Researchers claim they have discovered a new source of microbial mortality in the oceans, shedding light on a crucial aspect of nutrient cycling and ecosystem dynamics. A study conducted by Anne Thompson and colleagues reported that salps, gelatinous filter feeders, play a significant role in determining the fate of marine microbes. Salps, pelagic tunicates that filter particles from seawater using mucous mesh nets, have long been known to act as important nutrient conveyors in the oceans. However, their role in shaping microbial communities and nutrient fluxes had remained largely unexplored until now. By conducting SCUBA dives in the North Pacific Subtropical Gyre, a region characterised by low nutrient levels and dominated by small-cell microbes such as Prochlorococcus, the researchers said they were able to examine the feeding habits and prey preferences of salps. Surprisingly, they said salps did not preferentially consume Prochlorococcus, despite its abundance in seawater. Instead, salps were found to feed on a variety of other microbial taxa including Crocosphaera, Synechococcus, diatoms, and Chrysochromulina. The researchers argued that simple mechanical factors such as particle size or mesh dimensions alone cannot explain the selective feeding behavior of salps. They said: 'This suggests a more complex relationship between salps and their microbial prey. 'The study highlights the crucial role of salps in regulating microbial populations and nutrient cycling in the open ocean, with implications for global nutrient fluxes and ecosystem functioning. 'By clarifying the mechanisms of microbial death and nutrient transfer in the oceans, the research contributes to a better understanding of marine ecosystems and their responses to environmental changes.'