Implications of warming temperatures for population outbreaks of a nonindigenous species (Membranipora membranacea, Bryozoa) in rocky subtidal ecosystems

Abstract

To quantify and explore the role of temperature on population outbreaks of a nonindigenous bryozoan (Membranipora membranacea) in kelp beds in the western North Atlantic (Nova Scotia, Canada), we constructed an individual-based model using field-derived estimates for temperature-dependent colony settlement and growth. Using temperature as the single input variable, the model successfully simulated the timing of onset of settlement, colony abundance, colony size, and coverage on kelps. We used the model to examine the relative effect on the population of varying temperature by 22uC to +2uC each day. The timing of onset of settlement varied by 18 d uC 21 with changes in temperature from January to August. Variations in temperature had nonlinear effects on the population, with an increase in daily temperature of 1uC and 2uC causing the cover of colonies on kelps to increase by factors of 9 and 62, respectively. Changes in winter and spring temperature had the most pronounced effects on the timing and abundance of colonies, while changes in summer temperature had the most pronounced effect on colony size and coverage on kelp blades. Outbreaks of this species will increase in frequency and intensity if temperatures warm as a result of climate change, causing defoliation of kelp beds and, thus, facilitating the invasion of other nonindigenous benthic species.

Effects of Climate Change on Global Seaweed Communities

“…In kelp beds in eastern Canada, outbreaks of non‐native epiphytic bryozoans are triggered by warming events, and these outbreaks have led to drastic reductions in the percent cover of habitat‐forming Saccharina longicruris (Scheibling and Gagnon , Saunders et al. ). In cases such as this, where bryozoan epibionts increase the risk of frond breakage (Krumhansl et al.…”

The responses of brown macroalgae to environmental change from local to global scales: direct versus ecologically mediated effects

“…2; Hawkins et al 2009), and -enhanced by eutrophicationblooms of epiphytes ("h", "k" in Fig. 2) (Saunders et al 2010), all of which would promote a decline of large brown seaweed species.…”

Physical forcing of distributions of bryozoan cyphonautes larvae in a coastal embayment

“…In the western North Atlantic, a nonindigenous encrusting epiphytic bryozoan, Membranipora membranacea, undergoes significant population outbreaks in kelp beds (Lambert et al 1992, Scheibling et al 1999) during years with warmer than average temperatures (Saunders & Metaxas 2008, Scheibling & Gagnon 2009, Saunders et al 2010. During these outbreaks, colonies of M. membranacea can encrust entire blades of kelps, causing them to become brittle and fragile, and to subsequently break (Dixon et al 1981, Lambert et al 1992.…”

“…Similar distributions and abundances of the 2 species during this sampling period suggest that higher abundances of larvae of M. membranacea, or differences in transport processes between the 2 species, are not responsible for the invasive success of M. membranacea in the western North Atlantic. Rather, it more likely that continuous or repeated spawning events, fast colony growth rates, and the ability to reach large sizes all contribute to the success of M. membranacea (Scheibling & Gagnon 2009, Saunders et al 2010. However, while overall patterns of distribution and abundance of larvae of the 2 species were similar, the earlier occurrence of high proportions of competent larvae, and the presence of multiple cohorts, may contribute to the success of M. membranacea in 418: 131-145, 2010 ephemeral habitats, such as the blades of kelps.…”