TheUlvaspp. Conundrum: What Does the Ecophysiology of Southern Atlantic Specimens Tell Us?

Species of the genusUlvaare common in anthropogenically disturbed areas and have been reported as the cause of green tides in many areas of the world. In addition, they rank among the main marine groups used in a wide range of commercial applications. By displaying few distinctive morphological characters, some taxonomical identifications are difficult and the genus is under a conundrum. Our aims were to provide ecophysiological information about threeUlvaspecies in response to abiotic factors and to evaluate the proposal of ecophysiological information and the chlorophyll-afluorescence technique as auxiliary tool to resolve the long-standing taxonomic confusion. We hypothesize that three cooccurring specimens (U. fasciataDelile,U. lactucaLinnaeus, andU. rigidaC. Agardh) have different ecophysiological responses (as measured by the effective quantum yield of photosystem II by pulse amplitude modulated fluorometers) under manipulated conditions of temperature and nutrient concentration.Ulva lactucaandU. rigidashowed different photosynthetic efficiencies related to temperature, whereas no difference was recorded forU. fasciataindividuals. These results provide a reasonable explanation for the variability in spatial and temporal abundance of these species ofUlvaon rocky shores. We proposed the use of ecophysiological information by chlorophyll-afluorescence as an auxiliary tool to corroborate the taxonomic distinction ofUlvaspecies. We reinforce the statement ofU. fasciataandU. lactucaas distinct valid species.