Posts Tagged 'communitymodeling'

Impacts of the changing ocean-sea ice system on the key forage fish Arctic cod (Boreogadus saida) and subsistence fisheries in the Western Canadian Arctic—evaluating linked Climate, Ecosystem and Economic (CEE) models

This study synthesizes results from observations, laboratory experiments and models to showcase how the integration of scientific methods and indigenous knowledge can improve our understanding of (a) past and projected changes in environmental conditions and marine species; (b) their effects on social and ecological systems in the respective communities; and (c) support management and planning tools for climate change adaptation and mitigation. The study links climate-ecosystem-economic (CEE) models and discusses uncertainties within those tools. The example focuses on the key forage species in the Inuvialuit Settlement Region (Western Canadian Arctic), i.e., Arctic cod (Boreogadus saida). Arctic cod can be trophically linked to sea-ice algae and pelagic primary producers and are key vectors for energy transfers from plankton to higher trophic levels (e.g., ringed seals, beluga), which are harvested by Inuit peoples. Fundamental changes in ice and ocean conditions in the region affect the marine ecosystem and fish habitat. Model simulations suggest increasing trends in oceanic phytoplankton and sea-ice algae with high interannual variability. The latter might be linked to interannual variations in Arctic cod abundance and mask trends in observations. CEE simulations incorporating physiological temperature limits data for the distribution of Arctic cod, result in an estimated 17% decrease in Arctic cod populations by the end of the century (high emission scenario), but suggest increases in abundance for other Arctic and sub-Arctic species. The Arctic cod decrease is largely caused by increased temperatures and constraints in northward migration, and could directly impact key subsistence species. Responses to acidification are still highly uncertain, but sensitivity simulations suggests an additional 1% decrease in Arctic cod populations due to pH impacts on growth and survival. Uncertainties remain with respect to detailed future changes, but general results are likely correct and in line with results from other approaches. To reduce uncertainties, higher resolution models with improved parameterizations and better understanding of the species’ physiological limits are required. Arctic communities should be directly involved, receive tools and training to conduct local, unified research and food chain monitoring while decisions regarding commercial fisheries will need to be precautionary and adaptive in light of the existing uncertainties.

Continue reading ‘Impacts of the changing ocean-sea ice system on the key forage fish Arctic cod (Boreogadus saida) and subsistence fisheries in the Western Canadian Arctic—evaluating linked Climate, Ecosystem and Economic (CEE) models’

Toxic algae silence physiological responses to multiple climate drivers in a tropical marine food chain

Research on the effects of climate change in the marine environment continues to accelerate, yet we know little about the effects of multiple climate drivers in more complex, ecologically relevant settings – especially in sub-tropical and tropical systems. In marine ecosystems, climate change (warming and freshening from land run-off) will increase water column stratification which is favorable for toxin producing dinoflagellates. This can increase the prevalence of toxic microalgal species, leading to bioaccumulation of toxins by filter feeders, such as bivalves, with resultant negative impacts on physiological performance. In this study we manipulated multiple climate drivers (warming, freshening, and acidification), and the availability of toxic microalgae, to determine their impact on the physiological health, and toxin load of the tropical filter-feeding clam, Meretrix meretrix. Using a structural equation modeling (SEM) approach, we found that exposure to projected marine climates resulted in direct negative effects on metabolic and immunological function and, that these effects were often more pronounced in clams exposed to multiple, rather than single climate drivers. Furthermore, our study showed that these physiological responses were modified by indirect effects mediated through the food chain. Specifically, we found that when bivalves were fed with a toxin-producing dinoflagellate (Alexandrium minutum) the physiological responses, and toxin load changed differently and in a non-predictable way compared to clams exposed to projected marine climates only. Specifically, oxygen consumption data revealed that these clams did not respond physiologically to climate warming or the combined effects of warming, freshening and acidification. Our results highlight the importance of quantifying both direct and, indirect food chain effects of climate drivers on a key tropical food species, and have important implications for shellfish production and food safety in tropical regions.

Continue reading ‘Toxic algae silence physiological responses to multiple climate drivers in a tropical marine food chain’

Direct and indirect impacts of marine acidification on the ecosystem services provided by coralligenous reefs and seagrass systems

Increasing emissions of CO2 and the resultant ocean acidification (OA) will have large implications for the marine ecosystems sustained by habitat-forming species and their related ecosystem services (ES), with potentially significant impacts on human well-being. Here, we provide an assessment of the direct and indirect impacts of OA on ES. The changes in the functioning of coralligenous reefs and Posidonia oceanica meadows promoted by OA were investigated by i) synthesizing current knowledge into conceptual models. The models were then used to, ii) assessing the impacts of exposure of the selected taxa at the acidification level associated with two CO2 emission scenarios and iii) using the conceptual model outputs to project the cascading impacts from individuals to functions to ES.

The results highlight that the combination of the direct and indirect effects of acidification will alter many functions of both coralligenous and P.oceanica systems, triggering habitat modifications and the loss of highly valuable ES.

While the exact timing of the expected changes will depend on the severity of the emission scenarios, significant and hardly reversible changes can be expected as quickly as a few decades under the business-as-usual scenario, and many ecosystem services are at risk even under much more conservative scenarios.

Continue reading ‘Direct and indirect impacts of marine acidification on the ecosystem services provided by coralligenous reefs and seagrass systems’

Highest plasticity of carbon‐concentrating mechanisms in earliest evolved phytoplankton

Phytoplankton photosynthesis strongly relies on the operation of carbon‐concentrating mechanisms (CCMs) to accumulate CO2 around their carboxylating enzyme ribulose‐1,5‐bisphosphate carboxylase/oxygenase (RuBisCO). Earlier evolved phytoplankton groups were shown to exhibit higher CCM activities to compensate for their RuBisCO with low CO2 specificities. Here, we tested whether earlier evolved phytoplankton groups also exhibit a higher CCM plasticity. To this end, we collected data from literature and applied a Bayesian linear meta‐analytic model. Our results show that with elevated pCO2, photosynthetic CO2 affinities decreased strongest and most consistent for the earlier evolved groups, i.e., cyanobacteria and dinoflagellates, while CO2‐dependent changes in affinities for haptophytes and diatoms were smaller and less consistent. In addition, responses of maximum photosynthetic rates toward elevated pCO2 were generally small and inconsistent across species. Our results demonstrate that phytoplankton groups with an earlier origin possess a high CCM plasticity, whereas more recently evolved groups do not, which likely results from evolved differences in the CO2 specificity of RuBisCO.

Continue reading ‘Highest plasticity of carbon‐concentrating mechanisms in earliest evolved phytoplankton’

Modeling impact of varying pH due to carbondioxide on the dynamics of prey–predator species system

In this paper, we have considered a nonlinear mathematical model to investigate the effect of pH on prey–predator dynamics with Holling type II functional response. In the model, capture rate, handling time, growth rate and death rate are considered to be pH dependent. From the analysis of the model, it has been observed that as pH level goes below the normal tolerance limit of prey species then the equilibrium density of prey population decreases due to increase in capture rate and decrease in handling time by predator. Further, we have shown that as the growth rate of prey population decreases due to lowering of pH then the density of predator population also decreases and both the populations may tend to extinction if growth rate of prey population becomes negative due to lowering of pH on account of elevated carbondioxide concentration in the aquatic body. Moreover, it is noticed from the simulation that if the mortality of predator population increases because of decrease in pH level then the prey population gets advantage and in-turn their population increases.

Continue reading ‘Modeling impact of varying pH due to carbondioxide on the dynamics of prey–predator species system’

Individual and population level effects of ocean acidification on a predator−prey system with inducible defenses: bryozoan−nudibranch interactions in the Salish Sea

Ocean acidification (OA) from in creased oceanic CO2 concentrations imposes significant physiological stresses on many calcifying organisms. OA effects on individual organisms may be synergistically amplified or reduced by inter- and intraspecies interactions as they propagate up to population and community
levels, altering predictions by studies of calcifier responses in isolation. The calcifying colonial bryozoan Membranipora membranacea and the predatory nudibranch Corambe steinbergae comprise a trophic system strongly regulated by predator induced defensive responses and space limitation, presenting a unique system to investigate OA effects on these regulatory mechanisms at individual and population levels. We experimentally quantified OA effects across a range of pH from 7.0 to 7.9 on growth, calcification, senescence and predator-induced spine formation in Membranipora, with or without waterborne predator cue, and on zooid consumption rates in Corambe at Friday Harbor Laboratories, San Juan Island, WA. Membranipora exhibited maximum growth and calcification at moderately low pH (7.6), and continued spine formation in all pH treatments.
Spines reduced Corambe zooid consumption rates, with lower pH weakening this effect. Using a spatially explicit model of colony growth, where colony area
serves as a proxy for colony fitness, we assessed the population-level impacts of these experimentally determined individual-level effects in the context of
space limitation. The area-based fitness costs associated with defense measured at the individual level led to amplified effects predicted for the population level due to competition. Our coupled experimental and modeling results demonstrate the need to consider population-level processes when assessing ecological responses to stresses from changing environments.

Continue reading ‘Individual and population level effects of ocean acidification on a predator−prey system with inducible defenses: bryozoan−nudibranch interactions in the Salish Sea’

Modeling impact of varying pH due to carbondioxide on the dynamics of prey–predator species system

In this paper, we have considered a nonlinear mathematical model to investigate the effect of pH on prey–predator dynamics with Holling type II functional response. In the model, capture rate, handling time, growth rate and death rate are considered to be pH dependent. From the analysis of the model, it has been observed that as pH level goes below the normal tolerance limit of prey species then the equilibrium density of prey population decreases due to increase in capture rate and decrease in handling time by predator. Further, we have shown that as the growth rate of prey population decreases due to lowering of pH then the density of predator population also decreases and both the populations may tend to extinction if growth rate of prey population becomes negative due to lowering of pH on account of elevated carbondioxide concentration in the aquatic body. Moreover, it is noticed from the simulation that if the mortality of predator population increases because of decrease in pH level then the prey population gets advantage and in-turn their population increases.

Continue reading ‘Modeling impact of varying pH due to carbondioxide on the dynamics of prey–predator species system’


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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book