Untersuchungen zur Renaturierung von Feuchtgebieten im Tijuana Ästuar unter besonderer Berücksichtigung von brackwasserhaltigen und salinen Teichen

This study represents the first comprehensive biological and hydrochemical investigation of small coastal ponds in the saltmarsh dominated Tijuana Estuary, southern California (U.S.). Special attention is given to the brackish water biotopes. Different salinities and considerable fluctuations in water level characterized these shallow ponds and restrict the biological settlement. Fluctuations of salinities ranged from brackish water to hyperhaline water conditions. Due to different salinity levels, the ponds vary in hydrochemistry, macroinvertebrate species composition and plant communities. The macroinvertebrate community of the brackish waters were dominated by Gastropoda, Odonata, and Coleoptera containing a mixture of freshwater/brackish water species and marine macroinvertebrates. Typical plants of the brackish habitat were Typha domingensis (Southern cattail), and Scirpus californicus (California bulrush) associated with Juncus acutus (Siny rush). These brackish habitats with a wide range of salinity fluctuations are sparsely colonized but represent a niche for typical highly adaptable species. Especially, it is a biotope for species with a wide range of salt tolerance. Therefore, endangered species occurred besides introduced or invasive species in the ponds of the Tijuana Estuary. This fact has to be taken into account in case of wetland restoration. Due to the freshwater influence, the restoration of brackish habitats focuses on the problem of invasive species.Die vorliegende Arbeit befasst sich mit der Situation des Tijuana-River-Ästuars im Südwesten Kaliforniens und untersucht insbesondere Flachgewässer mit Brackwassercharakter. Verschiedene Salzgehalte und erhebliche Schwankungen der Wasserstände sind für diese Gewässer charakteristisch und limitieren die biologische Besiedelung. Die Unterschiede in der Salinität reichen dabei von Brackwasserbedingungen bis hin zur Hypersalinität. Aufgrund der verschiedenen Salzgehalte variieren die Gewässer in der hydrochemischen Zusammensetzung, der Makroinvertebratenzusammensetzung und der Pflanzengesellschaften. Die Gruppe der Makroinvertebraten in den Brackwasserbiotopen wird von Schnecken, Libellen und Käfern dominiert, wobei Süß- und Brackwasserarten zusammen mit marinen Invertebraten auftreten. Typische Pflanzen der Brackwasserlebensräume sind Typha domingensis und Scirpus californicus, verbunden mit Juncus acutus-Pflanzen. Solche Brackwasserbiotope mit ihren stark schwankenden Salzgehalten sind zwar artenarm, aber sie stellen zugleich Nischen für Organismen mit speziellem hohem Adaptationsvermögen insbesondere hinsichtlich der Salztoleranz dar. So wurden bei den Untersuchungen gefährdete, aber auch invasive Arten gefunden. Diese Besonderheit ist bei allen Sanierungs- und Renaturierungsaktivitäten zu berücksichtigen

Mesohabitat Associations Of The Devil Tryonia, Tryonia Diaboli (Gastropoda: Truncatelloidea: Cochliopidae)

The Cochliopidae of Texas include both stygobitic species, those that occupy only underground habitats, and epigean species, those living only in aboveground habitats. The devil tryonia, Tryonia diaboli, was described from the Devils River of Texas from river wrack, without additional habitat information. This species has been largely ignored since its description, so details of its habitat and ecology are obscure. In Dolan Springs and Finegan Springs, flowing into the Devils River, we sampled macroinvertebrates at five sites that form a gradient from the aquifer to the mainstem Devils River. We found the highest abundances of T. diaboli in aquifer samples, decreasing sharply downstream from the spring orifice. Our findings indicate that T. diaboli is stygophilic, occupying a transitional area including the aquifer as well as aboveground portions of springs

Molluscan paleontology of the Pliocene Peace Valley beds and Ridge Route formation (Ridge Basin group), Ridge Basin, southern California

The Ridge Basin, 90 km northwest of Los Angeles, California, lies within the San Gabriel, San Andreas, Liebre, and Clearwater fault zones. The basin is an elongated, wedge-shaped, intermontane, Miocene-Pliocene basin filled with about 12 000 m of marine, lacustrine, fluvial, and alluvial sediment. More than half of the thickness of the Ridge Route formation and about one fifth of the Peace Valley beds was examined for molluscs along the northeastern side of the basin and more than 600 m of section were measured. The nonmarine molluscs of the Ridge Route formation and Peace Valley beds consist of ten species: one unionid, Anodonta oregonensis (Lea); three sphaeriids, Musculium lacustre (Muller), M. transversum (Say), and Pisidium (Cyclocalyx) nitidum Jenyns; four hydrobiids, Fontelicella aff. F. (F.) truckeensis Yen, Tryonia aff. T. protea Gould, and Hydrobiidae species 1 and 2; one lymnaeid, ?Stagnicola sp.; and one planorbid. ?Planorbula aff. P. armigera (Say). All of the hydrobiids occur stratigraphically in the lower portion of the Ridge Route formation and Peace Valley beds. The other nonmarine molluscs occur in the Ridge Route formation and Peace Valley beds above the hydrobiids except in measured section 3, where Fontelicella aff. F. (F.) truckeensis and Hydrobiidae species 2 are associated with Musculium lacustre, M. transversum, and ?Planorbula aff. P. armigera. Freshwater environments are indicated by the presence of Anodonta Musculium, Pisidium, Fontelicella, ?Stagnicola, and ?Planorbula, whereas brackish water environments may be indicated by Tryonia or hydrobiids. Tryonia aff. T. protea is interpreted to tolerate a wide salinity range. Stagnant water is indicated by Stagnicola and Planorbula. Shallow freshwater is suggested by ?Planorbula aff. P. armigera or Pisidium (Cyclocalyx) nitidum. ?Stagnicola, together with ?Planorbula aff. P. armigera, is assumed to represent shallow ponds or marshes on a floodplain. Ridge Basin molluscs occur in sediment ranging from claystone to conglomerate although the majority of the molluscan fauna is found in siltstone, very fine-grained wacke, and claystone. The lack of molluscs in the mudstone of the lower Peace Valley beds (lacustrine facies), and the presence of the fauna in the nearly stratigraphic equivalent sandstone and siltstone units of the Ridge Route formation (fluvial-deltaic facies), may suggest fluctuating salinities in the lacustrine environment with penecontemporaneous stable salinity conditions in the fluvial-deltaic environment. Deep water, high turbidity with sediment influx, or reducing conditions are alternative explanations for the paucity of molluscs. Ridge Basin nonmarine molluscs do not suggest an age for the basin. Chlamys (Chlamys) cf. C. (C.) hodgei suggests a Miocene or later age for the lowermost Ridge Route formation (Wilson 1978). The ostracodes probably indicate a late Miocene age for the lower Ridge Basin Group; however, recent magnetostratigraphy suggests an early Pliocene age for the lowermost Ridge Basin Group (Ensley and Verosub 1979)

Population Density and Reproductive Seasonality of Tryonia cheatumi (Gastropoda: Cochliopidae), the Phantom Tryonia

We studied population density, population size, and reproductive seasonality of the Phantom Tryonia, Tryonia cheatumi (Pilsbry, 1935). This endangered freshwater snail is found only in the San Solomon Spring system, a cienega, or karst-based, arid-land freshwater spring system, in western Texas, USA. We sampled populations at seven locations in the system seasonally over a 2-yr period. San Solomon Spring, the system\u27s largest spring and modified into a swimming pool, had the largest population of T. cheatumi, with an estimated 49 million individuals and a mean density as high as 23,626 ± 39,030 (individuals/m2 ± SD). There were seasonal differences in mean density (up to 25-fold) and median snail size at all sites, but consistent seasonal patterns of mean density or size were not observed. Median snail size among samples was not related to water temperature, and juveniles were present in most samples in all seasons. These results support continuous, aseasonal reproduction, as expected in thermally stable habitats, but differences in median size and mean density among seasons and sites suggest that other factors affect reproduction and seasonal variation in population size of T. cheatumi

The nature of aquatic landscapes in the Miocene of western Amazonia: An integrated palaeontological and geochemical approach

The Miocene Pebas Formation from the section Santa Rosa de Pichana (Loreto, Peru) was investigated using a combination of analyses of sedimentary facies, molluscan communities and taphonomy, and stable isotopes of both entire shells and growth bands in bivalves. Three sequences, comprising a succession of transgressive, maximum flooding and regressive/prograding intervals, are documented. Molluscs are most common in the transgressive/highstand intervals and are almost absent in regressive/prograding intervals. The fauna is dominated by endemic Pebasian species, such as Pachydon and Dyris spp. The nature of the deposits as well as the availability of oxygen varied in a predictable way within each of the sequences and determined the nature of the assemblages. Highest diversity was reached in the late transgressive phase before the development of dysoxia that was widespread during the late highstand and early regressive/prograding phase. The mollusc and isotope data show no indications of elevated salinities, in contrast to ichnofossils found in the section. This discrepancy is interpreted to result either from temporal separation of the ichnofossils and the mollusc fossils or from evolution beyond usual ecological tolerances of taxa that produced these ichnofossils into freshwater settings

MICROBIAL ASSOCIATIONS WITH METCALF’S TRYONIA, TRYONIA METCALFI (GASTROPODA: COCHLIOPIDAE), AN IMPERILED CI´ENEGA ENDEMIC

The Chihuahuan Desert swamps are a hotspot for imperiled organisms including freshwater springsnails and bacteria. Many of these taxa are endemic to the desert and to the individual waterbodies where they occur. Efforts to conserve diversity in these threatened areas must account for the life history of the organisms, but also interactions between organisms including microbes. We documented the microbial assemblage associated with Tryonia metcalfi, a critically imperiled freshwater snail endemic to a ciénega system in western Texas. We identified 14 bacterial families in our snail samples and determined a core assemblage of 19 bacterial taxa (4 of which represented novel lineages) that are likely dependent on the snail. Future conservation efforts involving T. metcalfi and its environment should therefore consider the microbial diversity associated with both the snail and the ciénegas. - En las ciénegas del desierto de Chihuahua habitan muchos organismos en peligro, entre ellos caracoles de agua dulce y bacterias. Muchos de estos taxones son endémicos del desierto y de los específicos cuerpos de agua donde ocurren. Esfuerzos para conservar la diversidad en estas áreas amenazadas deben tomar en cuenta la historia de vida de los organismos junto con las interacciones entre ellos, incluyendo microbios. Documentamos el conjunto microbiano relacionado con Tryonia metcalfi, una especie de caracol de agua dulce en peligro de extinción, endémica a un sistema de ciénagas en el oeste de Texas. Identificamos 14 familias bacterianas en nuestras muestras de caracoles y determinamos un conjunto principal de 19 taxones bacterianos; cuatro representan nuevos linajes, que probablemente dependen del caracol. En el futuro, los esfuerzos para proteger a T. metcalfi y su ambiente en consecuencia deben considerarla diversidad microbiana asociada con esta especie de caracol y la ciénega

Komposisi dan Kelimpahan Moluska (Gastropoda dan Bivalvia)

This study aims to determine the composition and abundance of mollusks (Gastropods and Bivalves) in the Aek Pala River, Labuhanbatu Regency. The method used is purposive random sampling. Sampling was carried out using a net source. The results showed that the Gastropod groups found were Pachychilidae, Ampullaridae, Littorinidae, Nassaridae, Thiaridae, Hydrobiidae, Tateidae, Spiraxidae, Vivipararidae and Batillariidae, while the Bivalvia groups were Corbiculidae and Curbulidae. In conclusion, the composition of mollusks found were 10 families of Gastropods and 2 families of Bivalves. Keywords: Bivalves, Gastropods, Abundance, Composition, Mollusc

Landscape evolution and depositional processes in the Miocene Amazonian Pebas lake/wetland system: Evidence from exploratory boreholes in northeastern Peru.

This study of the type and scales of depositional processes and landscape development in western Amazonia during the Miocene is based on the description and interpretation of three boreholes from the Marañon basin (Peru). The Miocene Pebas Formation, and the overlying Marañon Formation and underlying Chambira Formation are lithologically characterised. An age calculation model indicates an Oligocene age for the Chambira Formation, and an Early - early Late Miocene age for the Pebas Formation. The base of the Chambira Formation is placed at a sequence boundary and corresponds to the beginning of a regression. The succession was deposited in floodplains included in a RST and a LST under a seasonal climate with a pronounced dry season. The base of the Pebas Formation is placed at a TS. It represents TST and HST lacustrine and swamp settings at or near sealevel, formed in a tropical monsoon climate alike the present-day climate in the region. At the time, the area was a mosaic of lakes, swamps and fluvial belts, but experienced tidal influence as well. During apparently regularly recurring base level highstands, open aquatic settings (lakes at sea level) were widespread. The depositional system was driven by tectonic subsidence in the area, uplift and erosion in the Andean hinterland and the western rim of the Pebas system (the developing Subandean zone), delta lobe switching and river belt avulsions, as well as presumable Milankovitch scale precipitation/erosion cycles and eustatic sea level variation. The base of the Marañon Formation is placed at a sequence boundary. It represents the end of the Pebas lake/wetland system, and the change to permanent fluvial conditions during the Late Miocene RST and LST

Molluscan radiations and landscape evolution in Miocene Amazonia

This PhD study aims to exploit the rich archive provided by the Miocene mollusc fauna of the Pebas Formation and other inland Miocene Amazonian formations to reconstruct landscape evolution and biotic development in lowland Amazonia during the Neogene. Over 160 samples from more than 70 Pebas Formation outcrops mostly collected by the author were processed for this study. Additional samples were collected in Andean areas of Colombia and Venezuela and further material from other northwestern South American basins was studied in museums. Pebas Formation samples and well log data made available by Occidental Peru from three wells in the Marañon Basin in Peru were also investigated. During this study four genera and 74 species from the Pebas Formation have been described and a further 13 species have been introduced in open nomenclature, and several species were reported for the first time. The number of mollusc species attributed to the Pebas fauna has increased from around 50 to 156. The Pebas fauna is characterised as aquatic, endemic and extinct, and is a typical representative of a long-lived lake fauna. Fluvial taxa are not common, (marginal) marine taxa are rare. An additional molluscan fauna from the Miocene Solimões Formation of Brazil, containing 13 fresh water species was also described. The newly documented fauna was used to improve biostratigraphic framework of Miocene Amazonian deposits. Twelve mollusc zones were introduced, the upper eleven of which cover a time interval of approximately seven million years covered previously by only three pollen zones. An age model calculated for the borehole data indicates that the Pebas Formation was deposited between c. 24 and 11 Ma. The areal distribution of the outcropping mollusc zones uncovered a broad dome structure, termed here the Iquitos-Araracuara anteclise in the study area. The structure appears to have influenced river courses and also contributed to edaphic heterogeneity that may have been in part responsible for the current high biodiversity in the study area. The Pebas system was a huge system (> one million km2) dominated by relatively shallow lakes, but also containing swamps and rivers. The system was fed by rivers draining the emergent Andes in the west and lowlands and cratons to the east. The Pebas system was located at sea level and was open to marine settings through a northern portal running through the Llanos Basin and East Venezuela Basin towards the Caribbean. Cyclical baselevel changes possibly related to Mylankhovitch cycles, have been documented in depositional sequences of the Pebas Formation. The composition of the Pebasian mollusc fauna implies that the system was mostly a fresh water system. Such an interpretation is matched by strontium isotope ratios as well as very negative δ18O ratios found in the shells, but is at odds with oligohaline and mesohaline ichnofacies found in the same strata. The mollusc fauna of the Pebas Formation diversified through most of the existence of the lake system. The diversification was mostly the result of in-situ cladogenesis. The success of some of the Pebasian endemic clades is explained by adaptation to fresh water, low oxygen, common unconsolidated lake bottoms (soup grounds) as well as high predation intensity. Maximum diversity was reached at the base of the late Middle to early Late Miocene Grimsdalea pollen zone, some 13 Ma. At the time some 85 species co-occurred, 67 of which are considered as Pebasian endemics. A subsequent drop in species richness coincides with indications of elevated salinities, although a causal relation still needs to be established. Apparently the Pebas fauna went (almost) entirely extinct with the replacement of the lake system into a fluvio-tidal system during the Early Late Miocene, some 11 Ma.Siirretty Doriast