Reconstructing Missing and Anomalous Data Collected from High-Frequency In-Situ Sensors in Fresh Waters

In situ sensors that collect high-frequency data are used increasingly to monitor aquatic environments. These sensors are prone to technical errors, resulting in unrecorded observations and/or anomalous values that are subsequently removed and create gaps in time series data. We present a framework based on generalized additive and auto-regressive models to recover these missing data. To mimic sporadically missing (i) single observations and (ii) periods of contiguous observations, we randomly removed (i) point data and (ii) day- and week-long sequences of data from a two-year time series of nitrate concentration data collected from Arikaree River, USA, where synoptically collected water temperature, turbidity, conductance, elevation, and dissolved oxygen data were available. In 72% of cases with missing point data, predicted values were within the sensor precision interval of the original value, although predictive ability declined when sequences of missing data occurred. Precision also depended on the availability of other water quality covariates. When covariates were available, even a sudden, event-based peak in nitrate concentration was reconstructed well. By providing a promising method for accurate prediction of missing data, the utility and confidence in summary statistics and statistical trends will increase, thereby assisting the effective monitoring and management of fresh waters and other at-risk ecosystems.

A new species of the genus Aeolosoma (Annelida: Aphanoneura: Aeolosomatidae) with peculiar sigmoid chaetae from fresh waters of Vietnam

A new species of the Aeolosomatidae, Aeolosoma vietnamicum sp. n., found in freshwater bodies of Vietnam, is illustrated and described. The new species differs from its congeners in the presence of specific sigmoid chaetae in the dorsal and ventral bundles of all segments, beginning from II. These chaetae are characterized by tips with two apical teeth and an additional row of three to nine distinct denticles on the concave side of the chaetae’s distal part. Aeolosoma vietnamicum sp. n. also differs from closely related species in the length, pattern and number of hair chaetae per bundle.

Diversity of mangrove species associated with zonation in Lubuk Kertang Village and Pulau Sembilan, North Sumatra

The Research about the diversity of mangrove species associated with zonation in Lubuk Kertang Village and Pulau Sembilan, Langkat Regency, North Sumatera was conducted in March – April 2021. This study aims to determine the diversity of mangrove species based on zoning observations in Lubuk Kertang Village and Pulau Sembilan. The research was conducted using the exploration method. The observation zone for the diversity of mangrove species is divided into three zones, namely zone 1 in brackish or almost fresh waters behind the actual green mangroves, zone 2 along the river, brackish to almost fresh, and zone 3 on the part facing the sea. The results of the study were fifteen mangrove species with two different mangrove groups, namely four true mangrove species (Lumnitzera racemosa, L. littorea, Nypa fruticans, and Scyphyphora hydrophyllacea) and eleven associated mangrove species (A. auriculiformis, Barringtonia asiatica, Casuarina equestifolia, Hibiscus tiliaceus, Melastoma candidum, Morinda citrifolia, Pandanus odoratatissima, Pongamia. Pinnata, Sesuvium portulcastrum, Stachytarpheta jamaicensis, and Terminalia catappa). Furthermore, the observations in zone 1 were dominated by mangrove association groups, namely A. auriculiformis, B. asiatica, C. equestifolia, H. tiliaceus, M. candidum, M. citrifolia, P. odoratatissima, P. pinnata, S. portulcastrum, S. jamaicensis, and T. catappa, in zone 2, namely L. littorea and L. racemosa and in zone 3, namely N. fruticans and S. hydrophyllacea, zones 2 and 3 are dominated by true mangrove groups. This shows that data on the diversity of mangrove species is very necessary to preserve mangrove species in Lubuk Kertang Village and Pulau Sembilan and the growing zone of mangrove species is natural zoning of mangrove forests.

First Record of the Alien Species Procambarus virginalis Lyko, 2017 in Fresh Waters of Sardinia and Insight into Its Genetic Variability

In the fresh waters of Sardinia (Italy), the non-indigenous crayfish species Procambarus clarkii has been reported from 2005, but, starting from 2019, there have been several reports of a new non-indigenous crayfish in southern and central areas of this Mediterranean island, and its morphology suggests that this species may be the marbled crayfish Procambarus virginalis. Forty-seven individuals of this putative species were analyzed, using the mitochondrial gene Cytochrome c Oxidase subunit I as molecular marker to identify this crayfish and investigate the level of genetic variability within the recently established population. Phylogenetic and phylogeographic analyses were carried out on a dataset including sequences from the Sardinian individuals and from all congenerics available in GenBank. Results showed that the new Sardinian crayfish belong to the species P. virginalis. All the sequences belonging to P. virginalis from European countries are identical, with only few exceptions found among Sardinian individuals. In conclusion, this paper highlights the occurrence of a new further alien species in the Sardinian fresh waters, which are already characterized by the high presence of non-indigenous species.