Aquatic Ecology Research Article
ACTA ZOOLOGICA BULGARICA Acta zool. bulg., 65 (3), 2013: 337-348
Benthic Macroinvertebrate Diversity in Relation to Environmental Parameters, and Ecological Potential of Reservoirs, Danube River Basin, North-West Bulgaria Teodora Trichkova1, Violeta Tyufekchieva1, Lyubomir Kenderov2, Yanka Vidinova1, Ivan Botev1, Dimitar Kozuharov2, Zdravko Hubenov3, Yordan Uzunov1, Stefan Stoichev1, Svetoslav Cheshmedjiev4 1 Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 2 Gagarin Str., Sofia 1113, Bulgaria, Email:
[email protected],
[email protected]; 2 Biological Faculty, Sofia University, 8 Dragan Tsankov Blvd., Sofia 1164, Bulgaria; 3 National Museum of Natural History, Bulgarian Academy of Sciences, 1 Tsar Osvoboditel Blvd., Sofia 1000, Bulgaria; 4 NGO EcoForum for the Nature.
Abstract: Twelve reservoirs in North-West Bulgaria were sampled in autumn 2009 to study the species diversity and distribution of benthic macroinvertebrates in relation to some environmental parameters, and to assess the ecological potential of the reservoirs based on macroinvertebrate metrics. A total of 75 taxa belonging mostly to Oligochaeta, Ephemeroptera, Chironomidae, and Mollusca were recorded. The most abundant were the invasive bivalve mollusks Dreissena sp., larvae of Ch. crystallinus and oligochaetes. The highest taxa diversity was recorded in the reservoirs located in close proximity to the Danube River and in the reservoirs with the largest areas. The occurrence and abundance of invasive Dreissena species, electrical conductivity, Ca2+ concentration and water transparency were identified as potential factors for the mactroinvertabrate distribution. Based on 7 macroinvertebrate metrics, the ecological potential of the reservoirs was assessed in the range from “Good” to “Bad”. Most of the reservoirs were classified as having a “Moderate” ecological potential. It is recommended that the invasive alien species are considered in the use and development of macroinvetebrate metrics and assessment tools for lakes, and in the river basin and reservoir management strategies. Immediate management actions are crucially needed to improve the ecological potential of reservoirs. Key words: benthic macroinvertebrates, distribution, water physico-chemical parameters, invasive alien species, ecological potential, reservoirs, Danube River Basin
Introduction In lentic freshwaters, the benthic invertebrates play an essential role in key ecosystem processes, such as food chain dynamics, productivity, nutrient cycling and decomposition (Covich et al. 1999). Their distribution and abundance is directly related to different environmental factors such as food availability and quantity, sediment type, substrate, and water quality (Wilhm, McClintock 1978, Bechara, 1996, Jónasson 1996, Real et al. 2000, Arslan et al. 2007, Odabasi et al. 2009). They also
show considerable spatial variation with lake depth, across habitats, and across lakes (Petridis, Sinis 1993, 1995, Di Giovanni et al. 1996, Baudo et al. 2001, Pamplin, Rocha 2007, Smiljkov et al. 2008). In reservoirs, the benthic macroinvertebrate community may be particularly susceptible to water-level changes that alter sediment exposure, temperature regime, wave-induced sediment redistribution and basal productivity (McEwen, Butler 2010). Since benthic invertebrates respond sensitively 337
Trichkova T., V. Tyufekchieva, L. Kenderov, Y. Vidinova, I. Botev, D. Kozuharov, Z. Hubenov, Y. Uzunov, S. Stoichev, S. Cheshmedjiev to pollution, as well as to a number of other human macrozoobenthos diversity and distribution; 4) to asimpacts (hydrological, climatological, morphological, sess the ecological potential of the reservoirs based navigational, recreational, and others), their po- on benthic macroinvertebrate metrics. tential use for a holistic indication system for lake ecosystem health has been considered to support Study Area Twelve reservoirs were sampled. They are EU WFD (2000/60/ЕЕС) implementation (Solimini et al. 2006). In many countries including Bulgaria, located in the Danube River basin, North-West reservoirs are of great economic importance, being Bulgaria (Fig. 1). Information on altitude, size and used for water supply, power generation, water ab- use of the reservoirs is presented in Table 1. straction for agriculture, aquaculture, etc. According to the EU WFD, these heavily modified water bodies should be assessed similarly to lakes, using the best Material and Methods ‘ecological potential’ as a reference. The sampling was made during the period September A comprehensive review of available informa- – October 2009. tion on the benthic fauna of non-lotic water basins Qualitative and quantitative samples of benin Bulgaria was published by Trichkova (2007). It thic macroinvertebrates were collected according to showed that data on the qualitative and quantitative standard methods ISO 9391:1993/ EN 9391:1995 and composition of benthic invertebrate communities in ISO 7828:1985/ EN 27828:1994. The quantitative the standing water basins in Bulgaria by that time were benthic samples were collected with a Petersen’s scarce and fragmentary. Generally, studies concerned grab of medium size (17.0x16.5 cm) at six sites in only single groups or communities of benthic inverte- each reservoir, at different depths (in the range from brates and did not consider the relations between ben- 0.5 to 30 m) and different substrate types. The qualithic invertebrates and other ecological groups, as well tative samples were collected by a hand-net and a as the influence of the environmental factors. Surber’s net (35x30cm) at different substrate types In the North-West Bulgarian reservoirs, Danube in the littoral area (at depths
