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1

Electronic Resource

Biochemical composition of algivorous freshwater ciliates: You are not what you eat (2005)

Boëchat, Iola G. ; Adrian, Rita

Oxford, UK : Blackwell Publishing Ltd

FEMS microbiology ecology 53 (2005), S. 0

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ISSN: 1574-6941

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The focus of our study was to determine whether the biochemical composition of two algivorous ciliates, both fed the same alga, resembles that of their diet. By comparing both ciliated protozoa we intended to identify species-specific differences in the metabolic features of these ciliates. Carbon- and cell-specific concentrations of fatty acids and essential amino acids were investigated for the ciliates Balanion planctonicum and Urotricha farcta grown on the cryptomonad Cryptomonas phaseolus. Stepwise discriminant analyses (SDA) indicated differences in the biochemical composition between ciliates and their diet and between the two ciliated protozoa. Carbon-specific fatty acid concentrations were usually higher in the ciliates than in their diet, especially concentrations of monounsaturated and some polyunsaturated fatty acids. Except for tryptophan, valine, and lysine, amino acid concentrations were higher in the ciliates than in C. phaseolus. Furthermore, differences in the polyunsaturated fatty acids accounted for the largest discrepancies between the two ciliated protozoa. The higher concentrations in the ciliates compared to their diet suggest that these species are capable of efficiently ingesting, assimilating or possibly synthesizing some fatty acids and amino acids. We conclude that dietary fatty acid and amino acid composition influences the composition of the two ciliated protozoa to a minor extent, and that species-specific differences in fatty acid and amino acid metabolism may be more important determinants of the biochemical composition of the studied ciliates. Moreover, the metabolism of polyunsaturated fatty acids seems to differ more profoundly between the two ciliated protozoa than the metabolism of other fatty acid classes or amino acids.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1016/j.femsec.2005.01.005

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2

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Species-specific changes in the phenology and peak abundance of freshwater copepods in response to warm summers (2002)

Gerten, Dieter ; Adrian, Rita

Oxford, UK : Blackwell Science Ltd

Freshwater biology 47 (2002), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: SUMMARY 1. Climate warming is now widely recognised as a major factor influencing ecological processes in terrestrial, marine and freshwater habitats. Here, we investigated how a recent period of warm springs and summers has affected the population dynamics of various cyclopoid copepods in a central European lake. We compared (i) the duration of the period when the species were present in the water column, and (ii) their annual peak density in a period dominated by cool summers (1980–91) and one dominated by warm summers (1992–99).2. The copepods under investigation were (i) Thermocyclops oithonoides, (ii) Mesocyclops leuckarti and (iii) Acanthocyclops robustus. These species differ in their thermal demand and seasonal phenology. Therefore, we hypothesised that enhanced summer warming would produce species-specific responses.3. The active phase of the copepods was usually prolonged both in spring and autumn. The earlier emergence of T. oithonoides (May in the warm years, July in the cool years) was probably related to high water temperature in late spring. The later onset of winter diapause in all species may have been coupled to raised temperature in late summer and autumn.4. The annual peak abundance of the two thermophiles M. leuckarti and T. oithonoides increased significantly in the warm period. In the latter case, the increase was probably because of the early start to population growth. In contrast, M. leuckarti probably responded primarily to mid-summer heat waves, in that its development time was likely to be short. We speculate that the increase in population size of both species resulted from the development of an additional generation (three instead of two cohorts per year). In contrast to these thermophiles, the coexisting A. robustus, which is adapted to a broader temperature range, did not respond noticeably to the warming trend.5. In general, the nature of these responses to summer warming varied substantially among species, and depended on the detailed seasonal patterning of the warming. Our findings thus support the hypotheses that single species are sensitive indicators of climate change, and that the seasonal timing of warming is crucial in the context of climate–ecosystem relationships.6. Moreover, our results add to the body of evidence that climate warming produces shifts in the seasonal phenology of aquatic and terrestrial organisms.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2002.00970.x

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3

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Possible impact of mild winters on zooplankton succession in eutrophic lakes of the Atlantic European area (1996)

ADRIAN, RITA ; DENEKE, RAINER

Oxford BSL : Blackwell Science Ltd

Freshwater biology 36 (1996), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. We report on a long-term study (1975–94) of water temperatures and plankton in a eutrophic lake (Heiligensee, Berlin, Germany). Using a phenomenological approach, we use historical data to infer how an increase in air temperature has influenced a natural zooplankton community.2. Air temperatures in Berlin showed a significantly rising trend between 1975 and 1994. Mean winter air temperatures in the last 8 years always exceeded the long-term mean.3. A rising trend was also found for April water temperature, which increased significantly beginning in 1988–89. An increase of 2.58°C in the last 21 years was recorded using a linear model. A significantly decreasing trend was found in June but no trend was noted for the other summer months.4. Phytoplankton composition shifted from a dominance of diatoms and cryptophytes during winter and spring in the 1980s towards a dominance of cyanobacteria in 1990–94.5. The dominant zooplankton species in spring shifted in recent years from the large-bodied Daphnia galeata to the smaller D. cucullata. Cyclops kolensis, previously the only invertebrate predator during winter, decreased in abundance while C. vicinus, usually present during spring and autumn, increased in abundance and was numerous during winter, a season passed in diapause in the earlier years.6. Because direct and indirect temperature effects are species specific, we put forward the hypothesis that zooplankton species, rather than functional groups, are the nexus between environmental stress, such as rising air temperatures, and ecosystem changes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.1996.00126.x

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4

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The North Atlantic Oscillation and plankton dynamics in two European lakes –- two variations on a general theme (2000)

Straile, Dietmar ; Adrian, Rita

Oxford, UK : Blackwell Science Ltd

Global change biology 6 (2000), S. 0

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ISSN: 1365-2486

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography

Notes: Long-term data on water temperature, phytoplankton biovolume, Bosmina and Daphnia abundance and the timing of the clear-water phase were compared and analysed with respect to the influence of the North Atlantic Oscillation (NAO) in two strongly contrasting lakes in central Europe. In small, shallow, hypertrophic Müggelsee, spring water temperatures and Daphnia abundance both increased more rapidly than in large, deep, meso/oligotrophic Lake Constance. Because of this, the clear-water phase commenced approximately three weeks earlier in Müggelsee than in Lake Constance. In Müggelsee, the phytoplankton biovolume during late winter/early spring was related to the NAO index. In Lake Constance, where phytoplankton growth was inhibited by intense downward mixing during all years studied, this was not the case. However, in both lakes, interannual variability in water temperature, in Daphnia spring population dynamics and in the timing of the clear-water phase, were all related to the interannual variability of the NAO index. The Daphnia spring population dynamics and the timing of the clear-water phase appear to be synchronized by the NAO despite large differences between the lakes in morphometry, trophic status and flushing and mixis regimes, and despite the great distance between the lakes (∼700 km). This suggests that a great variety of lakes in central Europe may possibly have exhibited similar interannual variability during the last 20 years.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2486.2000.00350.x

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5

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Reproductive success of the rotifer Brachionus calyciflorus feeding on ciliates and flagellates of different trophic modes (2002)

Mohr, Silvia ; Adrian, Rita

Oxford, UK : Blackwell Science Ltd

Freshwater biology 47 (2002), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: SUMMARY 1. The nutritional value of the bacterivorous ciliate Tetrahymena pyriformis and the algivorous ciliate Coleps sp., as well as the heterotrophic flagellate Chilomonas paramecium and the autotrophic flagellate Cryptomonas ovata, were investigated in population growth experiments using the rotifer B. calyciflorus. The two ciliates, both flagellates, which were of similar size, shape and mobility, were each offered as a sole diet and as a supplement to the alga Monoraphidium minutum, known to support reproduction of B. calyciflorus.2. To further test nutritional differences between the prey organisms, prey selection experiments were conducted in which B. calyciflorus was able to select between the bacterivorous and algivorous ciliate, and between the heterotrophic and autotrophic flagellate.3. The results demonstrated that both ciliates and the heterotrophic flagellate were not sufficient to support reproduction of B. calyciflorus when offered as a sole diet. They were, however, a good supplement to algal prey (except for the bacterivorous ciliate T. pyriformis). In the prey selection experiments, B. calyciflorus positively selected for the algivorous Coleps sp. and the autotrophic C. ovata.4. Overall, ciliates and heterotrophic flagellates may enhance survival of B. calyciflorus, but reproduction of the rotifer is likely to rely on algal prey. Both higher population growth of B. calyciflorus when fed the algivorous Coleps and the autotrophic Cryptomonas, along with their positive selection, give evidence for prey specific differences in nutrition, with algivorous or autotrophic prey species tending to be of higher nutritional value.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2002.00929.x

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6

Electronic Resource

Calanoid–cyclopoid interactions: evidence from an 11-year field study in a eutrophic lake (1997)

ADRIAN, RITA

Oxford, UK : Blackwell Science Ltd

Freshwater biology 38 (1997), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. The interactions between calanoid and cyclopoid copepods were examined in an 11-year field study of a eutrophic lake (Heiligensee, Berlin, Germany).2. A diminishing ratio of calanoids to cyclopoids was observed. The responses, however, were species specific. While two cyclopoid species responded with increased populations (Cyclops vicinus, Thermocyclops oithonoides), one species exhibited marked declines (C. kolensis). Other species extended the duration of their pelagic phase (Mesocyclops leuckarti, Diacyclops bicuspidatus, T. oithonoides, C. vicinus), leading to higher population overlaps. Eudiaptomus graciloides and E. gracilis, which used to be present throughout the year, were more frequently absent.3. These changes coincided with a series of mild winters during which prey availability (algae and rotifers) was high.4. Enhanced prey availability, in conjunction with a flexible diapausing strategy, are hypothesized to underly the increased success of C. vicinus. Predatory losses due to early occurrence and enhanced abundances of C. vicinus, rather than competition for the same food resources, are hypothesized to be responsible for the declines of C. kolensis and Eudiaptomus.5. Summer species tended to develop higher abundances early in the season, which led to enhanced seasonal means during spring. These changes cannot be explained by the interaction between calanoids and cyclopoids alone, but were probably a result of changes in fish predation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.1997.00215.x

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7

Electronic Resource

Effects of ice duration on plankton succession during spring in a shallow polymictic lake (1999)

Adrian, Rita ; Walz, Norbert ; Hintze, Thomas ; [et al.]

Oxford, UK : Blackwell Science, Ltd

Freshwater biology 41 (1999), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. Long-term records of air temperature and ice phenology (ice duration), and phyto- and zooplankton time series (1979–1997) were used to study the effects of ice duration on the successional pattern within plankton communities during spring in a shallow polymictic lake.2. Water temperature in March was significantly lower after cold winters when compared to average or mild winters. Mean water temperature in April was not significantly different after mild, average or cold winters, but showed an overall significant negative correlation with ice duration.3. Ice duration affected the timing and the magnitude of the peak abundance of diatoms, rotifers and daphnids during spring, but had no direct effects on the timing and maximum of chlorophytes, cryptophytes, cyanobacteria, bosminids and cyclopoid copepods.4. Plankton groups which appeared first in the seasonal succession (i.e. diatoms, rotifers and daphnids) reached maximum abundance earlier after mild and average winters. The peak abundance of diatoms was negatively correlated with ice duration, whereas that of rotifers and daphnids was independent of the conditions during the preceding winter.5. Temperature alone was generally a poor predictor of the timing and magnitude of both phyto- and zooplankton maxima. Turbulence may be important in the timing and the magnitude of peaks in diatoms, while total algal biomass was the most important determinant for the timing of the rotifer maximum. The magnitude of the daphnid maxima were significantly influenced by water temperature in March and April, and by rotifer abundance. The magnitude of the bosminid maximum was correlated with food availability and predation, whereas the timing of the maximum was more closely related to water temperature in May.6. We conclude that, as a result of the low heat storage capacity of shallow lakes, the effects of winter on planktonic communities are short lived, and soon overtaken by the prevailing weather and by biotic interactions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.1999.00411.x

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8

Electronic Resource

Filtering and feeding rates of cyclopoid copepods feeding on phytoplankton (1991)

Adrian, Rita

Springer

Hydrobiologia 210 (1991), S. 217-223

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ISSN: 1573-5117

Keywords: Cyclops kolensis ; C. vicinus ; in situ and laboratory grazing experiments

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The algal biomass ingested by omnivorous cyclopoid copepods (Cyclops kolensis and C. vicinus) was measured by two methods in the hypertrophic Heiligensee in Berlin (West Germany). The clearance and ingestion rates inferred from measurements of natural populations of 14C labelled phytoplankton were compared with those obtained from chlorophyll a determinations using the presence/absence method (observed chlorophyll a content of natural lake phytoplankton with and without addition of cyclopoids). Both methods gave similar results. Nevertheless, the radio tracer method is preferred, mainly because the short feeding duration excludes high variations in both the food composition and food concentration that limit the presence/absence method.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00034680

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Evaluating early-warning indicators of critical transitions in natural aquatic ecosystems (2016)

Gsell, Alena Sonia ; Scharfenberger, Ulrike ; Özkundakci, Deniz ; [et al.]

National Academy of Sciences

In: PNAS - Proceedings of the National Academy of Sciences of the United States of America. 2016; 113(50): E8089-E8095. Published 2016 Nov 22. doi: 10.1073/pnas.1608242113.

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Publication Date: 2016-11-22

Description: Ecosystems can show sudden and persistent changes in state despite only incremental changes in drivers. Such critical transitions are difficult to predict, because the state of the system often shows little change before the transition. Early-warning indicators (EWIs) are hypothesized to signal the loss of system resilience and have been shown to precede critical transitions in theoretical models, paleo-climate time series, and in laboratory as well as whole lake experiments. The generalizability of EWIs for detecting critical transitions in empirical time series of natural aquatic ecosystems remains largely untested, however. Here we assessed four commonly used EWIs on long-term datasets of five freshwater ecosystems that have experienced sudden, persistent transitions and for which the relevant ecological mechanisms and drivers are well understood. These case studies were categorized by three mechanisms that can generate critical transitions between alternative states: competition, trophic cascade, and intraguild predation. Although EWIs could be detected in most of the case studies, agreement among the four indicators was low. In some cases, EWIs were detected considerably ahead of the transition. Nonetheless, our results show that at present, EWIs do not provide reliable and consistent signals of impending critical transitions despite using some of the best routinely monitored freshwater ecosystems. Our analysis strongly suggests that a priori knowledge of the underlying mechanisms driving ecosystem transitions is necessary to identify relevant state variables for successfully monitoring EWIs.

Print ISSN: 0027-8424

Electronic ISSN: 1091-6490

Topics: Biology , Medicine , Natural Sciences in General