Macrozoobenthos

The intensive use of the European rivers during the last hundreds of years has led to profound changes in the physico-chemical properties, river morphology and aquatic faunistic communities. Rectifying these changes and improving the ecological state of all surface water bodies is the central aim of the European Water Frame Directive and river revitalization measures are the main tool to achieve this goal for many rivers. The research presented here provides essential and in-depth data about the effects of two such revitalization measures on the riverbed morphology and the ecological quality assessment based on the macrozoobenthos fauna. The results show a high spatial and temporal diversity and dynamic for all analyzed morphologic parameters – ranging from the riverbed sediments, organic structures like dead wood or macrophytes to the distribution of (micro-)habitat types. The structures and their dynamic depend on the character of the study area (free-flowing or impounded), the location of the study sites (in the main channel or in the revitalized side channels) and on the occurrence of major flood events. The high morphological diversity as a result of the river restoration however is not reflected in the evaluation of the ecological river quality based on the macrozoobenthos. This might be caused by the large scale impacts of the impoundment in the Lahn river catchment and by the inadequacy of the reference conditions used for the assessment and questions the value of the nationwide river typology with clearly defined and binding reference conditions. It also calls for a modified or extended assessment tool for a reliable evaluation of rivers in the transition zone between mountain rivers and lowland streams.

(The fulltext is in German with an English summary)

В теплый период года исследованы состав и структура фитоконсорций эстуариев двух
разнотипных рек. В эугалинном эстуарии р. Суходол детерминантами консорций выступали различные виды водорослей (ульва, кладофора, ризоклониум). В мезогалинном эстуарии р. Гладкой — травы (рдест, роголистник и руппия). В первой реке в составе консортов пре- обладали амфиподы и брюхоногие моллюски (94 % по массе). Во второй, кроме амфипод и брюхоногих (69 %), существенную долю составляли изоподы, а также полихеты и на- секомые. Биомасса животных-консортов была выше при более высокой солености воды и биомассе растений-детерминантов. Сезонная динамика обилия консортов определялась процессами колонизации ими нарастающей растительности (в первую очередь их моло- дью). Максимум биомассы как растений, так и животных в эстуарии р. Суходол отмечен в июле на фоне максимального прогрева воды. В августе 2011 г. во внутреннем эстуарии р. Суходол общая биомасса дночерпательного макрозообентоса составила 7,5 т, запас до- минирующих видов растений — 34,2 т, общая биомасса животных, ассоциированных с растениями, — 2,1 т. Во внутреннем эстуарии р. Гладкой эти величины составили соответственно 138,8, 719,0 и 11,6 т.

A list of species composition and seasonal dynamics of macrozoobenthos in the
Azerbaijan sector of the South Caspian shelf zone is provided. In 2011 - 2012 152
species of macrozoobenthos belonging to 15 taxonomic groups was found, by the
number of species mollusks (50 species) dominated, amphipods were at the second
place (44 species). In this zone of the sea for the first time 54 species of
macrozoobenthos were found by us. The maximum number of species observed in the
spring and summer season (137 - 152 species), the minimum - in the autumn season
(123 - 131 species). The average annual biomass of macrozoobenthos varied in the
range 155.54 - 176.12 g/m2, the number was 1175 -. 1420 ind/m2. Maximum
development of organisms observed in summer (192.46 g/m2), minimum - in autumn
(134.78 g/m2). In all seasons shellfish dominated by biomass (69.3 - 72.9 % of the total
benthic fauna biomass). The main role in the formation of benthos play 10
macrozoobenthic species, where shellfish dominated by biomass. Their biomass in 2011
amounted to 72.58 % and in 2012 70.91 % of the total biomass of benthos. The second
place is occupied by decapods (12.74 % - 13.01 % of the total biomass).

The present study deals with macrozoobenthic species on soft substrates in İğneada (Turkish coast of the Black Sea). Benthic samples were collected seasonally at three stations between 2012 and 2013. A total of 155 species belonging to seven taxa (Turbellaria, Nemertea, Nematoda, Oligochaeta, Polychaeta, Crustacea, Phoronida, Mollusca, Hemichordata) were identified. Of these, four species are new records for the Black Sea fauna, 15 species are new to the Turkish coast of the Black Sea; and two species are new to the Turkish Seas. Polychaeta was the most representative taxon in the study area – it was represented by 58 species (39% of the total number of species). In terms of the number of individuals, Mollusca were the dominant taxon in all seasons (82% of the total number of individuals). The most dominant species were Bittium reticulatum and Caecum trachea and the most frequent species were Micronephtys stammeri, B. reticulatum and Chamelea gallina.