Increase In Water Temperature Research Articles

Effects of different water temperatures on the ovarian development and biochemical composition of Portunus trituberculatus after mating (Decapoda, Portunidae)

Abstract This study investigated the effects of different water temperatures (20, 23, 26 and 29°C) on the ovarian development and biochemical composition of Portunus trituberculatus (a swimming crab) after mating. The results showed that the higher the water temperature was, the faster the ovarian development, especially the GSI in the 29°C group was significantly higher than that in the 20°C and 23°C groups (). The hepatosomatic index (HSI) decreased with increasing water temperature, but there was no significant difference between the groups at different water temperatures (). The muscle yield (MY) was basically maintained at approximately 34%. The condition factor (CF) of the crab reached 0.62 in the 29°C group, which was significantly higher than that in the 20°C and 23°C groups (). Histological observation revealed that the number of lipid droplets and the degree of homogenization of yolk granules in ovarian oocytes gradually increased with the increase of the water temperature. From the perspective of conventional biochemical composition, the moisture and crude protein contents in muscle and the crude fat content in hepatopancreas did not change much among the groups, but the crude protein content in the ovary of the 29°C group was as high as 24.65%, which was significantly higher than that in the other three groups (). In terms of fatty acid composition, there was little difference in the fatty acid content in the ovaries of the different water temperature groups. The contents of C22 : 2n6 and C18 : 3n3 in polyunsaturated fatty acids were significantly higher in the 29°C group than in the other three groups (). In the hepatopancreas, the contents of C22 : 5n3 (DPA) and C22 : 6n3 (DHA) in the 20°C group were the lowest, 0.07% and 0.15%, respectively, which were significantly lower values than in the 29°C group (). The change of amino acid content is mainly reflected in ovarian tissues, showing a gradual upward trend as a whole. Furthermore, the essential amino acid score (EAAS) and average score of the two tissues in the 20°C and 23°C groups were relatively close, and both reached the highest score in the 29°C group. Overall, with increasing water temperature, the rate of ovarian development significantly accelerated, and the nutritional quality of the tissues improved in these swimming crabs.

Spatial Patterns and Environmental Control of Polychaete Communities in the Southwestern Barents Sea

The Barents Sea region is influenced by an increased inflow of warm Atlantic water, which impacts all components of the local ecosystem. Information on the state of benthic communities is required to predict alterations in the food web’s structure and functioning. The spatial distribution of polychaete communities was investigated in relation to environmental conditions at nine stations along the Kola Transect (70°00′–74°00′ N, 33°30′ E) in April 2019. A taxonomically diverse fauna containing 114 taxa was found, with 95 identified at the species level. The fauna was composed predominantly of boreo-Arctic species (63%), followed by boreal (22%) and Arctic species (13%). The polychaete abundance and biomass exhibited considerable variability, ranging from 910 to 3546 ind. m−2 and from 3.4 to 72.7 g m−2, with average values of 1900 ind. m−2 and 18.7 g m−2, respectively. Cluster analysis revealed three distinct polychaete communities differing in dominant species composition, abundance, and biomass. The southern region featured the most abundant community, the middle part exhibited the highest diversity, and the northern area presented the community with the highest biomass. These spatial variations in community structure corresponded closely to the distribution and properties of water masses within the study area. Multivariate analysis identified depth as the primary driver of diversity indices, with higher values observed at shallow water sites. Salinity and water temperature together explained 46% of the variation in abundance, reflecting warming effects and showing positive or negative effects, depending on the taxa. Furthermore, an increase in water temperature had a positive impact on the contribution of boreal species to the total material, while exerting a strong negative effect on the overall community biomass, underscoring the potential of polychaetes in biological indication.

Research on control strategy of electric vehicle thermal management system motor

Abstract The low efficiency and difficulty in low-temperature heating are the challenges currently faced by the thermal management system of new energy vehicles. A multi-heat source vehicle thermal management system for waste heat cascade recovery and utilization was proposed, and the performance of the vehicle thermal management system was studied through a combination of component testing and one-dimensional simulation. Based on a one-dimensional simulation model, the characteristics of the motor waste heat source are analyzed. The increase in the inlet water temperature of the motor coolant will lead to enhanced heat dissipation of the motor to the air, resulting in a waste of motor waste heat. Based on the results of the analysis, an energy cascade management strategy is constructed. The optimal heating mode is selected by collecting temperature signals such as motors, and the cut-off valve is controlled through logic gates to achieve flexible switching of different modes. The system effectively reduces the energy consumption of thermal management systems, which is of great significance for developing thermal management systems for new energy vehicles.

Development of membrane distillation powered by engine exhaust for water desalination

To address water shortage in arid areas and make use of waste heat, an experimental investigation is presented for a novel system of air gap membrane distillation unit driven by an engine exhaust heat source for the development of an on-board car water desalination. The design of the gas-to-water heat exchanger is presented and optimized. The system’s performance, governed by the achieved feed water temperature and measured by the output vapor mass flux, is evaluated with time under varying operational parameters, including engine load, engine speed, and feed water flow rate, with the analysis of production cost for economic viability. Experimental results revealed that higher engine loads and speeds lead to rapid temperature increase of the feed water, enhancing the efficiency of the membrane distillation process and increasing the permeate flux. Notably, a maximum permeate flux of 45 kg/m2h was achieved after 40 min of operation. A minimum production cost of 3.2 $/m3 is estimated at an engine load of 35 N.m. With production costs ranging from 3.2 to 5.8 $/m3, the proposed system emerges as a highly competitive option when compared with other membrane distillation systems driven by waste heat in literature. This study underscores the potential of utilizing waste heat from car engines for cost-effective and sustainable water desalination, paving the way for further development and implementation of the system as a mobile desalination unit for different applications.

Driving mechanism of land use and landscape pattern to phytoplankton and zooplankton community and their trophic interactions in river ecosystems

The trophic interactions between phytoplankton and zooplankton communities are essential for maintaining river ecosystem integrity and health. However, the driving mechanisms of land use and landscape patterns (LULP) affecting their trophic interactions are not fully understood. Therefore, the research objective of this study was to reveal the driving mechanisms of LULP on the interaction of phytoplankton with zooplankton through remote sensing interpretation of LULP in different buffer scales (500 m, 1000 m, 1500 m, and catchment), combined with water environment factors and plankton community structures analyzed. Results showed that LULP had the most significant effect on the phytoplankton and the zooplankton community structure at 500 and 1500 m buffer scales, respectively. Construction land (CON) and edge density (ED) most influenced phytoplankton and zooplankton community structure and their influence mechanisms were identified, i.e., CON increased the species (S) of phytoplankton by increasing the concentration of NO3-N in river water at the 500 m buffer scale. ED reduced the biological density (BD) of zooplankton by decreasing the concentration of heavy metal (HM) in river water at the 1500 m buffer scale. The water area (WAT) and ED showed the most significant influence on plankton interaction. Three pathways were found to explain their influence mechanisms, i.e., ED decreased the BD or Shannon-Weiner index (H’) of zooplankton by increasing the dissolved oxygen (DO) to enhance BD of phytoplankton in river water at the 1500 m buffer scale; the WAT increased the BD of phytoplankton by increasing water temperature to reduce the H' of zooplankton at the 500 m buffer. These findings have implications for effective ecological planning of future human activities in the stream domain and maintaining river ecosystem health.

Water Temperature Model to Assess Impact of Riparian Vegetation on Jucar River and Spain

Water temperature is a critical factor for aquatic ecosystems, influencing both chemical and biological processes, such as fish growth and mortality; consequently, river and lake ecosystems are sensitive to climate change (CC). Currently proposed CC scenarios indicate that air temperature for the Mediterranean Jucar River will increase higher in summer, 4.7 °C (SSP5-8.5), resulting in a river water temperature increase in the hotter month; July, 2.8 °C (SSP5-8.5). This will have an impact on ecosystems, significantly reducing, fragmenting, or even eliminating natural cold-water species habitats, such as common trout. This study consists of developing a simulated model that relates the temperature of the river with the shadow generated by the riverside vegetation. The model input data are air temperature, solar radiation, and river depth. The model proposed only has one parameter, the shadow river percentage. The model was calibrated in a representative stretch of the Mediterranean river, obtaining a 0.93 Nash–Sutcliffe efficiency coefficient (NSE) that indicates a very good model fit, a 0.90 Kling–Gupta efficiency index (KGE), and a relative bias of 0.04. The model was also validated on two other stretches of the same river. The results show that each 10% increase in the number of shadows can reduce the river water temperature by 1.2 °C and, in the stretch applied, increasing shadows from the current status of 62% to 76–87% can compensate for the air temperature increase by CC. Generating shaded areas in river restorations will be one of the main measures to compensate for the rise in water temperature due to climate change.

Distribution Characteristics of Trichiurus japonicus and Their Relationships with Environmental Factors in the East China Sea and South-Central Yellow Sea

The largehead hairtail (Trichiurus japonicus) is the most productive fish caught in China. In order to understand the seasonal distribution of T. japonicus in the East China Sea and the central and southern parts of the Yellow Sea, three species distribution models were used in this study, namely the random-forest model, K-nearest-neighbor algorithm, and gradient-ascending decision-tree model, based on the data of trawling surveys in the East China Sea and central and southern parts of the Yellow Sea from 2008 to 2009. Combined with a variance inflation factor and cross-check, a distribution model of T. japonicus was screened and constructed to analyze the influence of environmental factors on the distribution of T. japonicus in the East China Sea and central and southern parts of the Yellow Sea. The results showed that the random-forest model had the advantages of fitting effect and prediction ability among the three models. The analysis of this model showed that the water depth, bottom water temperature, and surface salinity had a great influence on the habitat distribution of T. japonicus. The relative resources of T. japonicus increased with the increase of bottom water temperature, reached the maximum at 23.8 °C, and first increased and then decreased with the increase of water depth and surface salinity, reaching the maximum when water depth is 72 m and surface salinity is 31.2%. This study also used the random-forest model to predict the spatial distribution of T. japonicus in the central and southern waters of the East China Sea and south-central Yellow Sea from 2008 to 2009, and the results showed that the predicted results were close to the actual situation. The research results can provide a reference for the exploitation and protection of T. japonicus resources in the East China Sea and the south-central Yellow Sea.

A temperature tipping point in hypoxic zone size

AbstractTemperature increases will have ubiquitous effects on aquatic food webs, from microbes to consumers, and affect the quality and quantity of carbon flows within and between water layers. A decline in the biological pump moving carbon from surface to lower layers is anticipated. We reviewed 37 years of data on hypoxic zone size and water quality in the northern Gulf of Mexico to determine if air and bottom water temperature increases (0.5°C decade−1) are significantly related to variations in its areal size. There was no significant decline in important river water quality in the 24 years since the national Hypoxia Action Plan was developed to reduce its size. Changes in the ratio of km2 hypoxia per 1000 mt nitrate loading from the Mississippi River from 2000 to 2023 reveals a tipping point in the hypoxic zone size that is driven by ocean warming. Biological factors varying with temperature such as ectotherm growth rates, zooplankton grazing, cell sinking rates, and diatom sequestration of Si or N are apparently more important influences on recent hypoxic zone size than variations in physical factors. This tipping point may be common to similarly warmed and eutrophic coastal waters where warming will likely result in diminished oxygen deficiency (< 2 mgO2 L−1). Hypoxia and food web models assuming a stationary equipoise of nutrient loadings, ratios and food webs will be deficient as coastal waters warm further, coastal storm and hurricane frequency increase and land uses in the watershed are altered with climate change.

Natural and anthropogenically driven change of organic carbon burial rate in two alpine lakes from the southeastern margin of the Tibetan Plateau

The rate of organic carbon (OC) burial in lakes depends considerably on natural and anthropogenic factors. Delineating how and to what extent potential drivers shape a lake’s OC burial rate is crucial for anticipating OC sequestration under future environmental change scenarios. Alpine lakes provide valuable opportunities for studying the influence of climate warming and atmospheric nitrogen (N) deposition on OC burial in lakes, owing to the lack of human activities in their catchments; however, this aspect has not been sufficiently documented. Here, the OC burial rate was reconstructed in two alpine lakes (Heihai and Jiren) from the southeastern margin of the Tibetan Plateau over the past ∼ 160 years, and the associated drivers were identified by resolving the temporal trends in organic matter (OM) input from specific sources to lake sediments via paleolimnological methods. The results demonstrated a consistently low OC burial rate (6.21–10.86 g m−2 yr−1) in Lake Heihai. The low hydrogen index (HI), moderate Paq, and high long-chain n-alkane flux revealed that submerged macrophytes and terrestrial plants are major contributors to the sequestrated OC. The notable decrease in the OC burial rate after 1980 was hypothesized to be caused by regional climate warming during this period because a greater export of terrestrial materials under such a climate can inhibit light penetration, diminishing submerged macrophyte productivity and OM input. In contrast, the synchronous input of higher amounts of terrestrial plant OM was largely degraded owing to the increased water temperature and the intensification of water column stratification. In Lake Jiren, a notably high OC burial rate (13.82–46.75g m−2 yr−1) was observed. The high HI, Paq, and short-chain n-alkane flux showed that phytoplankton and submerged macrophytes were the major contributors to the sequestrated OC. The two-phase increase in the OC burial rate in this lake, including a slow increase after 1947 and a rapid increase after 1983, might have resulted from strengthening aquatic primary productivity and OM input, driven by anthropogenic intensification of nutrient emissions, especially reactive N, from highly urbanized areas and the subsequent long-term atmospheric transport and deposition of these materials over the lake basin. A comparative analysis of the results between the two lakes suggested that atmospheric N deposition has a stronger influence on the OC burial than climate warming. These drivers affect the OC burial rate by altering aquatic productivity rather than the terrestrial OM input. This study provides a basic for predicting future OC burial scenarios in warmer climates with more intense anthropogenic N emissions.

Determining the Consequences of Climate Change for Aquatic Ecosystems Using Bioassay Methods: a Review

The article describes the scientific and methodological possibilities of bioassay in the field of studying the effects of climate change on water bodies and aquatic organisms. In fish aquaculture, it was revealed that an increase in water temperature changes the biochemical parameters of the internal environments of organisms, affects their behavior and the number of offspring. A number of biogeochemical transformations of aquatic ecosystems are predicted: a decrease in the pH of water, mineralization of organic matter of bottom sediments, release and increase in bioavailability of compounds of potentially toxic elements. Bioassay methods using monocultures and laboratory microcosms have shown that maximum temperature values and a cascade of concomitant changes will lead to a restructuring of the aquatic life community, changes in the habitats of organisms, and the disappearance of stenothermic species. The realism of such scenarios is confirmed by paleodata and modern natural phenomena.

Elevated temperature increases the susceptibility of D. magna to environmental mixtures of carbamazepine, tramadol and citalopram

The joint risks assessment of thermal stress and rising loads of pharmaceuticals (PhACs) in surface waters is a relevant topic in aquatic ecotoxicology. This study investigated the relevance of increased water temperature to alter the acute toxicity of environmentally relevant carbamazepine (CBZ), citalopram (CIT) and tramadol (TRA) concentrations as mixtures (ECs) and delayed outcomes in Daphnia magna. Responses of detoxification and antioxidant pathways in premature daphnids post an acute 24 h (pulsed) exposure to the PhACs mixtures and delayed responses as the reproductive output over 14 days recovery were investigated under 21- and 26 °C incubation. Biphasic modulation in glutathione S-transferase (GST) activity and significant inhibition of superoxide dismutase (SOD) activity were observed in both thermal regimes with significant shift in effective thresholds from 10-fold ECs at 21 °C to ECs at 26 °C incubation. Significant induction in catalase (CAT) activity and oxidative stress development were recorded at elevated temperatures from the 10-fold ECs dose onward. Pulsed exposures at 26 °C also led to significant decrease in the reproduction of daphnids above the 10-fold ECs of PhACs. The Integrated Biomarker Response scoring (IBRv2) approach outlined a 1.8-fold increase in alterations of daphnids exposed to 100-fold ECs of PhACs at 26 °C.

Temporal Patterns of Fish Occurrence in the Colorado River, Grand Canyon in Response to Temperature, Largescale Drought, and Newly Exposed Habitat

ABSTRACTTwo large dams on the Colorado River, Glen Canyon and Hoover Dam, have profoundly altered the river within Grand Canyon. Owing to widespread drought and increased water usage throughout the Southwest, water levels in Lake Mead declined by over 40 m since 2000, exposing over 80 km of newly emerged riverine habitat in the western Grand Canyon that experiences higher water temperatures and increased turbidity relative to upstream portions of the Colorado River within the Grand Canyon. Our objective was to investigate how the probability of fish occurrence has changed within the Colorado River in Grand Canyon as abiotic conditions have shifted in relation to these altered environmental conditions. We used 22 years of long‐term fish monitoring data, from 2000 to 2022, on the mainstem of the Colorado River in the Grand Canyon to map the probability of occurrence based upon modeled water temperature for native and common nonnative salmonid species through space (river kilometer) and time in relation to declining water levels in Lake Mead. Our results suggest that native fish occurrence is strongly correlated with longitudinally increasing water temperature, while nonnative trout species were negatively correlated with increased water temperature downstream from the dam. Further, we found that nonnative trout species have experienced decreases in their probability of occurrence through time, while natives have experienced an increase in probability of occurrence. Information on distribution of fish prior to reservoir declines, and how the fish assemblage has shifted coincident with environmental changes, can help inform future management of native and nonnative fish in highly regulated river systems.

Detection of Floating Algae Blooms on Water Bodies Using PlanetScope Images and Shifted Windows Transformer Model

The increasing water temperature due to climate change has led to more frequent algae blooms and deteriorating water quality in coastal areas and rivers worldwide. To address this, we developed a deep learning-based model for identifying floating algae blooms using PlanetScope optical images and the Shifted Windows (Swin) Transformer architecture. We created 1,998 datasets from 105 scenes of PlanetScope imagery collected between 2018 and 2023, covering 14 water bodies known for frequent algae blooms. The methodology included data pre-processing, dataset generation, deep learning modeling, and inference result generation. The input images contained six bands, including vegetation indices such as the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), enhancing the model’s responsiveness to algae blooms. Evaluations were conducted using both single-period and multi-period datasets. The single-period model achieved a mean Intersection over Union (mIoU) between 72.18% and 76.47%, while the multi-period model significantly improved performance, with an mIoU of 91.72%. This demonstrates the potential of our model and highlights the importance of change detection in multi-temporal images for algae bloom monitoring. Additionally, the padding technique proposed in this study resolved the border issue that arises when mosaicking inference results from individual patches, providing a seamless view of the satellite scene.

Metabolic Rate of Goldfish (Carassius auratus) in the Face of Common Aquaculture Challenges.

This study examined the metabolic rate (MO2, oxygen consumption) of goldfish (Carassius auratus) under normal management conditions in aquaculture. Using an intermittent respirometry system, we assessed daily variations and the effects of feeding, handling, temperature increase, and anesthetics. MO2 exhibited a daily rhythm, with higher values during day. Feeding to satiety produced a 35% increase in MO2 compared to fasted animals, with a maximum peak after 3 h and returning to baseline after 7 h. Handling stress (5 min) produced a 140% MO2 peak (from 180 to 252 mg O2 kg-1 h-1), returning to the routine MO2 after 2.5 h. An increase in water temperature (+0.1 °C min-1) up to 30 °C caused MO2 to peak at 200% after 2.5 h from the start of the temperature increase. The use of common anesthetics in aquaculture (MS-222, 2-phenoxyethanol and clove oil in deep anesthesia concentration) affects MO2 during the first few minutes after anesthetic recovery, but also during the following 4 h. It can be concluded that the metabolic rate is a good indicator of the goldfish's response to aquaculture practices involving energy expenditure and stress. Thus, intermittent respirometry is a valuable non-invasive tool for understanding and improving fish welfare in aquaculture.

Пространственная и временная изменчивость нанофитопланктона в фьордах Западного Шпицбергена в летний период.

The paper presents the results of studies of nanophytoplankton in the fjords of Western Spitsbergen in the summer of 2001, 2002, 2003 and 2017. It is shown that the water area of each fjord is characterized by a fragmentation of the community of planktonic nanoalgae with depth and from the apex to the mouth region, as well as a deepening of the core of maximum abundance at the exit from the fjord, regardless of the density structure of the water column. For fjords of different latitudinal locations, a decline in integral indicators, a lowering of the community core from the surface horizon, and the replacement of large size fractions by cells smaller than 5 μm in the northern direction as the water temperature increases were recorded. In terms of interannual variability, the total abundance and structural organization of nanophytoplankton were determined by the degree of temperature stratification. In the summer of 2017 an increase in the absolute values of abundance and biomass by 1–2 orders of magnitude compared to zero years was revealed, while maintaining the main features of the structural organization of the community.

Changes in Phytoplankton Community Structure in Qingcaosha Reservoir Based on Time Series Analysis

Qingcaosha Reservoir is one among the important reservoirs and drinking water sources in Shanghai. Samples were collected from the reservoir every month from 2014 to 2021 to analyze phytoplankton community structure and water environmental factors to provide a reasonable reference for urban reservoir operation management, water resource protection, and development and utilization. The results showed that 561 species of phytoplankton were identified from eight phyla in 8a, mainly diatomata, chlorophyta, and cyanophyta, accounting for 34.94%, 34.58%, and 17.65% of the total species, respectively. A total of 26 dominant species were present in four phyla, and cyanobacteria accounted for 50%. Diatoms and green algae were the dominant species, cyanobacteria was the absolute dominant species, and other phyla accounted for a low proportion in the community structure. The Qingcaosha reservoir had the tendency of transforming into a cyanobacteria-type reservoir. The major dominant genera of chlorophyta were Scenedesmus, Ankistrodesmusc, and Chlorellaceae. The dominant genera of the phylum cyanobacteria were Merismopediaceae, Microcystaceae, Aphanocapsa, and Pseudanabaenaceae. The major dominant genera of the diatoms were Cyclotella, Melosira, and Aulacoseira. The dominant genus of xanthophyta was Tribonemataceae. Phytoplankton abundance ranged from 8.391×105 to 2.115×107 cells·L-1, with an average of 6.345×106 cells·L-1. The biomass of phytoplankton varied from 0.113 to 11.903 mg·L-1, with an average of 1.538 mg·L-1. The maximum abundance occurred in summer, and the maximum biomass occurred in spring. In spatial distribution, the maximum biomass and abundance appeared in the reservoir. Redundancy analysis （RDA） of phytoplankton community structure and water environmental factors showed that water temperature （WT）, dissolved oxygen （DO）, and nutrient salts （TN, TP） were important environmental factors affecting phytoplankton community structure, and significant changes occurred in 2014-2017 and 2018-2021. From 2018 to 2021, cyanobacteria disappeared and cyanobacteria dominated the reservoir and even changed to cyanobacteria-type reservoirs. From 2016 to 2021, half of the dominant species were cyanobacteria, and the cyanobacteria abundance accounted for the highest proportion during this period. The reasons for the extinction of xanthophyta were speculated to be the increase in phosphorus concentration and water temperature, and the reasons for the dominant position of cyanophyta, to be the rise of water level, water temperature, and alkaline water. Reservoirs use filter-feeding fish to control algal overgrowth； however, filter-feeding fish do not filter all algae and not all of their filter-feeding algae is easily digestible. In this study, it was observed that the size of digestible algae biomass in the four seasons was in the order of spring > summer > autumn > winter. RDA analysis of silver carp, bighead carp, and digestible algae showed that the biomass of digestible algae was positively correlated with that of silver carp and bighead carp in spring, autumn, and winter. These results suggest that the digestibility of algae changed the resource use efficiency of filter-feeding fish and led to changes in phytoplankton community structure. The phytoplankton community structure was directly affected by the descending effect of fish and indirectly affected by the digestibility of algae.

Water heater storage heat pump cycle for higher operating range

Heat pumps for water heating have become increasingly attractive. However, the achievable water temperature using a vapor compression heat pump water heater (HPWH) is often constrained by the compressor operating envelope. To address this challenge, HPWHs typically employ two-stage compression with complex system architecture or rely on back-up electric heating. This work introduces an alternate storage heat pump concept to improve the operating temperature range of an R134a HPWH system. The developed system operates in two modes: Mode I functions as a typical wrap-around condenser HPWH, while Mode II splits the wrap-around coil to use the top portion as a condenser and the bottom portion as evaporator. System modeling consisting of a vapor compression cycle and water tank sub-models was conducted to study the performance. The model was validated experimentally. The storage heat pump system could achieve an additional increase of 12 °C beyond the maximum possible water temperature of 46 °C which was achieved using the baseline conventional HPWH system. In Mode II, the system exhibits a 20 % higher average heating capacity and a 15 % lower average pressure ratio compared to the conventional system operating at a 27 °C ambient temperature. Compared to usage of electric heating elements, our system showed a longer recovery time with a 50 % lower energy consumption for a similar increase in water temperature.

Shifting spawning phenology in Hudson River American Shad

AbstractObjectiveThe objectives of this study were to investigate potential shift in the phenology of spawning for the Hudson River American Shad Alosa sapidissima and to identify factors contributing to the decline of the Hudson River shad population.MethodsThis study utilized American Shad eggs collected from the Long River Ichthyoplankton Survey. Logistic models were employed to estimate spawning phenology metrics, including the onset, peak, cessation, and duration of the spawning season. Additionally, we investigated the effects of biotic and abiotic variables on spawning timing.ResultThis study suggests that temporal changes in the spawning onset exhibited high variation and were not significant. However, a significantly delayed spawning peak and cessation, along with an extended spawning season, were observed. Additionally, the findings of this study revealed a correlation between the timing of spawning onset and water temperature, indicating that a 1°C increase in water temperature was associated with a 3.66‐day earlier initiation of spawning. Smaller female spawner size was associated with delayed peak and cessation of the spawning season. With a 1‐cm decrease in the average female spawner size, the peak of the spawning season was delayed by 1.79 days and the cessation of the spawning season was delayed by 2.87 days.ConclusionThe findings indicate that water temperature may be a crucial trigger for initiating spawning in Hudson River American Shad, with higher water temperatures associated with earlier spawning onset. Moreover, the findings indicate that the timing of spawning peaks and cessations has been progressively delayed over time, and this is linked to the size of female spawners.

Subsurface Marine Heatwaves in the South China Sea

AbstractMarine heatwaves (MHWs), extreme warm ocean temperature events, greatly impact marine ecosystems. While most MHW studies in the South China Sea (SCS) focus on the sea surface, subsurface characteristics remain less explored. This study uses high‐resolution (1/12°) ocean reanalysis data sets to assess MHW properties with depth in the SCS from 1993 to 2022. We find that MHW intensities are typically stronger at subsurface levels (30–150 m) than at the surface, with significant spatial variations. The vertical structures of MHW maximum and cumulative intensities peak between 70 and 100 m with 2.7°C and 63°C days, respectively; MHW annual days and duration increase gradually from 10 to 2,000 m with duration peaks at 2,000 m (∼60 days), four times longer than that at the surface. The SCS experienced two major periods of extensive El Niño‐related subsurface MHWs from 1997 to 2002 and 2008 to 2014, with MHWs reaching depths of 150 m and covering 70% of the upper 40 m. Strong El Niño events strengthen the western Pacific subtropical high, reducing summer monsoon winds, weakening coastal upwelling east of Vietnam, and increasing water temperatures. Regions of elevated eddy kinetic energy in the SCS suggest that significant mesoscale eddy activities are situated east of Vietnam. In addition, notable eddy heat transport was observed in the above region and west of the Luzon Strait in the upper 1,000 m. This may help to explain the high maximum and cumulative intensities of MHWs exceeding 100 m in the northern SCS.

Variability and Composition of Mysid Assemblages in a Northwest Iberian Estuary: Insights from a 10-Year Data Series

Long-term temporal studies have been used to assess the effects of climate change on mysid populations and their complex ecological interplay within heterogeneous ecosystems. This study is the first to investigate the mysid community in the Mondego estuary, western Portugal, for a decade, from 2003 to 2012. Monthly data collected from five stations along the estuary was used to investigate variations in mysid assemblage composition, patterns, phenology, and the interactions with environmental variables. Thirteen taxa were found in the assemblages. The community was dominated by Mesopodopsis slabberi, which was found in great numbers in the upper estuarine region. Praunus flexuosus and Schistomysis spiritus dominated the assemblages in the middle estuary, while Gastrossacus spinifer and Heteromysis formosa were very abundant at the mouth of the estuary. Overall, mysids were mostly present during autumn periods, when local environmental factors such as water temperature and chlorophyll-a concentrations influenced assemblage abundances. The high productivity of the system played a pivotal role in fostering greater species abundance. However, lower abundances were detected during warmer years, further evidencing changes in these key species’ communities under future climatic scenarios of increasing water temperatures.