Hydroecology of Amazonian lacustrine Arcellinida (testate amoebae): A case study from Lake Quistococha, Peru

Organic rich sediments were obtained from seven core tops taken in Lake Quistococha, near the city of Iquitos in the Peruvian Amazon. Subsamples from 0 to 4 cm depth in each core were analyzed under dissecting light microscopy to carry out the first investigation of Arcellinida (testate lobose amoebae) from a lacustrine environment in this ecologically important region. The fauna was characterized by a low diversity, low abundance community dominated by centropyxids. This fauna is similar to ‘stressed’ assemblages reported from temperate latitudes, except that test concentrations were two orders of magnitude lower than typical in temperate lakes. Principle arcellinidan stressors in Lake Quistococha likely include the low pH 4 conditions in the lake, and a general lack of suitable minerogenic material to construct tests in the organic rich lake substrate. The low pH conditions are the result of runoff and seepage of water high in dissolved organic carbon from the adjacent similarly low pH 4 terrestrial peatland. The dearth of minerogenic material is the result of the lake being isolated from riverine input for the past ∼2000 years, even during flooding events. Other limiting factors contributing to depressed arcellinidan populations may include nutrient supply, predation pressure, competition, and post-mortem taphonomic factors

Een ongelukkige samenloop van omstandigheden

Het artikel bevat een kritische analyse van de jurisprudentie van de HR geen aansprakelijkheid aan te nemen voor ongelukjes in de privésfeer, omdat dat zou berusten op een ongelukkige samenloop van omstandigheden

SOME SPECIES OF THE GENERA MELANOSTOMA PLATYCHEIRUS AND PYROPHAENA DIPTERA SYRPHIDAE AND THEIR RELATION TO FLOWERS

Volume: 30Start Page: 135End Page: 14

Non-pollen palynomorph studies in the Neotropics: the case of Venezuela

This paper summarises the NPP studies developed so far in a wide range of environments from Venezuelan lowlands, midlands and highlands, as an example of a growing discipline in a Neotropical area. The studies discussed include both modern analogues from surface sediments and Late Quaternary sequences combining pollen and spores with NPP analyses. Emphasis is placed on the utility of NPP as palaeoecological indicators both individually and collectively (NPP assemblages), as well as in combination with other proxies. The main advantages of using NPP instead of only pollen and spores are highlighted using case studies as examples. Among them, the occurrence of NPP in samples barren for pollen and spores, the independent indicator nature of NPP, and their capacity to reveal previously unnoticed environmental shifts (notably those related to local conditions), are emphasised. The main results obtained in all these analyses are discussed in the frame of several areas of the NPP study that are considered crucial (methods, taxonomy, indicator value and statistical treatment). Some ideas for future developments are proposed in each of these areas, and the need for closer collaboration among NPP specialists is strengthened, in a way towards unification and standardisation