Meeting Abstract

S1-1.5  Jan. 4  Ecomechanics of macroalgal spore dispersal in coastal environments: Insights from theory and experiment GAYLORD, B*; REED, D.C.; RAIMONDI, P.T.; WASHBURN, L.; Univ. of California, Davis; Univ. of California, Santa Barbara; Univ. of California, Santa Cruz; Univ. of California, Santa Barbara bpgaylord@ucdavis.edu

Passively dispersing propagules are often transported across a range of scales, with impacts on both local and regional population processes. In Macrocystis pyrifera, the giant kelp, patterns of spore dispersal influence rates of self-fertilization and inbreeding depression as well as levels of connectivity among forests. We used a combination of theoretical and experimental approaches to examine short- and long-distance spore dispersal in this important foundation species. Results of a physically based model were compared to settlement data acquired using spore collectors positioned around solitary kelps and an experimental kelp forest. Findings indicate that short-distance dispersal patterns quantified over brief durations are noisy due to stochastic effects of turbulence. Waves also smear dispersal distributions, reducing distinctions between point sources (i.e., solitary kelps) and area sources (i.e., forests composed of spatially distributed individuals). Temporally averaged dispersal distributions follow a lognormal-Gaussian form explicitly coupled to current speed. Functional expressions that describe such patterns provide additional first-order benchmarks. They suggest tremendous rates of spore release, exceeding 100 million spores per individual per day. Fertilization and recruitment appear possible at distances beyond 1 km, modulated by current speed, forest size, and the duration of viability of gamete-producing life stages derived from spores. Within forests where settlement is high, levels of self-fertilization may reach 10% or more. Such characteristics influence propagule supply, population connectivity, and inbreeding in this key nearshore seaweed.