TY - JOUR A1 - Weithoff, Guntram A1 - Neumann, Catherin A1 - Seiferth, Jacqueline A1 - Weisse, Thomas T1 - Living on the edge: reproduction, dispersal potential, maternal effects and local adaptation in aquatic, extremophilic invertebrates JF - Aquatic sciences : research across boundaries N2 - Isolated extreme habitats are ideally suited to investigate pivotal ecological processes such as niche use, local adaptation and dispersal. Extremophilic animals living in isolated habitats face the problem that dispersal is limited through the absence of suitable dispersal corridors, which in turn facilitates local adaptation. We used five rotifer isolates from extremely acidic mining lakes with a pH of below 3 as model organisms to test whether these isolates are acidotolerant or acidophilic, whether they survive and reproduce at their niche edges (here pH 2 and circum-neutral pH) and whether local adaptation has evolved. To evaluate potential dispersal limitation, we tested whether animals and their parthenogenetic eggs survive and remain reproductive or viable at unfavourable pH-conditions. All five isolates were acidophilic with a pH-optimum in the range of 4-6, which is well above the pH (< 3) of their lakes of origin. At unfavourable high pH, in four out of the five isolates parthenogenetic females produced a high number of non-viable eggs. Females and eggs produced at favourable pH (4) remained vital at an otherwise unfavourable pH of 7, indicating that for dispersal no acidic dispersal corridors are necessary. Common garden experiments revealed no clear evidence for local adaptation in any of the five isolates. Despite their acidophilic nature, all five isolates can potentially disperse via circum-neutral water bodies as long as their residence time is short, suggesting a broader dispersal niche than their realized niche. Local adaptation might have been hampered by the low population sizes of the rotifers in their isolated habitat and the short time span the mining lakes have existed. KW - Common garden experiments KW - Extreme habitats KW - Extremophiles KW - Rotifers KW - Zooplankton Y1 - 2019 U6 - https://doi.org/10.1007/s00027-019-0638-z SN - 1015-1621 SN - 1420-9055 VL - 81 IS - 3 PB - Springer CY - Basel ER - TY - JOUR A1 - Sperfeld, Erik A1 - Wacker, Alexander T1 - Maternal diet of Daphnia magna affects offspring growth responses to supplementation with particular polyunsaturated fatty acids JF - Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica N2 - Previous studies examining the effects of food quality on zooplankton often controlled for maternal effects of resource provisioning using standardized maternal diets. However, varying nutritional history of mothers may change resource provisioning to their progeny, especially regarding polyunsaturated fatty acids (PUFAs), which may change the interpretation of previously observed fitness responses of offspring. To assess PUFA-mediated maternal provisioning effects on offspring, we raised females of the cladoceran Daphnia magna on diets differing considerably in PUFA composition and raised their offspring on a PUFA-lacking diet supplemented with the omega 3 PUFAs alpha-linolenic acid (ALA) and/or eicosapentaenoic acid (EPA). The mass-specific growth responses of offspring to their own diets were affected by the maternal diet regime, probably due to varying maternal PUFA provisioning. A low maternal provisioning of EPA or ALA was sufficient to prevent growth limitation of offspring by these PUFAs until reaching maturity. A comparison with results of published ALA and EPA supplementation experiments suggests that the previously observed limitation effects depended on the usage of a single algae genus as maternal diet. Therefore, we suggest that maternal diets should be deliberately varied in future studies assessing ecological relevant food quality effects on zooplankton, especially regarding PUFAs. KW - Food quality KW - Maternal effects KW - Nutritional ecology KW - Resource provisioning KW - Zooplankton Y1 - 2015 U6 - https://doi.org/10.1007/s10750-015-2244-y SN - 0018-8158 SN - 1573-5117 VL - 755 IS - 1 SP - 267 EP - 282 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Quintana, Xavier D. A1 - Arim, Matias A1 - Badosa, Anna A1 - Maria Blanco, Jose A1 - Boix, Dani A1 - Brucet, Sandra A1 - Compte, Jordi A1 - Egozcue, Juan J. A1 - de Eyto, Elvira A1 - Gaedke, Ursula A1 - Gascon, Stephanie A1 - Gil de Sola, Luis A1 - Irvine, Kenneth A1 - Jeppesen, Erik A1 - Lauridsen, Torben L. A1 - Lopez-Flores, Rocio A1 - Mehner, Thomas A1 - Romo, Susana A1 - Sondergaard, Martin T1 - Predation and competition effects on the size diversity of aquatic communities JF - Aquatic sciences : research across boundaries N2 - Body size has been widely recognised as a key factor determining community structure in ecosystems. We analysed size diversity patterns of phytoplankton, zooplankton and fish assemblages in 13 data sets from freshwater and marine sites with the aim to assess whether there is a general trend in the effect of predation and resource competition on body size distribution across a wide range of aquatic ecosystems. We used size diversity as a measure of the shape of size distribution. Size diversity was computed based on the Shannon-Wiener diversity expression, adapted to a continuous variable, i.e. as body size. Our results show that greater predation pressure was associated with reduced size diversity of prey at all trophic levels. In contrast, competition effects depended on the trophic level considered. At upper trophic levels (zooplankton and fish), size distributions were more diverse when potential resource availability was low, suggesting that competitive interactions for resources promote diversification of aquatic communities by size. This pattern was not found for phytoplankton size distributions where size diversity mostly increased with low zooplankton grazing and increasing nutrient availability. Relationships we found were weak, indicating that predation and competition are not the only determinants of size distribution. Our results suggest that predation pressure leads to accumulation of organisms in the less predated sizes, while resource competition tends to favour a wider size distribution. KW - Phytoplankton KW - Zooplankton KW - Fish KW - Size distribution KW - Predation KW - Competition KW - Compositional data analysis Y1 - 2015 U6 - https://doi.org/10.1007/s00027-014-0368-1 SN - 1015-1621 SN - 1420-9055 VL - 77 IS - 1 SP - 45 EP - 57 PB - Springer CY - Basel ER - TY - JOUR A1 - Lukas, Marcus A1 - Wacker, Alexander T1 - Daphnia's dilemma: adjustment of carbon budgets in the face of food and cholesterol limitation JF - The journal of experimental biology N2 - We studied the carbon (C) metabolism in Daphnia when the amount of C (food quantity) and/or the content of biochemical nutrients (food quality) was limiting. Growth performances and C budgets of Daphnia magna (assimilation, faeces egestion, excretion and respiration measured by [C-14]-tracing) were analysed when animals were raised on different food quantities and concentrations of cholesterol, an essential biochemical food compound. Cholesterol is of special interest because it not only acts as limiting nutrient but also contributes to the overall C pool of the animals. As the tissue cholesterol concentration in Daphnia is quite low, we hypothesized the selective exclusion of cholesterol from C budgeting and tested this using radiolabelled cholesterol. Somatic growth rates of D. magna were highest at high quantity and quality and were reduced to a moderate value if either the food quantity or the cholesterol concentration was low. Growth was lowest at low food quantity and quality. The measurements of C budgets revealed high regulative response to low food quality at high food quantity only. Here, low dietary cholesterol caused bulk C assimilation efficiency (AE) to decrease and assimilated (excess) C to be increasingly respired. Additionally, Daphnia enhanced efficient adjustment of C budgets when facing cholesterol limitation by (1) increasing the AE of the cholesterol itself and (2) not changing cholesterol respiration, which was still not detectable. In contrast, at low food quantity, Daphnia is unable to adjust for low food quality, emphasizing that food limitation could overrule food quality effects. KW - Biochemical limitation KW - Carbon budgets KW - Zooplankton KW - Carbon pathway KW - Food quality KW - Food quantity Y1 - 2014 U6 - https://doi.org/10.1242/jeb.094151 SN - 0022-0949 SN - 1477-9145 VL - 217 IS - 7 SP - 1079 EP - 1086 PB - Company of Biologists Limited CY - Cambridge ER - TY - JOUR A1 - Bickel, Samantha L. A1 - Tang, Kam W. A1 - Grossart, Hans-Peter T1 - Structure and function of zooplankton-associated bacterial communities in a temperate estuary change more with time than with zooplankton species JF - Aquatic microbial ecology : international journal N2 - Zooplankton support distinct bacterial communities in high concentrations relative to the surrounding water, but little is known about how the compositions and functionalities of these bacterial communities change through time in relation to environmental conditions. We conducted a year-long field study of bacterial communities associated with common zooplankton groups as well as free-living bacterial communities in the York River, a tributary of Chesapeake Bay. Bacterial community genetic fingerprints and their carbon substrate usage were examined by denaturing gradient gel electrophoresis (DGGE) of amplified 16S rDNA and by Biolog EcoPlates, respectively. Zooplankton-associated communities were genetically distinct from free-living bacterial communities but utilized a similar array of carbon substrates. On average, bacteria associated with different zooplankton groups were genetically more similar to each other within each month (65.4% similarity) than to bacterial communities of the same zooplankton group from different months (28 to 30% similarity), which suggests the importance of ambient environmental conditions in shaping resident zooplankton-associated bacterial communities. Monthly changes in carbon substrate utilization were less variable for zooplankton-associated bacteria than for free-living bacteria, suggesting that the zooplankton microhabitat is more stable than the surrounding water and supports specific bacterial groups in the otherwise unfavorable conditions in the water column. KW - Zooplankton KW - Bacterial communities KW - Carbon substrates KW - Biolog EcoPlates KW - York River Y1 - 2014 U6 - https://doi.org/10.3354/ame01676 SN - 0948-3055 SN - 1616-1564 VL - 72 IS - 1 SP - 1 EP - 15 PB - Institute of Mathematical Statistics CY - Oldendorf Luhe ER -