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Publisher: Springer-Verlag   (Total: 2341 journals)

 Aquatic Ecology   [SJR: 0.646]   [H-I: 44]   [30 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1573-5125 - ISSN (Online) 1386-2588    Published by Springer-Verlag  [2341 journals]
• Rare but large bivalves alter benthic respiration and nutrient recycling
in riverine sediments
• Authors: Sara Benelli; Marco Bartoli; Erica Racchetti; Paula Carpintero Moraes; Mindaugas Zilius; Irma Lubiene; Elisa Anna Fano
Pages: 1 - 16
Abstract: Abstract Bioturbation studies have generally analyzed small and abundant organisms while the contribution to the benthic metabolism by rare, large macrofauna has received little attention. We hypothesize that large, sporadic bivalves may represent a hot spot for benthic processes due to a combination of direct and indirect effects as their metabolic and bioturbation activities. Intact riverine sediments with and without individuals of the bivalve Sinanodonta woodiana were collected in a reach with transparent water, where the occurrence of the mollusk was clearly visible. The bivalve metabolism and its effects on sedimentary fluxes of dissolved gas and nutrients were measured via laboratory incubations of intact cores under controlled conditions. S. woodiana contributed significantly to O2 and TCO2 benthic fluxes through its respiration and to $${\text{NH}}_{4}^{ + }$$ , SRP and SiO2 regeneration via its excretion. The bivalve significantly stimulated also microbial denitrification and determined a large efflux of CH4, likely due a combination of bioturbation and biodeposition activities or to anaerobic metabolism within the mollusk gut. This study demonstrates that a few, large individuals of this bivalve produce significant effects on aerobic and anaerobic benthic metabolism and nutrient mobilization. Random sediment sampling in turbid waters seldom catches these important effects due to low densities of large fauna.
PubDate: 2017-03-01
DOI: 10.1007/s10452-016-9590-3
Issue No: Vol. 51, No. 1 (2017)

• Distribution and microhabitat associations of the juveniles of a
high-value sea cucumber, Stichopus cf. horrens, in northern Philippines
• Authors: N. Palomar-Abesamis; R. A. Abesamis; M. A. Juinio-Meñez
Pages: 17 - 31
Abstract: Abstract There is considerable global interest in rebuilding depleted populations of sea cucumbers (Echinodermata, Holothuroidea) to address conservation and economic goals. For the vast majority of holothurian species, the habitat and food requirements of the juvenile stage are poorly understood. We investigated the distribution and microhabitat associations of juveniles of a commercially important sea cucumber, Stichopus cf. horrens, in the shallow, shoreward side of a coral reef (or backreef) in northern Philippines (16°21′38.7″N, 119°59′47.9″E). Relationships between juvenile density and the physical, chemical and biological characteristics of their habitat were examined. Potential food sources of the juveniles were also investigated using elemental and stable isotope analysis. Results showed that juveniles are more abundant in seagrass areas and the transition zone between seagrass and the rubble-dominated reef flat. A non-metric multidimensional scaling (MDS) plot indicated that juvenile density was most positively associated with coarser sand and rubble (>0.5 mm) and seagrass (Thalassia hemprichii) abundance (2D stress = 0.11). Juvenile density was also positively associated with sediment organic matter from plant detritus to a lesser extent. Elemental and isotope analysis of one site indicated that epiphytes were the primary food source of juveniles, while sediment detritus from microalgae and seagrass was a secondary food source. This study corroborates anecdotal evidence regarding the importance of seagrass to S. cf. horrens as potential refugia and source of high-quality food for its juveniles. These findings underscore the need to protect the nursery habitats of wild juveniles and provide critical information for the selection of suitable natural habitats for releasing cultured juveniles of this important species.
PubDate: 2017-03-01
DOI: 10.1007/s10452-016-9591-2
Issue No: Vol. 51, No. 1 (2017)

• Effects of temperature and food quality on isotopic turnover and
• Authors: Hélène Masclaux; Nicole B. Richoux
Pages: 33 - 44
Abstract: Abstract Our experimental study was designed to assess the effects of temperature on nitrogen isotope turnover and to measure the effects of temperature and food quality on the stable carbon and nitrogen isotope discrimination factors (Δ13C and Δ15N) in a cladoceran. For the first part of our study, Daphnia were fed with non-enriched or 15N-enriched Scenedesmus obliquus at 12, 15, 20, and 25 °C. For the second part, Daphnia were reared at 15, 20, and 25 °C on Scenedesmus or Cryptomonas sp. There were no clear effects of temperature on turnover rates of the nitrogen isotope of cladocerans. However, a general increase in Δ13C with increasing temperature was measured, regardless of the food source. Δ15N was also affected by temperature, but contrasting results were measured depending on the food source used. There were significant effects of food quality on Δ13C and Δ15N in Daphnia, as values obtained for Daphnia fed Scenedesmus were always higher than those obtained for Daphnia fed Cryptomonas. Our experiments produced discrimination factors that were very different from those usually considered in isotope studies and showed that the values used for isotope model implementation to analyze field data need to be adapted to environmental conditions.
PubDate: 2017-03-01
DOI: 10.1007/s10452-016-9592-1
Issue No: Vol. 51, No. 1 (2017)

• Metacommunity dynamics of amphibians in years with differing rainfall
• Authors: Attila L. Péntek; Csaba F. Vad; Katalin Zsuga; Zsófia Horváth
Pages: 45 - 57
Abstract: Abstract Many studies investigated the habitat preference and behaviour ecology of individual amphibian species while we know less about how their community assembly reflects changes in environmental factors, including the role of climatic extremes. Community-level studies also allow us to apply trait-based analyses that are crucial for a better understanding of the functioning of amphibian communities and metacommunities. In two years with contrasting rainfall (2012 and 2013), we found amphibian species in 85 different waterbodies of a heterogeneous landscape in Central Europe (Hungary). Within the metacommunity framework, the contributions of local, landscape and spatial variables to community assembly were assessed. We also measured the local extinction–colonisation rates in the ponds for all species between the two years. To investigate the role of dispersal traits in explaining the spatial distribution of species, we studied the relationship between body size and the pure spatial fraction of variation. According to our results, the main drivers were the same in both the dry and wet year, but their relative contribution changed. Local variables played a predominant role in the assembly of the amphibian metacommunity. Spatial signals were more evident in the dry year. This implies not only the adverse effect of decreased connectivity due to the drying out of several habitats but also a loss of breeding sites for the studied amphibians. Local colonisation rates were higher in primarily terrestrial species (Hyla arborea, Pelobates fuscus, Bufo bufo) which only visit ponds during breeding. We found a negative relationship between the pure spatial effect and body size, suggesting an increased level of dispersal limitation in small-bodied species. Our results showed that while the strength and relative role of local and spatial processes changed between years, the role of dispersal traits in explaining the spatial distribution of species was similar. Specialisation to different habitats seems to be a major process in determining vertebrate metacommunities in landscapes. Dispersal traits of different species should be taken more into consideration in the practical conservation of amphibian habitats.
PubDate: 2017-03-01
DOI: 10.1007/s10452-016-9597-9
Issue No: Vol. 51, No. 1 (2017)

• Elevated carbon dioxide has the potential to impact alarm cue responses in
some freshwater fishes
• Authors: John A. Tix; Caleb T. Hasler; Cody Sullivan; Jennifer D. Jeffrey; Cory D. Suski
Pages: 59 - 72
Abstract: Abstract Freshwater fish behaviors have the potential to be impacted by acidification due to increases in dissolved carbon dioxide (CO2). Recent work in the marine environment suggests that increased CO2 levels due to climate change can negatively affect fishes homing to natal environments, while also hindering their ability to detect predators and perform aerobically. The potential for elevated CO2 to have similar negative impacts on freshwater communities remains understudied. The objective of our study was to quantify the effects of elevated CO2 on the behaviors of fathead minnows (Pimephales promelas) and silver carp (Hypophthalmichthys molitrix) following exposure to conspecific skin extracts (alarm cues). In fathead minnows, their response to conspecific skin extracts was significantly impaired following exposure to elevated CO2 levels for at least 96 h, while silver carp behaviors were unaltered. However, fathead minnow behaviors did return to pre-CO2 exposure in high-CO2-exposed fish following 14 days of holding at ambient CO2 levels. Overall, this study suggests there may be potential impacts to freshwater fishes alarm cue behaviors following CO2 exposure, but these responses may be species-specific and will likely be abated should the CO2 stressor be removed.
PubDate: 2017-03-01
DOI: 10.1007/s10452-016-9598-8
Issue No: Vol. 51, No. 1 (2017)

• Groundwater biodiversity in a chemoautotrophic cave ecosystem: how
geochemistry regulates microcrustacean community structure
• Authors: Diana M. P. Galassi; Barbara Fiasca; Tiziana Di Lorenzo; Alessandro Montanari; Silvano Porfirio; Simone Fattorini
Pages: 75 - 90
Abstract: Abstract The Frasassi cave system in central Italy hosts one of the few known examples of a groundwater metazoan community that is supported by sulfur-based lithoautotrophic microbes. Despite the challenging conditions represented by high concentrations of H2S and low concentrations of O2, this cave system is home to many invertebrate species. Here, we analyzed the copepods inhabiting sulfidic lakes and non-sulfidic dripping pools in order to investigate how environmental conditions in sulfidic waters regulate the spatial distribution of the cave microcrustacean community over time. We also sampled copepod assemblages of sulfidic lakes under conditions of both high and low H2S concentration. Cluster analysis and canonical correspondence analysis separated the copepod assemblages inhabiting dripping pools from those of sulfidic lakes. H2S concentration, pH and O2 concentration were identified as the main factors regulating community structure. These results indicate that the distribution of groundwater copepods within the cave system is ecologically and spatially structured. Sulfidic lakes showed lower Simpson dominance, higher Shannon diversity and higher Pielou equitability at higher H2S concentrations. The complex community structure of the copepods of the Frasassi cave system suggests that a chemosynthetically produced food source facilitated the colonization of stygobionts in sulfidic groundwater due to their tolerance to the environmental conditions.
PubDate: 2017-03-01
DOI: 10.1007/s10452-016-9599-7
Issue No: Vol. 51, No. 1 (2017)

• Short-term interactive effects of ultraviolet radiation, carbon dioxide
and nutrient enrichment on phytoplankton in a shallow coastal lagoon
• Authors: Rita B. Domingues; Cátia C. Guerra; Helena M. Galvão; Vanda Brotas; Ana B. Barbosa
Pages: 91 - 105
Abstract: Abstract The main goal of this study was to evaluate short-term interactions between increased CO2, UVR and inorganic macronutrients (N, P and Si) on summer phytoplankton assemblages in the Ria Formosa coastal lagoon (SW Iberia), subjected to intense anthropogenic pressures and highly vulnerable to climate change. A multifactorial experiment using 20 different nutrient-enriched microcosms exposed to different spectral and CO2 conditions was designed. Before and after a 24-h in situ incubation, phytoplankton abundance and composition were analysed. Impacts and interactive effects of high CO2, UVR and nutrients varied among different functional groups. Increased UVR had negative effects on diatoms and cyanobacteria and positive effects on cryptophytes, whereas increased CO2 inhibited cyanobacteria but increased cryptophyte growth. A positive synergistic interaction between CO2 and UVR was observed for diatoms; high CO2 counteracted the negative effects of UVR under ambient nutrient concentrations. Nutrient enrichments suppressed the negative effects of high CO2 and UVR on cyanobacteria and diatoms, respectively. Beneficial effects of CO2 were observed for diatoms and cryptophytes under combined additions of nitrate and ammonium, suggesting that growth may be limited by DIC availability when the primary limitation by nitrogen is alleviated. Beneficial effects of high CO2 and UVR in diatoms were also induced or intensified by ammonium additions.
PubDate: 2017-03-01
DOI: 10.1007/s10452-016-9601-4
Issue No: Vol. 51, No. 1 (2017)

• The ecological adaptability of Phragmites australis to interactive effects
of water level and salt stress in the Yellow River Delta
• Authors: Bo Guan; Junbao Yu; Aixin Hou; Guangxuan Han; Guangmei Wang; Fanzhu Qu; Jiangbao Xia; Xuehong Wang
Pages: 107 - 116
Abstract: Abstract Soil salinity and waterlogging are two major environmental problems in estuarine wetlands. To prevent the typical wetland plants from degradation by soil salinization and salt waterlogging and more effectively use the plants to provide wetland ecosystem services, we examined the ecological adaptability of Phragmites australis, a characteristic plant species in the Yellow River Delta, to the interactive effects of water level and salt stress. The results showed that P. australis adapts to salt and water table stressed environments through slowing down the growth rate, maintaining the tiller number, and adjusting the biomass allocation of different organs. The highest plant height and the largest leaf area were at 0 cm water table treatment; the 0.5 % NaCl treatment increased the aboveground biomass; higher water table increased the fibrous root biomass allocation, but largely decreased the leaf biomass. The exclusion of toxic inorganic ions such as Na+ and Cl− and the accumulation of organic solutes are also important mechanisms to aid survival in saline wetlands. On average 35.1 % of Cl− and 53.9 % of Na+ accumulated in belowground organs. The study could provide fundamental guidance for wetland restoration projects and wetland sustainable use in coastal zones such as the Yellow River Delta.
PubDate: 2017-03-01
DOI: 10.1007/s10452-016-9602-3
Issue No: Vol. 51, No. 1 (2017)

• Competition between a toxic and a non-toxic Microcystis strain under
constant and pulsed nitrogen and phosphorus supply
• Authors: Saara Suominen; Verena S. Brauer; Anne Rantala-Ylinen; Kaarina Sivonen; Teppo Hiltunen
Pages: 117 - 130
Abstract: Abstract The toxicity of a harmful algal bloom is strongly determined by the relative abundance of non-toxic and toxic genotypes and might therefore be regulated by competition for growth-limiting resources. Here, we studied how the toxic Microcystis aeruginosa strain PCC 7806 and a non-toxic mutant compete for nitrogen and phosphorus under constant and pulsed nutrient supply. Our monoculture and competition experiments show that these closely related genotypes have distinct nutrient physiologies and that they differ in their ability to compete for nitrogen and phosphorus. The toxic wild type won the competition under nitrogen limitation, while the non-toxic mutant dominated under phosphorus limitation. Pulses of both nitrogen and phosphorus increased the dominance of the toxic genotype, which lead to an even faster competitive exclusion of the non-toxic genotype under nitrogen pulses and to coexistence of both genotypes under phosphorus pulses. Our findings indicate that the genotype level dynamics driven by resource competition can be an important factor in determining cyanobacterial bloom toxicity.
PubDate: 2017-03-01
DOI: 10.1007/s10452-016-9603-2
Issue No: Vol. 51, No. 1 (2017)

• Response variable selection in principal response curves using permutation
testing
• Authors: Nadia J. Vendrig; Lia Hemerik; Cajo J. F. ter Braak
Pages: 131 - 143
Abstract: Abstract Principal response curves analysis (PRC) is widely applied to experimental multivariate longitudinal data for the study of time-dependent treatment effects on the multiple outcomes or response variables (RVs). Often, not all of the RVs included in such a study are affected by the treatment and RV-selection can be used to identify those RVs and so give a better estimate of the principal response. We propose four backward selection approaches, based on permutation testing, that differ in whether coefficient size is used or not in ranking the RVs. These methods are expected to give a more robust result than the use of a straightforward cut-off value for coefficient size. Performance of all methods is demonstrated in a simulation study using realistic data. The permutation testing approach that uses information on coefficient size of RVs speeds up the algorithm without affecting its performance. This most successful permutation testing approach removes roughly 95 % of the RVs that are unaffected by the treatment irrespective of the characteristics of the data set and, in the simulations, correctly identifies up to 97 % of RVs affected by the treatment.
PubDate: 2017-03-01
DOI: 10.1007/s10452-016-9604-1
Issue No: Vol. 51, No. 1 (2017)

• Life history traits determine the differential vulnerability of native and

• Authors: Andrew T. Davidson; Nathan J. Dorn
Abstract: Abstract The vulnerability of gastropods to their predators varies with life history traits such as morphology, body size, behavior, and growth rates as well as predator size. A recent study suggested that the invasive apple snail, Pomacea maculata, was considerably more vulnerable to crayfish predators than the native Florida apple snail, P. paludosa. The difference was hypothesized to be caused by the relatively small hatchling size of P. maculata. To test this hypothesis, we conducted a series of feeding assays designed to quantify maximum feeding rates and selective foraging of crayfish on apple snails. The rate at which crayfish killed individual P. maculata (i.e., kill rates) decreased with snail size, and kill rates on both species increased with crayfish size. Kill rates on juvenile P. maculata were higher than kill rates on size-matched hatchling P. paludosa, and crayfish fed selectively on P. maculata when offered mixed groups of size-matched snails. Further analyses revealed that hatchling P. paludosa possess shells 1.8× heavier than size-matched P. maculata suggesting differences in vulnerability to crayfish were consistent with interspecific differences in shell defenses. Differences in hatchling size and defensive traits in combination make crayfish kill rates on hatchling P. maculata approximately 15.4× faster than on hatchling P. paludosa, but the relative contribution of hatchling size to differences in apple snail vulnerability was >3× greater than the contribution of defensive traits.
PubDate: 2017-04-11
DOI: 10.1007/s10452-017-9620-9

• Acclimation of Salix triandroides cuttings to incomplete submergence is
reduced by low light
• Authors: Xiaohui Ding; Jianfeng Zou; Youzhi Li; Xin Yao; Dongsheng Zou; Canming Zhang; Nan Yang; Yandong Niu; Hualin Bian; Jiajun Deng; Zixuan Ge
Abstract: Abstract A simulated flooding experiment was conducted to evaluate the effects of seasonal flooding on the plant Salix triandroides from the Dongting Lake wetlands in China. The morphology, photosynthetic activity, and anatomy of cuttings in three water conditions (−40 cm, water level 40 cm below soil surface; 0 cm, water level 0 cm at the soil surface; and 40 cm, water level 40 cm above soil surface) and two lights conditions (full sunlight and 10% sunlight) were measured. Plants had a higher survival ratio and biomass accumulation in full sunlight than in 10% sunlight when the water level was −40 and 0 cm, but there was no difference between these parameters in cuttings grown under the two light conditions in the 40 cm water treatment. In full sunlight, a lower survival ratio and reduced biomass were observed with increasing water level. The same trend was also seen for survival ratio in 10% sunlight. However, there was no difference in biomass among the three water levels in 10% sunlight, except for leaf weight. Branch height, leaf number, adventitious root length, and adventitious root number were different in the three water levels and two light conditions. In water levels of −40 and 0 cm, plants had lower chlorophyll contents in full sunlight than in 10% sunlight. In full sunlight, there was no difference in chlorophyll content between the water levels, while in 10% sunlight, lower chlorophyll content was observed in −40 cm than in 0 cm water. Photosynthetic rate, stomatal conductance, and transpiration rate decreased, but water-use efficiency increased in reduced light at all three water levels. Additionally, plants had higher porosity in 40 cm water than in −40 and 0 cm conditions. Based on the reduced plant growth in the 10% sunlight condition and decreased survival in the 40 cm water level, we conclude that low light significantly decreased plant acclimation to incomplete submergence and that high water levels induced dormancy in the cuttings. Therefore, the height of cuttings used for forestation or reforestation is an important consideration for mitigating the negative effects of seasonal flooding on the survival and growth of S. triandroides in Dongting Lake wetlands.
PubDate: 2017-04-05
DOI: 10.1007/s10452-017-9619-2

• The role of environmental factors in the induction of oxidative stress in
zebra mussel ( Dreissena polymorpha )
• Authors: Adrianna Wojtal-Frankiewicz; Joanna Bernasińska; Piotr Frankiewicz; Krzysztof Gwoździński; Tomasz Jurczak
Abstract: Abstract The aim of this study was to investigate the influence of specific environmental factors, such as temperature, pH, oxygen concentration, and phosphate, nitrate, chloride, sodium, potassium, sulphate, magnesium and calcium ions concentration, as well as microcystins, on the seasonal variations in the activity of the antioxidant system of the zebra mussel. We examined changes in lipid peroxidation (LPO) levels, glutathione content and the catalase activity of mussels inhabiting the two ecosystems, which differ due to their trophic structure and the presence of toxic cyanobacteria. The results show a relationship between the activity of the antioxidant system of zebra mussels and the seasonal fluctuations of environmental parameters: the symptoms of oxidative stress were generally the highest during spring and the lowest during summer in both ecosystems. Our study also revealed that regardless of the study area the most important factors determining the activity of the antioxidant defences of mussels were the mineral composition (particularly magnesium and calcium ions concentrations) and physical parameters of the water (oxygen concentration and pH). However, factors resulting from the trophic status of studied ecosystems, such as limitations in food resources or high concentration of microcystins during cyanobacterial blooms, were periodically responsible for increased level of LPO in the tissues of zebra mussel. These findings may indicate a limited tolerance of the zebra mussel to the local environmental conditions.
PubDate: 2017-03-29
DOI: 10.1007/s10452-017-9617-4

• Rising variance and abrupt shifts of subfossil chironomids due to
eutrophication in a deep sub-alpine lake
• Authors: Simon Belle; Virgile Baudrot; Andrea Lami; Simona Musazzi; Vasilis Dakos
Abstract: Abstract In response to anthropogenic eutrophication and global warming, deep-water oxygen depletion is expected to have large effects on freshwater lake biogeochemistry and resident communities. In particular, it has been observed that deep-water hypoxia may potentially lead to regime shifts of lake benthic communities. We explored such community shifts by reconstructing a high-resolution subfossil chironomid record from a sediment core collected in the sub-alpine lake Remoray in France. We identified an abrupt shift in chironomid composition triggered by the collapse of the dominant Sergentia coracina-type chironomids around 1980. We found that the collapse of Sergentia coracina type was coupled to a gradual increase in organic matter content in lake sediments caused by eutrophication. We concluded that the most probable cause for the collapse of Sergentia coracina type was a change in oxygen concentrations below the minimal threshold for larval growth. We also analyzed trends in variance and autocorrelation of chironomid dynamics to test whether they can be used as early warnings of the Sergentia collapse. We found that variance rose prior to the collapse, but it was marginally significant (Kendal rank correlation 0.71, p = 0.05), whereas autocorrelation increased but insignificantly and less strongly (Kendal rank correlation 0.23, p = 0.25). By combining reconstructions of ecosystem dynamics and environmental drivers, our approach demonstrates how lake sediments may provide insights into the long-term dynamics of oxygen in lakes and its impact on aquatic fauna.
PubDate: 2017-03-27
DOI: 10.1007/s10452-017-9618-3

• Coexisting small fish species in lotic neotropical environments: evidence
of trophic niche differentiation
• Authors: Jislaine Cristina da Silva; Éder André Gubiani; Mayara Pereira Neves; Rosilene Luciana Delariva
Abstract: Abstract Differences among species and their ecological requirements are considered fundamental in determining the outcome of species interactions as well as in coexistence. Thus, species that co-occurs tends to differ in the use of resources as a way to mitigate the effects of interspecific competition, facilitating interactions between pairs of species. So, this study used a set of seven small-sized characid species with similar morphology and feeding strategies, in order to investigate the hypothesis that the coexistence these species is facilitated by the differential use of food resources. Samplings were conducted in the rivers Verde and São Domingos, Upper Paraná River basin, Brazil, in hydrological periods rainy and dry. The analysis of 1055 stomach contents, by the volumetric method, indicated that the species consumed mainly allochthonous items, such as seeds, terrestrial plants and insects. In addition, they showed inter- and intraspecific differences in the diet composition between hydrological periods, which allowed the identification of items that particularise each species and contribute to the trophic segregation between them. Despite the wide variety of food items used, it was not possible to observe a consistent pattern of widening or narrowing of the food spectrum between hydrological periods, as expected. The trophic niche overlap showed intermediate and low values in both periods. In this sense, resource partitioning among species of small characids, facilitated by exploitation of different preferential resources as well as the intraspecific variation in response to seasonal availability of resources, became evident. The alternation of items and proportions of items in the diet as well as changes in feeding behaviour in opportune moments was probably the key for the coexistence of these species.
PubDate: 2017-03-17
DOI: 10.1007/s10452-017-9616-5

• Combating aggressive macrophyte encroachment on a typical Yangtze River
lake: lessons from a long-term remote sensing study of vegetation
• Authors: Qiang Jia; Lei Cao; Hervé Yésou; Claire Huber; Anthony David Fox
Abstract: Abstract Overabundant growth of emergent lacustrine plants can cause biodiversity, ecosystem service and economic loss. The two-basined Wuchang Lake is a typical small shallow lake within the Yangtze River floodplain. Expansion of the emergent macrophyte Zizania latifolia at Wuchang Lower Lake (to 49 km2 in area, c. 87.0% of Lower Lake) has increasingly denied the local community open water for fishing since the 1980s. To better understand the causes of these changes and potential remediation, we used annual Landsat imagery from 1975 to 2012 to determine the patterns of expansion between years as well as the effects of water levels in different seasons and trophic status on the annual extent of macrophytes in the Lower Lake. These analyses showed that: (1) Z. latifolia progressively covered the Lower Lake, while remaining confined to one inlet in the Upper Lake; (2) despite the generally increasing trend, there were obvious annual variations in area of Z. latifolia; (3) variation of water level in spring contributed to between-year variation in area and was significantly negatively correlated with expansion in Z. latifolia. Based on these results, to reduce the expansion in Z. latifolia, we recommend maintaining spring Lower Lake water levels above at least at 11.6 m and better at 12 m, cutting shoots in June and July, with subsequent shoot removal in autumn.
PubDate: 2016-12-19
DOI: 10.1007/s10452-016-9609-9

• Erratum to: Elevated carbon dioxide has the potential to impact alarm cue
responses in some freshwater fishes
• Authors: John A. Tix; Caleb T. Hasler; Cody Sullivan; Jennifer D. Jeffrey; Cory D. Suski
PubDate: 2016-11-30
DOI: 10.1007/s10452-016-9608-x

• Influence of the colonizing substrate on diatom assemblages and
implications for bioassessment: a mesocosm experiment
• Authors: C. L. Elias; R. J. M. Rocha; M. J. Feio; E. Figueira; S. F. P. Almeida
Abstract: Abstract Although diatoms are important bioindicators of ecological quality, their ecological traits are still not well understood. A major issue is that of substrate preferences, which may result in differences in production, and assemblage structure and composition, and which should therefore be taken into account for ecological quality assessment studies. Thus, in this work, the periphyton grown on sand and ceramic tiles in indoor controlled channels were compared to understand whether substrate differences lead to differences in: periphyton production (chlorophyll-a), chlorophyll-b and c concentrations, diatom assemblages (diversity-Shannon-Wiener, cell density, taxonomic composition, trait proportions), and ecological quality assessments (IPS-‘Indice de Polluosensibilité Spécifique’). A combined inoculum of periphyton from four Portuguese streams was introduced to the running channels (six sand and six tile) and left to colonize for 35 days. Epilithic (tiles) and epipsammic (sand) assemblages were sampled at days 14 and 35. We verified that there were no differences in chlorophyll-a concentration over time and between substrates. On both sampling occasions, the epipsammic assemblages had higher concentration of chlorophyll-c and diatom density but without significant differences over time in each substrate. The taxonomic composition was different between substrates and over time. However, these differences were not reflected in ecological quality assessment. The diversity was also similar between substrates in both sampling occasions, but it was higher at day 14. Mobile and stalked species were more abundant over the entire study and differed significantly between substrates, with the epipsammic assemblages presenting higher abundances of both traits. We concluded that the colonizing substrate influences diatom assemblages but not the ecological quality assessment.
PubDate: 2016-10-26
DOI: 10.1007/s10452-016-9605-0

• Impacts of sediment type on the performance and composition of submerged
macrophyte communities
• Authors: Lin Liu; Xiang-Qi Bu; Jun-Yan Wan; Bi-Cheng Dong; Fang-Li Luo; Hong-Li Li; Fei-Hai Yu
Abstract: Abstract To restore deteriorated lake ecosystems, it is important to identify environmental factors that influence submerged macrophyte communities. While sediment is a critical environmental factor for submerged macrophytes and many studies have examined effects of sediment type on the growth of individual submerged macrophytes, very few have tested how sediment type affects the growth and species composition of submerged macrophyte communities. We constructed submerged macrophyte communities containing four co-occurring submerged macrophytes (Hydrilla verticillata, Myriophyllum spicatum, Ceratophyllum demersum and Chara fragilis) and subjected them to three sediment treatments, i.e., clay, a mixture of clay and quartz sand at a volume ratio of 1:1 and a mixture at a volume ratio of 1:4. Compared to the clay, the 1:1 mixture treatment greatly increased overall biomass, number of shoot nodes and shoot length of the community, but decreased its diversity. This was because it substantially promoted the growth of H. verticillata within the community, making it the most abundant species in the mixture sediment, but decreased that of M. spicatum and C. demersum. The sediment type had no significant effects on the growth of C. fragilis. As a primary nutrient source for plant growth, sediment type can have differential effects on various submerged macrophyte species and 1:1 mixture treatment could enhance the performance of the communities, increasing the overall biomass, number of shoot nodes and shoot length by 39.03%, 150.13% and 9.94%, respectively, compared to the clay treatment. Thus, measures should be taken to mediate the sediment condition to restore submerged macrophyte communities with different dominant species.
PubDate: 2016-10-25
DOI: 10.1007/s10452-016-9607-y

• Effects of macrophyte-specific olfactory cues on fish preference patterns
• Authors: Charles W. Martin
Abstract: Abstract Vegetated habitats provide numerous benefits to nekton, including structural refuge from predators and food sources. However, the sensory mechanisms by which fishes locate these habitats remain unclear for many species, especially when environmental conditions (such as increased turbidity) are unfavorable for visual identification of habitats. Here, a series of laboratory experiments test whether three species of adult fish (golden topminnow Fundulus chrysotus Günther 1866, sailfin molly Poecilia latipinna Lesueur 1821, and western mosquitofish Gambusia affinis Baird and Girard 1853) use plant chemical cues to orient to one of two habitats [hydrilla Hydrilla verticillata (L.f.) Royle or water hyacinth Eichhornia crassipes (Mart.) Solms]. First, experiments in aquaria were conducted offering fish a choice of the two habitats to determine preference patterns. Next, a two-channel flume, with each side containing flow originating in one of the two habitats, was used to determine whether preferences were still exhibited when fish could only detect habitats through olfactory means. While patterns among the three fish species tested here were variable, results did indicate consistent habitat preferences despite the lack of cues other than olfactory, suggesting that these organisms are capable of discriminating habitats via chemical exudates from plants. As such, olfactory mechanisms likely provide vital information about the surrounding environment and future work should be directed at determining how anthropogenic inputs such as eutrophication and sediment runoff affect the physiology of these sensory capabilities.
PubDate: 2016-10-22
DOI: 10.1007/s10452-016-9606-z

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