Download "Observations on the Digestive Tract Contents of Eel Leptocephalus Sampled in the Western North Pacific Ocean," Tomoda et al., Journal of the Japanese Society of Fisheries Science, (2018).
Eel larvae are found at high densities just below the chlorophyll maximam layer. In that layer, there is a large amount of phytoplankton-derived TEP produced in the surface layer. In addition to TEP-like gel material, many picophytoplankton-like fluorescent particles were found in the digestive tract of eel larvae. Picophytoplankton is a major primary producer in subtropical waters. Their cell membranes are rich in nutrients, for example, they are composed of proteins. However, because the cell size is very small, about 1 to 2 μm, previous studies have thought that only protozoa prey on picophytoplankton. This study suggests that picophytoplankton attach to TEP floating in the ocean surface layer and exist at high density even just below the surface layer, where they become food for eel larvae.
I thought this research is very interesting from the viewpoint of oceanic material cycles.