查看更多>>摘要：? 2022 Elsevier B.V.Climate change, habitat loss, nutrient pollution, and other anthropogenic impacts cause seagrass degradation globally. Like other seagrass species, Thalassia hemprichii is threatened by these factors. A better knowledge about genetic diversity within and among populations would support and guide prudent conservation strategies. In Viet Nam, T. hemprichii is found mainly in two habitats including hard substratum in the open sea and the soft, muddy sand substratum in lagoons. In this present study, 106 individuals of T. hemprichii collected from eight populations along the southern coast of Viet Nam were used to evaluate the genetic diversity and population structure via 10 loci of microsatellite markers. Based on the pairwise FST, relatively low genetic differentiation was detected among T. hemprichii populations. Statistically significant pairwise population genetic differentiation was found among almost all populations. Cluster, structure, and AMOVA analysis also showed that the eight populations were separated into two groups in agreement with the two different habitat types. Significant positive correlations exist between geographic and genetic distances. The genetic diversity exhibitd by three of the eight populations suggests that these three populations need protection priority.
查看更多>>摘要：? 2022 Elsevier B.V.Ecklonia radiata is a dominant kelp across much of the southern hemisphere supporting vast economic, social and ecological values. It is also of emerging interest for aquaculture industries and in blue carbon sequestration. Despite its importance, genomic resources of this key species are scant, yet could provide important knowledge to better manage, cultivate and conserve this species in our changing oceans. In this study we report the complete mitochondrial and draft chloroplast genome for E. radiata. The mitochondrial genome is 37,696 bp in length and contains 66 annotated genes. Two alternative scaffold arrangements were recovered for the chloroplast genome, both of 130,955 bp and differing only in the orientation of a single ~ 43 kbp contig. Annotation of the plastid scaffolds identified 175 genes and two large inverted repeats that are typical of brown algal chloroplast genomes. Comparisons to other kelp genomes indicate that the gene sets reported here are likely complete. The recovery of two chloroplast scaffold assembly arrangements hints at the possibility of heteroplasmy in E. radiata though this requires further investigation. The genomic information reported here will aid in understanding functional response of E. radiata in changing oceans, enhance the development of E. radiata as an aquaculture resource and support efforts to conserve this ecologically important marine species.
de Morais M.da Silva C.J.dos Santos C.da Silva Nunes J.R....
9页
查看更多>>摘要：? 2022Spatial and temporal variation in limnological variables, as well as local changes in the hydrological pattern, may affect inundation hydrology and alter biotic interactions and functional diversity of aquatic macrophyte communities in the Pantanal. The objectives of this research in the floodplain along the Paraguay River were to: 1) examine changes in the diversity of aquatic macrophyte communities over a ten-year period based on surveys taken in 2008 and 2018; and 2) evaluate the possible indirect relation of changes in rainfall patterns, which in turn affect lateral hydrological connectivity and limnological variables that directly affect the composition and productivity of the aquatic macrophyte community. Comparison of data taken in 2008 and 2018 revealed a change in the timing and a reduction in the number of rainy days. These changes in rainfall patterns coincided with limnological changes, including increases in transparency, pH, dissolved oxygen, ammonium, nitrate, total nitrogen, orthophosphate, and total phosphorus, as well as decreases in water temperature and connectivity. Species richness of aquatic macrophyte communities in three ecological zones of the Paraguay River floodplain increased between 2008 and 2018, with increases in emergent grasses, emergent non-grasses, and amphibious life forms, showing a trend that favors species that are more adapted to drought conditions. The seasonal pattern of inundation and desiccation, as well as dissolved oxygen and temperature, where correlated with macrophytes communities variations. The colonization and expansion of rooted emergent macrophytes over this period could be a response to local anthropogenic activities, hydrological trends, or may reflect interannual rainfall variability.
查看更多>>摘要：? 2022 Elsevier B.V.Seagrass meadows are valuable coastal habitats that require sufficient light to flourish. A laboratory experiment was performed to measure the response of the seagrass Zostera muelleri to different levels of irradiance. Plants from a New Zealand estuary were grown submersed in artificial seawater for six weeks at five different daily irradiance levels ranging from 0.3 to 7.3 mol m-2 d-1. Plants were extinguished within three weeks at ≤ 1.4 mol m-2 d-1, showed some growth but then declined at 2.9 mol m-2 d-1 while biomass, quantified as total leaf area, doubled at 7.3 mol m-2 d-1. The results indicate that Z. muelleri is likely to require at least 7.3 mol m-2 d-1 of daily irradiance under average summer water temperatures of 20 °C to maintain growth and above-ground biomass accrual. The irradiance requirements for this and other seagrass species that grow in the subtidal zone are anticipated to increase as ocean water temperatures rise, highlighting the critical importance of actions to maintain and improve coastal water clarity.
查看更多>>摘要：? 2022 Elsevier B.V.Seagrasses are found at limited locations in the Eastern Tropical Pacific (ETP). Here, we provide the first characterization of seagrasses at Sámara Bay, on the northern Pacific coast of Costa Rica. Sampling was carried out in August 2018 and March 2019. We measured seagrass biomass, shoot density, leaf area, stable isotope composition (δ13C, δ15N), carbon content, bulk density, and grain size. We also measured water clarity, temperature, dissolved oxygen, salinity, and nutrient concentrations. Two seagrass species were found, Halophila baillonii and Halodule beaudettei, which are commonly found in the ETP. Sediment grain size at Sámara was mostly composed of fine and very fine sand. Total seagrass biomass was 31.9 ± 28.7 g DW m?2 and density was 2136 ± 1576 shoots m?2. Halophila bailloni leaf blade length (1.1 ± 0.3 cm) and width (0.5 ± 0.1 cm) were within ranges for the sizes reported for this species, and were similar to other locations. Halodule beaudettei leaf length (5.0 ± 3.8 cm) and width (0.09 ± 0.02 cm), were larger than at other seagrass meadows on the Pacific coast of Costa Rica yet smaller than in Brazil. Seagrass biomass and density at Sámara were higher in the sampling during the dry season, a pattern also found on the Pacific coast of Costa Rica and in Brazil. We recommend further study of seagrasses at this site and the ETP, including temporal and spatial variability and associated environmental factors. Seagrass presence at Sámara should be considered in local management and conservation initiatives.
查看更多>>摘要：? 2021 Elsevier B.V.Spartina anglica originated from interspecific hybridization between S. alterniflora and S. maritima which produced a sterile hybrid S. × townsendii. Subsequent whole genome duplication of the hybrid, gave rise to a vigorous allopolyploid S. anglica. In earlier studies, both parental nuclear sequences were detected in S. anglica. However, to date, parental copies of nuclear ribosomal DNA (nrDNA) have not been detected in a phylogenetic context. In the present study, we used the nuclear internal transcribed spacer (ITS) region in conjunction with chloroplast DNA (trnL-trnF, matK, and rbcL) to infer the hybrid origin of S. anglica invading Korean coasts. Our results revealed that the chloroplast DNA sequences of S. anglica were similar to those of S. alterniflora, which confirms its maternal origin. However, in the nuclear rDNA ITS region, we detected two highly divergent groups of ITS sequences that were divided between the two parent lineages. The maternal copies were indistinguishable from S. alterniflora, while the paternal repeats were highly differentiated from S. maritima and exhibited characteristics of ITS pseudogenes. This indicates that S. anglica has undergone rapid changes at the rDNA loci after the allopolyploid formation. Our study demonstrated the two divergent copies of ITS sequences, thus resolving the phylogenetic hybrid origin of S. anglica. This study offers further insights into the evolutionary history of S. anglica.
查看更多>>摘要：? 2021 Elsevier B.V.The free-floating aquatic plant Utricularia australis has typically subsurface shoots and subaerial showy inflorescences. To find it growing with large populations among benthic Chara stands at 4–6 m depth in two Central Italian lakes, is a phenomenon that was never previously reported. Production of showy chasmogamous flowers at this depth makes such finding yet increasingly intriguing. Here we make quantitative-qualitative comparisons of morphological characters among subaerial and underwater flowers taken from diverse sites in Central Italy. Environmental data were used to delineate differences between superficial and underwater habitats where flowering U. australis populations were found, and to help explain these extraordinary findings. Although similar, the subaerial and underwater flowers did show some differences, the most important being the length of the floral scape. Underwater scapes were around three times longer than those emerged. This might be a typical phototropic-response or a failed attempt to get flowers above water surface for allowing entomophilous pollination, or a redundant morpho-physiological trait as a result of a recent ecological move. Underwater flowers were generally smaller, but they did have longer styles, nectar signalling was less obvious, thinner petals, mucous-coated pollen (subaerial pollen is dry and grainy). Both types of flower were sterile, producing abortive fruits. Possibility of underwater ecological conditions causing stress-induced flowering is also proposed. A lack of water movement is an important ecological requirement for U. australis growth and could explain why large populations have been found in deep water far from its typical habitat.
查看更多>>摘要：? 2022 Elsevier B.V.This study aimed to elucidate for the first time the combined effects of marine heatwaves (MHWs) and light limitation simulated in mesocosm on critical physiological descriptors of the surfgrass Phyllospadix torreyi, which constitutes highly productive meadows along the intertidal and subtidal rocky shores of the Pacific coast of North America. Our results revealed that short-term exposure (~7 days) to extreme thermal anomalies of + 9 °C had positive effects on the photosynthetic capacities of P. torreyi, as indicated by increments in maximum photosynthetic rates, photosynthetic efficiency (α), maximum electron transport rate, and effective quantum yield. Despite that its photosynthetic performance was enhanced, exposure to warming caused a decrease in its internal carbon reserves (i.e. energy status), likely as a consequence of carbon mobilization/utilization to activate heat-stress responses. Plants exposed to light limitation (i.e. sub-saturating irradiance of 30 μmol photon m?2 s?1) generally exhibited an increase in α and/or a decrease in respiration, which ultimately allowed for a reduction in plant compensation irradiance. The combination of low light and seawater warming resulted in a decrease in non-structural carbohydrates content, daily net-productivity, and leaf growth rates. Gross photosynthetic rates at control saturating irradiance exhibited higher activation energy and, thus, greater responsiveness to seawater warming than plants kept under light limitation. While our results indicated that unusual warming events might favor the photosynthetic performance of P. torreyi, combining this condition with a drastic light reduction can lead to internal carbon depletion and potentially compromise plant survival in the long term.
查看更多>>摘要：? 2022 Elsevier B.V.Seaweeds provide important ecosystem functions in shallow temperate rocky reefs including carbon uptake. The macroalgae communities in shallow reefs off the south-eastern Mediterranean shores have shifted dramatically due to bioinvasions and possibly ocean warming over the past few decades. These changes have likely caused and will continue to shift the ecosystem functionality and carbon sequestration capacity of these reefs. In order to assess the potential changes in carbon sequestration capacity, it is important to determine the organic reservoir contained in the biomass of the native as well as the increasingly dominant alien algal species, for which biometric relationships can serve as good proxies. Between 2017 and 2020, we collected samples of nine species of native and non-native seaweeds that currently dominate the hard substrate of shallow reefs along the northern Israeli Levantine coast. For each species, we provide the biometric relationships between wet weight, dry weight and ash-free dry weight and report the equations for the conversions between the different mass-calibrations. Comparison between species, indicate that organic matter content in Ochrophyta is generally greater than Rhodophyta. Furthermore, seasonality was detected in some metrics of the tested species. Our results provide basic tools for assessing the impacts of climate change and bioinvasions in terms of carbon sequestration potential in shallow water seaweed communities of the Levantine and possibly other regions.
查看更多>>摘要：? 2022 Elsevier B.V.The seagrass Halodule wrightii (shoal grass) is found throughout the Caribbean and Gulf of Mexico where it can be an important or dominant component of the flora. It is generally more tolerant to disturbance than other seagrass species, including tolerance to reduced salinity. This study investigated the low salinity tolerance of a population of H. wrightii that has a long history of exposure to river flooding located at Cat Island, Mississippi (MS). Plants were collected after record prolonged flooding of the Mississippi River in 2019 and subsequent reduced salinities at Cat Island, MS, then allowed to recover at a salinity of 25 before being subject to three low salinity exposures of 5, 10, and 15. Plants were still alive after more than 12 months even at the lowest salinity of 5. Morphological and biomass metrics were recorded at the end of this prolonged low-salinity exposure. Plants exhibited low biomass and shoot density. This population of H. wrightii was able to survive very low salinities for longer than previously reported. Other seagrass populations with enhanced tolerance to abiotic stressors may become important for survival as climate change alters coastal habitat conditions.
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