Peak Biomass Research Articles

Chitosan-mediated copper nanohybrid attenuates the virulence of a necrotrophic fungal pathogen Macrophomina phaseolina.

This study reported the synthesis and characterization of chitosan-copper nanoparticles (Ch-CuNPs) using a 1% copper sulfate solution in 0.2% w/v chitosan. The Ch-CuNPs, displaying a stable brick-red hue, showed an absorption peak at 572nm, indicative of monodisperse nanoparticle formation and surface plasmon resonance. X-ray diffraction confirmed the face-centered cubic structure with peaks at 36.78°, 43.38°, 50.56°, and 74.26°, and an average particle size of 87-89nm. FTIR analysis showed interactions between chitosan and copper, particularly around 3370 -3226cm⁻¹, 1633cm⁻¹, and 680cm⁻¹. In vitro assays revealed that Ch-CuNPs inhibited Macrophomina phaseolina growth by 18-71% at 0.03-0.09% concentrations, achieving complete inhibition at 0.12-0.15%, with PCA analysis confirming that growth peaked at lower concentrations and sharply declined at higher levels. Ch-CuNPs also altered fungal morphology and enzyme activity, with notable degradation at higher concentrations. The Cu uptake by the fungus peaked at 29.9% with 0.03% Ch-CuNPs and decreased at higher concentrations. FTIR analysis showed shifts and disappearance of peaks in fungal biomass treated with Ch-CuNPs, indicating molecular interactions and potential structural changes. This study underscores the potential of Ch-CuNPs as an effective antifungal agent and elucidates their interaction mechanisms.

Phytoplankton morphological traits and biomass outline community dynamics in a coastal ecosystem (Gulf of Trieste, Adriatic Sea)

AbstractTrait-based ecology has recently gained increasing importance in phytoplankton research. In particular, the taxonomic and morphological traits, such as size and shape of phytoplankton cells, can help to unveil the ecological processes and their drivers in the pelagic domain. Our study aims to shed light on the trophodynamics of phytoplankton communities in a coastal ecosystem in the northern Adriatic Sea (Gulf of Trieste) using data on individual traits such as biomass, size and shape of phytoplankton taxa during a one-year study. The phytoplankton parameters were investigated at the levels of the whole community, groups, and individual cells, analysing also the probability distributions of biomass and size of the latter level. The results showed good agreement between abundance and biomass data, as well as individual size and biomass with differences partly explained by cell shapes. We have emphasized the role of the local freshwater source in bottom-up control, alternating with top-down control of phytoplankton dynamics through taxonomic and morphological diversity. The predominant bimodal and non-power law distribution, especially during and around the biomass peaks, confirmed the importance of nano- and microphytoplankton size classes and the role of blooms in destabilizing the trophic webs. We suggest that the analyses of distribution types of individual cell size and biomass can be appropriate to spot ecological processes driving to unconstrained phytoplankton proliferation or to periods of trophic web stability.

High benthic community respiration and ecosystem response to phytodetrital input in a subpolar fjord on the West Antarctic Peninsula

AbstractGlaciomarine fjords dominate the coastal margin of the West Antarctic Peninsula. Studies in similar habitats in the Arctic have shown that benthic biodiversity and ecosystem functioning in inner and middle fjord basins are reduced by turbidity and sedimentation disturbance caused by climate warming–enhanced glacial melting. In contrast, the inner and middle fjord basins along the West Antarctic Peninsula are characterized as productivity and biodiversity hotspots, but benthic ecosystem functions remain unevaluated. In 2015–2016, we conducted sediment respiration and 13C pulse‐chase experiments to assess benthic ecosystem functions along a five‐station transect at ~ 500–600 m depths from the inner Andvord Bay fjord, through to Gerlache Strait, and onto the open continental shelf. Incubation samples from the inner and middle basins of Andvord Bay showed peaks in background seafloor respiration, benthic biomass, and uptake of labeled algal biomass compared to more outlying stations; the continental shelf exhibited the lowest levels of these variables, as well as dissolved inorganic carbon production. Macrofaunal community uptake was responsible for most of the C processing in the inner and middle parts of the fjord (> 45%) while dissolved inorganic carbon was the dominant repository of processed C near the fjord mouth and on the continental shelf (> 80%). The inner parts of Andvord Bay are hotspots of benthic C‐cycling and metabolism, in addition to biodiversity. Ongoing climate warming is likely to negatively impact these inner‐fjord hotspots by increasing meltwater input and sedimentation disturbance, yielding a reduction in the input and recycling of labile detritus at the seafloor in the inner‐middle fjord.

75-Year dynamics of the Black Sea phytoplankton in association with eutrophication and climate change

Based on a database containing species records obtained from 1948 to 2022 and a hydrochemical database, long-term changes in the biomass and taxonomic structure of phytoplankton in the deep-sea basin of the Black Sea were analysed in the stratified period from April to October. Over 75 years, a significant increase in concentration of nitrate, a weak increase in phosphate and a strong decrease in dissolved silicate were observed in the nutricline. The biomass of diatoms and total phytoplankton increased several times during the peak of eutrophication in 1991–1993, then decreased by the 2000s and has again shown an increasing trend in the last 15 years. The number of species dominant in biomass has halved from the 1940s–60s to the 2010s. The primary beneficiaries were the large- and medium-celled diatoms Pseudosolenia сalcar-avis and Proboscia alata, as well as the coccolithophore Emiliania huxleyi, the main dominant species of the last decade. Most noticeable was the increase in the amplitude and duration of the regular annual May–July bloom of E. huxleyi. Over the past three decades, its biomass has increased by more than an order of magnitude, accounting for about 40 % of the total phytoplankton biomass. Development of the large- and medium-celled diatoms, as well as the decrease in biomass of silicoflagellates, can be, at least partly, associated with the long-term decline in dissolved silicate in the upper layers. The trend towards a decrease in dinoflagellate biomass is probably associated with increased mixing intensity in the water column. Over the study period, the total phytoplankton biomass was positively related to nitrate stock in the water column. Short-term period (from one to several years) interannual variability was influenced predominantly by hydrophysical processes, primarily the intensity of winter convection. After cold winters with intense involvement of deep nutrients in the upper layers, the biomass of diatoms, coccolithophores and total phytoplankton increased. Thus, fluctuations in winter weather or local climate reduced or enhanced the effect of eutrophication, sometimes leading to the time gap between the peak in nitrate stock and phytoplankton biomass. The case of the Black Sea illustrates the complex pattern of the response of a marine ecosystem to the simultaneous impacts of anthropogenic and climate changes, leading to significant alterations in the functioning of the biological carbon pump.

Do plants respond to multi‐year disturbance rhythms and are we missing the beat?

Disturbance seasonality and return interval can create complex interactions of direct and indirect effects on species and ecosystems. Fire is a key grassland disturbance, yet long‐term research examining seasonality and return intervals is limited. A 15‐year experiment testing combinations of fire seasonality (summer, fall, spring) and return interval (2, 3, 6‐year) plus non‐burned controls was conducted in northern mixed prairie to evaluate effects on the plant community. Hesperostipa comata is a native C3 bunchgrass and dominant species in northern mixed prairie and previously observed to be fire‐sensitive. Current‐year aboveground biomass results were generally counter to expectations based on short‐term research. Fire increased H. comata biomass with a strong, rhythmic response pattern to a specific fire seasonality‐return‐interval combination (fall fire at 3‐year return intervals) that periodically increased biomass to more than three times that with no fire. Through the first four post‐fire growing seasons, biomass with summer, fall and spring fire across return intervals was 41, 89 and 93% of that with no fire. Afterward, no fire combination produced less biomass than no fire and recurring patterns emerged with large increases in biomass, particularly with fall fire at 3‐year intervals. Peak biomass years were regularly two growing seasons after 3‐year fall fire and occurred across wet, near‐average and dry conditions. We hypothesize that productivity responses were driven by the combination of demographic processes of seedling recruitment and synchronization of multiple tiller age classes. Because short‐term negative effects were reversed and regular patterns only emerged 5 years after study initiation, more long‐term research evaluating fire regimes is recommended to expand upon tests of individual factors over short periods. This suggestion is based on fire research, but likely applies to multiple forms of disturbance and demonstrates how demographic processes can inform responses for individual species and larger ecosystem functions, such as productivity.

High-resolution temporal NDVI data reveal contrasting intratidal, spring-neap and seasonal biomass dynamics in euglenoid- and diatom-dominated biofilms

Intertidal microphytobenthos (MPB) are a major contributor to primary production in estuarine ecosystems. While their biomass is highly variable at multiple spatial and temporal scales, the underlying drivers are as yet little understood. Both in situ sampling and remote-sensing techniques often lack the temporal resolution or coverage to simultaneously capture short-term (intratidal to daily) and longer-term (weekly to annual) biomass changes. Our field setup with in-situ NDVI sensors allowed us to study MPB surface biomass variability at high temporal resolution (10 mins) for up to two years in a freshwater euglenoid dominated mudflat, and a brackish and a marine diatom dominated mudflat. MPB biomass showed marked periodicities at multiple temporal scales: seasonal, spring-neap and intratidal. The diatom-dominated MPB community showed a seasonal biomass peak in winter, while the euglenoid-dominated community showed biomass peaks during spring and summer, probably caused by underlying divergent responses to mainly irradiance, temperature and wind-induced resuspension, and macrobenthos grazing. Spring-neap periodicity likely resulted from differential migratory responses of the MPB communities to variation in timing and duration of daylight exposure. In the freshwater community, upward migration only occurred when exposure duration was sufficiently long (≥4 h). In the diatom-dominated community, morning daylight exposure resulted in highest NDVI values. This study highlights the differences in MPB biomass dynamics between MPB communities within estuarine ecosystems, and underscores the great potential of high-resolution temporal NDVI monitoring for more accurate estimates of MPB biomass and primary production.

A stoichiometric insight into the seasonal imbalance of phosphorus and nitrogen in central European fishponds

BackgroundThis study examines seasonal and regional trends in chlorophyll-a concentrations and the dynamics of nitrogen (N) and phosphorus (P) in 32 fishponds (resulting in 150 pond-year cases) employed for fish production. Fishponds have a poor ecological state, requiring further insights for pond management. To gain those insights, monthly data on the pond environment were collected over the growing seasons from April to September (up to 14 years) across lowland to highland regions in Czechia. We used a ratio of dissolved inorganic nitrogen to total phosphorus (DIN:TP) to investigate seasonal patterns of N and P limitations.ResultsFishponds in the lowland region (below 199 m above sea level, a.s.l.) were predominantly N-limited (80%), while ponds in the midland region (200–449 m a.s.l.) exhibited P limitation at the beginning of the growing season (April–May) and N limitation by the end of the season (August–September; 90% of fishponds). Highland fishponds (above 450 m a.s.l.) showed frequent P limitations, especially during the beginning of the season. Chlorophyll-a concentrations varied on both regional and seasonal scales, with the overall phytoplankton biomass peak at 31 ha of pond surface area. Chlorophyll-a remained stable at the beginning of the season regardless of the DIN:TP ratio but increased with a lower DIN:TP ratio by its end. The chlorophyll-a concentrations were lowest at the beginning and highest at the end of the season and decreased with altitude.ConclusionsSeasonal and regional variations in nutrient limitations and chlorophyll-a occur in fishponds. Our study suggests that targeted seasonal nutrient input and enhanced monitoring can significantly improve fishpond management practices and ecosystem stability.

Are we focusing on the right parameters? Insights from Global Sensitivity Analysis of a Functional-Structural Plant Model

Abstract Performing global sensitivity analysis on functional-structural plant models (FSP models) can greatly benefit both model development and analysis by identifying the relevance of parameters for specific model outputs. Setting unimportant parameters to a fixed value decreases dimensionality of the typically large model parameter space. Efforts can then be concentrated on accurately estimating the most important input parameters. In this work, we apply the Elementary Effects method for dimensional models with arbitrary input types, adapting the method to models with inherent randomness. Our FSP model simulated a maize stand for 160 days of growth, considering three outputs, namely yield, peak biomass and peak leaf area index (LAI). Of 52 input parameters, 12 were identified as important for yield and peak biomass and 14 for LAI. Over 70 % of parameters were deemed unimportant for the outputs under consideration, including most parameters relating to crop architecture. Parameters governing shade avoidance response and leaf appearance rate (phyllochron) were also unimportant; variations in these physiological and developmental parameters do lead to visible changes in plant architecture but not to significant changes in yield, biomass or LAI. Some inputs identified as unimportant due to their low sensitivity index have a relatively high standard deviation of effects, with high fluctuations around a low mean, which could indicate non-linearity or interaction effects. Consequently, parameters with low sensitivity index but high standard deviation should be investigated further. Our study demonstrates that global sensitivity analysis can reveal which parameter values have the most influence on key outputs, predicting specific parameter estimates that need to be carefully characterized.

Growth analysis of kikuyo grass Cenchrus clandestinus (Hochst. ex Chiov.) Morrone fertilized with different levels of nitrogen

Contextualization: Forage production response is determined by factors inherent to the ecotype and external environmental and management conditions. The high variation of factors influencing forage growth implies the need to establish responses based on the biological development regarding the accumulated temperature. Knowledge gap: The growth response of Cenchrus Clandestinus expressed in heating degree days (HDDs) when fertilized with different doses of N is unknown to establish grazing times at peak biomass accumulation accurately. Purpose: To determine the growth dynamics of kikuyu grass with different levels of nitrogen fertilization. Methodology: A control treatment without application of any source of N (T0) was evaluated, a dosage of 100 kg. N ha.-1 (T1) and a dosage of 150 kg. N ha.-1 (T2). The fertilization plan was programmed for 42-day defoliation with a residual height of 10cm. Subsequently, the growth of kikuyu grass was evaluated with a seven-day frequency based on the analysis of dry matter, chlorophyll content, stomatal conductance, number of leaves, height, leaf area, and dry matter of leaves and stems. Growth rates were calculated from the dry matter of the forage: Absolute Growth Rate (AGR), Relative Growth Rate (RGR), Net Assimilation Rate (NAR), Specific Leaf Area (SLA), Leaf Area Ratio (LAR), and Leaf Area Index (LAI). Analysis of repeated measures was carried out to determine the effect per sampling point (HDDs) in a completely randomized arrangement. Results and conclusions: With the application of 150 kg. N ha.-1 and defoliation at 208.5 Grade Days Cumulative (GDC), plants showed higher growth rate, leaf tissue production, increased leaf expansion and greater height (p<0.05).

A circumpolar study unveils a positive non‐linear effect of temperature on arctic arthropod availability that may reduce the risk of warming‐induced trophic mismatch for breeding shorebirds

AbstractSeasonally abundant arthropods are a crucial food source for many migratory birds that breed in the Arctic. In cold environments, the growth and emergence of arthropods are particularly tied to temperature. Thus, the phenology of arthropods is anticipated to undergo a rapid change in response to a warming climate, potentially leading to a trophic mismatch between migratory insectivorous birds and their prey. Using data from 19 sites spanning a wide temperature gradient from the Subarctic to the High Arctic, we investigated the effects of temperature on the phenology and biomass of arthropods available to shorebirds during their short breeding season at high latitudes. We hypothesized that prolonged exposure to warmer summer temperatures would generate earlier peaks in arthropod biomass, as well as higher peak and seasonal biomass. Across the temperature gradient encompassed by our study sites (>10°C in average summer temperatures), we found a 3‐day shift in average peak date for every increment of 80 cumulative thawing degree‐days. Interestingly, we found a linear relationship between temperature and arthropod biomass only below temperature thresholds. Higher temperatures were associated with higher peak and seasonal biomass below 106 and 177 cumulative thawing degree‐days, respectively, between June 5 and July 15. Beyond these thresholds, no relationship was observed between temperature and arthropod biomass. Our results suggest that prolonged exposure to elevated temperatures can positively influence prey availability for some arctic birds. This positive effect could, in part, stem from changes in arthropod assemblages and may reduce the risk of trophic mismatch.

Long-term prediction of algal chlorophyll based on empirical models and the machine learning approach in relation to trophic variation in Juam Reservoir, Korea

This study analyzed spatiotemporal variation and long-term trends in water quality indicators and trophic state conditions in an Asian temperate reservoir, Juam Reservoir (JR), and developed models that forecast algal chlorophyll (CHL-a) over a period of 30 years, 1993–2022. The analysis revealed that there were longitudinal gradients in water quality indicators along the reservoir, with notable influences from tributaries and seasonal variations in nutrient regimes and suspended solids. The empirical model showed phosphorus was found to be the key determinant of algal biomass, while suspended solids played a significant role in regulating water transparency. The trophic state indices indicated varying levels of trophic status, ranging from mesotrophic to eutrophic. Eutrophic states were particularly observed in zones after the summer monsoons, indicating a heightened risk of algal blooms, which were more prevalent in flood years. The analysis of trophic state index deviation suggested that phosphorus availability strongly influences the reservoir trophic status, with several episodes of non-algal turbidity at each site during Mon. Increases in non-algal turbidity were more prevalent during the monsoon in flood years. This study also highlighted overall long-term trends in certain water quality parameters, albeit with indications of shifting pollution sources towards non-biodegradable organic matter. According to the machine learning tests, a random forest (RF) model strongly predicted CHL-a (R2 = 0.72, p < 0.01), except for algal biomass peaks (>60 μg/L), compared to all other models. Overall, our research suggests that CHL-a and trophic variation are primarily regulated by the monsoon intensity and predicted well by the machine learning RF model.

Seasonal phenology and starch allocation patterns in populations of Oxycaryum cubense f. cubense and paraguayense in Mississippi, Louisiana, and Florida

Abstract Phenological studies for Cuban bulrush [Oxycaryum cubense (Poepp. &amp; Kunth) Lye] have been limited to the monocephalous form in Lake Columbus (Mississippi). Accordingly, there is little available information on potential phenological differences among O. cubense forms (monocephalous vs. polycephalous) and populations in other geographic locations in the United States. Therefore, seasonal patterns of biomass and starch allocation in O. cubense were quantified from two populations in Lake Columbus on the Tennessee-Tombigbee Waterway in Mississippi (monocephalous), two populations from Lake Martin in Louisiana (polycephalous), and two populations from Orange Lake in Florida (polycephalous). Monthly samples of O. cubense inflorescence, emergent, and submersed tissue were harvested from two plots per state from October 2021 to September 2022. During monthly data collection, air temperature and photoperiod were recorded. Starch allocation patterns were similar among all sites, with starch storage being less than 1.5% dry weight for all plant tissues. Biomass was greatest in Lake Columbus (monocephalous; 600.7 g dry weight [DW] m−2) followed by Lake Martin (polycephalous; 392.3 g DW m−2) and Orange Lake (polycephalous; 233.85 g DW m−2). Peak inflorescence biomass occurred in the winter for the Lake Martin and Orange Lake populations and in the summer for the Lake Columbus population. Inflorescence biomass in Lake Columbus had a positive relationship (r2 = 0.53) with warmer air temperatures. Emergent and submersed biomass generally had negative relationships with both photoperiod and temperature (r2 = 0.02 to 0.77) in all sites. Peak biomass was also negatively related to temperature and photoperiod. Results from this study indicate that there are differences in biomass allocation between the two growth forms of O. cubense and that growth can occur at temperatures below freezing. Low temperature tolerance may allow this species to expand its range farther north than previously suspected.

Water Composition, Biomass, and Species Distribution of Vascular Plants in Lake Agmon-Hula (LAH) (1993–2023) and Nearby Surroundings: A Review

A significant change to the land cover in the Hula Valley was carried out during the 1950s: A swampy area densely covered by aquatic vegetation and the old shallow lake Hula were drained. The natural shallow lake and swamps land cover were converted into agricultural development land use in two stages: (1) Drainage that was accomplished in 1957; (2) Implementation of the renovated hydrological system structure, including the newly created shallow Lake Agmon-Hula (LAH), was completed in 2007. The long-term data record of the restored diversity of the submerged and emerged aquatic plant community, and its relation to water quality in the newly created shallow Lake Agmon-Hula LAH, was statistically evaluated. Internal interactions within the LAH ecosystem between aquatic plants and water quality, including nitrification, de-nitrification, sedimentation, photosynthetic intensity, and plant biomass and nutrient composition, were statistically evaluated. The plant community in LAH maintains a seasonal growth cycle of onset during late spring–summer and dieback accompanied by decomposed degradation during fall–early winter. The summer peak of aquatic plant biomass and consequent enhancement of photosynthetic intensity induces a pH increase during daytime and carbonate precipitation. Nevertheless, the ecosystem is aerobic and sulfate reduction and H2S concentration are negligible. The Hula reclamation project (HP) is aimed at the improvement of eco-tourism’s integration into management design. The vegetation research confirms habitat enrichment.

A comprehensive study of potential Arthrospira platensis cultivated in various manure‐based media for biodiesel feedstock

Arthrospira platensis has emerged as a promising biodiesel feedstock due to its rapid growth and substantial biomass. In efforts to reduce production costs, researchers have explored alternative media derived from livestock waste to modify conventional mediums for Arthrospira platensis cultivation. The experimental design of this research employed a Completely Randomized Design, with treatments comprising inorganic fertilizer (A), chicken manure (B), cow manure (C), and goat manure (D). The livestock manures were macerated for seven days before being utilized as A. platensis medium. The results revealed significant (p &lt; 0.05) impacts of different media on peak growth values and biomass production, reaching 2.03 ± 0.06 g/L and 1.76 ± 0.05 g/ L, respectively for chicken manure. The highest peak lipid content was observed in A. platensis cultured in goat manure medium. This study recommends goat manure as the preferred medium for mass cultivation of A. platensis. Mass cultivation in goat manure medium yielded 1.53 kg of dried biomass, with a lipid content of 1.91% and a biodiesel yield of 1.65%. The predominant fatty acid in this biodiesel was heneicosane, constituting 26.4% of the total area.

Distinct differences of vertical phytoplankton community structure in mainstream and a tributary bay of the Three Gorges Reservoir, China.

The vertical distribution of phytoplankton plays a crucial role in shaping the dynamics and structure of aquatic communities. In highly dynamic reservoir systems, water level fluctuations significantly affect the physiochemical conditions and the phytoplankton community. However, the specific effects on the vertical characteristics of phytoplankton between the mainstream and the tributary bay of the reservoir remain unstudied. This study investigated the vertical aspects of phytoplankton density, biomass, α and β diversity through monthly sampling over two years in the mainstream (Chang Jiang, CJ) and a tributary bay (Xiang Xi, XX) of the Three Gorges Reservoir in China. Phytoplankton density and biomass were significantly higher in XX, indicating an increased risk of algal blooms in the tributary. The phytoplankton community in CJ showed more stable species-environment relationships, a lower Shannon index and a higher evenness index, suggesting a relatively simple structure and a more uniform distribution of phytoplankton among different water layers. Conversely, XX showed greater differences between water layers (higher β diversity), with significant negative correlations with water level and positive correlations with DO difference, dissolved silica (DSi) difference, and stratification. Peak phytoplankton density and biomass, as well as high β diversity in XX, occurred during periods of decreased water levels with strong stratification in spring and summer. A structural equation model complemented by path analysis revealed that a decrease in water level could increase β diversity either directly through internal processes with extended residence time or indirectly by modifying stratification and the vertical distribution of DSi in XX. Therefore, a proposed water quality management strategy for XX was to increase the water level or reduce β diversity by implementing artificial mixing during stratification periods. Overall, this study lies in its comprehensive investigation of the vertical characteristics of the phytoplankton community in both the mainstream and the tributary bay of the Three Gorges Reservoir, elucidating the significant impact of water level fluctuations and providing insights for targeted water quality management strategies in the tributary bay to mitigate potential ecological impacts.

Different seasonal dynamics of contrasting aquatic plants and the consequences for the submerged macrophyte biodiversity

Global warming shifts climate zones to the north, resulting in changes in biodiversity. One of the species adaptation strategies to survive is to change their phenology. In temperate climate, most aquatic plants show their peak of biomass in summer. In our study, we hypothesised that the rare charophyte Lychnothamnus barbatus and the partially invasive vascular plant Myriophyllum spicatum may apply a different seasonality and cause a decrease in the biodiversity of submerged macrophytes. The object of our study was a mesotrophic temperate lake in Western Poland with abundant submerged vegetation, where macrophyte seasonality was studied from November 2015 to November 2019 (autumn, spring, summer). Altogether, 29 taxa of plants were recorded, including 13 species of charophytes (40 % of the Polish charophyte flora) but only four species co-dominated, two eutrophic vascular plants, Ceratophyllum demersum and M. spicatum, and two charophytes, the rare mesotrophic L. barbatus and common Nitellopsis obtusa. M. spicatum due to its expansiveness in the shallow littoral decreased biodiversity in the study lake. Moreover, C. demersum negatively affected the endangered L. barbatus by direct competition for habitats in the lake. L. barbatus and M. spicatum dominated in vegetation in autumn while the further two species co-dominated in summer. L. barbartus and M. spicatum seem to avoid high competition in summer, which proves a high adaptive potential with respect to climate warming. However, further study in other lakes is needed to verify the relevance of our findings in terms of the conservation of rare macrophyte species.

Cover crops affect pool specific soil organic carbon in cropland – A meta‐analysis

AbstractCover crops (CC) offer numerous benefits to agroecosystems, particularly in the realm of soil organic carbon (SOC) accrual and loss mitigation. However, uncertainties persist regarding the extent to which CCs, in co‐occurrence with environmental factors, influence SOC responses and associated C pools. We therefore performed a weighted meta‐analysis on the effects of CCs on the mineral‐associated organic carbon (MAOC), the particulate organic carbon (POC) and the microbial biomass carbon (MBC) pool compared to no CC cultivation in arable cropland. Our study summarized global research of comparable management, with a focus on climatic zones representative of Europe, such as arid, temperate and boreal climates. In this meta‐analysis, we included 71 independent studies from 61 articles published between 1990 and June 2023 in several scientific and grey literature databases. Sensitivity analysis was conducted and did not identify any significant publication bias. The results revealed that CCs had an overall statistically significant positive effect on SOC pools, increasing MAOC by 4.8% (95% CI: 0.6%–9.4%, n = 16), POC by 23.2% (95% CI: 13.9%–34.4%, n = 39) and MBC by 20.2% (95% CI: 11.7%–30.7%, n = 30) in the top soil, compared to no CC cultivation. Thereby, CCs feed into the stable as well as the more labile C pools. The effect of CCs on MAOC was dependent on soil clay content and initial SOC concentration, whereas POC was influenced by moderators such as CC peak biomass and experiment duration. For MBC, for example, clay content, crop rotation duration and tillage depth were identified as important drivers. Based on our results on the effects of CCs on SOC pools and significant moderators, we identified several research needs. A pressing need for additional experiments exploring the effects of CCs on SOC pools was found, with a particular focus on MAOC and POC. Further, we emphasize the necessity for conducting European studies spanning the north–south gradient. In conclusion, our results show that CC cultivation is a key strategy to promote C accrual in different SOC pools. Additionally, this meta‐analysis provides new insights into the state of knowledge regarding SOC pool changes influenced by CCs, offering quantitative summary results and shedding light on the sources of heterogeneity affecting these findings.

HPLC validation as a management tool in artificial water storage ponds

Pigment analysis through high-performance liquid chromatography (HPLC) offers a faster and more replicable study of the phytoplankton community structure than traditional taxonomy, but its application to small-sized freshwater ecosystems is infrequent. We carried out a taxonomy-based validation for the application of HPLC to the management of two artificial water storage ponds. We also investigated the error and variability sources that affected the relationships between calculated biovolumes of phytoplankton groups and associated pigment concentrations. For both qualitative and quantitative approaches, agreement was obtained between techniques that consistently identified biomass peaks and structural trophic differences between the ponds. Considering the most relevant pigment to biovolume ratios for total biomass, and partial biomass proxies of green algae and fucoxanthin containing algae, a decreasing tendency was obtained as total and partial biomass increased in all the studied models. Bidirectional variability affecting these relationships scaled under high biomass conditions and suggested a better suitability of HPLC application under oligotrophic conditions, which is in line with previous studies. Additionally, pigment data was able to identify mean stored volume as the main environmental factor that drove trophic differences between the ponds. We conclude that HPLC is accurate not just for monitoring purposes, but to carry out ecosystem-level assessments in artificial ponds. Therefore, we endorse the use of HPLC as part of the monitoring networks in small-sized freshwater ecosystems.

Fish weight reduction in response to intra‐ and interspecies competition under climate change

AbstractAs described by the temperature–size rule paradigm, fish living in warmer temperatures grow faster but have a smaller mature body size. However, the changes in the body size of fish communities in the western North Pacific, which is one of the most active fishing grounds, remain unclear. This study aimed to investigate changes in the body size of fish assemblages in the western North Pacific and whether fish sizes were potentially driven by the temperature–size rule, bottom‐up effects and intra‐ and interspecies competition at a community scale. We evaluated the fish weight data of 6 stocks of 4 species from 1978 to 2018 and 17 stocks of 13 species from 1995/1997 to 2018. Weight reduction in the fish assemblage was observed in the 1980s and was associated with the biomass peak of the Japanese sardine (Sardinops melanostictus), indicating the effect of intra‐ and interspecies competition. Another weight reduction was observed in the 2010s, which was associated with a moderate increase in the biomass of the Japanese sardine and chub mackerel (Scomber japonicus). Our analyses indicate that stronger stratifications in the surface layers during the 2010s potentially reduced the nutrient supply from the subsurface to the surface layers. This limitation in food availability forced intra‐ and interspecies competition under a moderate increase in fish biomass. Our findings underscore the critical significance of integrating the impacts of species competition and climate change on fish sizes to improve fishery management at a community level.

Spatiotemporal variability of evapotranspiration in Alpine grasslands and its biotic and abiotic drivers

AbstractTo gain a deeper understanding of the water balances of Alpine grassland ecosystems, it is crucial to know the abiotic and biotic drivers of evapotranspiration. The abiotic drivers are very heterogeneous in mountain regions because elevation, slope and aspect control incoming Rs, and atmospheric layering affect air temperature, humidity and wind distribution. In a study with 24 lysimeter plots distributed over a study area of approx. 300 km2 in the Eastern Alps, we covered a wide range of topographic conditions. We investigated the effects of abiotic drivers on evapotranspiration by measuring evaporation from a free‐water body (Ew). For the biological modulation of crop evapotranspiration (ETc), we analysed two different grassland types (at peak biomass and at low biomass) and calculated the respective crop coefficients (Kc). Results showed that primarily physical drivers such as the accumulated solar radiation from sunrise to measurement (Rs_acc), followed by atmospheric pressure (P), wind speed (u) and vapour pressure deficit (VPD) influence both Ew and ETc. Moreover, ETc is also significantly influenced by standing biomass and the grassland type (i.e., resource use strategies of the vegetation types) and by the geographic location along the valley (i.e., entrance, middle and head of the valley). We suppose plant stress and/or ground winds to be the underlying factor for the significance of the geographic location, yet further research is needed. The current study helps towards a better understanding of the water balance in alpine grassland ecosystems, but we also show that some spatial drivers cannot yet be adequately addressed.