Invasion
Invasion Description
1st record: Graves shoal/Nova Scotia/Mahone Bay (Atlantic Ocean) (1991, Bird et al. 1993; Begin and Scheibling 2003)
Geographic Extent
Graves shoal/Nova Scotia/Mahone Bay (Atlantic Ocean) (1991, Bird et al. 1993; Begin and Scheibling 2003); Nova Scotia/St. Margarets Bay (1991, Begin and Scheibling 2003; 1999, Hubbard and Garbnary 2002); Halifax County/Nova Scotia/Cranberry Cove (1999, Begin and Scheibling 2003, Schmidt and Scheibling 2005, near Halifax); Point Tupper/Nova Scotia/Strait of Canso (2008, Choi et al. 2-016)Cape Sable-Canso/Nova Scotia/Atlantic Ocean (Watanabe et al. 2009, patchily distributed on ~500 km of coastline, most abundant near Mahone & St. Margarets Bays); Spanish Room/Newfoundland/Mortier Bay (8/22/2012, Matheson et al. 2014, 47.195ºN, 55.075ºW); Woody Island/Newfoundland/Placentia Bay (9/27/2012, Matheson et al. 2014, 47.784ºN, 54.180º); Arnold’s Cove/Newfoundland/Placentia Bay (8/30/2013, Matheson et al. 2014, 47.756ºN, 53.988ºW)
Vectors
| Level | Vector |
|---|---|
| Alternate | Hull Fouling |
| Alternate | Natural Dispersal |
Regional Impacts
| Ecological Impact | Competition | |
| Codium fragile invades after disturbance to kelp beds, and displaces native kelps (Laminaria digitata and L. longicruris). Major causes of displacement of kelps include outbreaks of the sea urchin Strongylocentrotus droebachiensis, and the killing of kelps by the introduced bryozoan Membranipora membranacea. A survey in the year 2000 found extensive meadows of C. fragile in Mahone and St. Margarets Bays (Chapman et al. 2002). In experiments, removal of Laminaria and a smaller native brown alga, Demarestia sp. resulted in an increase in C. fragile biomass. Conversely, removal of C. fragile resulted in increased growth of Laminaria and Demarestia species. Codium fragile meadows inhibit the recruitment of native kelps and other algae (Scheibling et al. 2006). However, in areas off the coast of Nova Scotia, large growths of C. fragile were vulnerable to winter storms, and declined from 2000 to 2008, and were replaced by the native kelp L. digitata (Kelly et al. 2011). | ||
| Ecological Impact | Habitat Change | |
| Codium fragile can replace a kelp canopy with less favorable habitat (Chapman et al. 2002). The differing structure of canopy of Codium fragile permits better survival of juvenile fishes and crabs (Schmidt and Sheibling 2007). These changes were transient, in regions off Nova Scotia, where the large growths of C. fragile were removed by winter storms, and recolonized by native kelps (Kelly et al. 2011). Small bivalves and amphipods were most abundant in the C. fragile-dominated state, compared to amphipods and small gastropods in the kelp-dominated state (Kelly et al. 2011). | ||
| Ecological Impact | Food/Prey | |
| Codium fragile was poor food for the sea urchin Strongylocentrotus droebachiensis. The urchins consumed 3.5X more algae than those fed Laminaria sp., but had less growth, and no gonadal production (Scheibling and Anthony 2001). | ||