Measures of ecosystem structure and function derived from analysis of flows†
Several measures of ecosystem structure and function are derived from the application of economic input-output analysis to ecosystem compartment models. Total system throughflow (TST) is defined as the sum of all compartmental throughflows. Average path length of the ith inflow (APL1) is defined as the average number of compartments through which the ith inflow passes. Average path length for an average inflow (ĀPL) is the mean of APL1 weighted according to size of the inflows. ĀPL is shown to be equal to TST divided by the sum of all inflows. TST can be partitioned into a portion due to cycled flow (TSTo) and a portion due to flow straight through the system (straight throughflow, TSTs). The portion of ĀPL due to cycled flow divided by the portion due to straight throughflow is the cycling index (CI). This index indicates how many times further than the straight throughflow path length an average system inflow will travel because of cycling. Three simple ecosystem models are examined to demonstrate the utility of these measures in explaining ecological phenomena.
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Cited by (668)
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Global change alters coastal plankton food webs by promoting the microbial loop: An inverse modelling and network analysis approach on a mesocosm experiment
2024, Science of the Total EnvironmentMarine organisms are currently, and will continue to be, exposed to the simultaneous effects of multiple environmental changes. Plankton organisms form the base of pelagic marine food webs and are particularly sensitive to ecosystem changes. Thus, warming, acidification, and changes in dissolved nutrient concentrations have the potential to alter these assemblages, with consequences for the entire ecosystem. Despite the growing number of studies addressing the potential influence of multiple drivers on plankton, global change may also cause less obvious alterations to the networks of interactions among species. Using inverse analyses applied to data collected during a mesocosm experiment, we aimed to compare the ecological functioning of coastal plankton assemblages and the interactions within their food web under different global change scenarios. The experimental treatments were based on the RCP 6.0 and 8.5 scenarios developed by the IPCC, which were extended (ERCP) to integrate the future predicted changes in coastal water nutrient concentrations. Overall, we identified that the functioning of the plankton food web was rather similar in the Ambient and ERCP 6.0 scenarios, but substantially altered in the ERCP 8.5 scenario. Using food web modelling and ecological network analysis, we identified that global change strengthens the microbial loop, with a decrease of energy transfer efficiency to higher trophic levels. Microzooplankton responded as well by an increased degree of herbivory in their diet and represented, compared to mesozooplankton, by far the main top-down pressure on primary producers. We also observed that the organisation of the food web and its capacity to recycle carbon was higher under the ERCP 8.5 scenario, but flow diversity and carbon path length were significantly reduced, illustrating an increased food web stability at the expense of diversity. Here, we provide evidence that if global change goes beyond the ERCP 6.0 scenario, coastal ecosystem functioning will be subjected to dramatic changes.
Temporal and spatial differences in nitrogen and phosphorus biogeochemistry and ecosystem functioning of a hypertrophic lagoon (Curonian Lagoon, SE Baltic Sea) revealed via Ecological Network Analysis
2024, Science of the Total EnvironmentIn coastal lagoons, eutrophication and hydrology are interacting factors that produce distortions in biogeochemical nitrogen (N) and phosphorus (P) cycles. Such distortions affect nutrient relative availability and produce cascade consequences on primary producer's community and ecosystem functioning.
In this study, the seasonal functioning of a coastal lagoon was investigated with a multielement approach, via the construction and analysis of network models. Spring and summer networks, both for N and P flows, have been simultaneously compiled for the northern transitional and southern confined area of the hypertrophic Curonian Lagoon (SE Baltic Sea). Ecological Network Analysis was applied to address the combined effect of hydrology and seasonality on biogeochemical processes.
Results suggest that the ecosystem is more active and presents higher N and P fluxes in summer compared to spring, regardless of the area. Furthermore, larger internal recycling characterizes the confined compared to the transitional area, regardless of the season. The two areas differed in the fate of available nutrients. The transitional area received large riverine inputs that were mainly transferred to the sea without the conversion into primary producers' biomass. The confined area had fewer inputs but proportionally larger conversion into phytoplankton biomass. In summer, particularly in the confined area, primary production was inefficiently consumed by herbivores. Most phytoplanktonic N and P, in the confined area more than in the transitional area, were conveyed to the detritus pathway where P, more than N, was recycled, contributing to the unbalance in N:P stoichiometry and favouring N-fixing cyanobacteria over other phytoplankton groups. The findings of this study provide a comprehensive understanding of N and P circulation patterns in lagoon areas characterized by different hydrology. They also support the importance of a stoichiometric approach to trace relative differences in N and P recycling and abundance, that promote blooms, drive algal communities and whole ecosystem functioning.
Analysis of the dynamics of common industrial solid waste based on input–output: A case study of Shanghai international metropolis in China
2024, Waste ManagementRapid economic development inevitably leads to the discharge of a large amount of common industrial solid waste (CISW), which not only pollutes the environment but also restricts economic development in turn. In this study, a dynamic common industrial solid waste (DCISW) model is developed to analyze the retrospectively CISW development in Shanghai from 2000 to 2017 and simulate prospectively multi-perspective emission reduction measures. Specifically, the dynamic linkages between CISW and socio-economics are established at both the systematic and sectoral levels through input–output analysis, ecological network analysis, and related socio-economic indicators. Abatement measure simulations are conducted using RAS and other methods. The findings reveal that the growth of CISW in Shanghai is closely related to its fast-growing economy. The Others sector (OS) receives the most CISW from other sectors, while the Mining industry (MI) sends the most CISW to others. From production-based, consumption-based, and income-based perspectives, Chemical Products (CP) consistently remain the largest contributors. For the proposed waste generation intensity (WGI) indicator, the Mining industry (MI) is regarded as the main sector in all three perspectives. Moreover, the MI consistently emerges as the key sector of the system. CISW simulations indicate that improving the MI emission technology and increasing the MI output value will be top priorities for CISW emission reduction in Shanghai. This study is expected to provide scientific support to address the CISW problem in Shanghai and other similar fast-growing metropolises.
Exploring nonlinear responses of lake nutrients and algal blooms to restoration measures: A three-dimensional flux network modelling approach
2024, Journal of HydrologyExcessive anthropogenic nitrogen (N) and phosphorus (P) inputs accelerate harmful algal blooms (HABs) and pose a significant global threat to lake ecosystems. Despite the adoption of extensive restoration measures to improve water quality, their effects on nutrient cycles and the underlying pathways remain unclear. In this study, a three-dimensional nutrient flux modelling approach was developed based on a validated Environmental Fluid Dynamics Code (EFDC) model and the Spatiotemporal Integral for Nutrient Networks (SINN) to compute nutrient storages and fluxes in lakes. We then conducted a scenario analysis, composed of 10 schemes, to assess the eight restoration measures in Lake Dianchi, China. The results showed that our model exhibited a high level of agreement with observed data and fluxes reported in previous studies. Of all the measures implemented, pollution interception by lakeshore wastewater treatment plants (WWTPs) accounted for the largest historical improvements in water quality, with reductions of total nitrogen (TN) by 9.3%, total phosphorus (TP) by 36.4%, and chlorophyll a (Chla) by 18.2%. Furthermore, combined implementation of transboundary water transfer and wastewater diversion contributed to a reduction of 13.3% in TN, 11.5% in TP, and 6.2% in Chla. To achieve greater improvements in water quality, efforts must be made to improve the emission standard of WWTPs and ensure compliance with water quality standard of inflow rivers. The cyanobacteria biomass catch can only be used as a supplementary approach to restrict the HAB peaks. The nonlinear responses of lakes were characterized by large loading abatement but slight changes in water quality. Through the SINN approach, we revealed that weakened internal cycling was the primary driver of water quality improvements in all restoration measures. Further analysis demonstrated that measures targeting reducing external loadings significantly weakened internal cycling processes. In contrast, measures targeting the internal loadings, such as sediment dredging, exhibited limited effectiveness in reducing the intensity of internal cycling and Chla in the lake. For eutrophic lakes with substantial legacy nutrients, the abatement of external loadings remains the principal strategy. The approach presented in this study can be used to assess and optimize lake restoration measures.
Using a food web model to predict the effects of Hazardous and Noxious Substances (HNS) accidental spills on deep-sea hydrothermal vents from the Mid-Atlantic Ridge (MAR) region
2024, Marine Pollution BulletinDeep-sea hydrothermal vents host unique ecosystems but face risks of incidents with Hazardous and Noxious Substances (HNS) along busy shipping lanes such as the transatlantic route. We developed an Ecopath with Ecosim (EwE) model of the Menez Gwen (MG) vent field (MG-EwE) (Mid-Atlantic Ridge) to simulate ecosystem effects of potential accidental spills of four different HNS, using a semi-Lagrangian Dispersion Model (sLDM) coupled with the Regional Ocean Modelling System (ROMS) calibrated for the study area. Food web modelling revealed a simplified trophic structure with low energy efficiency. The MG ecosystem was vulnerable to disruptions caused by all tested HNS, yet it revealed some long-term resilience. Understanding these impacts is vital for enhancing Spill Prevention, Control, and Countermeasure plans (SPCC) in remote marine areas and developing tools to assess stressors effects on these invaluable habitats.
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University of Georgia, Contributions in Systems Ecology, No. 23.