Resource availability and invasibility in an intertidal macroalgal assemblage

Abstract

The invasibility of a low intertidal macroalgal assemblage was experimentally tested from March 2003 to April 2004 at 1 locality in northern Spain. It was hypothesised that a community becomes more susceptible to invasion when there is an increase in the amount of key resources. A bifactorial ('nutrient supply' and 'macroalgal biomass removed') orthogonal experiment was designed with 3 levels in each factor (high, medium and control). Fertile plants of Sargassum muticum (Yendo) Fensholt were transplanted to each plot to simulate the arrival of an invader. The invasibility of the assemblage was quantified in the pre-(density of recruits) and post-settlement (percentage cover, size and density of S. muticum at the end of the experiment) phases of S. muticum's life cycle. Results supported the initial hypothesis. Both space availability and nutrient enrichment facilitated the establishment and spread of S. muticum in the experimental plots. Established S. muticum plants grew faster in enriched plots than in controls. Furthermore, different successional assemblages played different roles in resisting invasion as S. muticum's life cycle progressed. In the initial stage of the invasion, the Bifurcaria bifurcata canopy inhibited recruitment by S. muticum, whereas understory species did not have a significant effect on invasion success. In contrast, an increased survivorship of S. muticum beneath the canopy of B. bifurcata was observed in those plots where S. muticum had successfully recruited. This study shows that the invasibility of this low intertidal assemblage is mediated by a complex interaction of several resources acting at different stages during S. muticum's invasion.KEY WORDS: Sargassum muticum · Invasibility · Marine invasion · Nutrients · Disturbance · Bifurcaria bifurcata · Macroalgal assemblage Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 313: [85][86][87][88][89][90][91][92][93][94] 2006 On a world-wide basis, space and seawater inorganic nutrients are the limiting resources for macroalgae in most temperate systems (Chapman & Craigie 1977, Sousa 1985, and therefore, in the context of FRAT, one might expect them to have effects on the susceptibility of communities to invasion by alien species. It has been argued that disturbance facilitates invasion by reducing the abundance of competitors or by increasing resource levels (D'Antonio 1993), especially in intertidal habitats where disturbances are strong organising forces of the community structure (Dayton 1971). Nutrient availability is another important ecological factor regulating the structure of coastal macroalgal communities (Valiela et al. 1997, Benedetti-Cecchi et al. 2001, and several studies on terrestrial systems have shown its importance in determining a community's invasibility (see Davis et al. 2000). However, in spite of the growing number of studies assessing the effects of nutrient supply on algal community structure, the role of nutrient inputs on community invasibility has n...

Synergism between two anthropic impacts: Caulerpa racemosa var. cylindracea invasion and seawater nutrient enrichment

“…Our results agree with other findings (Ceccherelli & Cinelli 1997, Steen 2003, Sánchez & Fernández 2006, Lapointe & Beldford 2010, indicating that the spread of some species of non-native macroalgae in the oligotrophic regions can be favored by nutrient enrichment. The role of eutrophication in aiding invasions of non-native macroalgae must be recognized and more experimental studies on this topic are needed in order to predict the con sequences of possible synergisms between these aspects of global change and to identify appropriate strategies to effectively manage the phenomenon in the future.…”

“…Mar Ecol Prog Ser 427: 59-70, 2011 60 logical invasions has been examined mainly in terrestrial habitats (Burke & Grime 1996, Gross et al 2005, Leishman & Thomson 2005; in contrast, only a few experimental studies have been carried out to investgate this phenomenon in marine ecosystems (but see Steen 2003, Sánchez & Fernández 2006, Incera et al 2009). Eutrophication is a growing problem in the marine habitats of coastal waters all over the world (Nixon 1995, Livingston 2001, Howarth & Marino 2006 and is considered one of the main causes of deteriorating coastal water quality and loss of ecosystem complexity (Soltan et al 2001, Arevalo et al 2007).…”

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

“…For example, Britton-Simmons (2006) showed that space pre-emption by low-lying algae inhibited recruitment of the invasive fucoid alga Sargassum muticum and that light reduction by canopies reduced its survival. Similarly, Sánchez & Fernández (2006) found that bare space and increased nutrients facilitated establishment and spread of S. muticum. The suppressive role of lowlying algae found in these and other studies may well relate to the different attachment dynamics of fucoids, such as S. muticum, with quick attachment and direct development of 2N propagules (e.g.…”

“…The timing of gap creation or disturbance is also important, with maximum recruitment of the invader occurring when the disturbance was just prior to its reproduction season (Valentine & Johnson 2003, Incera et al 2010, Airoldi & Bulleri 2011. However, little work of this nature has been done in the intertidal zone (but see Sánchez & Fernández 2006, Incera et al 2010, which is modulated not only by algal canopies but also by often harsh and extreme physical conditions.…”

Environmental control of the annual erect phase of <i>Nemalion helminthoides</i> (Rhodophyta) in the field

“…On the coast of N Spain (43°34'N) these conditions are found around mid-May when N. helminthoides starts to colonize the upper faces of intertidal rocky boulders, at the lowest nutrient levels of the year (Rico and Fernández, 1996;Martínez and Rico, 2002;Sánchez and Fernández, 2006). Other seaweeds also follow this kind of cycle, such as many Porphyra species (Lubchenco andCubit, 1980, Hernández et al, 1993;Pedersen et al, 2004), the sea palm Postelsia palmaeformis (Blanchette, 1996), and the brown seaweed Desmarestia ligulata (Dayton et al, 1992, Edwards, 2000.…”