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Kelps are dominant primary producers in temperate coastal ecosystems. Large amounts of kelp biomass can be exported to the seafloor during the algal growth cycle or following storms, creating new ecological niches for the associated microbiota. Here, we investigated the bacterial community associated with the kelp Laminaria hyperborea during its accumulation and degradation on the seafloor. Kelp tissue, seawater and sediment were sampled during a six‐month in situ experiment simulating kelp detritus accumulation. Evaluation of the epiphytic bacterial community abundance, structure, taxonomic composition and predicted functional profiles evidenced a biphasic succession. Initially dominant genera (Hellea, Litorimonas, Granulosicoccus) showed a rapid and drastic decrease in sequence abundance, probably outcompeted by algal polysaccharide‐degraders such as Bacteroidia members which responded within 4 weeks. Acidimicrobiia, especially members of the Sva0996 marine group, colonized the degrading kelp biomass after 11 weeks. These secondary colonizers could act as opportunistic scavenger bacteria assimilating substrates exposed by early degraders. In parallel, kelp accumulation modified bacterial communities in the underlying sediment, notably favoring anaerobic taxa potentially involved in the sulfur and nitrogen cycles. Overall, this study provides insights into the bacterial degradation of algal biomass in situ, an important link in coastal trophic chains.

While population foraging behaviour of herbivores has been extensively studied, individual choice is still poorly understood. Very few studies have focused on the individual consistency of foraging behaviour in marine herbivores. Because marine ectotherms are strongly influenced by their environment and because a mixed diet is appropriate for herbivores, we hypothesized that Haliotis tuberculata, a large marine gastropod, would not exhibit significant individual consistency in foraging activity and would display generalist food choices. To test these hypotheses, the behaviour of 120 abalone was studied using a choice test of eight macroalgal species over 3 weeks, with video recording 24 hr a day. In addition, primary components, secondary metabolites and toughness of the eight algae were measured. At the population level, food choice was mainly related to the protein composition and the toughness of the macroalgae. We found that H. tuberculata is a generalist species feeding on a variety of algae (IS = 0.64), even if 21% of the individuals can be considered to be specialists. However, in contrast to our hypothesis, highly consistent between‐individual variation was observed in foraging activity (ICC = 0.81 for time spent feeding and ICC = 0.74 for number of feeding visits per day). The high individual consistency of foraging activity has some ecological and evolutionary implications currently not understood for this marine herbivore.