General Impact
Begin and Scheibling (2003) have found that the invasive success of C. fragile ssp. tomentosoides in the northwest Atlantic can be attributed to various characteristics of the alga's life history and physiological ecology. This species exhibits various modes of reproduction, which is a common trait in many invaders. It can reproduce sexually, parthenogentically, and vegetatively. Water currents can and will carry this species over long distances introducing it to new locations. C. fragile is also tolerant of a variety of salinity and water temperature levels. It also thrives in sheltered habitats, which facilitate human mediated dispersal (Begin and Scheibling, 2003).Provan et al. (2005) state that, "C. fragile ssp. tomentosoides has serious economic implications for aquaculture industries. Indeed, the tendency of this species to overgrow and smother oyster beds has earned it the nickname 'oyster thief' (Naylor et al. 2001)." The Benthic Ecology Lab (2001) adds that it has found that, "In its quest for a stable substrate C. fragile ssp. tomentosoides will often make its home on the shells of oysters, scallops, and clams. This can cause problems because an attached adult plant can hinder the movement and feeding of the shellfish. In cases where the attached plant is relatively large and wave exposure is high, the shellfish can be swept away with the plant." Trowbridge (1999) reports that, "The most detrimental effect of C. fragile ssp. tomentosoides is the fouling of shellfish beds, particularly on NW Atlantic shores. There are several direct and direct effects of this attachment (Trowbridge 1998a); these include: 1) smothering mussels and scallops by preventing opening of the valves, clogging scallop dredges, and interfering with the collecting of clams. C. fragile ssp. tomentosoides also is a fouling agent of nets of fin and squid fishers increasing labor costs during harvesting and processing associated with the need to remove the alga from shellfish and the replacement of nets. The authors also state that, "The main negative social effect is that the introduced alga grows profusely and fouls wharf pilings, jetties, ropes, and beaches thereby reducing the amenity associated with the use of coastal areas. Furthermore, the accumulation of masses of C. fragile ssp. tomentosoides rotting on beaches of the NW Atlantic, Mediterranean, and New Zealand produces a foul odor that drives away visitors." The Benthic Ecology Lab (2001) states that, "The morphological structure of C. fragile ssp. tomentosoides will likely increase sedimentation. C. fragile ssp. tomentosoides is a "low lying" alga, making it difficult for some large invertebrates and fish to move among the plants and live in the space between the bushy parts of the algae and the seabed (the understory). In a kelp bed, many species can freely move under the canopy of fronds because the stems (stipes) are narrow and widely spaced. They rely on this understory environment for food, habitat and protection from predators. Replacement of kelp by C. fragile ssp. tomentosoides will undoubtedly affect such species."
Location Specific Impacts:Nova Scotia (Canada) 
Economic/Livelihoods: “Changes in the ecology of the subtidal community will likely have an impact on some of the commercially important species of Nova Scotia. Kelp is the primary food source of sea urchins, which are harvested for their roe. While it has been shown that sea urchins will consume C. fragile ssp. tomentosoides when they come into contact with it (Prince and LeBlanc 1992), sea urchins fed C. fragile ssp. tomentosoides do not produce high quality roe (Scheibling and Anthony 2001)” (Benthic Ecology Lab 2001). “Furthermore, it is possible that the low lying structure of C. fragile ssp. tomentosoides meadows will inhibit the movements of seabed foraging species such as lobster” (Benthic Ecology Lab 2001)
Modification of natural benthic communities: On the Atlantic coast of Nova Scotia, local populations are extremely dense, and Codium fragile may be able to replace native kelp (Laminariales) in the subtidal zone (Chapman 1999, Chapman et al 2002) (Hubbard and Garbary, 2002).
Reduction in native biodiversity: On the Atlantic coast of Nova Scotia, local populations are extremely dense, and Codium fragile may be able to replace native kelp (Laminariales) in the subtidal zone (Chapman 1999, Chapman et al 2002) (Hubbard and Garbary, 2002). Canada
Interaction with other invasive species: In addition to Codium fragile, shores of eastern Canada are undergoing major invasions of the green crab, Carcinus maenas (Gillis et al 2000) and the bryozoan kelp epiphyte, Membranipora membranacea (Chapman 1999, Scheibling et al 1999). Interactions among these species and the native biota will change the ecology of intertidal and subtidal marine communities in coming years (Hubbard and Garbary, 2002). Ireland
Reduction in native biodiversity: On the west-cast shores of the Republic of Ireland and Northern Ireland Codium fragile has encroached on the range of the native congener C. tomentosum. Western North Atlantic Ocean (North America)
Economic/Livelihoods: Codium fragile ssp. tomentosoides is regarded as a serious ecological and economic pest on North West Atlantic shores, particularly for the shellfish industry (Trowbridge, 1999). England (United Kingdom (UK))
Reduction in native biodiversity: “On shores of S England and W Ireland, the alga is not considered a pest but has reputedly replaced the native congener C. tomentosum; whether this change was due to a competitive displacement or to a temporal replacement has never been investigated” (Trowbridge, 1999). Northern Ireland (United Kingdom (UK))
Reduction in native biodiversity: On the west-coast shores of the Republic of Ireland and Northern Ireland Codium fragile has encroached on the range of the native congener C. tomentosum. “On shores of S England and W Ireland, the alga is not considered a pest but has reputedly replaced the native congener C. tomentosum; whether this change was due to a competitive displacement or to a temporal replacement has never been investigated” (Trowbridge, 1999).
|
