Marine invasions are changing the face of marine communities around the world. S

Question

Marine invasions are changing the face of marine communities around the world. Select three invasive species in marine (not freshwater!) environments that have caused major shifts in marine community structure. For each one of the species, describe 1) characteristics that these species have which have allowed them to be successful invaders, 2) changes in community structure and ecosystem function that have occurred, and 3) ways in which governments/environmental organizations are attempting to remedy the problem. Marine invasions are changing the face of marine communities around the world. Select three invasive species in marine (not freshwater!) environments that have caused major shifts in marine community structure. For each one of the species, describe 1) characteristics that these species have which have allowed them to be successful invaders, 2) changes in community structure and ecosystem function that have occurred, and 3) ways in which governments/environmental organizations are attempting to remedy the problem.

Explanation / Answer

The Red Sea jellyfish (Rhopilema nomadica) entered the Mediterranean through the Suez Canal. Each summer, huge swarms appear along the Eastern Mediterranean shores. At certain times there are 25 jellyfish per square metre forming a ‘jellyfish belt’ about 1 km offshore. This is having a big impact on fisheries and coastal infrastructure. Coastal fisheries are disrupted for the duration of the swarming due to clogging of nets and the inability to sort catches. In Israel, tonnes of jellyfish have to be removed from the seawater intake pipes at the two largest power plants, at an estimated cost of US$ 50,000 per year. Coastal tourism and fishing industries are affected across Israel, Egypt, Lebanon, Turkey and Cyprus.

One of the worst marine invasions occurred in the early 1980s when the North American comb jelly (lediyi is misspelt) was introduced into the Black Sea and Sea of Azov. The species arrived in ship ballast water and rapidly took hold in the foodrich and predator-free waters of the Black Sea until, in 1989, there was an estimated 1 billion tonnes of the alien species. The jellyfish ate vast quantities of fish eggs and larvae as well as the zooplankton that commercially-important fish feed on, leading to the collapse of fish stocks within the Black Sea. By 1994 the anchovy fishery had almost disappeared. The alien comb jelly has completely altered the food web within the Black Sea . Damage to the environment, the economy and human health is being caused by ‘red tides’. These are created during blooms of some microscopic algae known as dinoflagellates that produce powerful toxins. The toxins accumulate in filterfeeding organisms such as oysters, scallops or mussels, and can poison people who eat them. The effects on other native animals that feed on shellfish are mostly unknown, but one study reported a fatal toxin poisoning of 14 humpback whales over a five-week period. The toxin produced by the algae Gymnodinium catenatum for instance can cause Paralytic Shellfish Poisoning which, in extreme cases, causes muscular paralysis, respiratory difficulties and even death.

The spread of this algae has led to closures of shellfish farms and bans on gathering wild shellfish while the blooms occur. Dinoflagellates can be accidentally spread by aquaculture and fisheries equipment such as in oyster cages or on mussel ropes and have also been transported over long distances in ballast water. Alien species can also cause environmental damage when they ‘escape’ from enclosures such as aquariums, zoos or fish farms. Large areas of seabed in the northern Mediterranean are now carpeted by caulerpa (Caulerpa taxifolia), an invasive seaweed which pushes out native marine life, disrupts ecosystems and fishermen’s livelihoods. Mediterranean bream (Sarpa salpa) eat caulerpa but they accumulate toxins from the plant in their flesh, making them inedible. Caulerpa is thought to have entered the Mediterranean accidentally via the Monaco Aquarium, where it was used in fish tanks

Caulerpa taxifolia, the “killer algae”, is a tropical seaweed that has already been able to invade

temperate regions. This algal species has rapidly colonized the Mediterranean, where it covers

the bottom and fills the water column with hundreds of tons of plant biomass per hectare.

Infestations in California took 6 years and over $7M to eradicate. With warming seas around

many temperate coastlines, Caulerpa invasions may become more common.

* The Pacific Lionfish (Pterois volitans) was first detected in Florida in 1990s and is now

common off the Carolinas. As of 2009, the tropical fish was found in north to Cape Cod during

the summer months. Warming conditions probably will permanently expand the range of this

fish along much of the eastern coast of the United States. The broad diet of the lionfish suggests

that this invasive species may become a real threat to many native reef fish populations through

direct predation as well as competition for food resources with native piscivores. Further, its

voracious feeding behavior may impact the abundance of ecologically important species such as

herbivorous fishes that keep seaweeds and macroalgae from overgrowing corals..

Related Questions

Navigate

• Browse (All)
• Browse M
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.