Pub Date : 2006-09-01DOI: 10.1127/0003-9136/2006/0167-0217
L. Meester, J. Vanoverbeke, K. D. Gelas, R. Ortells, P. Spaak
The genetic structure of cyclic parthenogenetic zooplankton populations is strongly determined by the consequences of combining sexual and asexual reproduction in the same life cycle. Since the pioneering population genetic studies on freshwater zooplankton in the 1970's, a distinction has been made between the genetic structure of permanent and intermittent populations. However, the results of many studies do not fit the expectations of this dichotomous model, for example when large lake populations are considered. In this paper, we present a unifying framework for understanding the genetic structure of cyclic parthenogenetic zooplankton populations, focusing on three factors that determine their degree of clonality and within-population genetic diversity as well as their among-population genetic differentiation: the size of the dormant egg bank, length of the growing season, and strength of clonal selection. We illustrate the importance of each of these factors, and show that our broader concept better explains the variation in genetic structure observed in natural populations of cyclic parthenogens than the earlier implicitly dichotomous model.
{"title":"Genetic structure of cyclic parthenogenetic zooplankton populations - a conceptual framework","authors":"L. Meester, J. Vanoverbeke, K. D. Gelas, R. Ortells, P. Spaak","doi":"10.1127/0003-9136/2006/0167-0217","DOIUrl":"https://doi.org/10.1127/0003-9136/2006/0167-0217","url":null,"abstract":"The genetic structure of cyclic parthenogenetic zooplankton populations is strongly determined by the consequences of combining sexual and asexual reproduction in the same life cycle. Since the pioneering population genetic studies on freshwater zooplankton in the 1970's, a distinction has been made between the genetic structure of permanent and intermittent populations. However, the results of many studies do not fit the expectations of this dichotomous model, for example when large lake populations are considered. In this paper, we present a unifying framework for understanding the genetic structure of cyclic parthenogenetic zooplankton populations, focusing on three factors that determine their degree of clonality and within-population genetic diversity as well as their among-population genetic differentiation: the size of the dormant egg bank, length of the growing season, and strength of clonal selection. We illustrate the importance of each of these factors, and show that our broader concept better explains the variation in genetic structure observed in natural populations of cyclic parthenogens than the earlier implicitly dichotomous model.","PeriodicalId":8118,"journal":{"name":"Archiv Fur Hydrobiologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79103838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-09-01DOI: 10.1127/0003-9136/2006/0167-0135
R. Tollrian, C. Laforsch
The seasonal change in helmet size in Daphnia cucullata has been studied for over one century. Recently it has been shown that helmets in D. cucullata, which have been found to reduce predator caused mortality, can be induced by chemical cues released by several predatory invertebrates. However, it also has been shown that tur- bulence induces this trait. The relation and interplay of both inducing cues is not known. Here we present results from lab experiments showing that predator cues and turbulence can act synergistically. Both factors in combination induced significantly larger responses, compared to each factor alone, and helmets reached the maximum sizes found in natural lakes. This result might help to explain the observation of large helmets in this species in nature. The ultimate reason behind the turbulence induction is yet unknown. We link both induction factors to predation, as the ultimate reason, by testing the hypothesis that D. cucullata can respond to turbulence produced by swimming invertebrates. We found that helmet growth increased significantly in direct contact to both the heterospecific Daphnia magna and the predator Cyclops sp. Treat- ments which accounted for chemical cues alone did not increase helmet growth in re- sponse to cues from D. magna ,o rCyclops under these conditions. Together, these re- sults indicate that D. cucullata is able to respond to mechanical cues produced by swimming invertebrates. Thus, our study suggests that both chemical cues and turbu- lence generated by predatory invertebrates might act synergistically to induce helmets as effective protection against invertebrate predation.
{"title":"Linking predator kairomones and turbulence: synergistic effects and ultimate reasons for phenotypic plasticity in Daphnia cucullata","authors":"R. Tollrian, C. Laforsch","doi":"10.1127/0003-9136/2006/0167-0135","DOIUrl":"https://doi.org/10.1127/0003-9136/2006/0167-0135","url":null,"abstract":"The seasonal change in helmet size in Daphnia cucullata has been studied for over one century. Recently it has been shown that helmets in D. cucullata, which have been found to reduce predator caused mortality, can be induced by chemical cues released by several predatory invertebrates. However, it also has been shown that tur- bulence induces this trait. The relation and interplay of both inducing cues is not known. Here we present results from lab experiments showing that predator cues and turbulence can act synergistically. Both factors in combination induced significantly larger responses, compared to each factor alone, and helmets reached the maximum sizes found in natural lakes. This result might help to explain the observation of large helmets in this species in nature. The ultimate reason behind the turbulence induction is yet unknown. We link both induction factors to predation, as the ultimate reason, by testing the hypothesis that D. cucullata can respond to turbulence produced by swimming invertebrates. We found that helmet growth increased significantly in direct contact to both the heterospecific Daphnia magna and the predator Cyclops sp. Treat- ments which accounted for chemical cues alone did not increase helmet growth in re- sponse to cues from D. magna ,o rCyclops under these conditions. Together, these re- sults indicate that D. cucullata is able to respond to mechanical cues produced by swimming invertebrates. Thus, our study suggests that both chemical cues and turbu- lence generated by predatory invertebrates might act synergistically to induce helmets as effective protection against invertebrate predation.","PeriodicalId":8118,"journal":{"name":"Archiv Fur Hydrobiologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89105364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-09-01DOI: 10.1127/0003-9136/2006/0167-0101
Z. Gliwicz, Piotr Dawidowicz, P. Maszczyk
We used a flow-through experimental system ("plankton organ") to test if Daphnia hyalina x galeata (Dhg), D. cucullata (Dc) and Chaoborus flavicans (Ch) take higher risks of predation at low population density levels than at high ones, i. e. to test whether or not they select shallower depths with higher temperatures and higher food levels when they do not receive chemical information on crowding (added to the medium with fish kairomones). Neonates of Daphnia and Chaoborus 4 th instar larvae were first grown for 55 h in batch cultures: Daphnia were reared at high food levels (Scenedesmus obliquus) and at two different population densities of 1 and 100 ind. L -1 (Dhg and Dc); Chaoborus were kept at densities of 1 and 10 ind. L -1 without food. After 55 h, individual Daphnia 2 nd instar juveniles were transferred into the narrow vertical tubes of a "plankton organ" with constant flow of fresh medium. The medium contained chemical information on either high or low population density; all media had the same food and fish kairomone levels. The same setup was used for individual Chaoborus 4 th instar larvae, but using media without food. Whereas no difference was found in Dc, different depth selection behavior was apparent in Dhg. The daytime depth selected by the animals was greater in the presence of chemical information on high population density, and this behavior became more pronounced with increasing duration of the experiment. The difference was highly significant for the entire dataset. The calculated duration time of egg development was up to 17% longer and the calculated birth rate 12% reduced for Daphnia receiving high-density information, as compared to control animals enjoying higher temperatures of the shallower and warmer strata. Only minor and inconsistent difference was found for Chaoborus.
我们使用了一个流动实验系统(“浮游生物器官”)来测试水蚤(Daphnia hyalina x galeata, Dhg)， D. cucullata (Dc)和Chaoborus flavicans (Ch)在低种群密度下是否比在高种群密度下有更高的捕食风险，即测试当它们没有接收到关于拥挤的化学信息(添加到含有鱼类激素的介质中)时，它们是否会选择温度更高、食物含量更高的较浅深度。水蚤和潮蚤4龄幼虫分批培养55 h:水蚤在高食物水平(Scenedesmus obliquus)和1和100个种群密度(Dhg和Dc)下饲养;在不饲喂的情况下，以1和10个L -1的密度饲养潮蝇。55 h后，水蚤2龄幼体被转移到“浮游生物器官”的狭窄垂直管中，新鲜培养基不断流动。培养基中含有种群密度高或低的化学信息;所有培养基的食物和鱼的氯酮水平相同。4龄潮蝇幼虫采用相同的培养基，但培养基中不含食物。而在Dc中没有发现差异，在Dhg中有明显不同的深度选择行为。在高种群密度的化学信息存在的情况下，动物选择的白天深度更大，并且随着实验时间的延长，这种行为变得更加明显。这个差异对于整个数据集来说是非常显著的。接受高密度信息的水蚤与生活在较浅和较暖地层温度较高的对照动物相比，计算出的卵子发育时间延长了17%，计算出的出生率降低了12%。只有小的和不一致的差异发现朝天蛇。
{"title":"Low-density anti-predation refuge in Daphnia and Chaoborus?","authors":"Z. Gliwicz, Piotr Dawidowicz, P. Maszczyk","doi":"10.1127/0003-9136/2006/0167-0101","DOIUrl":"https://doi.org/10.1127/0003-9136/2006/0167-0101","url":null,"abstract":"We used a flow-through experimental system (\"plankton organ\") to test if Daphnia hyalina x galeata (Dhg), D. cucullata (Dc) and Chaoborus flavicans (Ch) take higher risks of predation at low population density levels than at high ones, i. e. to test whether or not they select shallower depths with higher temperatures and higher food levels when they do not receive chemical information on crowding (added to the medium with fish kairomones). Neonates of Daphnia and Chaoborus 4 th instar larvae were first grown for 55 h in batch cultures: Daphnia were reared at high food levels (Scenedesmus obliquus) and at two different population densities of 1 and 100 ind. L -1 (Dhg and Dc); Chaoborus were kept at densities of 1 and 10 ind. L -1 without food. After 55 h, individual Daphnia 2 nd instar juveniles were transferred into the narrow vertical tubes of a \"plankton organ\" with constant flow of fresh medium. The medium contained chemical information on either high or low population density; all media had the same food and fish kairomone levels. The same setup was used for individual Chaoborus 4 th instar larvae, but using media without food. Whereas no difference was found in Dc, different depth selection behavior was apparent in Dhg. The daytime depth selected by the animals was greater in the presence of chemical information on high population density, and this behavior became more pronounced with increasing duration of the experiment. The difference was highly significant for the entire dataset. The calculated duration time of egg development was up to 17% longer and the calculated birth rate 12% reduced for Daphnia receiving high-density information, as compared to control animals enjoying higher temperatures of the shallower and warmer strata. Only minor and inconsistent difference was found for Chaoborus.","PeriodicalId":8118,"journal":{"name":"Archiv Fur Hydrobiologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74119391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-09-01DOI: 10.1127/0003-9136/2006/0167-0421
M. Vanni, J. Andrews, W. Renwick, María González, S. Noble
We investigated the dynamics of nutrient and light limitation of phytoplank- ton in a reservoir ecosystem in relation to storm-mediated variation in stream dis- charge, and how dynamics differed at a shallow site near stream inflows versus one in deep water near the lake outflow. Storm-mediated discharge events reduced the sev- erity of nutrient limitation and increased the severity of light limitation, as predicted by a model of reservoir resource limitation developed by Kimmel et al. (1990). The sev- erity of nutrient limitation was negatively correlated with discharge to the lake; the correlation was strongest with discharge over the preceding 10-14 day period and wea- ker at shorter and longer time scales. However, discharge events also flushed phyto- plankton from the lake and enhanced light limitation, so it is not clear by which mech- anism(s) discharge events mediate phytoplankton resource limitation. Phytoplankton near stream inflows were less nutrient limited than phytoplankton at the lake outflow, consistent with predictions of the Kimmel et al. (1990) model. However, this was true even when streamflow was negligible, suggesting alternative mechanisms for reduced nutrient limitation near stream inflows. In contrast to predictions of the model, phyto- plankton were not more light limited near stream inflows than at the outflow; shallo- wer depth near inflows compensated for higher turbidity, in terms of the light climate experienced by phytoplankton. Our results show that the mechanisms by which dis- charge events mediate phytoplankton resource limitation are complex and require fur- ther study in reservoirs as well as other aquatic systems subject to a high degree of temporal variation in discharge.
我们研究了水库生态系统中植物的营养和光照限制动态与风暴引起的水流变化的关系，以及在靠近水流流入的浅水地点与靠近湖泊流出的深水地点的动态差异。正如Kimmel等人(1990)开发的水库资源限制模型所预测的那样，风暴介导的排放事件降低了养分限制的严重程度，增加了光照限制的严重程度。养分限制的严重程度与入湖量呈负相关;在前10-14天内，其相关性最强，在较短和较长的时间尺度上相关性较弱。然而，排放事件也会使浮游植物从湖中流出，并增强对光的限制，因此，排放事件介导浮游植物资源限制的机制尚不清楚。与Kimmel et al.(1990)模型的预测相一致，河流流入附近的浮游植物比湖泊流出处的浮游植物营养受限更少。然而，即使在水流可以忽略不计的情况下，这也是正确的，这表明了在水流流入附近减少营养限制的其他机制。与模型的预测相反，浮游植物在水流流入处并不比在水流流出处受到更多的光照限制;就浮游植物所经历的轻度气候而言，靠近流入的浅水深度补偿了较高的浊度。我们的研究结果表明，放电事件介导浮游植物资源限制的机制是复杂的，需要在水库和其他受高度时间变化影响的水生系统中进行进一步研究。
{"title":"Nutrient and light limitation of reservoir phytoplankton in relation to storm-mediated pulses in stream discharge","authors":"M. Vanni, J. Andrews, W. Renwick, María González, S. Noble","doi":"10.1127/0003-9136/2006/0167-0421","DOIUrl":"https://doi.org/10.1127/0003-9136/2006/0167-0421","url":null,"abstract":"We investigated the dynamics of nutrient and light limitation of phytoplank- ton in a reservoir ecosystem in relation to storm-mediated variation in stream dis- charge, and how dynamics differed at a shallow site near stream inflows versus one in deep water near the lake outflow. Storm-mediated discharge events reduced the sev- erity of nutrient limitation and increased the severity of light limitation, as predicted by a model of reservoir resource limitation developed by Kimmel et al. (1990). The sev- erity of nutrient limitation was negatively correlated with discharge to the lake; the correlation was strongest with discharge over the preceding 10-14 day period and wea- ker at shorter and longer time scales. However, discharge events also flushed phyto- plankton from the lake and enhanced light limitation, so it is not clear by which mech- anism(s) discharge events mediate phytoplankton resource limitation. Phytoplankton near stream inflows were less nutrient limited than phytoplankton at the lake outflow, consistent with predictions of the Kimmel et al. (1990) model. However, this was true even when streamflow was negligible, suggesting alternative mechanisms for reduced nutrient limitation near stream inflows. In contrast to predictions of the model, phyto- plankton were not more light limited near stream inflows than at the outflow; shallo- wer depth near inflows compensated for higher turbidity, in terms of the light climate experienced by phytoplankton. Our results show that the mechanisms by which dis- charge events mediate phytoplankton resource limitation are complex and require fur- ther study in reservoirs as well as other aquatic systems subject to a high degree of temporal variation in discharge.","PeriodicalId":8118,"journal":{"name":"Archiv Fur Hydrobiologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91166941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-09-01DOI: 10.1127/0003-9136/2006/0167-0169
F. Wende, L. Lucas, A. Graves, M. C. Swift, T. Berendonk
The genetic structure of Chaoborus flavicans was analyzed to start an investigation of the evolutionary status of this Holarctic species and to make inferences about C. flavicans' historical distribution and dispersal. We sequenced a 611 bp fragment of the cytochrome oxidase subunit I and II gene for 26 populations spread across Europe and North America. We found distinct North American and European C. flavicans clades. Chaoborus crystallinus, widely accepted as a sister species of C. flavicans, clustered within the European C. flavicans clade, suggesting potential peripatric speciation. The genetic relationship of the C. flavicans haplotypes within Europe suggests that several glacial refugia existed during the last ice age in southern Europe. European C. flavicans recolonized central and northern Europe from refugia in France and/or Spain after glaciers retreated. This phylogeographic structure was roughly comparable to that of other zooplankton species. The correlation between genetic and geographic distance within Europe was significant, indicating that short distance dispersal in C. flavicans is more common than in other passively dispersing zooplankton species.
{"title":"Steps between lakes? Some initial genetic data on the Holarctic planktonic predator Chaoborus flavicans","authors":"F. Wende, L. Lucas, A. Graves, M. C. Swift, T. Berendonk","doi":"10.1127/0003-9136/2006/0167-0169","DOIUrl":"https://doi.org/10.1127/0003-9136/2006/0167-0169","url":null,"abstract":"The genetic structure of Chaoborus flavicans was analyzed to start an investigation of the evolutionary status of this Holarctic species and to make inferences about C. flavicans' historical distribution and dispersal. We sequenced a 611 bp fragment of the cytochrome oxidase subunit I and II gene for 26 populations spread across Europe and North America. We found distinct North American and European C. flavicans clades. Chaoborus crystallinus, widely accepted as a sister species of C. flavicans, clustered within the European C. flavicans clade, suggesting potential peripatric speciation. The genetic relationship of the C. flavicans haplotypes within Europe suggests that several glacial refugia existed during the last ice age in southern Europe. European C. flavicans recolonized central and northern Europe from refugia in France and/or Spain after glaciers retreated. This phylogeographic structure was roughly comparable to that of other zooplankton species. The correlation between genetic and geographic distance within Europe was significant, indicating that short distance dispersal in C. flavicans is more common than in other passively dispersing zooplankton species.","PeriodicalId":8118,"journal":{"name":"Archiv Fur Hydrobiologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86639255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-09-01DOI: 10.1127/0003-9136/2006/0167-0575
N. Aberle, M. Beutler, C. Moldaenke, K. Wiltshire
Currently it is still extremely difficult to adequately sample populations of microalgae on sediments for large-scale biomass determination. We have now devised a prototype of a new benthic sensor (BenthoFluor) for the quantitative and qualitative assessment of microphytobenthos populations in situ. This sensor enables a high spatial and temporal resolution and a rapid evaluation of the community structure and distribution. These determinations are based on the concept that five spectral excitation ranges can be used to differentiate groups of microalgae, in situ, within a few seconds. In addition, because sediments contain a lot of yellow substances, which can affect the fluorescence and optical differentiation of the algae, the device was equipped with a UV-LED for yellow substances correction. The device was calibrated against HPLC with cultures and tested in the field. Our real-time approach can be used to monitor algal assemblage composition on sediments and is an ideal tool for investigations on the large-scale spatial and temporal variation of algal populations in sediments. Apart from the differentiation of algal populations, the BenthoFluor allows instantaneous monitoring of the chlorophyll concentrations and determination of which algae are responsible for this on the uppermost surface of sediments in the field and in experimental set-ups.
{"title":"\"Spectral fingerprinting\" for specific algal groups on sediments in situ: a new sensor","authors":"N. Aberle, M. Beutler, C. Moldaenke, K. Wiltshire","doi":"10.1127/0003-9136/2006/0167-0575","DOIUrl":"https://doi.org/10.1127/0003-9136/2006/0167-0575","url":null,"abstract":"Currently it is still extremely difficult to adequately sample populations of microalgae on sediments for large-scale biomass determination. We have now devised a prototype of a new benthic sensor (BenthoFluor) for the quantitative and qualitative assessment of microphytobenthos populations in situ. This sensor enables a high spatial and temporal resolution and a rapid evaluation of the community structure and distribution. These determinations are based on the concept that five spectral excitation ranges can be used to differentiate groups of microalgae, in situ, within a few seconds. In addition, because sediments contain a lot of yellow substances, which can affect the fluorescence and optical differentiation of the algae, the device was equipped with a UV-LED for yellow substances correction. The device was calibrated against HPLC with cultures and tested in the field. Our real-time approach can be used to monitor algal assemblage composition on sediments and is an ideal tool for investigations on the large-scale spatial and temporal variation of algal populations in sediments. Apart from the differentiation of algal populations, the BenthoFluor allows instantaneous monitoring of the chlorophyll concentrations and determination of which algae are responsible for this on the uppermost surface of sediments in the field and in experimental set-ups.","PeriodicalId":8118,"journal":{"name":"Archiv Fur Hydrobiologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73193658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-09-01DOI: 10.1127/0003-9136/2006/0167-0403
H. Stibor, Anna Gelzleichter, F. Hantzsche, U. Sommer, M. Striebel, O. Vadstein, Y. Olsen
Measurements of in situ phytoplankton growth and grazing by zooplankton normally involve different techniques. We show that a single dilution experiment based on dialysis bags can be used to do these estimates in situ. Dialysis bags allow an estimate of the in situ phytoplankton gross growth rate whereas the dilution gradient allows a simultaneous estimate of microzooplankton grazing. The comparison of the phytoplankton net growth rate outside dialysis bags and the estimated apparent growth rate of phytoplankton in undiluted samples within dialysis bags allows estimating additional loss processes such as mesozooplankton grazing. The method is especially useful in mesocosms experiments.
{"title":"Combining dialysis and dilution techniques to estimate gross growth rate of phytoplankton and grazing by micro- and mesozooplankton in situ","authors":"H. Stibor, Anna Gelzleichter, F. Hantzsche, U. Sommer, M. Striebel, O. Vadstein, Y. Olsen","doi":"10.1127/0003-9136/2006/0167-0403","DOIUrl":"https://doi.org/10.1127/0003-9136/2006/0167-0403","url":null,"abstract":"Measurements of in situ phytoplankton growth and grazing by zooplankton normally involve different techniques. We show that a single dilution experiment based on dialysis bags can be used to do these estimates in situ. Dialysis bags allow an estimate of the in situ phytoplankton gross growth rate whereas the dilution gradient allows a simultaneous estimate of microzooplankton grazing. The comparison of the phytoplankton net growth rate outside dialysis bags and the estimated apparent growth rate of phytoplankton in undiluted samples within dialysis bags allows estimating additional loss processes such as mesozooplankton grazing. The method is especially useful in mesocosms experiments.","PeriodicalId":8118,"journal":{"name":"Archiv Fur Hydrobiologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87238059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-09-01DOI: 10.1127/0003-9136/2006/0167-0037
J. Pijanowska, Piotr Dawidowicz, A. Howe, L. Weider
Abstract: Patterns of growth and reproduction (first, second and third broods) of aDaphnia magna clone were studied in a life-table experiment with and without chemi-cal signals from fish predators, under three different food regimes (0.2, 0.5 and 2.0mgCl 1 ).At high resource levels, predation played a role as a factor synchronizing repro-ductive events. Somatic growth rates increased with increasing food concentration andwere lower under the presence of fish than in the control treatments. Smaller femalesize in the fish treatments was accompanied by reduced number of eggs released in thesecond and third (but not the first) clutch. The effect of decreased cumulative numberof offspring was counterbalanced by the gain in the second fitness component decreased age in releasing successive broods, which eventually resulted in equivalentintrinsic rates of increase (r) in both, the fish and fish-free environments. Conse-quently, Daphnia life-history performance under the presence of predator cues, with-out accompanying mortality, did not incur fitness costs, across the studied range offood concentrations.Key words: Daphnia magna , phenotypic plasticity, growth rate, predation, reproduc-tive synchrony.
{"title":"Predator-induced shifts in Daphnia life-histories under different food regimes","authors":"J. Pijanowska, Piotr Dawidowicz, A. Howe, L. Weider","doi":"10.1127/0003-9136/2006/0167-0037","DOIUrl":"https://doi.org/10.1127/0003-9136/2006/0167-0037","url":null,"abstract":"Abstract: Patterns of growth and reproduction (first, second and third broods) of aDaphnia magna clone were studied in a life-table experiment with and without chemi-cal signals from fish predators, under three different food regimes (0.2, 0.5 and 2.0mgCl 1 ).At high resource levels, predation played a role as a factor synchronizing repro-ductive events. Somatic growth rates increased with increasing food concentration andwere lower under the presence of fish than in the control treatments. Smaller femalesize in the fish treatments was accompanied by reduced number of eggs released in thesecond and third (but not the first) clutch. The effect of decreased cumulative numberof offspring was counterbalanced by the gain in the second fitness component decreased age in releasing successive broods, which eventually resulted in equivalentintrinsic rates of increase (r) in both, the fish and fish-free environments. Conse-quently, Daphnia life-history performance under the presence of predator cues, with-out accompanying mortality, did not incur fitness costs, across the studied range offood concentrations.Key words: Daphnia magna , phenotypic plasticity, growth rate, predation, reproduc-tive synchrony.","PeriodicalId":8118,"journal":{"name":"Archiv Fur Hydrobiologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84041722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-09-01DOI: 10.1127/0003-9136/2006/0167-0301
B. Santer, N. Sommerwerk, J. Grey
Feeding studies have suggested interspecific differences in the food sources and trophic position of cyclopoid copepod species. We measured δ13C and δ15N of five sympatric cyclopoid copepod species and of bulk POM from a eutrophic lake over a one-year period, to determine if stable isotope derived-data from the field supported the hypotheses from feeding studies. Cyclops abyssorum and C. vicinus differed significantly in δ15N but not in δ13C, inferring assimilation from similar carbon sources but differentiation in their trophic position. Cyclops abyssorum δ15N typically was 1– 2‰ higher than C. vicinus, suggesting a more predatory feeding mode compared to its congener. The summer species Mesocyclops leuckarti, Thermocyclops oithonoides and Diacyclops bicuspidatus exhibited considerable differences in δ13C. The lower δ13C of the hypolimnetic D. bicuspidatus compared to the two epilimnetic species indicates a food niche differentiation by vertical separation. All copepod δ13C and δ15N signatures showed seasonal fluctuations, with low values in winter and high values in summer. The δ13C of seston was generally higher than copepod δ13C. We regard selective feeding from the bulk POM, spatial separation of feeding and assimilation of 13C depleted food sources responsible for this phenomenon.
{"title":"Food niches of cyclopoid copepods in eutrophic Plußsee determined by stable isotope analysis","authors":"B. Santer, N. Sommerwerk, J. Grey","doi":"10.1127/0003-9136/2006/0167-0301","DOIUrl":"https://doi.org/10.1127/0003-9136/2006/0167-0301","url":null,"abstract":"Feeding studies have suggested interspecific differences in the food sources and trophic position of cyclopoid copepod species. We measured δ13C and δ15N of five sympatric cyclopoid copepod species and of bulk POM from a eutrophic lake over a one-year period, to determine if stable isotope derived-data from the field supported the hypotheses from feeding studies. Cyclops abyssorum and C. vicinus differed significantly in δ15N but not in δ13C, inferring assimilation from similar carbon sources but differentiation in their trophic position. Cyclops abyssorum δ15N typically was 1– 2‰ higher than C. vicinus, suggesting a more predatory feeding mode compared to its congener. The summer species Mesocyclops leuckarti, Thermocyclops oithonoides and Diacyclops bicuspidatus exhibited considerable differences in δ13C. The lower δ13C of the hypolimnetic D. bicuspidatus compared to the two epilimnetic species indicates a food niche differentiation by vertical separation. All copepod δ13C and δ15N signatures showed seasonal fluctuations, with low values in winter and high values in summer. The δ13C of seston was generally higher than copepod δ13C. We regard selective feeding from the bulk POM, spatial separation of feeding and assimilation of 13C depleted food sources responsible for this phenomenon.","PeriodicalId":8118,"journal":{"name":"Archiv Fur Hydrobiologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86779591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2006-09-01DOI: 10.1127/0003-9136/2006/0167-0351
M. Sala, H. Güde
In order to obtain a first insight into the characteristics of pelagic, littoral and profundal bacterial communities and their potential role for the degradation of organic matter in the deep prealpine Lake Constance, we compared the seasonal dynamics of bacterial abundances and activities during the annual cycle in the epilim- netic water of a central station as well as in surface layers of sediments at a central pro- fundal and a littoral site. For this purpose, bacterial abundances (DAPI counts), rates of leucine incorporation, respiration of 14 C-labeled substrates (glucose, phenol) and ectoenzymatic activities were measured biweekly-monthly at the different sampling sites. Bacterial densities in lake sediments generally exceeded those of epilimnetic waters by at least two orders of magnitude with higher values in profundal sediments. A seasonal pattern was well expressed for bacterioplankton, less pronounced for ben- thic littoral bacteria and hardly visible for profundal bacteria. Compared to pelagic bacteria, benthic bacteria exhibited lower specific rates of leucine incorporation, espe- cially during the warmer periods. For profundal benthic communities specific rates of glucose respiration and of enzyme activities were permanently low with little seasonal fluctuation. In contrast, littoral benthic communities showed the highest values for these specific metabolic activities among the three sites tested. Additionally, the capac- ity of metabolism of phenol (used here as a representative of more recalcitrant aro- matic substances) was by far highest respired for littoral communities, and almost lacking for pelagic communities. Evidence from the literature suggests that the qualita- tively and quantitatively enhanced level of degradation capacities observed for littoral bacteriobenthos may be predominantly a result of the combined effect of increased supply of additional organic matter (e. g. allochthonous matter and macrophytes), an enriched bacterial gene reservoir in sediments, and frequent resuspension. Littoral ben- thic communities showed the highest specific metabolic activities exceeding those of bacterioplankton and profundal bacteriobenthos by an order of magnitude. As a whole,
{"title":"Seasonal dynamics of pelagic and benthic (littoral and profundal) bacterial abundances and activities in a deep prealpine lake (L. Constance)","authors":"M. Sala, H. Güde","doi":"10.1127/0003-9136/2006/0167-0351","DOIUrl":"https://doi.org/10.1127/0003-9136/2006/0167-0351","url":null,"abstract":"In order to obtain a first insight into the characteristics of pelagic, littoral and profundal bacterial communities and their potential role for the degradation of organic matter in the deep prealpine Lake Constance, we compared the seasonal dynamics of bacterial abundances and activities during the annual cycle in the epilim- netic water of a central station as well as in surface layers of sediments at a central pro- fundal and a littoral site. For this purpose, bacterial abundances (DAPI counts), rates of leucine incorporation, respiration of 14 C-labeled substrates (glucose, phenol) and ectoenzymatic activities were measured biweekly-monthly at the different sampling sites. Bacterial densities in lake sediments generally exceeded those of epilimnetic waters by at least two orders of magnitude with higher values in profundal sediments. A seasonal pattern was well expressed for bacterioplankton, less pronounced for ben- thic littoral bacteria and hardly visible for profundal bacteria. Compared to pelagic bacteria, benthic bacteria exhibited lower specific rates of leucine incorporation, espe- cially during the warmer periods. For profundal benthic communities specific rates of glucose respiration and of enzyme activities were permanently low with little seasonal fluctuation. In contrast, littoral benthic communities showed the highest values for these specific metabolic activities among the three sites tested. Additionally, the capac- ity of metabolism of phenol (used here as a representative of more recalcitrant aro- matic substances) was by far highest respired for littoral communities, and almost lacking for pelagic communities. Evidence from the literature suggests that the qualita- tively and quantitatively enhanced level of degradation capacities observed for littoral bacteriobenthos may be predominantly a result of the combined effect of increased supply of additional organic matter (e. g. allochthonous matter and macrophytes), an enriched bacterial gene reservoir in sediments, and frequent resuspension. Littoral ben- thic communities showed the highest specific metabolic activities exceeding those of bacterioplankton and profundal bacteriobenthos by an order of magnitude. As a whole,","PeriodicalId":8118,"journal":{"name":"Archiv Fur Hydrobiologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2006-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86876969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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