Management of non-indigenous invasive species (NIS) is challenging owing in part to limitations of early detection and identification. The advent of environmental DNA (eDNA) techniques provides an ...efficient way to detect NIS when their abundance is extremely low. However, eDNA-based methods often suffer from uncertain detection sensitivity, which requires detailed testing before applying these methods in the field. Here we developed an eDNA tool for early detection of the highly invasive golden mussel,
Limnoperna fortunei
, based on the mitochondrial cytochrome
c
oxidase subunit I gene (COI). Further, we tested technical issues, including sampling strategy and detection sensitivity, based on a laboratory experiment. We then applied the method to field samples collected from water bodies in China where this mussel has or is expected to colonize. Results showed that the detection limit varied extensively among our newly developed primer pairs, ranging from 4 × 10
−2
to 4 × 10
−6
ng of total genomic DNA. Laboratory detection was affected by the availability of eDNA (i.e., both mussel abundance and incubation time). Detection capacity was higher in laboratory samples containing re-suspended matter from the bottom layer versus that collected from the surface. Among 25 field sites, detection was 100% at sites with high mussel abundance and as low as 40% at sites with low abundance when tested using our most sensitive primer pair. Early detection of NIS present at low abundance in nature requires not only sensitive primers, but also an optimized sampling strategy to reduce the occurrence of false negatives. Careful selection and detailed testing of primer pairs ensures effective eDNA-based species detection in surveillance and management programs.
Environmental DNA (eDNA) has increasingly been used to detect rare species (e.g., newly introduced nonindigenous species) in both terrestrial and aquatic ecosystems, often with distinct advantages ...over traditional methods. However, whether water eDNA signals can be used to inform invasion risks remains debatable owing to inherent uncertainties associated with the methods used and the varying conditions among study systems. Here, we sampled eDNA from canals of the central route of the South‐to‐North Water Diversion Project (hereafter SNWDP) in China to investigate eDNA distribution and efficacy to inform invasion risks in a unique lotic system. We first conducted a total of 16 monthly surveys in this system (two sites in the source reservoir and four sites in the main canal) to test if eDNA could be applied to detect an invasive, biofouling bivalve, the golden mussel Limnoperna fortunei. Second, we initiated a one‐time survey in a sub‐canal of the SNWDP using refined sampling (12 sites in ~22 km canal) and considered a few environmental predictors. We found that detection of target eDNA in the main canal was achieved up to 1100 km from the putative source population but was restricted to the warmer months (May–November). Detection probability exhibited a significant positive relationship with average daily minimum air temperature and with water temperature, consistent with the expected spawning season. eDNA concentration in the main canal generally fluctuated across months and sites and was generally higher in warmer months. Golden mussel eDNA concentration in the sub‐canal decreased significantly with distance from the source and with increasing water temperature and became almost undetectable at ~22 km distance. Given the enormity of the SNWDP, golden mussels may eventually expand their distribution in the main canal, with established “bridgehead” populations facilitating further spread. Our findings suggest an elevated invasion risk of golden mussels in the SNWDP in warm months, highlighting the critical period for spread and, possibly, management.
摘要
环境DNA(eDNA)已被越来越多地用于检测陆地和水生生态系统中的稀有物种(例如:新引入的外源物种)，相较于传统方法，其通常表现出明显优势。然而，由于所用方法固有的不确定性和不同研究系统的差异，水体eDNA信号是否可用于揭示入侵风险仍有争议。本研究中，我们从中国南水北调中线工程(以下简称南水北调工程)的渠道中提取eDNA样本，研究eDNA在这样一个独特的动水系统中的分布及其揭示入侵风险的效果。首先，我们在这一系统中进行了16次月度调查(涵盖源水库2个站点和干渠4个站点)，以测试eDNA是否可以用于检测入侵生物沼蛤Limnoperna fortunei，一种生物污损双壳贝类。其次，我们在干渠的一个支渠中，采用更加精细的取样方法(在约22公里的渠道中设置12个样点)，开展了一次考察多个环境因子的调查。我们发现，在距离假定源种群1100公里的干渠中可以检测到目标eDNA，但仅限于温暖的月份(5–11月)。目标eDNA的检出概率与日平均最低气温和水温呈显著正相关，这与预期的产卵季节一致。在支渠中，沼蛤eDNA浓度随着与源头的距离增加和水温的升高而明显下降，在约22公里处变得几乎无法检出。鉴于南水北调工程的巨大规模，沼蛤最终可能无法避免地扩张其在干渠的分布，已定殖的 “桥头堡 “种群会促进其进一步传播。我们的研究揭示了南水北调工程在温暖月份中升高的沼蛤入侵风险，凸显了其扩散和潜在管理的关键窗口期。
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•Golden mussels have a type I functional response.•Suppressive effect on suspended matter is mussel abundance-dependent.•Size of suspended particles affects their capture efficiency ...by golden mussels.
Filter feeding activities link suspension feeders with their environment and underpin their impact on aquatic ecosystems. Despite their ecological and economic impacts, the functional response and size-selective capture of suspended particulates have not been well documented for the golden mussel Limnoperna fortunei. Here we demonstrated that golden mussels had a type I functional response, with an attack rate a = 0.085 and negligible handling time (h). Clearance rate ranged between 72.6 ± 27.0 and 305.5 ± 105.9 mL ind.-1h−1 (Mean ± S.E.), depending on food concentrations, which exhibited an inverse relationship with clearance rate. Presence of golden mussels suppressed chlorophyll a concentration in experimental mesocosms, the extent of which was dependent on mussel abundance. Concentration of suspended particles in experimental mesocosms experienced a sharp initial decline across all size categories (≤1–>50 μm), though with increased final concentration of large particles (>25 μm), indicating packaging and egestion by golden mussels of fine particles (down to ≤1 μm). Capture efficiency of quantitatively-dominant suspended matter (≤1−50 μm) by golden mussels was inversely related to particle size. Animal abundance, particle size, and their interaction (abundance × particle size) determined the extent to which matter was removed from the water column. Presently L. fortunei occurs primarily in the southern end of the central route of South to North Water Diversion Project (China), but the species is spreading north; we anticipate that impacts associated with filtering of L. fortunei will correspond with local population abundance along this gradient.
Many countries/areas are experiencing or may soon experience water scarcity owing to rapid population growth, urbanization and/or climate change. Currently, almost one-fifth of the world’s population ...(1.2 billion) live in areas of physical water scarcity. Water diversions have become a commonplace solution proposed by governments for alleviation of physical water scarcity. Thus far, more than 80 major projects are completed or under construction globally, including the world’s largest diversion: South-to-North Water Transfer Project (SNWTP) in China. Negative effects associated with water diversions, such as habitat loss and transfer of pollutants, have been recognized. However, it has been largely overlooked that “invasion highways” are created when water diversions link biogeographic regions. These “invasion highways” can facilitate spread of an array of non-native species. Although previous experiences have provided clear warnings regarding spread of non-native invasive species through artificial waterways, these lessons have been largely ignored by governments when resolving water scarcity problems. Here we use SNWTP, which will likely facilitate spread of invasive golden mussels, as well as many known examples of non-native invasive species spread through artificial waterways in other water systems, to call on governments to formally establish policy and seek management solutions to considering spread of non-native species when planning water diversions.
The microbial food-loop is critical to energy flow in aquatic food webs. We tested the hypothesis that species composition and relative abundance in a microbial community would be modified by the ...development of toxic algal blooms either by enhanced carbon production or toxicity. This study tracked the response of the microbial community with respect to composition and relative abundance during a 7-day algal bloom event in the Three Gorges Reservoir in May 2018. Chlorophyll a biomass, microscopic identification and cell counting of algae and algal abundance (ind. L−1) and carbon, nutrient concentrations (total phosphorus and nitrogen, dissolved total phosphorus and nitrogen), and DNA high throughput sequencing were measured daily. Algal density (1.2 × 109 ind. L−1) and Chlorophyll a (219 μg L−1) peaked on May 20th–21st, when the phytoplankton community was dominated by Chlorella spp. and Microcystis spp. The concentrations of both dissolved total nitrogen and phosphorus declined during the bloom period. Based on DNA high throughput sequencing data, the relative abundance of eukaryotic phytoplankton, microzooplankton (20–200 μm), mesozooplankton (>200 μm), and fungal communities varied day by day while the prokaryotic community revealed a more consistent structure. Enhanced carbon production during the bloom was closely associated with increased heterotrophic microbial composition in both the prokaryotic and eukaryotic communities. A storm event, however, that caused surface cooling and deep mixing of the water column greatly modified the composition and relative abundance of species in the microbial loop. The high temporal variability and dynamics observed in this study suggest that many factors, and not just algal blooms, were interacting to determine the composition and relative abundance of species of the microbial loop.
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•Temporal stability of microbial loop of a riverine-lake was investigated.•Carbon production from a cyano-bloom stimulated heterotrophy of microbial loop.•Fungi and microzooplankton were negatively related during the algal bloom.•Storm events modified the composition and abundance of species of microbial loop.
Photoferrotrophs thrive in an Archean Ocean analogue Crowe, Sean A; Jones, CarriAyne; Katsev, Sergei ...
Proceedings of the National Academy of Sciences - PNAS,
10/2008, Letnik:
105, Številka:
41
Journal Article
Recenzirano
Odprti dostop
Considerable discussion surrounds the potential role of anoxygenic phototrophic Fe(II)-oxidizing bacteria in both the genesis of Banded Iron Formations (BIFs) and early marine productivity. However, ...anoxygenic phototrophs have yet to be identified in modern environments with comparable chemistry and physical structure to the ancient Fe(II)-rich (ferruginous) oceans from which BIFs deposited. Lake Matano, Indonesia, the eighth deepest lake in the world, is such an environment. Here, sulfate is scarce (<20 μmol·liter⁻¹), and it is completely removed by sulfate reduction within the deep, Fe(II)-rich chemocline. The sulfide produced is efficiently scavenged by the formation and precipitation of FeS, thereby maintaining very low sulfide concentrations within the chemocline and the deep ferruginous bottom waters. Low productivity in the surface water allows sunlight to penetrate to the >100-m-deep chemocline. Within this sulfide-poor, Fe(II)-rich, illuminated chemocline, we find a populous assemblage of anoxygenic phototrophic green sulfur bacteria (GSB). These GSB represent a large component of the Lake Matano phototrophic community, and bacteriochlorophyll e, a pigment produced by low-light-adapted GSB, is nearly as abundant as chlorophyll a in the lake's euphotic surface waters. The dearth of sulfide in the chemocline requires that the GSB are sustained by phototrophic oxidation of Fe(II), which is in abundant supply. By analogy, we propose that similar microbial communities, including populations of sulfate reducers and photoferrotrophic GSB, likely populated the chemoclines of ancient ferruginous oceans, driving the genesis of BIFs and fueling early marine productivity.
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