Fee O.H. SmuldersS. Tatiana BeckerJustin E. Campbell
12页
查看更多>>摘要：The success of invasive macrophytes can depend on local nutrient availability and consumer pressure, which may interact. We therefore experimentally investigated the interacting effects of nutrient (nitrogen and phosphorus) addition, the exclusion oflarge herbivorous fishes and mimicked grazing on the expansion rates of the invasive seagrass Halophila stipulacea. The experiments were established on Bonaire and Aruba, two islands in the southern Caribbean, which differ in fish community structure. Weobserved that multiple Caribbean fish species feed on H. stipulacea. At both study sites, nutrient enrichment decreased invasive leaf carbon:nitrogen ratios. However only on Bonaire, where herbivore fish abundance was 7 times higher and diversity was 4.5 times higher, did nutrient enrichment result in a significant reduction of H. stipulacea expansion into native Thalassia testudinum meadows. This effect was likely due to increased herbivory on nutrient enriched seagrass leaves, as we found that excluding large herbivorous fish (e.g. parrotfish) doubled invasive expansion rates in bare patches on Bonaire. On Aruba, H. stipulacea expansion rates were higher overall, which coincided with lower abundances and diversity of native fishes, and were limitedby mimicked fish grazing. We suggest that top-down control by the native fish community may counteract eutrophication effects by increased grazing pressure on nutrient-rich invasive seagrass leaves. We conclude that diverse and abundant herbivore communities likely play an important role in limiting invasion success and their conservation and restoration may serve as a tool to slow down seagrass invasions.
Glisson, Wesley J.Muthukrishnan, RanjanWagner, Carli K.Larkin, Daniel J....
5页
查看更多>>摘要：Understanding the phenology of the invasive macroalga Nitellopsis obtusa (starry stonewort) is critical for evaluating and predicting its impacts on native macrophytes and timing control efforts. We tracked N. obtusa phenology in two Minnesota (USA) lakes from 2017 to 2018. We measured N. obtusa biomass and counted bulbils (asexual reproductive structures) throughout the growing season and in winter, under ice. Additionally, we compared phenology of N. obtusa to other invasive and native macrophytes using a long-term, Minnesota statewide dataset. We found consistent late-season peaks in N. obtusa biomass in both lakes, and this extended growth distinguished it from common native and invasive macrophytes in the region. Phenological asynchrony of N. obtusa relative to native macrophytes indicates use of a distinct temporal niche that may contribute to its invasion success. Bulbil counts were lowest early to mid-summer and increased through fall; however, high variability in this relationship warrants more intensive sampling to clarify seasonal trends. Late-season growth of N. obtusa poses challenges for timing control efforts, as early-season treatments may be limited to avoid harming native species. Treatment during peak biomass, before peak bulbil abundance, may improve control.
查看更多>>摘要：Submerged plants are crucial for maintaining a clear water state in lakes, and their distribution area is usually determined by the lowest distribution boundary (LDB). However, LDBs of submerged macrophytes often exhibit species differences and vary with seasonal water level fluctuations. In this study, we carried out a three-year field investigation to compare differences in the LDBs of three submerged macrophyte species (i.e., Vallisneria natans, Ceratophyllum demersum, and Potamogeton maackianus) and explore their distinct determinants. We assumed that LDB differences would exist among the three species and that water level (WL) would be a key environmental driver of LDB dynamics, with an association between the LDBs of submerged macrophytes and water level fluctuations. Indeed, our results showed significant seasonal differences between C. demersum and V. natans in the period of September - May, with mean annual values in the order (low to high) V. natans, C. demersum, and P. maackianus. Furthermore, water level was a major driving force of the LDB dynamics of the three species. Changes in the LDBs of the three species in response to water level fluctuations could be divided into three periods: i.e., recovery growth period (April to June), stress tolerance period (July to September), and recession period (October to following March). This study not only clarifies the impact of water level on submerged macrophyte growth and distribution, but also has larger practical implications for the ecological restoration and management of large deep lakes.
查看更多>>摘要：Submerged plants are crucial for maintaining a clear water state in lakes, and their distribution area is usuallydetermined by the lowest distribution boundary (LDB). However, LDBs of submerged macrophytes often exhibitspecies differences and vary with seasonal water level fluctuations. In this study, we carried out a three-year fieldinvestigation to compare differences in the LDBs of three submerged macrophyte species (i.e., Vallisneria natans,Ceratophyllum demersum, and Potamogeton maackianus) and explore their distinct determinants. We assumed thatLDB differences would exist among the three species and that water level (WL) would be a key environmentaldriver of LDB dynamics, with an association between the LDBs of submerged macrophytes and water levelfluctuations. Indeed, our results showed significant seasonal differences between C. demersum and V. natans inthe period of September - May, with mean annual values in the order (low to high) V. natans, C. demersum, andP. maackianus. Furthermore, water level was a major driving force of the LDB dynamics of the three species.Changes in the LDBs of the three species in response to water level fluctuations could be divided into threeperiods: i.e., recovery growth period (April to June), stress tolerance period (July to September), and recessionperiod (October to following March). This study not only clarifies the impact of water level on submergedmacrophyte growth and distribution, but also has larger practical implications for the ecological restoration andmanagement of large deep lakes.
Magda F. El-AdlMohamed A. DeyabRadwa S. El-Shanawany
11页
查看更多>>摘要：This study aims at investigating the use of fatty acid constituents from two abundant algal species: the marine Chaetomorpha vieillardii (Kutzing) M.J.Wynne 2011 and the freshwater Cladophora glomerata (Linnaeus) Kutzing 1843 as natural antimicrobialagents. Water samples and massive growth of Egyptian species C. vieillardii and C. glomerata, causing environmental problems, were collected from Port Said and Ras El-Bar, respectively. After hexane extraction, the fatty acids were investigated for the bioactivity against seven pathogens; three Gram-negative bacteria: Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa, and four fungi: Aspergillus niger, Alternaria alternata, Candida albicans, and Penicillium chrysogenum. Generally, theantimicrobial activity of C. vieillardii was stronger than that of C. glomerata. However, C. vieillardii extract was inefficient against P. aeruginosa and C. albicans whereas C. glomerata extract was inefficient against E. coli and P. chrysogenum. Transmission electron microscopy (TEM) of C. vieillardii extract-treated pathogens revealed distortion of cell shape and size of K. pneumoniae and membrane disorganization, cytoplasm disintegration, and vacuolation in Aspergillus niger. The results concluded that the fatty acids of blooming algal species, C. vieillardii and C. glomerata, can be manipulated as economic and safe antimicrobial agents.
查看更多>>摘要：While attention in coastal ecosystem restoration has increased over the last two decades, the success rate of efforts remains relatively low. To increase success rates, physical restoration techniques often utilize supporting or protective materials to provide a stable surface for transplantation, and in some cases reduce herbivory and hydrodynamic disturbances. In this study, we evaluated the effectiveness of traditional (staples, burlap) and novel (BESE- elements, a biodegradable potato starch lattice) physical restoration techniques on the growth of transplanted Halodule wrightii seagrass. A first experiment revealed that seagrass planted in both two-stacked BESE structure without planting holes and four-stacked BESE with holes had significantlyhigher shoot count and blade length than four-stacked BESE without holes, with the latter design losing all seagrass shortly after deployment as shoots could not float through the structure. In a second experiment, the BESE lattice treatment (four-stacked with holes) had three times the shoot count and equal to greater blade length compared to traditional methods of physical restoration (staples and burlap), likely due to BESE providing some protection from hydrodynamic activity. However, disturbances,possibly including herbivory and hydrodynamic activity (culminating with Hurricane Irma), prevented long term study, illustrating the importance of stochastic abiotic factors in seagrass planting success. Overall our study demonstrates the effectivenessof using BESE lattice designs and similar physical techniques in the restoration of seagrass beds.
查看更多>>摘要：While attention in coastal ecosystem restoration has increased over the last two decades, the success rate of efforts remains relatively low. To increase success rates, physical restoration techniques often utilize supporting or protective materials to provide a stable surface for transplantation, and in some cases reduce herbivory and hydrodynamic disturbances. In this study, we evaluated the effectiveness of traditional (staples, burlap) and novel (BESE- elements, a biodegradable potato starch lattice) physical restoration techniques on the growth of transplanted Halodule wrightii seagrass. A first experiment revealed that seagrass planted in both two-stacked BESE structure without planting holes and four-stacked BESE with holes had significantlyhigher shoot count and blade length than four-stacked BESE without holes, with the latter design losing all seagrass shortly after deployment as shoots could not float through the structure. In a second experiment, the BESE lattice treatment (four-stacked with holes) had three times the shoot count and equal to greater blade length compared to traditional methods of physical restoration (staples and burlap), likely due to BESE providing some protection from hydrodynamic activity. However, disturbances,possibly including herbivory and hydrodynamic activity (culminating with Hurricane Irma), prevented long term study, illustrating the importance of stochastic abiotic factors in seagrass planting success. Overall our study demonstrates the effectivenessof using BESE lattice designs and similar physical techniques in the restoration of seagrass beds.
查看更多>>摘要：Diatoms make an important contribution to the total primary production in Zostera beds. The study of the vertical distribution of diatoms in the canopy of Zostera noltii Hornemann 1832 and its relationship with the biomass and height of the host species was the goal of this paper.The Z. noltii canopy with a height of 39.2 ± 0.91 cm was divided into eight horizontal layers with a step of 5 cm. The mean biomass of the eelgrass canopy leaves per bottom area was 0.240 ± 0.091 kg dry weight (d.w.) m_2.On the leaves, stems, and rhizomes of Z. noltii, 34 diatom species belonging to 24 genera were found. In terms of relative cell density (43 ± 15.6%) and biomass (57.5 ± 15.2%), Cocconeis scutellum var. scutellum was the dominant species. In different layers of the canopy, the total abundance of diatoms and their biomass on Zostera per unit of its phytomass varied widely from 0.88-105 to 2.95-10 cells g_ and from 0.24 to 2.10 mg g_ , respectively. The total abundance of diatoms and their biomass on Zostera leaves per bottom area covered by the canopy reached, on average, (54.879 ± 20.675)-10 cells m_ and 0.332 ± 0.126 g m_2, respectively. The total mass of diatoms averaged 0.046 ± 0.0006% per wet weight of the aboveground part of Zostera. It is suggested that two factors play an important role in the distribution of diatoms in the horizontal layers of the Z. noltii canopy: the amount of the surface area available for settlement and its morphological characteristics.
查看更多>>摘要：Seagrass meadows with more than two species co-occurring at a small scale are unusual in temperate regions, and such multispecies seagrass beds are undocumented in the Northeastern Pacific. Seagrasses in multispecies beds may coexist through trait differentiation in body size, life history types and phenology, especially when competitive exclusion is interrupted by environmental variability. Here, we survey and manipulate a multispecies seagrass meadow in Willapa Bay, Washington (USA), containing Zostera marina, Zostera japonica and Ruppia maritima; our 13-month survey is the first formal documentation of multispecies seagrass bed occurrence in the Northeastern Pacific. Z. japonica, a non-native species, reached an end-of-summer biomass that was an order of magnitude greater than either native seagrass. To test competition, we experimentally removed Z. japonica and found competition occurred disproportionately on the smaller R maritima relative to larger Z. marina. R. maritima germinated later and senesced earlier than the two Zostera species, and the removal of Z. japonica positively affected R. maritima biomass, supporting previous studies that R. maritima is an opportunistic species. In addition to species-specific phenology and body size, all species presented annual life histories and thus began each annual cycle under high resource availability, such as light, space and nutrients, which may contribute to coexistence.
Naiane Maria Correa dos SantosPriscila Goncalves MonteiroEvander Alves Ferreira
11页
查看更多>>摘要：There is a need for efficient technologies to remove atrazine residues that are detected in water bodies. These residues are harmful as they intoxicate plankton and may decrease oxygen in the water. This study evaluated the growth, physiology, and leaf anatomy of Eichhornia crassipes and Pistia stratiotes that were exposed to atrazine for phytoremediation purposes. To carry out this evaluation, atrazine concentrations ranging from 0 to 1000 ug L~(-1) were added into 5 L pots with macrophytes, which were maintained for 28 d in these solutions. Following this period, atrazine toxicity, chlorophyll content, and dry mass were measured. High-performance liquid chromatography was used to quantify residual atrazine concentrations in the solution and plantmaterial samples. It was found that E. crassipes was sensitive to an atrazine concentration of 1000 ug L~(-1) . Atrazine reduced macrophyte growth, promoted a decrease in chlorophyll, and altered anatomical parameters; however, plant growth was uninterrupted, and macrophytes remained physiologically active until the evaluation period. The residual atrazine concentrations in solution were 35.56% and 79.19% for E. crassipes and 76.13% and 78.83% for P. stratiotes, respectively; this was lower than plantsthat were unpotted for atrazine concentrations of 10 and 100 ug L~(-1) . The results indicate that E. crassipes and P. stratiotes may be suitable phytoremediators in aquatic ecosystems for atrazine concentrations up to 10 and 100 ug L~(-1) , respectively.
NSTL
Elsevier