| Since first recorded in Nova Scotia in 1991, the invasive green Codium fragile ssp. tomentosoides has spread rapidly through the shallow subtidal and intertidal zones. To examine the potential of sea urchins (Strongylocentrotus droebachiensis) and snails (Littorina littorea) to regulate Codium on the coast of Nova Scotia, a series of field and laboratory experiments were conducted. In a field experiment, urchins at densities of 0, 50, and 100 urchins/m2, were enclosed on boulders covered with kelp (Laminaria longicruris), Codium, or a mixture of both species from 11 June to 22 September 2002.; In a set of three field experiments, Littorina littorea grazed Codium at specific vulnerable stages. A grazer manipulation experiment with snails grazing on bleached and necrotic thalli of Codium. A second grazer manipulation experiment (with control, inclusion and exclusion treatments) examined snail grazing on Codium recruits (<2 cm in height) in 3 tidepools over 2 years. A third grazer manipulation experiment (with control, inclusion and exclusion treatments) examined snail grazing on residual Codium holdfast tissue (resulting from fragmentation). (Abstract shortened by UMI.)... |
