Intertidal Organisms Research Articles

Copper toxicity does not affect low tide emersion tolerance of Mytilus galloprovincialis

Intertidal mussels are well adapted to withstand emersion from water during low tide, but they may be intermittently exposed to waterborne toxicants such as copper, which targets physiological processes including metabolism, ammonia excretion, and osmoregulation. To determine if copper exposure damages intertidal organisms' ability to tolerate tidal emersion, Mediterranean mussels (Mytilus galloprovincialis) were exposed to copper for 96 h followed by 6 h of emersion. Oxygen uptake increased after copper exposure which suggests that copper accumulation caused moderate stress in the mussels, but ammonia excretion and anaerobic metabolism were unaffected by mixed copper and emersion exposures. Shell composition analyses indicate that cycles of copper exposure and tidal emersion may affect bivalve shell growth, but copper deposition into shells may decrease the metal's overall toxicity. Results suggest that copper does not damage M. galloprovincialis's tolerance to tidal emersion, and insight is provided into the mussel's ability to overcome mixed stressor exposures.

Are pelagic mussel stages chemically attracted to barnacle stands for settlement?

These photographs show dense aggregations of juvenile mussels (Mytilus spp) growing on intertidal barnacle stands (Semibalanus balanoides) on the Atlantic coast of Nova Scotia, Canada. In wave-exposed habitats on this coast, extreme environmental events can lead to widespread mortality of intertidal organisms, resulting in large clearings on the rocky substrate. Typically, barnacles are the first macroscopic organisms that recolonize such areas. Once those barnacles attain a certain size, pelagic mussel stages settle upon them and become benthic recruits. These new additions to mussel populations occur substantially more often on barnacle patches than on bare rock. In the complex microtopography of barnacle beds, mussel recruits benefit from increased moisture during low tides and greater protection from waves during high tides. As mussel recruitment progresses, with later recruits concentrating around the first recruits, mussels achieve high densities and outcompete barnacles as they grow, ultimately becoming the dominant species.

The BioGeo Ecotile: Improving biodiversity on coastal defences using a multiscale, multispecies eco-engineering design

Hard coastal defences support lower biodiversity than natural rocky shores. Ecological enhancement on coastal structures can improve biodiversity by increasing habitat heterogeneity. Most studies have investigated the effect of only one type of texture on intertidal biodiversity. There is a lack of eco-engineering designs that mimic the complexity of natural rocky shores and are scalable for real world applications and commercial manufacturing. To address these gaps, we developed a novel, multiscale (mm-cm), multispecies design called BioGeo Ecotile that is scalable and readily manufacturable. The hybrid design combines previously tested eco-engineering features (pits, holes, grooves and crevices), providing habitats for a range of intertidal organisms. To test the success of the design, Ecotiles and smooth tiles were deployed on rock armour and flood walls along Edinburgh's coast, Scotland. Post-deployment, data on species presence and abundance were collected at the start and end of the second settlement season. Textured Ecotiles supported higher species richness (F3,55 = 21.18, p < 0.001) and colonisation than smooth tiles and adjacent rock armour. Ecotiles supported more mobile species, some of which (crabs) were not recorded on the other treatments. Material type (concrete vs rock) significantly affected community composition, where concrete was dominated by fucoids and rock by barnacles. In this temperate setting, the Ecotiles have enhanced biodiversity of rock armour achieving practical conservation goals. This is the first known retrofit of tiles onto rock armour in the UK. The tiles can be scaled up to whole walls or rock armour units. We demonstrate that a science-design approach can achieve ecological and engineering goals simultaneously, which can accelerate widespread implementation of eco-engineering in large-scale projects.

Proteostasis in ice: the role of heat shock proteins and ubiquitin in the freeze tolerance of the intertidal mussel, Mytilus trossulus.

The bay mussel, Mytilus trossulus, is an animal that can survive extracellular ice formation. Depending on air and ocean temperatures, freeze tolerant intertidal organisms, like M. trossulus, may freeze and thaw many times during the winter. Freezing can cause protein denaturation, leading to an induction of the heat shock response with expression of chaperone proteins like the 70kDa heat shock protein (HSP70), and an increase in ubiquitin-conjugated proteins. There has been little work on the mechanisms of freeze tolerance in intertidal species, limiting our understanding of this survival strategy. Additionally, this limited research has focused solely on the effects of single freezing events, but the act of repeatedly crossing the freezing threshold may present novel physiological or biochemical stressors that have yet to be discovered. Mytilus are important ecosystem engineers and provide habitat for other intertidal species, thus understanding their physiology under thermal extremes is important for preserving shoreline health. We predicted that repeated freeze exposures would increase mortality, upregulate HSP70 expression, and increase ubiquitin conjugates in mussels, relative to single, prolonged freeze exposures. Mytilus trossulus from Vancouver, Canada were repeatedly frozen for a combination of 1 × 8h, 2 × 4h, or 4 × 2h. We then compared mortality, HSP70 expression, and the quantity of ubiquitin-conjugated proteins across experimental groups. We found a single 8-h freeze caused significantly more mortality than repeated freeze-thaw cycles. We also found that HSP70 and ubiquitinated protein was upregulated exclusively after freeze-thaw cycles, suggesting that freeze-thaw cycles offer a period of damage repair between freezes. This indicates that freeze-thaw cycles, which happen naturally in the intertidal, are crucial for M. trossulus survival in sub-zero temperatures.

Hypoxia tolerance, but not low pH tolerance, is associated with a latitudinal cline across populations of Tigriopus californicus.

Intertidal organisms must tolerate daily fluctuations in environmental parameters, and repeated exposure to co-occurring conditions may result in tolerance to multiple stressors correlating. The intertidal copepod Tigriopus californicus experiences diurnal variation in dissolved oxygen levels and pH as the opposing processes of photosynthesis and cellular respiration lead to coordinated highs during the day and lows at night. While environmental parameters with overlapping spatial gradients frequently result in correlated traits, less attention has been given to exploring temporally correlated stressors. We investigated whether hypoxia tolerance correlates with low pH tolerance by separately testing the hypoxia and low pH stress tolerance separately of 6 genetically differentiated populations of T. californicus. We independently checked for similarities in tolerance for each of the two stressors by latitude, sex, size, and time since collection as predictors. We found that although hypoxia tolerance correlated with latitude, low pH tolerance did not, and no predictor was significant for both stressors. We concluded that temporally coordinated exposure to low pH and low oxygen did not result in populations developing equivalent tolerance for both. Although climate change alters several environmental variables simultaneously, organisms' abilities to tolerate these changes may not be similarly coupled.

Ecological characteristics of a typical coastal artificial shoreline considering the key drivers involved

The loss of natural shorelines has been accelerated by the construction of artificial shorelines in recent years, which is a serious threat to intertidal biodiversity and makes the ecological construction of artificial shorelines increasingly urgent, yet the mechanisms of regulating intertidal biodiversity using artificial structures are still poorly understood. In this study, the different fates and causes of the ecological effects of the two artificial seawalls were investigated in detail. We conducted on-site sampling and surveys on the water quality, wave conditions, and organisms around seawalls of different types of structures, and quantified the hydrodynamic strength distribution of the seawall walls through field experiments, while introducing numerical simulation methods to reproduce the flow field characteristics near the seawalls. The results show that the differences in the ecological effects of the investigated artificial seawalls are mainly due to flow (including wave-induced flow) rather than water quality, or other factors. Although the cavity structure of the seawall surface contributes to biodiversity, it is also the presence of this large and complex cavity structure that leads to local flow field heterogeneity in the seawall, which enhances fluid wall shear and makes it more difficult for intertidal organisms to attach and even causes a decrease in their surface biomass. However, in terms of ecosystem health, seawalls with more complex structures provide a more stable community structure, so we believe that they are more ecologically sound. In ecological shoreline construction, flow field heterogeneity should be taken into account as an important driver of biotic community assemblages on artificial coastlines. How to reconcile structural complexity with the resulting flow field heterogeneity should be an important part of ecological engineering construction. Our study provides new insights into the ecological construction of artificial shorelines.

Daily timing of low tide drives seasonality in intertidal emersion mortality risk

Sea level exerts a fundamental influence on the intertidal zone, where organisms are subject to immersion and emersion at varying timescales and frequencies. While emersed, intertidal organisms are exposed to atmospheric stressors which show marked diurnal and seasonal variability, therefore the daily and seasonal timing of low water is a key determinant of survival and growth in this zone. Using the example of shallow coral reefs, the coincidence of emersion with selected stressors was investigated for eight locations around the Australian coastline. Hourly water levels (1992 – 2016) from a high-resolution sea level hindcast (http://sealevelx.ems.uwa.edu.au), were linked to maximum surface solar radiation data from the Copernicus ERA5 atmospheric model and minimum atmospheric temperature observations from the Australian Bureau of Meteorology to identify seasonal patterns and historical occurrence of coral emersion mortality risk. Local tidal characteristics were found to dictate the time of day when low water, and therefore emersion mortality risk occurs, varying on a seasonal and regional basis. In general, risk was found to be greatest during the Austral spring when mean sea levels are lowest and a phase change in solar tidal constituents occurs. For all Great Barrier Reef sites, low tide occurs close to midday during winter and midnight in the summer, which may be fundamental factor supporting the historical bio-geographical development of the reef. Interannual variability in emersion mortality risk was mostly driven by non-tidal factors, particularly along the West Coast where El Niño events are associated with lower mean sea levels. This paper highlights the importance of considering emersion history when assessing intertidal environments, including shallow coral reef platform habitats, where critical low water events intrinsically influence coral health and cover. The study addresses a fundamental knowledge gap in both the field of water level science and intertidal biology in relation to the daily timing of low tide, which varies predictably on a seasonal and regional basis.

The influence of stochastic temperature fluctuations in shaping the physiological performance of the California mussel, Mytilus californianus.

Climate change is forecasted to increase temperature variability and stochasticity. Most of our understanding of thermal physiology of intertidal organisms has come from laboratory experiments that acclimate organisms to submerged conditions and steady-state increases in temperatures. For organisms experiencing the ebb and flow of tides with unpredictable low tide aerial temperatures, the reliability of reported tolerances and thus predicted responses to climate change requires incorporation of environmental complexity into empirical studies. Using the mussel Mytilus californianus, our study examined how stochasticity of the thermal regime influences physiological performance. Mussels were acclimated to either submerged conditions or a tidal cycle that included either predictable, unpredictable or no thermal stress during daytime low tide. Physiological performance was measured through anaerobic metabolism, energy stores and cellular stress mechanisms just before low tide, and cardiac responses during a thermal ramp. Both air exposure and stochasticity of temperature change were important in determining thermal performance. Glycogen content was highest in the mussels from the unpredictable treatment, but there was no difference in the expression of heat shock proteins between thermal treatments, suggesting that mussels prioritise energy reserves to deal with unpredictable low tide conditions. Mussels exposed to fluctuating thermal regimes had lower gill anaerobic metabolism, which could reflect increased metabolic capacity. Our results suggest that although thermal magnitude plays an important role in shaping physiological performance, other key elements of the intertidal environment complexity such as stochasticity, thermal variability and thermal history are also important considerations for determining how species will respond to climate warming.

Temperature Extremes and Sex-Related Physiology, Not Environmental Variability, Are Key in Explaining Thermal Sensitivity of Bimodal-Breathing Intertidal Crabs

Global temperature increases are predicted to have pronounced negative effects on the metabolic performance of both terrestrial and aquatic organisms. These metabolic effects may be even more pronounced in intertidal organisms that are subject to multiple, abruptly changing abiotic stressors in the land-sea transition zone. Of the available studies targeting the intertidal environment, emphasis has largely been on water-breathing model organisms and this selective focus resulted in limited reliable forecasts on the impact of global warming on primarily air-breathing intertidal species. We investigated the thermal sensitivity of six phylogenetically related fiddler crab species that occupy different microhabitats on intertidal shores from south America and east Asia to test how bimodal-breathing intertidal ectotherms cope with thermal stress. We examined the metabolic physiology and thermal limits of the crabs by measuring their cardiac function and oxygen consumption along a thermal gradient. Their specific thermal microhabitat was also appraised. We found that subtropical fiddler crab species inhabiting vegetated microhabitats have lower upper lethal temperatures and therefore greater thermal sensitivity in comparison to their tropical counterparts. Additionally, females exhibited higher oxygen consumption and lower lethal temperatures in comparison to males. Our results contradict previous predictions that species from higher latitudes that experience greater temperature variability have broader latitudinal distributions, greater phenotypic plasticity and lower thermal sensitivity. Furthermore, the higher thermal sensitivity demonstrated by female fiddler crabs with respect to males strongly suggests a role of both gametogenesis and physiological dimorphism on the thermal performance of tropical and subtropical intertidal organisms. These observations ultimately, advocates for further studies on sex-biased and development-biased thermal sensitivity before drawing any generalizations based on a single sex or life stage.

Towards an Understanding of Circatidal Clocks.

Circadian clocks are an intrinsic element of life that orchestrate appropriately timed daily physiological and behavioural rhythms entrained to the solar cycle, thereby conferring increased fitness. However, it is thought that the first archaic ‘proto-clocks’ evolved in ancient cyanobacteria in a marine environment, where the dominant time cues (zeitgebers) probably would have been lunar-driven and included tidal cycles. To date, non-circadian ‘marine clocks’ have been described with circatidal (~12.4 h), circasemilunar (~14.8 days), and circalunar (~29.5 days) periodicity, mostly studied in accessible but temporally complex intertidal habitats. In contrast to the well-described circadian clock, their molecular machinery is poorly understood, and fundamental mechanisms remain unclear. We propose that a multi-species approach is the most apposite strategy to resolve the divergence that arose from non-circadian clockwork forged in an evolutionary environment with multiple zeitgebers. We review circatidal clock models with a focus on intertidal organisms, for which robust behavioural, physiological, or genetic underpinnings have been explicated, and discuss their relative experimental merits. Developing a comprehensive mechanistic understanding of circatidal clocks should be a priority because it will ultimately contribute to a more holistic understanding of the origins and evolution of chronobiology itself.

Comparative Transcriptome Reveals the Molecular Regulation Mechanism of Charybdis japonica to High- and Low-Temperature Stresses

Intertidal organisms are more sensitive to temperature stresses (whether high or low temperatures). As an intertidal crustacean, the optimal survival temperature ranges of Charybdis japonica are from 20 to 27°C. In this study, C. japonica was selected as the research species to better explore the molecular regulatory mechanisms of intertidal crustaceans to temperature stresses. The transcriptomes of C. japonica exposed to three temperature gradients (12, 20, and 28°C) were sequenced. A total of 69.22 Gb clean transcriptome reads were obtained from nine libraries and then de novo assembled to 52,972 unigenes with a mean length of 1080.23 bp and an N50 length of 1,775 bp. A total of 20,121 unigenes were successfully matched with at least one protein database. The transcriptome structure was predicted, and 12,125 coding sequences and 12,854 simple sequence repeats (SSRs) were obtained. The gene expression level of C. japonica at 20°C was used as control, and 548 and 90 unigenes were significantly differentially expressed at 28 and 12°C, respectively. A total of 720 unigenes were significantly differentially expressed at 28°C compared with 12°C. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation showed that genes related to cell structure, metabolism, and protein folding and hormone synthesis might be involved in the regulation of temperature stress in C. japonica. Our results reveal for the first time the response of C. japonicas to low- and high- temperature stresses at the transcriptome level. The results provide fundamental information for revealing the temperature regulation mechanisms of C. japonica and other intertidal crustaceans. Furthermore, the present study enhances our understanding of how temperature fluctuations will affect the survival of marine crustaceans.

Cumulative stressors impact macrofauna differentially according to sandy beach type: A meta-analysis

Many studies have demonstrated human impacts on sandy beach macroinvertebrates. However, little is known about causative drivers among multiple co-occurring stressors and how these interact with natural habitat conditions to yield specific faunal responses. We performed a global meta-analysis to shed light on how interactions between human disturbances and beach morphodynamics shape macroinvertebrate populations. We found that supralittoral forms (Talitridae and Ocypodidae) responded more negatively to the Human Modification Metric (a proxy for urbanization) on dissipative beaches, whereas intertidal organisms (Hippidae and Cirolanidae) showed more negative responses on non-dissipative beaches. Based on these findings we propose the Cumulative Harshness Hypothesis (CHH), which predicts higher sensitivity of beach macroinvertebrates to human disturbances when inhabiting a harsher physical environment according to their life histories. Secondly, we compared the response of macroinvertebrates to urbanization levels from local to larger scales (from 500 to 50000 m). Supralittoral families responded more negatively to local urbanization, which leads to habitat loss due to removal or reduction of upper beach zones. Conversely, intertidal organisms with planktonic larval stages were more affected by urbanization at the largest spatial scales, which we hypothesize disrupts metapopulation dynamics by impacting the supply of larvae that could colonize human-disturbed beaches. The differential effects of human disturbances on macroinvertebrates according to beach morphodynamics suggest that the efficiency of these ecological indicators for beach monitoring is context-dependent. Focusing on multiple stressors rather than on a single one is also critical to mitigate human impacts on these threatened ecosystems.

Molecular Responses to Thermal and Osmotic Stress in Arctic Intertidal Mussels (Mytilus edulis): The Limits of Resilience.

Increases in Arctic temperatures have accelerated melting of the Greenland icesheet, exposing intertidal organisms, such as the blue mussel Mytilus edulis, to high air temperatures and low salinities in summer. However, the interaction of these combined stressors is poorly described at the transcriptional level. Comparing expression profiles of M. edulis from experimentally warmed (30 °C and 33 °C) animals kept at control (23‰) and low salinities (15‰) revealed a significant lack of enrichment for Gene Ontology terms (GO), indicating that similar processes were active under all conditions. However, there was a progressive increase in the abundance of upregulated genes as each stressor was applied, with synergistic increases at 33 °C and 15‰, suggesting combined stressors push the animal towards their tolerance thresholds. Further analyses comparing the effects of salinity alone (23‰, 15‰ and 5‰) showed high expression of stress and osmoregulatory marker genes at the lowest salinity, implying that the cell is carrying out intracellular osmoregulation to maintain the cytosol as hyperosmotic. Identification of aquaporins and vacuolar-type ATPase transcripts suggested the cell may use fluid-filled cavities to excrete excess intracellular water, as previously identified in embryonic freshwater mussels. These results indicate that M. edulis has considerable resilience to heat stress and highly efficient mechanisms to acclimatise to lowered salinity in a changing world.

Sub-lethal and lethal effects of chronic and extreme multiple stressors on a critical New Zealand bivalve under hypoxia

Warming of coastal regions due to climate change is exerting chronic thermal stress on intertidal organisms, many of which are already living at or near their limits for thermal tolerance. In addition, increasing frequency of marine heat waves and algal blooms leading to hypoxic events in estuaries exert acute stresses on aerobic organisms. Hypoxia and warming rarely occur in isolation, and when combined, likely have synergistic detrimental effects on bivalves. Further, midday low tides have been identified as important drivers of mass mortality events for bivalves as a consequence of the combined effects of thermal stress and desiccation. Accordingly, the current study focuses on the sublethal and lethal effects of these combined stressors on the critical estuarine bivalve Austrovenus stutchburyi. Experiments were used to test the effects of simulated midday low tides combined with chronic warming and oxygen depletion on activity, respiration and survival of A. stutchburyi. A lethal emersion thermal threshold was surpassed at 33°C for treatments exposed to both hypoxic and normoxic treatments, suggesting extreme thermal events such as heatwaves during midday low tides could have substantial detrimental effects on bivalve populations and their vital ecosystem functions. Further, the ability of bivalves to survive heat and desiccation of midday low tide events was much reduced when they were exposed to even minor heat and hypoxia stress when immersed at high tide. The findings of the current study highlight important biological consequences of coastal warming combined with extreme temperature and hypoxic events observed in estuaries.

Tissue- and substrate-dependent mitochondrial responses to acute hypoxia–reoxygenation stress in a marine bivalve (Crassostrea gigas )

Hypoxia is a major stressor for aquatic organisms, yet intertidal organisms such as the oyster Crassostrea gigas are adapted to frequent oxygen fluctuations by metabolically adjusting to shifts in oxygen and substrate availability during hypoxia-reoxygenation (H/R). We investigated the effects of acute H/R stress (15 min at ∼0% O2 and 10 min reoxygenation) on isolated mitochondria from the gill and the digestive gland of C. gigas respiring on different substrates (pyruvate, glutamate, succinate, palmitate and their mixtures). Gill mitochondria showed better capacity for amino acid and fatty acid oxidation compared with mitochondria from the digestive gland. Mitochondrial responses to H/R stress strongly depended on the substrate and the activity state of mitochondria. In mitochondria oxidizing NADH-linked substrates, exposure to H/R stress suppressed oxygen consumption and generation of reactive oxygen species (ROS) in the resting state, whereas in the ADP-stimulated state, ROS production increased despite little change in respiration. As a result, electron leak (measured as H2O2 to O2 ratio) increased after H/R stress in the ADP-stimulated mitochondria with NADH-linked substrates. In contrast, H/R exposure stimulated succinate-driven respiration without an increase in electron leak. Reverse electron transport (RET) did not significantly contribute to succinate-driven ROS production in oyster mitochondria except for a slight increase in the OXPHOS state during post-hypoxic recovery. A decrease in NADH-driven respiration and ROS production, enhanced capacity for succinate oxidation and resistance to RET might assist in post-hypoxic recovery of oysters mitigating oxidative stress and supporting rapid ATP re-synthesis during oxygen fluctuations, as is commonly observed in estuaries and intertidal zones.

Mesoscale patterns in barnacle reproduction are mediated by upwelling-driven thermal variability

Environmental variables are known to regulate the reproductive output of marine intertidal organisms, but typically these variables are studied as averages and interpreted at a macroscale level. Along 200 km of coast in NW Iberia, great variability in the reproductive activity of the stalked barnacle Pollicipes pollicipes was found among 7 different locations. We found the highest number of broods reported to date in this species and suggest a more realistic method of predicting reproductive success that takes into account sea surface temperature (SST). At these same locations, we studied 13 yr of SST, thermal upwelling index (UI), ground skin temperature and chlorophyll a (chl a) satellite data, using spectral analyses to partition their temporal variability over ecologically relevant time scales. SST played the most relevant role as an environmental driver, explaining 48% of the variability in the proportion of breeding individuals (BI), but the SST-BI goodness-of-fit decreased sharply northwards. Variance-partitioning analyses indicated that cycles between 20 and 100 d in SST and UI were more important southwards, which is consistent with a latitudinal gradient in upwelling intensity and frequency along this coast. Thus, we found better biophysical coupling towards the south, where shorter fluctuation time scales in SST match the gonadal development period (around 1 mo). This pattern may explain the spatial variability in the strength of association between key environmental variables and the reproductive cycle of coastal species along their distribution range.

Differential tolerance capacity of intertidal organisms (sponge and zoanthid) to the environmental stresses: Preliminary findings from a rockpool transplantation experiment

Differential tolerance capacity of intertidal organisms (sponge and zoanthid) to the environmental stresses: Preliminary findings from a rockpool transplantation experiment

Thermal sensitivity in dual‐breathing ectotherms: Embryos and mothers determine species' vulnerability to climate change

AbstractUnderstanding the life‐stage specific vulnerability of ectotherms to temperature increases is crucial to accurately predicting the consequences of current and future global climate change. Here, we examined ontogeny‐specific thermal vulnerability of three intertidal, bimodal (i.e., air and water) breathing crabs from tropical and warm temperate latitudes to address this issue. Spawning females and embryos of intertidal crabs from warm temperate latitudes were more vulnerable to temperature increases than tropical conspecifics, particularly in water. Our findings do not fully support the Climate Variability Hypothesis for setting upper thermal limits, but correspond with the Oxygen‐ and Capacity‐Limited Thermal Tolerance hypothesis, suggesting ontogeny‐specific aerobic capacity dictates overall species' thermal sensitivity. Bimodal breathing efficiency as an evolutionary adaptation, ontogenetic stage and local climate adaptation are therefore significant factors to consider when evaluating the vulnerability of intertidal ectotherms to temperature increases and the consequences of climate changes for intertidal organisms, populations and communities.

Distribution, annual committed effective dose, and health safety assessment of 210Po in marine biota from Kalpakkam coast, Bay of Bengal

Seafood, intertidal biota, beach sediment, and seawater from Kalpakkam coast, Bay of Bengal were analyzed for 210Po to evaluate the internal exposure and other radiological safety aspects. Kalpakkam houses various nuclear power generation facilities on its coast. The activity concentration of 210Po was more pronounced in the intertidal organisms. Pelagic planktivorous fishes have the highest activity of the non-technogenic radionuclide, followed by the detrital feeders, benthic planktivores, benthic carnivores, and pelagic carnivore fishes. The affinity of 210Po to organic detrital matter and planktonic organisms has led to a higher accumulation of radionuclide in planktivorous fishes. Activity concentration of 210Po in seafood ranged between 1.13 ± 0.3 and 96.71 ± 1.6 Bq kg−1 (Becquerel/kilogram). In seaweeds and gastropods, it ranged from 2.09 ± 0.2 to 8.21 ± 0.6 and from 9.31 ± 0.7 to 21.58 ± 1.2 Bq kg−1, respectively. The committed effective dose (CED) of 210Po in seafood varied from 31.18 to 456.68 μSv yr−1 (microSievert/year). Radiological hazard parameters, such as activity intake, CED in consumption, of the seafood from this coast are within the acceptable levels prescribed by the International Commission on Radiological Protection and US Environmental Protection Agency.

An integrated, multi-level analysis of thermal effects on intertidal molluscs for understanding species distribution patterns.

Elucidating the physiological mechanisms that underlie thermal stress and discovering how species differ in capacities for phenotypic acclimatization and evolutionary adaptation to this stress is critical for understanding current latitudinal and vertical distribution patterns of species and for predicting their future state in a warming world. Such mechanistic analyses require careful choice of study systems (species and temperature-sensitive traits) and design of laboratory experiments that reflect the complexities of in situ conditions. Here, we critically review a wide range of studies of intertidal molluscs that provide mechanistic accounts of thermal effects across all levels of biological organization - behavioural, organismal, organ level, cellular, molecular, and genomic - and show how temperature-sensitive traits govern distribution patterns and capacities for coping with thermal stress. Comparisons of congeners from different thermal habitats are especially effective means for identifying adaptive variation. We employ these mechanistic analyses to illustrate how species differ in the severity of threats posed by rising temperature. Counterintuitively, we show that some of the most heat-tolerant species may be most threatened by increases in temperatures because of their small thermal safety margins and minimal abilities to acclimatize to higher temperatures. We discuss recent molecular biological and genomic studies that provide critical foundations for understanding the types of evolutionary changes in protein structure, RNA secondary structure, genome content, and gene expression capacities that underlie adaptation to temperature. Duplication of stress-related genes, as found in heat-tolerant molluscs, may provide enhanced capacity for coping with higher temperatures. We propose that the anatomical, behavioural, physiological, and genomic diversity found among intertidal molluscs, which commonly are of critical importance and high abundance in these ecosystems, makes this group of animals a highly appropriate study system for addressing questions about the mechanistic determinants of current and future distribution patterns of intertidal organisms.