Detecting the impacts of notorious invaders: experiments versus observations in the invasion of eelgrass meadows by the green seaweed Codium fragile.

摘要: Biological invasions can vary in the extent of their effects on indigenous communities but predicting impacts for particular systems remains difficult. In coastal marine ecosystems, green seaweed Codium fragile ssp. is a notorious invader with its reputation based studies conducted largely rocky shores. The has recently invaded soft-bottom eelgrass by attaching epiphytically to (Zostera marina) rhizomes, thereby creating potential disruption these habitats through competition or disturbance. We investigated effect this various aspects performance (shoot density and length, shoot growth, above- below-ground biomass, carbohydrate storage) using both small-scale manipulative large-scale observational experiments. Manipulative experiments that varied abundance demonstrated clear negative over 4-month period reserves, only high, realistic, biomass levels. Light levels were much lower under canopies high medium treatments relative low control cover treatments, suggesting shading may influence growing algal cover. contrast, either not detectable very weak when examined correlatively field surveys at larger spatial scales, even sites had been 4 years. It premature extend generalizations Codium’s impact derived from other communities; further efforts are required assess long-term threats alga poses ecosystem. This study demonstrates need investigate multiple especially those incorporate temporal heterogeneity invader’s abundance.