Lacuna vincta (Mollusca, Neotaenioglossa) herbivory on juvenile and adult Nereocystis luetkeana (Heterokontophyta, Laminariales)

Abstract

Herbivory can be an important factor structuring coastal algal communities. Herbivores may preferentially graze particular algal species or tissue types. Mesograzers, despite their small size, can critically weaken kelp thalli and impact entire kelp beds. We propose that when kelp beds are composed of several kelp cohorts, mesograzers will selectively choose to inhabit younger plants and grazing activities will have a greater impact on younger plants. This study investigated the effects of grazing by the littorinid gastropod, Lacuna vincta, on different age classes of the bull kelp, Nereocystis luetkeana by (1) testing food preference of L. vincta on juvenile, first-year adult, and second-year adult Nereocystis blades in the laboratory, (2) determining substrate (blades of different ages) preference of L. vincta in the laboratory, and by (3) estimating in-situ herbivore abundances and densities on juvenile and adult Nereocystis. Results demonstrated that grazing by L. vincta produced greater damage on juvenile than older Nereocystis tissues. Although L. vincta did not select juvenile versus older kelps as substrate in the laboratory, in situ surveys showed that differences existed between age classes with higher L. vincta densities on juvenile than adult kelp. We conclude that at a local scale, L. vincta can be an important structuring factor in Nereocystis populations due to its high density and grazing ability.

Invasive seaweeds transform habitat structure and increase biodiversity of associated species

“…). This facilitates kelp loss and lead to greater light availability to understorey species (Johnson & Mann ; Chenelot & Konar ). L. vincta is a cold‐water northern temperate species that experiences physiological stress at 25°C and mortality at 30°C (McMahon & Russell‐Hunter ).…”

“…Grazing by gastropods such as L. vincta on kelp thalli and reproductive structures (O'Brien & Schiebling 2016), can reduce canopy area, particularly in the presence of D. japonica (Low et al 2015). This facilitates kelp loss and lead to greater light availability to understorey species (Johnson & Mann 1986;Chenelot & Konar 2007). L. vincta is a coldwater northern temperate species that experiences physiological stress at 25°C and mortality at 30°C (McMahon & Russell-Hunter 1977).…”

Introduced rats indirectly change marine rocky intertidal communities from algae- to invertebrate-dominated

“…Herbivorous snails and limpets are important components of gull and oystercatcher diets (20,21,25,27), and both are known to significantly reduce fleshy algal cover in the marine rocky intertidal through grazing (21,(27)(28)(29)(30)(31). Therefore, rat predation on the birds indirectly changes the rocky intertidal community from an algal-to an invertebrate-dominated system by releasing intertidal herbivores from predation pressure, which reduces fleshy algal cover via increased herbivory.…”

Spatial and temporal variation in grazing damage by the gastropod Lacuna vincta in Nova Scotian kelp beds

“…Mesograzers, such as small snails and crustaceans (Brawley 1992), can have large direct effects on benthic community organization by influencing the dynamics of early succession ), reducing macrophyte biomass (Johnson & Mann 1986, Chenelot & Konar 2007, and cycling nutrients through consumption of detrital material (Robertson & Lucas 1983). Tissue damage by mesograzers can also increase the susceptibility of macrophytes to other forms of disturbance, such as breakage or dislodgement by hydrodynamic forces (Duggins et al 2001.…”

“…However, in areas where sea urchins are rare or absent, mesograzers may be the dominant herbivores (Kangas et al 1982, Johnson & Mann 1986, Duggins et al 2001, Chenelot & Konar 2007). In the northwest Atlantic, the gastropod Lacu -na vincta is the only mesograzer known to consume macroscopic kelp sporophytes (Brady-Campbell et al 1984, Johnson & Mann 1986).…”