Marine Invasive Species And Their Effect On Biodiversity

Introduction

In general, invasive species is a type of species that has been tranported from its native environment to a new environment that suits its survival. The exotic species that introduced lack indigenous predators, thus are able to reproduce in large quantities, have an aggressive growth pattern, and populate their new environment are called invasive species. Invasive species are known to cause many negative impacts on native species and their habitat; these include out-competing for and destruction of the native spawning areas, modification of food systems, competition for food and habitat and predation on native species. According to the National Invasive Species Information Center (NISIC), an invasive species is an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.

Invasive species are usually introduced into the marine environment through intentional or/and accidental introductions. Some species were introduced to: improve aquaculture operations; revitalize commercial and recreational fisheries; as a source of food; display as ornamental species; or control pests. Accidental introduction can occur through the ballast water or ballast soil of ships; by attaching themselves to the ship’s hull; as stowaways in cargo; can also occur through marine tourism. Many studies throughout the years have recorded and shown the implications of invasive species and their impact on worldwide biodiversity, the focus of this essay will be on several of those studies, as will be examined below.

Harms of Invasive Marine Species

The harms caused by non-native species are usually described as one of three types: threats to human health, economic harm, and ecological harm. One type of economic harm is the damaging or compromising of ecosystem services. Ecological harm would consist of ecological effects that do not have an economic cost, or threaten human health, but may still be deemed undesirable. Also, some species may cause more than one type of harm, and/or the type of harm might change over time.

Biological Impacts

While many of the alien species become part of the background flora and fauna, others become invasive and come to dominate the native flora and fauna. The numerical dominance of invasive alien marine species overwhelms the already existent native species and alters ecosystem services.

A case study about an invasive crab, Carcinus maenas, originally an European species that is now found in Australia, Japan, South Africa and both coasts of North America, is blamed for the collapse of bivalve fisheries on the North American east coast, and it is feared it will outcompete migratory bird populations on the west coast of North America for favoured shellfish.

There are several broad categories of vectors that can transport marine organisms. With the introduction of the most recent vectors, those associated with the aquarium trade, recreational water users, and the oil, gas and construction industries, the changing nature of domestic and international shipping is altering the diversity and speed of potential vectors, causing the increase of the probability that a known invasive species will be transported and as well as the probability that previously untransported species will find suitable vectors.

Human Health Harms

The global movement of ballast water by ships creates a long-distance dispersal mechanism for human pathogens and may be important in the worldwide distribution of microorganisms, as well as for the epidemiology of waterborne diseases affecting plants and animals.

A research paper in 2000 predicted that coastal ecosystems are frequently invaded by microorganisms from ballast water and other vectors, which could lead potentionally large concentrations of bacteria and virus to successfully colonize ecosystems, due to the flexibility in tolerating a broad range of environmental conditions, combining with a high capacity for increase, asexual reproduction and the ability to form dormant resting stages, allowing rapid population growth.

Ballast water is capable of transporting viral and bacterial pathogens, including the bacteria that causes cholera and the resistant cysts of toxic dinoflagellates that can lead to harmful algal blooms and shellfish poisoning, also ballast water can carry invasive alien marine species that have invaded Europe and the US West coast and can function as a secondary host for the Asian lung fluke (Paragonimus westermani), which that can cause diseases in humans that become infected with the parasite.

Future Developments to Marine Invasive Species

Climate, eutrophication, ocean acidification, and land use change are types of change that are currently occurring. Information on how native and invasive species respond to climate change is very limited, especially when considering intact communities or multi-species assemblages, because most of research has focused on the effects of climate change on organisms in isolation. Although it is hard to predict how these changes in the oceans will affect native and non-native species, ocean warming and ocean acidification, synergistically, might push organisms, communities and ecosystems beyond their threshold limits, although that's not always the case.

Climate Changes

Additive and antagonistic effects are frequently reported in marine invertebrates. For example, well-established non-native species might modify community responses to climate. Non-native species might tolerate a broader range of environmental conditions, having a greater success in a climate change scenario. Climate change leads to increased rainfall or drought, this may also shift invasive species ranges and present new opportunities for invasion. Climate change will also contribute to selective pressures on species, presumably leading to adaptive genetic changes that may influence species success.

Some species do not require climate change to damage ecosystems, yet climate change may exacerbate the damage they do cause. An example of invasive species that can alter the invaded ecosystem even without climate change is the common carp (Cyprinus carpio). The common carp decreases water quality and destroys viable habitat for other desirable species. Climate change may have positive feedbacks for this invasive species if waters get warmer then more frequent droughts will happen, leading to an increase in the amount of suitable habitat to invade. This interaction between climate change and invasive species may intensify ecosystem effects and possibly increase the spatial extent of these effects.

As temperatures and precipitation patterns shift in response to climate change, species ranges will also shift. A current example of a marine plant the threadleaf water-crowfoot (Ranunculus trichophyllus), which has invaded previously non-vegetated lakes in the Himalayas, an invasion attributed to climate change. Tropical aquatic snails are another example of species whose ranges may expand under a changing climate. These snails are carriers of a specific genus of trematodes or blood flukes that cause the disease schistosomiasis. These blood flukes could impact human health if these tropical aquatic snails, move northward as temperatures warm and conditions become more humid. While these aquatic species have not caused the types of damages attributed to other species that respond to enviromental changes, the potential exists to cause further or unforeseen ecological or economic damages.

Conclusion

Based on an analysis of already existent evidence and research, marine invasive species are primary drivers of biological change — they create and modify habitat; outcompete native fauna; act as disease agents or vectors; and threaten biodiversity and human health. Their widespread impacts means that they can affect all other marine conservation programs such as: marine protected areas and marine mammal conservation, etc. Marine invasive species is not just a regional problem, they are a global problem, that require both regional and global solutions.

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