Aquatic Vascular Plants Research Articles

Findings of Aquatic Vascular Plants on the Sakhalin Island

Investigations of South-western geobotanical district of Sakhalin Island, which is classified as a separate subzone of dark coniferous forests with an admixture of broad-leaved species and corresponds to Krillon floristic district, revealed a number of new aquatic vascular plant species for that area (Lemna turionifera, Myriophyllum verticillatum, Potamogeton gramineus, P. manchuriensis, Stuckenia pectinata, Utricularia minor, U. × ochroleuca). There is also a novelty for the South-Sakhalin lowland geobotanical district (Myriophyllum spicatum). All these taxa are known from other geobotanical districts of Sakhalin. The additions to the flora of the South-western district, which is well surveyed by botanists, indicate not floristic uniqueness of the subzone of dark coniferous forests with an admixture of broad-leaved species, but rather a poor knowledge of the Sakhalin Island aquatic flora.

Alien aquatic plants in Poland: Temporal and spatial distribution patterns and the effects of climate change

Distribution of alien aquatic plants in European freshwater ecosystems is still not fully recognized. Little is also known about the impact of climatic factors on the expansion of particular neophyte species in freshwater ecosystems. In this article, we present the first comprehensive assessment of the occurrence of non-native aquatic vascular plants in Poland (CE Europe), with a particular focus on: (1) inventory of the species, (2) temporal and spatial changes in their distribution, and (3) the climate impact on species occurrence and diversity. For this purpose, we collected both published and unpublished data on alien macrophytes occurrence in Poland covering past 70 years. In order to investigate the mechanism of alien aquatic plant expansion, climate data from 24 meteorological stations were analyzed. Redundancy analysis (RDA) was used to analyze the relationship between species composition and microclimate variables. In addition, Generalized Additive Model (GAM) was used to examine the response curves of neophyte species to temperature parameters.In total, we found records of 15 neophytes of alien aquatic plant taxa in Poland, including 14 species and collective taxon of Nymphaea cultivars. The most frequent was Elodea canadensis (over 25,000 records). Excluding this species, we counted more than 300 records of the occurrence of alien aquatic plants, of which three (E. nuttallii, Azolla filiculoides and Lemna turionifera) were the most abundant. Ten species occurred only in isolated sites. In addition, analyses showed a substantial increase in the number of the aquatic neophyte sites in the last 20 years that could be linked with the raised average monthly and yearly air temperatures in Poland.Our results showed a strong relationship between raised average temperatures in Poland and the spread of some species, e.g. Azolla filiculoides, while other species such as Elodea nuttallii and Lemna turionifera expanded irrespectively of this factor. The occurrence of some species (e.g. Vallisneria spiralis, Hygrophila polysperma) was exclusively associated to high thermally altered or thermally contaminated waters, and thus was limited to only a small part of the country. Our results confirm the major role of elevated temperatures (mean annual temperatures and minimum monthly temperatures) and thermally polluted freshwater ecosystems in the distribution of alien aquatic plants.

Fate of heavy metals in ecosystems of dam reservoirs: Transport, distribution and significance of the origin of organic matter

In this article, a multivariate analysis of the parameters determining the transport and fate of selected heavy metals in the water - bottom sediment interface was carried out. The studies were carried out in the summer season of 2019 at Nielisz Reservoir (southeastern Poland, Lublin Voivodeship).Finally, a previously unknown factor related to the quality of organic matter was identified. Autochthonous organic matter was shown to promote the accumulation of the studied heavy metals. To date, the significance of the origin of organic matter in the context of the transport and fate of heavy metals in retention reservoirs has rarely been reported in the scientific literature. More than that, this factor was not considered an important component in the process of heavy metal deposition in bottom sediments. However, it turns out that not only the quantity of organic matter, but also its quality plays an important role in the circulation of heavy metals in retention reservoir ecosystems. It was found that autochthonous organic matter promotes the accumulation of the studied heavy metals. It can be assumed that, in a sense, it plays the role of a catenary ("hub") controlling the fate of heavy metals in the water-sediment system. It has also been conjectured that, in a sense, OMS may reflect the potential for heavy metal assimilation by aquatic vascular plants (mainly of the C3 group). Plants with a photosynthetic pathway similar to the C3 group generally have a much lower enrichment in the 13C isotope (δ13C from −38‰ to −22‰). In our case, the lowest δ13C-TOCS value was −24.05‰, and the average for the whole reservoir was −21.53‰. In addition, it was observed that quantitative changes in the isotopic composition of total organic carbon δ13C-TOCS, corresponded with changes in the content of the heavy metals studied in entrapped sediments.

Database of aquatic macrophytes in Japanese lakes

AbstractMacrophytes, comprising aquatic vascular plants, bryophytes, and macroalgae, including charophytes, are crucial components of lake ecosystems. Their diversity affects ecosystem functions and services, and they are sensitive to environmental changes, making them effective indicators of lake health. Historical records of macrophyte species composition are essential for evaluating environmental changes and conservation goals. In this study, we compiled a comprehensive database of macrophytes, along with lake and survey information from the literature, providing a historical record of macrophyte biodiversity for lakes in Japan. This database enables the analysis of changes in the flora of Japanese lakes and fluctuations in species distribution, facilitating future monitoring. The complete dataset for this abstract published in the Data Article section of the journal is available in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2024-02.1/jalter-en.

Seasonality strongly affects short‐term C‐storage in coastal macrophyte communities

AbstractEcosystem functions provided by aquatic plants are context dependent and mediated by environmental conditions and plant growth form. This impedes our ability to predict the carbon (i.e., C) sink potential of multispecies coastal meadows characterized by marked seasonal succession of environmental conditions, causing a clear need to explore the distinct patterns of both C capture and release associated with seasonal succession of macrophyte growth forms and life‐history strategies in aquatic plant communities. We conducted four field surveys throughout 2022–2023 (i.e., October, March, June, and August), where we sampled six soft bottom locations dominated by aquatic vascular plants in the northern Baltic Sea. Temporal differences in biomass‐bound C stocks (i.e., structural elements and non‐structural carbohydrates) were linked to the plant production‐decomposition cycle and peaked when environmental conditions became increasingly permissive for growth and development (i.e., summer). Species identity influenced seasonal patterns of non‐structural carbohydrate concentrations in both leaf and rhizome tissue by shaping the timing of short‐term accumulation (i.e., photosynthesis) of C in plant tissue or release through respiration. Overall, our study illustrates that biomass‐bound C stocks were shaped by both seasonality and the variation of functional structure and life history strategies found within the vegetated seascapes. This highlights the importance of addressing both biodiversity and short‐term C dynamics and suggests that estimations of C budgets or stock assessments should be based on data incorporating the intra‐annual variation in C dynamics to fully comprehend the C sink potential of vegetated seascapes.

A functional perspective on the factors underpinning biomass-bound carbon stocks in coastal macrophyte communities

Coastal ecosystems have received international interest for their possible role in climate change mitigation, highlighting the importance of being able to assess and predict how changes in habitat distributions and their associated communities may impact the greenhouse gas sink potential of these vegetated seascapes. Importantly, the range and diversity of macrophytes within the vegetated seascape have different capacities to store C within their biomass and potentially sequester C depending on their functional trait characteristics. To bridge the present knowledge gaps in linking macrophyte traits to C storage in tissue, we (1) quantified biomass-bound C stocks within diverse macrophyte communities, separately for soft and hard bottom habitats and (2) explored the links between various traits of both vascular plants and macroalgae and their respective biomass-bound C stocks using structural equation modeling (SEM). We conducted a field survey where we sampled 6 soft bottom locations dominated by aquatic vascular plants and 6 hard bottom locations dominated by the brown algae Fucus vesiculosus in the Finnish archipelago. Macrophyte carbon stocks of hard bottom locations were an order of magnitude higher than those found in soft bottom locations. Biodiversity was associated with aquatic plant carbon stocks through mass ratio effects, highlighting that carbon stocks were positively influenced by the dominance of species with more acquisitive resource strategies, whereas age was the main driver of carbon in the mono-specific macroalgal communities. Overall, our results demonstrate that habitat type and dominating life-history strategies influenced the size of the organism-bound carbon stocks. Moreover, we showed the importance of accounting for the diversity of different traits to determine the drivers underpinning carbon storage in heterogenous seascapes composed of macrophyte communities with high functional diversity.

Efficient and rapid control of Eurasian watermilfoil (Myriophyllum spicatum) by combining benthic mats and hand pulling

AbstractEurasian watermilfoil (Myriophyllum spicatum L.) is an aquatic vascular plant that forms extensive dense beds in lakes. This invader competes with native plants, interferes with aquatic activities, and decreases riparian property values. In Canada, the use of aquatic herbicides is highly restricted. Environmental managers must therefore rely on physical methods such as hand pulling or benthic matting for control. Although these methods are not new, there has been little scientific investigation regarding their effectiveness and cost over multiple years. Benthic matting and hand pulling were used in Lac des Abénaquis (area: 1.2 km2) to control 3.6 ha of M. spicatum beds. Initiated by citizens in 2016, control procedures were scientifically studied in 2020 and 2021. Benthic fiberglass mats were deployed on dense M. spicatum patches for 10 wk. Isolated plants and patches <100 m2 were hand pulled by divers, and the harvested material surfaced via a suction hose or in hand-filled bags. By August 2021, all the M. spicatum patches had been eliminated, and only 560 widely scattered plants remained. Over the last 2 yr of control, hand pulling required 243 person-hours and removed 2,245 kg of biomass. The biomass brought to the surface was 2.4 times higher per person-hour with the suction system than with bags. The use of 1,000 m2 of benthic mats required 47 to 51 person-hours per summer season, including installation, removal, and maintenance. Intensive management (years 1 to 5) using benthic mats and hand pulling cost an estimated Can$185,000 (US$140,000) ha−1 of M. spicatum bed. Hand pulling of scattered individuals (years 6+), estimated at Can$20,000 (US$15,000) per summer, is essential to avoid reinfestation. An invasion of M. spicatum can successfully be managed in small lakes without herbicides, but control remains a costly and long-term endeavor.

Multi-approach inventory of aquatic vascular plants in Kyrgyzstan provides new data on biodiversity of Central Asia

Freshwater plants of Central Asian Mountains (a global biodiversity hotspot) remain poorly studied. We performed extensive field inventory of vascular plants in different types of waterbodies in northeastern Kyrgyzstan. By joint morphological and genetic analysis, we revealed a new, previously undetected, hybrid (Utricularia macrorhiza × U. vulgaris) and demonstrated that Stuckenia amblyphylla should not be treated as a separate species, being rather a lineage of S. filiformis. Besides these new data for global biodiversity, we report three new taxa for Central Asia (Lemna × japonica, Potamogeton berchtoldii × P. pusillus and Sparganium rothertii). We listed seven new species for Kyrgyzstan, that are not rare in Central Asia (Caulinia minor, Lemna gibba, Najas major, Potamogeton berchtoldii, P. nodosus, Spirodela polyrhiza, Zannichellia repens), and provided new data on distribution of nine species in the country. We conclude that focused multi-approach studies of aquatic vascular plants in Central Asia should be continued.

Aquatic flora of the high-mountain lakes in the southeastern part of the Chersky Ridge within the basin of the upper Kolyma River

We investigated several intermountain depressions in lakes with diverse flora of aquatic vascular plants in the southeastern part of the Chersky Range. The study area was located between 63–64° N and 147–148.5° E, at approximately 800–1200 m a.s.l. We identified 48 species and three hybrids.Among them, the families Potamogetonaceae (13 species and 1 hybrid) and Ranunculaceae (7 species) were characterized by the greatest diversity. For the first time, Stuckenia subretusa was found in the Magadan Region, which is the southernmost locality for this species. In an ultracontinental climate with an average annual air temperature of –13.1 °С, Arctophila fulva, Eleocharis acicularis, Hippuris vulgaris, Potamogeton alpinus, Ranunculus gmelinii, R. reptans and Sparganium hyperboreum are widespread. The species composition of aquatic plants is most diverse in small lakes at altitudes of 750–850 m a.s.l. in the plain interfluve, where the rarest species in the Kolyma River Basin are found. At altitudes above 850 m a.s.l. the most diverse species were found in the smallest lakes located near the large lakes. Obligate aquatic plants (80 %; 41 taxa; 30 hydrophytes and 11 hydrohygrophytes) dominated the flora of the mountain lakes. Only 20 % (10 species) of the flora were represented by plants of excessively moist coastal habitats. Among the 30 hydrophyte taxa 11 species grew up to 1050 m a.s.l. and 19 species grew at 950 m a.s.l. We identified four species that were protected at the regional level. Stuckenia pectinata is included in the Red Book of the Magadan Region, and Isoёtes asiatica, Nuphar pumila and Subularia aquatica are included in the Red Books of the Magadan Region and the Republic of Sakha (Yakutia).

The Kava River Basin (Northern Okhotsk Area) as a Hotspot of Aquatic Macrophyte Diversity in Northern Pacific

Aquatic macrophytes of the Kava River basin in northern Okhotsk area are represented by 4 species of macroalgae and 51 species and 4 hybrids of vascular plants. Flora of the Magadan Region was completed by 3 species and 3 hybrids: Aegagropilopsis moravica, Equisetum arvense × E. scirpoides, Elatine aff. triandra vel americana, Potamogeton × vepsicus, Sparganium chlorocarpum and S. chlorocarpum × S. gramineum. Almost all species of aquatic vascular plants protected in the Magadan Region (10 out of 11) are concentrated and abundant in the Kava River basin, 3 “red listed” species in the Khabarovsk Territory were also found in its basin and with a high abundance. Basing on floristic diversity, water bodies are grouped according to the similarity of environmental conditions, and not according to their geographical location. Almost all diversity of aquatic macrophytes is concentrated in lakes. The lake-river system of the Chukcha River, one of the major tributary of the Kava River, is distinguished here by the greatest diversity and concentration of rare taxa, because it is the most isolated from the cold sea winds. Rich aquatic flora and vegetation in the Kava River basin had emerged and are now sustained due to the special favorable microclimatic conditions of the closed valley of a large river, the existence of numerous water bodies of different ages and genesis with a wide variation in hydrological and hydrochemical parameters, the possibility of moving the propagules of aquatic plants along a well-developed lake-river network. The unique lake-river system of the Kava River requires increased attention and protection.

Interactions between Aquatic Plants and Cyanobacterial Blooms in Freshwater Reservoir Ecosystems

Climate change and nutrient pollution are echoed by worldwide increasing trends in the frequency, duration, and toxicity of cyanobacterial (blue-green algal) blooms. Therefore, searching for the best options to mitigate blooms is relevant and timely. Aquatic vascular plants offer a promising solution through biological control. In this study, we use reservoirs regularly affected by intensive blooms (the Kyiv and Kaniv Reservoirs of the Dnipro River, Ukraine) to investigate whether macrophytes may inhibit or reduce the massive development of cyanobacteria. Special attention was paid to plants with floating leaves and free-floating plants since data on their effects on cyanobacteria are controversial. On the basis of field and satellite observations, the spatial distribution of cyanobacterial blooms and aquatic macrophyte patches was assessed. Multispectral images captured by satellites Sentinel-2a (S2A) and Sentinel-2b (S2B) were used. In addition, based on data from field observations, a comparative analysis of phytoplankton and physical and chemical parameters between areas of the reservoirs overgrown and not overgrown by macrophytes was carried out. The obtained results indicate that in macrophyte patches phytoplankton structure differed from that observed in open waters. However, in areas of reservoirs dominated by floating-leaf plants or free-floating plants, a significant decrease in phytoplanktic or cyanobacterial biomass was not observed. This is most likely due to the fact that these macrophytes did not reduce the concentration of biogenic substances to a level that would limit cyanobacterial growth. On the contrary, intensive overgrowth of floating-leaf plants (in particular, Trapa natans) along the river sections of the reservoirs, as well as other factors, contributed to nitrogen and phosphorus enrichment. Therefore, in the face of relevant nutrient supply, these ecological groups of macrophytes (floating-leaf plants and free-floating plants) have not shown statistically significant effectiveness in controlling the process of cyanobacterial blooms in reservoir ecosystems.

Seasonal variation and provenance of organic matter in the surface sediments of the three gorges reservoir: Stable isotope analysis and implications for agricultural management

The construction of the Three Gorges Dam has altered the hydrology and increased the trapping of sediment in the reservoir. This has also changed the composition and export of particulate organic matter in the Yangtze River. To understand the seasonal variations and sources of organic matter in sediments, total organic carbon (TOC), total nitrogen (TN), δ13Corg and δ15N in surface sediment samples from the mainstream and tributaries of the Three Gorges Reservoir were measured in the summer (July) and winter (December) of 2017, respectively. The results showed that the concentrations of TOC and TN in the surface sediments of the Three Gorges Reservoir were 0.79 %–1.46 % and 0.07 %–0.13 %, respectively. The ranges of δ13Corg and δ15N were − 26.35 ‰ to−24.70 ‰ and 2.59 ‰ to 5.67 ‰, respectively. According to δ13Corg and the TOC/TN ratio, the source range of organic matter was determined, and the contributions of different organic matter sources were quantified using a Bayesian mixed model. The results showed that soil organic matter and river plankton were the main sources of surface sediment organic matter in summer, whereas soil organic matter and aquatic vascular plants were the main sources in winter. The source of organic matter is related to biological factors in summer, whereas it is mainly caused by hydrodynamic conditions in winter. The analysis of δ15N further reveals that there are obvious external pollutants in the Three Gorges Reservoir, mainly related to artificial nitrogen fertiliser and domestic sewage. This study highlights the influence that soil nitrogen loss may be an important reason for the impact of agricultural non-point source pollution in the reservoir area, showing seasonal differences which were mainly affected by rainfall in summer and controlled by impoundment in winter. Hence, fine nitrogen management is required to reduce pollution in the Three Gorges Reservoir.

Aquatic Vascular Plants in the Mires of the Volga Upland: Distribution, Occurrence, and Ecology

Aquatic Vascular Plants in the Mires of the Volga Upland: Distribution, Occurrence, and Ecology

Posidonia oceanica (L.) Delile: A Mediterranean seagrass with potential applications but regularly and erroneously referred to as an algal species

Posidonia oceanica (L.) Delile is one of the most abundant aquatic vascular higher plants in the Mediterranean Sea belonging to Posidoniaceas family. It is considered as a valuable natural source for multiple uses either for ecological functions or industrial applications. Nevertheless, this marine phanerogam is commonly confused with macroalgae, or seaweeds, known also as cryptogams. The present note intends to discuss the mis-use of the associated terminology of P. oceanica as algae in the scientific literature in order to avoid the widespread of this issue in the future. Thus, an extensive assessment of some important published woks has been conducted. This note will certainly allow the accurate nomenclature of this promising endemic species, which will continue its valorizations' ascension in several potential applications.

Aquatic vascular plants in the National рark «Shushensky bor» (Minusinsky steppe basin)

The studies of the aquatic vascular macrophytes flora of water bodies in the forest cluster of the National park «Shushensky Bor» and its vicinities located in the Minusinsky steppe basin in the south of the Krasnoyarsk territory are resulted. The list of species of vascular aquatic plants includes 99 taxa belonging to 54 genera and 33 families. Families Potamogetonaceae (2 genera, 13 species), Cyperaceae (5 genera, 12 species), Lentibulariaceae (1 genus, 6 species), Poaceae (6 genera, 6 species), Polygonaceae (2 genera, 6 species), Ranunculaceae (3 genera, 6 species) prevail in the spectrum. The ecological spectrum is represented by hydrophytes (true aquatic plants) including 35 taxa (33 species and 2 hybrids), helophytes - 12 species, hygrohelophytes - 18, hygrophytes - 33, hygromesophytes - 1. Rare species listed in the Red Data Book of the Krasnoyarsk region (2012) were found among hydrophytes - Nymphaea candida and N. tetragona. Interesting finds of aquatic plants of hybridogenic origin were made - Utricularia х japonica and Potamogeton х nitens.

Investigation of aquatic vascular flora at Sadullapur Upazila of Gaibandha District, Bangladesh

The present article focused on aquatic vascular plants diversity and their conservation status in natural and manmade wetlands habitats of Sadullapur Gaibandha. The study was conducted in between May 2019 to June 2020. A total of 52 aquatic plant species was recorded from Sadullapur Gaibandha in the present study. These are assigned to 35 genera under 30 families. For each species scientific name, local name, family, division, habit, habitat, use and status are provided. Ecological habitats analysis of aquatics shows variations. Among them, 37% species prefers to grow near the edge of water, 13% submerged, 11% as emergent, 11% as free floating and 28% as rooted floating in the aquatic habitat. In case of submerged species, they produce flowers on surface of the water. After pollination fruits remain under water up to maturation. Among them, 49% species used as fodder, 22% as medicinal, 4% as aquarium purpose, 9% as vegetable, 6% as edible, 10% as fish food in the study area. The population number of different aquatic plant species in habitats is not uniform. Overall analysis showed that 46% aquatic plant species in the study area found to be rare, 44% species found common and 10% species found as abundant. This status of aquatic plant species is very preliminary. Based on field observations and discussion with local people we are able to identify a good number of rare aquatic plants and also pointed some conservation measures for them in future. The investigation recorded a number of rare aquatic plant species from the study area. These are Trapa bispinosa (Singara), Nelumbo nucifera (Paddo), Nymphaea pubescens (Sada shapla), Oenanthe javanica (Panidhone), Nymphaea rubra (Lal shapla), Ottelia alismoides (Panikola), Enhydra fluctuans (Titidata) and Centrostachys aquatica (Thuash). Populations of such species in the wild are very rare because of local demand for the use. These species need to be cared for conservation.

Photosynthesis of Submerged and Surface Leaves of the Dwarf Water Lily (Nymphoides aquatica) Using PAM Fluorometry

Dwarf Water Lilies (Nymphoides aquatica (J.F. Gmel) Kuntze have floating and submerged leaves. Some submerged aquatic vascular plants have a form of CAM (Crassulacean Acid Metabolism) called Submerged Aquatic Macrophyte (SAM) metabolism. Blue-diode based PAM technology was used to measure the Photosynthetic Oxygen Evolution Rate (POER: 1O2 ≡ 4e– ). Optimum Irradiance (Eopt), maximum POER (POERmax) and quantum efficiency (α0) all vary on a diurnal cycle. The shape of the POER vs. E curves is different in seedling, submerged and surface leaves. Both Eopt and POERmax are very low in seedling leaves (Eopt ≈ 104 μmol photon m–2 s–1, PPFD; POERmax ≈ 4.95 µmol O2 g–1 Chl a s–1), intermediate in mature submerged leaves (Eopt ≈ 419 µmol photon m–2 s–1 PPFD, POERmax ≈ 38.1 µmol O2 g–1 Chl a s–1) and very high in surface leaves (Eopt ≈ 923 µmol photon m–2 s–1 PPFD, POERmax ≈ 76.1 µmol O2 g–1 Chl a s–1). Leaf titratable acid (C4 acid pool) is too small (≈20 to 50 mol H+ m–3) to support substantial SAM metabolism. Gross daily photosynthesis of surface leaves is ≈3.71 g C m–2 d–1 in full sun and as much as 1.4 gC m–2 d–1 in shaded submerged leaves. There is midday inhibition of photosynthesis.

Genetic legacy of ancient lands: Callitriche (Plantaginaceae) indicates Beringia and Paratethys Sea as diversification hotspots for aquatic vascular plants in Eurasia

The taxonomic status of endemic Callitriche taxa from western Beringia (C. subanceps) and the Lower Volga (C. fimbriata, C. transvolgensis) has been poorly studied. To investigate this question we compared endemic taxa with close Callitriche species. To achieve this goal we studied nuclear (ITS) and plastid (trnS-trnG, petL-psbE, trnH-psbA) genetic variation of almost 200 Callitriche samples and incorporated data on fruit shape variation and chromosome numbers. We found two genetically well-differentiated evolutionary lineages within C. heterophylla s.l. with rounded, wingless fruits, which diversification was likely associated with Beringia. One lineage occurs in western Beringia (known as C. subanceps), Greenland and northern North America, while another is confined to North America. Callitriche palustris, bearing winged, ovate fruits, is well-differentiated genetically from both C. heterophylla s.l. lineages. We refrain from any taxonomic decisions in C. heterophylla s.l. unless revision of full spectrum of diagnostic characters coupled with genetic studies with inclusion of abundant material from the both sides of the Bering Strait will be done. We demonstrated that Lower Volga endemics (C. fimbriata and C. transvolgensis) are separate species and their divergence might have been associated with dynamics of the Mediterranean, Black and Caspian seas. We point out importance of northern cryptic refugia (e.g. Lena River Delta) for cold-tolerant aquatic plants diversification.

Effects of Protein Level on the Production and Growth Performance of Juvenile Chinese Mitten Crab (Eriocheir sinensis) and Environmental Parameters in Paddy Fields

Rice–crab co-culture systems represent integrated agriculture–aquaculture systems developed in China over the last 30 years. The rice–crab co-culture area comprised approximately 1.386 × 105 hm2 in 2019. However, there is no specific feed designed for Chinese mitten crab (Eriocheir sinensis) cultured in this system until now. In this study, we investigated feed formulae for the nutritional requirements of Chinese mitten crab in this mode. The control group was not fed with any artificial feed (Co), and the experimental groups were fed with three different feeds of 15% (T15), 30% (T30), or 45% (T45) protein content, respectively. Growth performance variations in E. sinensis were investigated along with water quality, phytoplankton, zooplankton, aquatic vascular plants, and benthic animals in the paddy fields to determine the effect of crabs and their diet on the paddy ecosystem. Dietary protein levels had no significant effect on water quality. The biomass and species of phytoplankton, zooplankton, aquatic vascular plants, and zoobenthos in the paddy field were affected by crabs and their diet. Morphological parameters of crabs were significantly more pronounced in the high-protein group than in the other groups. However, the T45 diet negatively affected production by increasing feed costs, causing precocious puberty and inducing water eutrophication. In conclusion, adding a 15% protein compound feed can meet the nutritional needs of crabs, reduce culture costs, and improve water quality. The discharged water had low ammonia nitrogen and nitrite content and no eutrophication occurred, so the water could be recycled. These findings provide a scientific reference for supporting rice and fish co-cultivation.

Potential Use of Aquatic Vascular Plants to Control Cyanobacterial Blooms: A Review

Intense “blooming” of cyanobacteria (blue-green algae) caused by eutrophication and climate change poses a serious threat to freshwater ecosystems and drinking water safety. Preventing the proliferation of cyanobacteria and reducing water nutrient load is a priority for the restoration of eutrophic water bodies. Aquatic plants play an important role in the function and structure of aquatic ecosystems, affecting the physiochemistry of the water and bottom sediments, primary production, and biotic interactions that support a balanced ecosystem. This review examines the inhibitory effect of aquatic vascular plants on harmful blooms of cyanobacteria. Aquatic plants are able to successfully inhibit the growth of cyanobacteria through various mechanisms, including by reducing nutrient and light availability, creating favorable conditions for the development of herbivorous zooplankton, and releasing allelopathic active substances (allelochemicals) with algicidal effect. Allelopathy is species-specific and therefore acts as one of the key mechanisms by which the development of cyanobacterial populations in aquatic ecosystems is regulated. However, allelopathic activity of aquatic vascular plants depends on various factors (species characteristics of aquatic plants, area, and density of overgrowth of water bodies, physiochemical properties of allelopathically active substances, hydrological and hydrochemical regimes, temperature, light intensity, etc.), which may regulate the impact of allelochemicals on algal communities. The paper also discusses some problematic aspects of using fast-growing species of aquatic vascular plants to control cyanobacterial blooms.