Rise In Seawater Temperature Research Articles

The Interactive Effects of the Anti-Sea Lice Pesticide Azamethiphos and Temperature on Oxidative Damage and Antioxidant Responses in the Oyster Ostrea chilensis.

Azamethiphos is used in the salmon industry to treat sea lice and is subsequently discharged into the sea, which may affect non-target species (NTS). A rise in seawater temperature could enhance the sensitivity of NTS. Thus, in the present investigation, the combined effects of azamethiphos (0 µg L-1, 15 µg L-1 and 100 µg L-1) and temperature (12 °C and 15 °C) was assessed over time (7 days) in the gonads and gills of the oyster Ostrea chilensis, assessing its oxidative damage (lipid peroxidation and protein carbonyls) and total antioxidant capacity. Our results indicated that in gonads and gills, lipid peroxidation levels increased over time during exposure to both pesticide concentrations. Protein carbonyl levels in gills increased significantly in all experimental treatments; however, in gonads, only pesticide concentration and exposure time effected a significant increase in protein damage. In both, gill and gonad temperature did not influence oxidative damage levels. Total antioxidant capacity in gonads was influenced only by temperature treatment, whereas in the gills, neither temperature nor azamethiphos concentration influenced defensive responses. In conclusion, our results indicated the time of pesticide exposure (both concentrations) had a greater influence than temperature on the cellular damage in this oyster.

The mussel larvae microbiome changes in response to a temperature rise

Ocean warming caused by global climate change influences the function, diversity, and community dynamics of commensal microorganisms, including the hemolymph and the gut microbiota in mussels. However, the microbiota in hard-shelled mussel (Mytilus coruscus) larvae and the effect of temperature on the microbial community structure have yet to be studied. Herein, we investigated the core microbiota of M. coruscus larvae and the impact of acute (4 h) and gradual (4 days) exposure to a rise in seawater temperature from 21 to 25 °C. Eleven core genera were identified in M. coruscus larvae by 16S rDNA gene sequencing: Alteromonas, Brevundimonas, Delftia, Microbacterium, Neptuniibacter, Neptunomonas, Pseudoalteromonas, Rhodococcus, Stenotrophomonas, Tenacibaculum, and Thalassotalea. The microbiota of larvae in the short exposure treatment was similar to the control. However, the abundance of Delftia, Neptunomonas, Pseudoalteromonadaceae, Rhodococcus, and Stenotrophomonas decreased significantly in the long-exposure larvae. In contrast, at the genus level, the abundance of Tenacibaculum increased significantly. Diversity and multivariate analyses confirmed that the microbiota patterns were linked to seawater warming over the long term. Microbiota diversity did not change significantly, regardless of whether the seawater temperature increased quickly or slowly; however, we observed a significant increase in the microbiota species abundance at higher temperatures. Among the altered bacterial genera, Delftia, Neptunomonas, and Rhodococcus function in the degradation of organic compounds; Pseudoalteromonas is closely associated with mussel attachment and metamorphosis, and Tenacibaculum is an opportunistic pathogen that can cause marine mollusk death. The results suggest that marine heat waves caused by climate change may reduce the ability of symbiotic bacteria to degrade environmental toxins, will affect mussel larvae metamorphosis, and increase the abundance of opportunistic pathogens, thereby increasing the risk of disease and death of mussel larvae.

Reef building corals show resilience to the hottest marine heatwave on record in the Gulf of Aqaba

Coral reefs are facing rapid deterioration, primarily due to a global rise in seawater temperature. In conjunction, the frequency and intensity of extreme high temperature events, known as marine heatwaves (MHWs), are increasing. The Gulf of Aqaba (GoA) in the northern Red Sea is home to corals known for their thermal resilience, yet concerns have been raised regarding the potential for MHWs to put this coral refuge at risk. In summer of 2021, the hottest MHW so far occurred in the GoA, with sea surface temperatures peaking at 31°C and persisting above the local summer maximum for 34 days. To assess the physiological response of the corals Stylophora pistillata and Pocillopora damicornis to this event, we analyzed the monthly content across a year of host and symbiont proteins, carbohydrates, and lipids, pre-, during, and post the MHW, as a proxy for metabolic stress. We found that the MHW was not fatal to either species and did not induce bleaching, based on algal densities and chlorophyll content. Species-specific responses were detected. In S. pistillata, host protein content decreased (33%) at the onset of the MHW (August) compared to pre-MHW levels (July). Algal symbionts of S. pistillata were unaffected by the MHW in their maximal photosynthetic efficiency (Fv/Fm) and exhibited higher carbohydrate levels (+34%) at the end of the MHW (September) compared to its onset. In contrast, no significant catabolic response was detected in P. damicornis host or symbionts, and the maximal relative electron transport rate (rETRmax) of symbionts was 37% higher during the MHW than the annual average. These results highlight the remarkable ability of common GoA corals to withstand extreme thermal anomalies, underscoring the global significance of this coral refuge.

Meta-analysis of the thermal pollution caused by coastal nuclear power plants and its effects on marine biodiversity

The rise in seawater temperature due to industrial activities is one of the main threats to marine biodiversity. In nuclear power plants, large volumes of water are used for their operation, returning to the ecosystem at higher temperatures. A global meta-analysis was performed to evaluate the thermal effects caused by coastal nuclear power plants on marine organisms. We found 853 articles of which, 99 were included in the qualitative analysis and 75 in the meta-analysis. The meta-analysis showed an increase of 4.38 °C in water temperature near the outfall, and the temperature variation of each study was found to be associated with the power plant latitudes. The main effects on organisms were related to changes in the structure and composition of aquatic communities, with species abundance, distribution, dominance, and density being the most cited ones. Among the affected groups, photosynthesizing microorganisms were the most cited, potentially contributing to shifts in ecosystem dynamics.

Quantifying the contribution of temperature, salinity, and climate change to sea level rise in the Pacific Ocean: 2005-2019

In recent decades, Pacific Ocean’s steric sea level anomaly (SSLA) has shown prominent patterns among global sea level variations. With ongoing global warming, the frequency and intensity of climate and sea level changes have increased, particularly in the tropical Pacific region. Therefore, it is crucial to comprehend the overall trends and mechanisms governing volumetric sea level changes in the Pacific. To accurately quantify the spatiotemporal evolution characteristics of density-driven sea level change in the Pacific Ocean (PO) from 2005 to 2019, we decomposed temperature and salinity into linear trends, interannual variations, seasonal variations, and residual terms using the STL (seasonal-trend decomposition based on loess) method. To evaluate the influence of ocean temperature, salinity, and climate change on density-driven sea level change and its underlying mechanisms, we decompose temperature as well as salinity changes through into the Heaving (vertical displacements of isopycnal surfaces) and Spicing (density-compensated temperature and salinity change) modes. The findings reveal an average steric sea level rise rate of 0.34 ± 0.16 mm/yr in the PO from 2005 to 2019. Thermosteric sea-level accounts for 82% of this rise, primarily due to seawater temperature rise at depths of 0-700 m caused by Heaving mode changes. Accelerated SSLA increase via the thermosteric effect has been connected to interactions between greater Ekman downwelling from surface winds, radiation forcing linked to global greenhouse gases, and changes in the Pacific warm currents triggered by El Niño-Southern Oscillation (ENSO) episodes. Although salinity is affected by the Subantarctic Mode Water (SAMW) and the Antarctic Intermediate Water (AAIW) in the southern Indian Ocean, however the significance of salinity in sea level change is little compared to the role played by thermocline shift. This study offers a substantial contribution to the field, providing robust data and technical support, and facilitating a deeper understanding of the mechanisms underlying the effects of temperature and salinity on sea level changes during periods of rapid climate change, thus enhancing the accuracy of future predictions regarding sea level rise.

How thermal priming of coral gametes shapes fertilization success

Seawater temperature rise is damaging coral reef ecosystems. There is growing evidence for the negative impact of rising temperatures on the survival of adult corals and their reproductive success. However, the effect of elevated temperatures on gametes remains scarcely studied. Here we tested the effect of the thermal priming of gametes on the fertilization success in experimentally tested populations of Acropora cytherea corals in French Polynesia. As expected, a temperature of 30 °C (ambient +3 °C) reduces coral fertilization success. However, the thermal exposure of gametes to 30 °C after their release in seawater prior to fertilization limited fertilization failure, with a greater impact of oocytes in comparison to sperm. This temperature is similar to temperatures observed in nature under the changing climate. Our findings imply that the thermal priming of early life stages, such as gametes may play a role in maintaining the coral fertilization success in spite of increasing seawater temperature.

A Case Study on the Preliminary Study for Disaster Prevention of Storm Surge: Arrangement of Structures

Climate change is accelerating worldwide due to the recent rise in global temperature, and the intensity of typhoons is increasing due to the rise in seawater temperature around the Korean Peninsula. An increase in typhoon intensity is expected to increase not only wind damage, but also coastal damage caused by storm surge. Accordingly, in this study, a study of the method of reducing storm surges was conducted for the purpose of disaster prevention in order to respond to the increasing damage from storm surges. Storm surges caused by typhoons can be expected to be affected by structures located on the track of typhoon, and the effects of storm surges were studied by the eastern coast and the barrier island along the coast of the Gulf of Mexico in the United States. This study focused on this aspect and conducted related research, considering that storm surges in the southern coastal area of the Korean Peninsula could be directly or indirectly affected by Jeju Island, which is located on the track of typhoon. In order to analyze the impact of Jeju Island on storm surges, simulations were performed in various situations using a numerical analysis model. The results of using Jeju Island are thought to be able to be used to study new disaster prevention structures that respond to super typhoons.

Enhanced continental chemical weathering during the multiple early Eocene hyperthermals: New constraints from the southern Indian Ocean

Multiple short-term (<105 years) global warming events (“hyperthermals”) occurred throughout the early Eocene. Chemical weathering of continental silicate rocks is considered to have played a key role in recovery from these transient global warming events via consumption of excess atmospheric CO2. However, although evidence of this negative feedback has been reported for the Paleocene–Eocene Thermal Maximum (PETM), the effectiveness of chemical weathering during other transient hyperthermals remains poorly constrained. Here, we newly report early Eocene marine Os isotope records including Eocene Thermal Maximum 2 (ETM2), the I1 event, and ETM3 at Ocean Drilling Program Site 752 in the southern Indian Ocean. We demonstrate that marine 187Os/188Os increased during the hyperthermal events that were less severe than the PETM. The intensity of continental silicate weathering increased by 18%–22%, 17%–21%, and 13%–16% during ETM2, the I1 event, and ETM3, respectively, compared to the background conditions. Based on a reconsidered formulation of an Os mass-balance model, the intensity of continental silicate weathering during the PETM was reassessed to be a 34%–42% increase relative to the pre-PETM level. Thus, the continental chemical weathering flux during the Eocene hyperthermals may have been up to half as large as that of the PETM. It is noteworthy that the ordering of the changes in continental silicate weathering did not agree with the ordering of the seawater temperature rise among these events. This weathering–warming inconsistency might be attributable to (1) potential underestimation of continental silicate weathering due to the emplacement of Large Igneous Provinces (LIPs) and related basalt weathering, such as the North Atlantic Igneous Province and Siletzia in western North America, (2) changes in the background level of weathering intensity, and/or (3) a secular decrease in continental weatherability through the long-lasting early Eocene warming trend.

Historical and future naturalization of Magallana gigas in the Galician coast in a context of climate change

Magallana gigas is a naturalized species on the north coast of Galicia (Rías Altas, Northwest Iberian Peninsula), where it was unintentionally introduced. In recent decades, a greater abundance of M. gigas has been observed on the Galician coast, expanding towards the south, reaching the Artabro Gulf (Rías Centrales, NW Galician coast), probably due to ocean warming. Although this species has been cultivated in the Rías Baixas since the early 1990s and spawning has been reported, recruitment was never observed, which is likely due to the cold water upwelled during the spawning months. The future rise in seawater temperature may favor the naturalization of the non-indigenous species M. gigas southwards, in the Rías Baixas. Thermally, the Ría de Arousa seems to be the most favorable estuary for the future settlement of M. gigas, which may occur in the next decades. The extent of thermally favorable zones within estuaries is projected to increase rapidly by mid-century, and reaching 100 % of the estuarine area by the end of the century. As has already happened in other areas of the world, the expansion and naturalization of the Pacific oyster on the Galician coast will likely affect the native communities and economic activities, making it necessary to implement monitoring and management strategies to mitigate its effect.

The impact of temperature on lithium toxicity in the gastropod Tritia neritea.

The most important use of lithium (Li) is in rechargeable batteries. The growing use of Li, incorrect disposal of Li-based applications, and inefficient recycling strategies for their elimination will result in the release of this metal into the aquatic systems. Alongside with the impacts caused by pollutants, organisms in coastal ecosystems are also facing environmental changes as those related with climate change scenarios, namely, seawater temperature rise. In this context, the present study aimed to evaluate the influence of temperature on Li toxicity, using the Nassariid gastropod Tritia neritea as model species. Metabolism and oxidative stress related biomarkers were evaluated after a 28-day exposure period. The results demonstrated that temperature enhanced the toxic impacts of Li, most probably due to snail increased sensitivity when under warming conditions. As a consequence of inefficient antioxidant and biotransformation capacity, lipid peroxidation was observed in Li-contaminated snails at 21 ºC, demonstrating a significant interaction between both factors. Regarding snails' metabolic capacity, Li did not affect snails, but a clear decrease on their metabolism was observed at increased temperature (with or without Li) which may limit snail defense capacity. Overall, the present findings demonstrated the impacts derived from Li towards marine intertidal gastropods, evidencing enhanced threats under predicted warming conditions. Considering the role of T. neritea in the ecosystem functioning, impacts on this species may greatly affect other populations and eventually the entire community.

Transcriptome and enzyme activity analyses of tolerance mechanisms in pearl oyster (Pinctada fucata) under high-temperature stress

Pearl oyster (Pinctada fucata) is an economically valuable shellfish for seawater pearl production. However, many pearl oysters are dying as the global climate warms and seawater temperatures rise. The breeding of high temperature-resistant strains is therefore urgent. We performed transcriptome analysis to reveal the response mechanism of P. fucata to long-term high-temperature stress. Nanopore sequencing identified 1787 loci and revealed high-quality full-length isoforms for 17,803 novel splice isoforms. The large-scale study suggested differential patterns of alternative splicing (AS) regulation and transcriptional regulation under heat stress. There were more AS events in the high-temperature group (HT) than the normal temperature (NT) control group. In total, 44 upregulated and 33 downregulated differentially expressed genes (DEGs) were evident between NT and HT. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that DEGs were mainly associated with defence mechanisms, phagosome signalling, cytoskeleton, posttranslational modification, protein turnover and chaperones under heat stress. Nine DEGs (c-fox, heat shock protein 60, heat shock protein 90, fucolectin-1, dermatopontin, caveolin-1, ETS homologous factor, glutathione S-transferase sigma 3 and fatty acyl-CoA hydrolase precursor) showed complex expression pattern changes from 1 h to 30 days of high-temperature induction. Furthermore, heat stress resulted in irregular shell microstructures and impacted enzyme activity, exemplified by continuous upregulation of lactate dehydrogenase (LDH), indicating that the energy needs of P. fucata needs were met in part by anaerobic metabolism. Integrated analyses demonstrated that long-term high-temperature stress can significantly impact internal bodily functions, and disrupt physiological and biochemical processes. High-temperature stress induces pearl oysters to activate gene expression and thereby alter immune responses, respiratory metabolism, antioxidant systems, biomineralisation, and secondary metabolism. These pathways likely coordinate to support P. fucata physiology under high-temperature stress. The findings deepen our understanding of the molecular mechanisms underlying the responses to long-term high-temperature stress, and provide valuable information for future breeding of thermotolerant P. fucata strains.

Elevated pCO2 Impedes Succession of Phytoplankton Community From Diatoms to Dinoflagellates Along With Increased Abundance of Viruses and Bacteria

Eutrophic coastal regions are highly productive and greatly influenced by human activities. Primary production supporting the coastal ecosystems is supposed to be affected by progressive ocean acidification driven by increasing CO2 emissions. In order to investigate the effects of high pCO2 (HC) on eutrophic plankton community structure and ecological functions, we employed 9 mesocosms and carried out an experiment under ambient (∼410 ppmv) and future high (1000 ppmv) atmospheric pCO2 conditions, using in situ plankton community in Wuyuan Bay, East China Sea. Our results showed that HC along with natural seawater temperature rise significantly boosted biomass of diatoms with decreased abundance of dinoflagellates in the late stage of the experiment, demonstrating that HC repressed the succession from diatoms to dinoflagellates, a phenomenon observed during algal blooms in the East China Sea. HC did not significantly influence the primary production or biogenic silica contents of the phytoplankton assemblages. However, the HC treatments increased the abundance of viruses and heterotrophic bacteria, reflecting a refueling of nutrients for phytoplankton growth from virus-mediated cell lysis and bacterial degradation of organic matters. Conclusively, our results suggest that increasing CO2 concentrations can modulate plankton structure including the succession of phytoplankton community and the abundance of viruses and bacteria in eutrophic coastal waters, which may lead to altered biogeochemical cycles of carbon and nutrients.

Effect of polystyrene microplastics and temperature on growth, intestinal histology and immune responses of brine shrimp Artemia franciscana

Microplastics pollution and seawater temperature rise have been the major environmental issues, threatening the survival and biodiversity of marine organisms. This study evaluated the combined effect of temperature and polystyrene microplastics (MP) on Artemia, a filter-feeding crustacean that is widely used for environmental toxicology studies. Brine shrimp Artemia franciscana were exposed to three MP concentrations (0, 0.2, and 2.0 mg/L) and three temperatures (22, 26, and 30 °C) for 14 d. In general, higher MP concentration and temperature led to a decreased survival rate and growth. Two-way ANOVA analysis indicated that the survival rate of Artemia was significantly impacted by both MP concentration and temperature (P 0.05). Growth of Artemia was significantly impacted by temperature (P<0.05), and with a significant interaction between two factors (P<0.05). Furthermore, the enzymatic activity, intestinal histological analyses, and immune gene expression were determined for Artemia reared at 30 °C with three MP concentrations (0, 0.2, and 2.0 mg/L). The results showed that 2.0 mg/L MP resulted in reduced Artemia intestinal microvilli and exfoliated epithelia cells, significantly increased acid phosphatase (ACP) activity (P<0.05) and immune-related gene ADRA1B and CREB3 expression, revealing that higher MP concentration could induce oxidative and immunological stress on Artemia at 30 °C. Overall, our study suggests that MP and temperature have combined adverse effect on Artemia, especially at relatively high temperature and polystyrene MP concentration. These findings are important to understand the potential ecological risks posed by these two factors on the organisms in marine environment.

Impact Assessment of Thermal Discharge from the Kemen Power Plant Based on Field Observation and Numerical Simulation

Zeng, Z.; Luo, Y.; Chen, Z.J.; Tang, J.J.; Wang, Y.H., and Chen, C.H., 2020. Impact assessment of thermal discharge from the Kemen power plant based on field observation and numerical simulation. In: Guido Aldana, P.A. and Kantamaneni, K. (eds.), Advances in Water Resources, Coastal Management, and Marine Science Technology. Journal of Coastal Research, Special Issue No. 104, pp. 351–361. Coconut Creek (Florida), ISSN 0749-0208.The impact of the Kemen Power Plant thermal discharge on temperature rise in the ambient waters in the Luoyuan Bay was studied using field observation and numerical simulation. The scope of influence, indicated by the maximum temperature rise envelope curves during the observation period, was determined through field measurements of water temperature in the study area. The measurements revealed that the surface water with temperature rise diffused along the shoreline to the upstream and downstream of the power plant after the thermal discharge entered the sea. The longitudinal diffusion distance along the direction parallel to the shoreline was significantly longer than the transverse diffusion distance along the direction perpendicular to the shoreline. The area with the maximum temperature rise was near the outfall. Under the field conditions given in this paper, the surface seawater temperature rise varied from a maximum of 10 °C near the outfall to 0.5 °C at a distance of 600 m from the shore. Temperature rise was mainly observed in the surface water, and the scope of influence rapidly diminished vertically with minimal temperature rise in the waters 3 m below the surface. Meanwhile, a 2-D tide field mathematical model and a thermal discharge diffusion model were developed to simulate the diffusion process of the power plant thermal discharge in the sea area. A comparison of the simulated results obtained under the same conditions as the field measurements showed that the established numerical model can effectively reflect the temperature diffusion of the thermal discharge, as well as the scope of full-tide maximum temperature rise at typical tide phases. Therefore, the numerical model of thermal discharge described in this paper can serve as a powerful tool to predict the impact of thermal discharge from power plants.

Metabolic response of the cannonball jellyfish Stomolophus meleagris upon short-term exposure to thermal stress

Jellyfish are non-model organisms that have brought the scientific community's attention over the last decades since the frequency and intensity of these species blooms around the world have increased significantly. The occurrence of blooms has been hypothesized due to the rise in seawater temperature associated with climate change. This fact has promoted an increased interest in studying jellyfish metabolic responses to face thermal stress and maintain cell homeostasis. In this study, the response of the cannonball jellyfish Stomolophus meleagris to short-term exposure to different temperatures was evaluated. The survival and respiratory rates, and the concentration of glucose, L-lactate, glycogen, ATP, and total soluble protein in the umbrella of adult jellyfish were measured. Low survival rates at extreme temperatures (18 and 33 °C) and an increase in the jellyfish respiratory rates were observed as seawater temperature raised. Rapid changes were detected in energy substrates such as glucose and glycogen that significantly varied at extreme temperatures and longer exposure periods. L-lactate levels increased after 2 h of exposure, and then remained steady at longer times of exposure. Soluble protein concentration decreased significantly in jellyfish exposed to extreme temperatures, and ATP increased after exposure to non-optimal temperatures (18, 28, and 33 °C). These results suggest that S. meleagris faces temperature changes through rapid metabolic responses that use energetic reserves, activate anaerobic metabolism, and display a remarkable ability to synthesize ATP and maintain energy, even at long exposure.

The evolution of the Kuroshio Current over the last 5 million years since the Pliocene: Evidence from planktonic foraminiferal faunas

Meridional heat transport of the western Pacific boundary current (the Kuroshio Current) is one of the key factors in global climate change. This current is important because it controls the temperature gradient between low latitudes and the North Pacific and so significantly influences mid-latitude atmosphere-ocean interactions. Here we reconstruct changes in hydrological conditions within the mid-latitude mainstream of the Kuroshio Current based on faunal analysis of planktonic foraminifera in core DSDP 296 from the Northwest Pacific Ocean. This approach enabled us to deduce evolutionary processes within the Kuroshio Current since the Pliocene. A total of 57 species in the coarser section (> 150 µm) were identified; results indicate that planktonic foraminiferal faunal evolution has mainly been characterized by three major stages, the first of which comprised mixed-layer warm-water species of Globigerinoides ruber which first appeared between 3.5 and 2.7 Ma and then gradually increased in content. Percentages of another warm-water species of G. conglobatus also gradually increased in number over this interval. Variations in warm-water species indicate a gradual rise in sea surface temperature (SST) and imply initiation of Kuroshio Current impact on the Northwest Pacific Ocean since at least 3.5 Ma. Secondly, over the period between 2.7 and 2.0 Ma, thermocline species of Globigerina calida , Neogloboquadrina humersa , Neogloboquadrina dutertrei , and Pulleniatina obliquiloculata started to appear in the section. This fauna was dominated by G. ruber as well as increasing G. conglobatus contents. These features imply a further rise in SST and its gradually enhanced influence on thermocline water, suggesting strengthening of the Kuroshio Current since 2.7 Ma. Thirdly, between 2.0 Ma and present, increasing contents of thermocline species (i.e., G. calida , N. dutertrei and P. obliquiloculata ) indicate a gradual rise in seawater temperature at this depth and also imply more intensive Kuroshio Current during this period. On the basis of comparative records from cores ODP 806 and DSDP 292 from the low latitude Western Pacific, we propose that initiation of the impact of the Kuroshio Current in the Northwest Pacific and it subsequent stepwise intensifications since 3.5 Ma can be closely related to the closure and restriction of the Indonesian and Central American seaways as well as variations in the Western Pacific Warm Pool (WPWP) and equatorial Pacific region.

Reproductive timing and synchronized reproduction of the sea urchin Pseudechinus magellanicus (Echinoidea: Temnopleuridae) in central Patagonia, Argentina

ABSTRACT The reproduction of the sea urchin Pseudechinus magellanicus and the influence of environmental factors were studied during a 27-month period in central Patagonia, Argentina, where this species is among the dominant grazers in kelp forests and tide pools. The monthly variation in the gonad dry weights, gonadal stages and other quantitative reproductive variables (oocyte diameter, density and thickness of spermatogenic columns) indicated a clearly annual gametogenic cycle and revealed a high level of spawning synchrony. A main spawning event occurs between August and September, and a minor and asynchronous spawning event was recorded during the austral summer (January–March). The highest gonadal growth rate occurs between late spring and summer, accompanied by growth and early prematurity gonadal stages, indicating active vitellogenesis. The accumulation of ova begins in autumn and shows a peak during winter. After spawning, the recovery stages are not extended in time and ovaries do not show a complete meshwork of nutritive phagocytes within the acinus, suggesting simultaneous reabsorption and inversion processes. Spermatogenesis shows a higher maturation rate than oogenesis, and a higher temporal prevalence of premature and mature stages. Major spawning coincides with the first rise in seawater temperature, the maximum rate of increase in day length and the maximum peak of chlorophyll a. Results also revealed some temporal differences in the gonadal cycle, vitellogenesis and spawning periods compared with other P. magellanicus populations from different latitudes. This could be attributed to individual differences in the acquisition and allocation of energy for gametogenesis, as well as to local environmental factors.

Genomic characterization of filamentous phage vB_VpaI_VP-3218, an inducible prophage of Vibrio parahaemolyticus.

The seawater temperature rise can promote the growth of potentially pathogenic Vibrio species. In the North Sea, V. parahaemolyticus strains have been isolated and characterized. These strains contain prophages that may contribute to the emergence of pathogenic strains in the marine environment. Here, we present the genome structure and possible biological functions of the inducible phage vB_VpaI_VP-3218, a novel filamentous phage carried by the V. parahaemolyticus strain VN-3218. Prophages of the strain VN-3218 were induced with mitomycin C and the DNA from the phage induction was sequenced. Two incomplete prophages were identified, only one complete phage genome with length of 11,082bp was characterized. The phage vB_VpaI_VP-3218 belongs to the Inoviridae family and shows close homology to the Saetivirus genus. This phage can integrate into the chromosomal host genome and carries host-related regions absent in similar phage genomes, suggesting that this phage might integrate in other Vibrio host genomes from the environment. Furthermore, this phage might have a role in pathogenicity due to potential zonula occludens toxin genes. Based on its genomic similarity, the genome of vB_VpaI_VP-3218 phage probably integrates into the lysogen's chromosome and replicates as episome. This study complements prophage induction and bioinformatic studies applied to non-model species of potentially pathogenic Vibrio species. The characterization of this phage provides new insights with respect to the presence of filamentous phages in environmental V. parahaemolyticus strains, which might have a role in the emergence of new pathogenic strains in the North Sea.

Molecular mechanisms of acclimation to long-term elevated temperature exposure in marine symbioses.

Seawater temperature rise in French Polynesia has repeatedly resulted in the bleaching of corals and giant clams. Because giant clams possess distinctive ectosymbiotic features, they represent a unique and powerful model for comparing molecular pathways involved in (a) maintenance of symbiosis and (b) acquisition of thermotolerance among coral reef organisms. Herein, we explored the physiological and transcriptomic responses of the clam hosts and their photosynthetically active symbionts over a 65day experiment in which clams were exposed to either normal or environmentally relevant elevated seawater temperatures. Additionally, we used metabarcoding data coupled with in situ sampling/survey data to explore the relative importance of holobiont adaptation (i.e., a symbiont community shift) versus acclimation (i.e., physiological changes at the molecular level) in the clams' responses to environmental change. We finally compared transcriptomic data to publicly available genomic datasets for Symbiodiniaceae dinoflagellates (both cultured and in hospite with the coral Pocillopora damicornis) to better tease apart the responses of both hosts and specific symbiont genotypes in this mutualistic association. Gene module preservation analysis revealed that the function of the symbionts' photosystem II was impaired at high temperature, and this response was also found across all holobionts and Symbiodiniaceae lineages examined. Similarly, epigenetic modulation appeared to be a key response mechanism for symbionts in hospite with giant clams exposed to high temperatures, and such modulation was able to distinguish thermotolerant from thermosensitive Cladocopium goreaui ecotypes; epigenetic processes may, then, represent a promising research avenue for those interested in coral reef conservation in this era of changing global climate.

Crawling and righting behavior of the subtropical sea star Echinaster (Othilia) graminicola: effects of elevated temperature

Sea stars exhibit discrete neuromuscular-mediated behaviors, such as crawling and righting, which are critical to daily functioning and survival. As global seawater temperatures rise, subtidal asteroids such as Echinaster (Othilia) graminicola on the Gulf Coast of Florida are increasingly subjected to elevated temperatures, which may compromise their neuromuscular health. To better understand the neuromuscular biology of E. graminicola and the effects of elevated seawater temperature on behavior, we first describe their righting mechanism and identify the arms used in righting and crawling. Together, this allowed us to determine if they exhibit any bilateral tendencies, related to their anterior–posterior ancestry, by measuring the frequency with which each arm led in righting and crawling. To determine the effect of elevated seawater temperature on their described righting behavior, we tested the effects of acute (1 day) and chronic (7 day) exposure to seawater temperatures ranging from 28 to 36 °C on righting time in a laboratory experiment. We found that E. graminicola rights by somersaulting, but exhibits no lead arm preference during this behavior. In crawling, Arm E, located adjacent to the madreporite, led most frequently, indicating a partial tendency toward bilateralism. Sea stars righted significantly faster with increasing temperature and exposure time as temperatures increased from 28 to 34 °C, suggesting some capacity for acclimatization to elevated temperatures. However, at 36 °C, righting time increased dramatically and sea stars experienced high mortality, suggesting E. graminicola may be living near the upper limits of its thermotolerance. As seawater temperatures rise beyond an organism’s thermal tolerance, their neuromuscular responses may become critically impaired, reducing their capacity to survive in a warming ocean.