Effects of Oxbow Reconnection Based on the Distribution and Structure of Benthic Macroinvertebrates

Abstract

This study focuses on the assessment of relationships between flow and macrozoobenthos structure that was performed in a reconnected oxbow lake located in the Sl / upia River floodplain (northern Poland). The lake was created during river straightening at the beginning of 20th century by cutting off the right-bank meander. The oxbow restoration was performed to enhance the ecological viability of this water body and restore riverine wetland. In July 2000 the oxbow was connected with the river channel through PVC pipes which enabled free water movement. Macrozoobenthos sampling, as well as chemical analyses of water and hydrological measurements, took place both before and after the oxbow reconnection. Before the oxbow reconnection, the dominant species was Asellus aquaticus, whereas after the reconnection the structure of benthic species changed significantly. During the first year it was replaced by bivalves and Chironomidae larvae and then A. aquaticus. After the reconnection, macrozoobenthos mean density was 5-fold higher and the mean wet biomass was 77-fold higher than before the reconnection. The number of taxa increased from 4 before the oxbow reconnection to 17 during the first year after the performed works and 20 in the next year. We stated that the revitalization process of the reconnected oxbow lake has longterm consequences for the benthic communities. The most significant feature of the oxbow reconnection is the qualitative and quantitative recolonization by riverine macrozoobenthos species. The performed restoration significantly improved ecological status of the oxbow lake by the increase in biodiversity and water quality.

Status of Macrobenthic Community and Its Relationships to Trace Metals and Natural Sediment Characteristics

“…Therefore, the macrobenthic community composition in Laizhou Bay has undergone a tremendous change in the past three decades. The dominance shifts are likely a direct result of anthropogenic stressors [6]. The important phyla of Laizhou Bay were mainly mollusca and annelida in 2011 (Table 3), whereas mollusca and echinodermata were dominant in 1982 [22].…”

“…In addition, they are relatively sedentary and have long life spans, subjecting them to long-term exposure to different sources of disturbance and pollutants of both natural and human origins [2,3]. They have been widely introduced as biological indicators of habitat conditions in marine and estuarine environments to assess water quality and ecological risk assessments for their physiological sensitivity [4][5][6].…”

“…Capitella capitata, a representative opportunistic polychaete, is short lived, matures rapidly and has a high reproductive output. Planktonic and macrobenthic larvae are both food supplements for C. capitata, which can develop in great quantities in a short period of time and play a major role in macrobenthic community succession in soft-bottom habitats [6,7]. Amphipods build and irrigate their burrows or tubes in previously anoxic sediment, creating small oxidized cylinders within the sediment that allow sea-bottom oxygenation and nitrification processes.…”

Biodiversity of Macroinvertebrates in Oxbow-Lakes of Early Glacial River Basins in Northern Poland

“…Benthofauna structure in lentic oxbow-lakes depended on the specific features of consecutive river basins. In the Drwęca River Basin the inflow of fresh water occurs during floods and therefore benthofauna was predominated by taxa resistant to low oxygen concentration in water-some of the Diptera larvae (Mikulski, 1974;Stańczykowska, 1986 (Obolewski, 2011b). As a result, benthofauna abundance is higher with the domination of Oligochaeta and Crustacea.…”

Lateral and longitudinal patterns of water physico-chemistry and trace metal distribution and partitioning in a large river floodplain

“…The re-connection of the floodplain with the main river is often a major aim in river restoration projects (Gregory, 2006;Lamouroux et al, 2015;Muhar et al, 2016). Such reconnections influence water chemistry (Obolewski and Glińska-Lewczuk, 2011) but their influence on trace metal mobilization is not well studied. As the quality of water and sediment have been described to play a role in the success of river restoration projects (Bednarek, 2001), the characterization of physico-chemical parameters and trace metal distribution and partitioning along gradients of lateral and longitudinal connectivity is expected to provide valuable insights into the general geochemistry of floodplains and carries potential implications for river restoration.…”