Herbivory and community organization on a subtidal cobble bed

Abstract

We examined the role of molluscan mesograzers (periwinkles Littorina littorea, limpetsTestudinalia testudinalis and chitons Ischnochiton ruber) in mediating macroalgal succession after a mass mortality of sea urchins Strongylocentrotus droebachiensis in a subtidal cobble bed in Nova Scotia, Canada. Experimental exclusions of mesograzers from cobbles encrusted with smooth (Phymatolithon) or rugose (Lithothamnion) coralline algae resulted in the establishment of a variety of ephemeral filamentous algae, suggesting that these small (2 to 5 mm) but abundant herbivores are the dominant agents controlling early succession and community organization in this habitat. In removing inhibitive effects of early successional species, molluscan grazing facilitated the establishment of fleshy perennial species Fucus evanescens and Chondrus crispus, which occasionally escaped grazing at small size to attain a growth refuge on the cobbles. Algal biomass and species richness were greater on Lithothamnion than Phymatolithon, suggesting that rugose crusts provide more favourable microhabitats for recruitment or survival of various macroalgae. The distribution of mesograzers differed between coralline types, likely influencing the rate and intensity of grazing: periwinkles foraged on both types of crust, whereas limpets occurred primarily on Phymatolithon and chitons on Lithothamnion. All non-coralline algae were consumed when urchins were experimentally reintroduced to the cobble bed, returning the assemblage to the urchin barrens state.

Consistency in a marine algal‐grazer interaction over multiple scales

“…These competitors are differentially removed by grazers (Scheibling et al. ), the result presumably being a net gain to the coralline algae. In this sense, recovery after physical disturbance is facilitated by grazers, and corallines are thus grazer‐dependent.…”

“…, Scheibling et al. ). Whereas this association has been well documented over large spatial scales, here, we examine this ubiquitous relationship over smaller spatial scales relevant to the individuals of the interacting species.…”

“…, Scheibling et al. , McCoy and Kamenos ), calcified red algae whose thalli can be 80%–90% CaCO 3 on a dry‐weight basis (Johansen ). Numerous manipulative studies suggest that the conspicuousness of both erect and crustose corallines in the presence of grazers is achieved because they are both mechanically resistant to grazing and, in some sense, are protected when grazing restricts the growth or persistence of faster‐growing, competitively superior fleshy algae (e.g., Paine and Vadas , Lewis , Sala et al.…”

Biodiversity Knowledge and its Application in the Gulf of Maine Area

“…The decline of large predatory fi sh has been used to explain cascading effects at lower trophic levels involving various combinations of macroinvertevbrates and their invertebrate and algal prey (Steneck et al 2004 ;Frank et al 2005 ). Fluctuating abundances of sea urchins (caused by trophic cascades, direct fi shing on urchins, and disease) and kelp (caused by predation by urchins and other factors (see, for example, Schmidt & Scheibling 2006 )) have attracted particular attention because of the structuring role of kelp in shallow subtidal communities (Scheibling et al 2009 ). The naturally low diversity of the Gulf of Maine kelp ecosystem may have facilitated the rapidity of these changes (Steneck et al 2004 ).…”

Análise espaço-temporal da composição da dieta, preferência alimentar e desenvolvimento de gônadas de Lytechinus variegatus (Lamarck, 1816) no infralitoral rochoso da enseada de Parati-Mirim (Paraty, RJ)

“…Este processo é extremamente prejudicial não somente pela perda da diversidade e riqueza das espécies de alga, mas também causa um efeito cascata em toda a comunidade (Harold & Reed, 1985). Fora isso, esta ação dos ouriços pode afetar as interações competitivas entre as espécies e afetar a sobrevivência e recrutamento de outras espécies (Anderson & Underwood, 1997;Scheibling et al, 2009). Por fim, é importante manter a diversidade das espécies vegetais pois ela fornece complexidade ao hábitat, refúgio para pequenas presas e serve de berçário para algumas espécies que estão nos estágios inicias de vida (Valentine & Heck, 1991).…”