Effects of the alien algae Undaria pinnatifida (Phaeophyceae, Laminariales) on the diversity and abundance of benthic macrofauna in Golfo Nuevo (Patagonia, Argentina): potential implications for local food webs

Abstract

Changes in macroalgal community structure caused by invasive seaweeds have strong impacts on the associated macrofauna due to the role of macroalgae as autogenic ecosystem engineers. This study investigates the effect of Undaria pinnatifida on the abundance and diversity of benthic macrofauna in Golfo Nuevo, northern Patagonia, using a manipulative experiment involving the systematic removal of Undaria microthalli from strips of hard bottom during its eighth-month growing period. Species richness and diversity were higher in plots covered by Undaria than when Undaria was removed. Also, the abundance of two species of crustaceans, one species of sea urchin, one species of nemertina and several species of polychaetes was higher. We attribute these effects to the provision of new habitat structure by Undaria, a larger and structurally more complex species than the local native seaweeds. These results support the hypothesis that complex habitats enhance abundance and species richness, by offering different shelter and foraging opportunities compared to morphologically simpler habitats. Based on a review of diet studies in the region, we speculate that Undaria could potentially produce a bottom-up effect on local food chains by increasing abundance of prey for a wide variety of predators, from invertebrates to marine mammals. While our study has a narrow temporal and spatial scale, we expect similar effects of Undaria on the macrofauna in other sites of the Argentine coast, especially those dominated by small native macroalgae.

The structure of biogenic habitat and epibiotic assemblages associated with the global invasive kelp Undaria pinnatifida in comparison to native macroalgae

“…pinnatifida have been recorded in other invaded regions (Valentine and Johnson, 2005;Irigoyen et al, 2011;South et al, 2015). What is clear from our study is that, at the scale of sporophyte, U. pinnatifida harbours structurally distinct, less abundant and less diverse epibiotic assemblages than the longer-lived native kelps, L. ochroleuca and S. latissima.…”

“…Research into the effects of U. pinnatifida invasions on recipient macroalgae-dominated systems has shown varying impacts on local biodiversity. Studies have shown both an increase (Irigoyen et al, 2011) and a decrease (Curiel et al, 1998;Casas et al, 2004) in local diversity as a result of U. pinnatifida introductions, as well as subtle and inconsistent effects on native species and associated assemblages (Raffo et al, 2009;South et al, 2015). It is likely that U. pinnatifida impacts are context-dependent, but it does have the potential to affect the performance and/or abundance of native kelp species within Plymouth Sound because it is an opportunistic fast-growing species that occupies a substantial area of seabed by early summer (Heiser et al, 2014), and can shade co-existing native species (Smale, pers obs.).…”

Climate driven changes in subtidal kelp forest communities in NW Spain

“…habitat modification and changes in primary productivity) (Libralato et al, 2004;Okada et al, 2005), and climate change (Qui et al, 2010). In particular, studies demonstrate a positive relationship between kelp and decapod abundances (Johns and Mann, 1987;Daly and Konar, 2010;Irigoyen et al, 2011). In this study we make use of this relationship by employing decapod landing data as an indication of changes in kelp abundance, as no quantitative data on kelp abundance was present directly prior to the decline.…”

Resistance and facilitation by native algal communities in the invasion success of Undaria pinnatifida

“…One of the most invasive macroalgal species is the Japanese kelp Undaria pinnatifida (Harvey) Suringer, which has become established in the temperate zone worldwide (Silva et al 2002, Valentine & Johnson 2003, Edgar et al 2004, Farrell & Fletcher 2006, Martin & Cuevas 2006, Baez et al 2010, Irigoyen et al 2011). This seaweed arrived in New Zealand around 1987 and has since spread throughout much of the South Island (Hay & Villouta 1993, Parsons 1995, Stuart 2004, Russell et al 2008, aided by multiple incursions (Uwai et al 2006).…”