High Seawater Temperatures Research Articles

Seasonal Variability in Non-Structural Carbohydrate Content of Warm-Adapted Zostera noltei and Zostera marina Populations

Non-structural carbohydrates (NSCs) are energetic compounds that can be accumulated in tissues and mobilized during periods of unfavorable conditions to maintain the biological functions of plants. The balance of these biochemical compounds is controlled by environmental factors such as temperature and irradiance. Zostera noltei and Zostera marina find one of their southern distribution limits in southern Spain, where relatively high seawater temperatures are reached during summer (23–24 °C). To better understand the effects of elevated temperatures on the concentration of NSCs, we conducted a seasonal study at Cadiz Bay, representing warm-adapted populations of these species. Our results showed a bimodal pattern in both species, with the highest NSC content observed in December and June, followed by a depletion in March and August. In addition, the NSC content observed in the leaves of Z. noltei (71.26 ± 30.77 mg g−1 dry weight) was higher than in the rhizomes and roots (52.14 ± 38.86 mg g−1 DW). The observed patterns suggest that these species accumulated NSCs to cope with periods of unfavorable environmental conditions. We also suggest that the limited concentration of NSCs in Z. noltei rhizomes and roots indicates that this population may be suffering physiological stress.

High-resolution water temperature and salinity evolutions and associated drivers of the North Yellow Sea during the Late-Holocene

The mud deposit areas on continental shelf have developed in a relatively steady sedimentary condition with high sedimentation rates, thus rendering them ideal regions for exploring high-resolution paleo-sedimentary environment records. Since the sedimentary environment of the continental shelf is subject to the compound influence of multiple factors, the reconstruction of water salinity and temperature and comprehensive analysis of their response to global climate change remains challenging. Therefore, the present study characterized water salinity and temperature of the North Yellow Sea (NYS) using proxies, such as ratios of halogen elements of sediments and stable isotopic compositions of benthic foraminifera, and found the halogen elements of Cl in sediments was good proxy for water salinity. The evolutions of water salinity and temperature of the NYS for the past 3000 years were reconstructed, while the evolution stages and drivers of the sedimentary environment were explored. From approximately 3000 cal yr BP, the sea bottom salinity and temperature of the NYS were found to follow the same evolution trends predominantly consisting of the three stages: relatively low seawater salinity and temperature during 3000−2000 cal yr BP; relatively high seawater salinity and temperature during 2000−460 cal yr BP; and rapid changes of seawater salinity and temperature since 460 cal yr BP. The changes in seawater salinity and temperature of the NYS were largely driven by the East Asian winter monsoon (EAWM) as well as the influence of the Kuroshio Current. As the EAWM fluctuated, changes occurred in the flux of low temperature, low salinity coastal current water into the Yellow Sea, with concomitant changes in bottom temperature and salinity. Strengthening of the Kuroshio Current promoted the development of the Yellow Sea Warm Current, while the influx of warm, salty water into the Yellow Sea influenced the respective sea region. The abrupt global climate changes such as the “Little Ice Age” and the Medieval Warm Period first affected the East Asian monsoon, followed by the respective sea region.

Skeletal mineralogy of marine calcifying organisms shaped by seawater temperature and evolutionary history—A case study of cheilostome bryozoans

AbstractAimQuantify the contribution of environmental factors (water temperature, salinity and depth) and evolutionary history to varied skeletal mineralogy in calcifying marine organisms.LocationGlobal Ocean.Time periodPresent.Major taxa studiedOrder: Cheilostomatida; Phylum: Bryozoa.MethodsWe employed X‐ray diffraction (XRD) to analyse the skeletal mineral composition of 872 individual colonies, representing 437 bryozoan species, in terms of calcite/aragonite ratios. We integrated these data with equivalent published data, thus reaching 981 species, and applied linear models (LMs), generalized linear models (GLMs) and phylogenetic generalized least squares models (PGLSs) to investigate the influences of temperature, salinity, depth and phylogenetic history on the mineralogy of nearly 1000 cheilostome bryozoan species.ResultsCheilostome bryozoans vary considerably in their skeletal mineral composition: in our dataset 65% of the species possess purely calcite skeletons, 15% exclusively employ aragonite and 20% exhibit mixed (i.e. calcite and aragonite) mineralogies. Temperature is the predominant measured environmental factor influencing bryozoan skeletal mineralogy, accounting for 20% of its variability across species, when phylogenetic relatedness is unaccounted for. Bryozoans in lower latitudes, characterized by higher seawater temperatures, have higher aragonite concentrations. By accounting for phylogenetic structure using a subset of 87 species for which we have topological information, 40% of the observed mineralogical variability could be attributed to present‐day temperature. In contrast, depth and salinity played minor roles, explaining less than 1% of the mineralogical variation each.Main conclusionsThis study emphasizes the influence of evolutionary history on the mineralogical variability of calcifying organisms, even when it can be shown that a single environmental factor (temperature) explains a substantial amount of this variability. When confronted with changing temperature, calcifiers such as bryozoans are likely to respond in diverse ways, depending on the species, given their phylogenetic relatedness and the external conditions they meet.

Tropical Shrimp Biofloc Aquaculture within Greenhouses in the Mediterranean: Preconditions, Perspectives, and a Prototype Description

Biofloc technology (BFT) offers an innovative eco-friendly approach that is particularly applicable in shrimp farming. Penaeus vannamei is the most important seafood species in terms of global economic value. Nevertheless, its increasing global demand highlights the necessity for sustainable production of P. vannamei shrimps outside their native range, assuring the avoidance of genetic pollution risk. Towards this direction, the present study focuses on the feasibility of tropical shrimp species aquaculture in indoor systems evaluating BFT application in temperate zones. The achievability of P. vannamei cultivation inside greenhouses in temperate latitudes is thoroughly examined and a representative experimental biofloc setup for P. vannamei within a greenhouse in Northern Greece is demonstrated. Nevertheless, there are two major limitations, related to economy and ecology, namely the energy demand for high seawater temperature and the fact that most reared shrimps are non-indigenous species setting risk for genetic pollution, respectively. To overcome the former, energy-saving measures such as tank and greenhouse insulation in combination with a microclimate chamber construction were implemented to optimize water temperature at minimal cost. Concerning the latter, there is clear evidence that P. vannamei populations cannot be established in the Mediterranean, setting aside any environmental risk. Overall, based on the developed and tested pilot prototype, employment of optimal management practices, innovative manufacturing and clean energy alternatives, and the utilization of ecosystem services could reduce the environmental impact and maximize the profitability of biofloc operations. These actions could probably permit sustainable and economically viable farming of P. vannamei employing BFT within greenhouses in the Mediterranean.

Subsurface evolution of three types of surface marine heatwaves over the East Sea (Japan Sea)

Extremely high seawater temperatures (beyond the 90th percentile threshold) are a key characteristic of marine heatwaves (MHWs), which adversely affect human and marine ecosystems. It is important to characterize the MHWs in the East Sea (Japan Sea), a semi-enclosed deep basin connected to the outside seas/ocean by shallow and narrow straits, where the most rapid upper ocean warming has been reported in recent decades. Despite several reports on their rising frequency and severity, the characteristics, and underlying dynamics of East Sea MHWs (ESMHWs), particularly their subsurface evolution, remain poorly understood. In this study, we aimed to understand the subsurface evolution patterns of ESMHWs and the underlying mechanisms. Here, summer (June, July, and August) ESMHWs from four ocean reanalysis products were characterized after being verified against those from long-term (2000–2015) time-series observations near the east coast of Korea. We found the HYCOM reanalysis products is the best match with the observation, showing consistent evolution patterns with the ESMHWs in the observation, yielding high correlation coefficients (ranging from 0.7 to 0.9 at the surface), and low root-mean-square errors (3°C). Therefore, the HYCOM reanalysis is further used to characterize the subsurface evolution of surface ESMHWs. A rising frequency of annual mean and summer ESMHWs across the whole East Sea, with a maximum increasing rate of 1–2 events in 40 years and mean cumulative intensity of 5–9°C days decade-1. Three types (Types-A, -B, and -C) of subsurface evolution of ESMHW were commonly found in six sub-regions (where the increasing ESMHWs trends are maximum)—three in the western and three in the eastern parts. The three types are Type-A, which is surface-confined and short-lived with anomalous warm surface temperatures and cold subsurface temperatures; Type-B, characterized by warm anomalies propagating from the surface to the upper several meters with no subsurface cold anomalies; and Type-C, exhibiting anomalous warm temperatures at the upper 200 m. Although increased shortwave radiation, decreased wind speed, and thinned mixed layer commonly contribute to the formation of all three types, the relative role of the heat penetration into the layer below the mixed layer and dissipation mechanisms significantly differ among the types. Common ESMHW evolution features include mixed layer deepening, heat release to the atmosphere, and interactions between the surface mixed layer and deeper layers, while horizontal advection played a significant role only during the Type-C ESMHW events. The long-term trends in frequency, cumulative intensity, and duration of ESMHWs were discussed in terms of those in each type ESMHWs metrics along with long-term surface warming, subsurface cooling, and weakening currents in the six sub-regions. This study provides significant insights into surface and subsurface evolution of MHWs in this and other marginal seas in warming climate conditions.

Spatial and seasonal distribution of cyanobacteria Moorea species in coastal waters of Tanzania

This study aimed at identifying the presence of harmful cyanobacteria, detecting potential harmful algae toxins and their distribution in three seasons: December to February (hot dry season), March to May (rainy season), and June to November (cool dry season) of 2016. The samples were collected in five study sites in Tanzania: Tumbe, Chwaka, Paje, Bweleo in Zanzibar islands and Songosongo Island, mainland Tanzania, where skin irritation problems were observed in seaweed workers in an earlier study. The cyanobacteria from the Moorea genus were microscopically detected in the seawater, with highest concentrations in the months with the highest seawater temperature or hot dry season, than in the other two seasons. The concentration of Moorea species was significantly higher in Songosongo, Tanzania mainland than in Zanzibar Islands in all three seasons, corresponding to the higher level of nutrients of nutrients (PO43−, NO3− and NH4+) in the prior season. However, the concentrations were considered relatively low and thus not collected during an ongoing algal bloom. This is one of the first studies that detect Moorea sp. in Tanzanian seawater, and complementary studies including genome sequencing to characterize the species are warranted.

Effect of seawater temperature on the corrosion and cavitation erosion-corrosion resistance of Al10Cr28Co28Ni34 high-entropy alloy coating

The influence of temperature on the corrosion and cavitation erosion-corrosion (CE-C) behavior of Al10Cr28Co28Ni34 high-entropy alloy (HEA) coating in seawater was investigated. Interestingly, the corrosion resistance of the coating progressively diminished with an increase in seawater temperature, but the CE-C resistance demonstrated a trend of initial increase followed by a decrease. At higher seawater temperature, the resistance of the coating surface and the destructive force of the bubbles were respectively enhanced and weakened due to the increase in oxide film thickness, maximum bubble size, and collapse time, together leading to a reduction in the damage degree to the coating.

Relationships between high temperatures and Pacific Oyster disease and mortality in southeast Tasmania, Australia

Warm ocean temperature extremes, including marine heatwaves, have profound impacts on natural marine systems and aquaculture industries across the globe. In Tasmania, Australia, one aquaculture industry that has been significantly impacted by warm temperatures is Pacific Oyster (Magallana gigas, previously named Crassostrea gigas) farming, due to recurring outbreaks of the virus Ostreid herpesvirus 1. Such viral outbreaks are understood to be driven by high seawater temperatures, but the temperature threshold or duration for triggering disease and mortalities remain unclear. This study investigates the relationship between in-situ farm temperatures and oyster disease and mortality on the southeast coast of Tasmania, Australia using daily observations from three oyster growing areas (Pipe Clay Lagoon, Upper Pittwater, and Lower Pittwater) over three seasons. It is found that a 12-day averaged daily mean temperature is an excellent measure of the occurrence of high mortality. Specifically, a 21-day mean of 23.7 °C resulted in a 70% likelihood of high mortality, which is defined here as oyster losses of >15%. On the other hand, for lower levels of disease and mortality, a 12-day average of daily mean temperature gave the strongest relationship. A 12-day mean of 19.7 °C led to 70% probability of some disease and low mortality. The analysis also found in-situ farm temperature generally correlates well with remotely sourced temperature observations, indicating their potential usability for operational management. This study demonstrates a statistical risk analysis framework for the oyster farming industry, helping to improve the understanding of the detrimental impact of high temperatures on Pacific Oysters.

C, O, and Sr Isotope Compositions of Belemnites from the Bajocian–Bathonian of Arctic Siberia: Implications for Global Correlations and Paleogeographic Reconstructions

Abstract —The Middle Jurassic sedimentary strata of Siberia remain poorly studied chemostratigraphically. We contribute to the knowledge with pioneering C, O, and Sr isotopic data for carbonate material of belemnites from the Yuryung-Tumus Peninsula and the lower reaches of the Lena River, as a basis for comprehensive description of the north Siberian Bajocian and lower Bathonian. The obtained chemostratigraphic constraints, with new 87Sr/86Sr ratios and previous δ13C and δ18O estimates, also include data for the lower Bathonian in the Sokur section (Central Russia). Despite the limited amount of material, chemostratigraphy, along with the available biostratigraphic data, allows reliable correlation of the Boreal sections with the primary standard of Northwest Europe, which is impossible for these strata with any of the two methods alone. The δ13C, δ18О, and 87Sr/86Sr patterns correlate with the records of eustatic, climatic, tectonic, and paleogeographic events. The new δ18O data and the inferred paleotemperatures for the latest early Bajocian and the Bajocian/Bathonian boundary reveal two excursions of notable seawater warming near the Siberian Arctic coast, which were synchronous with episodes of global sealevel rise. It was presumably during the eustatic events that the N–S Komi Strait (first naming) opened twice in the territory of the Russian Plate. The strait connected the Boreal and Tethyan seas and thus changed the oceanic circulation patterns. Specifically, it opened a gateway for a warm current from the south to northern Siberia responsible for the high seawater temperatures recorded in the δ18О patterns of belemnites.

Body mass index does not decline during winter for the sedentary marine gastropod Crepidula fornicata.

Seasonal extremes in environmental conditions can substantially limit the growth and reproduction of animals. Sedentary marine animals are particularly susceptible to winter food limitation since they cannot relocate to more favourable conditions. In several temperate-zone bivalve species, substantial winter tissue mass declines have been documented; however, no comparable studies have been conducted on intertidal gastropods. Here, we investigate whether the suspension-feeding intertidal gastropod Crepidula fornicata also loses substantial tissue mass during the winter. We calculated body mass index (BMI) for individuals collected in New England at different times of year for 7 years to determine whether BMI declines through winter or varies seasonally. Remarkably, C. fornicata body mass did not decline significantly during winter months; indeed, a relatively poorer body condition was associated with higher seawater temperature, higher air temperature and higher chlorophyll concentration. In a laboratory experiment, we found that C. fornicata adults that were not fed for three weeks at 6°C (local winter seawater temperature) showed no detectable declines in BMI compared to field-collected individuals. Future studies should document energy budgets of C. fornicata and other sedentary marine animals at low winter seawater temperatures, and the impact of short-term elevated temperatures on those energy budgets.

Genome-wide association screening and MassARRAY for detection of high-temperature resistance-related SNPs and genes in a hybrid abalone (Haliotis discus hannai ♀ × H. fulgens ♂) based on super genotyping-by-sequencing

High seawater temperatures in summer often lead to high mortality in farmed abalone, which greatly increases the cost of farming. The hybrid abalone (Haliotis discus hannai ♀ × H. fulgens ♂, DF), is one of the main varieties of abalone cultured in Fujian Province, China, to resist the high temperature. In this study, the high-temperature resistance of DF abalones was assessed under 28 °C - 32 °C. 31 °C was applied in the subsequent screening experiments of high-temperature resistant individuals. A total of 614,321 single nucleotide polymorphisms (SNPs) were identified via super genotyping-by-sequencing (S-GBS), and 69 SNPs involved in 42 candidate genes were identified by genome-wide association study (GWAS). In addition, according to gene functional annotation, the locus with the lowest P value was screened within the threshold range (−log10P = 4.98296). The genotyping was verified by Sequenom MassARRAY, and 7 SNPs were proved to be related to high temperature resistance in DF population of 100 individuals. 7 candidate genes (fabp, e3rglg4, rgs2, tanc2x6, osbp1, arsb, and uch1) were identified near these SNPs. Finally, these candidate genes were further proved to be associated with the high-temperature resistance trait of DF by the analysis of differential expression genes between sensitive and tolerant individuals. These candidate genes involved regulatory mechanisms such as cell stability, protein repair, lipid metabolism and immune regulation. Notably, the mechanism by which the e3rglg4 gene was involved in the degradation of abnormally folded proteins of abalone under heat stress, corroborating the reliability of the results of GWAS and Sequenom MassARRA. These results complement the shortage of molecular markers for heat resistance of hybrid abalone, provide a reference for marker-assisted selection (MAS) and accelerate the development of heat-resistant abalone varieties.

Effect Of Sea Moisture Content On Corrosion Hull Of A Warship Made By PT Pal Indonesia

Seawater temperature ranges from -2 0 c to 300 c. Low temperatures are usually found in seawater around the poles and on the deep seabed. Meanwhile, high seawater temperatures are found in the sea in the Arid area. The Red Sea and Bab El Mandeb have temperatures of about 290 c to 300. Corrosion is a subject matter that concerns various disciplines, or in other words, it connects elements of physics, chemistry, metallurgy, electronics and engineering. This study uses the literature review study method to collect, identify, evaluate the effect of seawater content on the corrosion of the hulls of warships made by PT Pal Indonesia. An effective corrosion control strategy should be selected with the selection of suitable coatings for the marine environment. Hull plating with paint has a special function to protect the construction of the hull, especially those located below the waterline and the construction of the ship above the waterline.

Correlation of High Seawater Temperature with Vibrio and Shewanella Infections, Denmark, 2010-2018.

During 2010-2018 in Denmark, 638 patients had Vibrio infections diagnosed and 521 patients had Shewanella infections diagnosed. Most cases occurred in years with high seawater temperatures. The substantial increase in those infections, with some causing septicemia, calls for clinical awareness and mandatory notification policies.

Can marine heatwaves affect the fatty acid composition and energy budget of the tropical fish Zebrasoma scopas?

Marine heatwaves (MHWs) are extreme weather events featuring abnormally high seawater temperature, and expected to increase in frequency, duration and severity over this century. The impacts of these phenomena on physiological performance of coral reef species require understanding. This study aimed to evaluate the effects of a simulated MHW (category IV; ΔT = +2 °C, 11 days) (after exposure and 10-day recovery period) on fatty acid (FA) composition (as a biochemical indicator) and energy budget (i.e., growth, G, excretion (faecal, F and nitrogenous losses, U), respiration, R and food consumption, C) of a juvenile tropical surgeonfish species (Zebrasoma scopas). Significant and different changes were found under MHW scenario for some of the most abundant FA and respective groups (i.e., an increase in the contents of 14:0, 18:1n-9, ΣMonounsaturated (ΣMUFA) and 18:2n-6; and a decrease in the levels of 16:0, ΣSaturated (ΣSFA), 18:1n-7, 22:5n-3 and ΣPolyunsaturated (ΣPUFA)). The contents of 16:0 and ΣSFA were also significantly lower after MHW exposure compared to control (CTRL). Additionally, lower feed efficiency (FE), relative growth rate (RGR) and specific growth rate in terms of wet weight (SGRw), as well as higher energy loss for respiration were observed under MHW exposure conditions in comparison with CTRL and MHW recovery period. The energy proportion channelled for faeces dominated the mode of energy allocation, followed by growth in both treatments (after exposure). After MHW recovery, this trend was reversed, and a higher percentage was spent for growth and a lower fraction for faeces than in the MHW exposure period. Overall, FA composition, growth rates and energy loss for respiration of Z. Scopas were the physiological parameters most influenced (mainly in a negative way) by an 11-day MHW event. The observed effects in this tropical species can be exacerbated with increasing intensity and frequency of these extreme events.

Marine protected areas' positive effect on fish biomass persists across the steep climatic gradient of the Mediterranean Sea

Abstract The positive effect of fully protected marine protected areas (MPAs) on marine biodiversity, and specifically on fishes, has been widely documented. In contrast, the potential of MPAs to mitigate the impact of adverse climatic conditions has seldom been investigated. Here, we assessed the effectiveness of MPAs, quantified as increasing fish biomass, across wide geographic and environmental gradients across the Mediterranean Sea. We performed underwater visual surveys within and outside MPAs to characterize fish assemblages in 52 rocky reef sites across an extent of over 3300 km. We used the steep spatial temperature gradient across the Mediterranean as a ‘space‐for‐time’ substitution to infer climate‐driven temporal changes. We found that, as expected, Mediterranean MPAs increased fish biomass. At the same time, higher seawater temperatures are associated with decreased fish biomass, changes in species composition, and shifts towards more thermophilic species. Importantly, we found that the rate of decrease in fish biomass with temperature was similar between protected and fished sites. Taken together, these results suggest that the capacity of MPAs to harbour higher fish biomass, compared to surrounding areas, is maintained across a broad temperature range. At the same time, MPAs will not be able to offset larger‐scale biotic alterations associated with climate change. Policy implications. Our results suggest that sustained warming will likely reduce fish biomass in the Mediterranean Sea and shift community structure, requiring more conservative targets for fishery regulations. At the same time, protection from fishing will remain an important management tool even with future high‐water temperatures, and MPAs are expected to continue to provide local‐scale benefits to conservation and fisheries.

Effects of high temperature stress on conchospore germination and early seedling development ofPyropia haitanensis

Pyropia haitanensis is one of the main cultivated macroalgae in China. In recent years, the cultivation of P. haitanensis conchospores in seawater is conducted in advance to obtain earlier harvest. However, the high seawater temperature may exert negative impacts on the algae. Seven temperature conditions (25, 26, 27, 28, 29, 30 and 31°C) were set in the culture of P. haitanensis to investigate the effects of temperature on the conchospore germination and early seedling development of P. haitanensis. The results showed that conchospore germination rate decreased with the increase in temperature. The temperatures of 25 and 26°C were suitable for P. haitanensis conchospore germination. Higher temperature (27°C) promoted conchospore germination on the 1st and 2nd days but decreased the germination considerably on the 3rd day. The conchospore mortality rate reached 89% after culture at high temperature (31°C) for 4 days. Additionally, the development of conchospore seedlings was normal, the total number of cells increased, and the survival rate was high (53%–90%) in the range of 25–29°C. At 25°C, the absolute growth rate of seedlings was as high as 302%. However, the development slowed down and the absolute growth rate decreased with the increase in temperature. At 30 and 31°C, seedling development was abnormal or even ceased, the survival rate was as low as 20% (30°C) and 11% (31°C), and the absolute growth rates were negative under the two conditions. The mortality of seedling was remarkably higher at 31°C than at other temperatures and gradually increased with the increase in temperature (25–31°C). And, the potential mechanisms underlying high temperature damages were analysed. Therefore, the temperature range suitable for the seedling collection and cultivation of P. haitanensis conchospore is 25–29°C.

Reproductive Biology of the Sea Cucumber Holothuria mammata (Echinodermata: Holothuroidea).

Simple SummaryHolothuria mammata is one of the sea cucumber species with high commercial value and great demand in Asian markets; however, the existent knowledge about the biology and ecology of this species is scarce. This study aims to describe the reproductive cycle of H. mammata in a coastal area of southwest Portugal through monthly collections of biometric data and environmental data. The sex ratio of H. mammata was 1:1.2 (male:female), and the size at first sexual maturity was 142 mm for males and 167 mm for females. Gonad development began when days had a shorter photoperiod and lower seawater temperature, and spawning occurred later, with longer photoperiod and higher seawater temperature and chlorophyll-a concentrations. This study is essential to increase the biological and ecological knowledge of the populations of H. mammata, create conditions for the domestication of broodstock in captivity and create precise measures for the conservation of ecosystems.Holothuria mammata is one of the most valuable species of sea cucumber, as well as one of the main target species harvested in the Mediterranean and NE-Atlantic regions. This study aims to describe the reproductive cycle of H. mammata in a coastal area of southwest Portugal. Monthly samplings were carried out for 19 months, with the concomitant collection of environmental data and biometric data. H. mammata had a sex ratio of 1:1.2 (male:female) and a size at first maturity of 142 mm for males and 167 mm for females. The gonadosomatic index (GI) peaked between April and May for both sexes. Gonad development started when days had a shorter photoperiod (9 to 13 h of sunlight) and lower seawater temperature (<15 °C), and spawning occurred later, with longer photoperiod (13 to 15 h of sunlight) and higher seawater temperature (>15 °C) and chlorophyll-a concentrations. The development of new studies to increase the biological and ecological knowledge of the populations of H. mammata is essential to create conditions for the domestication of broodstock in captivity, to allow the development of fishing regulations based on informed decisions and to create precise measures for the conservation of ecosystems.

Seasonal Pattern of the Effect of Slurry Ice during Catching and Transportation on Quality and Shelf Life of Gilthead Sea Bream

The objective of the present study was the evaluation of the effect of slurry ice, as an alternative cooling medium during harvesting and transportation, on the quality parameters (e.g., microbiological stability, sensory attributes, physicochemical changes) and shelf life of fish. The effect of seasonal variability of seawater temperature on fish preservation using the tested cooling media was also investigated. Gilthead sea bream (Sparus aurata) was slaughtered and transported in different mixtures of conventional flake ice and slurry ice for 24 h. Three mixtures of ice were tested as T: slaughtered in flake ice and transported in flake ice (control), TC: slaughtered in slurry ice and transported in flake ice, T50: slaughtered and transported in slurry ice 50%–flake ice 50%. Samples were subsequently stored isothermally at 0 °C for shelf-life evaluation. Three independent experiments were performed at three different periods, i.e., January, April, and September, referring to a sea water temperature range of 13.3–26.8 °C. Higher sea water temperatures at catching led to lower microbial growth rates and proteolytic enzyme activities and longer shelf life of refrigerated whole fish. The partial replacement of conventional flake ice with slurry ice improved the quality and extended the shelf life of fish at 0 °C by 2–7 days. The results of the study support that the use of slurry ice may enable better quality maintenance and significant shelf-life extension of whole gilthead sea bream.

Seagrass Meadows under the Changing Climate: A Review of the Impacts of Climate Stressors

Seagrass meadows provide important ecological functions, particularly by serving as carbon sinks and breeding grounds for marine species. Climate change has threatened seagrass communities, causing their replacement, loss and increased vulnerability. This review examined scholarly articles published between 2010-2021 to comprehensively present the impacts of climate change on seagrass meadows. It shows that ocean warming negatively affects seagrass communities by favouring communities of lower structuring capacities, thus reducing the effectiveness of their ecological functions. Ocean warming also promotes the propagation and spread of invasive species, and changes the trophic structures leading to further loss of seagrasses of value. Higher seawater temperature is associated with shoot mortality and retarded growth of certain seagrasses. Sea level rise causes more wave energy to be received by coastal seagrass communities, thus, creating more damage to the communities. Deepening sea limits light penetration and alters distribution of seagrass meadows. Carbon dioxide enrichment of seawater increases photosynthetic rate of seagrasses but ocean warming and acidification counteract this beneficial effect. Carbon dioxide enrichment affects different seagrass species and different parts of a seagrass species differently, and, where beneficial to seagrass communities, could enhance their ecological services. Temperature extremes could kill seagrasses while marine heatwaves and flooding could act synergistically to increase carbon demand of certain seagrasses and unfavourably change their biomass. These impacts are often aggravated by anthropogenic activities. This review calls for more studies and conservation efforts to understand the impacts of climate change on seagrass communities and future-proof them against the changing climate.

The Effect of Thermal Stress on the Physiology and Bacterial Communities of Two Key Mediterranean Gorgonians.

ABSTRACTGorgonians are important habitat-providing species in the Mediterranean Sea, but their populations are declining due to microbial diseases and repeated mass mortality events caused by summer heat waves. Elevated seawater temperatures may impact the stress tolerance and disease resistance of gorgonians and lead to disturbances in their microbiota. However, our knowledge of the biological response of the gorgonian holobiont (i.e., the host and its microbiota) to thermal stress remains limited. Here, we investigated how the holobiont of two gorgonian species (Paramuricea clavata and Eunicella cavolini) are affected throughout a 7-week thermal stress event by following both the corals’ physiology and the composition of their bacterial communities. We found that P. clavata was more sensitive to elevated seawater temperatures than E. cavolini, showing a greater loss in energy reserves, reduced feeding ability, and partial mortality. This lower thermotolerance may be linked to the ∼20× lower antioxidant defense capacity in P. clavata compared with E. cavolini. In the first 4 weeks of thermal stress, we also observed minor shifts in the microbiota of both species, suggesting that the microbiota likely plays a limited role in thermal acclimation of the holobiont. However, major stochastic changes occurred later on in some colonies, which were of a transient nature in E. cavolini, but were linked to partial colony mortality in P. clavata. Overall, our results show significant, but differential, effects of thermal stress on the holobionts of both E. cavolini and P. clavata and predict potentially severe impacts on gorgonian populations under future climate scenarios.IMPORTANCE In the Mediterranean Sea, the tree-shaped gorgonian corals form large forests that provide a place to live for many species. Because of this important ecological role, it is crucial to understand how common habitat-forming gorgonians, like Eunicella cavolini and Paramuricea clavata, are affected by high seawater temperatures that are expected in the future due to climate change. We found that both species lost biomass, but P. clavata was more affected, being also unable to feed and showing signs of mortality. The microbiota of both gorgonians also changed substantively under high temperatures. Although this could be linked to partial colony mortality in P. clavata, the changes were temporary in E. cavolini. The overall higher resistance of E. cavolini may be related to its much higher antioxidant defense levels than P. clavata. Climate change may thus have severe impacts on gorgonian populations and the habitats they provide.