Increasing Seawater Temperature Research Articles

The investigation on stress mechanisms of Sepia esculenta larvae in the context of global warming and ocean acidification

Sepia esculenta is a tasty and nutritious cephalopod. But the trend toward global warming is accelerating with massive emissions of greenhouse gases. An increase in seawater temperature and a decrease in pH are a great challenge for artificial breeding and culture of S. esculenta. In this study, we investigated the contingency mechanism of S. esculenta larvae under both high temperature and low pH conditions by transcriptome analysis. A total of 1235 DEGs were identified. functional enrichment analysis results suggest that high temperature and low pH conditions led to malignant proliferation in exceptional cells of S. esculenta larvae. A comprehensive analysis of the KEGG signaling pathway and protein-protein interaction network (PPI) identified sixteen key genes under both high temperature and low pH conditions. The three genes with the highest quantities of interactions or involved in more KEGG signaling pathways were identified as hub genes affecting normal physiological processes in S. esculenta. In this study, the effects of global warming and ocean acidification on the metabolism and immunity of S. esculenta larvae were preliminarily investigated to provide necessary help for S. esculenta captive breeding in the face of global climate change.

In situ decrease in rhodolith growth associated with Arctic climate change.

Rhodoliths built by crustose coralline algae (CCA) are ecosystem engineers of global importance. In the Arctic photic zone, their three-dimensional growth emulates the habitat complexity of coral reefs but with a far slower growth rate, growing at micrometers per year rather than millimeters. While climate change is known to exert various impacts on the CCA's calcite skeleton, including geochemical and structural alterations, field observations of net growth over decade-long timescales are lacking. Here, we use a temporally explicit model to show that rising ocean temperatures over nearly 100 years were associated with reduced rhodolith growth at different depths in the Arctic. Over the past 90 years, the median growth rate was 85 μm year-1 but each °C increase in summer seawater temperature decreased growth by a mean of 8.9 μm (95% confidence intervals = 1.32-16.60 μm °C-1, p < .05). The decrease was expressed for rhodolith occurrences in 11 and 27 m water depth but not at 46 m, also having the shortest time series (1991-2015). Although increasing temperatures can spur plant growth, we suggest anthropogenic climate change has either exceeded the population thermal optimum for these CCA, or synergistic effects of warming, ocean acidification, and/or increasing turbidity impair rhodolith growth. Rhodoliths built by calcitic CCA are important habitat providers worldwide, so decreased growth would lead to yet another facet of anthropogenic habitat loss.

Transcriptomic WGCNA analyses reveal endoplasmic reticulum response of Patinopecten yessoensis under acute heat stress

Patinopecten yessoensis is one of the most important aquaculture shellfish worldwide. As a cold-water species, the increasing seawater temperatures due to global warming have been a great challenge for P. yessoensis. Understanding the response mechanism of P. yessoensis to high temperatures is essential to the genetic breeding of heat-tolerant varieties. In this study, histological, cytological and transcriptomic analyses were performed on the gill tissues of P. yessoensis under different acute heat stresses (temperature: 22 °C, 25 °C, 28 °C; time: 6 h, 36 h). A total of 10,601 differentially expressed genes (DEGs) were detected, among which, 141 DEGs were shared by all heat-stressed groups. Weighted gene co-expression network analysis (WGCNA) identified three modules (M1, M2 and M3) that were significantly correlated with heat stress. Functional enrichment analysis revealed that heat stress probably caused serious endoplasmic reticulum (ER) stress in gill cells, with many associated GO terms and KEGG pathways markedly enriched. Notably, the protein processing in ER pathway probably played a key role in the response to heat stress; this pathway was upregulated and was the most enriched in all heat-stressed groups, as well as in the M1 and M2 modules. DEGs from this pathway participated in different processes of the ER stress response, alleviating ER stress by upregulating the protein correct folding, ER-associated degradation (ERAD) and unfolded protein response (UPR) processes. Excessive ER stress induced apoptosis via the UPR, and excessive apoptosis resulted in tissue injury as observed by histological and TUNEL assays. Further, numerous Hsps were upregulated in all heat-stressed groups, and some members were identified as hub genes, including BiP, NEF, Hsp70 and Hsp90. These genes may perform crucial functions during heat stress as molecular chaperones. This study elucidates the key molecular components of the ER stress response to heat stress in scallops. The findings provide new insights into the adaptation mechanisms of molluscs to environmental stress.

Too Hot to Handle: Effects of Water Temperature on the Early Life Stages of Gongolaria barbata (Fucales)

Gongolaria barbata plays a crucial role as a habitat-forming Fucales species in the Mediterranean Sea, thriving in shallow, sheltered coastal regions, where it exhibits optimal growth in a temperature range of 10 to 25 °C. In the northern Adriatic Sea, a semi-enclosed part of the Mediterranean, there has been a remarkable increase in seawater temperatures in recent decades, often exceeding 28 °C in summer. These high temperatures pose a significant threat to the vulnerable early life stages of G. barbata. This study delves into the effects of four temperatures (15, 18, 24, and 28 °C) on the growth of G. barbata over its first 16 days, closely monitoring mortality, deformities, and overall survival. Our experiments reveal that higher temperatures can result in deformities and increased mortality of germlings. Notably, a temperature of 28 °C resulted in the death of all germlings within the first week, whereas those exposed to 24 °C survived until the second week, albeit with significant deformities prior to death. In contrast, germlings cultivated at 15 and 18 °C exhibited normal development with minimal deformities. These results highlight the susceptibility of the early life stages of G. barbata to temperature-induced stress and provide valuable insights into the potential consequences of rising seawater temperatures in the Mediterranean.

The present and future contribution of ships to the underwater soundscape

Since the industrial revolution the ocean has become noisier. The global increase in shipping is one of the main contributors to this. In some regions, shipping contributed to an increase in ambient noise of several decibels, especially at low frequencies (10 to 100 Hz). Such an increase can have a substantial negative impact on fish, invertebrates, marine mammals and birds interfering with key life functions (e.g. foraging, mating, resting, etc.). Consequently, engineers are investigating ways to reduce the noise emitted by vessels when designing new ships. At the same time, since the industrial revolution (starting around 1760) greenhouse gas emissions have increased the atmospheric carbon dioxide fraction x(CO2) by more than 100 μmol mol-1. The ocean uptake of approximately one third of the emitted CO2 decreased the average global surface ocean pH from 8.21 to 8.10. This decrease is modifying sound propagation, especially sound absorption at the frequencies affected by shipping noise lower than 10 kHz, making the future ocean potentially noisier. There are also other climate change effects that may influence sound propagation. Sea surface warming might alter the depth of the deep sound speed channel, ice melting could locally decrease salinity and more frequent storms and higher wind speed alter the depth of the thermocline. In particular, modification of the sound speed profile can lead to the appearance of new ducts making specific depths noisier. In addition, ice melting and the increase in seawater temperature will open new shipping routes at the poles increasing anthropogenic noise in these regions. This review aims to discuss parameters that might change in the coming decades, focusing on the contribution of shipping, climate change and economic and technical developments to the future underwater soundscape in the ocean. Examples are given, contrasting the open ocean and the shallow seas. Apart from the changes in sound propagation, this review will also discuss the effects of water quality on ship-radiated noise with a focus on propeller cavitation noise.

A circle that closes. First report of Echinolittorina punctata (Gmelin, 1791) (Gastropoda; Littorinidae) for the coasts of Sardinia

Echinolittorina punctata (Gmelin, 1791), a thermophilic supralittoral species, was historically distributed along the Atlantic coasts from southern Spain to Senegal, and in the southern and eastern sectors of the Mediterranean. In the latter sea it has spread its range northwards only in recent years, moving up the Tyrrhenian coasts of Italy up to Tuscany, the Adriatic ones up to Croatia, and the southern coasts of Western Europe up to France. Sardinia, in an intermediate position between the Italian Tyrrhenian coasts and the southern Spanish and French ones, both recently colonized by E. punctata, presented itself as a foreseeable new settlement area. The discovery of some populations of this species in north-western Sardinia, along the coasts of the municipality of Porto Torres, represents the first report for Sardinia. It fills the last missing range gap for this species to be defined as widely distributed in the Mediterranean. The expansion of this species further northward in the Mediterranean seems linked to the general increase in sea water temperatures resulting from climate change.

Effects of temperature and microbial disruption on juvenile kelp Ecklonia radiata and its associated bacterial community

Ocean warming can affect the development and physiological responses of kelps, and under future climate change scenarios, increasing seawater temperatures pose a major threat to these habitat-forming species. However, little is known about the effects of warming on epiphytic bacterial communities and how an altered microbiome may interact with temperature stress, affecting the condition and survival of kelp, particularly of the potentially more vulnerable early life stages. Here, we tested the effects of thermal stress on the growth and physiological responses of juvenile kelp Ecklonia radiata in which their epiphytic bacterial community was experimentally disrupted using antimicrobials, simulating dysbiosis. We hypothesized that, under thermal stress (23°C, simulating a extreme scenario of ocean warming in Tasmania), kelp with a disrupted bacterial community would be more strongly affected than kelp with an undisrupted microbiome or kelp under ambient temperature (14°C) but with a disrupted microbiota. Thermal stress reduced growth, increased tissue bleaching and negatively affected net photosynthesis of kelp. In addition, a substantial change in the epiphytic bacterial community structure was also found under thermal stress conditions, with an increase in the abundance of potentially pathogenic bacterial groups. However, microbial disruption did not act synergistically with thermal stress to affect kelp juveniles. These results suggest that effects of elevated temperature on juvenile kelps is not microbially-mediated and that juveniles may be less susceptible to disruptions of their microbiome.

Increased seawater temperature triggers thermal, oxidative and metabolic response of Ostrea edulis, leading to anaerobiosis

Bivalves are among the marine organisms most influenced by climate change. Despite the flat oyster's Ostrea edulis high economic value, its culture is developed on a very small scale, since this species possesses a strong susceptibility to abiotic stressors. Due to climate change, temperature is one of the most critical environmental parameters for the welfare of the Mediterranean basin's marine inhabitants. The present study's purpose was to investigate the physiological performance of the Mediterranean's native O. edulis as it faces exposure to different temperatures. Since juveniles are more susceptible to abiotic stressors, this experimental procedure was focused on young individuals. The seawater temperatures studied included a standard control temperature of 21 °C (often observed in several marine areas throughout the Mediterranean), as well as increased seawater temperatures of 25 °C and 28 °C, occasionally occurring in shallow Mediterranean waters inhabited by bivalve spat. These were selected since the tissues of O. edulis becomes partly anaerobic in temperatures exceeding 26 °C, while cardiac dysfunction (arrhythmia) emerges at 28 °C. The results demonstrate that temperatures above 25 °C trigger both the transcriptional upregulation of hsp70 and hsp90, and the antioxidant genes Cu/Zn sod and catalase. Enhancement of thermal tolerance and increased defense against increased ROS production during thermal stress, were observed. As the intensity and duration of thermal stress increases, apoptotic damage may also occur. The increased oxidative and thermal stress incurred at the highest temperature of 28 °C, seemed to trigger the switch from aerobic to anaerobic metabolism, reflected by higher pepck mRNA expressions and lower ETS activity.

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.

Successive responses of three coral holobiont components (coral hosts, symbiotic algae, and bacteria) to daily temperature fluctuations

Corals and their associated microbiota form a “holobiont,” which includes symbiotic algae and other associated microbiota dominated by bacteria. The composition of holobiont is influenced by various environmental factors, such as increasing sea water temperatures. Previous studies of the effects of temperature changes on coral physiology and associated bacterial communities have been conducted based on stable water temperatures set by mean temperatures, or by slowly increasing/decreasing temperatures. However, the daily temperature fluctuations that corals experience in nature are not stable. The current understanding of the effects of large daily temperature fluctuations on coral and associated bacterial community dynamics is limited. Hence, we conducted a four-week tank experiment using different large daily temperature fluctuations (±5 °C and ±7 °C) accompanied by continuous warming conditions (26 °C to 29 °C) to investigate the effects on two common reef-building corals, Stylophora pistillata and Pocillopora acuta. During the experiment, the activity of coral host catalase and superoxide dismutase were measured, the photosynthetic ability of symbiotic algae was recorded, and the variation in bacterial communities was analyzed using the V6-V8 region of 16S rDNA. According to the results, different parts of the holobionts of two coral species exhibited varying response rates to the continuous warming conditions and diurnal temperature fluctuations. Additionally, it was found that diurnal temperature fluctuations may mitigate the heat stress on the host and reduce the changes in bacterial response to warming. Therefore, it is suggested that the holobionts of different coral species may adopt different adaptation and survival strategies in response to diurnal temperature fluctuations and warming. Finally, based on the response of these two coral species under the conditions of diurnal temperature fluctuations and continuous warming, Acinetobacter and Rhodobacteraceae were identified as potential indicator coral-associated bacteria. This is the first study to investigate the tripartite dynamic response of coral, symbiotic algae and bacteria to daily temperature fluctuations.

Effect of NaOCl and ClO2 on seawater desalination using reverse osmosis with cartridge filtration as the pretreatment during the algal bloom

Increased seawater temperature leads to harmful algal blooms (HABs), which releases toxic materials and extracellular polymeric substances (EPS) that are harmful to both humans and the environment. Reverse osmosis (RO) with cartridge filter (CF) as the pretreatment process is often used for desalination process. However, the EPS causes severe fouling on the CF, and RO membrane. Disinfectants, such as NaOCl and ClO2, are commonly used to remove biofouling, because they can oxidize and kill microorganisms. Therefore, our study aims to utilize NaOCl and ClO2 during the CF-RO process to minimize the algal growth within the system and minimize the fouling induced by EPS. Results from this study show that CF can remove more than 50% of protein and 14% of polysaccharides but is not effective in removing toxins. However, with disinfectants, toxic materials were completely oxidized. Improved removal of EPS with CF improved overall performance. The flux reduction in RO process without disinfection was over 60%, however, the flux decline was about 44% and 10% with NaOCl and ClO2, respectively. Both disinfectants were found to be effective, however use of ClO2 is recommended because it is less damaging the membrane, yet more effective in enhancing the performance.

The climate crisis affects Mediterranean marine molluscs of conservation concern

AbstractAimThe Mediterranean Sea is a hotspot of endemism and it is warming at two to three times the rate of the global ocean. The continental masses that surround it constrain species range shifts. Therefore, as seawater temperature increases, distributions of marine species may contract into few small cooler refugia, with consequent risk of extinction from range contraction and fragmentation, particularly for endemics. We assess this risk for 15 molluscs of conservation concern occurring in the Mediterranean Sea. Invertebrates have been rarely assessed so far, despite their diversity and their importance for ecosystem functioning.LocationThe Mediterranean Sea and Eastern Atlantic Ocean.MethodsWe used ensemble species distribution models to project the future range of our target species and assess their IUCN Red List status.ResultsAs hypothesized, our models predicted major range shifts, contractions and fragmentation in the Mediterranean Sea for all species. Under moderate emission scenarios such as RCP4.5, up to 12 of the 15 target species will be eradicated from the eastern and southern warmer sectors. Under severe emission scenarios such as RCP8.5 and by the end of the century, we predict the global extinction of the endemic Patella ferruginea and Pinna nobilis. Non‐endemic species may buffer range loss in the Mediterranean with range gains in the Atlantic Ocean. Still, we predict that only a single species, Zonaria pyrum, will have marginal total range gains in future climate warming scenarios.Main conclusionsEight species will become threatened and the fate of Patella ferruginea and Pinna nobilis contrasts the belief that marine species are less prone to extinction than continental species under a warming climate.

Life history traits and historical comparison of blue whiting (Micromesistius poutassou) growth performance from the western Pomo/Jabuka Pits area (central Adriatic Sea)

Although fishing is considered the primary cause of the decline in fish populations, increasing evidence of the significant role of climate change has been provided recently in the Mediterranean Sea, which shows one of the highest warming trends in the world. In this area, the most important environmental driver is represented by the increase in seawater temperature. Though several studies have addressed the effects of sea warming on thermophilic species, little attention has been paid to cold-water species. Among these, blue whiting (Micromesistius poutassou) constitutes one of the most important traditional fisheries resources in the northern part of the basin, particularly in the central Adriatic Sea. This area has experienced intense fishing exploitation by the Italian and Croatian fishing fleets. Since 2015, the Pomo/Jabuka Pits area, the fleets’ main fishing ground, has been subject to a series of fishing regulations over time and space. In the present study, we investigated the age structure and growth performance (by means of otoliths) of blue whiting, comparing samples collected during 1985–86 and 2020–21 in the Pomo/Jabuka Pits. Our results show that the 2020–21 blue whiting specimens had a lower length-at-age compared to 1985–86. The asymptotic length estimate decreased from 29 cm TL in 1985–86 to 25 cm TL in 2020–21. The pattern observed might be related to a modification in the cold and dense water formation dynamics in the northern Adriatic Sea, as a consequence of climate change, resulting in higher temperatures and lower nutrient and oxygen exchange, which may have hampered the optimal growth of the species. Moreover, data on the historical trend of landings from the Adriatic Sea reveals a clear decline in catches starting from 2000 onwards. Although the introduction of a fishing ban in the Pomo/Jabuka Pits was an important milestone, the abundance of this species in the area remains at low levels, highlighting a potentially alarming situation for the stock of blue whiting in the central Adriatic Sea.

Insights into the response of coral biomineralisation to environmental change from aragonite precipitations in vitro

Precipitation of marine biogenic CaCO3 minerals occurs at specialist sites, typically with elevated pH and dissolved inorganic carbon, and in the presence of biomolecules which control the nucleation, growth, and morphology of the calcium carbonate structure. Here we explore aragonite precipitation in vitro under conditions inferred to occur in tropical coral calcification media under present and future atmospheric CO2 scenarios. We vary pH, ΩAr and pCO2 between experiments to explore how both HCO3− and CO32− influence precipitation rate and we identify the effects of the three most common amino acids in coral skeletons (aspartic acid, glutamic acid and glycine) on precipitation rate and aragonite morphology. We find that fluid ΩAr or [CO32−] is the main control on precipitation rate at 25 °C, with no significant contribution from HCO3− or pH. All amino acids inhibit aragonite precipitation at 0.2–5 mM and the degree of inhibition is inversely correlated with ΩAr and, in the case of aspartic acid, also inversely correlated with seawater temperature. Aspartic acid inhibits precipitation the most, of the tested amino acids (and generates changes in aragonite morphology) and glycine inhibits precipitation the least. Previous work shows that ocean acidification increases the amino acid content of coral skeletons and probably reduces calcification media ΩAr, both of which can inhibit aragonite precipitation. This study and previous work shows aragonite precipitation rate is exponentially related to temperature from 10 to 30 °C and small anthropogenic increases in seawater temperature will likely offset the inhibition in precipitation rate predicted to occur due to increased skeletal aspartic acid and reduced calcification media ΩAr under ocean acidification.

Structurally stable but functionally disrupted marine microbial communities under a future climate change scenario: Potential importance for nitrous oxide emissions

The blue mussel Mytilus edulis is a widespread and abundant bivalve species along the North Sea with high economic and ecological importance as an engineer species. The shell of mussels is intensively colonized by microbial organisms that can produce significant quantities of nitrous oxide (N2O), a potent greenhouse gas. To characterize the impacts of climate change on the composition, structure and functioning of microbial biofilms on the shell surface of M. edulis, we experimentally exposed them to orthogonal combinations of increased seawater temperature (20 vs. 23 °C) and decreased pH (8.0 vs. 7.7) for six weeks. We used amplicon sequencing of the 16S rRNA gene to characterize the alpha and beta diversity of microbial communities on the mussel shell. The functioning of microbial biofilms was assessed by measuring aerobic respiration and nitrogen emission rates. We did not report any significant impacts of climate change treatments on the diversity of mussel microbiomes nor on the structure of these communities. Lowered pH and increased temperature had antagonistic effects on the functioning of microbial communities with decreased aerobic respiration and N2O emission rates of microbial biofilms in acidified seawater compared to increased rates in warmer conditions. An overriding impact of acidification over warming was finally observed on N2O emissions when the two factors were combined. Although acidification and warming in combination significantly reduced N2O biofilm emissions, the promotion of aquaculture activities in coastal waters where shellfish do not normally occur at high biomass and density could nonetheless result in unwanted emissions of this greenhouse gas in a near future.

Ocean warming and acidification detrimentally affect coral tissue regeneration at a Mediterranean CO2 vent

Among the main phenomena that are causing significant changes in ocean waters are warming and acidification, largely due to anthropogenic activities. Growing evidence suggests that climate change is having more substantial and rapid effects on marine communities than on terrestrial ones, triggering several physiological responses in these organisms, including in corals. Here we investigated, for first time in the field, the combined effect of increasing seawater acidification and warming on tissue regeneration rate of three Mediterranean scleractinian coral species characterized by different trophic strategies and growth modes. Balanophyllia europaea (solitary, zooxanthellate), Leptopsammia pruvoti (solitary, non-zooxanthellate) and Astroides calycularis (colonial, non-zooxanthellate) specimens were transplanted, during a cold, intermediate, and warm period, along a natural pH gradient generated by an underwater volcanic crater at Panarea Island (Mediterranean Sea, Italy), characterized by continuous and localized CO2 emissions at ambient temperature. Our results show a decrease in regenerative capacity, especially in the zooxanthellate species, with increasing seawater temperature and acidification, with demonstrated species-specific differences. This finding suggests that increasing seawater temperature and acidification could have a compounding effect on coral regeneration following injury, potentially hindering the capacity of corals to recover following physical disturbance under predicted climate change.

Predicting the contribution of climate change on North Atlantic underwater sound propagation.

Since the industrial revolution, oceans have become substantially noisier. The noise increase is mainly caused by increased shipping, resource exploration, and infrastructure development affecting marine life at multiple levels, including behavior and physiology. Together with increasing anthropogenic noise, climate change is altering the thermal structure of the oceans, which in turn might affect noise propagation. During this century, we are witnessing an increase in seawater temperature and a decrease in ocean pH. Ocean acidification will decrease sound absorption at low frequencies (<10 kHz), enhancing long-range sound propagation. At the same time, temperature changes can modify the sound speed profile, leading to the creation or disappearance of sound ducts in which sound can propagate over large distances. The worldwide effect of climate change was explored for the winter and summer seasons using the (2018 to 2022) and (2094 to 2098, projected) atmospheric and seawater temperature, salinity, pH and wind speed as input. Using numerical modelling, we here explore the impact of climate change on underwater sound propagation. The future climate variables were taken from a Community Earth System Model v2 (CESM2) simulations forced under the concentration-driven SSP2-4.5 and SSP5-8.5 scenarios. The sound modeling results show, for future climate change scenarios, a global increase of sound speed at different depths (5, 125, 300, and 640 m) except for the North Atlantic Ocean and the Norwegian Sea, where in the upper 125 m sound speed will decrease by as much as 40 m s-1. This decrease in sound speed results in a new sub-surface duct in the upper 200 m of the water column allowing ship noise to propagate over large distances (>500 km). In the case of the Northeast Atlantic Ocean, this sub-surface duct will only be present during winter, leading to similar total mean square pressure level (SPLtot) values in the summer for both (2018 to 2022) and (2094 to 2098). We observed a strong and similar correlation for the two climate change scenarios, with an increase of the top 200 m SPLtot and a slowdown of Atlantic Meridional Overturning Circulation (AMOC) leading to an increase of SPLtot at the end of the century by 7 dB.

The impact of salps (Salpa thompsoni) on the Antarctic krill population (Euphausia superba): an individual-based modelling study

BackgroundKrill (Euphausia superba) and salps (Salpa thompsoni) are key macrozooplankton grazers in the Southern Ocean ecosystem. However, due to differing habitat requirements, both species previously exhibited little spatial overlap. With ongoing climate change-induced seawater temperature increase and regional sea ice loss, salps can now extend their spatial distribution into historically krill-dominated areas and increase rapidly due to asexual reproduction when environmental conditions are favorable. Understanding the potential effects on krill is crucial, since krill is a species of exceptional trophic significance in the Southern Ocean food web. Negative impacts on krill could trigger cascading effects on its predators and prey. To address this question, we combined two individual-based models on salps and krill, which describe the whole life cycle of salp individuals and the dynamic energy budget of individual krill. The resulting new model PEKRIS (PErformance of KRIll vs. Salps) simulates a krill population for 100 years under varying chlorophyll-a concentrations in the presence or absence of salps.ResultsAll of the investigated krill population properties (abundance, mean length, and yearly egg production) were significantly impacted by the presence of salps. On the other hand, salp density was not impacted if krill were present. The medians of krill population properties deviated during variable maximum chlorophyll-a density per year when salps were introduced by − 99.9% (− 234 individuals per 1000 m3) for krill density, − 100% (− 22,062 eggs per 1000 m3) for krill eggs and − 0.9% (− 0.3 mm) for mean length of krill.ConclusionsIf both species compete for the same food resource in a closed space, salps seem to inhibit krill populations. Further simulation studies should investigate whether this effect prevails if different phytoplankton sizes and consumption preferences of krill are implemented. Furthermore, direct predation of the two species or consumption of krill fecal pellets by salps could change the impact size of the food competition.

Investigating the effect of bacterial coinfections on juvenile and adult green‐lipped mussels (Perna canaliculus)

AbstractThe New Zealand's Greenshell™ mussel (Perna canaliculus) aquaculture industry is being affected by summer mortality events associated with increasing seawater temperatures and pathogens. In this study, challenge experiments were conducted to investigate, for the first time, the effects of pathogen coinfection on the survivability and haemolymph immune responses of juvenile and adult mussels. Animals were injected with marine broth (control), Vibrio mediterranei, Photobacterium swingsii, or a mixture of V. mediterranei and P. swingsii. Then, mussel survival was monitored for 72 h, and haemolymph was sampled for bacterial quantification and metabolomics analyses at 24‐ and 48‐h post challenge. Coinfected adults and juveniles showed 100% mortality. Bacterial colony counts in haemolymph decreased as infection time continued, especially in juveniles. The haemolymph metabolome of mussels exposed to single bacterial species and coinfection showed response changes largely within energy metabolism. Mussels infected with V. mediterranei exhibited increased metabolites linked to the glutathione pathway, branched‐chain amino acids, and others over time, supporting structural functions. Conversely, mussels infected with P. swingsii showed no metabolic differences over time. The coinfection group exhibited large decreases in important metabolites, such as fatty acids as an alternative energy source and amino acids to support immune functions and protein synthesis.

Contrasting effects of temperature and biological processes on aragonite saturation state at the A4HDYD station in the North Yellow Sea

To explore the effects of seawater temperature and biological processes on aragonite saturation state (Ωarag), eight field surveys were conducted from December 2014 to November 2015 at A4HDYD station in the North Yellow Sea (NYS). Low regional yearly initial values of seawater Ωarag (1.26–1.76) were obtained in winter due to low seawater temperature. During spring to early autumn, surface-water Ωarag increased from 2.02 to 3.47 for the increasing seawater temperature and biological production, whereas bottom-water Ωarag remained as low as 1.44–1.79 due to low seawater temperature, net community respiration and the influence of the North Yellow Sea Cold Water Mass (NYSCWM). Following the collapse of stratification in late autumn, the seawater was well-mixed with an average Ωarag of 2.17. The annual cycle of seawater temperature dominated the seasonal variations of Ωarag, counteracted by biological production increasing Ωarag of 0.49 in surface water in March and strengthened by net community respiration decreasing Ωarag of 0.11–0.41 below the pycnocline during summer and autumn. It is, therefore, mid-to-high latitude coastal areas impacted by human activities are likely subject to ocean acidification due to the combined effects of low seawater temperature and net community respiration.