Phytoplankton Genera Structure Revealed from the Multispectral Vertical Diffuse Attenuation Coefficient

The composition of phytoplankton and the concentration of pigments in their cells make their absorption and specific absorption coefficients key parameters for bio-optical modeling. This study investigated whether the multispectral vertical diffuse attenuation coefficient of downward irradiance (Kd) gradients could be a good framework for accessing phytoplankton genera. In situ measurements of remote sensing reflectance (Rrs), obtained in an Amazon Floodplain Lake (Lago Grande do Curuai), were used to invert Kd, focusing on Sentinel-3/Ocean and Land Color Instrument (OLCI) sensor bands. After that, an analysis based on the organization of three-way tables (STATICO) was applied to evaluate the relationships between phytoplankton genera and Kd at different OLCI bands. Our results indicate that phytoplankton genera are organized according to their ability to use light intensity and different spectral ranges of visible light (400 to 700 nm). As the light availability changes seasonally, the structure of phytoplankton changes as well. Some genera, such as Microcystis, are adapted to low light intensity at 550–650 nm, therefore high values of Kd in this range would indicate the dominance of Microcysts. Other genera, such as Aulacoseira, are highly adapted to harvesting blue-green light with higher intensity and probably grow in lakes with lower concentrations of colored dissolved organic matter that highly absorbs blue light (405–498). These findings are an important step to describing phytoplankton communities using orbital data in tropical freshwater floodplains. Furthermore, this approach can be used with biodiversity indexes to access phytoplankton diversity in these environments.

A new tribe, two new genera and three new species of Cypridopsinae (Crustacea, Ostracoda, Cyprididae) from Brazil

We describe one new tribe, two new genera and three new species of the subfamily Cypridopsinae Kaufmann, 1900 from Brazilian floodplains. Brasilodopsis gen. nov. belongs in the nominal tribe Cypridopsini, and both new species in this new genus were found in both sexual and asexual populations. Brasilodopsis baiabonita gen. et sp. nov. has a wide distribution and was found in three of the four major Brazilian floodplains. Brasilodopsis amazonica gen. et sp. nov. was recorded only from the Amazon floodplain. Brasilodopsis baiabonita gen. et sp. nov. has a subtriangular shape in lateral view, whereas Brasilodopsis amazonica gen. et sp. nov. is more elongated and has more rounded dorsal margins in both valves, as well as more pronounced external valve ornamentation, consisting of rimmed pores in shallow pits. Paranadopsis reducta gen. et sp. nov. was found in asexual populations in the Upper Paraná River floodplain only and differs from other Cypridopsinae in the more elongated carapace, an A1 with strongly reduced chaetotaxy (hence the specific name) and the total absence of caudal rami in females. Because of these strong reductions in valve and limb morphology, Paranadopsini trib. nov. is created within the Cypridopsinae for this intriguing new genus and species.