor in successful establishment post germination was the irrigation. Once a seed had a place where it would not wash way it grew, irrespective of the presence of mulch, wrack etc. It must be noted that irrigation is a non-natural method and high germination success in natural conditions has been shown to be due to the presence of seagrass wrack (Chapman and Roberts, 1994).
Changes in Species Composition in Existing Saltmarsh
The role of wrack in changing species composition should not be underestimated. Salt Couch, Sporobolus virginicus, occupied an area of over 1000m2 almost as a monoculture. After a storm event it was thickly covered in wrack resulting in it dying back. Conditions changed and wrack was washed from this area and deposited elsewhere. Patches of bare earth were exposed around the Salt Couch. Seedlings of Beaded Glasswort, Sarcocornia quinqueflora, and Suaeda australis established in these bare areas. Seedling establishment was abundant as the remaining dead grass and scattered wrack caught seeds and retained a moist microclimate. Where there was once a monoculture of Sporobolus virginicus there are now three Saltmarsh species growing.
The above is observation only and there is scope for additional research looking at changes in species distribution and abundance in relation to short-term impacts such as storms and wrack deposition.
Ela way diyi Ngli’ta