Abstract. BACKGROUND: Pain sensitivity has been negatively associated with physical activity levels. Few studies have examined associations between experimentally induced pain sensitivity and physical activity in adults with chronic low back pain and painfree controls. OBJECTIVE: The objective of this study was to examine associations between physical activity levels and how an individual processes pain using experimentally induced pain stimuli. METHODS: Seventy subjects (CLBP = 49; mean age = 46.8 ± 14.9; Pain-free = 21; mean age = 45.3 ± 18.2, n of females = 46) participated. A self-report questionnaire derived from the International Physical Activity Questionnaire (IPAQ) was used to calculate an activity level index. Pain sensitivity was assessed via quantitative sensory testing (QST) at the right lower extremity. RESULTS: Moderate (U = 688, p < 0.05) and vigorous (U = 649, p < 0.05) physical activity levels were higher in pain-free vs. individuals with CLBP. Activity level was not associated with pain sensitivity (Pain-free: R2 = 0.02, p > 0.05; CLBP: R2 = 0.01, p > 0.05). Both moderate (R2 = 0.49, p < 0.05) and vigorous (R2 = 0.68, p < 0.01) physical activity were associated with pain modulation amongst pain-free individuals. CONCLUSIONS: Findings suggest that physical activity influences pain modulation amongst pain-free individuals, however no relationship exists once CLBP is present. However, future investigation will elucidate the extent to which physical activity level either prevents CLBP or is effective in alleviating CLBP.

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Whether the non-native seaweed Sargassum muticum can displace or impact native eelgrass Zostera marina has been debated in the literature, based on differing substrate requirements of the 2 species. Field observations in Bamfield, British Columbia, Canada, revealed that the non-native S. muticum successfully inhabits an eelgrass bed through colonizing siphons of the native clam Tresus capax. Numerical or physical facilitation of S. muticum into the eelgrass bed by T. capax may be tempered by seaweed quality or condition. We used field sampling to investigate whether seaweed condition differs between 2 attachment substrates (clam siphon and rock) as a proxy for habitat quality. Attachment substrate promoted different morphologies of S. muticum; individuals attached to clam siphons expressed morphologies consistent with sheltered areas compared to individuals attached to rock, which expressed wave-exposed morphologies. Habitat association with the different morphologies supported differences in the epibiont communities colonizing S. muticum. Further, S. muticum subsequently facilitated incursion of the non-native tunicates Styela clava and Botrylloides violaceous into the eelgrass bed through habitat provisioning. By facilitating 2 additional invaders, S. muticum enhances the level of invasion in the eelgrass bed. This non-native seaweed has the potential to disrupt the persistence of eelgrass in this system. KEY WORDS: Sargassum muticum · Zostera marina · Non-native species · Facilitation · Tresus capax Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 424: [87][88][89][90][91][92][93][94][95] 2011 Despite the ecological and environmental importance of eelgrass beds, their decline has been observed in many areas of the world, i.e. Florida Bay in North America (Fourqurean & Robblee 1999), Japan (Environment Agency of Japan 2000), the European Mediterranean (Marbà et al. 2005), and Australia (Walker et al. 2006). Over the last decade, 90 000 ha of eelgrass loss has been documented, although the actual area lost is certainly greater (Short & WyllieEcheverria 1996). Declines have been attributed to (1) disturbance of coastal and estuarine environments, including industrial, residential, and recreational development, where impacts are most notably manifested in the near-absence of eelgrasses in industrialized ports and areas of intense human coastal development (Short & Wyllie-Echeverria 1996, Orth et al. 2006, and (2) the incursion of non-native species (Orth et al. 2006, Martínez-Lüscher & Holmer 2010.We found the non-native seaweed Sargassum muticum (Yendo) Fensholt (Phaeophyceae: Fucales) colonizing an eelgrass bed at the head of Bamfield Inlet, Bamfield, British Columbia. A non-native seaweed from southeast Asia, Sargassum muticum was accidentally introduced to British Columbia around the 1940s with Japanese oysters Crassostrea gigas that were imported for aquaculture (Scagel 1956). Sargassum muticum is both a fouling species and an opportunist (Critchley...