Average Water Temperature Research Articles

КЛИМАТИЧЕСКИЕ ИЗМЕНЕНИЯ ТЕРМИЧЕСКОГО РЕЖИМА РЫБИНСКОГО ВОДОХРАНИЛИЩА

According to the data of the Rybinsk Hydrometeorological Observatory (HMO) and archival data of the Laboratory of Hydrology, Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, the seasonal variability of the main climate parameters, air temperature (Rybinsk HMO) and water temperature in the Rybinsk Reservoir have been studied at the modern stage of global warming (2001–2019). Over the period of 1976–2019, the rate of an increase in the average annual air temperature was 0.50°C /10 years in the littoral zone of the Rybinsk Reservoir. Changes in the timing of the onset and end of the climatic seasons of the year and an increase in their duration have been determined. It is found that during the modern period the average surface air temperature was higher than the climatic norm in all months of the year (1960–1990). During the growing season (conventionally May–October), its maximum increase was recorded in July, 1.5°C, May and September, 1.2°C. It is shown during the modern period of intensive global warming the average decadal water temperature in the spring, summer, and autumn seasons increased compared to the norm. The maximum positive anomalies were recorded in the second-third decade of May, 2.8–2.3°C and July, 2.0°C. According to observations at the standard stations, significant differences were recorded in water mass heating: in July in anomalously warm summer of 2010 the average water temperature was 27°C in the surface layer and 18.5°C in the near bottom layer; in the cold summer of 2017, the temperature was 18.5 and 16.0°C, respectively. The monitoring data on the water temperature in the reservoir indicate an increase in the number of years with anomalous thermal conditions as a result of climate change. The earlier temperature stratification of water masses (the end of May) and decrease in the difference in the temperature between the surface and near-bottom water layers have been observed.

Thermal application of composites of iron and magnesium in thermosyphon solar water heating system

AbstractA novel and low‐cost mixture of iron and magnesium have been synthesized and used as selective coatings for flat plate absorber in solar water heating system. The commercial black paint is fabricated with the mixture of composition Fe3(PO4)2·0.1Mg2P2O7·1.9 MgSO4(FPM3A). The composition of the coating mixture has been characterized by various analytical techniques. Thermal studies of these mixtures were accomplished using differential scanning calorimetry and thermo‐gravimetric analysis. From the thermal analysis, it has been observed that the mixtures can be used as thermal heat storage materials. The FPM3A‐modified black paint has been tested in a thermosyphon solar water heater prototype. The average water temperature and efficiency of the flat plate absorber with FPM3A‐modified black paint have increased by an average of 7.5° and around 12%, respectively, in comparison with that with commercial unprocessed black paint.

Long-term trend of heat waves and potential effects on phytoplankton blooms in Lake Qiandaohu, a key drinking water reservoir.

Global warming is increasing the frequency and duration of heat waves, which is defined as when air temperature exceeds a threshold for more than specific consecutive days. Ecosystem around the globe will be impaired by heat waves just like the exposures to dangerously high temperatures as a public health threat to human. However, the knowledge of the response of lake and reservoir ecosystem to heat waves is largely unknown although it has been argued that climate warming may increase the incidence of harmful algal blooms. We examined the long-term trend of heat waves and how the variability of phytoplankton biomass responds to lake heat waves on a deep reservoir (Lake Qiandaohu). Long-term (1980–2020) meteorological observation in the lake watershed showed a significant warming trend of 0.36 °C per decade for the yearly average of daily average air temperature and the yearly average of daily maximum air temperature of 18.32 °C was observed in 2016. Meanwhile, a significant increasing number of heat wave events lasting longer was observed, and Lake Qiandaohu suffered an unusually severe lake heat wave in summer 2016. Significant correlations were found between the yearly average of daily maximum air temperature and heat days, heat wave events, and heat wave days. Nuisance phytoplankton bloom was found in Lake Qiandaohu by high frequency observation and remote sensing monitoring in summer 2016. Remote sensing estimation from two Landsat 8 Operational Land Imager (OLI) images showed that the average chlorophyll a (Chla) was 7.45 ± 4.89 μg/L on July 18 before heat wave and 18.96 ± 0.98 μg/L on August 19 during the heat wave. Two heat wave events lasting from July 20 to August 2 and August 11 to 26 with average surface water temperature of 29.93 and 31.99 °C promoted two marked phytoplankton blooms with average Chla concentrations of 11.75 ± 4.08 and 10.53 ± 1.65 μg/L in the central lake region, respectively, as evidenced by high-frequency buoy data. These findings suggest that heat waves are likely to yield an increased threat of harmful algal bloom in freshwater ecosystems. With lake heat waves projected to increase in frequency, duration, and spatial extent with global climate change, more studies are needed to improve our understanding of lake heat waves and their potential effects on the species, communities, frequency of phytoplankton bloom, and also help providing advanced schemes of water quality management.

A Temporally Dynamic Gut Microbiome in Atlantic Salmon During Freshwater Recirculating Aquaculture System (RAS) Production and Post-seawater Transfer

Atlantic salmon aquaculture is undergoing an expansion of land-based recirculating aquaculture systems (RAS), especially for freshwater (FW) stages of production. Juvenile salmon undergo parr-smolt transformation, also known as smoltification and become pre-adapted to tolerate seawater (SW). One aspect requiring study is the development of microbial communities during this time, especially in RAS systems. Here we analyzed temporal changes in microbiome associated with the intestine in Atlantic salmon during smolt production in a commercial RAS production facility and followed the same cohort of fish post-seawater transfer (SWT), using 16S rRNA gene sequencing. Microbial diversity and richness showed an increase over time across FW production, but declined sharply and significantly 1-week post-SWT before re-establishing itself with a completely different community structure after 4 weeks. Core microbial taxa could be assigned to three distinct categories; (1) omnipresent, (2) salinity specific, or (3) transient. By including diet and water samples in the analyses, we classified true core taxa associated with the host, those associated with the diet, and transient cores associated with microbial communities in tank water. The rising trend observed in microbial richness in the water may be a consequence of a temporal increase in organic load while dominance of Vibrionaceae may be attributed to the higher temperatures maintained during RAS production and above average natural water temperatures post-SWT. Functional analysis suggests modulation of metabolic pathways post-SWT, but downstream impacts on fish growth and health in a commercial setting remain to be elucidated. A deeper understanding of the interplay between microbial composition and functionality can play a role in optimizing fish performance in tightly regulated RAS production.

Water physical factor analysis using aqua-modis image data to determine the tour ship route in Karimunjawa

Tourism development is closely related to the sustainable development that has been declared by the Government. The development of the tourism sector is in line with national development goals. The tourism development must be based on sustainability criteria, which means that development which was environmentally supported in the long-term as well as economically feasible, ethically fair, and socially fair to society. The condition of sea transportation (accessibility) of the Karimunjawa Islands people toward mainland (Java Island) was very limited, that was an average of 10 trips / week in and out of the Karimunjawa port, until the end of 2012. The Inter-island transportation was using fishing boats. This become an obstacle for economic activity, fulfilled the needs of coastal communities and the limited number of tourist visits. The purpose of this research was to identify the average range of water parameters for the route of the tour ship using aqua-modis and to analyze the average range of the waters suitability for determining the port of tour ship. The results of the study used aqua-modis image data, the range of average water temperature in Karimunjawa was ranged from 27 - 320C, the average depth measurement was ranged from 2 - 3 meters at high and low tide, while the average current was ranged from 0.8 - 1.0 m / s. The results of this study proved that the physical parameters of Karimunjawa water were very suitable for tour routes with the category of long vessel capacity with 12 m dimensions, 10 m width, 2.1 m and with an engine size of 5 GT.

Application of a Diatom Transfer Function to Quantitative Paleoclimatic Reconstruction — A Case Study of Yunlong Lake, Southwest China

Although diatom records from lake sediments have been used for quantitative paleoclimatic reconstruction, their validity and sensitivity have rarely been tested rigorously. At Yunlong Lake, an alpine lake in Southwest China, we studied the seasonal succession of diatom assemblages to produce a mean surface water temperature (MSWT) transfer function. In addition, based on the spatial distribution of surface diatom assemblages with water depth, we produced a diatom-water depth (WD) transfer function. Combined with the analysis of diatom assemblages in a sediment core (YL2013-A), changes in surface water temperature and water level over the last ∼100 years were quantitatively reconstructed using the diatom-based transfer functions. Comparison with records of regional meteorology and reservoir water capacity revealed that the diatom-based lake water level reconstruction is a sensitive indicator of short-term fluctuations in precipitation, and it also reflects a long-term stepwise rise in water level caused by the impounding and large-scale extension of the reservoir. In addition, the diatom-inferred MSWT is consistent with the changes in air temperature prior to large-scale human disturbance of the site. However, after the extension of the reservoir, although the regional air temperature continued to increase, the water temperature decreased substantially. This suggests that the large increase in lake water volume in the short term led to a decrease in the average water temperature, which in turn led to the occurrence of a diatom bloom in the cold season. The results demonstrate that diatom transfer functions based on modern observations of the same lake has a high environmental sensitivity and can be used for the quantitative reconstruction of regional climate change. Overall, our findings provide a foundation for the use of lake diatom records for quantitative paleoclimatic reconstruction on various timescales.

Energy and Water Savings during Backwashing of Rapid Filter Plants

This paper describes an analysis of the effects of adjusting the intensity of filter backwash to the water temperature. The consequences of the lack of such adjustment for the life of filter beds, the amount of water used for backwashing, the amount of energy used for backwashing and the quality of the first filtrate are presented. In order to determine the losses and profits resulting from controlling the intensity of backwash water depending on its temperature, an analysis was carried out at a water treatment plant in southern Poland. Laboratory measurements were used to determine the granulation and specific gravity of sand grains filling the filtration beds. On the basis of measurements on a semi-technical scale, the magnitudes of filter bed expansion were determined for average monthly wash water temperatures. They were first calculated from the Richardson–Zaki equation, using different formulae for the value of the exponent of the power in this equation. Due to significant differences in the density and shape of grains covered with a permanent deposit after several years of filter operation, a satisfactory match between the formulae known from the literature and the results of expansion measurements was not obtained. Therefore, an new formula for the bed expansion was developed based on the Richardson–Zaki equation. A good fit of this formula to the experimental results was obtained. Monthly average values of water temperature were compiled, and on this basis the required amount of backwash water and energy was computed. The computations were made for 25% of fluidized bed expansion. Possible energy and water savings were estimated, as well as further gains from keeping the required expansion of the porous bed constant regardless of the wash water temperature.

Comparison of Historical Water Temperature Measurements with Landsat Analysis Ready Data Provisional Surface Temperature Estimates for the Yukon River in Alaska

Water temperature is a key element of freshwater ecological systems and a critical element within natural resource monitoring programs. In the absence of in situ measurements, remote sensing platforms can indirectly measure water temperature over time and space. The Earth Resources Observation and Science (EROS) Center has processed archived Landsat imagery into analysis ready data (ARD), including Level-2 Provisional Surface Temperature (pST) estimates derived from the Landsat 4–5 Thematic Mapper (TM), Landsat 7 Enhanced Thematic Mapper Plus (ETM+), and Landsat 8 Thermal Infrared Sensor (TIRS). We compared in situ measurements of water temperature within the Yukon River in Alaska with 52 instances of pST estimates between June 2014 and September 2020. Agreement was good with an RMSE of 2.25 °C and only a slight negative bias in the estimated mean daily water temperature of −0.47 °C. For the 52 dates compared, the average daily water temperature measured by the USGS streamgage was 11.3 °C with a standard deviation of 5.7 °C. The average daily pST estimate was 10.8 °C with a standard deviation of 6.1 °C. At least in the case of large unstratified rivers in Alaska, ARD pST can be used to infer water temperature in the absence of or in tandem with ground-based water temperature monitoring campaigns.

Using mark-recapture techniques to assess factors affecting survival of fall stocked walleye Sander vitreus in two Iowa lakes

Stocking walleye Sander virteus is a common management technique to supplement populations where natural reproduction is limited. However, numerous factors can influence the survival of fall stocked walleye including environmental conditions, predation, and stocked walleye total length (TL), condition, and foraging ability. The relative effects of these factors on survival of stocked walleye are challenging to evaluate and rarely assessed simultaneously. Our objective was to determine factors that influence survival rates of stocked fingerling walleye (98−287 mm TL) from stocking until ice cover in two Iowa systems (East Okoboji and West Okoboji) during fall 2015, 2016, and 2017 using mark-recapture techniques. Each fall, roughly 4000 stocked walleye were implanted with passive integrated transponder tags, stocked across both systems, and recaptured via boat electrofishing. Cormack-Jolly-Seber recapture models estimated walleye weekly apparent survival was negatively related to the weekly average proportion of walleye recovered from predator diets (β = −0.89; 95 % credibility interval = −1.74 to −0.03) and positively related to weekly average water temperatures (β = 2.62; 95 % credibility interval = 1.04–4.21). At an average fall water temperature (13.2 ℃), mean walleye apparent survival was 0.83 (95 % credibility interval = 0.75–0.91) when no walleye were recovered from predator diets and declined to 0.54 (95 % credibility interval = 0.28–0.84) when walleye comprised 60 % of predator diets. Between 41–97 % of stocked walleye were lost to apparent mortality from stocking through ice-up and survival was influenced by post-stocking predation rather than walleye body size or condition. Thus, strategies that minimize predation following stocking may result in the greatest improvements in walleye stocking success.

Comfort of Domestic Water in Residential Buildings: Flow, Temperature and Energy in Draw-Off Points: Field Study in Two Danish Detached Houses

There is very little knowledge on the occupant actual hot water comfort (temperature and flow), usage practice, and routines (temporal and spatial distribution of hot water usage in a household). This paper describes the results from the total and hot water measurements in two Danish detached houses. The results show that, at the draw-off points, the temperature of 55 °C is never asked by the occupants, not even in the kitchen sink. The domestic water temperature differentiates depending on the function of the draw-off point, with the shower and kitchen taps being most energy- and water-intense. They constitute around 90% of the hot water use in the house. Shower units on average demand for highest temperature (i.e., 35.5 °C to 40.4 °C). Hand washing operates, on average, at temperature between 20.5 °C to 26.5 °C. Average water temperature at the taps located in utility room varies between 23 °C to 26 °C. These in-depth insight in the total and hot water use in two new-built low energy houses, can a) help building professionals designing more efficient hot water installations; b) enhance the research work on energy flexibility buildings by providing knowledge on most energy-intensive draw-off points; and c) facilitate district heating professionals in improving the network performance.

Phytoplankton community structural reshaping as response to the thermal effect of cooling water discharged from power plant

The increase of water temperature caused by the thermal effect of cooling water discharged from power plants has become a major environmental problem, especially its influence on phytoplankton community. The change of water temperature usually reshapes the structure of phytoplankton community. A research combining phytoplankton community and thermal discharge of power plants was conducted to identify the potential influences. Results indicated the average annual water temperature of the reservoir increased gradually by 5–11 °C because of the thermal discharge. Through annual diversity analysis, 139 species or taxa from 6 phyla (i.e., Bacillariophyta, Chlorophyta, Cyanobacteria, Euglenophyta, Dinoflagellata, and Cryptophyta) were found in different sampling sites, among which Bacillariophyta was the dominant community. Preliminary experimental results revealed the increasing temperature completely reshaped the phytoplankton community structure, especially during the cold season, and this was confirmed by the results of redundancy analysis. In addition, lots of thermophilic genera (i.e., Synedra, Nitzschia, and Navicula) were detected at sampling station 1 (Spt1) and sampling station 2 (Spt2) where the effect of thermal discharge was the most obvious. The increase in biomass and cell count of Bacillariophyta was the result of thermal effect, especially in cold season. Besides, consequences also revealed some environmental parameters (i.e., dissolved oxygen concentration, chlorophyll a concentration, and transparency) were affected by the thermal discharge. Chlorophyll a concentration exhibited a slow rising trend while dissolved oxygen concentration and transparency gradually decreased.

Demand response potential of district heating in a swimming hall in Finland

In this paper, the demand response of district heating for swimming pools and pool space air is proposed and applied in a swimming hall in Finland. Swimming halls have significant heat demands e.g., domestic hot water supply, space heating and pool water heating, and thus have much large heat storage capacity for the realization of district-heat based demand response. A dynamic building simulation tool IDA ICE was used to simulate whole swimming hall including pools and HVAC systems. In addition, a rule-based demand response algorithm which utilized dynamic district heat price was proposed and applied in the district heating control of the studied swimming hall. The results show that the large storing capacity of pool water promises the large amount of charged and discharged heat energy, and ensure the application of demand response of district heating in swimming hall. The application of demand response of district heating can increase the average pool water temperature from the normal setpoint of 26.5 °C to 27.3 °C. In addition, demand-response district heating control for the swimming pool water and pool space air decreases the total district heat costs of the swimming hall by 1.1%. During the repayment periods of 7 and 15 years, the energy cost savings and maximum cost of profitable investment for the demand response control are between 10 000 € and 20 000 €.

Daily, seasonal, and annual variability of temperature in streams inhabited by the endemic San Pedro Martir trout (Oncorhynchus mykiss nelsoni), in Baja California, Mexico, and the predicted temperature for the years 2025 and 2050

The present study measured the daily, seasonal, and annual variability of the water temperature of streams in which the endemic rainbow trout, Oncorhynchus mykiss nelsoni, is distributed on the western slope of the Sierra San Pedro Mártir, Baja California, Mexico, between 1996 and 2019. The seasonal thermal interval and daily duration of summer temperatures above the thermal threshold for this trout subspecies (≥ 28°C) were determined in streams at different elevations (553, 1,220, and 2,080 masl, or meters above sea level). Temperatures ≥ 28°C were recorded at the study site on the stream with the lowest elevation (San Antonio de Murillos Creek) over an accumulated 365 h between June and September 2014, with the maximum temperature recorded there, 30.66 °C, making it the site most vulnerable to climate change. At the San Antonio de Murillos Creek, the average water temperature predicted by three models (GFDL R30, HadCM3, and Mote) for the year 2025 would be a non-lethal temperature, < 28 °C, for trout at a minimum elevation of 491-511 masl, while this was predicted to be 545-701 masl for the year 2050. Predicted hourly water temperatures of 28°C (non-lethal) may occur at minimum elevations of 868-898 masl in 2025 and at 908-1028 masl in 2050, reducing a 21-23% and 23-31% its current altitudinal distribution range, respectively, thus avoiding its presence at the type locality (San Antonio de Murillos).

A collaborative voltage optimization utilizing flexibility of community heating systems for high PV penetration

The increasing penetration of photovoltaic generation exacerbates the risk of voltage violations in distribution networks. One viable tactic for increasing the flexibility of regional distribution networks is to use the thermal inertia of community heating systems (CHSs). However, the slow heat dynamics in the heating network brings difficulties in synchronous joint operation decisions of the integrated system. In this paper, we propose a novel power-to-temperature sensitivity model (PTSM), equating the whole CHS to a flexible electric load with thermodynamic characteristics. It denotes the direct relationship between the average water temperature change and the electric power consumed by ground-source heat pumps (GSHPs). A robust collaborative voltage optimization model is then developed from the perspective of power distribution system operators. The PTSM provides accurate prediction of CHS temperature variations to construct the operation constraints of GSHPs. This mixed integer programming problem is solved by the column-and-constraint generation algorithm. The test results of an actual residential community demonstrate that the PTSM can ensure the prediction errors of the CHS average temperature within ±0.4 °C in case of the optimal time resolution and aggregated heating load location. An IEEE 69-bus distribution network with several CHSs is studied to show that, the flexibility of CHSs can achieve an extra 17.25% reduction of the daily voltage deviation. The proposed method has significant advantages in computation time and robustness.

Numerical analysis of the heat pump water heater with immersed helically coiled tubes

With the aim of increasing the accuracy of the numerical results and reduce the computational time of simulation, our work focuses on the study of a heat pump water heater with immersed helically coiled tubes. The effects of the storage tank dimension and the copper coil pitch on the heating process were investigated by considering the evolution of temperature and velocity field of the waterside at the axial centerline of cylindrical water tank. The effects of varying the time step on the evolution of the average water temperature and velocities during the heating process are analyzed using Computational fluid dynamics (CFD) software package. The results showed that the effects of time step size on the results and clearly led to less accuracy. The validation of the numerical solutions was performed by comparing the simulated average water temperature with the results reported from the literature [1,2].It was found that the simulation and experimental results are in good agreement.

Impact of Water Temperature Changes on Water Loss Monitoring in Large District Heating Systems

This paper explores how water temperature changes in a district heating system (DHS) impact the monitoring of water losses. Water volume in DHS is constantly monitored, recorded, and replenished. The leakage and failure status of the DHS is often monitored through measuring the make-up water flow rate. In this paper, we present the methodology and a simplified model of the dynamics of the heating system operation, which was used to determine the profile of changes in the average temperature and density of water in the system. The mathematical model of the district heating network (DHN) was verified by comparing the results of simulation calculations, i.e., calculated values of the temperature of water returning to the heat source, with the measured values. Fluctuations in water temperature cause changes in the density and volume of water in the DHN, which affect the amount of water supplementing the system. This is particularly noticeable in a DHN with a large water volume. The study reports an analysis of measurement results of operating parameters of a major DHS in Poland (city of Szczecin). Hourly measurements were made of supply and return water temperature, water flow rate, and pressure throughout the whole of 2019. The water volume of the analyzed DHN is almost 42,000 m3 and the changes in water volume per hour are as high as 5 m3/h, representing 20–30% of the value of the make-up water flow rate. The analysis showed that systems for monitoring the tightness of the DHS and detecting failures, on the basis of measurements of the make-up water flow rate, should take into account the dynamics of water volume changes in the DHN.

Experimental Analysis on the Inactive region of Evacuated tube Solar Collector using Twisted Tapes

The evacuated tube type solar collector is used predominantly for water heating application in both residential and industrial scales. They found superior in thermal efficiency compared to other kind of solar collectors. All-glass evacuated solar collector is the simplest form of evacuated collector which found its major applications as passive flow solar water heaters for residential and industrial purposes. However, they have been affected with an inherent issue which is due to the inactive region formed at the bottom of the tubes. This paper addresses this issue with the help of twisted tubes, made-up of aluminum. The experimental results proved that the existence of twisted tapes accelerated the heat transfer within the inactive region and helped to maintain the uniform temperature inside the tube. The results proved that the water temperature at the inactive region was augmented up to 73°C with the help of twisted tapes, which was 31°C more than tubes without twisted tapes. Also, the twisted tapes enhanced the average temperature of tube water by the maximum of 10°C.

Field study of heating performance of three ground-source heat pumps in Canadian single-family houses

This paper is the second part of a two-part study on the performance of ground-source heat pumps (GSHPs) in single-family detached houses in Canada. In Part I the cooling performance of two GSHPs was tested, analyzed and evaluated over one cooling season. In this paper, the heating performance of three vertical closed-loop water-to-air GSHP systems installed in three new single-family detached houses in Innisfil (80 km north of Toronto, Canada) is monitored, analyzed and evaluated over one heating season. Results show that GSHP A, GSHP B and GSHP C were able to meet the peak heating load without using the auxiliary heating element. The seasonal coefficient of performance of heat pump of GSHP A, GSHP B and GSHP C is 4.2, 4.0 and 3.4, respectively, whereas the seasonal coefficient of performance of the GSHP system of GSHP A, GSHP B and GSHP C is 3.8, 3.4 and 2.7, respectively. GSHP A has the highest COP mainly because it is equipped with a variable speed compressor while GSHP B and GSHP C are equipped with two-stage compressors. The average temperature of water leaving the ground loop of GSHP A, GSHP B and GSHP C is 3.9 °C, 3.1 °C and 2.7 °C, respectively, where the average temperature of water leaving the ground loop varied by up to 6.3 °C throughout the heating season. The total power consumption and operating cost of GSHP A, GSHP B and GSHP C are less than conventional air-source heat pumps by up to 46%, 40% and 24%, respectively. It is concluded that GSHPs operate at high COPs without operational problems even in very cold climates if designed, sized and installed correctly.

Spatio-temporal Variation of Harmful Planktonic Microalgae and Cyanobacteria Along the Central Coast of Campeche, Southeastern Gulf of Mexico.

To describe the phytoplankton species composition, spatio-temporal distribution and habitats during different seasons along the central coast of the state of Campeche, Mexico, southeastern Gulf of Mexico, eight shallow-water (ca 1m) sites from the city of Campeche Southwest to Villamar were monitored monthly from September 2016 to June 2017 by taking water-bottle samples. Average water temperature varied between 22.2 and 30.9°C and average salinity between 26.6 and 35.0. The Kolmogorov-Smirnov test, the Bartlett's test and canonical correspondence analyses were applied. Sixteen potentially harmful microalgal species were found: five species are bloom-forming, nine are potentially toxic to humans, and two affect aquatic organisms. At all sampling sites, massive algal proliferations occurred in June (beginning of rainy season) caused by the dinoflagellates Heterocapsa sp. (2.6 × 105cells/L) and Blixaea quinquecornis (2.0 × 104 cells/L) and from October to March (windy season) by the cyanobacterium Trichodesmium sp. (2.6 × 105cells/L).

Conserved fatty acid profiles and lipid metabolic pathways in a tropical reef fish exposed to ocean warming – An adaptation mechanism of tolerant species?

Climate warming is causing rapid spatial expansion of ocean warm pools from equatorial latitudes towards the subtropics. Sedentary coral reef inhabitants in affected areas will thus be trapped in high temperature regimes, which may become the “new normal”. In this study, we used clownfish Amphiprion ocellaris as model organism to study reef fish mechanisms of thermal adaptation and determine how high temperature affects multiple lipid aspects that influence physiology and thermal tolerance. We exposed juvenile fish to two different experimental conditions, implemented over 28 days: average tropical water temperatures (26 °C, control) or average warm pool temperatures (30 °C). We then performed several analyses on fish muscle and liver tissues: i) total lipid content (%), ii) lipid peroxides, iii) fatty acid profiles, iv) lipid metabolic pathways, and v) weight as body condition metric. Results showed that lipid storage capacity in A. ocellaris was not affected by elevated temperature, even in the presence of lipid peroxides in both tissues assessed. Additionally, fatty acid profiles were unresponsive to elevated temperature, and lipid metabolic networks were consequently well conserved. Consistent with these results, we did not observe changes in fish weight at elevated temperature. There were, however, differences in fatty acid profiles between tissue types and over time. Liver showed enhanced α-linolenic and linoleic acid metabolism, which is an important pathway in stress response signaling and modulation on environmental changes. Temporal oscillations in fatty acid profiles are most likely related to intrinsic factors such as growth, which leads to the mobilization of energetic reserves between different tissues throughout time according to organism needs. Based on these results, we propose that the stability of fatty acid profiles and lipid metabolic pathways may be an important thermal adaptation feature of fish exposed to warming environments.