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The ecosystem effects of different management options can be predicted through models that simulate the ecosystem functioning under different management scenarios. Optimal management strategies are searched by simulating different management (and other, such as climate) scenarios and finding the management measures that produce desirable results. The desirability of results is often defined through the attainment of policy objectives such as good environmental/ecological status. However, this often does not account for societal consequences of the environmental status even though the consequences can be different for different stakeholder groups. In this work we introduce a method to evaluate management alternatives in the light of the experiential value of stakeholder groups, using a case study in the Baltic Sea. We use an Ecopath with Ecosim model to simulate the ecosystem responses to management and climate scenarios, and the results are judged based on objectives defined based on a stakeholder questionnaire on what aspects of the ecosystem they value or detest. The ecosystem responses and the stakeholder values are combined in a Bayesian decision support model to illustrate which management options bring the highest benefits to stakeholders, and whether different stakeholder groups benefit from different management choices. In the case study, the more moderate climate scenario and strict fisheries and nutrient loading management brought the highest benefits to all stakeholders. The method can be used to evaluate and compare the effects of different management alternatives to various stakeholder groups, if their preferences are known., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

A trophic model was constructed for the Poonthura Estuary, a small, anthropogenically impacted estuary along the south-western coast of India. An Ecopath with Ecosim based trophic modelling approach, based on observations made between 2016 and 2020, revealed that the Poonthura Estuary had a low total system throughput (3044.2 t km -2 year -1 ), low ascendancy (15%), high Finn's cycling index (17.9%), low primary production/total biomass (5.2 t km -2 year -1 ), high mean transfer efficiency (12.4%), and low eco-exergy (14,455.46 gm detritus equivalent m -2 ). These values indicated that the estuary is an immature, less organized, and unhealthy system. The evaluation of Ecological Network Analysis, and ecosystem health indices revealed that the ecological structure and functioning of the estuary are impaired to a large extent from multiple anthropogenic stressors. The Poonthura Estuary trophic model revealed the total primary production/respiration value as 0.46, indicative of the massive pollution that the system is subjected to, particularly from organic sources. Small benthic carnivores were the most important keystone groups recorded from the Poonthura Estuary, despite their low biomass. The comparison of ecological indices of Poonthura Estuary, with those recorded for other small estuaries from various geographical locations, suggested dissimilar trophic functioning and food web structures from estuaries with similar physical features. Our study is a pioneering step to reveal the ecosystem status and functioning of small, anthropogenically disturbed estuaries, besides offering theoretical and scientific basis for the management, supervision and restoration of the Poonthura Estuary as well as other small estuaries, around the world., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Although microplastics (MPs) in marine organisms have been widely studied, the toxicity of MPs in freshwaters and human health is still a global challenge. To fill this gap, we implemented an Ecopath and food web accumulation model to simulate the Tai Lake ecosystem, a region dependent on the tourism and seafood industries. Our results suggested the accumulation of MPs throughout the food web and ultimately reach organisms at high trophic levels, including human-being, who consume MPs through seafood. The adults were prone to consume more MPs than adolescents and children. Unlike clams, fish biota magnification factors indicated that MPs accumulation between specific predator-prey interactions is not expected. The abundance of MPs within clams reveals a potential risk of MPs entering the food web. To better understand the MPs transfer, we recommend paying greater attention to species-specific mechanisms and the resources they rely on., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Chalakudy River is renowned for its pristine waters and rich ichthyofaunal biodiversity. The downstream area of the river is confronting a series of risks, including pollution, saline water ingression, sand mining, illegal and intensified fishing practices, and invasion of exotic and alien species. A mass balanced ecosystem model was constructed for the downstream region of Chalakudy River (DCR) using Ecopath with Ecosim (EWE), incorporating 12 functional groups to delineate the food web and network flow indices for the period 2020 to 2021. The trophic level (TL) of the ecosystem network ranged from TL-1 (detritus) to TL-3.4 (birds). High fishing pressure is one possible cause for the high ecotrophic efficiency values as evidenced by the fish groups. Both the grazing food chain and detritus food chain (detritivory: herbivory ratio 0.94) contributed more or less equal to the energy transfer between TL. Network analysis of the model indicated a mean transfer efficiency of 12%, with shares from primary producers (14%) and detritus (11%). A mixed trophic impact analysis demonstrated a strong positive impact of primary producers and detritus groups on most of the other ecological groups at higher trophic levels. The DCR model showed a high system throughput (32,464.7 t km -2 year -1 ), low system omnivory (0.09), low connectance index (0.36), low Finn's cycling index (4.9), and mean path length (2.8), low relative ascendency (37.5%), and high system overhead (62.5%). These indices propound that DCR is an immature and developing ecosystem with moderate strength in reserve to resist external perturbations., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The ecosystem of Bandon Bay, in the Gulf of Thailand (GoT), has been impacted since 2007 by the continued stocking of larval blue swimming crab Portunus pelagicus , also called a crab bank. In this study, the food web in the Bay was modelled using Ecopath software to compare the trophic status, interaction and energy flow among the components in the system in 2007 and 2016 (i.e., before and 10 years after the crab bank intervention). The models were based on data collected from trawling. Twenty fish and shellfish components were used in the 2007 model, while 22 were used in the 2016 model. A significant increase in biomass was found in blue swimming crab, but biomass declined for other demersal fishes, cephalopods, and Penaeid shrimps. The production/biomass ratios of most components were higher in 2016 but the consumption/biomass ratios were relatively unchanged. The ecotrophic efficiency indicated that shellfishes were more exploited than fishes. Changes in most of the ecological indices revealed higher maturity and stability after 10 years of crab bank operation. The mixed trophic impact indicated bottom-up regulation, and that the increase of blue swimming crab negatively impacted only Mantis shrimp. Overall, the results indicate positive impacts of the crab bank intervention., (© Penerbit Universiti Sains Malaysia, 2023.)

Understanding the cumulative effects of multiple stressors is a research priority in environmental science. Ecological models are a key component of tackling this challenge because they can simulate interactions between the components of an ecosystem. Here, we ask, how has the popular modeling platform Ecopath with Ecosim (EwE) been used to model human impacts related to climate change, land and sea use, pollution, and invasive species? We conducted a literature review encompassing 166 studies covering stressors other than fishing mostly in aquatic ecosystems. The most modeled stressors were physical climate change (60 studies), species introductions (22), habitat loss (21), and eutrophication (20), using a range of modeling techniques. Despite this comprehensive coverage, we identified four gaps that must be filled to harness the potential of EwE for studying multiple stressor effects. First, only 12% of studies investigated three or more stressors, with most studies focusing on single stressors. Furthermore, many studies modeled only one of many pathways through which each stressor is known to affect ecosystems. Second, various methods have been applied to define environmental response functions representing the effects of single stressors on species groups. These functions can have a large effect on the simulated ecological changes, but best practices for deriving them are yet to emerge. Third, human dimensions of environmental change - except for fisheries - were rarely considered. Fourth, only 3% of studies used statistical research designs that allow attribution of simulated ecosystem changes to stressors' direct effects and interactions, such as factorial (computational) experiments. None made full use of the statistical possibilities that arise when simulations can be repeated many times with controlled changes to the inputs. We argue that all four gaps are feasibly filled by integrating ecological modeling with advances in other subfields of environmental science and in computational statistics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

The Arctic is undergoing unprecedented change. Observations and models demonstrate significant perturbations to the physical and biological systems. Arctic species and ecosystems, particularly in the marine environment, are subject to a wide range of pressures from human activities, including exposure to a complex mixture of pollutants, climate change and fishing activity. These pressures affect the ecosystem services that the Arctic provides. Current international policies are attempting to support sustainable exploitation of Arctic resources with a view to balancing human wellbeing and environmental protection. However, assessments of the potential combined impacts of human activities are limited by data, particularly related to pollutants, a limited understanding of physical and biological processes, and single policies that are limited to ecosystem-level actions. This manuscript considers how, when combined, a suite of existing tools can be used to assess the impacts of pollutants in combination with other anthropogenic pressures on Arctic ecosystems, and on the services that these ecosystems provide. Recommendations are made for the advancement of targeted Arctic research to inform environmental practices and regulatory decisions., (© 2021. Crown.)

Tropical and subtropical rivers are being subjected to multiple stressors from human disturbance (e.g., water pollution and habitat degradation). Understanding the relationship between environmental conditions and the river ecosystem is important for improving river management. We built 14 Ecopath models composed of 28 functional groups (trophic levels [TLs] of 1.0-3.8) along a subtropical urban river to explore the influence of environmental changes on system attributes. From headwaters to downstream, the model outputs showed that the transfer efficiency (TE), energy flow parameters, and ecosystem theory indices exhibited significant (P < 0.05) differences across a longitudinal gradient of disturbance, indicating heterogeneous attributes of local river segments. The high TE values of TLs I, II, and III separated the upper, middle, and lower reaches, respectively, which could be attributed to the shift in dominant consumption flows from upstream 'periphyton - aquatic insects - insectivorous fish' to midstream 'detritus - shrimp - crustaceavorous fish' and to downstream 'phytoplankton - filter-feeding invertebrates/fish'. Structural equation modelling was used to test the causal relationships among environmental variables and demonstrated that abiotic factors directly influenced biomass composition and indirectly influenced trophic networks. Water quality, including dissolved oxygen and flow velocity; habitat characteristics, such as riffles, cobble-gravel substrate, and seasonal floodplain; and biological indicators, including the relative contributions (%) of decapods, insectivorous fish, and insect scrapers to biomass composition, had significant (P < 0.05) positive impacts on system maturity (evaluated by omnivory, connectance, and cycling indices). In the future, it will be possible to evaluate the health of river ecosystems by monitoring representative environmental factors, which could be a cost-effective approach to system-level improvement., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Invasive species exert a strong impact on the trophic structure and functioning of the ecosystem they occupy. A modeling software globally used to assess these impacts is Ecopath with Ecosim. This study measures the effects of two invasive species, African catfish Clarias gariepinus, in the food web of the Karapuzha reservoir ecosystem in India. The findings show that the two invasive species directly and indirectly influence several ecosystem elements. The high level of niche overlap (92%) and strong competition for similar resources was exhibited by C. gariepinus. The adverse effects of African catfish on all fish and crustaceans in the reservoir were revealed by mixed trophic impact. Oreochromis mossambicus impacts were both positive and negative. It had a beneficial impact on its predator aquatic birds and was negative towards minnows. This study will help fishery managers to make informed decisions for ecosystem-based fishery management of fish resources., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Ecosystem-based management relies on understanding how perturbations influence ecosystem structure and function (e.g., invasive species, exploitation, abiotic changes). However, data on unimpacted systems are scarce, therefore, we often rely on impacted systems to make inferences about 'natural states.' Among the Laurentian Great Lakes, Lake Superior provides a unique case study to address non-native species impacts because the food web is dominated by native species. Additionally, Lake Superior is both vertically (benthic versus pelagic) and horizontally (nearshore versus offshore) structured by depth, providing an opportunity to compare the function of these sub-food webs. We developed an updated Lake Superior EcoPath model using data from the 2005/2006 lake-wide multi-agency surveys covering multiple trophic levels. We then compared trophic transfer efficiency (TTE) to previously published EcoPath models. Finally, we compared ecosystem function of the 2005/2006 ecosystem to that with non-native linkages removed and compared native versus non-native species-specific approximations of TTE and trophic flow. Lake Superior was relatively efficient (TTE = 0.14) compared to systems reported in a global review (average TTE = 0.09) and the microbial loop was highly efficient (TTE > 0.20). Non-native species represented a very small proportion (<0.01%) of total biomass and were generally more efficient and had higher trophic flow compared to native species. Our results provide valuable insight into the importance of the microbial loop and represent a baseline estimate of non-native species impacts on Lake Superior. Finally, this work is a starting point for further model development to predict future changes in the Lake Superior ecosystem.

El Niño events have great impacts on marine ecosystems worldwide, ranging from low trophic plankton production to fishery resources. Understanding how ecosystems respond to El Niño is the key to the success of ecosystem-based fisheries management (EBFM). However, few studies have focussed on the ecosystems respond to this natural perturbation in China seas, and the selection of effective ecological network analyses (ENA) indicators to evaluate the ecosystem response under El Niño conditions needs to be assessed. In this study, we constructed Ecopath models for Haizhou Bay in ENSO-neutral (2013) and El Niño (2015) years. Comprehensive analyses were conducted to evaluate ENA indicators in terms of sensitivity to the ecosystem variations, robustness to the model parameters uncertainties, and statistical check. Results showed that there were obvious variations in the species composition and biomass in the Haizhou Bay ecosystem under the El Niño event. Four optimal ENA indicators were selected, including total system throughput, total primary production, total system non-cycled throughflow, and ascendency. The indicators further showed a shrunken ecosystem size, increased energetic efficiency, and less organised ecosystem under the El Niño event. These findings enhance our understanding of ecosystem dynamics and underscore the need for precautionary management under El Niño conditions. Moreover, this work can be helpful in guiding the further selection of ENA indicators for evaluating and managing marine ecosystems during El Niño events elsewhere and thusly contribute to the implementation of EBFM., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Coastal ecosystems provide important ecosystem services for millions of people. Climate change is modifying coastal ecosystem food web structure and function and threatens these essential ecosystem services. We used a combination of two new and one existing ecosystem food web models and altered scenarios that are possible with climate change to quantify the impacts of climate change on ecosystem stability in three coastal bays in Maine, United States. We also examined the impact of climate change on bivalve fisheries and aquaculture. Our modeled scenarios explicitly considered the predicted effects of future climatic change and human intervention and included: 1) the influence of increased terrestrial dissolved organic carbon loading on phytoplankton biomass; 2) benthic community change driven by synergisms between climate change, historical overfishing, and increased species invasion; and 3) altered trophic level energy transfer driven by ocean warming and acidification. The effects of climate change strongly negatively influenced ecosystem energy flow and ecosystem stability and negatively affected modeled bivalve carrying capacity in each of our models along the Maine coast of the eastern United States. Our results suggest that the interconnected nature of ecosystem food webs make them extremely vulnerable to synergistic effects of climate change. To better inform fisheries and aquaculture management, the effects of climate change must be explicitly incorporated., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Ecopath with Ecosim has been used to create mass-balance models of different type of ecosystems around the world to explore and analyse their functioning and structure. This modelling framework has become a key tool in the ecosystem approach to fisheries management, by providing a more comprehensive and holistic understanding of the interactions between the different species. Additionally, Ecopath with Ecosim has provided a useful framework to study ecosystem maturity, changes in the ecosystem functioning over time and the impact of fisheries and aquaculture on the ecosystem, among other aspects. The present work explores the ecosystem functioning and structure in an anthropogenically impacted coastal area, influenced by seasonal coastal upwelling and high input of nutrients from rias (ancient drowned tectonic valleys) off North-West Spain. A mass-balance model with 23 functional groups was created using Ecopath to study the trophic interactions in the ecosystem during the post-upwelling period (August to October) in 2017. The model described an immature, wasp-waist ecosystem, that shared characteristics of ecosystems found in upwelling areas and ecosystems found in fjords or coastal embayments. Deeper analyses highlighted the importance of small planktivorous pelagic fish as a keystone functional group, and of zooplankton, blue whiting (Micromesistius poutassou) and phytoplankton as structuring groups in the ecosystem. Additionally, the study revealed that the existing fishing pressure on species of intermediate-high trophic levels could alter ecosystem functioning and structure, and ultimately affect top predators in the area. Findings of this study provide baseline information in ecosystem functioning and structure in the area and highlight the need to deeper study the effects of fisheries and their potential impacts on top predators., Competing Interests: Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Coastal lagoons are among the most productive systems in the world. Many marine species make use of this by entering the lagoons as juveniles for nursery and growth before returning to the sea for reproduction. Humans take advantage of such fish migration processes by fishing, and exploit the high productivity for aquaculture activities. The Mar Menor is one of the largest coastal lagoons in the Mediterranean, sustaining relatively high fishing intensity despite the fact that it has traditionally been characterized as highly oligotrophic. However, in the last decades, this lagoon has suffered drastic changes induced by human activities. This has led to eutrophication, which started mainly as a consequence of changes in agricultural practices in the lagoon watershed, and triggered such fundamental changes in the system, as the mass development of jellyfish. The aim of this work is to capture and analyse the structure and functioning of the trophic web of the Mar Menor when it was still, in contrast to other coastal lagoons, oligotrophic, to provide a start point for analysing the consequences of changes in the distribution of macrophyte meadows and of eutrophication. We have compiled a detailed trophic model of this lagoon, comprising 94 compartments, using an ECOPATH model to capture the period 1980-1995. At this time the lagoon was an autotrophic system with a high net surplus of production that reached 9124.31gC/m 2 /year, while the production/biomass (P/B) ratio reached 34.56 and the total primary production/total respiration ratio was 7.01. The lagoon exported a 38.46% of total flows, including the catch by fishing, and 44.40% went to detritus. The primary production was mainly benthic (99.4%) due to the microphytobenthos and macrophytes. However, despite the fact that total fishery landings in the study period ranged between 144,835.5 and 346,708.5 kg, the gross efficiency was low, making up only 0.005% of the net primary production. This could partly be explained by the high trophic level of the fish catch (2.9), but mainly because most of the primary production (10,532.06 gC/m 2 /year) went directly to the detritus pool and was accumulated in the sediment in the Caulerpa prolifera meadows. We suggest several reasons why such high productivity coincided with low chlorophyll concentrations and good overall water quality: 1) the domination of both benthic biomass and primary production over pelagic ones with a high biomass of filter feeders, detritus feeders and scavengers, 2) high species diversity, complex and long food webs characterized by low connectance,3) the export of a significant part of the production from the system, and 4) the accumulation of surplus organic matter (as detritus) in sediments. We compare the food web of the Mar Menor in this mentioned oligotrophic stage to those of ten other lagoons in pursuit of more general implications regarding lagoon ecosystem functioning., Competing Interests: Declaration of competing interest Authors declared that the submitted work was carried out without any personal, professional or financial relationships that could potentially be construed as a conflict of interest., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

An experimental study was conducted to assess the physical and biological impacts of muddy fine sand dredged material dumped on a medium sand site Machu offshore the Seine Estuary. Complementary trophic web modelling tools were applied to the Machu ecosystem to analyse the effects of dumping operations. Results show that, after the dumping operations, the biomass of fish increased while invertebrate biomass remained relatively stable through time. Nevertheless, the biomasses of benthic invertebrates, omnivores/scavengers and predators showed some increases, while non-selective deposit feeders and filter feeders decreased. At the ecosystem level, results show that the total ecosystem activity, the ascendency and the overall omnivorous character of the food-web structure increased after dumping operations, whereas recycling subsequently decreased. Finally, the fine and medium sand habitat offshore from the Seine estuary, which undergoes regular natural physical perturbations, shows a high resilience after a short dumping phase., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This study aimed to create the first model of biological iron (Fe) cycling in the Southern Ocean food web. Two biomass mass-balanced Ecopath models were built to represent pre- and post-whaling ecosystem states (1900 and 2008). Functional group biomasses (tonnes wet weight km -2 ) were converted to biogenic Fe pools (kg Fe km -2 ) using published Fe content ranges. In both models, biogenic Fe pools and consumption in the pelagic Southern Ocean were highest for plankton and small nektonic groups. The production of plankton biomass, particularly unicellular groups, accounted for the highest annual Fe demand. Microzooplankton contributed most to biological Fe recycling, followed by carnivorous zooplankton and krill. Biological Fe recycling matched previous estimates, and, under most conditions, could entirely meet the Fe demand of bacterioplankton and phytoplankton. Iron recycling by large baleen whales was reduced 10-fold by whaling between 1900 and 2008. However, even under the 1900 scenario, the contribution of whales to biological Fe recycling was negligible compared with that of planktonic consumers. These models are a first step in examining oceanic-scale biological Fe cycling, highlighting gaps in our present knowledge and key questions for future research on the role of marine food webs in the cycling of trace elements in the sea.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'., (© 2016 The Author(s).)