TROPICAL MARINE HERBIVORE ASSIMILATION OF PHENOLIC-RICH PLANTS

Phenolics in marine brown algae have been thought to follow a latitudi nal gradient with high phenolic species in high latitudes and low phen olic species in low latitudes. However, tropical brown algae from the western Caribbean have been shown to be high in phlorotannin concentra tion, indicating that latitude alone is not a reasonable predictor of marine plant phenolic concentrations. This study shows that the range of high phenolic phaeophytes is not limited to the western Caribbean b ut encompasses the western tropical Atlantic, including Bermuda and th e Caribbean, where algal phlorotannin concentrations can be as high as 25% dry weight (DW). Assimilation efficiencies (AEs) of phenolic-rich and phenolic-poor plants were examined in three tropical marine herbi vores (the parrotfish, Sparisoma radians, and the brachyuran crab, Mit hrax sculptus, from Belize and the parrotfish, Sparisoma chrysopterum, from Bermuda). AEs of phenolic-rich food by each of the three herbivo re species were uniformly high, suggesting that high plant phenolic co ncentrations did not affect AEs in these species. This is in contrast to some temperate marine herbivores where phenolic concentrations of 1 0% DW have been shown to drastically reduce AE. The apparent contradic tion is discussed in light of the effects of specific herbivore gut ch aracteristics on successful herbivory of high phenolic brown algae.