American Oceans

Invading Barnacles

Barnacles are a type of marine crustacean that attach themselves to hard surfaces such as rocks, ships, and docks. While some barnacle species are native to certain regions, others have been introduced through human activities such as shipping and aquaculture. These introduced species, also known as invasive or non-native species, can have significant ecological and economic impacts on the areas they invade.

a horseshoe crab on the beach with barnacles all over it

Invasive barnacles can outcompete native species for resources such as space and food, alter the physical and chemical properties of the environment, and even serve as vectors for diseases. For example, in Kaneohe Bay, Hawaii, the larger and faster-growing invasive barnacle Balanus reticulatus has been observed to reduce the abundance of the native barnacle Chthamalus proteus through substrate pre-emption. Similarly, the introduction of the Pacific barnacle Balanus glandula to the Atlantic coast of South America has resulted in a shift in the composition of the intertidal community, with the invasive species dominating over native barnacles.

Understanding the mechanisms behind the success of invasive barnacles is crucial for developing effective management strategies. Researchers have identified various factors that contribute to the establishment and spread of invasive barnacles, including high reproductive rates, broad temperature tolerances, and the ability to attach to a variety of substrates. By studying the interactions between invasive and native barnacles, scientists can gain insights into the ecological and evolutionary processes that shape marine communities and inform conservation efforts.

Understanding Barnacles

acorn barnacles up close

Barnacles are marine invertebrates that belong to the class Cirripedia, which is a subclass of Crustacea. They are arthropods and are closely related to crabs, lobsters, and shrimps. Barnacles are known for their hard shells and the cirri, which are feathery appendages that they use to filter food from the water.

Barnacles are found in all the world’s oceans, from the Arctic to the Antarctic. They are also found in estuaries, intertidal zones, and on rocky shores. They are sessile, which means they attach themselves to rocks, shells, and other hard surfaces, and spend their entire lives in one place.

Barnacles have a complex biology and life cycle. They start out as free-swimming larvae called cyprids, which settle on a hard surface and metamorphose into juvenile barnacles. Juvenile barnacles grow into adults, which can reproduce sexually or asexually. Some species of barnacles can also be parasitized by rhizocephalan barnacles, which are a type of crustacean that lives inside the host barnacle’s body.

Barnacles have a slow growth rate and can take several years to reach maturity. They are also sensitive to changes in their environment, such as changes in temperature, salinity, and water quality. These factors can affect their growth and reproduction, and can also make them more susceptible to disease and predation.

Invading Species and Their Distribution

cluster of barnacles on a rock

Barnacle invasions have been documented in various regions across the world. In North and South America, several non-native and invasive species have been identified. The Pacific coast of North America has been invaded by several barnacle species, including Balanus glandula, Balanus trigonus, and Balanus amphitrite Darwin. These species have also been reported in the Hawaiian Islands, along with another non-native species, Megabalanus coccopoma.

In Brazil, several exotic barnacle species have been identified, including Amphibalanus eburneus, Balanus reticulatus, and Balanus trigonus. The distribution and abundance of these species vary depending on the region. For example, A. eburneus is more common in the northeastern region, while B. reticulatus is found primarily in the southern region.

The Gulf of Mexico and the Atlantic coast of North America have also been invaded by several non-native barnacle species, including Elminius modestus and Austrominius modestus. These species were likely introduced through the Panama Canal and have since spread throughout the region.

In South America, several non-native barnacle species have been reported, including Balanus glandula, Balanus trigonus, and Balanus amphitrite Darwin. These species have invaded the Western South Atlantic and have been reported in Colombia, Ecuador, and Peru.

The biogeography and distribution of these invasive barnacle species are influenced by a variety of factors, including shipping traffic, ocean currents, and temperature. The University of California has conducted extensive research on the distribution and abundance of these species, providing valuable insight into the impacts of non-indigenous species on marine ecosystems.

Barnacles and Their Habitats

barnacles on a piece of driftwood

Barnacles are sessile crustaceans that attach themselves to various substrates, including rocks, wood, and other hard surfaces. They are commonly found in intertidal zones, where they are exposed to the alternating periods of immersion and emersion due to the tide.

Barnacles are known to inhabit a wide range of habitats, including estuaries, continental shelves, lagoons, and lower salinity settings. They are particularly abundant in the intertidal zone, where they compete for space and resources with other sessile organisms.

One of the most common species of barnacles found in intertidal zones is Balanus amphitrite. This species is known to attach itself to a variety of substrates, including rocks, shells, and other hard surfaces. It is also able to tolerate a wide range of environmental conditions, including changes in salinity, temperature, and water flow.

Barnacles are important members of intertidal communities, providing food and habitat for a variety of other organisms. They are also important indicators of environmental change, as they are sensitive to changes in water quality and other environmental factors.

Ecological Impact of Invading Barnacles

rock in the sand covered in barnacles

The invasion of non-native barnacles can have significant ecological impacts on marine organisms and community structure. One such impact is niche compression, where invading species compete with native species for key resources such as substrate and space. This can lead to the decline or extirpation of native species, as well as changes in community structure.

Settlement and recruitment of exotic species, such as the Australasian barnacle Austrominius modestus, can occur on a variety of substrates including buoys, coral, and other marine fauna. The invasion of A. modestus has been associated with substrate pre-emption, where it outcompetes native barnacles such as Semibalanus balanoides for space.

Field experiments have shown that A. modestus can also exclude native barnacles such as Chthamalus proteus through competition for key resources. The invasion of A. modestus has also been linked to changes in fishery yields, as it competes with native species for planktonic food sources.

Management strategies for invasive barnacles include the removal of fouled buoys and other structures, as well as the prevention of further introductions through ballast water management and other measures. It is important to monitor the spread of invasive species and their impacts on marine ecosystems to ensure the health and sustainability of these environments.

Barnacles and Human Interaction

a cluster of barnacles on a ship

Barnacles have a long history of interaction with humans, particularly in the context of ships and fouling. Ships have historically been a major vector for the spread of barnacles around the world, as they can attach themselves to the hulls of ships and be transported to new locations. This has led to multiple invasions of new areas by different species of barnacles.

Fouling is a major problem associated with barnacles, as they can attach themselves to a variety of surfaces, including ships, pilings, and plastic. This can cause damage to structures and reduce their lifespan. In addition, the presence of barnacles can also impact the survival of other organisms that rely on these structures for habitat.

One particularly invasive species of barnacle is the Megabalanus coccopoma, which has been shown to have a negative impact on the survival of ecologically similar species. This species has been found to be particularly successful in colonizing new areas, and has been responsible for displacing other barnacle species in some locations.

Predators can play an important role in controlling the spread of invading barnacles. For example, the acorn barnacle has been shown to be vulnerable to predation by certain species of crabs. Understanding the interactions between predators and invading barnacles can provide insight into potential management strategies.

The Life Cycle of Barnacles

Barnacles have a unique life cycle that involves a free-swimming larval stage and a sessile, attached adult stage. The larval stage of barnacles is called a nauplius, which hatches from eggs laid by adult barnacles. During the nauplius stage, barnacles feed on plankton and undergo several molts before developing into a cyprid larva.

The cyprid larva is the final larval stage of barnacles and is responsible for finding a suitable place to attach and metamorphose into an adult barnacle. Cyprid larvae use a variety of sensory cues to locate suitable surfaces, including chemical cues and surface texture.

Once the cyprid larva has found a suitable surface, it attaches using a cement gland and undergoes metamorphosis into a juvenile barnacle. The juvenile barnacle undergoes several molts before reaching adulthood.

Breeding in barnacles occurs once they have reached adulthood. Barnacles are hermaphroditic, meaning they have both male and female reproductive organs. However, they cannot self-fertilize and require a partner for reproduction. During breeding, barnacles release sperm and eggs into the water, where fertilization occurs.

Marine fouling is a major problem caused by barnacles. Barnacles attach to the hulls of ships, piers, and other marine structures, causing damage and reducing efficiency. Amphibalanus reticulatus is an invasive barnacle species that has been found in many parts of the world, including the Mediterranean Sea and the Atlantic coast of North America. This species is known for its rapid colonization and ability to displace native species.

Pearl Harbor is a location where barnacles have been found to be a major problem. The warm waters and high nutrient levels in the harbor provide ideal conditions for barnacle growth and reproduction. The presence of barnacles can cause damage to boats and other structures in the harbor, as well as increase the risk of fouling and invasive species introduction.

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