Effect of lipid reserves on individual carbon content of two planktonic freshwater copepod species

The effect of the variation of lipid droplet volume on individual carbon content was studied in two species of planktonic freshwater copepods, Eudiaptomus gracilis G.O. Sars and Thermocyclops oithonoides G.O. Sars. It was found, that when a multiple regression of carbon content on prosoma and lipid droplet volume instead of a simple regression of carbon content on prosoma volume was applied, the unexplainied variance of individual carbon content of Eudiaptomus gracilis could be reduced. However, the use of multiple regression on Thermocyclops oithonoides data did not lead to significantly higher coefficient of determination than was obtained by using a simple regression.     

Vertical distribution of epipelagic siphonophores at the confluence between Benguela waters and the Angola Current over 48 hours

The diel distribution of epipelagic siphonophores at a station off northern Namibia (18°00 S 10°30 E) was studied. This area is characterized by the mixing of surface waters of the Angola Current with the waters of the northernmost Benguela region. During the sampling period, the continuous flow of the Angola Current gave rise to a marked thermocline at ca 30 m depth. In order to study the diel vertical distribution patterns of epipelagic species under these hydrographic conditions, narrow depth horizons in the top 200 m of the water column were sampled repeatedly over a 48 h period. Thirty-four species were collected. Sphaeronectes gracilis and Chelophyes appendiculata predominated. Increasing numbers of species and individuals were observed on the second day of sampling, particularly in the layers above the thermocline. Only a few species showed an upward nocturnal migration that crossed the boundary between 2 water masses. The differences in the depth distributions of the various species were related to 3 distinct phenomena: the existence of 2 separate siphonophore populations associated with each of the 2 water masses; vertical migration by the most abundant species, which were able to cross the thermocline; and differences in patch size for the most epipelagic species.     

Lipid content and utilization of lipids in planktonic copepods in Lake Pääjärvi,southern Finland

The variation of the lipid content of a planktonic copepod species, Eudiaptomus gracilis G. O. Sars, was studied in an oligotrophic lake, Pääjärvi, southern Finland, during 1982. The variation was caused by changes in the food resources and by the use of lipids for reproduction. The lipids are partly present in the form of droplets, which provide an energy reserve for some of food shortage, or may be used in reproduction. The utilization of lipid droplets for nutrition was studied by culturing specimens of two species, Eudiaptomus gracilis and Thermocyclops oithonoides G. O. Sars, in the absence of food. It was found that about half of the energy required for the 30-hour experimental period was obtained from the lipid droplets. However, not all the animal groups could use their lipid droplets and they had to use other reserves to satisfy their energy requirement. Lipid droplets seemed to have only a minor effect on the sinking rate of Eudiaptomus gracilis.     

Ecological description of the sodium chloride mineral springs in the Kirenga River basin and the upper reaches of the Lena River: 1. General characteristics of the springs and their hydrofauna

The aquatic microecosystems and their environment have been studied in 12 mineral springs located in the Cis-Baikal Depression and in the basin of the upper reaches of the Lena River (Eastern Siberia). The hydrochemical characteristics of the springs, originating from the Cambrian salt deposits, are given. Their total mineralization varies from 1.1 to 123.0 g/L and the water is sodium chloride. The soils formed under the influence of the mineral waters (“para-soils”) are described. The data on the composition and quantitative abundance of aquatic fauna are presented. Six types of macroinvertebrate communities are described. The communities where Turbellaria, Gastropoda, and Psychodidae dominate are recorded in weakly mineralized waters (<3 g/L). The communities where Chironomidae dominate are found in waters characterized both by low and high (up to 28 g/L) salinity. In springs with a water salinity of 2.5–11 g/L, communities characterized by the dominance and high biomass of amphipods Gammarus lacustris Sars. are formed. A unique type of community where Ephydridae larvae dominate (>97% of the biomass) is described for the concentrated brines in Ust’-Kutskii spring. Halophilic species of crustaceans are recorded in the meiofauna. The presence of Foraminifera (marine organisms) in the two studied springs attracts specific interest.     

Long chain alkyl phenols from the liverwort Schistochila appendiculata

3-Undecyl phenol, 6-undecyl salicylic acid and potassium 6-undecyl salicylate were isolated from the New Zealand liverwort Schistochila appendiculata. 3-Tridecyl and 3-pentadecyl phenol, 6-tridecyl and 6-pentadecyl salicylic acid, potassium 6-tridecyl and 6-pentadecyl salicylate and 6-undecyl catechol were also detected in the same species. The chemical constitution of S. appendiculata is quite similar to that of the brown algae Caulocystis species, and of the higher plants Ginkgo biloba and some of the Anacardia species. The allergic reaction brought on by S. appendiculata might be due to the presence of these phenolic compounds.     

Sympatric occurrence of three leaf beetle species of Macroplea Samouelle, 1819 (Coleoptera,Chrysomelidae, Donaciinae) in Finland with a key to species in Northern Europe

Macroplea Samouelle, 1819 is the only known fully aquatic leaf beetle genus with three European species that have earlier been classified by their assumed water salinity preferences. We studied the inter- and intraspecific variation of the specimens living in Northern Europe using both molecular (cytochrome c oxidase subunit I, COI) and morphological evidence. The variation in the COI sequences between M. mutica (Fabricius, 1792) and M. pubipennis (Reuter, 1875) was 8.4%–9%, M. mutica and M. appendiculata (Panzer, 1794) – 3.9%–4.9%, and M. appendiculata and M. pubipennis – 8.8%–9.2%. All three species were sampled together in the Bothnian Sea on the same water plants, showing that neither salinity nor plant species bear a decisive importance in their occurrence in the region. Phylogenetic results suggest the existence of two currently unknown Macroplea species that are evolutionarily close to M. appendiculata. A key to the Nordic species is provided.     

Two new species of Pseudocythere Sars (Crustacea,Ostracoda) from Britain and Norway

Two new species of the genus Pseudocythere Sars are described, one each from British and Norwegian waters respectively.     

Effect of salinity on the distribution of Ponto-Caspian gammarids in a non-native area – environmental and experimental study

The native area of gammarids from the so-called ‘Caspian complex’, Pontogammarus robustoides (G.O. Sars, 1894), Obesogammarus crassus (G.O. Sars, 1894), Dikerogammarus haemobaphes (Eichwald, 1841) and D. villosus (Sowinsky, 1894), is associated with brackish waters. Over the last several decades they have colonized the European inland waters and part of the brackish Baltic Sea. It is believed that anthropogenic increase in the salinity of inland waters facilitated their expansion. However, the influence of salinity on the dispersal of gammarid species outside their native area is not fully understood. We tested the hypothesis that salinity was a major factor in determining distribution, based on the abundance of Gammaridae in three coastal areas of low salinity (brackish Baltic), i.e. 0.3, 3.4 and 7.3 PSU, successfully inhabited by them. Additionally, for the first time, the effect of water salinity on the osmoregulatory capacity of O. crassus was examined under laboratory conditions, for the salinities given above. The experiments showed that similarly as in the case of other Caspian complex species, salinity values of about 7 PSU create better conditions for osmoregulation in O. crassus than lower salinities (i.e. 0.3 and 3.4 PSU). In the environmental part of the study, we observed that only D. villosus achieved a significantly higher abundance in the area of 7.3 PSU. Thus, we concluded that in the range of 0.3–7.3 PSU, salinity is not a key factor governing the distribution of Ponto-Caspian gammarids.     

Effect of flooding with sewage water on three wetland sedges

Plants of three wetland sedges, Carex vesicaria, C. rostrata, and C. gracilis, were subjected to flooding with diluted pig farm sewage water in a sand-culture experiment lasting for one growing season (20 weeks). Sewage water application altered growth dynamics and accumulation of dry matter in all three species; it shifted the distribution of dry matter in favor of above-ground parts; it depressed root growth both in dry mass and length; and it increased percentages of major nutrients (nitrogen, phosphorus, and potassium) in plant dry matter. In the root structure, sewage water application inhibited formation of gas spaces in the cortex, differentiation of exodermis and endodermis, and formation of starch grains in the cortex. The changes in root growth and structure are ascribed to the combination of (1) high nutrient availability, and (2) oxygen deficiency, which developed in the root medium following addition of sewage water. In view of these findings, Carex species are not well suited for use in the treatment of wastewaters rich in both mineral nutrients and organic matter.     

Biogeographical distribution of Hartaetosiga strains (Choanoflagellatea,Craspedida, Salpingoecidae) including morphological and transcriptomic data from a transect across the Atlantic Ocean

The genus Hartaetosiga Carr, Richter and Nitsche, 2017 comprised up to now only three species, H. gracilis (Kent) Carr, Richter, Nitsche, 2017, H. balthica (Wylezich and Karpov) Carr, Richter and Nitsche, 2017 and H. minima (Wylezich and Karpov) Carr, Richter and Nitsche, 2017. Based on distinct molecular data these species were relocated from the strictly freshwater genus Codosiga (Ehrenberg) Bütschli, 1878 to a new genus comprising brackish and marine species. During the cruise MSM82/2 across the Atlantic Ocean in 2019, surface water samples were taken from 15 stations along a transect ranging from 35°S to 23°N. We were able to isolate and cultivate 14 strains of the genus Hartaetosiga. Morphometric data showed no distinct morphological traits allowing for a species delineation, indicating a cryptic species complex within the genus. Based on cultivation, morphological data, and molecular analyses, we recorded H. gracilis for the first time from off-shelf waters of the Atlantic Ocean and could describe a new species, H. australis n. sp. This new species was recorded from sampling stations in the Southern Hemisphere only, which may indicate a potential biogeographic restriction likely caused by the Equatorial Counter Current (ECC), dividing the northern and southern surface waters.     

Diatom communities in small water bodies at H. Arctowski Polish Antarctic Station (King George Island, South Shetland Islands, Antarctica)

An investigation of ponds, puddles and slow-flowing waters situated in the area of the Polish Antarctic Station distinguished two groups of diatom communities. The first group characterized waters poor in nutrients and brackish. The number of taxa, abundance of species and diatom biomass index were all low. Nitzschia homburgiensis, Achnanthes laevis var. quadratarea and A. delicatula prevailed. The second group characterized water richer in nutrients and brackish. The number of species was also low, but the diatom biomass index was higher. Nitzschia gracilis, Navicula gregaria and Navicula wiesneri formed large populations. Received: 17 May 1996 / Accepted: 20 September 1997     

Decline of Gammarus lacustris Sars (Crustacea: Amphipoda) population in the delta of the Selenga River

We determined the amphipod population characteristics from the water bodies of the delta of the Selenga River, where Gammarus lacustris Sars, 1863 was industrially harvested until the 1990s. In 2011, the population density of G. lacustris varied from 80 to 10200 in Lapkhai Lake and from 80 to 2320 ind./m² in Krivaya Channel. The low population density (<40 ind./m²) in Gryaznoe Lake, together with the absence of the species in the waters of the former Zhilishchenskoe Lake, confirms the indications of population density decline in the associated waters of the delta. Population growth of G. lacustris was limited primarily by changes in the hydromorphology of the lakes and waterways due to floods of the early 1990s and the subsequent period of extremely low flow of the Selenga River.     

Impact of acidification and eutrophication on the distribution of fish species in shallow and lentic soft waters of The Netherlands: an historical perspective

The species richness and composition of fish assemblages were examined in lentic soft waters in The Netherlands. The selected bodies of water reflected a large variation in geomorphological and limnological factors. In total, 24 fish species were encountered in Dutch soft waters. During 1983–1984 Esox lucius, Perca fluviatilis, Rutilus rutilus, Scardinius erythrophthalmus, Tinca tinca and Umbra pygmaea were quite common. In slightly acid and alkaline waters (pH≥5) Rutilus rutilus, Scardinius erythrophthalmus, Perca fluviatilis, Ictalurus nebulosus and Cyprinus carpio accounted for about 90% of the total number of specimens in the catches. Strongly acid waters (pH < 5) generally were fishless. If fish were present in these waters, however, the catches mainly consisted of Umbra pygmaea. Only in a few strongly acid systems were other species collected. The lowest pH at which certain fish species occurred varied from 3.1 to 7.0. In particular, Umbra pygmaea was extremely acid-tolerant. The percentage of waters which harboured fish as well as the average number offish species per water decreased steeply between pH 6 and 4. The sampled waters showed remarkable differences in their fish assemblages. With hierarchical classification, six groups of waters could be distinquished with respect to their fish fauna. The site groups are defined and characterized physico-chemically and their fish assemblages described. Multivariate analysis showed that the structure of fish communities is strongly related to the pH, the alkalinity, trophic level and the ionic composition of the water. Comparison of historical and recent data on the occurrence of fish strongly indicated that in many sampling sites fish species or even entire fish assemblages had disappeared. Ordination of available data also illustrated recent changes in community structure. At least 67% of the nowadays extremely acid waters formerly harboured fish populations. The impoverishment of fish communities or the total loss of fish were primarily caused by cultural acidification. Limited nutrient enrichment of soft waters only resulted in minor alterations of fish assemblages.     

Microbial Communities of Low Temperature,Saline Groundwater Used for Therapeutical Purposes in North Poland

Knowledge on microbial community composition and ecology in highly mineralized (TDS up to 71?g l^?1), cold waters (T?<?12?°C) from the zones of restricted water exchange is scarce. Therefore, the aim of our study was to reveal how the particular physicochemical water conditions of these zones affect the community composition. The community members, which could be involved in the sulfur cycling were of particular interest since they may strongly influence wells operation. The pristine, mineral waters of North Poland were extracted from boreholes reaching Cenozoic, Jurassic, and Triassic aquifers at the depth of 46–1248?m below ground surface. Both culture-dependent (culturing on R2A medium) and culture-independent techniques (microscopic methods and high-throughput 16S rDNA amplicon sequencing) were applied. The bacterial communities were characterized by low complexity and strongly varied across the sampling locations. Bacteria potentially involved in the sulfur cycle (sulfate reduction) were common in all mineral waters and were dominant (especially Desulfovibrio) in the deepest waters. The most important geochemical drivers of the observed microbial community composition were TDS including Cl^?, Na⁺, Mg²⁺, and NO₃^?. Bacterial isolates belonged mostly to the genus Bacillus. Sequences assigned to Archaea (Methanobacterium) were detected only in the deepest borehole water.     

Ilyocryptus thailandensis sp. nov. (Cladocera: Anomopoda: Ilyocryptidae) from North Thailand

Previously only a single species of Ilyocryptus Sars , 1862 (Cladocera: Anomopoda: Ilyocryptidae) was reported from Thailand, I. spinifer Herrick , 1882. However, our examination of numerous samples from this country resulted in the discovery of four other species of Ilyocryptus. Ilyocryptus thailandensis sp. nov. is described from two adjacent water bodies in Uttaradit Province, North Thailand. It has at least two characters which distinguish it from any other species of the Ilyocryptus: (1) a row of lateral setae reaching medial anus, and continuing along preanal margin up to base of the postabdomen; (2) a large projection bearing the sensory setae, situated on the coxal region of antenna II. It appears to be a rare species, may be, endemic of the North Thailand.     

The contribution of standing waters to aquatic biodiversity: the case of water beetles in southeastern Iberia

The southeast of the Iberian Peninsula is a recognized area of high aquatic biodiversity, water beetles being one of the most well-known groups contributing to such biodiversity. The standing waters of this area show a high habitat diversity, occurring fresh, saline, temporary, permanent, karstic, endorheic, and artificial small water bodies. Despite this, there has been no attempt to analyze their contribution to local biodiversity. In this work, we identify the species inhabiting standing waters, analyze their contribution to the checklist from the study area, and recognize the species exclusive to this kind of habitat. We also highlight the most threatened species, identify the habitats which constitute biodiversity hotspots for this group, explore patterns of water beetle assemblage composition, and identify indicator species associated with each habitat type. We collected 125 species, 55 of them being typical to lentic habitats, in the set of 26 sampled standing water bodies, which means the 57% of the 218 species recorded in the most recent checklist for the study area. A total of 10 species are Iberian endemics and four can be considered threatened, Ochthebius irenae falling in both categories. Natural ponds showed the highest species richness (91 species), while saline water bodies (endorheic lagoons and continental salt-pans) contributed the most threatened species: Nebrioporus baeticus, Ochthebius delgadoi, Ochthebius tudmirensis and Ochthebius irenae. The most representative species for continental salt-pans was Ochthebius notabilis, for endorheic lagoons Ochthebius marinus and Hygrotus pallidulus, while Hydroglyphus geminus played this part in rice fields. Our results suggest that rice fields, endorheic lagoons, and continental salt-pans have specific water beetles assemblages, which could be used in bioassessment and conservation studies. In general, standing waters are seriously threatened in this area, particularly as a result of intensive agricultural activities. Thus, taking into account these ecosystems hold a high number of species, their continued degradation is likely to result in a significant loss of biodiversity, including key populations of a number of threatened and endemic species.     

Do natural container habitats impede invader dominance? Predator-mediated coexistence of invasive and native container-dwelling mosquitoes

Predator-mediated coexistence of competitors occurs when a species that is superior in competition is also more vulnerable to a shared predator compared to a poorer competitor. The invasive mosquito Aedes albopictus is usually competitively superior to Ochlerotatus triseriatus. Among second instar larvae, A. albopictus show a lesser degree of behavioral modification in response to water-borne cues from predation by the larval midge Corethrella appendiculata than do O. triseriatus, rendering A. albopictus more vulnerable to predation by C. appendiculata than O. triseriatus. The hypothesis that C. appendiculata predation favors coexistence of these competitors predicts that C. appendiculata abundances will be negatively and positively correlated with A. albopictus and O. triseriatus abundances, respectively, and that coexistence will occur where C. appendiculata are common. Actual abundances of O. triseriatus, A. albopictus, and C. appendiculata in three habitats fit this prediction. In natural container habitats like tree holes, C. appendiculata were abundant and competitors co-existed at similar densities. In cemeteries and tires, which occur primarily in non-forested, human-dominated habitats, A. albopictus dominated, with abundances twice those found in tree holes, but C. appendiculata and O. triseriatus were rare or absent. We also tested for whether antipredatory behavioral responses of A. albopictus differed among habitats or populations, or were correlated with local C. appendiculata abundances. We could detect no differences in A. albopictus antipredatory behavioral responses to water-borne cues from predation. Tree hole habitats appear to promote co-existence of O. triseriatus and A. albopictus through interactions with predatory C. appendiculata, and this predator effect appears to limit invasion success of A. albopictus in tree holes. There are many studies on predator-mediated coexistence in natural habitats but to our knowledge this is the first study to suggest differential predator-mediated coexistence between natural and man-made habitats. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Distribution and Species Composition of Zooplankton in Himalayan Ecosystems

The zooplankton communities of lakes, Sars, wetlands and ponds in Jammu-Kashmir Himalayas were examined. The waters are situated between 600–3800 m a. s. l. and, in the ordinates 30°–36° N. Significant variations in Rotifers and Crustacean distribution patterns were encountered. Some species having wide tolerance limits are more frequent while a few species due to their rigid environmental demands are restricted to few water bodies. Such species serve as good indicators of trophic evolution. The general distribution of these groups and their ecological implication have been discussed in the paper.     

Length-weight relationships of Ponto-Caspian gammarids that have overcome the salinity barrier of the southern Baltic Sea coastal waters

Gammarids from the Caspian complex have invaded many European waters along the rivers and canals of the inland migration corridors. The species examined in this work are well known as invaders of European freshwater environments, so the colonization of brackish habitats is a phenomenon inviting more detailed investigation. The aim of this study was to determine the condition of the Ponto-Caspian gammarids Pontogammarus robustoides (G.O. Sars, 1894), Obesogammarus crassus (G.O. Sars, 1894), Dikerogammarus haemobaphes (Eichwald, 1841) and Dikerogammarus villosus (Sowinsky, 1894) as expressed by the relationship between total length and the wet weight of specimens in the brackish waters of the Gulf of Gdansk (Poland). The relationships can be regarded as responses to a newly expanded habitat after they overcome the salinity barrier of the southern Baltic Sea coastal waters. All these Ponto-Caspian gammarids demonstrated an increase in weight with increasing total length: P. robustoides (b = 2.852), O. crassus (b = 3.3477), D. haemobaphes (b = 3.7855) and D. villosus (b = 2.6917). The results are an indicator of the relatively good condition of the organisms and indicate that the brackish environment of the Gulf of Gdansk affords them excellent possibilities for growth.     

Neoboeckella loffleri (Copepoda: Calanoida), a new species and genus from Bolivian fresh waters

A new species and genus of freshwater calanoid, Neoboeckella loffleri, is described from shallow, high-altitude waters. N. kinzeli (Löffler), 1955, is also included in the new genus. Neoboeckella, like Hemiboeckella Sars from Australia, is characterized inter alia by an exceptionally high degree of sexual dimorphism in size.