A comparative study of ecophysiological traits of the invasive species Lemna minuta Kunth and the native Lemna minor Linnaeus

Invasive aquatic plants are a major threat to biodiversity and a considerable amount of money is spent on their management and control. In this study the invasiveness of the alien freshwater plant Lemna minuta was investigated. The performance of this species under different environmental conditions was tested and compared with the performance of the native species Lemna minor. Physiological and morphological parameters were used to quantify the performance of the two species and interpret the growth strategies adopted. In fully controlled conditions, L. minuta and L. minor were grown using different nutrient concentrations, different light intensities and in the presence of several physical and chemical stressors. In parallel, the presence and abundance of L. minuta, and L. minor was monitored for two years in natural freshwater ponds where the two species occur spontaneously. The observation that the water fern Azolla filiculoides co-occurs very often with Lemnaceae, led us to include it in monitoring of growth performance. Also investigated was the correlation between the presence and abundance of the three species and environmental factors of the waterbody such as water chemistry and canopy shade. A one year long outdoor experiment was carried out in order to investigate the performance of the three species throughout the seasons. The laboratory experiments showed that L. minuta has generally a higher growth rate than L. minor. L. minuta outgrows the native species at all the nitrate concentrations tested and at all the Ca/Mg ratios and concentrations tested. Only at very low concentrations of phosphate did L. minor outgrow the alien species. When exposed to stressors, L. minor tolerated low temperatures best, while L. minuta tolerated best high aluminium and copper concentrations, high temperatures and drought stress. It was concluded that the commonly accepted believe that competitive species grow faster, but are less able to tolerate stress, is not always correct. The outdoor experiment showed that, in the summer months, A. filiculoides and L. minor outgrow the native L. minor, but the native species is the first one to re-start its growth after the winter in accordance with the tolerance to low temperatures observed under laboratory conditions. The outdoor experiment showed that the fastest growing and most competitive species is A. filiculoides, followed by L. minuta. Yet, field monitoring showed that these two species were not able to exclude the native species in the wild. Survival of winter conditions and/or re-colonisation, together with the invasibility, need to be considered to explain this apparent discrepancy

Competition between Lemna minuta, Lemna minor, and Azolla filiculoides. Growing fast or being steadfast?

A substantial number of Lemnaceae are invasive outside their natural distribution area. Lemna minuta is considered invasive in several European countries, where it can occur in the same habitat as invasive Azolla filiculoides and native Lemna minor. In this study the presence, abundance and growth rates of all three species were monitored across 24 natural ponds and in a series of mesocosms in order to explore the importance of species invasiveness and habitat invisibility. Field monitoring showed that the distribution of the three species of macrophytes is heterogeneous in space and time. However, the data show no association of nutrient or light levels with plant distribution. Indeed, using reciprocal transplanting experiments it was demonstrated that all species are able to grow in all ponds, even ponds where the species do not naturally occur. It is concluded that distribution of L. minor, L. minuta, and A. filiculoides is not limited by the prevailing physicochemical characteristics of the ponds during the summer period. Remarkably, in these experiments A. filiculoides displayed the highest RGR, and exerted a negative influence on growth rates and surface cover of L. minor and L. minuta. Despite such apparent invasiveness, A. filiculoides was relatively rare in the study area. Rather, the species most abundant was L. minor which has the lowest RGR under field conditions in summer. Therefore, this study shows that the invasiveness of the species during the summer months is not necessarily reflected in the actual distribution pattern in natural ponds. In fact, alien L. minuta and A. filiculoides are under-represented in the monitored area. It is concluded that the interaction of several factors, including growth under winter-conditions and/or dispersal after disturbances, is the major determinant of the abundance and heterogeneous distribution of L. minor, L. minuta, and A. filiculoides in the study area

Intra-varietal variability of Romanesco variety (Vitis vinifera L.)

Most historical sources that describe the presence of Romanesco variety in vine-growing areas of Lazio Region (Italy) highlighted the variability of morphological traits within the variety. This partly justifies the presence of different synonyms, true or presumed, reported by many authors for this grape variety. With the aim of analysing this variability, eight accessions related to the variety, collected in Lazio Region and grown in the DAFNE grape germplasm collection, have been characterized over five productive seasons. The ampelographic description was carried out using 50 OIV morphological descriptors and ampelometric analyses were carried out on mature leaves by SuperAmpelo software. The DNA of the different accessions, extracted from young leaves, was analyzed using 14 microsatellite loci. Furthermore, at harvest, the grapes of each accession were sampled to assess main compositive characteristics. Results showed differences among accessions on some ampelographic descriptors of the mature leaf, of the bunch, and on phenological stages. Microsatellite profiles allowed for classification of the accessions into three distinct groups. Qualitative analysis of the berry skin showed differences among accessions in the content of the main classes of phenolic compounds

Labels on seafood products in different European countries and their compliance to EU legislation

Funding Information: This study was funded by the European Regional Development Fund Interreg Atlantic Area, EAPA_87/2016 .Peer reviewedPublisher PD

Seafood labelling in different eu countries and their compliance to eu regulations

Poster.-- Aquaculture Europe 2021, October 4-7, Funchal-Madeira, PortugalN

Competition Between Lemna minuta, Lemna minor, and Azolla filiculoides. Growing Fast or Being Steadfast?

A substantial number of Lemnaceae are invasive outside their natural distribution area. Lemna minuta is considered invasive in several European countries, where it can occur in the same habitat as invasive Azolla filiculoides and native Lemna minor. In this study the presence, abundance and growth rates of all three species were monitored across 24 natural ponds and in a series of mesocosms in order to explore the importance of species invasiveness and habitat invisibility. Field monitoring showed that the distribution of the three species of macrophytes is heterogeneous in space and time. However, the data show no association of nutrient or light levels with plant distribution. Indeed, using reciprocal transplanting experiments it was demonstrated that all species are able to grow in all ponds, even ponds where the species do not naturally occur. It is concluded that distribution of L. minor, L. minuta, and A. filiculoides is not limited by the prevailing physicochemical characteristics of the ponds during the summer period. Remarkably, in these experiments A. filiculoides displayed the highest RGR, and exerted a negative influence on growth rates and surface cover of L. minor and L. minuta. Despite such apparent invasiveness, A. filiculoides was relatively rare in the study area. Rather, the species most abundant was L. minor which has the lowest RGR under field conditions in summer. Therefore, this study shows that the invasiveness of the species during the summer months is not necessarily reflected in the actual distribution pattern in natural ponds. In fact, alien L. minuta and A. filiculoides are under-represented in the monitored area. It is concluded that the interaction of several factors, including growth under winter-conditions and/or dispersal after disturbances, is the major determinant of the abundance and heterogeneous distribution of L. minor, L. minuta, and A. filiculoides in the study area

The invasive duckweed Lemna minuta Kunth displays a different light utilisation strategy than native Lemna minor Linnaeus

Lemna minuta Kunth is an invasive, alien duckweed that is present throughout much of Europe, where it competes with native congeneric Lemna minor Linnaeus. Previously, L. minuta was found to grow faster than L. minor. The aim of this study was to determine whether the rapid growth of invasive L. minuta is based on differential light utilisation. For this purpose, the growth performance of L. minuta was compared with that of L. minor under a range of different light intensities. Both physiological and morphological parameters were determined. L. minuta showed a higher Relative Growth Rate (RGR) than L. minor when grown under medium and high intensities. Further analysis showed that, at high light intensities, L. minuta has a higher Net Assimilation Rate (NAR), and displays more photochemical quenching (qP) and a higher quantum yield (Y(II)) than L. minor. In contrast under low light intensities L. minor displayed a marginally higher RGR, due to a greater Leaf Area Ratio (LAR), and higher chlorophyll content than L. minuta. The results indicate two distinct light utilisation strategies, and reveal that the invasive species L. minuta takes more advantage from high intensity light conditions. In turn, this may influence plant distribution and, consequently, ecosystem management by relevant authorities

Integrated Multitrophic Aquaculture; Analysing Contributions of Different Biological Compartments to Nutrient Removal in a Duckweed-Based Water Remediation System

Duckweed (Lemnaceae) can support the development of freshwater aquaculture if used as extractive species in Integrated MultiTrophic Aquaculture (IMTA) systems. These aquatic plants have the advantage of producing protein-rich biomass that has several potential uses. On the contrary, other biological compartments, such as microalgae and bacteria, present in the water and competing with duckweed for light and nutrients cannot be harvested easily from the water. Moreover, as phytoplankton cannot easily be harvested, nutrients are eventually re-released; hence, this compartment does not contribute to the overall water remediation process. In the present study, a mesocosm experiment was designed to quantify the portion of nutrients effectively removed by duckweed in a duckweed-based aquaculture wastewater remediation system. Three tanks were buried next to a pilot-scale IMTA system used for the production of rainbow trout and perch. The tanks received aquaculture effluents from the adjacent system, and 50% of their surface was covered by duckweed. Daily water analyses of samples at the inlet and outlet of the mesocosm allowed quantification of the amount of nutrients removed in total. The portion removed by duckweed was determined by examining the nutrient content in the initial and final biomass. The portion of nutrients removed by other compartments was similarly estimated. The results show that duckweed is responsible for the removal of 31% and 29% of N and P, respectively. Phytoplankton removed 33% and 38% of N and P, respectively, while the biofilm played no major role in nutrient removal. The remainder of the removed nutrients were probably assimilated by bacteria or sedimented. It is speculated that a higher initial duckweed density can limit phytoplankton growth and, therefore, increase the portion of nutrients removed by the duckweed compartment

The importance of the calcium-to-magnesium ratio for phytoremediation of dairy industry wastewater using the aquatic plant Lemna minor L.

Lemnaceae are being exploited to remediate a variety of different wastewaters. Our aim was to remediate dairy processing waste, which is produced in large amounts, and contains valuable plant nutrients, for example, nitrate, ammonium, phosphate and iron. However, initial trials failed to establish the growth of Lemna minor on this medium. A lack of growth can be due to a lack of essential plant nutrients, or the presence of phytotoxic ingredients. In this study we show that not just nutrient concentrations, but also the ratios between them can be important in facilitating growth. Lab-scale experiments in which L. minor were grown on 100 mL of synthetic dairy industry wastewater demonstrated that the skewed Ca:Mg ratio in synthetic wastewater is a key obstacle to good growth. Experiments showed that a ratio which favors magnesium over calcium negatively affects L. minor growth and photosynthetic yield, leading to RGRs as low as 0.05 day−1. A change in this ratio to favor calcium, through the addition of calcium sulfate, leads to RGRs of 0.2–0.3 day−1. Experiments lead us to conclude that a Ca:Mg ratio of 1:1.6 or greater is necessary for L. minor growth, and therefore phytoremediation of dairy industry processing wastewater

Clonal diversity amongst island populations of alien, invasive Lemna minuta kunth

Invasive alien species can negatively impact on newly colonised ecosystems. Thus, it is important to understand factors that facilitate invasiveness. Genetic diversity will enable a species to exploit a variety of environmental conditions. Yet, the process of dispersal to a new ecosystem will commonly create a genetic bottleneck and, hence, result in low diversity. Here we explored variability at genetic and morpho-physiological level of island of Ireland populations of alien, invasive Lemna minuta. A comparison of nine clones of L. minuta with nine clones of co-generic, native Lemna minor shows similar levels of genetic diversity across both species. Thus, the successful invasion of Ireland by L. minuta is associated with substantial, intraspecific diversity. It is hypothesised that increased biodiversity is due to repeated invasions from continental Europe, which occurred despite the geographic barriers separating the island from mainland Europe