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Amphibians and fishes play a central role in shaping the structure and function of freshwater environments. These organisms have a limited capacity to disperse across different habitats and the thermal buffer offered by freshwater systems is small. Understanding determinants and patterns of their physiological sensitivity across life history is, therefore, imperative to predicting the impacts of climate change in freshwater systems. Based on a systematic literature review including 345 experiments with 998 estimates on 96 amphibian (Anura/Caudata) and 93 freshwater fish species (Teleostei), we conducted a quantitative synthesis to explore phylogenetic, ontogenetic, and biogeographic (thermal adaptation) patterns in upper thermal tolerance (CTmax) and thermal acclimation capacity (acclimation response ratio, ARR) as well as the influence of the methodology used to assess these thermal traits using a conditional inference tree analysis. We found globally consistent patterns in CTmax and ARR, with phylogeny (taxa/order), experimental methodology, climatic origin, and life stage as significant determinants of thermal traits. The analysis demonstrated that CTmax does not primarily depend on the climatic origin but on experimental acclimation temperature and duration, and life stage. Higher acclimation temperatures and longer acclimation times led to higher CTmax values, whereby Anuran larvae revealed a higher CTmax than older life stages. The ARR of freshwater fishes was more than twice that of amphibians. Differences in ARR between life stages were not significant. In addition to phylogenetic differences, we found that ARR also depended on acclimation duration, ramping rate, and adaptation to local temperature variability. However, the amount of data on early life stages is too small, methodologically inconsistent, and phylogenetically unbalanced to identify potential life cycle bottlenecks in thermal traits. We, therefore, propose methods to improve the robustness and comparability of CTmax/ARR data across species and life stages, which is crucial for the conservation of freshwater biodiversity under climate change. [ABSTRACT FROM AUTHOR]

ABSTRACT Temperature is one of the main factors influencing biological processes of ectothermic species. An optimum temperature of 16-18[degrees]C has been suggested for the development of early life stages of [...]

ABSTRACT On Australian aquaculture farms, early life stages of abalone are reared under controlled abiotic and biotic conditions in an attempt to optimize individual growth and reduce potential stressors. Yet, [...]

During development crustaceans experience a range of oxygen tensions (PO.sub.2) in their various developmental environments. Therefore, it is likely that they developed varying strategies to respond to hypoxic events during their ontogeny. We investigated short-term responses to various oxygen levels in early life stages of two anomuran decapods Petrolisthes laevigatus and Lithodes santolla that develop in different habitats. Embryos and juveniles of P. laevigatus inhabit the upper rocky intertidal and are regularly exposed to hypoxia during low tide, while larvae of this species inhabit well-oxygenated surface waters. L. santolla is a subtidal species that inhabits fjords and is frequently exposed to hypoxia due to stratification in this environment. Oxygen consumption (MO.sub.2), lactate content, RNA/DNA ratio, lactate dehydrogenase and superoxide dismutase (SOD) activities were measured in embryos, larvae and juveniles after exposure to PO.sub.2s of 3-21 kPa for 24 h. Results indicated considerable variation in hypoxia tolerances among the ontogenetic stages of both species. Embryos of both species relied on anaerobiosis at all tested PO.sub.2 yet were able to regulate MO.sub.2 until 15 kPa. In contrast, larvae of L. santolla were oxyconformers, while those of P. laevigatus continued to oxyregulate in conjunction with a decrease in SOD activities in response to low PO.sub.2. Juveniles of P. laevigatus were more sensitive to hypoxia than those of L. santolla as all tested parameters were affected at higher PO.sub.2 in the former. This study shows that aerobic and anaerobic metabolism, antioxidant defence and protein synthesis of early life stages are diverse and reflect the variety of inhabited environments., Author(s): Katharina Alter[sup.1] [sup.5] , Kurt Paschke[sup.2] , Paulina Gebauer[sup.3] , Juan-Pablo Cumillaf[sup.2] , Hans-Otto Portner[sup.4] Author Affiliations: (1) Universität Bremen, Bremen, Germany (2) Instituto de Acuicultura, Universidad Austral de [...]

In marine fishes, the timing of spawning determines the environment offspring will face and, therefore, the chances of early life stage survival. Different waves of Atlantic herring Clupea harengus spawn throughout spring in the western Baltic Sea, and the survival of offspring from early in the season has been low in the most recent decade. The authors assessed changes in egg traits from early, middle and late phases of the spawning season to examine whether seasonal and/or maternal effects influenced embryo survival. At each phase, fertilized eggs of six to eight females were incubated at two temperatures (7 and 13°C), and egg size, fertilization success, mortality and time to hatch were recorded. A compilation of data from 2017 to 2020 spawning seasons indicated that mean total length of females decreased with progression of the season and increasing in situ water temperature. For the sub‐set of females used in the laboratory study, early spawners were 7.6% larger and produced 14.2% larger eggs than late‐spring spawners. Fertilization success was consistently high (>90%), and mortality to hatch was low (<3%). Neither the former nor latter were influenced by season, but both were influenced by maternity. This significant female effect was, however, not related to any maternal trait measured here (total length, Fulton's condition factor or age). There was no maternal effect on development rate at 7 or 13°C. The results suggest that intrinsic differences among females or among spawning waves are unlikely to markedly contribute to the poor survival observed for progeny from early in the season in this population and point towards other extrinsic factors or processes acting on eggs or early larval stages (e.g., seasonal match–mismatch dynamics with prey) as more likely causes of mortality. [ABSTRACT FROM AUTHOR]

The European Union's Habitats Directive has the obligation to restore natural habitats in order to increase biodiversity within Europe. The European flat oyster Ostrea edulis is a favorable habitat builder for ecological restoration for which large amounts of spat are needed. Yet, the supply of spat is a key limiting factor because rearing protocols for O. edulis have not been optimized. This study reports on successful hatchery production of O. edulis reared at different temperature regimes with the aim to determine the most suitable thermal condition for early-life growth and survival. Larvae were reared at 25 and 29 °C until they were competent for settlement. Then, the larval batch at either temperature was split into two. One half of the batch remained at the original temperature while the other half was exposed to another temperature (25 or 29 °C) until 14 days post settlement. Larval size was similar among temperature treatments until 10 days post release, after which larvae reared at 29 °C were slightly (3%) larger compared to those reared at 25 °C (p < 0.05). The percentage of larvae which developed competence for settlement was not different (p > 0.05) between 25 °C (37 ± 4%) and 29 °C (33 ± 4%). Two weeks post settlement, size of the spat reared at 29 °C with a larval thermal history of 25 °C was 23% larger (p < 0.05) compared to O. edulis constantly reared at either 29 or 25 °C. Spat survival, which varied between 29 ± 6% and 56 ± 15% among treatments, was not related to rearing temperatures during the larval and early benthic phase (p > 0.05). Spat reached a size at which they are suitable for release into restoration sites within two weeks, resulting in a hatchery period of as little as three weeks. Our results contribute to the optimization of O. edulis hatchery protocols to improve yields for a growing demand of spat used in ecological restoration. • Supply of spat is a key limiting factor for ecological restoration. • Rearing protocol for flat oysters was not reliable. • We used two high temperatures which were either stable or switched at settlement. • A temperature increase at settlement resulted in 10–23% increased spat growth. • Spat nursery/market size can be reached within a three week hatchery period. [ABSTRACT FROM AUTHOR]

Many abalone farms are reliant on coastal water inputs which are subject to fluctuations in environmental variables such as temperature, oxygen, CO2 and salinity. Near future climate change scenarios predict that there will be more frequent extreme weather events which can exacerbate these fluctuations and potentially be deleterious to farmed abalone where these variables remain largely uncontrolled. In this review, we have taken an in depth examination of current literature on the effects of environmental stress on abalone physiology and metabolism and how this affects their health and growth. In conjunction, we have also reviewed the effects of farm-specific stressors such as ammonia, stocking density, handling, nutrition and disease and the synergistic effects of these and environmental stressors on abalone physiology. We have identified currents gaps in our knowledge of this under-studied species and have made predictions on the effects of climate change on future abalone production with suggestions for future research. In summary, it is expected that abalone will show reduced growth rates as more energy is invested in combating stresses rather than growth. Furthermore, disease outbreaks may become more frequent with greater fluctuations in temperature and salinity, both of which have large-scale effects on immunity. The current body of knowledge is mainly on whole animal effects of stresses, but we know very little of their mechanistic foundation. Research in this area as well as investments in infrastructure will be pivotal in identifying and implementing strategic interventions to maintain a sustainable abalone industry in Australia. [ABSTRACT FROM AUTHOR]

We evaluated the effects of projected, near future ocean acidification (OA) and extreme events of temperature (warming or cooling) on the thermal tolerance of Concholepas concholepas , a coastal benthic keystone species. Three separate trials of an experiment were conducted by exposing juvenile C. concholepas for 1 month to one of two contrasting p CO 2 levels (~500 and ~1200 μatm). In addition, each p CO 2 level was combined with one of four temperature treatments. The control was 15 °C, whilst the other temperatures were 10 °C (Trial 1), 20 °C (Trial 2) and 25 °C (Trial 3). At the end of each trial, we assessed Critical Thermal maximum (CTmax) and minimum (CTmin) via self-righting success, calculated partial thermal tolerance polygons, measured somatic growth, determined transcription of Heat Shock Proteins 70 (HSP70) and measured oxygen consumption rates. Regardless of p CO 2 level, HSP70 transcript levels were significantly higher in juveniles after exposure to extreme temperatures (10 °C and 25 °C) indicating physiological stress. Oxygen consumption rates increased with increasing temperature from 10 °C to 20 °C though showed a decrease at 25 °C. This rate was not affected by p CO 2 or the interaction between temperature and p CO 2. Juveniles exposed to present-day and near future p CO 2 levels at 20 °C showed similar thermal tolerance polygonal areas; whilst changes in both CTmin and CTmax at 25 °C and 10 °C caused narrower and broader areas, respectively. Temperature affected growth, oxygen consumption and HSP70 transcription in small juvenile C. concholepas. Exposure to elevated p CO 2 did not affect thermal tolerance, growth or oxygen consumption at temperatures within the thermal range normally experienced by this species in northern Chile (15-20 °C). At elevated p CO 2 conditions, however, exposure to warmer (25 °C) or colder (10 °C) temperatures reduced or increased the thermal area, respectively. This study demonstrates the importance of examining the thermal-tolerance edges to better understand how OA and temperature will combine to physiologically challenge inter-tidal organisms. Laboratory experiments examined the effect of near-future changes in temperature (cooling and warming) and elevated p CO 2 levels (acidification) on small juveniles of the keystone predator species Concholepas concholepas using self-righting success as end points for thermal tolerance. Survival, metabolism and HSP70 transcription were also investigated. Extreme cooling and warming under near-future p CO 2 levels reduced the partial thermal tolerance polygons, growth and metabolism whilst increased HSP70 transcription in comparison to present-day conditions. Although survival was not affected, the results indicate that near-future conditions of cooling or warming may potentially disrupt the performance and narrow the distribution of this species with potential ecological and economic consequences. Unlabelled Image • At 20 °C at both p CO 2 levels similar thermal tolerance polygons were obtained. • Acidification expanded the thermal tolerance polygons at 10 °C. • Acidification reduced the thermal tolerance polygons at 25 °C. • Regardless of the p CO 2 levels, growth increased from 10 °C to 20 °C acclimation • Regardless of the p CO 2 levels, growth was reduced when individuals were acclimated to 25 °C [ABSTRACT FROM AUTHOR]