Jerry Blackford

End-To-End Models for the Analysis of Marine Ecosystems: Challenges, Issues, and Next Steps

Abstract There is growing interest in models of marine ecosystems that deal with the effects of climate change through the higher trophic levels. Such end-to-end models combine physicochemical oceanographic descriptors and organisms ranging from microbes to higher-trophic-level (HTL) organisms, including humans, in a single modeling framework. The demand for such approaches arises from the need for quantitative tools for ecosystem-based management, particularly models that can deal with bottom-up and top-down controls that operate simultaneously and vary in time and space and that are capable of handling the multiple impacts expected under climate change. End-to-end models are now feasible because of improvements in the component submodels and the availability of sufficient computing power. We discuss nine issues related to the development of end-to-end models. These issues relate to formulation of the zooplankton submodel, melding of multiple temporal and spatial scales, acclimation and adaptation, behavioral movement, software and technology, model coupling, skill assessment, and interdisciplinary challenges. We urge restraint in using end-to-end models in a true forecasting mode until we know more about their performance. End-to-end models will challenge the available data and our ability to analyze and interpret complicated models that generate complex behavior. End-to-end modeling is in its early developmental stages and thus presents an opportunity to establish an open-access, community-based approach supported by a suite of true interdisciplinary efforts.

Advective controls on primary production in the stratified western Irish Sea: An eddy‐resolving model study

[1] The Proudman Oceanographic Laboratory Coastal Ocean Modelling System and the European Regional Seas Ecosystem Model are applied at eddy-resolving (∼1.8 km) scales to the stratified region of the western Irish Sea to investigate the effects of advective transport processes on the ecosystem. We find currents can transport nutrient-rich water into the otherwise nutrient-depleted surface layer of the stratified region, fueling intermittent production throughout the summer. The currents involved fall into three classes: large-scale wind and density-driven circulation, smaller-scale eddies, and tidally mediated dispersive phenomena; all appear to play a role in this area. A model experiment without ecosystem advection does not show the intermittent surface production; summer growth only occurs at the thermocline. This experiment gives a significantly lower total annual production of 110 ± 26 g C m -2 yr -1 , compared with 150 ± 40 g C m -2 yr -1 for the full model, which is in better agreement with observational estimates of 140 g C m-2 yr -1 . We calculate summer averages of the terms in the scalar transport equation, which show that advective transport of all nutrients dominates over vertical diffusion above the thermocline in most of the stratified region. The transport of nitrate, ammonia, and phosphate is significantly greater than the transport of silicate. This can be attributed to the lack of silicate recycling in the pelagic ecosystem. Only limited and anecdotal observational evidence exists to support these model results, which points to a need for observations of high spatial and temporal resolution to investigate these processes in conjunction with further model studies.

Ocean acidification with (de)eutrophication will alter future phytoplankton growth and succession

Human activity causes ocean acidification (OA) though the dissolution of anthropogenically generated CO2 into seawater, and eutrophication through the addition of inorganic nutrients. Eutrophication increases the phytoplankton biomass that can be supported during a bloom, and the resultant uptake of dissolved inorganic carbon during photosynthesis increases water-column pH (bloom-induced basification). This increased pH can adversely affect plankton growth. With OA, basification commences at a lower pH. Using experimental analyses of the growth of three contrasting phytoplankton under different pH scenarios, coupled with mathematical models describing growth and death as functions of pH and nutrient status, we show how different conditions of pH modify the scope for competitive interactions between phytoplankton species. We then use the models previously configured against experimental data to explore how the commencement of bloom-induced basification at lower pH with OA, and operating against a background of changing patterns in nutrient loads, may modify phytoplankton growth and competition. We conclude that OA and changed nutrient supply into shelf seas with eutrophication or de-eutrophication (the latter owing to pollution control) has clear scope to alter phytoplankton succession, thus affecting future trophic dynamics and impacting both biogeochemical cycling and fisheries.

Assessing the environmental consequences of CO2 leakage from geological CCS: Generating evidence to support environmental risk assessment

At the start of the industrial revolution (circa 1750) the atmospheric concentration of carbon dioxide (CO2) was around 280 ppm. Since that time the burning of fossil fuel, together with other industrial processes such as cement manufacture and changing land use, has increased this value to 400 ppm, for the first time in over 3 million years. With CO2 being a potent greenhouse gas, the consequence of this rise for global temperatures has been dramatic, and not only for air temperatures. Global Sea Surface Temperature (SST) has warmed by 0.4–0.8 °C during the last century, although regional differences are evident (IPCC, 2007). This rise in atmospheric CO2 levels and the resulting global warming to some extent has been ameliorated by the oceanic uptake of around one quarter of the anthropogenic CO2 emissions (Sabine et al., 2004). Initially this was thought to be having little or no impact on ocean chemistry due to the capacity of the ocean’s carbonate buffering system to neutralise the acidity caused when CO2 dissolves in seawater. However, this assumption was challenged by Caldeira and Wickett (2005) who used model predictions to show that the rate at which carbonate buffering can act was far too slow to moderate significant changes to oceanic chemistry over the next few centuries. Their model predicted that since pre-industrial times, ocean surface water pH had fallen by 0.1 pH unit, indicating a 30% increase in the concentration of H+ ions. Their model also showed that the pH of surface waters could fall by up to 0.4 units before 2100, driven by continued and unabated utilisation of fossil fuels. Alongside increasing levels of dissolved CO2 and H+ (reduced pH) an increase in bicarbonate ions together with a decrease in carbonate ions occurs. These chemical changes are now collectively recognised as “ocean acidification”. Concern now stems from the knowledge that concentrations of H+, CO2, bicarbonate and carbonate ions impact upon many important physiological processes vital to maintaining health and function in marine organisms. Additionally, species have evolved under conditions where the carbonate system has remained relatively stable for millions of years, rendering them with potentially reduced capacity to adapt to this rapid change. Evidence suggests that, whilst the impact of ocean acidification is complex, when considered alongside ocean warming the net effect on the health and productivity of the oceans will be detrimental.

Modelling impacts and recovery in benthic communities exposed to localised high CO2

Regulations pertaining to carbon dioxide capture with offshore storage (CCS) require an understanding of the potential localised environmental impacts and demonstrably suitable monitoring practices. This study uses a marine ecosystem model to examine a comprehensive range of hypothetical CO2 leakage scenarios, quantifying both impact and recovery time within the benthic system. Whilst significant mortalities and long recovery times were projected for the larger and longer term scenarios, shorter-term or low level exposures lead to reduced projected impacts. This suggests that efficient monitoring and leak mitigation strategies, coupled with appropriate selection of storage sites can effectively limit concerns regarding localised environmental impacts from CCS. The feedbacks and interactions between physiological and ecological responses simulated reveal that benthic responses to CO2 leakage could be complex. This type of modelling investigation can aid the understanding of impact potential, the role of benthic community recovery and inform the design of baseline and monitoring surveys.

Changes in DMS production and flux in relation to decadal shifts in ocean circulation

A fundamental question is are the biological processes regulating dimethylsulphide (DMS) production by the marine ecosystem interconnected and responding to atmospheric or ocean signals at decadal timescales? Related to this is a need to quantify how climate change affects these interconnections and understand the expected levels of natural variability on decadal timescales. To explore this we have used indicators of climate variability [the Gulf Stream North Wall (GSNW) and the North Atlantic Oscillation (NAO) indices] as probes to demonstrate that a marine ecosystem model, incorporating DMS production, can extract and amplify a climatic signal, which is spread across a variety of meteorological variables. The GSNW signal is imparted through the wind and cloud forcing, despite the fact there was not significant relationship observed between the GSNW index and the meteorological forcing data. The model simulations appear to reproduce observed decadal variability in phytoplankton community structure in the eastern North Atlantic and imply that DMS(P) biogeochemistry may vary on decadal timescales as a consequence of changes in community structure. The GSNW index is a potential indicator of such changes and there may have been a regime shift in DMSP production in the eastern North Atlantic coincident with that observed for plankton. Sensitivity analysis indicates that the impact of climate variability on DMS biogeochemistry may potentially be damped by the ability of microbial communities to adapt physiologically to the effects of changes in light and nutrients.

CO2 leakage from geological storage facilities: environmental, societal and economic impacts, monitoring and research strategies

Carbon capture and storage (CCS) has the potential to significantly limit CO 2 emissions to the atmosphere; however a leakage of CO 2 from transport or storage could have environmental and safety implications. Monitoring of CCS storage is a further challenge, both to assure the public and, should leakage occur, to enable mitigation and verification. This chapter reviews the current state of knowledge regarding environmental sensitivities and monitoring and outlines the challenges for research over the next few years. The current hypothesis is that significantly large leaks would be required to cause noticeable damage in the ecosystem.

Eddy resolved ecosystem modelling in the Irish Sea

A computationally efficient three-dimensional modelling system (Proudman Oceanographic Laboratory Coastal-Ocean Modelling System, POLCOMS) has been developed for the simulation of shelf-sea, ocean and coupled shelf-ocean processes. The system is equally suited for use on single processor workstations and massively parallel supercomputers, and particular features of its numerics are an arbitrary (terrain following) vertical coordinate system, a feature preserving advection scheme and accurate calculation of horizontal pressure gradients, even in the presence of steep topography. One of the roles of this system is to act as a host to ecosystem models, so that they can interact with as accurate a physical environment as is currently feasible. In this study, a hierarchy of nested models links the shelf-wide circulation and ecosystem, via a high resolution physics model of the whole Irish Sea, to the test domain: a region of the western Irish Sea. In this domain, ecosystem models are tested at a resolution of ~1.5km (c.f. the typical summer Rossby radius of 4km). Investigations in the physics-only model show the significance of advective processes (particularly shear diffusion and baroclinic eddies) in determining the vertical and horizontal temperature structure in this region. Here we investigate how a hierarchy of complexity (and computational load) from a 1D point model to a fully 3D eddy resolved model affects the distribution of phytoplankton (and primary production) and nutrients predicted by the European Regional Seas Ecosystem Model (ERSEM), a complex multi-compartment ecosystem model. We shall also show how the parallel programming features of the POLCOMS code allows large-scale simulations to be carried out on hundreds, and now on over a thousand, processors, approaching Teraflop/s performance levels. This is shown using a series of benchmark runs on the 1280 processor IBM POWER4 system operated by the UKs HPCx Consortium.

Modelling marine sediment biogeochemistry: Current knowledge gaps, challenges, and some methodological advice for advancement

The benthic environment is a crucial component of marine systems in the provision of ecosystem services, sustaining biodiversity and in climate regulation, and therefore important to human society. With the contemporary increase in computational power, model resolution and technological improvements in quality and quantity of benthic data, it is necessary to ensure that benthic systems are appropriately represented in coupled benthic-pelagic biogeochemical and ecological modelling studies. In this paper we focus on five topical challenges related to various aspects of modelling benthic environments: organic matter reactivity, dynamics of benthic-pelagic boundary layer, microphytobenthos, biological transport and small-scale heterogeneity, and impacts of episodic events. We discuss current gaps in their understanding and indicate plausible ways ahead. Further, we propose a three-pronged approach for the advancement of benthic and benthic-pelagic modelling, essential for improved understanding, management and prediction of the marine environment. This includes: (A) development of a traceable and hierarchical framework for benthic-pelagic models, which will facilitate integration among models, reduce risk of bias, and clarify model limitations; (B) extended cross-disciplinary approach to promote effective collaboration between modelling and empirical scientists of various backgrounds and better involvement of stakeholders and end-users; (C) a common vocabulary for terminology used in benthic modelling, to promote model development and integration, and also to enhance mutual understanding.

WP4 result summary report relevant for "Environmental Best Practice"

This report presents a distillation of the main findings from ECO2 WP4, together with information available from other EU and Nationally funded projects, presented within and specifically for the context of Environmental Best Practice. The information and key messages contained within this deliverable (D4.4) will be directly applied to the project wide “Guidance on Environmental Best Practice” and will form the basis of Chapter 6 “Assessing biological impact of CO2 leakage”. There were 8 key findings that came from the ECO2 research conducted with WP4: - Exposure to elevated levels of CO2 has a negative impact on marine organisms - There is a wide range of CO2 sensitivities across different marine taxa and groups - Care must be taken when predicting species specific response and sensitivity to CO2 for Environmental Risk Assessments - Exposure to elevated levels of CO2 has a negative impact on marine communities, biodiversity and ecosystem processes / functions - The leakage / release of formation water can have a negative impact on marine organisms - Other environmental factors could exacerbate or ameliorate the impact of CCS leakage - Some biological responses may be employed in a programme of Environmental Monitoring - Collecting spatially and temporally referenced biological data is important for creating effective Baseline Surveys