Zoological component of periphyton developed on artificial substrate in Baračka pond (SNR “Gornje Podunavlje”) – diversity and monthly dynamics

Abstract

Periphyton is a complex subcenosis of microorganisms: algae, bacteria, fungi, protists and animals attached on submerged substrates in aquatic ecosystems. Literature data on periphyton are limited, especially those concerning its zoological component. The aim of this research is to present the diversity of zooperiphyton in the area of Baračka pond, by identifying the groups of invertebrates, reveal the monthly dynamics of their abundance and the pattern of ecological succession on the artificial substrate. Sampling is conducted in the eutrophic Baračka pond located near ecological station within SNR “Gornje Podunavlje” in northwest Serbia (Vojvodina province). Physical and chemical parameters were also measured during sampling. The temperature ranged from 14.7 to 30.2°C; and the concentration of dissolved oxygen from 2.5 to 17.6 mg/l. Periphyton was sampled with a specially made construction carrying 45 plexiglass plates. It was anchored far from the shore at a depth of 20 cm. For the purpose of this research, the continuous samples, scrubbed from plates exposed for one up to five months were analyzed. The samples were collected each month from June to October 2018 and fixed in 70% ethanol. After vigorously shaking the sample content to obtain homogenization, a subsample of 1 ml was taken to be analyzed under a trinocular light microscope with a camera, Leica DMLB and using “Leica Application Suite”. A total of 606 invertebrate specimens were identified. Rotifera (57.09%) and Nematoda (35.97%) were represented by the largest number of individuals. The groups Oligochaeta (0.82%), Copepoda (1.32%), Chironomidae (0.66%), and only one specimen of Ostracoda (0.17%) were found in smaller percentages. Nauplii were classified in a separate group and are in third place in terms of share in the total sample (3.96%). Periphyton components also identified during microscoping were silicate algae, individuals of the genera Phacus, Arcella, Vorticella and other ciliates. The largest number of individuals of the most numerous groups Rotifera and Nematoda was recorded in August, whereas the greatest number of nauplii larvae was recorded in September. Other groups were absent in some samples. The climax stage of the periphyton (biomass) development occurred in August and coincided with the most favourable conditions for the development of the most numerous groups. Colonization of the substrate by the groups of invertebrates presented with a lower abundance, such as Chironomidae, may have depended on the type and properties of the surface of the artificial substrate. Interesting topics for the future zooperiphyton studies could be focused on the presence and abundance of different invertebrate groups depending on sampling plate properties and its orientation concerning the gravitational force and the sampling depth.