Review on invasive alien species (IAS): Challenge and consequence to the aquatic ecosystem services

The invasive alien species (IAS) are widely recognized as a significant threat to marine biodiversity and severely affect ecosystem services. There has been no measurable global assessment of their impacts and routes of introduction. This review highlights some aspects of invasive species and their impacts on the ecosystem in general. For many roots like global transportation, biological pest control, climate changes, and sometimes commercial, invasive species are introduced into the new environments. Afterward, the invasive species are rapidly dominant over the indigenous species because of their first growth, rapid reproduction, ecological competence, and phenotypic plasticity, consequently, altering the structure of Ecosystems and deterring the biological and physical organization of the system. Many policies have been introduced to stop the destruction produced by invasive animals and plants and to prevent upcoming invasions. Some critical components of getting rid of invasion are concern about transporting wildlife to new areas, Ballast water in tankers, aquarium species, and shipping.


Invasive Alien Species?
An invasive alien species (IAS) is an immigrant animal in an ecosystem that causes severe ecological or economic * Corresponding author E-mail address: joy@fmrt.ku.ac.bd (J. Bir) impairment to the environment and sources a major threat to local biodiversity by altering or shifting with the native habitats or species (Molnar et al., 2008;Riley et al., 2008;Pejchar & Mooney, 2009). IAS species have been transferred in a new biogeographical area by human activity at a historical scale

Bir et al. (2022) Marine Science and Technology Bulletin 11(3): 288-298
289 (Audemard et al., 2002). Those species can be familiarized to a new habitat via the ballast water of ocean-going ships, deliberate and unintentional releases of aquaculture species, aquarium samples or bait, and other means (Molnar et al., 2008) and initiating extinction of local floras and faunas, dipping biodiversity, instructing with indigenous organisms for partial resources, and fluctuating habitats. For instances, the American blue crab (Callinectes sapidus, Figure 1A,) is a predatory invasive species that capable to survive very extreme environments and has high fecundity rates. Now this species has widely spread throughout the Mediterranean Sea especially in the coast of Spain, Italy and France (Stasolla & Innocenti, 2014). This American crab has been recorded first in Ebro Delta in 2012, then it has rapidly expanded to the Mediterranean Sea and its adjacent rivers and wetlands. The massive invasion capacity of this crab established this species as a potential threat to the marine biota. This crab also makes threats on traditional fishing boat which is one of the most affected sectors of southern Spain fisheries sectors as the crab accidentally destroys the fishing nets. Another dominant candidate, the zebra mussels (Dreissena polymorpha, Figure 1B) are small freshwater shellfish mainly indigenous to the lakes and rivers that move into the Caspian, and Black seas in eastern Europe, are now widespread throughout the entire European water bodies and The Mediterranean Sea. They are frequently moving into new waterways attached with boats and also with ballast water discharged from commercial ships. This mussel was first introduced at 1980s, since causing millions of dollars in economic loss and altering ecosystems intensely.

Invasive Species: Concerns to Habitat Degradation?
With the quick change in climate and different emerging contaminant, world biodiversity is at immense risk (Martin et al., 2010;Rizzo et al., 2017;Pierucci et al., 2019). The invasive species are achieving extra importance for the declination of oceanic diversity because of their unquantified hazard to ecosystem services (Thomsen et al., 2014;Walsh et al., 2016).
The interactions between invasive species and native dwellers cause drastic changes in marine biotic and abiotic factors of the ecosystem. These changes have continuously transformed marine habitats around the world. Most importantly, these invaders displace native species, food webs, food chain and, alter the change community assembly and also alter essential processes, such as the sedimentation process and biogeochemical cycle (Molnar et al., 2008;Piazzi & Balata, 2009;Rizzo et al., 2017;Pierucci et al., 2019). Therefore, in a normal community, species grow together into an ecosystem balances the limit the population growth of any one species (Crooks, 2005;Simberloff, 2005;Sih et al., 2010;Narwani et al., 2013;Rizzo et al., 2017). These balances include predators, parasites, herbivores, diseases, and other organisms interacting for similar resources and limiting environmental factors (Cook et al., 2007;Crowl et al., 2008). opportunities and a food source (Griffiths et al., 1991).
However, many species have altered the existing environment in order to makes it more favorable for them while adverse for natives' dwellers, which is known as ecological facilitation (Botts et al., 1996;Gallien et al., 2012;Douda et al., 2013;Pierucci et al., 2019). For instance, Spartina alterniflora invasion in the Bay of Arcachon, France that quickly changed the bottom structure with the speedy proliferation of the plant ( Figure 3).

Methods of Ecosystem Modification
Ecosystems are characterized by biological, chemical and physical structure and functions, leading to ecosystem services' production and maintenance. The significant attention of ecosystem ecology is on functional processes and ecological mechanisms that maintaining the function and services produced by ecosystems including the alteration of primary production of biomass, decomposition and trophic relations.

Impacts on Habitat and Ecosystem
Invasive species are acting as major driver of global change having a number of harmful impacts on the areas that they were intruded. Several studies have been reported that they can rapidly modify the biodiversity and ecosystem functions in a virgin ecosystem (Pejchar & Mooney, 2009;Linders et al., 2019). The most significant of these is the widespread loss of habitat. Invasive species can change the food web in an ecosystem by destroying or replacing native food sources (Molnar et al., 2008). perpetuating the population, and other epifauna, such as ascidians, ultimately destroying the entire natural ecosystem (Readman & Rayment, 2016;De Montaudouin et al., 2018).

Impacts on Biodiversity and the Environment
Invasive species are threats to the biodiversity including floras and faunas and overall ecosystem health by disrupting existing biological communities and ecological processes (Molnar et al., 2008;Linders et al., 2019;Proença et al., 2019).
For instance, Asian carp recruited into the United States outcompete native fish for both habitat and foods, leading to significant alterations in natural fish populations that makes the ecosystem less diverse. And always these less diverse ecosystems are more vulnerable to further disturbances such as diseases and natural disasters (Dale et al., 2001;Molnar et al., 2008;Proença et al., 2019). In spites of having some economic and ecological benefits, alien invasions may result in extensive modification in the ecosystem structure, composition, functions and the distribution of the biota, leading homogenization of the world's fauna and flora's diversity (Charles & Dukes, 2008;Molnar et al., 2008;Traill et al., 2010;Proença et al., 2019).

Impact on Hydrodynamics, Nutrient and Water Cycling
Most often, the introduction of alien species alters the hydrodynamics of the existing ecosystem consequently changes the energy flows and trophic relationship of living biota. A study on golden apple snail (Pomacea canaliculata), a herbivore snail observed dramatically decreased aquatic plant populations in wetlands with implications for water parameters and purification (Carlsson et al., 2004;Moulin et al., 2007;Martin et al., 2010). Along with this, the nutrient cycling in aquatic system also be altered by invasive plants that fix nitrogen, and release compounds that alter nutrient availability or retention, including nitrogen and phosphorus, and change topsoil erosion or fire frequency (Dukes & Mooney, 2004;De Montaudouin et al., 2018).

Impact on Human Health
Invasive species are also harmful for human health. Many studies found that invasive zebra mussels produce toxins likes PCBS and PAHs in their tissues. When other predatory organisms prey on these mussels, the toxins are transfer into the food chain and finally can goes through the higher trophic level.
Discharged ballast water from ships sometimes brings harmful bacteria like cholera. Invasive animals can also be vectors for these deadly disease (Gollasch et al., 2019). Encroachment of humans into previously remote ecosystems has exposed exotic diseases such as HIV (Pimentel et al., 2005) to the broader population. Throughout recorded history, epidemics of human diseases, such as malaria, yellow fever, typhus, bubonic plague, spread via some invasive vectors (Elton, 2020). A recent example of an introduced disease is the spread of the West Nile virus, which killed humans, birds, mammals, and reptiles (Lanciotti et al., 1999;Molnar et al., 2008). Examples of various types of impact of aquatic invasive alien species on human health are shown in Table 2.

Causes allergies
Cercopagis pengoi (may cause allergic reactions in fisherman when they clean their nets)

Accumulation of toxins and their transfer to human food
Neogobius melanostomus, Procambarus clarkiia (heavy metals and cyanotoxins)

Impedes recreational activities and tourism
Alexandrium catenella (causing red tides) According to the European Commission, the estimated annual economic losses (Euro) of some developed countries are given in the Table 3.

Control Measures for Invasive Species
There are several strategies have been taken to reduce the damage caused by invasive species along with to prevent future invasions. However, managing invasive alien species is particularly challenging in the ocean because marine ecosystems are extremely interconnected across broad spatial scales. Extermination of aquatic invasive species was only achieved when species were spotted early, and management responded swiftly (Pyšek & Richardson, 2010;Giakoumi et al., 2019). Many international and local laws and regulations have also been introduced to combat the future expansion of invasives. (Hunter & Hart, 2013). Usually, invasive control strategies in the marine environment follow a species-byspecies approach. Though, trait-based prevention and management could result in more effective conservation outcomes as a set of management actions could benefit multiple invasive species sharing common traits. Furthermore, a comprehensive approach to invasive species management should consider, such as the expected impacts of these species on native ecosystems, the available technical intervention options, their expected likelihood of success and their cost, the risks associated with management, and the extent of public support and stakeholder support for the proposed interventions (Pyšek & Richardson, 2010;Ojaveer et al., 2014;Giakoumi et al., 2019).

The various options of management include-
Physical or Mechanical Control -involving physical removal of the invasive species by harvesting or using barriers or traps.
These techniques mainly suitable for the removal of invasive plants.
Chemical Control -Can be executed by using pesticides, herbicides, insecticides, fungicides and other recommended chemicals. As well as adverse effects of using these chemicals in the ecosystem need to be considered.
Biological Control -This method is the most purposeful and ecologically sustainable approach of controlling invasion. In this process many biological individuals are used to reduce the invasive species populations.

Conclusion
Invasive species is a global problem and consider a prime disaster to species diversity. Depending on diverse taxa, geographic locations, and ecosystem types invasive species can alter ecosystem services by affecting populations, community interactions, ecosystem processes, biotics and abiotic variables.
Almost all ecosystem services can be destructively impacted by invasive species, whereas some minor positive impacts exist.
Sometimes the developed country can overcome the consequence of invasive activity, but it's really difficult for developing one, therefore, the ecosystem and species richness are a significant risk to those nations. It is high time to take initiatives to control invasive species distribution for a sound ecosystem.