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The term 'carryover effect' originally arose from repeated measures clinical experiments. However, the term has more recently been applied to ecological and evolutionary studies, often in migratory systems, which has led to an emphasis on non-lethal effects across seasons. In this article, we suggest that ecological carryover effects can also occur between life-history stages, developmental stages, physiological states, or social situations, and each will be associated with a discrete time-scale. Therefore, we propose the working definition: In an ecological context, carryover effects occur in any situation in which an individual's previous history and experience explains their current performance in a given situation . This concept of carryover effects provides an explicit but highly flexible context for examining the mechanisms that drive non-lethal interactions between distinct periods of an organism's lifetime, and unites the currently disparate fields investigating these effects in ecological systems. Greater communication among research fields and identifying mechanisms of carryover effects at different time scales will ultimately lead to a better understanding of the factors influencing variation in individual fitness.

Organisms are increasingly likely to be exposed to multiple stressors repeatedly across ontogeny as climate change and other anthropogenic stressors intensify. Early life stages can be particularly sensitive to environmental stress, such that experiences early in life can “carry over” to have long-term effects on organism fitness. Despite the potential importance of these within-generation carryover effects, we have little understanding of how they vary across ecological contexts, particularly when organisms are re-exposed to the same stressors later in life. In coastal marine systems, anthropogenic nutrients and warming water temperatures are reducing average dissolved oxygen (DO) concentrations while also increasing the severity of naturally occurring daily fluctuations in DO. Combined effects of warming and diel-cycling DO can strongly affect the fitness and survival of coastal organisms, including the eastern oyster (Crassostrea virginica), a critical ecosystem engineer and fishery species. However, whether early life exposure to hypoxia and warming affects oysters’ subsequent response to these stressors is unknown. Using a multiphase laboratory experiment, we explored how early life exposure to diel-cycling hypoxia and warming affected oyster growth when oysters were exposed to these same stressors 8 weeks later. We found strong, interactive effects of early life exposure to diel-cycling hypoxia and warming on oyster tissue : shell growth, and these effects were context-dependent, only manifesting when oysters were exposed to these stressors again two months later. This change in energy allocation based on early life stress exposure may have important impacts on oyster fitness. Exposure to hypoxia and warming also influenced oyster tissue and shell growth, but only later in life. Our results show that organisms’ responses to current stress can be strongly shaped by their previous stress exposure, and that context-dependent carryover effects may influence the fitness, production, and restoration of species of management concern, particularly for sessile species such as oysters.

The spread of marine non-indigenous species (NIS) is driven largely by shipping and global trade. Biofouling on vessel hulls is a major source of invasions, but many biofouling organisms are sessile (non-motile) and require reproduction, which often produces mobile, waterborne propagules (e.g., larvae) that can colonize new regions. The ability of biofouling organisms to reproduce, however, can depend strongly on abiotic conditions at the time of reproduction but also potentially prior to any reproductive event. For many organisms, past environments can influence performance later in life via within-generation carryover effects, but how carryover effects influence potential NIS introductions is unclear. We conducted a laboratory experiment to explore within-generation carryover effects of salinity and how they operate across different environments in the barnacle Amphibalanus improvisus, a common biofouling organism. We exposed newly settled barnacles to two different salinities (15 and 28 psu) for three weeks, maintained them in a common salinity for five weeks, then re-exposed them to the two initial salinities in a fully-factorial design prior to measuring their reproductive output. We found that barnacles that switched salinities between the initial and final exposures tended to produce more nauplii larvae (up to 50%) than those that remained in the same salinity conditions, possibly because of a stress response induced by physiological acclimation to early life environments. Because adult biofouling species are likely to be exposed to variable environmental conditions during vessel transits, carryover effects and their impact on propagule output may be important to consider when evaluating potential NIS introductions via biofouling.

Environmentally cued plasticity in hatching timing is widespread in animals. As with later life-history switch points, plasticity in hatching timing may have carryover effects that affect subsequent interactions with predators and competitors. Moreover, the strength of such effects of hatching plasticity may be context dependent. We used red-eyed treefrogs, Agalychnis callidryas , to test for lasting effects of hatching timing (four or six days post-oviposition) under factorial combinations of resource levels (high or low) and predation risk (none, caged, or lethal Pantala flavescens dragonfly naiads). Tadpoles were raised in 400-L mesocosms in Gamboa, Panama, from hatching until all animals had metamorphosed or died, allowing assessment of effects across a nearly six-month period of metamorphosis. Hatching early reduced survival to metamorphosis, increased larval growth, and had context-dependent effects on metamorph phenotypes. Early during the period of metamorph emergence, early-hatched animals were larger than late-hatched ones, but this effect attenuated over time. Early-hatched animals also left the water with relatively longer tails. Lethal predators dramatically reduced survival to metamorphosis, with most mortality occurring early in the larval period. Predator effects on the timing of metamorphosis and metamorph size and tail length depended upon resources. For example, lethal predators reduced larval periods, and this effect was stronger with low resources. Predators affected metamorph size early in the period of metamorphosis, whereas resource levels were a stronger determinant of phenotype for animals that metamorphosed later. Effects of hatching timing were detectable on top of strong effects of larval predators and resources, across two subsequent life stages, and some were as strong as or stronger than effects of resources. Plasticity in hatching timing is ecologically important and currently underappreciated. Effects on metamorph numbers and phenotypes may impact subsequent interactions with predators, competitors, and mates, with potentially cascading effects on recruitment and fitness.

Most marine invertebrate larvae either feed or rely on reserves provisioned by parents to fuel development, but facultative feeders can do both. Food availability and temperature are key environmental drivers of larval performance, but the effects of larval experience on performance later in life are poorly understood in facultative feeders. In particular, the functional relevance of facultative feeding is unclear. One feature to be tested is whether starved larvae can survive to adulthood and reproduce. We evaluated effects of larval temperature and food abundance on performance in a marine harpacticoid copepod, Tisbe sp. In doing so, we report the first example of facultative feeding across the entire larval stage for a copepod. In a series of experiments, larvae were reared with ad libitum food or with no food, and at 2 different temperatures (20 vs. 24°C). We found that higher temperatures shortened development time, and larvae reared at higher temperature tended to be smaller. Larval food consistently improved early performance (survival, development rate and size) in larvae, while starvation consistently decreased survival, increased development time and decreased size at metamorphosis. Nonetheless, a small proportion (3–9.5%, or 30–42.7% with antibiotics) of larvae survived to metamorphosis, could recover from a foodless larval environment, reach maturity and successfully reproduce. We recommend that future studies of facultative feeding consider the impact of larval environments on adult performance and ability to reproduce.

We consider the analysis of continuous repeated measurement outcomes that are collected longitudinally. A standard framework for analysing data of this kind is a linear Gaussian mixed effects model within which the outcome variable can be decomposed into fixed effects, time invariant and time-varying random effects, and measurement noise. We develop methodology that, for the first time, allows any combination of these stochastic components to be non-Gaussian, using multivariate normal variance–mean mixtures. To meet the computational challenges that are presented by large data sets, i.e. in the current context, data sets with many subjects and/or many repeated measurements per subject, we propose a novel implementation of maximum likelihood estimation using a computationally efficient subsampling-based stochastic gradient algorithm. We obtain standard error estimates by inverting the observed Fisher information matrix and obtain the predictive distributions for the random effects in both filtering (conditioning on past and current data) and smoothing (conditioning on all data) contexts. To implement these procedures, we introduce an R package: ngme. We reanalyse two data sets, from cystic fibrosis and nephrology research, that were previously analysed by using Gaussian linear mixed effects models.

The muricid gastropod Acanthina monodon deposits egg capsules in both subtidal and intertidal environments. Intertidal egg capsules are naturally exposed during low tides to sublethal environmental stressors, including desiccation and fluctuations in temperature and salinity. This study was undertaken to determine if juveniles hatching from intertidal egg capsules show reduced rates of feeding or growth. This research therefore compares the performance of juveniles during the first month of post-hatching life, according to whether the juveniles had developed in capsules that had been naturally deposited intertidally or subtidally. We found that juveniles that hatched from intertidal egg capsules grew more slowly than those that hatched from subtidally collected capsules. Moreover, juveniles that hatched from intertidal egg capsules consumed fewer prey per week and ate more slowly than those that hatched from subtidal capsules, although by the end of the study, the total dry weight of juveniles from the two environments was no longer significantly different. Even so, the final mean organic content of juveniles that had hatched from subtidal capsules was significantly higher than that of juveniles that had hatched from capsules of intertidal origin, suggesting that the juveniles from intertidal egg capsules prioritized inorganic shell growth over tissue growth. These results suggest that the intertidal placement of egg capsules imposes stresses on embryos that subsequently reduce rates of juvenile feeding and shell growth, demonstrating how sublethal stresses experienced during early, pre-hatching development in the field interacting with likely maternal effects can produce deleterious latent effects in later life.

Oil spills cause damage to marine wildlife that lasts well past their immediate aftermath. Marine offspring that must settle and metamorphose to reach adulthood may be particularly prone to harm if the legacy of oil exposure interrupts later transitions across life stages. Following an oil spill on Curaçao, we found that oil-contaminated seawater reduced settlement of 2 coral species by 85% and 40% after exposure had ended. The effect of contamination on settlement was more severe than any direct or latent effects on survival. Therefore, oil exposure reduces the ability of corals to transition to their adult life stage, even after they move away from oil contamination. This interruption of the life cycle likely has severe consequences for recruitment success in these foundational and threatened organisms. Latent, sublethal, and behavioral effects on marine organisms—as shown in this study—are not commonly considered during oil-spill impact assessments, increasing the likelihood that harm to marine species goes underestimated or unmeasured.

Exposure to environmental stressors such as pollutants early in life may have latent effects visible only in later life stages. Sea urchin Evechinus chloroticus larvae were exposed briefly (2 d) to 4 treatments of low levels of copper (2 to 10 μg l−1). Juveniles were re-exposed to a further short pulse of copper (10 μg l−1) to investigate potential resistance to pollution. No major direct effects of larval exposure to copper were observed on larval growth, survival or settlement success. However, complex latent effects started to appear from 8 d post-settlement onwards in individuals exposed as larvae to the highest concentration of copper. Juveniles had strongly impaired growth from 8 to 25 d post-settlement, with average radial length and spine to body ratio decreasing by 24% for both variables. In addition, juveniles previously exposed to the highest tested concentration of copper as larvae were more vulnerable to a subsequent pulse, with up to 4 times higher mortality in groups previously exposed to copper during the larval stage. On the other hand, survivors had a 35% higher growth rate than naive juveniles (i.e. no previous exposure). These results demonstrate that exposure to a concentration of copper similar to that found in many polluted bays and harbours (10 μg l−1) for as little as 48 h in early life impacts juvenile performance and leaves them more vulnerable to a subsequent exposure. This highlights the importance of considering latent effects when evaluating the impacts of pollution.

We estimate fundamental pricing relationships in selected European day-ahead electricity markets. Using a fractionally integrated panel data model with unobserved common effects, we quantify the responsiveness of hourly electricity prices to two fundamental leading indicators of day-ahead markets: the predicted load and renewable generation. The application of fractional cointegration analysis techniques gives further insight into the pricing mechanism of power delivery contracts, enabling us to measure the persistence of fundamental shocks.