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The dark false mussel Mytilopsis leucophaeata occurs as non-native species in Asia, Europe and South America. Despite the low population density usually found in its native range, M. leucophaeata forms dense clusters in newly invaded areas which lead to impacts on local organisms and environment. Some of the impacts of non-native species on newly colonized areas may be positive. However, despite the empirical evidences of increase in water transparency by freshwater dresseinids, the hypothesis that dark false mussel enhances the quality of brackish water has never been tested so far. Thus, the present study aimed to determine M. leucophaeata impacts on the water quality of a nutrient-enriched coastal lagoon by (1) analyzing a historical water dataset for pre- and post-invasion at Rodrigo de Freitas Lagoon (Brazil) and (2) experimentally testing dark false mussel direct effects on water quality. Historical field data evidenced significant lower phytoplankton abundance and chlorophyll a, and higher water transparency for the post-invasion period. These pattens were also supported by time-series analyses, which detected a decreasing trend for total coliforms density and an increased trend for dissolved oxygen over time. Moreover, time series indicated a gradual increase in lagoon water level with time, but none or minor changes were evidenced for floodgates operation routine, meteorological variables, and the frequency of sewage input. In microcosms, M. leucophaeata was effective to increase water transparency and decrease E. coli densities. The combination of field and laboratory data partially supported the hypothesis that M. leucophaeata invasion promoted an improvement in lagoon water quality, but increased phosphorus availability through excretion in microcosm assays. Management of dark false mussel populations seems to be a potential strategy for water quality improvement within already invaded systems where high sewage-enriched effluents are released. However, as non-native species often unbalance ecological relationships and functioning of the invaded ecosystems, new introductions of M. leucophaeata must be avoided.

Both title compounds show two fluorescence bands, with maxima at approximately 290 nm and 340 nm in non-protic (hexane, cyclohexane) and protic (ethanol) solvents. Approximate molecular orbital calculations suggest that these two bands can be associated with an excitation partially localized on the anisolyl moiety and a more delocalized excitation, respectively, present in both compounds. In cyclohexane both compounds exhibit a fluorescence band with a maximum at 550 nm, which can be associated with the proton transferred species. In the case of the flavanone this band is very weak and attributed to Excited State Intramolecular Proton Transfer (ESIPT) of the proton at the 5-position. In the flavone the corresponding band is considerably more intense and the theoretical calculations point to the proton being transferred as originating from the 5-position also. In cyclohexane the flavanone exhibits monoexponential decay under the band at 290 nm. In all other combinations solute/solvent/band studied here the fluorescence was found to follow a biexponential decay. In the case of the flavanone these results are interpreted as indicating that the localized anisolyl excitation is not coupled to the delocalized excitation, whereas the decay of the latter is coupled to ESIPT. The time-resolved results of the flavone are interpreted as indicating coupling between all three excited states observed.

— By use of fluorescence spectroscopy and time-correlated single photon counting, solvent-assisted excited-state proton transfer (ESPT) has been observed for olivacine in two organic solvents, 1,4-dioxane and methanol. Because of spectral overlap, factor analysis was used to determine the emission spectrum of the proton-transferred (PT) species. The ESPT is not observed in the nonpolar solvent n-hexane. For the first time in a system of this type, the individual excited-state rate constants have been calculated exactly from time-resolved single photon counting results. Because the PT process involves a path of more than 6 A, its individual rate constant is extremely low, approximately 107 s−1.