Continuous monitoring of phytoplankton dynamics in Lake Balaton (Hungary) using on-line delayed fluorescence excitation spectroscopy

1. This study introduces delayed fluorescence (DF) excitation spectroscopy as an on‐line tool for in situ monitoring of the composition and biomass of various colour classes of phytoplankton when they are photosynthetically active (cyanobacteria, chlorophytes, chromophytes and cryptophytes). The DF data are validated by comparison with those from conventional methods (weekly microscopic counts and the measurement of chlorophyll concentration). 2. The composition of phytoplankton as assessed by DF agreed reasonably well with the results from microscopic counts, particularly when differences in chlorophyll‐specific DF integrals of the various colour classes were taken into account. 3. Integrals of DF spectra were converted into concentration of chlorophyll a using empirical factors derived from field data. The value of the conversion factor was nearly twice as high when the relative abundance of cyanobacteria was low (<15%) than when it was high. The converted DF‐chl time series agreed well with chlorophyll measurements particularly when blooms were developing. As the DF method is inherently free of the interference caused by pigment degradation products, the discrepancy between the two data sets increased during the collapse of blooms and when sediment resuspension was intense. 4. Fourier spectrum analysis of the time series of DF‐chl indicated that samples must be taken, at a minimum, every 2–3 days to capture the dynamics of phytoplankton. As a consequence, the dynamics of various algal blooms, including their timing, duration and net growth rate, could be estimated with greater confidence than by using conventional methods alone. 5. On‐line DF spectroscopy is an advanced technique for monitoring daily the biomass and composition of the photosynthetically active phytoplankton in aquatic environments, including turbid shallow lakes. At present, the detection limit is around 1 mg DF‐chl a m^?3 in terms of total biomass but confidence in estimates of phytoplankton composition declines sharply below about 5 mg chl a m^?3. 6. On‐line DF spectroscopy represents a promising approach for monitoring phytoplankton. It will be useful in water management where it can act as an early‐warning system of declines in water quality. In basic ecological research it can supplement manual methods. While default calibration spectra may be acceptable for routine monitoring, we suggest a careful individual calibration of the DF spectrometer for basic research. The statistical methods developed here help to assess the adequacy of various calibration sets.     

A comparison of estimates of relative abundance from a weakly structured mass‐participation bird atlas survey and a robustly designed monitoring scheme

Estimates of population size are frequently used in conservation. Volunteer‐conducted surveys are often the only source of information available, but their reliability is unclear. We compare data from a weakly structured national bird atlas collected by volunteer surveyors free to choose where and when to visit with data from an independent suite of monitoring surveys that used a stratified sampling design. We focus on the Mount Lofty Ranges, South Australia, a region that has lost most of its native vegetation. Both datasets comprise several thousand 20‐min 2‐ha searches carried out between 1999 and 2007. The atlas dataset reported more species, and covered habitats more comprehensively, but showed greater variability in the temporal and spatial distribution of survey effort. However, after we restricted the atlas dataset to native eucalypt woodlands, reporting rates from the two schemes were very strongly correlated. The structured surveys tended to record more species that are normally detected by call and the unstructured surveys recorded more species using edges and open habitats. Minimum population estimates from the two datasets agreed very well. The strength of concordance depended on whether overflying birds were included, highlighting the importance of distinguishing such records in future surveys. We conclude that appropriate calibration using selected regional surveys, including surveys to estimate absolute densities, can enable volunteer‐collected and weakly structured atlas data to be used to generate robust occupancy and minimum population estimates for many species at a regional scale.     

Phytoplankton equilibrium phases during thermal stratification in a deep subtropical reservoir

1. Equilibrium and non-equilibrium hypotheses have often been used to explain observations in community ecology. Published case studies have demonstrated that steady state phytoplankton assemblages are more likely to occur in deep lakes than in shallow mixed ones.
2. Phytoplankton seasonal succession was studied by weekly sampling in Faxinal Reservoir (S Brazil), a subtropical deep, clear, warm monomictic and slightly eutrophic reservoir. This study demonstrated an alternation of steady and non-steady state phases of phytoplankton assemblages with different dominant species during the steady states.
3. During the studied period, three steady states were identified with different dominant algal species: Anabaena crassa (Cyanobacteria), Nephrocytium sp. (green algae) and Asterionella (diatoms).
4. Each steady state in Faxinal Reservoir developed under stratified conditions of the water column according to the predictions of the disturbance concepts. Apparently, the major forces driving the development and persistence of these steady-state phases were closely related to thermal stratification and its consequences.
5. This study is the first report on development of more than one steady state within a year in a stratified water body. The development of three steady states might be the result of the relatively long stratification period in the Faxinal Reservoir and to its unique geochemical features.     

Crossing the Tasman Sea: Inferring the introduction history of Litoria aurea and Litoria raniformis (Anura: Hylidae) from Australia into New Zealand

Abstract The amphibian fauna of New Zealand consists of three native species (Leiopelma spp.), and three Litoria species introduced from Australia in the last 140 years. We conducted a molecular phylogeographical study that aimed to identify the Australian origins of two species, Litoria aurea and Litoria raniformis. We used partial sequences of the mitochondrial cytochrome oxidase I (cox1) gene from 59 specimens sampled from across the range of both species to identify the probable source populations for the New Zealand introductions, and to describe the current genetic diversity among New Zealand Litoria populations. Our genetic data suggest that L. aurea was introduced into the North Island of New Zealand from two regions in Australia, once from the northern part of coastal New South Wales and once from the southern part of coastal New South Wales. Our data indicate that L. raniformis introductions originated from the Melbourne region of southern Victoria and once established in the South Island of New Zealand, the species subsequently spread throughout both islands. In addition, we found a distinct haplotype in L. raniformis from Tasmania that strongly suggests, contrary to earlier reports, that this species was not introduced into New Zealand from Tasmania. Finally, we identified two very distinctive mitochondrial lineages of L. raniformis within the mainland Australia distribution, which may be previously unrecognized species.     

Sequential colonization by river periphyton analysed by microscopy and molecular fingerprinting

1. An artificial glass substratum was incubated in the River Danube for a period of 28 days in order to detect the sequential colonization of microorganisms.
2. Light and fluorescent microscopy showed that microalgae and the picoalgal fraction on the slides increased rapidly over the first 2 weeks of colonization. Diatoms were numerically the most abundant component of the periphyton and their species richness and diversity increased rapidly in the early phase of colonization whereas diversity subsequently increased moderately.
3. Evenness of the diatom community was initially high, lower in the intermediate phase and again higher later on. Succession involving early, intermediate and late colonizer species was observed. Community composition during the first 5 days of colonization was very different from later stages whereas there were only minor changes subsequently.
4. Molecular community analysis by means of terminal restriction fragment length polymorphism analysis of PCR amplified 16S rRNA and 18S rRNA genes pointed to even larger differences between the composition of samples obtained early and late in the period.
5. The number of 18S rRNA and 16S rRNA terminal restriction fragments (T-RF-s) was variable over the colonization period and the fragment patterns of both the bacterial and eukaryotic portion of the microbial community were variable, with most T-RF-s unique to a single sample, suggesting a wide diversity and dynamic properties of periphytic organisms.     

Will European soil-monitoring networks be able to detect changes in topsoil organic carbon content?

Within the United Nations Framework Convention on Climate Change, articles 3.3 and 3.4 stipulate that some voluntary activities leading to an additional carbon (C) sequestration in soils could be accounted as C sinks in national greenhouse gas inventories. These additional C stocks should be verifiable. In this work, we assess the feasibility of verifying the effects of changes in land use or management practice on soil organic carbon (SOC), by comparing minimum detectable changes in SOC concentration for existing European networks suitable for soil monitoring. Among the tested scenarios, the minimum detectable changes differed considerably among the soil-monitoring networks (SMNs). Considerable effort would be necessary for some member states to reach acceptable levels of minimum detectable change for C sequestration accounting. For SOC, a time interval of about 10 years would enable the detection of some simulated large changes in most European countries. In almost all cases, the minimum detectable change in SOC stocks remains greater than annual greenhouse gases emissions. Therefore, it is unlikely that SMNs could be used for annual national C accounting. However, the importance of organic C in soil functions, and as an indicator of soil condition and trends, underlines the importance of establishing effective national SMNs.     

Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) and Ca2+ Mobilization

Many physiological processes are controlled by a great diversity of Ca^{2 +} signals that depend on Ca^{2 +} entry into the cell and/or Ca^{2 +} release from internal Ca^{2 +} stores. Ca^{2 +} mobilization from intracellular stores is gated by a family of messengers including inositol-1,4,5-trisphosphate (InsP₃), cyclic ADP-ribose (cADPR), and nicotinic acid adenine dinucleotide phosphate (NAADP). There is increasing evidence for a novel intracellular Ca^{2 +} release channel that may be targeted by NAADP and that displays properties distinctly different from the well-characterized InsP₃ and ryanodine receptors. These channels appear to localize on a wider range of intracellular organelles, including the acidic Ca^{2 +} stores. Activation of the NAADP-sensitive Ca^{2 +} channels evokes complex changes in cytoplasmic Ca^{2 +} levels by means of channel chatter with other intracellular Ca^{2 +} channels. The recent demonstration of changes in intracellular NAADP levels in response to physiologically relevant extracellular stimuli highlights the significance of NAADP as an important regulator of intracellular Ca^{2 +} signaling.     

Population dynamics of the freshwater dinoflagellate Ceratium hirundinella in the largest shallow lake of Central Europe, Lake Balaton, Hungary

SUMMARY.

• 1 Horizontal distribution, long-term (1933–82) and short-term (day-to-day) changes in abundance, vertical stratification and circadian rhythm of the freshwater dinoflagellate Ceratium hirtmdinella were studied in Lake Balaton, the largest shallow lake of Central Europe.
• 2 The lowest abundance was consistently found in those areas of the lake which had the strongest currents.
• 3 The density of C. hirundinella seemed to be, at least in those parts of the lake above the level of fertility considered oligotrophic, insensitive to changes in trophic conditions; only its relative contribution to total biomass decreased with increased enrichment.
• 4 During the day the bulk of the population stayed at a level in which the light intensity was between 126 and 440 μE m^-2 s^-1 PAR.

     

Oviposition preferences of Maculinea alcon as influenced by aphid (Aphis gentianae) and fungal (Puccinia gentianae) infestation of larval host plants

Abstract 1. The influence of infestation of the larval host plant Gentiana cruciata on the egg‐laying preferences of the xerophilous ecotype of Alcon Blue butterfly (Maculinea alcon) was studied in a semi‐dry grassland area (Aggtelek Karst Region, Northern Hungary). 2. We examined whether oviposition patterns of females differed when G. cruciata stems were uninfested compared with when they were infested by an aphid (Aphis gentianae) or a rust (Puccinia gentianae) species. 3. Females laid more than 90% of their eggs on fertile, uninfested G. cruciata stems, although these stems comprised only ～ 50% of the total stems available. Stems infested by aphids were similar to uninfested ones in properties that had a strong correlation with egg numbers, and yet there were significantly fewer eggs on infested stems than on intact ones. 4. Females never laid eggs on parts of Gentiana stems infested by aphids, and the presence of Lasius paralienus ants, which have a mutualistic interaction with Aphis gentianae, did not increase the repulsive effect of aphids. Infection of Gentiana by Puccinia did not influence the egg‐laying behaviour of females, even though the flowers and buds of infested stems exhibited a delayed development. 5. Aphid infestation can influence butterfly oviposition patterns through both direct and indirect effects. The presence of aphids directly excluded oviposition, but our data also indicated the possibility of an indirect effect of aphid infestation. Stems that had no aphids at the last egg counting, but were infested prior to it, had significantly fewer eggs than those that were never infested.