A physically coupled end-to-end model platform for coastal ecosystems: Simulating the effects of climate change and changing upwelling characteristics on the Northern California Current ecosystem

Abstract

We describe a spatially explicit, intermediate complexity end-to-end model platform that integrates physical, trophic, and nutrient cycling processes. A two-dimensional advection and mixing model drives nitrate input into the model continental shelf domain, the transport of nutrients and plankton between sub-regions, and the export of nutrients and plankton from the model domain. Trophic relationships are defined by classical mass-balanced food web model techniques (e.g., ECOPATH). Inclusion of nitrate and ammonium nutrient pools and bacterial recycling of detritus allows consideration of alternate "new" vs "recycled" production regimes. The model platform was applied to the Northern California Current (NCC) shelf ecosystem. Seasonal upwelling of nutrients along the coast is the primary driver of NCC productivity, however the characteristics of upwelling vary considerably between years and are expected to change into the future as a result of global climate change. The model was run under alternate physical driver scenarios to examine the effects of changing upwelling characteristics on the production and spatial distribution of functional groups across all trophic levels. Productivity on the shelf had a dome-shaped relationship with upwelling strength. As the intensity of individual upwelling events increased, productivity increased throughout the food web. However, strong upwelling had a detrimental effect when the physical export of plankton exceeded the capacity of

Trophic flow structure of a neotropical estuary in northeastern Brazil and the comparison of ecosystem model indicators of estuaries

“…Ecosystem models attempt to represent the entire ecological system by considering the interactions between its components. They have been increasingly developed worldwide as tools for evaluating the impact of climate change and fishing pressure in coastal areas (Bentorcha et al, 2017;Ruzicka et al, 2016). In addition, they can simulate scenarios that support the Ecosystem Approach to Fisheries (EAF) (Corrales et al, 2015;FAO, 2003).…”

Comparing the roles of Pacific halibut and arrowtooth flounder within the Gulf of Alaska ecosystem and fishing economy

“…Trophic matrix A cp is expanded to include nutrient and detritus pools and account for the distribution of all consumption by group p between its consumers, between nutrient and detritus pools via feces and ammonium excretion, or to detritus as senescence. A model expressed in this format can readily be used to quantify the consequences of changes to community composition (Robinson et al., ; Ruzicka et al., ), changes to external subsidies of nutrients and plankton (Treasure, Ruzicka, Moloney, Gurney, & Ansorge, ; Treasure, Ruzicka, Pakhomov, & Ansorge, ), changes in oceanographic regime through coupled physical models (Ruzicka et al., , ), changes in fishery management policy, or changes to the physiology or diet of any functional group.…”

“…ECOTRAN models are based on the transformation of the solution for a system of linear equations describing predation pressure upon all members of a food web, such as solved by ecopath, into a donor-driven trophic matrix A cp that maps the fate of all production by groups p through the food web to consumers c (Steele, 2009;Steele & Ruzicka, 2011): where matrix D pc is the fraction of each producer p within the diet of each consumer c, q c is the total consumption rate of consumer c, and term ∑ c D pc q c is the total grazing or predation rate upon each producer p by all consumers c. Trophic matrix A cp is expanded to include nutrient and detritus pools and account for the distribution of all consumption by group p between its consumers, between nutrient and detritus pools via feces and ammonium excretion, or to detritus as senescence. A model expressed in this format can readily be used to quantify the consequences of changes to community composition (Robinson et al, 2015;Ruzicka et al, 2012), changes to external subsidies of nutrients and plankton (Treasure, Ruzicka, Moloney, Gurney, & Ansorge, 2015;Treasure, Ruzicka, Pakhomov, & Ansorge, 2018), changes in oceanographic regime through coupled physical models (Ruzicka et al, 2016, changes in fishery management policy, or changes to the physiology or diet of any functional group.…”

“…CGoA‐ECOTRAN adds separate descriptions for the food webs of five subregions within the western and central CGoA. The model is run within a platform allowing for rapid estimation of the consequences of changes to community structure and fishing pressure and is intended to be coupled with ocean current and plankton production models for time‐dynamic simulations under alternate physical regimes in future studies (e.g., Ruzicka, Brink, Gifford, & Bahr, ; Ruzicka, Steele, Brink, Gifford, & Bahr, ). We apply the model to (a) quantify the importance of halibut and arrowtooth to the ecosystem in terms of energy demand upon lower trophic levels and energy contribution to higher trophic levels.…”

Linking Chlorophyll Concentration and Wind Patterns Using Satellite Data in the Central and Northern California Current System

“…This finding implies that the optimal wind speed for maximum productivity varies with latitude and shelf width. More recently, in a more complex simulation built upon a traditional ECOPATH food web model that incorporates upwelling dynamics, Ruzicka et al (2016) FIGURE 1 | A conceptual diagram representing the Botsford et al (2003) relationship. The relationship between shelf chlorophyll concentration and upwelling-favorable wind stress (black curve) results from the balance between the chlorophyll response to nutrient availability (red dashed arrow) and the chlorophyll response to cross-shelf export of biomass (blue dashed arrow).…”