Posts Tagged 'crustaceans'

Ocean warming increases availability of crustacean prey via riskier behavior

Marine prey and predators will respond to future climate through physiological and behavioral adjustments. However, our understanding of how such direct effects may shift the outcome of predator–prey interactions is still limited. Here, we investigate the effects of ocean warming and acidification on foraging behavior and biomass of a common prey (shrimps, Palaemon spp.) tested in large mesocosms harboring natural resources and habitats. Acidification did not alter foraging behavior in prey. Under warming, however, prey showed riskier behavior by foraging more actively and for longer time periods, even in the presence of a live predator. No effects of longer-term exposure to climate stressors were detected on prey biomass. Our findings suggest that ocean warming may increase the availability of some prey to predators via a behavioral pathway (i.e., increased risk-taking by prey), likely by elevating metabolic demand of prey species.

Continue reading ‘Ocean warming increases availability of crustacean prey via riskier behavior’

Impacts of ocean acidification on intertidal macroalgae and algivore preference

Ocean acidification, a facet of global climate change, has the potential to induce changes in marine macroalgae that modify their existing interactions with algivorous invertebrates. In this study, I examined the effects of elevated carbon dioxide (pCO2) on several species of intertidal macroalgae (Phaeophyta, Rhodophyta) and evaluated the present-day and predicted future preferences of algivores (Pugettia producta and Tegula funebralis) by assessing grazing rates on untreated algal tissue and on algae exposed to high-pCO2 seawater. Both red and brown algae grew faster in elevated pCO2 than in ambient seawater, and algae in intermediate pCO2 generated more new growth overall than those in highly elevated pCO2. The effect of pCO2 on the carbon and nitrogen contents of algae depended on species identity, and C:N ratios decreased slightly with increasing pCO2 for four of the five species studied. Total phenolic content in each alga was unaffected by pCO2 treatment, although similar (distinct) levels between untreated species became distinct (similar) when those same species were compared after highpCO2 treatment. Algivores demonstrated contrasting responses to changes in their food sources; P. producta, a specialist crab grazer, did not modify its preference for the brown alga Egregia menziesii when offered high-pCO2 treated individuals, but the generalist snail T. funebralis adjusted its feeding behavior to choose algae with low phenolic contents, which created different patterns of preference for untreated and pCO2-treated algae. C:N ratios of algae did not appear to be a strong driver of preference for either grazer in feeding experiments. These results indicate that algae may be well-equipped to benefit from moderate increases in seawater pCO2, but they exhibit species-specific rates of growth and phenolic production, which in turn affect their appeal to a generalist algivore. Intertidal algal communities will therefore face altered patterns of predation under future ocean acidification conditions as generalist algivores adjust to new variation in algal palatability.

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Toward a mechanistic understanding of marine invertebrate behavior at elevated CO2

Elevated carbon dioxide (CO2) levels can alter ecologically important behaviors in a range of marine invertebrate taxa; however, a clear mechanistic understanding of these behavioral changes is lacking. The majority of mechanistic research on the behavioral effects of elevated CO2 has been done in fish, focusing on disrupted functioning of the GABAA receptor (a ligand-gated ion channel, LGIC). Yet, elevated CO2 could induce behavioral alterations through a range of mechanisms that disturb different components of the neurobiological pathway that produces behavior, including disrupted sensation, altered behavioral choices and disturbed LGIC-mediated neurotransmission. Here, we review the potential mechanisms by which elevated CO2 may affect marine invertebrate behaviors. Marine invertebrate acid–base physiology and pharmacology is discussed in relation to altered GABAA receptor functioning. Alternative mechanisms for behavioral change at elevated CO2 are considered and important topics for future research have been identified. A mechanistic understanding will be important to determine why there is variability in elevated CO2-induced behavioral alterations across marine invertebrate taxa, why some, but not other, behaviors are affected within a species and to identify which marine invertebrates will be most vulnerable to rising CO2 levels.

Continue reading ‘Toward a mechanistic understanding of marine invertebrate behavior at elevated CO2’

The effects of elevated temperature and PCO2 on the energetics and haemolymph pH homeostasis of juveniles of the European lobster, Homarus gammarus

Regulation of extracellular acid–base balance, while maintaining energy metabolism, is recognised as an important aspect when defining an organism’s sensitivity to environmental changes. This study investigated the haemolymph buffering capacity and energy metabolism (oxygen consumption, haemolymph [l-lactate] and [protein]) in early benthic juveniles (carapace length <40 mm) of the European lobster, Homarus gammarus, exposed to elevated temperature and PCO2. At 13°C, H. gammarus juveniles were able to fully compensate for acid–base disturbances caused by the exposure to elevated seawater PCO2 at levels associated with ocean acidification and carbon dioxide capture and storage (CCS) leakage scenarios, via haemolymph [HCO3−] regulation. However, metabolic rate remained constant and food consumption decreased under elevated PCO2, indicating reduced energy availability. Juveniles at 17°C showed no ability to actively compensate haemolymph pH, resulting in decreased haemolymph pH particularly under CCS conditions. Early benthic juvenile lobsters at 17°C were not able to increase energy intake to offset increased energy demand and therefore appear to be unable to respond to acid–base disturbances due to increased PCO2 at elevated temperature. Analysis of haemolymph metabolites suggests that, even under control conditions, juveniles were energetically limited. They exhibited high haemolymph [l-lactate], indicating recourse to anaerobic metabolism. Low haemolymph [protein] was linked to minimal non-bicarbonate buffering and reduced oxygen transport capacity. We discuss these results in the context of potential impacts of ongoing ocean change and CCS leakage scenarios on the development of juvenile H. gammarus and future lobster populations and stocks.

Continue reading ‘The effects of elevated temperature and PCO2 on the energetics and haemolymph pH homeostasis of juveniles of the European lobster, Homarus gammarus’

Effects of multiple stressors on the development and performance of decapod crustaceans

Many marine crustacean larvae develop in a relatively stable pelagic environment; therefore, they are likely to be sensitive to perturbations in their surrounding environmental conditions. Ocean Acidification (OA) is occurring on a globalised scale and may cause disruptions to crustacean larval survival. However, species and/or life history stages are not expected to respond uniformly to these near-future predicted changes. The performance of species that lack a compensatory capacity to cope with the changing conditions may potentially be detrimentally affected, which in turn may impact recruitment. In addition to this, little information exists surrounding the impacts of ocean acidification in conjunction with additional environmental stressors, such as salinity, temperature and food availability, which are predicted to covary with OA, upon brachyuran crustacean larvae. This research focused on the effects of elevated CO2, in combination with other environmental stressors, upon rates of larval development, performance and survival of a brachyuran crustacean species common to Europe (Carcinus maenas) and two species of shrimp (Palaemon serratus and Palaemon varians). These species have varying physiological abilities to cope with salinity change and such attributes may influence their capacities to survive elevated CO2 in combination with other environmental changes. Exposure of early larval stages to combinations of salinity, temperature and food limitation in C. maenas revealed that high temperature ameliorated the effect of low salinity on survival and developmental duration. Limited access to food also affected developmental duration, but exposure to elevated CO2 alone in a second experiment only affected survival, and low salinity alone had no effect. Exposure of early juvenile stages of C. maenas to CO2 and salinity, revealed that developmental duration was significantly affected by elevated CO2 and/or salinity at varying levels, whereas, for survival, such influences were only observed in later juvenile stages. These results suggest the possibility of a physiologically sensitive bottleneck within the life cycle of C. maenas. Exposure of early larval stages of the estuarine species, P. varians, to CO2 and salinity had no effect on either survival or developmental duration. For the predominantly coastal species, P. serratus, developmental duration was negatively influenced by the interaction of elevated CO2 and low salinity, but there was limited observed effect on overall survival at the early stages studied. Overall, evaluations of the effects of climate driven variables on physiological performance demonstrated that differences can occur among broods. In future, further studies are required to incorporate seasonal (and possibly spatial) variability in responses, due to maternal effects or phenotypic variation, as conclusions based on individuals collected over a short time frame are unlikely to fully represent population level responses.

Continue reading ‘Effects of multiple stressors on the development and performance of decapod crustaceans’

Short-term effects of hypoxia are more important than effects of ocean acidification on grazing interactions with juvenile giant kelp (Macrocystis pyrifera)

Species interactions are crucial for the persistence of ecosystems. Within vegetated habitats, early life stages of plants and algae must survive factors such as grazing to recover from disturbances. However, grazing impacts on early stages, especially under the context of a rapidly changing climate, are largely unknown. Here we examine interaction strengths between juvenile giant kelp (Macrocystis pyrifera) and four common grazers under hypoxia and ocean acidification using short-term laboratory experiments and field data of grazer abundances to estimate population-level grazing impacts. We found that grazing is a significant source of mortality for juvenile kelp and, using field abundances, estimate grazers can remove on average 15.4% and a maximum of 73.9% of juveniles per m2 per day. Short-term exposure to low oxygen, not acidification, weakened interaction strengths across the four species and decreased estimated population-level impacts of grazing threefold, from 15.4% to 4.0% of juvenile kelp removed, on average, per m2 per day. This study highlights potentially high juvenile kelp mortality from grazing. We also show that the effects of hypoxia are stronger than the effects of acidification in weakening these grazing interactions over short timescales, with possible future consequences for the persistence of giant kelp and energy flow through these highly productive food webs.

Continue reading ‘Short-term effects of hypoxia are more important than effects of ocean acidification on grazing interactions with juvenile giant kelp (Macrocystis pyrifera)’

The importance of environmental exposure history in forecasting Dungeness crab megalopae occurrence using J-SCOPE, a high-resolution model for the US Pacific Northwest

The Dungeness crab (Metacarcinus magister) fishery is one of the highest value fisheries in the US Pacific Northwest, but its catch size fluctuates widely across years. Although the underlying causes of this wide variability are not well understood, the abundance of M. magister megalopae has been linked to recruitment into the adult fishery 4 years later. These pelagic megalopae are exposed to a range of ocean conditions during their dispersal period, which may drive their occurrence patterns. Environmental exposure history has been found to be important for some pelagic organisms, so we hypothesized that inclusion of recent environmental exposure history would improve our ability to predict inter-annual variability in M. magister megalopae occurrence patterns compared to using “in situ” conditions alone. We combined 8 years of local observations of M. magister megalopae and regional simulations of ocean conditions to model megalopae occurrence using a generalized linear model (GLM) framework. The modeled ocean conditions were extracted from JISAO’s Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE), a high-resolution coupled physical-biogeochemical model. The analysis included variables from J-SCOPE identified in the literature as important for larval crab occurrence: temperature, salinity, dissolved oxygen concentration, nitrate concentration, phytoplankton concentration, pH, aragonite, and calcite saturation state. GLMs were developed with either in situ ocean conditions or environmental exposure histories generated using particle tracking experiments. We found that inclusion of exposure history improved the ability of the GLMs to predict megalopae occurrence 98% of the time. Of the six swimming behaviors used to simulate megalopae dispersal, five behaviors generated GLMs with superior fits to the observations, so a biological ensemble of these models was constructed. When the biological ensemble was used for forecasting, the model showed skill in predicting megalopae occurrence (AUC = 0.94). Our results highlight the importance of including exposure history in larval occurrence modeling and help provide a method for predicting pelagic megalopae occurrence. This work is a step toward developing a forecast product to support management of the fishery.

Continue reading ‘The importance of environmental exposure history in forecasting Dungeness crab megalopae occurrence using J-SCOPE, a high-resolution model for the US Pacific Northwest’

Can ocean acidification interfere with the ability of mud snails (Tritia obsoleta) to sense predators?

Highlights

• Mud snails respond differently to threat cues from crushed conspecifics and crabs

• Ocean acidification disrupted mud snail predator avoidance behavior

• Snails in acidified tanks crawled towards threat cues instead of away

• Acidification reduced snail crawling distance and climbing escape from threat cues

• Acidification may interfere with cue sensing and alter predator-prey relationships

Abstract

Nonlethal predator-prey interaction between Dyspanopeus sayi (northern mud crab) and Tritia obsoleta (mud snail) under ocean acidification conditions (OA) were investigated. Nonlethal interactions can influence predator-prey relationships and magnify the ecological impact of predators in marine habitats. Future increases in OA necessitate an understanding of how prey perceive the threat of predation and how this may be impacted by ocean acidification. In baseline experiments at pH 8.1, mud snails responded differently to crab cues compared to crushed conspecifics, burying in the presence of crushed conspecifics and fleeing in the presence of a mud crab. While many predator cue experiments combine these two types of cues, these results suggest that mud snails not only discern between threat cues but also have a nuanced response that is tailored to specific threats. Mud snail responses to predator-prey relationships were delayed under lower pH conditions, as snails in acidified treatments did not exhibit any of the escape responses that they commonly displayed under control conditions. Thus, acidification could shift predator-prey relationships and significantly alter food webs under acidified conditions.

Continue reading ‘Can ocean acidification interfere with the ability of mud snails (Tritia obsoleta) to sense predators?’

Model simulation of seasonal growth of Fucus vesiculosus in its benthic community

Numerical models are a suitable tool to quantify impacts of predicted climate change on complex ecosystems but are rarely used to study effects on benthic macroalgal communities. Fucus vesiculosus L. is a habitat‐forming macroalga in the Baltic Sea and alarming shifts from the perennial Fucus community to annual filamentous algae are reported. We developed a box model able to simulate the seasonal growth of the Baltic Fucus–grazer–epiphyte system. This required the implementation of two state variables for Fucus biomass in units of carbon (C) and nitrogen (N). Model equations describe relevant physiological and ecological processes, such as storage of C and N assimilates by Fucus, shading effects of epiphytes or grazing by herbivores on both Fucus and epiphytes, but with species‐specific rates and preferences. Parametrizations of the model equations and required initial conditions were based on measured parameters and process rates in the near‐natural Kiel Outdoor Benthocosm (KOB) experiments during the Biological Impacts of Ocean Acidification project. To validate the model, we compared simulation results with observations in the KOB experiment that lasted from April 2013 until March 2014 under ambient and climate‐change scenarios, that is, increased atmospheric temperature and partial pressure of carbon dioxide. The model reproduced the magnitude and seasonal cycles of Fucus growth and other processes in the KOBs over 1 yr under different scenarios. Now having established the Fucus model, it will be possible to better highlight the actual threat of climate change to the Fucus community in the shallow nearshore waters of the Baltic Sea.

Continue reading ‘Model simulation of seasonal growth of Fucus vesiculosus in its benthic community’

The challenge of scaling up from individual physiology to population level effects: using the Dynamic Energy Budget to describe and predict crustacean responses to climate variability

Predicting how marine communities will be affected by environmental change is one of the most significant challenges facing researchers today. In order to tackle this challenge, a mechanistic understanding of climate impacts at the individual level is necessary, as variations in species physiological responses are often reflected in patterns at higher organisational levels such as populations and communities. In order to explore the relationship between individual physiology and higher-level dynamics more fully, the swimming crab Liocarcinus depurator (Linnaeus, 1758) was selected as a model species for experimental work in which whole organism responses (growth, respiration and allocation to reproduction) to climate drivers were investigated using a bio-energetic modelling approach. This species was selected as a model organism after analysis of epibenthic time-series from the Western English Channel monitoring Station L4 revealed that decapod crustaceans played a key role in structuring the benthic community, and that L. depurator was one of the most dominant species in the area, in terms of both abundance and biomass. A bio-energetic approach was used as the same time-series analysis identified water temperature and seasonal phytodetrital input (e.g. food) as the predominant drivers of variation in benthic community wet biomass at L4, with the two drivers appearing to primarily influence community biomass at different times of the year. It is possible that warmer water temperatures in the autumn trigger gonad development and a consequent increase in reproductive biomass, while the sedimentation of the spring phytoplankton bloom drives an increase in somatic biomass. This time-series analysis clearly highlighted the role of organism energetics, and the environmental conditions that influence energy allocation, in structuring benthic communities. Further work elucidated the relationship between environmental variables and individual energy budgets. L. depurator responses to climate drivers (temperature, hypoxia and ocean acidification) were tested experimentally, and a mechanistic Dynamic Energy Budget (DEB) model was parameterised to describe the life history characteristics of crustaceans. At an individual level the model was able to accurately describe and predict observed responses to environmental drivers, both in isolation and in multiple stressor scenarios. Experimental results suggested that L. depurator was broadly tolerant of those climate drivers tested in the short term. Over the longer term however, model scenarios suggested that OA and the combined stressors may have an adverse effect on growth. When the multi-stressor model was forced with environmental projections from a coupled hydrodynamic-biogeochemical model (NEMO-ERSEM), it could be used to make predictions regarding ultimate carbon mass, age-at-maturity and cumulative allocation to reproduction, which were used to infer possible population level effects such as species distributions and population viability. Model scenarios suggested that, in the future, the optimum settlement time for juvenile L. depurator would shift forward across the north-west European shelf, and that this crustacean species may be able to expand its range further into the northern North Sea. The DEB model presented here can provide a mechanistic underpinning of observed species responses to climate drivers, and more broadly, the thesis demonstrates how multi-stressor models can be built from data collected in single stressor experiments, thereby providing a way of synthesising single stressor data into a modelling environment. This approach allows us to simulate more complex, ecologically relevant conditions. At a broader scale, the coupled DEB-ERSEM model showed that it can provide insight into why changes in species’ distributions are predicted, as these distributions are an emergent property of the processes being modelled.

Continue reading ‘The challenge of scaling up from individual physiology to population level effects: using the Dynamic Energy Budget to describe and predict crustacean responses to climate variability’


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Ocean acidification in the IPCC AR5 WG II

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