Posts Tagged 'predation'

Juvenile Dungeness crab foraging behavior and lipid composition is altered more by food quantity than seawater pH in a multi-stressor experiment

Published 29 March 2023 Science Closed
Tags: , , , , , ,

Highlights

  • We fed juvenile crab a maintenance- or low-quantity diet at ambient or reduced pH.
  • Foraging behaviors changed depending on diet and pH exposure but pH sensing did not.
  • Crab fatty acid composition was altered due to diet and pH exposure.
  • Crab lipid and fatty acid concentrations did not change due to pH exposure.
  • Crab in regions with pH and food supply variability may be resilient to reduced pH.

Abstract

Increases in atmospheric, anthropogenic carbon are driving reductions in seawater pH, a process referred to as ocean acidification. Reduced seawater pH can influence behavior of marine animals, but little is currently known about how juvenile crustaceans will respond. We conducted lab experiments to improve our understanding of the consequences of pH exposure and food quantity on juvenile Dungeness crab (Metacarcinus magister, (Dana, 1852)) behavior and nutritional condition. To understand the foraging and pH sensing behavior of juvenile crab, and how this interacts with their nutritional status, we exposed recently settled second instar juveniles to either ambient pH or reduced pH for 42-d, crossed with either a ‘maintenance’- or low-quantity ‘challenge’ diet treatment. After the experimental exposure period, we introduced crab into foraging and sensing pH behavior experiments. In the foraging experiment, we placed crab in a behavior arena with unidirectional flow, where we measured the food discovery time and time allocation of activities in 300-s trials for all individual crab. Food quantity and pH exposure influenced both the speed with which juvenile crab identified and allocation of activities but there was no interactive effect of experimental factors. For our pH sensing experiment, we used a two-current flume plumbed with both ambient and reduced pH seawater. This flow-through flume provided a choice between the pH treatment waters and allowed us to measure the amount of time individuals spent on either side of the arena in 300-s trials. There was no effect of prior diet or pH exposure on the amount of time juvenile crab spent in either seawater pH condition. In addition to the behavior trials, we evaluated crab nutritional condition by quantifying the total lipid content of whole-body tissues and fatty acid profile composition of juvenile crab fed either the maintenance or low-quantity diet during the experimental pH exposure period. The proportional fatty acid profiles differed for crab based on their diet and pH exposure, with no interactive effects. However, we did not detect differences in the concentrations of key summary categories of fatty acids (e.g., saturated, monounsaturated, or polyunsaturated) based on pH exposure. Our results indicate that reduced food availability has a greater impact on juvenile Dungeness crab foraging behavior and nutritional condition than reduced seawater pH exposure representing the 0.3 pH unit decrease predicted by 2100.

Continue reading ‘Juvenile Dungeness crab foraging behavior and lipid composition is altered more by food quantity than seawater pH in a multi-stressor experiment’

Climate change effects on marine species across trophic levels

Published 10 March 2023 Science Closed
Tags: , , , , , , , , , , ,

Climate change and anthropogenic activities are producing a range of new selection pressures, both abiotic and biotic, on marine organisms. While there are numerous studies that have investigated the response of individual marine organisms to climate change, few studies have focused on differences in organismal responses across trophic levels. Such trophic differences in response to climate change may disrupt ecological interactions and thereby threaten marine ecosystem function. In addition, predation is known as a strong driver that impacts individuals and populations. Despite this, we still do not have a comprehensive understanding of how different trophic levels respond to climate change stressors, predation and their combined effects in marine ecosystems.

The main focus of this thesis is to identify whether marine trophic levels respond differently to climatic stressors and predation. To explore these questions, I have used a combination of traditional mesocosm experiments, together with a statistical method called meta-analysis. I initiated the research by study the responses of marine gastropods at two trophic levels to ocean acidification and predation using long-term mesocosm experiments together with a gastropod-specific meta-analyses. I focused on the amount of phenotypic plasticity in morphological traits of snails when exposed to the two stressors. In order to generalise and test these assumptions among a greater number of marine taxa, I used the meta-analysis approach to investigate the effects of ocean acidification and warming, as well as their combined effects on four marine trophic levels. Finally, to study the individual and combined effects of ocean acidification and predation with respect to inducible defences, I again applied a mesocosm experiment and used blue mussels as a model species.

By using long-term mesocosm experiments and the gastropod-specific meta-analysis on marine gastropods from two trophic levels, I showed that these trophic levels varied in their responses to both ocean acidification and predation. Gastropods at lower trophic levels exhibited greater phenotypic plasticity against predation, while those from higher trophic levels showed stronger tolerance to ocean acidification. Next, by using a meta-analysis, including a large number of species and taxa, examining the effects of ocean acidification and warming, I revealed that top-predators and primary producers were most tolerant to ocean acidification compared to other trophic levels. Herbivores on the other hand, were the most vulnerable trophic level against abiotic stress. Again, using the meta-analysis approach, but this time incorporating only factorial experimental data that included the interactive effects of ocean acidification and ocean warming, I showed that higher trophic levels again were the most tolerant trophic level, and herbivores being most sensitive, with respect to the combined effect of the two stressors. Contrary to previous discussions in the literature concerning multiple climate-related stressors, antagonistic and additive effects occurred most frequently, while synergistic effects were less common and which decreased with increasing trophic rank. Finally, by conducting a fully-factorial experiment using blue mussels, I found that mussels with previous experience contact with predator has developed greater inducible defences than ones without previous experience. However, levels of ocean acidification may mask predator cues, or obstruct shell material, and consequently disrupt blue mussels inducible defence from crab predation.

In summary, marine trophic levels respond differently to both biotic and climatic stressors. Higher trophic levels, together with primary producers, were often more robust against abiotic stress and may therefore be better prepared for future oceans compare species from lower trophic levels. These results may provide vital information for: implementing effective climate change mitigation, to understand which stressors to act on, and when and where to intervene for prioritizing conservation actions.

Continue reading ‘Climate change effects on marine species across trophic levels’

Predicting effects of multiple interacting global change drivers across trophic levels

Published 8 March 2023 Science Closed
Tags: , , , , , , , , , , ,

Global change encompasses many co-occurring anthropogenic drivers, which can act synergistically or antagonistically on ecological systems. Predicting how different global change drivers simultaneously contribute to observed biodiversity change is a key challenge for ecology and conservation. However, we lack the mechanistic understanding of how multiple global change drivers influence the vital rates of multiple interacting species. We propose that reaction norms, the relationships between a driver and vital rates like growth, mortality, and consumption, provide insights to the underlying mechanisms of community responses to multiple drivers. Understanding how multiple drivers interact to affect demographic rates using a reaction-norm perspective can improve our ability to make predictions of interactions at higher levels of organization—that is, community and food web. Building on the framework of consumer–resource interactions and widely studied thermal performance curves, we illustrate how joint driver impacts can be scaled up from the population to the community level. A simple proof-of-concept model demonstrates how reaction norms of vital rates predict the prevalence of driver interactions at the community level. A literature search suggests that our proposed approach is not yet used in multiple driver research. We outline how realistic response surfaces (i.e., multidimensional reaction norms) can be inferred by parametric and nonparametric approaches. Response surfaces have the potential to strengthen our understanding of how multiple drivers affect communities as well as improve our ability to predict when interactive effects emerge, two of the major challenges of ecology today.

Continue reading ‘Predicting effects of multiple interacting global change drivers across trophic levels’

Dynamics of an aquatic diffusive predator–prey model with double Allee effect and pH-dependent capture rate

Published 2 March 2023 Science Closed
Tags: , , , ,

To investigate ocean acidification and Allee effects on the dynamics of a marine predator–prey system, an aquatic diffusive predator–prey model with double Allee effect on prey and pH-dependent capture rate is considered. First, we study the stability of constant steady state solutions using linearized theory. Second, the nonexistence of nonconstant positive steady state solutions is shown for appropriate ranges of parameters. Furthermore, we show the existence of a Hopf bifurcation and derive the direction and stability of the bifurcating periodic solutions. Both theoretical analysis and numerical simulation show that changing predator–prey interaction strengths, due to changing environmental conditions, can fundamentally change the system dynamics, even for apparently small changes in interaction strength. As the interaction strength decreases due to decreasing ocean pH, the system dynamics transition from persistent fluctuations in species abundances (periodic solutions), to stable coexistence, to predator extinct (with stable non-zero prey abundance), suggesting the potential for ocean acidification to decrease the abundance and diversity of marine species by weakening predation rates. Moreover, double Allee effect parameters together determine the stability of periodic solutions when the spatially homogeneous bifurcating periodic solutions exist, and the wavelength becomes longer as the Allee effect increases.

Continue reading ‘Dynamics of an aquatic diffusive predator–prey model with double Allee effect and pH-dependent capture rate’

Differential effects of ocean acidification and warming on biological functioning of a predator and prey species may alter future trophic interactions

Published 23 February 2023 Science Closed
Tags: , , , , , , , , ,

Highlights

  • Multiple environmental stressors act upon multiple trophic levels.
  • Mollusc predator and prey respond differently to future climate scenarios.
  • Prey are negatively impacted physiologically and behaviourally.
  • Predators unaffected resulting in elevated predation risk for prey.
  • Potential for fundamental change in trophic interactions affecting biodiversity.

Abstract

Independently, ocean warming (OW) and acidification (OA) from increased anthropogenic atmospheric carbon dioxide are argued to be two of the greatest threats to marine organisms. Increasingly, their interaction (ocean acidification and warming, OAW) is shown to have wide-ranging consequences to biological functioning, population and community structure, species interactions and ecosystem service provision. Here, using a multi-trophic experiment, we tested the effects of future OAW scenarios on two widespread intertidal species, the blue mussel Mytilus edulis and its predator Nucella lapillus. Results indicate negative consequences of OAW on the growth, feeding and metabolic rate of M. edulis and heightened predation risk. In contrast, Nucella growth and metabolism was unaffected and feeding increased under OAW but declined under OW suggesting OA may offset warming consequences. Should this differential response between the two species to OAW, and specifically greater physiological costs to the prey than its predator come to fruition in the nature, fundamental change in ecosystem structure and functioning could be expected as trophic interactions become disrupted.

Continue reading ‘Differential effects of ocean acidification and warming on biological functioning of a predator and prey species may alter future trophic interactions’

Combined effects of climate change stressors and predators with contrasting feeding-digestion strategies on a mussel species

Published 1 February 2023 Science Closed
Tags: , , , , , , , ,
Graphical abstract

Highlights

  • Combined effects of climate change stressors and Predator Cues (PC) were evaluated.
  • Ocean Acidification (OA), Warming (OW) and PC affected mussel traits.
  • At the control temperature (15 °C), mussel byssal biogenesis increased with PC.
  • PC affected mussel size, wet mass and calcification rate.
  • The effects of starfish PC on some mussel traits were larger than those of snail PC.

Abstract

We investigated the combined effects of Ocean Warming (OW), Acidification (OA) and predator cues (Non-Consumptive Effects; NCEs) of two predators with contrasting feeding-digestion strategies on the mussel Perumytilus purpuratus. We considered starfish-NCEs (partially external digestion) and snail-NCEs (internal digestion). Mussels were exposed for 13 weeks to cross-factored OA (~500 and ~1400 μatm, pCO2) and OW (~15 and ~20 °C) conditions, in the presence/absence of NCEs from one or both predators. Mussels exposed to both NCEs exhibited smaller length and buoyant weight growth than those under control or snail-NCEs conditions. Mussels exposed to starfish-NCEs exhibited smaller wet mass than control mussels. OW and starfish-NCEs in isolation or combined with snail-NCEs increased mussel oxygen consumption. Byssal biogenesis was affected by the three-factors interaction. Clearance rates were affected by the OW × OA interaction. We suggest that mainly starfish-NCEs, in isolation or interacting with OA or/and OW, can threat mussel traits and the associated community.

Continue reading ‘Combined effects of climate change stressors and predators with contrasting feeding-digestion strategies on a mussel species’

Biological responses of the predatory blue crab and its hard clam prey to ocean acidification and low salinity

Published 9 December 2022 Science Closed
Tags: , , , , , , , , , , , ,

How ocean acidification (OA) interacts with other stressors is understudied, particularly for predators and prey. We assessed long-term exposure to decreased pH and low salinity on (1) juvenile blue crab Callinectes sapidus claw pinch force, (2) juvenile hard clam Mercenaria mercenaria survival, growth, and shell structure, and (3) blue crab and hard clam interactions in filmed mesocosm trials. In 2018 and 2019, we held crabs and clams from the Chesapeake Bay, USA, in crossed pH (low: 7.0, high: 8.0) and salinity (low: 15, high: 30) treatments for 11 and 10 wk, respectively. Afterwards, we assessed crab claw pinch force and clam survival, growth, shell structure, and ridge rugosity. Claw pinch force increased with size in both years but weakened in low pH. Clam growth was negative, indicative of shell dissolution, in low pH in both years compared to the control. Growth was also negative in the 2019 high-pH/low-salinity treatment. Clam survival in both years was lowest in the low-pH/low-salinity treatment and highest in the high-pH/high-salinity treatment. Shell damage and ridge rugosity (indicative of deterioration) were intensified under low pH and negatively correlated with clam survival. Overall, clams were more severely affected by both stressors than crabs. In the filmed predator-prey interactions, pH did not substantially alter crab behavior, but crabs spent more time eating and burying in high-salinity treatments and more time moving in low-salinity treatments. Given the complex effects of pH and salinity on blue crabs and hard clams, projections about climate change on predator-prey interactions will be difficult and must consider multiple stressors.

Continue reading ‘Biological responses of the predatory blue crab and its hard clam prey to ocean acidification and low salinity’

Cascading effects augment the direct impact of CO2 on phytoplankton growth in a biogeochemical model

Published 11 November 2022 Science Closed
Tags: , , , , , , , , , , , , ,

Atmospheric and oceanic CO2 concentrations are rising at an unprecedented rate. Laboratory studies indicate a positive effect of rising CO2 on phytoplankton growth until an optimum is reached, after which the negative impact of accompanying acidification dominates. Here, we implemented carbonate system sensitivities of phytoplankton growth into our global biogeochemical model FESOM-REcoM and accounted explicitly for coccolithophores as the group most sensitive to CO2. In idealized simulations in which solely the atmospheric CO2 mixing ratio was modified, changes in competitive fitness and biomass are not only caused by the direct effects of CO2, but also by indirect effects via nutrient and light limitation as well as grazing. These cascading effects can both amplify or dampen phytoplankton responses to changing ocean pCO2 levels. For example, coccolithophore growth is negatively affected both directly by future pCO2 and indirectly by changes in light limitation, but these effects are compensated by a weakened nutrient limitation resulting from the decrease in small-phytoplankton biomass. In the Southern Ocean, future pCO2 decreases small-phytoplankton biomass and hereby the preferred prey of zooplankton, which reduces the grazing pressure on diatoms and allows them to proliferate more strongly. In simulations that encompass CO2-driven warming and acidification, our model reveals that recent observed changes in North Atlantic coccolithophore biomass are driven primarily by warming and not by CO2. Our results highlight that CO2 can change the effects of other environmental drivers on phytoplankton growth, and that cascading effects may play an important role in projections of future net primary production.

Continue reading ‘Cascading effects augment the direct impact of CO2 on phytoplankton growth in a biogeochemical model’

Coral reef fishes in a multi-stressor world

Published 1 November 2022 Science Closed
Tags: , , , , , , , , , , ,

Coral reef fishes and the ecosystems they support represent some of the most biodiverse and productive ecosystems on the planet yet are under threat as they face dramatic increases in multiple, interacting stressors that are largely intensified by anthropogenic influences, such as climate change. Coral reef fishes have been the topic of 875 studies between 1979 and 2020 examining physiological responses to various abiotic and biotic stressors. Here, we highlight the current state of knowledge regarding coral reef fishes’ responses to eight key abiotic stressors (i.e., pollutants, temperature, hypoxia and ocean deoxygenation, pH/CO2, noise, salinity, pressure/depth, and turbidity) and four key biotic stressors (i.e., prey abundance, predator threats, parasites, and disease) and discuss stressors that have been examined in combination. We conclude with a horizon scan to discuss acclimation and adaptation, technological advances, knowledge gaps, and the future of physiological research on coral reef fishes. As we proceed through this new epoch, the Anthropocene, it is critical that the scientific and general communities work to recognize the issues that various habitats and ecosystems, such as coral reefs and the fishes that depend on and support them, are facing so that mitigation strategies can be implemented to protect biodiversity and ecosystem health.

Continue reading ‘Coral reef fishes in a multi-stressor world’

Limited behavioural effects of ocean acidification on a Mediterranean anemone goby (Gobius incognitus) chronically exposed to elevated CO2 levels

Published 7 October 2022 Science Closed
Tags: , , , , , , ,
Graphical abstract

Highlights

  • This is the first assessment in the wild of behavioural responses of fish acutely and chronically exposed to elevated CO2.
  • High density of anemone goby fish was recorded at high-CO2 levels off a volcanic CO2 vent in Vulcano island (Italy).
  • Acute and chronic exposure to elevated CO2 did not affect most of the behaviours in adult G. incognitus.
  • Behavioural plasticity occurred under ocean acidification conditions suggesting potential local adaptation.

Abstract

An in situ reciprocal transplant experiment was carried around a volcanic CO2 vent to evaluate the anti-predator responses of an anemone goby species exposed to ambient (∼380 μatm) and high (∼850 μatm) CO2 sites. Overall, the anemone gobies displayed largely unaffected behaviors under high-CO2 conditions suggesting an adaptive potential of Gobius incognitus to ocean acidification (OA) conditions. This is also supported by its 3-fold higher density recorded in the field under high CO2. However, while fish exposed to ambient conditions showed an expected reduction in the swimming activity in the proximity of the predator between the pre- and post-exposure period, no such changes were detected in any of the other treatments where fish experienced acute and long-term high CO2. This may suggest an OA effect on the goby antipredator strategy. Our findings contribute to the ongoing debate over the need for realistic predictions of the impacts of expected increased CO2 concentration on fish, providing evidence from a natural high CO2 system.

Continue reading ‘Limited behavioural effects of ocean acidification on a Mediterranean anemone goby (Gobius incognitus) chronically exposed to elevated CO2 levels’

Variation in the behavioral tolerance of congeneric marine snails to low-pH exposure

Published 5 October 2022 Science Closed
Tags: , , , ,

The ocean is acidifying, with multiple consequences for coastal organisms. However, species may differ in their sensitivities. Some taxa may find future conditions mildly stressful or even advantageous, while others will persist only through acclimatization or genetic adaptation. An open question is whether such variation in the sensitivity of species to ocean acidification relates to their evolutionary histories of exposure to reduced pH. Here, we explored this unknown through an investigation of differences in pH tolerance of 2 shoreline gastropods, the black turban snail Tegula funebralis and its congener, the brown turban snail T. brunnea. These species occupy distinct vertical distributions on rocky shores, each subject to different extremes in low pH. We assayed the extent to which low pH degrades the flight behavior of each species in response to the predatory sea star Pisaster ochraceus. Across a range of pH, the tidepool-inhabiting T. funebralis exhibited less behavioral disruption than T. brunnea at any given pH value but also experienced impairment at a pH characteristic of the present-day minimum in its habitat (7.1 pH). The latter pattern suggests T. funebralis operates near what may be a fixed tolerance limit to low pH. T. funebralis also exhibited hints of elevated intraspecific variation in its behaviors, which could imply scope for selection to act. Deeper-dwelling T. brunnea, in contrast, showed little sensitivity to present-day pH minima found where it lives (7.6 pH) and displayed less variation upon which selection might operate. These results provide a initial framework for investigations into the capacity of species of differing evolutionary histories to cope with future ocean acidification.

Continue reading ‘Variation in the behavioral tolerance of congeneric marine snails to low-pH exposure’

Bioaccumulation of inorganic and organic mercury in the cuttlefish Sepia officinalis: influence of ocean acidification and food type

Published 7 September 2022 Science Closed
Tags: , , , , , , , ,

The bioaccumulation of mercury (Hg) in marine organisms through various pathways has not yet been fully explored, particularly in cephalopods. This study utilises radiotracer techniques using the isotope 203Hg to investigate the toxicokinetics and the organotropism of waterborne inorganic Hg (iHg) and dietary inorganic and organic Hg (methylHg, MeHg) in juvenile common cuttlefish Sepia officinalis. The effect of two contrasting CO2 partial pressures in seawater (400 and 1600 μatm, equivalent to pH 8.08 and 7.54 respectively) and two types of prey (fish and shrimp) were tested as potential driving factors of Hg bioaccumulation. After 14 days of waterborne exposure, juvenile cuttlefish showed a stable concentration factor of 709 ± 54 and 893 ± 117 at pH 8.08 and 7.54, respectively. The accumulated dissolved i203Hg was depurated relatively rapidly with a radiotracer biological half-life (Tb1/2) of 44 ± 12 and 55 ± 16 days at pH 8.08 and 7.54, respectively. During the whole exposure period, approximately half of the i203Hg was found in the gills, but i203Hg also increased in the digestive gland. When fed with 203Hg-radiolabelled prey, cuttlefish assimilated almost all the Hg provided (>95%) independently of the prey type. Nevertheless, the prey type played a major role on the depuration kinetics with Hg Tb1/2 approaching infinity in fish fed cuttlefish vs. 25 days in shrimp fed cuttlefish. Such a difference is explained by the different proportion of Hg species in the prey, with fish prey containing more than 80% of MeHg vs. only 30% in shrimp. Four days after ingestion of radiolabelled food, iHg was primarily found in the digestive organs while MeHg was transferred towards the muscular tissues. No significant effect of pH/pCO2 variation was observed during both the waterborne and dietary exposures on the bioaccumulation kinetics and tissue distribution of i203Hg and Me203Hg. Dietary exposure is the predominant pathway of Hg bioaccumulation in juvenile cuttlefish.

Continue reading ‘Bioaccumulation of inorganic and organic mercury in the cuttlefish Sepia officinalis: influence of ocean acidification and food type’

Differential effects of warming and acidification on chemosensory transmission and detection may strengthen non-consumptive effects of blue crab predators (Callinectes sapidus) on mud crab prey (Panopeus herbstii)

Published 25 August 2022 Science Closed
Tags: , , , , , , ,

Predators control prey abundance and behavior, both of which strongly influence community dynamics. However, the relative importance of these predator effects may shift with climate change stressors, suggesting understanding the potential effects on these different processes is critical to predicting effects of climate change on community function. We investigated the effects of global warming and ocean acidification on the transmission and detection of chemical cues from blue crab predators (Callinectes sapidus) by mud crab prey (Panopeus herbstii). We measured mud crab feeding rates in the presence of blue crab predator cues, using either predator cues stressed in acidified conditions or mud crabs stressed in warmed and acidified conditions. Mud crabs consumed less food in the presence of predator cues, but acidifying the cues or subjecting mud crabs receiving the cues to acidified environment did not affect this antipredator response. Mud crabs in warmed conditions consumed significantly less food regardless of predator cue, but this effect was reversed in ambient conditions. Therefore, climate change may produce shifts in community regulation as warming potentially compromises consumptive effects of predators by reducing motor function, whereas non-consumptive effects mediated by sensory transmission and detection remain unaffected by acidification. Overall, warming may have stronger effects than acidification on community dynamics in oyster reefs as global temperatures continue to rise.

Continue reading ‘Differential effects of warming and acidification on chemosensory transmission and detection may strengthen non-consumptive effects of blue crab predators (Callinectes sapidus) on mud crab prey (Panopeus herbstii)’

Context-dependent effects of ocean acidification on the interaction between a crab predator and its oyster prey

Published 2 August 2022 Science Closed
Tags: , , , , , , , ,

Ocean acidification affects the fitness of species in coastal and estuarine systems, although interactions among species may alleviate or elevate the responses. Acidification effects on predator-prey interactions were evaluated between the blue crab Callinectes sapidus and eastern oyster Crassostrea virginica. Animals were exposed to 5 pH treatments: (1) control (pH ~8.00), constant pH at (2) 7.10 and (3) 6.75, and cycling pH from (4) 7.10 and (5) 6.75 to ~8.00, respectively. Crab foraging behavior, oyster size, and their defensive response against crabs (i.e. shell thickening) were compared among pH treatments. Results showed that predation rates of crabs tended to decrease with pH and from cycling to constant conditions, though statistical differences were only found at the lowest pH value and when consuming the larger oysters offered. Also, crab interest in oysters decreased with decreasing pH. In contrast, prey handling times and foraging motivation triggered by an odor stimulus were not affected by pH. In oysters, size metrics decreased with pH and also from cycling to constant conditions. Additionally, shells were thicker in the presence of predators, although the defensive strategy of oysters was weakened at the lowest pH level examined. Results indicate that although impaired foraging behavior of blue crabs may compensate for the negative effects on oysters under extreme acidification conditions, net effects are difficult to predict depending on the conditions to which animals are exposed and the size and behavioral variables considered.

Continue reading ‘Context-dependent effects of ocean acidification on the interaction between a crab predator and its oyster prey’

The effect of ocean acidification on the escape behaviour of the sea star Parvulastra exigua to its sea star predator Meridiastra calcar

Published 15 July 2022 Science Closed
Tags: , , , , , , ,

Ocean acidification (OA) driven by sea water uptake of anthropogenic atmospheric CO2 has broad deleterious effects on marine species including modified behavioural interactions such as between predators and prey. Predatory sea stars are key species in many marine ecosystems and often elicit defensive responses in their prey. This study investigated the effect of elevated CO2 on the escape response of the sea star Parvulastra exigua to its sea star predator Meridiastra calcar. In response to touch by M. calcar, P. exigua exhibits a distinct fleeing response. The escape response of P. exigua with respect to velocity and escape trajectory was investigated after both species were acclimated in OA conditions. At pHT 7.6 and 7.8 velocity and escape trajectory of the fleeing response of P. exigua did not differ from that seen in the ambient treatment. However, there was a delay in the time that P. exigua started to flee with the initiation time being 2.8 times slower (10 vs 28 s) at pHT 7.6. This delay may increase the vulnerability of P. exigua to predation by M. calcar and have ecological effects with respect to the role of this species as an algal grazer on rocky shores of southeast Australia where these sea star species co-occur.

Continue reading ‘The effect of ocean acidification on the escape behaviour of the sea star Parvulastra exigua to its sea star predator Meridiastra calcar’

Marine gastropods at higher trophic level show stronger tolerance to ocean acidification

Published 8 July 2022 Science Closed
Tags: , , , , , , , ,

Climate change and anthropogenic activities are producing a range of new selection pressures, both abiotic and biotic, on marine organisms. Although it is known that climate change can differentially affect fitness-related traits at different trophic levels of the food web, it is not clear if different trophic levels will respond via phenotypic plasticity in the form of maintenance of phenotypes in the face of abiotic and biotic environmental stress similarly. To answer this question, we combined a mesocosm experiment (120 days) using a food web comprising three gastropod species from two trophic levels (grazers and meso-predators) and a meta-analysis including 38 studies to address whether different trophic levels exhibit similar phenotypic responses to abiotic and biotic variables. Abiotic (ocean acidification) and biotic (predation) stress significantly influenced body mass, shell mass, shell thickness and shell strength in both grazers and meso-predators in the mesocosm experiment, with the magnitude of OA effects greater on the meso-predator than the grazers; a result supported by the meta-analysis. In contrast, both mesocosm experiment and meta-analysis found that predation risk induced stronger responses in shell morphology for grazers compared to meso-predators. Together, our findings indicate that higher trophic level species are better able to maintain aspects of their phenotype under OA, suggesting that they may show greater tolerance to climate change effects in general, while lower trophic levels express higher levels of plastic inducible defences to maintain function when under threat of predation. By using marine snails as a model, our study provides new knowledge for understanding how changing environmental conditions may alter biological interactions, and increases our understanding of how climate change may affect ecological communities in which gastropods play a key role.

Continue reading ‘Marine gastropods at higher trophic level show stronger tolerance to ocean acidification’
  • Reset

Subscribe

OA-ICC Highlights

%d bloggers like this: