Macroalgal propagules do not survive digestion by the green sea urchinStrongylocentrotus droebachiensis

The ghost of a giant – Six hypotheses for how an extinct megaherbivore structured kelp forests across the North Pacific Rim

“…Terrestrial plants are known to use animals as vectors for seed dispersal, although little is known about biotic dispersal of marine angiosperms such as seagrasses (Tol et al., 2017), and even less about seaweeds. Spores of marine algae have been found on the legs of amphipods and, together with vegetative fragments, have been reported to survive digestion by fish and molluscs (Buschmann & Bravo, 1990; Santelices & Paya, 1989) but not echinoderms (Skern et al., 2003). And while the role of extant sirenians (i.e., manatees and dugongs) in seagrass seed dispersal has been widely discussed (Marsh et al., 2011; McMahon et al., 2014) only recently has it been demonstrated that biotic dispersal of tropical seagrass seeds (by dugongs and green sea turtles) enhances connectivity amongst seagrass meadows across large spatial extents (Tol et al., 2017).…”

“…Although the zoospores of brown algae lack a cell wall and seem to be sensitive to high temperatures (Hoffmann & Santelices, 1991; Lind & Konar, 2017), it has been reported that the gametophytes of some kelp species may remain dormant for months, withstanding environmental factors inadequate for normal development and survival (Dobkowski et al., 2019; Edwards, 2000). Thus, while spore tolerance to digestion remains uncertain (Cabral de Oliveira, 1991; Lind & Konar, 2017; Skern et al., 2003), the spores of some kelp species may have been able to withstand digestion by sea cows and be dispersed in their faeces. As with biotic dispersal in other systems (e.g., Kendrick et al., 2012), these potential mechanisms would have promoted recruitment and colonization of new areas and facilitated genetic exchange (Reed, 1990; Reed et al., 1988).…”