Begin and Scheibling (2003) believe that, \"The success of C. fragile ssp. tomentosoides in colder waters north of Cape Cod, in regions previously considered unsuitable for this species, suggests a new ecotype along the northern extent of its range.\"

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.\"

A two year study was undertaken for the Department of Environment and Heritage (Australia) by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) to identify and rank introduced marine species found within Australian waters and those not found within Australian waters.
All of the non-native potential target species identified in this report are ranked as high, medium and low priority, based on their invasion potential and impact potential. C. fragile tomentosoides is identified as one of ten most damaging potential domestic target species, based on overall impact potential (economic and environmental). A hazard ranking of potential domestic target species based on invasion potential from infected to uninfected bioregions identifies C. fragile tomentosoides as a 'medium priority species' - these species have a reasonably high impact/or invasion potential.
For more details, please see Hayes et al. 2005.
The rankings determined in Hayes et al. 2005 will be used by the National Introduced Marine Pest Coordinating Group in Australia to assist in the development of national control plans which could include options for control, eradication and/or long term management.

Nyberg and Wallentinus (2005) state that C. fragile ssp. tomentosoides is one of five top risk species in Europe. The authors study quantitatively ranked species traits which facilitate introduction and predominance using interval arithmetic to search for common patterns among 113 marine macroalgae introduced in Europe. From the abstract Nyberg and Wallentinus (2005) “Three main categories were used: dispersal, establishment and ecological impact. These were further subdivided into more specific categories, a total of 13. Introduced species were compared with the same number of native species randomised from the same families as the introduced. Invasive species (i.e. species having a negative ecological or economical impact) were also compared with non-invasive introductions, separately for the three algal groups. In many categories, as well as when adding all species, the introduced species ranked more hazardous than the native species and the invasive species ranked higher than the non-invasive ones. The ranking within the three main categories differed, reflecting different strategies between the species within the three algal groups. When all categories (excluding salinity and temperature) were summed, the top five risk species, all invasive, were, in descending order, C. fragile ssp. tomentosoides, Caulerpa taxifolia, Undaria pinnatifida, Asparagopsis armata and Grateloupia doryphora, while Sargassum muticum ranked eight and Caulerpa racemosa ten. Fifteen of the twenty-six species listed as invasive were among the twenty highest ranked