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This study concerns the distribution of nereid Hediste diversicolor in the Middle Pomerania, near the estuaries of five rivers (Parsęta, Wieprza, Słupia, Łupawa and Łeba). The highest density of Hediste was observed in the vicinity of the Wieprza estuary while the lowest (7-fold lower) in the estuary of the Łeba River. As for biomass, it was the highest in the river mouth of Parsęta and the lowest in the Wieprza estuary. Frequency in the studied estuaries was low and amounted to 32%. Using standard statistical methods (significance tests) we indicated differences in average Hediste density and biomass between the eastern and western transects. Nereid’s density was 2-fold higher in the eastern transects while biomass in western. The applied multivariate regression and classification tree method (MR&CT) revealed that the density of Hediste was determined only by the depth of a sampling site while biomass by the distance from the coast. The Spearman’s correlation coefficient analysis indicated significant (p < 0.05) dependence of biomass and density on depth and distance from the shore. Due to ecological role of H.diversicolor as a food source for benthivorous fish, including valuable and endangered species (cod, flatfish), the analysis of food supply can be important in the identification of fish feeding grounds.
In order to estimate the impact of flow manipulations on abiotic and biotic variables two sites of the fourth-order section of a lowland river (Drzewiczka River, in central Poland) with five dominant habitats each were selected downstream of a dam reservoir: the former just downstream of a canoeing track (CT), marked as disturbed (D), and the latter, control one (C), 10 km farther downstream. At the disturbed site water from the reservoir was released in afternoons to operate the CT (3–5 times higher volume than the natural median, i.e. from 4.3 (most frequently) to over 12.0 m⁻³ s⁻¹ (exceptionally), which lasted for 2–3 hours per day while no flow fluctuations were observed in the control. The habitats were sampled over an annual cycle. Variables that have a great impact on macrozobenthos, like current velocity, water depth, substrate composition, presence of macrophytes and standing stock of food resources (BPOM – benthic particulate organic matter, TPOM – transported particulate organic matter, periphyton) were measured. As showed by our results (MANOVA) permanent moderate disturbance caused macrobenthos to be 2–4 times more abundant and diverse at the disturbed site (D), than at nearby natural river site (C), especially at the high-flow area. A lower abundance was recorded at the stagnant and pool habitats of both sites. Chironomidae dominated at all habitats, and Oligochaeta (gathering collectors) at the stagnant and macrophyte habitats; Trichoptera (mainly filtering collectors), Ephemeroptera and Simuliidae (filtering collectors) were the next most abundant among insects, depending on the habitat type. Although Chironomidae dominated at both river sites, they were represented by taxa belonging to various functional feeding groups; at site D chironomids – mainly periphyton scrapers (Orthocladiinae), while at site C – deposit feeders (Chironomini), connected with either silt sediment or sand.
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Antarctic benthic fauna in the global climate change

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An important question stated in the presented paper is: Could rotifers be the indicators of climate change in the Antarctic environments? Rotifers are one of the most important components of the invertebrate fauna of the Antarctic freshwater and terrestrial ecosystems. However, investigations of their distribution, diversity and an ecological role in the environment have been widely neglected, mainly due to the methodological and taxonomical difficulties. During the investigations 176 species of rotifers were found, including the endemic and cosmopolitan species. Their existence is directly proportional to microvariations of humidity factor. Scientists still have poor knowledge about the occurrence of rotifer species in recently studied habitats e.g. cryoconite holes, nunataks or soil. Probably rotifers could be the indicators of climate change in the Antarctic freshwater and terrestrial ecosystems but more investigations and monitoring studies are needed.
The biotic diversity of springs is specific, which makes them valuable sites important for nature protection. Springs located in the Krakow-Częstochowa Upland (southern Poland) are characterized by low variability of environmental conditions, but their benthic fauna composition is considerably different. Benthic invertebrates, water chemistry as well as sediment characteristics of 25 springs were studied four times in 2003. The relationships between fauna composition and abiotic parameters were ascertained using multivariate statistical analyses. In total, fifty families or subfamilies and four higher taxa of invertebrates were identified in the springs studied. Only Gammarus fossarum (Amphipoda) occurred in all of the springs, whereas crenophilic taxonomic groups such as Turbellaria, Bythinellinae, Nemouridae, Limoniidae, Limnephilidae and Enchytraeidae as well as ubiquitous taxa such as Tubificidae and Chironomidae were very common but not present in all springs. Important factors determining differences in the taxonomic composition (at the family level) of the invertebrate fauna of springs were found to be those connected with their geographical location as well as chemical and discharge parameters, which were different for southern and northern groups of springs. The taxonomic richness, i.e. the number of invertebrate taxa, was found to be strongly dependent on discharge and the content of organic matter in bottom sediments, whereas specific taxa mentioned above had other abiotic determinants such as alkalinity, NO3 and temperature.
There have been very few quantitative studies of the intertidal and shallow water biota of the Andaman Coast of Thailand and thus it was very difficult to provide precise estimates of the impact of the tsunami on coastal resources. Some quantitative data from Laem Son National Park existed, having been collected by the present authors, and these indicated that the most severe impacts were on the intertidal sand beach fauna, on rocky shore assemblages and on the seaward edge of mangrove forests. Inside the forests there was heavy deposition of coarse sediment on the forest floor and this led to changes in the species composition of the infauna. Most, but not all, sea grass beds escaped serious damage. By 2008 intertidal sediment assemblages contained a similar number of individuals to that recorded before the tsunami. Pre-tsunami data indicate that open coast, estuarine and seagrasses assemblages are naturally highly variable and thus were well adapted to recovering from the tsunami disturbance. Offshore sediments lack pre-tsunami information, but they too appear to be normal. Size frequency analysis of a population of the heart urchin Brissopsis luzonicus indicate that some individuals survived the tsunami but that there is heavy domination by the first post-tsunami cohort suggesting heavy colonization of disturbed seafloor. The trees in the seaward fringe of the most exposed mangrove forests still have to recover from tsunami damage, although the benthic fauna within the forest has returned.
The food composition of small common bream, roach, pikeperch and ruffe was studied in the shore area of the Włocławek Reservoir between July and October 1999. Zoobenthos and pelagic Chironomidae pupae dominated. Rotifers, copepods and cladoceran pelagic zooplankton were almost not consumed at all. Common bream fed mainly on benthic cladoceran Chydoridae and Chironomidae larvae. Roach consumed vegetation, Chironomidae larvae and small molluscs Sphaeriidae. Ruffe ate Chironomidae larvae, and pikeperch ate fish and various developmental stages of Chironomidae. Pelophilous chironomid forms, mainly from the genus Chironomus, dominated among the consumed larvae. Due to its exceptional abundance, the benthic fauna in the Włocławek Reservoir is an attractive food source for fish, and it plays an important role in their diet from the earliest life stages onwards. The benthic fauna also provides good developmental conditions, especially for typical benthic feeders.
The zebra mussel, Dreissena polymorpha (Pall.) inhabits various live and dead substrates of the lotic and lentic zones of the heated Konin lakes. Occurring at depths from 20 cm to 3.5 m, this species showed a preference for Unionidae mussels as a substrate. Aggregations of D. polymorpha varied in number from 2 000 to 2 million individuals per m², while the biomass reached more than 12 kg m⁻² . The most numerous were one year old mussels 5 mm in length, which comprised from 60 - 80% of the population. In the preliminary cooling reservoir, newly settled post-veligers comprised as much as 94% of the total of D. polymorpha numbers. The largest mussels did not exceed 35 mm. Aggregations of D. polymorpha contained 49 invertebrate taxa, and the most frequently occurring subdominants were from the Corophidae and Gammaridae families. The diel destruction of organic matter in the aggregations varied between 20 and 370 kJ m⁻² , depending on the number of animals and their biomass. The turnover coefficient (R/B) in the heated zones was 1.5 times higher, on average, than in the non-heated parts of the system.
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