Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Polish Journal of Ecology

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: aquatic molluscs

Sortuj według:

Ogranicz wyniki do:

Comparative Effects of Aquaculture and Water Level Fluctuations on Macroinvertebrate Communities in Three Gorges Reservoir, China

Chi S., Zheng Z., Zhang Z., Hu J., Zheng J., Zhao X., Hu J., Dong F., Peng J.

Polish Journal of Ecology

2017

Vol. 65, nr 4

390--404

In this study, the comparative effects of the two disturbances (aquaculture and water level fluctuations) on macroinvertebrate communities were explored in two waterbodies connected with the reservoir system of Three Gorges Reservoir (TGR) in China. One water body called Gaoyang Bay which suffered organic pollution from intensive aquaculture. Another named Hanfeng Lake, where the effects of water-level fluctuations are obvious. The results showed that aquaculture could significantly affect the chemical forms of nutrients, decrease the α-diversity and increase the β-diversity of macroinvertebrates although the communities in the treatment area in Gaoyang Bay were not fundamentally changed comparing to the control area in the same bay. The densities of macroinvertebrates in the treatment area were significantly lower than that of the control area. The composition of functional feeding groups in the treatment area was close to that in Hanfeng Lake, but obviously different from that in the control area in Gaoyang Bay and the collectors and predators dominated the communities in this control area with the highest percentages. Although water-level fluctuations had negative effects on the communities by decreasing the α-diversity and increasing the β-diversity, which were confirmed by the values of Simpson index, Shannon-Wiener index and Harrison's index in the control area of Gaoyang bay and Hanfeng Lake, the adverse effects were relative low compared to aquaculture. In the bays of TGR, the small-scale disturbance (aquaculture activities) had more significant negative effects compared to the big-scale disturbance (water-level fluctuations related to dam operation of TGR).

Diversity of Aquatic Molluscs in a Heterogenous Section of a Medium-Sized Lowland River-Floodplain System: An Example of Intermediate Disturbance Hypothesis

Jurkiewicz-Karnkowska E.

Polish Journal of Ecology

2015

Vol. 63, nr 4

559--572

Natural river-floodplain systems are heterogenous mosaics of lotic and lentic habitats subjected to dynamic temporal changes connected with hydrological regime, which promote high biological diversity. Mollusc assemblages of three habitat types within 10 km section of the lower course of the Liwiec River (East Poland) — the main river channel (MC), the secondary channel (SC) and remnants of the former river channel (FC), were compared to find if they were structured by heterogeneity resulting from hydrological connectivity and disturbance intensity related to it. The influence of selected qualitative environmental variables was also analysed. The investigations were carried out at 19 sites during late spring and late summer in the years 2012–2014, molluscs were sampled from approximately 1 m2 of the bottom with a hand net, and from macrophytes with a frame. Rich aquatic malacofauna (36 species including 22 gastropods and 14 bivalves) was found within the study area including three species of special interest: Anisus vorticulus (Troschel), Unio crassus Phillipsson and Anodonta cygnea (L.). Bivalves Sphaerium corneum (L.) and Pisidium spp dominated within MC, in SC a few common and ubiquitous species (mainly snails) prevailed, pulmonate snails and some small bivalves of the genus Pisidium were the most numerous molluscs within FC. Principal Component Analysis revealed that current velocity, channel width, bottom sediments and macrophyte abundance were important environmental factors structuring mollusc assemblages. Considerable variation in species composition (β diversity), especially between the main river channel and two other habitat types (β2) was found. The highest values of mean species richness, Shannon true diversity and Shannon index found in the secondary channel were in accordance with intermediate disturbance hypothesis.