Spatio-temporal variability in the Cladocera assemblage of a subtropical hypersaline lagoon

Abstract

Cladocera represent an important zooplankton group because of their seasonal prominence in terms of abundance and their contribution in controlling primary production (phytoplankton). On a global scale, there are few studies on Cladocera in hypersaline environments. The present work aims to evaluate the spatio-temporal variation of the Cladocera assemblage across a salinity gradient in the habitats of the Araruama Lagoon. Samples were collected in random months over a period of four years at 12 fixed stations in the Araruama Lagoon using a WP2 plankton net equipped with a flow meter. Our results do not reveal significant influence of the tide and seasonal variation as factors affecting the Cladocera assemblage. Five Cladocera species were found in the Araruama Lagoon, only in stations 11 and 12 where they reached an average of 1,799 ± 3,103 ind. m-3. The mean of the Shannon Diversity Index was 0.45 ± 0.2. The species that stood out in terms of frequency and abundance were: Penilia avirostris (frequency of occurrence: 71%), followed by Pseudevadne tergestina (41%). The same species also stood out in terms of relative abundance, Penilia avirostris (87%) and Pseudevadne tergestina (11%). The absence of Cladocera in the innermost parts of the lagoon suggests that their entrance to these locations is possibly inhibited by the salinity and temperature gradient of the lagoon, being the main factors influencing the dynamics of the Cladocera assemblages.

Characterization and distribution of Teredinidae assemblage in an estuary in Ceará, Brazil's Northeast

“…However, considering the abundance, the highest values were found at Site 3, further away from the estuary mouth, differing from the observations of several authors (Barreto et al, 2000;Junqueira et al, 1989;Lopes and Narchi, 1993), who observed a decreasing infestation with increasing distance from the mouths of the rivers, highlighting the role of salinity in the distribution of teredinids in this environment. Similar results were observed by Rosa et al (2020) in studies carried out at Lagoa Araruama in Rio de Janeiro where the absence of Cladocera was attributed to the high level of salinity inside the lagoon. The salinity condition observed in the dry period of the region, as well as the predominance of euryhaline species, such as Nausitora fusticula and Neoteredo reynei, seem to determine this differentiated condition in the Acaraú River estuary.…”

Effects of environmental factors on ichthyoplankton in a permanently open estuary under the influence of a semi-arid climate, north-eastern Brazil

“…Several authors have suggesting that local variables are important predictors that influence the distribution patterns of estuarine ichthyoplankton (Harris et al ., 2001; Kimmerer, 2002; Lima et al ., 2015; Machado et al ., 2017; Zhang et al ., 2019). In particular, salinity is one of the most important factors that influence egg survival and larval distribution because it affects metabolism through osmoregulation and oxygen demands (Rosa et al ., 2016).…”

“…Several authors have suggesting that local variables are important predictors that influence the distribution patterns of estuarine ichthyoplankton(Harris et al, 2001;Kimmerer, 2002;Lima et al, 2015;Machado et al, 2017;Zhang et al, 2019). In particular, salinity is one of the most important factors that influence egg survival and larval distribution because it affects metabolism through osmoregulation and oxygen demands(Rosa et al, 2016).In tropical areas, levels and ranges of environmental variables can be largely determined by the seasonal rainfall patterns(Blaber, 2002). Ichthyoplankton density patterns may consequently respond to the hydrologic regime(Pringle, 2003).…”