Influence of wastewater on zooplankton communities in the Daugava River upstream and downstream of Daugavpils over the last 50 years

Abstract

During expeditions to the section of the Daugava River from Surozha in Belarus to Dunava in Latvia in 2008, and during expeditions to the Kraslava-Dunava section in 2009, zooplankton were sampled. Quantitative characteristics, the relation of zooplankton taxonomic groups, the saprobity index and species diversity (Shannon-Wiener index) were employed for the analysis of zooplankton community structure in the Daugava River. The results were compared with the Daugava zooplankton findings of the research carried out by Škute in 1962-1968 in similar sections of the river. Both in 1962Both in -1963Both in and in 2005Both in -2009, the base complex of the Daugava River zooplankton comprised cosmopolitan species; as for the diversity of species, the leading group of organisms was Rotifera. A tendency for decrease in the diversity of species was recorded. Relevant changes were recorded in the structure of taxa. The Daugava River is polluted by Daugavpils' wastewater; however, the untoward influence of pollution on zooplankton is observed only in years and in seasons with low water level and discharge. Decrease in the amount of zooplankton occurs not only in the dominant species, but also in the decrease or even disappearance of oligosaprobes. RÉSUMÉInfluence des eaux usées sur les communautés zooplanctoniques dans la rivière Daugava en amont et en aval de Daugavpils au cours des 50 dernières années Pendant les expéditions à la partie de la rivière Daugava allant de Surozha en Bié-lorussie à Dunava en Lettonie en 2008, et lors des expéditions à la section Kraslava-Dunava en 2009, le zooplancton a été échantillonné. Les caractères quantitatifs, les groupes taxonomiques du zooplancton, l'indice saprobie et la diversité spécifique (indice de Shannon-Wiener) ont été utilisés pour l'analyse de la structure de la communauté du zooplancton dans la rivière Daugava. Les résul-tats ont été comparés avec les résultats des recherches effectuées par Škute en 1962-1968 sur le zooplancton de la Daugava dans des sections similaires de la rivière. En 1962En -1963En comme en 2005En -2009 spécifique, les rotifères arrivent en tête. Une tendance à la diminution de la diversité des espèces a été enregistrée. Des changements significatifs ont été enregistrés dans la structure des taxons. La rivière Daugava est polluée par les eaux usées de Daugavpils, mais l'influence fâcheuse de la pollution sur le zooplancton est observée seulement dans les années et les saisons avec faible niveau d'eau et de décharge. La diminution de la quantité de zooplancton se produit non seulement pour les espèces dominantes, mais aussi par la diminution ou même la disparition des oligosaprobes.

Municipal wastewater can result in a dramatic decline in freshwater fishes: a lesson from a developing country

“…When the water level began to recede, the impact of wastewater pollution on fish abundance and species richness became much more apparent. Evidence of similar impacts of wastewater on zooplankton, the key natural food for many of the fishes, during low water level is available (Deksne, 2011).…”

Evaluation of the Effects of Tigris River Water Quality on the Rotifers Community in Northern Baghdad by using the Canadian Water Quality Index (CCME-WQI)

“…Biological oxygen demand (BOD 5 ) recorded high levels, ranging from 1.3 mg/L in the second site to 8.1 mg/L in the fourth, which is a negatively determining effect on zooplankton [39]. This implies that the river water is questionable in its cleanliness.…”

“…While, the values were from 42 (Poor) to 65 (Fair) during different seasons. As for drinking usages, the results demonstrated poor or undrinkable (31)(32)(33)(34)(35)(36)(37)(38)(39)(40) water in all sites. Meanwhile, the values ranged from 39 (Poor) to 56 (Clear) in regard to seasons.…”

An examination of long-term ecological studies of rotifers: comparability of methods and results, insights into drivers of change and future research challenges

“…Another exception is a study of the zooplankton of the middle Parana River (Argentina) between 1971 and 2007, which found that rotifer numbers declined significantly after 1999 and that there was growing evidence that levels of competition between rotifers and cladocerans were increasing (de Paggi et al 2014). One final example is that of Deksne (2011Deksne ( ), who analysed data collected between 1962Deksne ( and 1968Deksne ( , and between 2005Deksne ( and 2009, from the Duagava River, which lies between Belarus and Latvia. Again, the dominant group of zooplankton in the river was rotifers, and it was noted that there was a tendency for the species diversity of zooplankton in this river to decrease over time.…”

“…These authors found that, although most zooplankton species had remained relatively stable, rotifers had declined markedly (from 40% to 4% of total zooplankton biomass) over the previous 40 years although the reason was unclear. In a study that demonstrated a different response of rotifers to pollution, Deksne (2011) investigated the influence of wastewater on zooplankton of the Duagava River (Balrus/Latvia) by comparing data collected between 1962 and 1968 with that collected between 2005 and 2009 (i.e. before and after a new wastewater treatment plant had been installed).…”