Bottom Fauna Research Articles

Консорты брюхоногого моллюска Rapana venosa (Valenciennes, 1846) в северной части Чёрного моря. Часть I: Porifera, Cnidaria, Bryozoa, Chordata

Брюхоногий моллюск-вселенец Rapana venosa (Valenciennes, 1846) в 1940-х занял свободную экологическую нишу терминального хищника в бентосных сообществах шельфа Чёрного моря и стал важным элементом его экосистемы. Способность R. venosa оказывать разрушительное воздействие на биоценозы фильтраторов определяет необходимость постоянного мониторинга состояния популяций этого вида. Однако его экологическая роль не сводится только к хищничеству. Довольно крупная раковина R. venosa служит твёрдым субстратом для водорослей, прикреплённых и малоподвижных (седентарных) бентосных животных организмов, среди которых иногда находят убежище и подвижные свободноживущие формы. Цель работы — описание специфического комплекса эпибионтных организмов на раковине рапаны, который рассматривается как консорция, где R. venosa является ядром. Для изучения консортного сообщества R. venosa были осуществлены сборы рапаны в 7 районах северной части Чёрного моря: 1 — пляж Мамайя, Румыния; 2 — северо-западная часть Чёрного моря (СЗЧМ), Крымский сектор; 3 — Севастополь; 4 — Алупка; 5 — Ялта — Алушта; 6 — Карадаг; 7 — Керченский пролив. Сбор материала в прибрежной зоне (до 15 м) проводился легководолазным способом, на больших глубинах (до 40 м) использовался дночерпатель «Океан-50». Всего было собрано и проанализировано 856 экземпляров R. venosa. Основной объём материала в количестве 750 экз. R. venosa собран в прибрежной зоне г. Севастополя (Юго-Западный Крым) в диапазоне глубин 1.5–10.0 м. Сбор особей рапаны проводили тотально, каждый экземпляр помещали в отдельный пластиковый пакет с указанием района сбора, глубины и биотопа. Параллельно со сбором моллюсков проводили визуальные наблюдения и фотофиксацию гидробионтов in situ. По результатам исследований расширен таксономический список эпибионтных организмов рапаны, впервые приводится таксономический состав подвижных форм, постоянно или временно присутствующих в консорции R. venosa. Представленная первая часть работы посвящена эпибионтам рапаны, относящимся к четырём (Porifera, Cnidaria, Bryozoa, Chordata) из семи обнаруженных типов животных, с указанием глубин обнаружения и типа грунта, а также комментариями по встречаемости, количеству обнаруженных видов и их взаимодействию с ядром консорции. Тип Porifera представлен 1 видом, Cnidaria — 2, Bryozoa — 5, Chordata — 5 видами. Сверлящая губка Pione vastifica обнаружена во всех исследованных районах кроме р-на 2 (СЗЧМ) со встречаемостью от 20 до 90 % и площадью повреждения раковин до 100 % (в среднем 30–35 %). Представители Cnidaria обнаружены единично в р-не 3 (Actinia equina) и в р-не 5 (Diadumene lineata). Мшанки — наиболее распространённая группа животных — консортов рапаны, присутствующая во всех районах исследований. Их встречаемость варьировала от 10 до 100 %, площадь покрытия раковины — от 0 до 85 %. Более 90 % в общей площади покрытия раковин рапаны мшанками и их встречаемости приходится на Cryptosula pallasiana. Вторым по показателям развития видом мшанок является Conopeum seurati, который обнаружен в р-нах 3, 6 и 7, где имел встречаемость до 30 % и площадь покрытия до 25 %. Остальные 3 вида мшанок (Schizomavella auriculata, Bowerbankia imbricata, Hippothoa sp.) встречались редко. Представители Chordata — 2 вида асцидий (Botryllus schlosseri, Ciona intestinalis) и 3 вида рыб (Diplecogaster bimaculata, Parablennius tentacularis, Scorpaena porcus) — зафиксированы единично в р-нах 2, 3, 5. Для рассмотренных четырёх типов животных организмов список консортов R. venosa в биотопе рыхлых грунтов (10 видов) в два раза больше, чем у скальной экоформы (5 видов). Рассмотренные организмы имеют различную степень и характер связей с ядром консорции — от комменсализма до паразитизма. Дана обобщённая информация о водорослевых обрастаниях и суммарном покрытии раковин R. venosa комплексом эпибионтов. Результаты работы показывают, что R. venosa в Чёрном море стала значимым элементом экосистемы, увеличивающим биологическое разнообразие донной фауны за счёт формирования собственных консортивных комплексов эпибионтных организмов.

Use of stable isotopes to understand food webs in Macao wetlands

In this study, components of the food-web in Macao wetlands were quantified using stable isotope ratio techniques based on carbon and nitrogen values. The δ13C and δ15N values of particulate organic matter (δ13CPOM and δ15NPOM, respectively) ranged from −30.64 ± 1.0 to −28.1 ± 0.7 ‰, and from −1.11 ± 0.8 to 3.98 ± 0.7 ‰, respectively. The δ13C values of consumer species ranged from −33.94 to −16.92 ‰, showing a wide range from lower values in a freshwater lake and inner bay to higher values in a mangrove forest. The distinct dietary habits of consumer species and the location-specific food source composition were the main factors affecting the δ13C values. The consumer 15N-isotope enrichment values suggested that there were three trophic levels; primary, secondary, and tertiary. The primary consumer trophic level was represented by freshwater herbivorous gastropods, filter-feeding bivalves, and plankton-feeding fish, with a mean δ15N value of 5.052 ‰. The secondary consumer level included four deposit-feeding fish species distributed in Fai Chi Kei Bay and deposit-feeding gastropods in the Lotus Flower Bridge flat, with a mean δ15N value of 6.794 ‰. The tertiary consumers group consisted of four crab species, one shrimp species, and four fish species in the Lotus Flower Bridge Flat, with a mean δ15N value of 13.473 ‰. Their diet mainly comprised organic debris, bottom fauna, and rotten animal tissues. This study confirms the applicability of the isotopic approach in food web studies.

Delimiting oceanographic provinces to determine drivers of mesoscale patterns in benthic megafauna: A case study in the Barents Sea

Communities of benthic megafauna in the deep waters of continental shelves (> 100m) are important components of marine ecosystems. In high-latitude ecosystems, this fauna is increasingly impacted by human activities and climate variability. In this study, we provide baseline knowledge on the oceanographic conditions affecting its distribution in the Barents Sea in the vicinity of the Polar Front – an oceanic front occurring at the transition zone between the Atlantic and Arctic water masses. We used fields of temperature and currents from an ocean circulation model (Regional Ocean Modelling System – ROMS) to derive variables divided into 3 groups relevant to bottom fauna (temperature, water column structure and bottom currents) expressing either mean conditions or temporal variability over 10years (2001–2010). Benthic megafauna was surveyed in summer 2011 at 139sites. To analyze the relationship between spatial variability in the composition of benthic megafauna (i.e., β-diversity) and oceanographic conditions, we: (1) used generalized dissimilarity modelling (GDM) and (2) delimited oceanographic provinces (i.e., regions of similar conditions) for each group of variables using principal component analysis (PCA) followed by cluster analysis. Turnover in benthic megafauna was explained by 7 oceanographic variables (temperature: 4, water column structure: 2, bottom currents: 1), depth and geographic distance (56.7% of total deviance explained). Concurrently, patterns in oceanographic provinces among the 3 groups of variables coincided with results from the GDM, where provinces derived from temperature were sharply delimited relative to the other groups. We concluded that the spatial structure of the environment is important in the relationship between spatial variability of benthic megafauna and oceanographic conditions in shelf deep waters. Ocean models are powerful tools to study this relationship, but the way in which their inherent uncertainty affects the conclusions of ecological models should be assessed more thoroughly.

Postglacial floodings of the Marmara Sea: molluscs and sediments tell the story

The early Holocene marine flooding of the Black Sea has been the subject of intense scientific debate since the “Noah’s Flood” hypothesis was proposed in the late 1990s. The chronology of the flooding is not straightforward because the connection between the Black Sea and the Mediterranean Sea involves the intermediate Marmara Sea Basin via two sills (Dardanelles and Bosphorus). This study explores the chronology of late Pleistocene–Holocene flooding by examining sedimentary facies and molluscs from 24 gravity cores spanning shelf to slope settings in the southern Marmara Sea Basin. A late Pleistocene Ponto-Caspian (Neoeuxinian) mollusc association is found in 12 of the cores, comprising 14 mollusc species and dominated by brackish (oligohaline–lower mesohaline) endemic taxa (dreissenids, hydrobiids). The Neoeuxinian association is replaced by a Turritella–Corbula association at the onset of the Holocene. The latter is dominated by marine species, several of which are known to thrive under dysoxic conditions in muddy bottoms. This association is common in early Holocene intervals as well as sapropel intervals in younger Holocene strata. It is an indicator of low-salinity outflows from the Black Sea into the Marmara Sea that drive stratification. A marine Mediterranean association (87 species) represents both soft bottom and hard substrate faunas that lived in well-ventilated conditions and upper mesohaline–polyhaline salinities (ca. 25 psu). Shallower areas were occupied by hard substrate taxa and phytopdetritic communities, whereas deeper areas had soft bottom faunas. The middle shelf part of the northern Gemlik Gulf has intervals with irregular and discontinuous sedimentary structures admixed with worn Neoeuxinian and euryhaline Mediterranean faunas. These intervals represent reworking events (slumping) likely related to seismic activity rooted in the North Anatolian Fault system. The core data and faunas indicate an oscillating postglacial sea-level rise and phases of increased/decreased ventilation in the Marmara Sea during the Holocene, as well as palaeobiogeographic reorganisations of Ponto-Caspian and Mediterranean water bodies since the latest Pleistocene (<30 ka). The findings contribute to arguments against a single catastrophic flooding of the Black Sea at about 7.5 ka (Noah’s Flood).

Age and reproduction in two Antarctic plunderfishes (Artedidraconidae) from the Weddell Sea

The Antarctic plunderfishes (Artedidraconidae) are a poorly known component of the bottom fish fauna inhabiting the continental shelf of the High Antarctic Zone. Biological data on these fishes are still rather scarce and generally based on only a few specimens. To increase the knowledge of this group, we investigated the reproductive biology and population age structure of Artedidraco skottsbergi and Dolloidraco longedorsalis, the most abundant plunderfishes collected during the 2013/2014 expedition of the RV Polarstern in the Weddell Sea. Based on macroscopic and histological analyses, we found that both species exhibited prolonged gametogenesis and produced few eggs. Estimates of absolute and relative fecundity were lower in A. skottsbergi than in D. longedorsalis, ranging from 69 ± 7 oocytes per female and 11.4 ± 4.3 oocytes/g, and from 209 ± 73 oocytes per female and 13.5 ± 3.7 oocytes/g, respectively. Female size at first spawning was estimated to be 9.5 and 11 cm in A. skottsbergi and D. longedorsalis, respectively. Age and growth were assessed through otolith readings, and estimates of age ranged between 6 and 14 years in A. skottsbergi and between 3 and 14 years in D. longedorsalis. The von Bertalanffy growth parameters were only estimated for D. longedorsalis (L ∞ = 12.5 cm, k = 0.27, t 0 = −0.06). The results of this study provide insights into some of the biological aspects of these species and shed new light on their life strategies, which show similarities to those of other notothenioids.

Macrozoobenthos of small lowland lakes of Sakhalin Island

Species composition, structure and seasonal dynamics of macrozoobenthos in small lakes of Sakhalin Island are considered on the data of benthic surveys conducted in 1994-2012. Features of the bottom fauna are determined by the lakes origin, their connection with other water bodies, biotic and abiotic conditions. The faunas of the lakes of northern Sakhalin are distinguished by the highest similarity. Generally, variety of benthic communities in small lakes corresponds to their biotope diversity and reduces with the size of lakes decreasing. The most typical benthic communities are those ones of the coastal belt of rigid plants, of the belt of pondweed, and profundal community of the open water area; the latter only is observed in very small lakes. Seasonal dynamics of the benthic communities is defined by biology of a few key species which dominate the whole year round. For example, seasonal dynamics of the profundal community in small floodplain lakes is determined mainly by generative dynamics of one species of chironomid: Chironomus gr. plumosus . Three phases could be traced in the seasonal succession: i) winter; ii) spring and early summer; iii) late summer and autumn. They change under influence of seasonal events as spring flood, summer low water, ice formation, or mass fish migration (reaction of benthic communities on fish migration is adaptive, not catastrophic). Food web of the benthic communities in small lakes is based on autochthonous organic matter of phytoperiphyton, phytobenthos and phytoplankton settled to the bottom. Benthic communities of floodplain lakes play important role in preserving of rheophilic fauna during catastrophic floods.

Effects of harbour excavating and dredged sediment disposal on the benthic invertebrate fauna of River Danube (Austria)

Dredging Austrian Danube harbours becomes necessary to keep the navigation channel free from bed sediment and to insure safe navigation, especially after major floods. In most cases, the excavated substrate is deposited in the free-flowing river section in the vicinity of the mouth of a harbour. The effects of harbour dredging on the biota need to be studied to minimize possible outcomes that may endanger the ecological status of the river system in order to implement the aims of the European Water Framework Directive. This study presents the first quantitative information on the colonisation of benthic invertebrates with respect to Danube harbours. One sampling at Linz Harbour was conducted before dredging and four samplings were carried out after dredging. Four transects were documented in the affected river section. The study used an air-lift sampler and a grab sampler to investigate if and to what extent the benthic invertebrate community is disturbed. It found that the sediment dredging heavily affected the benthic invertebrates (decline of 82% of biomass), while the dumping of the material had no effects on the benthic Danube biota. As a rough estimate (conferring to a simple trend line analysis) the harbour bottom fauna would recover after 235 days.

The assessment of ionising radiation impact on the cooling pond freshwater ecosystem non-human biota from the Ignalina NPP operation beginning to shut down and initial decommissioning

The radiological doses to non-human biota of freshwater ecosystem in the Ignalina NPP cooling pond – Lake Druksiai were evaluated for several cases including the plant's operation period and initial decommissioning activities, using the ERICA 1.2 code with IAEA SRS-19 models integrated approach and tool.Among the Lake Druksiai freshwater ecosystem reference organisms investigated the highest exposure dose rate was determined for bottom fauna – benthic organisms (mollusc-bivalves, crustaceans, mollusc-gastropods, insect larvae), and among the other reference organisms – for vascular plants. The mean and maximum total dose rate values due to anthropogenic radionuclide ionising radiation impact in all investigated cases were lower than the ERICA screening dose rate value of 10 μGy/h. The main exposure of reference organisms as a result of Ignalina NPP former effluent to Lake Druksiai is due to ionizing radiation of radionuclides 60Co and 137Cs, of predicted releases to Lake Druksiai during initial decommissioning period – due to radionuclides 60Co, 134Cs and 137Cs, and as a result of predicted releases to Lake Druksiai from low- and intermediate-level short-lived radioactive waste disposal site in 30–100 year period – due to radionuclides 99Tc and 3H.The risk quotient expected values in all investigated cases were <1, and therefore the risk to non-human biota can be considered negligible with the exception of a conservative risk quotient for insect larvae. Radiological protection of non-human biota in Lake Druksiai, the Ignalina NPP cooling pond, is both feasible and acceptable.

ASSESSMENT OF ENVIRONMENTAL STATE OF WATERCOURSES OF DELTA OF THE VOLGA RIVER BY THE STRUCTURE OF BOTTOM COMMUNITIES

Представлены результаты исследований оценки экологического состояния дельты Волги по структуре донных сообществ, выполненных в рамках научных исследований ФГУП «КаспНИРХ» за период с 2010 по 2013 г.г. В ходе работ определяли количественные и качественные характеристики зообентоса, индекс видового разнообразия (H), модифицированный БИ Вудивисса, олигохетный индекс Пареле D1. Результаты исследований показали, что в бентосном сообществе водотоков дельты р. Волги ведущее положение занимают организмы наиболее интенсивно участвующие в процессах самоочищения водоема (β и β-α-мезосапробы), что характеризует качество исследуемых вод как «Слабо-загрязненная» и «Загрязненная». Картина распределения количественных показателей зообентоса дельты Волги в среднемноголетнем аспекте носила неравномерных характер, с проявлением четкой тенденцию к снижению их значений от восточной части дельты (р. Волга) к западной (рук. Бахтемир).

Influence of zooplankton and bottom fauna on growth of production young carp (Cyprinus carpio, Linnaeus, 1758)

In this paper presents the results of research of the influence of zooplankton and bottom fauna, as a natural food grown in the growth of production young Carps. Investigations were carried out at the choice of 4 ports ponds 'Baranda'. Investigations were carried out at the choice of 4 winter quarters of the pond 'Baranda'. Used the same agroculturals practices in all winter quarters. The winter quarters are populated with young carp old this month, with an average weight of 2.6 to 3.1 grams with different densities of 6538 to 10838 individuals. During the research, followed by the amount of biomass - plankton and bottom fauna, and its influence on growth of carp. There was no statistically significant difference the amount of biomass formed between winter quarters. In the first group (Z-2 and Z-6) there was no correlation between the available natural food and grown carp, while in the second group (Z-16 and Z-22) there is a linear relationship between the two variables. The different final weight of carp has had different density populated.

LONG-TERM CHANGES OF GROUND FAUNA OF COASTAL ZONES OF APSHERON AND BAKU ARCHIPELAGOES ISLANDS OF CASPIAN SEA DURING 1967-2007

During 2000-2007 studying of specific structure macrozoobenthos and its quantitative distribution on islands of Apsheron and Baku archipelagoes of Caspian Sea has been spent. The got results have been compared with the results of analyses carried out in the same area of the sea between 1967-1986 years, and as a result, increasing in quantity and bio weight of bottom fauna has been observed. Number of macroorganisms has increased in 20 times, and a biomass - in 15 times. The oil maintenance in waters for the first 20 years has decreased with in 1,2-2 times, for the next 20 years quantity of oil has decreased in limits from 10 to 300 times. Considering the above-stated, it is possible to come to conclusion about absence now appreciable negative consequences for sea ecosystem and bioresources of Caspian Sea from working out of oil and gas deposits.

Asteroids, ophiuroids and holothurians from the southeastern Weddell Sea (Southern Ocean).

Until the early 1980s, the composition and distribution of the asteroid (starfish), ophiuroid (brittle star) and holothurian (sea cucumber) bottom fauna of the southeastern Weddell Sea was virtually unknown. This southernmost part of the Atlantic sector of the Southern Ocean is a typical high-latitude Antarctic region located in the circumpolar permanent pack-ice zone. It became accessible for large-scale scientific surveys only through the availability of modern ice-breaking research vessels, such as the German RV “Polarstern”. Here, we describe a dataset of the faunal composition and abundance of starfish, brittle star and sea cucumber assemblages in this area, based on collections from trawl catches carried out during three “Polarstern” cruises in 1983, 1984 and 1985. The set comprises a total of 4,509 records of abundances of 35 asteroid species (with a total of 2,089 specimens) and 38 ophiuroid species (with a total of 18,484 specimens) from 34 stations, as well as of 66 holothurian species (with a total of 20,918 specimens) from 59 stations including zero-abundances (absences). A synthesizing zoogeographical community analysis confirms the presence of three distinct assemblages of asteroids, ophiuroids, and holothurians with highest species richness on the eastern shelf. Overall, starfishes, brittle stars and sea cucumbers were present at all sites investigated in the study area but composition and abundance of asterozoan (asteroids and ophiuroids together) and holothurian fauna varied considerably. A synthesizing zoogeographical community analysis confirms the presence of three distinct assemblages of asteroids, ophiuroids, and holothurians with highest species richness on the eastern shelf. In the case of asterozoans, water depth and latitude seemed to be the most important drivers of assemblage distribution and composition. One of the holothurian assemblages was part of the rich macrozoobenthic community dominated by a diverse and abundant epifauna, mainly sponges and gorgonians. Another one was mainly composed of vagrant deposit-feeding species inhabiting a predominantly non-colonised substratum. In addition, a mixed holothurian assemblage was identified.

&lt;strong&gt;Where have all the ”vejdovskies” gone (Potamothrix vejdovskyi Hrabe)? Ponto-Caspian tubificid oligochaete species in Lake Mälaren, south-central Sweden, in a 100 year perspective&lt;/strong&gt;

Potamothrix vejdovskyi is one of several alien Ponto-Caspian species presently invading Europe and the New World. Its invasive success has been suggested to be dependent upon the trophic degree of the water, and this species is considered to be particularly indicative of mesotrophy (Lang &amp; Reymond 1996). Bottom fauna surveys performed by the Swedish Fisheries Board in 1915 and 1916 and in 1933–1935 did not reveal the existence of P. vejdovskyi in Lake Mälaren, whereas extensive bottom fauna programs in the lake in 1967–1976 demonstrated a wide distribution of the species in the central, least polluted basins. Strict quantifications of the distribution of oligochaetes in those basins in 1974 showed that P. vejdovskyi then made up on average 28 % of the total abundance of oligochaetes. However, in later bottom fauna surveys in Lake Mälaren, performed by the Swedish Environment Protection Agency in 1981 and in 2009–2011), P. vejdovskyi could not be found at all. Sewage treatment around Lake Mälaren accelerated in the late 60’s and the phosphorus load is nowadays considerably lower than before treatment (about 30 % less in terms of total-P concentrations in the water). The question of why this species seems to have more or less disappeared from the lake remains unsolved.

Review of sterlet (Acipenser ruthenus L. 1758) (Actinopterygii: Acipenseridae) feeding habits in the River Danube, 1694–852 river km

The aim of this work is to present the variation in the sterlet’s (Acipenser ruthenus L. 1758) diet along the course of the River Danube, from 1694 to 852 river km. The diet of sterlet mostly comprised 12 bottom fauna taxa. Sterlet in the Danube feed mainly on larvae of Trichoptera, Chironomidae (Diptera) and Gammaridae (Amphipoda), with a reduction in food composition variability close to the Djerdap I dam and in the reservoir between the two dams. The other components of the diet were Corophium sp., Asselus sp., Mollusca, Oligochaeta, Annelida, Insecta, Nematoda and Hirudinea. The organisms typical of lithorheophilic and psammorheophilic biocoenoses play a considerable role in the diet of the sterlet. Composition of bottom fauna as food items varies due to changes in environmental conditions induced mainly by the construction of two dams: Djerdap I (943 river km, 1970) and Djerdap II (863 river km, 1984).

7. Macrozoobenthos community

Quantitative and qualitative parameters of the macrozoobenthos community in Lake Drūksiai were analyzed. We compared our data obtained in 2011–2012 with those of earlier investigations. The comparison of the current situation with the situations before the launch of the Ignalina Nuclear Power Plant (INPP) and during the initial period of its operation shows that stenothermic coldwater species of relict crustaceans and some species of chironomids have disappeared from the bottom fauna. In general, quantitative indices of zoobenthos development have increased in comparison with those recorded in the initial INPP operation period and are characterized by the dominance of oligochaetes in the profundal.

Macrobenthic invertebrates in the main channel of Lake Nasser, Egypt

Samples were collected seasonally from ten sectors of the main channel of Lake Nasser during 2013. Macrobenthic community consisted of twenty-four species belonging to three phyla, Annelida (five species), Mollusca (nine species) and Arthropoda (ten species). Annelida ranked the first position and constituted 52% and 68% of total population density (P.D.) and biomass of macrobenthic invertebrates (M.B.I.) respectively. Annual average of M.B.I. was 529organisms/m2 weighing 2.30g/m2. The abundance of M.B.I. species was closely related with type of sediments and water level in the lake. Tushka was the richest sector in the area where 1132organisms/m2 weighing 3.65g/m2 were recorded, while El-Madiq was the poorest one where 127organisms/m2 weighing 0.61g/m2 were recorded. Southern sectors were more populated with bottom fauna than northern sectors. This mostly attributed to the increase of Limnodrilus spp. Benthic fauna attained its maximum during autumn, while summer season sustained the lowest density. Correlation Coefficient revealed strong negative relationships between temperature and the density of oligochaets and arthropods. The highest diversity index (H) and species richness (SR) were calculated in Abu-Simble while, the lowest (H) and SR were calculated in El-Madiq.

Polychaete diversity in the estuarine habitats of Términos Lagoon, southern Gulf of Mexico

Hernandez-Alcantara, P., Cortes-Solano, J.D., Medina-Cantu, N.M., Aviles-Diaz, A.L. and Solis-Weiss, V. 2014. Polychaete diversity in the estuarine habitats of Terminos Lagoon, Southern Gulf of Mexico. Memoirs of Museum Victoria 71: 97–107. In order to establish the status of the biodiversity of the polychaete fauna inhabiting the soft bottoms in the largest lagoon-estuarine system from the southern end of the Gulf of Mexico, Terminos Lagoon, we collected and identified 3,398 specimens belonging to 119 species and 33 families of polychaetes. The soft bottom fauna was then compared with records of polychaetes collected in other habitats in the lagoon such as seagrass beds and mangroves. In all, 190 species from 34 families of polychaetes previously recorded there were taken into account. The families Nereididae (20 spp.), Spionidae (15 spp.) and Syllidae (14 spp.) were the most diverse. The soft bottom habitat has by far the largest number of species (119) followed by the seagrass beds and mangroves with 75 and 42 species respectively. Large spatial heterogeneity in polychaete composition was observed, as only 5% of the species (Melinna maculata, Capitella sp., Mediomastus californiensis, Schistomeringos rudolphii, Marphysa sanguinea, Alitta succinea, Diopatra cuprea, Scoloplos treadwelli, Prionospio heterobranchia and Scolelepis squamata) were widely distributed in the lagoon. The polychaete fauna living in the mangroves is quite similar to that from seagrasses and soft bottoms (R(ANOSIM) = 0.247 and 0.3 respectively), but the polychaetes in the seagrasses and soft bottoms are clearly different from each other (R(ANOSIM) = 0.622). The 119 polychaete species identified in this study represent a significant increase in the records of biodiversity recorded so far in Terminos Lagoon, while the total of 190 species recorded for the whole lagoon represents a larger number than any other recorded for an American tropical estuary.

BENTHIC FAUNA STATUS AS INDICATOR OF WATER QUALITY ASSESSMENT IN STREZHEVO ACCUMULATION

In the period March–October 2009 in the water of Strezhevo accumulation, Shemnica River and the alimentation canal samples of water and sediment were being collected for multidisciplinal research, with special regard to the quantitative and qualitative composition of benthic fauna. The field study was organized in season intervals, and special attention was paid to the critical months (June, July, August) with the goal of following-up the dynamics of the changes in the accumulation. The obtained results shows that the dominant groups of bottom fauna are Oligochaeta, Ephemeroptera,Trichoptera, Diptera and Plecoptera. According to the used indicators (composition of macrozoobentos fauna) it was found that there is a serious worsening of the water quality in the ecosystem. Increased presence of biodegradable organic matters was noticed, especially in the summer period.

The Tommotian phase of the Early Cambrian Agronomic Revolution in the carbonate mud environment of central Siberia

The profound ecological change of the marine benthos that eventually led to the almost complete destruction of the Precambrian matgrounds by benthic grazers and bioturbators (the agronomic revolution) was largely completed in the Tommotian. At that time, burrows produced by bottom-dwelling animals as shelters against predators were supplemented by burrowing for food by predators and sediment feeders. The limy mud ichnofauna of that age in Siberia was very different from the roughly coeval sand bottom faunas of Baltica. Although the exact zoological identity of the animals forming the infaunal Tommotian traces remains unknown, they probably mostly represent various kinds of early nemathelminthes. No apparent locomotion traces of mollusc origin have been encountered in the Early Cambrian, despite the abundant occurrence of skeletal fossils attributed to molluscs. Possibly the standard muscular foot, typical of modern molluscs, had not yet developed. Ichnotaxa represented are Teichichnus isp., Rhizocorallium isp., Chondrites isp., possibly the Buren ichnocomplex and others.

Submarine groundwater discharge to the Baltic coastal zone: Impacts on the meiofaunal community

The discharge of groundwater into the sea affects surrounding environments by changing the salinity, temperature and nutrient regimes. This work reports the spatial effects of a submarine groundwater discharge (SGD) on the abundance and structure of the meiofaunal community in the shallow area of Puck Bay (Baltic Sea). Several field expeditions in the years 2009 and 2010 found that low-saline groundwater escapes into the bay from permeable, sandy, near-shore sediments. The SGD literature has grown rapidly during the current decade; however, the effects of this type of disturbance on the shallow sandy bottom fauna have thus far been little studied. We provide evidence that the discharge of groundwater has a clear effect on meiofaunal assemblages in the research area. This effect was reflected in a significant decline of certain meiofaunal taxa, mainly nematodes and harpacticoids, as well as in altered patterns of temporal distribution and small-scale (vertical) zonation of meiofaunal assemblages. Overlooking submarine groundwater discharge processes may lead to serious misinterpretations of ecological data. It is clear that groundwater discharge phenomena should be considered in future scientific studies.