Firstly, Caulerpa can grow rapidly, leading to concerns it could out-compete native seagrass. Secondly, small fragments of Caulerpa can grow into new plants and create large colonies. Since the initial discovery of Caulerpa in NSW research activities and observations indicate that the impacts of Caulerpa especially on seagrasses are not as severe as first considered.
Rather, it tends to grow primarily on the edges of seagrass beds and less commonly is found interspersed with seagrass. Caulerpa opportunistically occupies suitable uninhabited space. Caulerpa has been found to create habitat that is similar to native seagrasses in some regards e. The latter differences appear to be driven by the differences in sediment chemistry with Caulerpa beds compared to non-vegetated sediments, but more research is needed to investigate what extent these differences are driven by the density of vegetation as compared to the type of vegetation e.
Caulerpa versus seagrasses; Eyre et al. Research by Gribben and Wright focusing on the impacts of Caulerpa on invertebrates living in and on sediments has found that the cockle Anadara trapezia recruits in greater numbers to Caulerpa than to seagrass or unvegetated areas, but that the survival and reproductive output of females cockles is less in Caulerpa. These observed impacts on invertebrates appear to be as a result of low levels of oxygen in water and in the sediments under Caulerpa.
Taylor et al. After 15 years of published research and scientific observations in NSW, the behavior of Caulerpa in the NSW environment is now better understood and we are changing the way we manage it. We believe our efforts will be more effective if we focus on preventing the spread of Caulerpa to unaffected estuaries, rather than on activities that have little effect on established populations. Large outbreaks of Caulerpa are almost impossible to eradicate, require extensive resources and cannot guarantee that Caulerpa will not reoccur so control activities will generally no longer be supported by DPI, unless in exceptional circumstances in a newly affected estuary.
Fishers and boaters will be required to clean their gear and equipment before leaving affected estuaries to minimise the risk of further spread. DPI will continue to issue advisory information that educates people about the importance of implementing good hygiene measures when leaving affected waterways to minimise the potential for spread of this marine alga to new waterways. DPI will continue to support research by universities to investigate the potential impacts of Caulerpa on fishes, invertebrates and nutrients in sediments.
We will also continue to investigate reports of Caulerpa infestations only in waterways where it has not previously been known to occur. The DPI Aquatic Biosecurity team encourages waterway users to be vigilant to help minimise the spread of Caulerpa to unaffected estuaries. The California Department of Fish and Game is seeking funds from the legislature to conduct a survey throughout Southern California to look for infestations of this invasive algae.
Initially the surveys would focus on areas near the previously discovered infestations, but eventually the entire region should be surveyed for the presence of this algae. If any infestations are discovered, immediate eradication efforts will be implemented, using funds from the State Cleanup and Abatement Account. SCCAT has developed a brochure for distribution to the public which summarizes the threat from this destructive algae.
Posters advertising the threat also have been placed in waterfront locations. More localized dispersal occurs through the unintentional movement of plant material on boats, anchors, or fishing gear, or via algal fragments being dispersed by sea currents.
The Problem: The invasive strain of Caulerpa in the Mediterranean Sea smothers other algal species, seagrasses and sessile invertebrate communities. It does this by either out-competing species for food and light or due to the toxic effects of caulerpenyne compounds that are contained in its foliage. Large meadows of Caulerpa have vastly reduced native species diversity and fish habitat.
Native fish which are able to eat Caulerpa , such as Mediterranean bream, accumulate caulerpenyne toxins in their flesh which makes these fish unsuitable for human consumption. The appearance of Caluerpa in southern California in was most probably caused by an aquarium owner improperly dumping the contents of a marine fish tank into a storm water system that fed into Agua Hedionda Lagoon in Carlsbad where this weed was first discovered.
California has since passed a law forbidding the possession, sale or transport of Caulerpa taxifolia within the state. Control Level Diagnosis: Highest Priority. Experts believe it has established too strong a foothold in the Mediterranean to be eradicated or even effectively controlled there, but that the need to curb the spread is extremely urgent. It has been identified by the Global Invasive Species Specialist Group as being among the worst invasive alien species threatening biodiversity.
The threat it poses to marine environments was acknowledged by the government of the United States when in Caulerpa taxifolia was classified as a Prohibited Species under the Federal Noxious Weed Act.
Control Method: It is generally recognized that if an outbreak is to be controlled it is critical to identify the plant at the earliest stages of arrival in a marine environment. Mechanical controls have been attempted in portions of the Mediterranean but with no long-term success. Because the plant spreads with fragmentation, small portions that inevitably break off when attempts are made to uproot the plant only serve to spread it further afield. Attempts to remove plants mechanically with pumps to pull out the plant have resulted in regeneration in the same place at an accelerated growth rate.
Other methods , such as using underwater welding devices to kill the plant with heat, have thus far proved successful at eradication. In terms of biological controls, two species of snail have been identified that attack the algae , Aplysia depilans , and Elysia subornata.
However, due to the dangers the introduction of a new species can cause to an ecosystem, neither snail has been released for testing on the plant in open water. In Carlsbad California the outbreak was successfully stopped through a two-stage process in which a heavy tarp was used to completely cover the plants, and then a herbicide was injected under the tarp to contain and focus the poison on the target species.
It was decided to leave the tarp in place for the foreseeable future, and check the area repeatedly over the next five years.
0コメント