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 Aquatic EcologyJournal Prestige (SJR): 0.656 Citation Impact (citeScore): 2Number of Followers: 42      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1573-5125 - ISSN (Online) 1386-2588 Published by Springer-Verlag  [2467 journals]
• Effect of alkalinity and light intensity on the growth of the freshwater
sponge Ephydatia fluviatilis (Porifera: Spongillidae)

Abstract: Abstract The adaptation of sponges to freshwater environments was a major event in the evolutionary history of this clade. The transition from a marine environment to freshwater ecosystems entailed a great number of adaptations to more unstable habitats, such as the ability to form resistance gemmules as a defense mechanism against environmental adversity. However, data on the parameters that modulate hatching and growth of these animals are scarce. In the present study, the growth response capacity of Ephydatia fluviatilis (Porifera: Spongillidae) has been evaluated in relation to both water alkalinity and light intensity. The results obtained revealed a positive association between the growth capacity of this freshwater sponge and high alkalinity values. On the other hand, exposure to light, regardless of its intensity, affected the development and distribution of the symbionts, which in turn, corresponds to a higher growth rate of the sponge. The obtained data suggest an explanation for the greater distribution of this species in alkaline environments. The results of this work also shed light on the importance of the symbiosis phenomenon in E. fluviatilis.
PubDate: 2023-03-20

• Biomonitoring of pesticides in agricultural river catchments: a case study
from two river catchments in tropical Sri Lanka

Abstract: Abstract Monitoring of pesticide pollution in aquatic systems is a complex process and often constrained by high costs and methodical complexities associated with pesticide measurements in many regions of the world. A trait-based Species at Risk (SPEAR) biomonitoring approach has been conducted to test the responsiveness of the SPEAR_pesticides index to pesticide effects in two tropical river catchments in Sri Lanka. The effects of pesticide toxicity (TU(D.magna)), water quality parameters, channel quality (CQI), and landuse on SPEAR pesticides index and other biotic indices, i.e., family richness of macroinvertebrates (FR) and %EPT (Ephemeroptera, Plecoptera, and Trichoptera) taxa in streams were tested using stepwise multiple linear regression analysis approaches. The analyses revealed that the SPEAR_pesticides index and FR respond favorably to the TU(D.magna) and CQI (p < 0.05). % EPT did not significantly respond to any of the measured instream variables. The catchment scale agricultural activities negatively affected the SPEAR_pesticides and FR, while riparian forest cover acted to improve both indices. The findings of the study suggest the possibility of using SPEAR_pesticides for pesticide impacts assessment in tropical regions.
PubDate: 2023-03-18

• Changes in nutrient concentration and water level affect the microbial
loop: a 6-month mesocosm experiment

Abstract: Abstract Eutrophication and lake depth are of key importance in structuring lake ecosystems. To elucidate the effect of contrasting nutrient concentrations and water levels on the microbial community in fully mixed shallow lakes, we manipulated water depth and nutrients in a lake mesocosm experiment in north temperate Estonia and followed the microbial community dynamics over a 6-month period. The experiment was carried out in Lake Võrtsjärv—a large, shallow eutrophic lake. We used two nutrient levels crossed with two water depths, each represented by four replicates. We found treatment effects on the microbial food web structure, with nutrients having a positive and water depth a negative effect on the biomasses of bacterial and heterotrophic nanoflagellates (HNF) (RM-ANOVA, p < 0.05). Nutrients affected positively and depth negatively the mean size of individual HNF and ciliate cells (RM-ANOVA; p < 0.05). The interactions of depth and nutrients affected positively the biomass of bacterivorous and bacteri-herbivorous ciliates and negatively the biomass of predaceous ciliates (RM-ANOVA; p < 0.05). Bacterivorous ciliates had lowest biomass in shallow and nutrient-rich mesocosms, whilst predaceous ciliates had highest biomass here, influencing trophic interactions in the microbial loop. Overall, increased nutrient concentrations and decreased water level resulted in an enhanced bacterial biomass and a decrease in their main grazers. These differences appeared to reflect distinctive regulation mechanisms inside the protozoan community and in the trophic interactions in the microbial loop community.
PubDate: 2023-03-16

• Beneath the surface: spatial and temporal trends in water quality and its
impacts on algal community composition in the Albemarle Sound, North
Carolina

Abstract: Abstract Urban and agricultural expansion and intensification pose a critical threat to water quality and aquatic ecosystems. Increased nutrient loading into waterways combined with warming temperatures due to climate change have increased eutrophication and algal blooms. The relationship between land use, nutrient availability, and algal growth can vary dramatically across space and time, but few studies have captured this variation. The goal of this research is to assess water quality across time and disparate land uses, and its influence on algal community composition in the Albemarle Sound, a brackish water estuary in North Carolina. We collected water quality data from 21 sites across the sound, visiting six sites in Chowan County biweekly and 15 other sites twice between June and August 2020. Water samples from each site were tested for nitrate, phosphate, ammonia, bicarbonate, and total phosphorus (TP). Preserved algal samples from the six Chowan County sites were enumerated under a microscope to estimate genus richness and biomass. In the Chowan County sites, phosphorus increased and nitrate decreased over the course of the summer. Across all sites, TP increased with development and agricultural land use. These results suggest that sources of nitrogen and phosphorus in the sound differ. Algal richness increased with nitrate concentration and decreased with precipitation while biomass increased with water temperature. Our results indicate that climate change impacts, particularly increasing temperatures and extreme precipitation, influence how land use, water quality, and algal community composition interact. These data demonstrate the co-benefits of mitigating climate change in developing management strategies to reduce algal blooms.
PubDate: 2023-03-15

• Diversity and seasonal variation of the molluscan community associated
with the seagrass Halodule wrightii in a marine protected area in the
southern Gulf of California

Abstract: Abstract The structural complexity of Halodule wrightii enhances the abundance and diversity of mollusks in the marine protected area of Bahía Balandra, in the southern Gulf of California. Marine mollusks are considered ecosystem engineers because they create, modify, and maintain habitats. Taxonomical and functional analyses of the mollusk community were carried out from May 2016 to 2017. The total abundance in all sampled periods was 7284 individuals and comprised 52 families, 69 genera, and 89 species. The Gastropoda class showed the highest number of species (61 species, 68.53%), followed by Bivalvia (24 species, 26.96%) and Scaphopoda (4 species, 4.49%). The highest density of mollusks was in the summer of 2016 (ca. 6500 ind. m−2), while the highest richness was found in spring 2017 (60 species). Five trophic levels were identified. All trophic groups were present in all the seasons with carnivores showing the highest species richness and herbivores the highest abundance, followed by filter-feeders. A positive and moderate relationship between the total biomass of seagrass and gastropod richness was found, while the relationship between gastropod abundance and seagrass biomass was negative. Halodule wrightii in the Gulf of California represents a unique niche that supports a high mollusk biodiversity and offers great variability of resources for this group. Halodule wrightii represents a suitable habitat for reproduction, metamorphosis, nursery, refuge, and feeding for mollusks. Finally, the functional group concept was applied to evaluate the ecosystem seagrass health of Bahía Balandra resulting in a moderate score.
PubDate: 2023-03-13

• Fish abundance estimation from multi-beam sonar by improved MCNN

Abstract: Abstract Aquatic products provide essential food and nutrients to humans, the abundance of fish is used in many aspects of aquaculture management, and it also undertakes a lot of tasks in the process of aquaculture, so it is a crucial link. This study introduces an automated method for estimating fish abundance in sonar images based on the modified MCNN (multi-column convolutional neural network), named FS-MCNN. We also proposed the multi-dilation rate fusion loss, which will improve the accuracy and robustness of the model. This method will improve the impact of low pixels in sonar images and blurry edges of target objects in sonar images. It further decreases the RMSE by 14.22% and the MAE by 11.83%, and the final accuracy is 92.83%. This study estimates fish abundance through imaging sonar, which will be able to reduce the effect of light and the complex environment, and it will also contribute to increase labor productivity, reduce the feed waste and enhance the level of information technology in aquaculture or fisheries.
PubDate: 2023-03-08

• Dynamic responses of root vigor, lipid peroxidation and antioxidant
enzymes in Artemisia selengensis to long-term drought and re-watering

Abstract: Abstract Artemisia selengensis is a typical wetland plant with valuable nutritional and medical purposes, and its growth and field distribution is highly dependent on water conditions. However, wetland hydrology is becoming more complex due to global climate change, and the future response of A. selengensis to water deficits and rehydration is uncertain. We here conducted simulations to investigate physiological variations in A. selengensis in response to varying degree of soil moisture (85–90%, 60–65%, 45–50%, and 30–35%) and re-watering. Results show that drought boosted root vigor and increased water and soil nutrient absorption in A. selengensis. As drought conditions progressed, the superoxide anion ( $${\text{O}}_{2}^{ - }$$ ) and malondialdehyde content significantly increased. This led to increased activity of antioxidant enzymes, which significantly inhibited $${\text{O}}_{2}^{ - }$$ content. Root vigor and peroxidase (POD) activity were fully recovered after rehydration. The $${\text{O}}_{2}^{ - }$$ and MDA content, and catalase (CAT) activity also fully recovered under moderate and mild drought, although full recovery can take longer under severe drought. Superoxide dismutase (SOD) activity decreased significantly after rehydration, but SOD activity in drought conditions has not yet recovered to the control level. A. selengensis is drought tolerant due to its high root vigor and the regulation of antioxidant enzyme system. Our results may provide guidance for the future population dynamics of wetland ecosystems under climate change.
PubDate: 2023-03-01

• Using macroinvertebrate functional traits to reveal ecological conditions
of two streams in Southwest Nigeria—a case study

Abstract: Abstract Understanding functional processes of aquatic bodies provides alternative means of assessing aquatic ecosystem health and identifying sites in urgent need of conservation or restoration. In this study, aquatic macroinvertebrates were used to assess the ecosystem health of a protected headwater stream (Olumirin Stream) and an unprotected middle-sized stream (Opa Stream) in Southwest Nigeria. Macroinvertebrate samples were collected between May 2019 and January 2022 and assessed for their taxonomic and functional diversity. A total of 51 macroinvertebrate species were recorded in Olumirin Stream, while a total of 35 species were recorded for Opa Stream. A significantly higher species richness (p < 0.001), Ephemeroptera-Plecoptera-Trichoptera (EPT) richness (p < 0.0001) and EPT abundance (p < 0.0001) were recorded in Olumirin Stream. While the Simpson Index (1 − D) showed higher diversity (p > 0.05) in Opa Stream, the Shannon–Wiener Index (H) indicated a significantly higher diversity (p < 0.05) in Olumirin Stream. Also, a total of six functional feeding guilds (FFGs) were recorded in the Olumirin Stream, namely predators, scrapers, shredders, collector-gatherers (CGs), collector-filterers (CFs) and piercer-herbivores (PHs). Predators dominated the fauna of both streams, while CGs and PHs were not recorded in the Opa Stream. The FFG-based channel stability index reflected a generally stable substrate in Opa stream. The production/respiration ratio (P/R) revealed the autotrophic and heterotrophic states of Opa and Olumirin Streams, respectively, with a significant difference (p < 0.05) between both streams. The P/R ratio (0.75) of the Olumirin Stream clearly indicates that its biological productivity is being driven by allochthonous organic matter of its riparian forest, while that of the Opa Stream is being driven largely by autochthonous organic matter. As a result, a dual approach of riparian forest and freshwater system protection is advocated for the sustainability of freshwater biodiversity in particular.
PubDate: 2023-03-01

• The temporal and spatial variation in morphospecies, size and viability of
Microcystis colonies in Lake Taihu

Abstract: Abstract Microcystis has been the dominant bloom-forming cyanobacterial population in Lake Taihu over the past two decades. To illustrate the temporal and spatial variation in the main colony characteristics for Microcystis and their key environmental factors in Lake Taihu, an annual investigation of the size, morphospecies and viability (the viable cell rate) of Microcystis colonies was performed in this study from 2020 to 2021. The average colony diameter ranged from 81.12 to 499.54 μm at all sites during this investigation. The average colony diameter of the whole lake in spring and in late autumn to early winter was higher than that in other times. Microcystis flos-quae, Microcystis aeruginosa, Microcystis novacekii and Microcystis wesenbergii were the main dominant morphotypes, which was mainly affected by pH, TDP and temperature. Although no significant correlation was found between colony viability and environmental factors, the temporal difference in colony viability was remarkable. Colony viability in autumn (mainly October and November), spring (March and April), and July was lower than that in other times.
PubDate: 2023-03-01

• The energetic cost of facing cyanotoxins: a case study on Daphnia magna

Abstract: Abstract Under the effects of global change, toxic cyanobacterial proliferations increase and subsequently threaten freshwater ecosystems and the services they provide. Zooplankton consumers, a key trophic level of freshwater ecosystems, are particularly impaired by cyanotoxins, but populations regularly exposed to cyanobacteria can develop tolerance against toxins. While the physiological processes involved in this tolerance have been extensively studied, their consequences for consumers’ energetics remain poorly explored, impeding predictions of energy flow from zooplankton up to higher trophic levels. Here, we explored the metabolic response of Daphnia magna exposed to toxic and non-toxic strains of cyanobacteria to define the energy dedicated to cyanotoxins resistance mechanisms. We showed that resting metabolic rate (RMR) of individuals exposed to toxins increased by up to 60%, reflecting the energy requirement involved by cyanotoxin resistance processes. By quantifying the energy dedicated to resistance mechanisms, RMR constitutes an interesting metric to estimate overall capacity of individual zooplankters to actively handle cyanotoxins. Moreover, RMR responds more promptly to cyanotoxins than growth thus being adequate to assess short-term cyanotoxins constraints (< 72 h). Overall, we showed that cyanotoxins resistance constitutes an energy leak in freshwater ecosystems. Quantifying this leak of energy may help anticipate alterations of energy flow within food web in response to cyanobacterial proliferation and, ultimately, enhance our predictions of freshwater ecosystem structure and functions in a context of global change.
PubDate: 2023-03-01

• Effects of rice–crayfish co-culture on ammonia-oxidizing microbial
abundance and community structure

Abstract: Abstract Ammonia oxidation microorganism (AOM) is a key aspect of nutrient recycling in aquaculture sediments. Recently, rice–fish co-culture (symbiosis) has been paid more and more attention to the restoration of water and sediment quality in intensive aquaculture. Nevertheless, there are few studies on the effect of rice–fish co-culture on AOM in the sediments. Here, a field experiment was used to determine differences in abundance, community structure of ammonia-oxidizing bacteria (AOB) along with ammonia-oxidizing archaea (AOA) in surface sediments (0–10 cm) in the paddy field (with ridge of 80 cm high, similar to shallow pond) for co-culture of japonica rice and crayfish (Procambarus clarkii) (JR-C), co-culture of indica rice and crayfish (IR-C), and crayfish monoculture (CM). The results showed that AOA were higher abundance, and diversity than AOB in the three modes of crayfish farming; AOA and AOB communities were dominated by Nitrososphaera and Nitrosospira clusters, respectively, with an average relative abundance of 97.86% and 93.77%; among the three modes, IR-C remarkably lowered α-diversity of AOA and AOB. Compared to CM, relative abundance of the Nitrosospira cluster in IR-C and JR-C was significantly increased, and the abundance of amoA genes of AOA in JR-C was remarkably higher (P < 0.05). Redundancy analysis (RDA) and spearman’s correlation analysis showed that AOB community structure and abundances of AOA were significantly correlated with sediment pH, which indicated that sediment pH dominantly controlled the AOM.
PubDate: 2023-03-01

• Testing whether reducing brown trout biomass in peatland lakes increases
macro-invertebrate biomass and invertivorous waterbird occurrence

Abstract: Abstract Waterbirds and fish sometimes compete for macro-invertebrate prey. In Scotland, the invertivorous waterbird, the common scoter Melanitta nigra, breeds at oligotrophic lakes with few brown trout Salmo trutta. This study tested whether reducing trout biomass favours this and other invertivorous waterbirds. The study took place in Scotland’s Flow Country, where brown trout occur widely, attracting recreational anglers, though angling has declined. At four small lakes, over 7 years, trout were reduced using 25 m2 exclosures, and re-introducing traditional angling (including fish removal). Trout, macro-invertebrates and waterbirds were monitored. After angling re-introduction, trout biomass density declined by 56% (95% CLs 13–78%), but there was little lake-level change in combined macro-invertebrate biomass. However, within exclosures, macro-invertebrate biomass increased 4.7-fold (CLs 1.6–14). Analysing invertebrates in eight different groups showed lake-level increases, following angling re-introduction, for two groups (freshwater shrimps Gammarus; water-surface invertebrates). Gammarus showed the strongest response, increasing sixfold (CLs 2.2–11.6). A combined analysis was performed for the commonest invertivorous waterbirds: common scoter, mallard Anas platyrhynchos, teal A. crecca, greenshank Tringa nebularia and dunlin Calidris alpina. After angling effort increased, occurrence of these species changed little initially, but rose later: 4 years after angling began, odds of occurrence had increased 4.9-fold (CLs 2.2–11). This study supports reducing trout biomass in peatland lakes by encouraging traditional angling, to increase some macro-invertebrate groups and usage by invertivorous waterbirds. Further work should test this across more lakes alongside work investigating the origins (native or stocked) of brown trout populations in the Flow Country.
PubDate: 2023-02-14

• Temporal variation in diversity, abundance and size class structure of
planktonic copepods from a tropical estuary

Abstract: Abstract A study on the community structure of planktonic copepods was carried out in the down stretch of Ashtamudi estuary (AE) for a period of two years (2018 to 2019). The copepod community composed of a total of 53 species under 31 genera belonging to 20 Families during the study period. Thirty Nine species of Calanoids, 9 species of Cyclopoids and 6 species of Harpacticoids were recorded from the AE. Of the total 20 families recorded during the study, 17 were noticed during pre-monsoon (PrM), 16 during post-monsoon (PsM), and 13 during monsoon (Mn) periods. Family Paracalanidae constitute > 50% irrespective of seasons followed by Acartiidae (18%), Oithonidae (9%), and Pseudodiaptomidae (4%). Family Pontellidae (11) and Acartiidae (9) represented the maximum number of species followed by Centropagidae (4), Pseudodiaptomidae (3), and Paracalanidae (3). The species Bestiolina similis belonging to the family Paracalanidae dominated throughout the study (~ 75%). The species such as Acartia plumosa, Acartia bowmani, Pseudodiaptomus serricaudatus, Paracalanus aculeutus, Dioithona rigida, and Oithona brevicornis were also recorded with higher abundance from the estuary. Copepods were grouped into 200–300 µm (smallest), 300–500 µm (Small), 500–1000 µm (Medium), and > 1000 µm (Large) size classes. Significant seasonal variation (p < 0.05) was observed in the size class structure of copepods in terms of its abundance and diversity during the study. Noticeably higher abundance was observed in the smallest category whereas relatively higher diversity was observed in the medium size category (H′ = 3.26). The study also discusses the habitat and feeding pattern of copepod species.
PubDate: 2023-02-13

• Pasture areas reduce the abundance and trophic niche width, but not the
body condition of the Amazonian whale catfish

Abstract: Abstract Land use changes modify aquatic ecosystems by changing their physical structure and biodiversity and generally reduce riparian vegetation, increase erosion of the margins, and negatively affect habitat-specialist species. Nonetheless, agricultural activities with different intensities affect those systems in the Neotropical region differently. For example, pastures drastically reduce the riparian vegetation alongside streams compared to oil palm monocultures. In turn, the riparian vegetation in oil palm monocultures supports the input of allochthonous materials into the stream, which serves as habitat or trophic resources to aquatic organisms. Herein, we test how different land uses (mature forest, pasture, and oil palm monoculture) in Eastern Amazon affect the abundance, diet, and condition factor of the whale catfish Helogenes marmoratus, an organism specialized in using floating or submerged debris as habitat. Pasture streams displayed a reduced abundance of H. marmoratus compared to those within forest and oil palm areas. In addition, the diet of the individuals captured in the pasture streams differed and included fewer items than the diet of the remaining areas. Nonetheless, these dietary differences were not related to any changes in the body condition of the individuals. Our results highlight that different types of land use have different effects on a habitat-specialist Neotropical fish and that pastures might have more marked effects by reducing their local abundance and trophic interactions with different prey.
PubDate: 2023-02-03

• Correction: Community structure and diversity of five groups of
zooplankton in the Perdido region of the Gulf of Mexico using DNA
metabarcoding

PubDate: 2023-01-31

• Effects of experimental sediment resuspension on protozooplankton grazing
activity: implication for the planktonic food web structure

Abstract: Abstract The effects of sediment elutriate, prepared from a sediment resuspension simulation process, on the growth of bacterioplankton and of different sized phytoplankton as well as on their grazing by protozooplankton were investigated in Mediterranean coastal ecosystems during spring phytoplankton bloom. In parallel, the response of bacterioplankton, phytoplankton and protozooplankton to sediment elutriate enrichment was assessed in microcosm experiments. Elutriate addition provoked a high enrichment in nutriments of the overlying water, particularly in ammonium, dissolved organic matter but also in trace metal elements and herbicides. Overall, elutriate addition significantly increased the biomass of bacterioplankton and of total phytoplankton, but the phytoplankton size fractions responded differently to elutriate enrichment. The picophytoplankton showed a significant strong enhancement in both growth and production rates, relatively to control, while these rates significantly decreased for nano- and microphytoplankton. Accordingly, the phytoplankton size structure shifted in elutriate microcosm toward a dominance of the picophytoplankton concomitant with a significant reduction in larger size fractions. The elutriate addition caused also a clear shift in the taxonomic composition of protozooplankton, associated with a significant modification of its functional diversity, with the dominance of pico-sized cell consumers (such as aloricate ciliates, heterotrophic nanoflagellates and mixotrophic dinoflagellates) in the detriment of grazers of nano- and microphytoplankton (such as heterotrophic dinoflagellate). The protozooplankton grazing on small prey (bacterioplankton and picophytoplankton) increased, while feeding on nano- and micro-sized phytoplankton decreased after elutriate addition. These results have implication for the carbon transfer pathway, which could change from an herbivorous food web to a microbial food web, influencing so the exportation of biogenic carbon through the other trophic compartments.
PubDate: 2023-01-10
DOI: 10.1007/s10452-022-09998-y

• Community structure and diversity of five groups of zooplankton in the
Perdido region of the Gulf of Mexico using DNA metabarcoding

Abstract: Abstract The evaluation of biodiversity is a primary concern for natural sciences and society, including marine ecosystems. Zooplankton plays a crucial role in marine ecosystems, transferring energy between trophic levels and participating in carbon and nutrient cycling. Zooplankton communities respond to changes in environmental conditions in complex ways and are highly susceptible to anthropogenic impacts, including climate change. However, the study of their diversity relative to environmental conditions has been hindered by their extremely high taxonomic diversity, which requires a high level of specialization for the morphological identification of specific taxa. We used metabarcoding to evaluate the relationship between zooplankton diversity and oceanic conditions along two transects in the Perdido region of the northwestern Gulf of Mexico during the summer and fall of 2016. This area has active oil production and ongoing exploratory wells. We focused on five zooplankton groups: Mollusca, Calanoida, Non-Calanoid copepods, Decapoda, and Amphipoda. We found that the studied groups had different levels of diversity that varied among sampling stations and seasons, and the taxonomic composition had larger differences among stations than between seasons. We found that environmental variables may have influenced the presence of zooplanktonic groups; however, we conclude that it is not possible to generalize deterministic factors that influence zooplankton diversity and that both the spatial and temporal scales are needed to take into account to determine the factors that shape such diversity.
PubDate: 2023-01-09
DOI: 10.1007/s10452-022-10002-w

• Effects of anthropogenic activities on scavenger communities in freshwater
riparian zones of eastern Ontario, Canada

Abstract: Abstract Carrion as a food source and the role of scavengers both contribute to ecosystem connections, services, and food webs. Historically overlooked, there are paucities in the literature examining scavenging ecology and it remains unknown how anthropogenic activities such as riparian shoreline development impact scavengers. The objective of this study was to evaluate the effect of human disturbance on freshwater riparian zone scavenger communities and their activity. Using bluegill sunfish (Lepomis macrochirus) carcasses as carrion bait and trail cameras, we conducted a field experiment on Big Rideau Lake, Ontario, Canada, and contrasted developed (impact) and undeveloped (control) sites. We found that it took a similar amount of time for scavengers to locate and consume the carcass regardless of degree of development. Additionally, we determined that the composition of scavenger communities varied across impact and control sites, although this difference was not significant. Using generalized linear mixed modeling to investigate scavenging (binary), we found that the top models included total length of carcass, and distance to closest development, respectively. Further, there was a positive relationship between scavenging and both the distance to closest to development and the body size of bluegill sunfish (i.e., further distance to development and larger bluegill were more likely to be scavenged, respectively). Our results suggest that anthropogenic activities are likely imparting a negative effect on the scavenging community within freshwater riparian zones; however, the scavenging community may be able to offset the negative impacts through flexible feeding strategies.
PubDate: 2022-12-30
DOI: 10.1007/s10452-022-09993-3

• Response of the cellular components to environmental factors indicates
limiting factors of Microcystis in Lake Taihu

Abstract: Abstract Studying the influence of environmental factors on the growth and physiological state of cyanobacteria is an important basis for understanding the formation of cyanobacteria content. This study selected Microcystis aeruginosa as an example, using algal pigment and fatty acid composition to reflect the physiological state of Microcystis, and analyzed the effects of environmental changes on the basic physiological indicators of Microcystis cells. The results showed that an increase in light strength caused the ratio of Chlorophyll a to proteins to decrease and then increase, but has little effect on fatty acids. Increasing the temperature caused Microcystis cells to increase photosynthesis pigments and polysaccharides to proteins ratio and caused fatty acid Palmitic acid C16:0 to decrease and then increase, as opposed to linoleic acid γ-C18:3. When the N:P ratio was 9.4, an increase in N concentration caused the Chlorophyll a to PR ratio to increase, and PS, TOC, β-carotene and zeaxanthin to PR ratio decrease. At P = 1.7 mg L−1, an increase N:P ratio promoted photosynthetic pigmentation of algae, which increased the PS to PR ratio. During autumn and winter, the fatty acids of Lake Taihu Microcystis cells were mostly C16:0 and C18:1, of which C16:0 changed most significantly during the winter period, showing a trend of decreasing first and then increasing later. Cluster analysis and the comparison of laboratory data found that the limiting factors affecting the growth of Lake Taihu Microcystis during this period were mainly temperature and nitrogen concentrations.
PubDate: 2022-12-28
DOI: 10.1007/s10452-022-09997-z

• Community and population impacts of an introduced meiofauna (Nippoleucon
hinumensis) upon an intertidal infaunal community and its closest endemic
analog (Cumella vulgaris)

Abstract: Abstract Introduced species may be one of the penultimate threats facing natural systems in the Anthropocene. Unfortunately, some taxa, such as meiofauna (organisms that pass through a 1 mm mesh but are retained by a 45 μm mesh), are so challenging to study that the presence and impact of introduced meiofauna often goes undetected. Further, the impacts of introduced species are seldom placed into context with other structuring variables. Therefore, we used infaunal invertebrate communities of northern British Columbia, Canada, to quantify potential impacts of the introduced Cumacea Nippoleucon hinumensis upon the infaunal community and its closest endemic analog, Cumella vulgaris. We also compared the relative importance of this introduced species to other top-down (predation), bottom-up (competition), middle-out (predation/competition), and abiotic (tolerance) variables in structuring the infaunal community. We identified a significant negative correlation between N. hinumensis and C. vulgaris, suggesting that when placed in context with other structuring factors, the introduced species may have a minor, but detectable impact upon C. vulgaris populations. However, no relationship was observed between N. hinumensis and the infaunal community. The lack of a community-wide effect is potentially the result of the similarity between N. hinumensis and C. vulgaris life history strategies, enabling the introduced species to effectively replace C. vulgaris in the food web. As such, N. hinumensis may be best described as an invasive species, and not as merely non-native. Furthermore, the analytical techniques used here can be applied to other ecological systems to quantify and compare the impact of introduced species against other structuring forces.
PubDate: 2022-12-05
DOI: 10.1007/s10452-022-09996-0

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