Recruitment of Ascophyllum nodosum: wave action as a source of mortality

Abstract

The brown alga Ascophyllum nodosuni (L.) Le Jolis is a dominant rocky intertidal organlsm throughout much of the North Atlantic Ocean, yet its inabilily 10 colonize exposed or denuded shores is well recognized. Our experimental data show that wave action is a major source of mortality to recently settled zygotes. Artificially recniited zygotes consistently exhibited a Type IV survivorsh~p curve in the presence of moving water. As few as 10, bul olten only 1 reLalively low energy wave removed 85 to 99'% of recenlly setlled zygotes. increasing the setting time for attachment of zygotes (prior to distilrbance from water movemenl) had a positive effect on survival. However, survival was significantly lower at high densities, and decreased at long (24 h) setting times, probably as a result of bacleria 011 the surface of zygotes. Spatial refuges provided significant protection from gentle water movement but relatively little protectjon from waves. These data indicate that zygotes are maladapted lor attachment in moving water and suggest that water movement is the primary faclor conlrolliny recruitment and distributional patterns of A. nodosum. These and earlier observations on the long-term lack of colonizat~on of denuded shores suggest that successful recruitment is highly epjsodic on all but the most sheltered shores. Because of the widespread don~ina~~ce of A. nodosum, disturbance b y waves or currents, and stochastic events may play major roles in structuring intertidal comrnunilies In the Northwest Allantic.

Temporal and spatial variation in the early recruitment of fucoid algae: the role of microhabitats and temporal scales

“…Johnson & Brawley 1998]). We thus estimate that the total settlement during the reproductive season was from 0.9 × 10 7 to 2.6 × 10 7 zygotes m -2 yr -1 (= daily average × 30 d × 3 mo) depending on the year, which is consistent with earlier studies of fucoid algae (Ang 1991, Creed et al 1996 and reinforces the idea that post-settlement mortality rates are extremely high in these algae (Vadas et al 1990, Wright et al 2004.…”

“…Lazo et al (1994) found that only 0.01% of Ascophyllum nodosum survived annually and that the mortality was largely due to molluscan herbivores. Our results suggest also that the majority of mortality is occurring shortly after settlement and is likely due to wave dislodgment (Vadas et al 1990, Serrão et al 1996. Other causes such as desiccation (Schonbeck & Norton 1980, Santelices 1990, Brawley & Johnson 1991, Chapman 1995 or density-dependent competition (Ang & De Wreede 1992, Kendrick 1994, Steen & Scrosati 2004 are less likely possibilities, although the effect of grazing (e.g.…”

“…Thus, variation in hydrodynamic forces immediately after settlement could explain the observed variation in recruitment. Hydrodynamic forces vary substantially at this site (Addy & Johnson 2001) both spatially and temporally, and the negative correlation between wind forces and recruitment could be the result of reduced settlement or increased dislodgment under conditions of increased wind-driven water movement as observed elsewhere (Vadas et al 1990). Water motion can also inhibit gamete release (e.g.…”

Distributional expansion ofCarpophyllum flexuosumonto wave‐exposed reefs in north‐eastern New Zealand

“…Those pelagic individuals might be expected to deposit sporelings at greatest densities in the shallows on arrival at reefs, but C. flexuosum seldom occurred in shallow water. We postulate that this is the result of wave action (Vadas et al 1990), or grazing by gastropods (Schiel 1981). C. flexuosum seldom recruited in Ecklonia forest, even where space was available, and we observed no substantial recruitment of C. flexuosum deeper than the previous borders of kelp forests following mass mortality of Ecklonia at Leigh (1995 and1998 & Babcock 1996).…”

Influence of a breakwater on nearby rocky intertidal community structure

“…As for adult populations, exposure to wave action is known to influence the recruitment and survival of a number of intertidal animals and plants. For instance, low energy waves were shown to remove up to 99% of recently settled zygotes of Ascophyllum nodosum, and thus explaining its inability to colonise exposed locations (Vadas et al, 1990). Although populations of the barnacle C. stellatus predominate on wave-exposed shores (e.g.…”