An NPZ Model with State-Dependent Delay due to Size-Structure in Juvenile Zooplankton

The study of planktonic ecosystems is important as they make up the bottom trophic levels of aquatic food webs. We study a closed Nutrient-Phytoplankton-Zooplankton (NPZ) model that includes size structure in the juvenile zooplankton. The closed nature of the system allows the formulation of a conservation law of biomass that governs the system. The model consists of a system of nonlinear ordinary differential equation coupled to a partial differential equation. We are able to transform this system into a system of delay differential equations where the delay is of threshold type and is state-dependent. The system of delay differential equations can be further transformed into one with fixed delay. Using the different forms of the model we perform a qualitative analysis of the solutions, which includes studying existence and uniqueness, positivity and boundedness, local and global stability, and conditions for extinction. Key parameters that are explored are the total biomass in the system and the maturity level at which the juvenile zooplankton reach maturity. Numerical simulations are also performed to verify our analytical results

Spring plankton dynamics in the Eastern Bering Sea, 1971-2050 : mechanisms of interannual variability diagnosed with a numerical model

A new planktonic ecosystem model was constructed for the Eastern Bering Sea based on observations from the 2007-2010 BEST/BSIERP (Bering Ecosystem Study/Bering Sea Integrated Ecosystem Research Program) field program. When run with forcing from a data-assimilative ice-ocean hindcast of 1971-2012, the model performs well against observations of spring bloom time evolution (phytoplankton and microzooplankton biomass, growth and grazing rates, and ratios among new, regenerated, and export production). On the southern middle shelf (57°N, station M2), the model replicates the generally inverse relationship between ice-retreat timing and spring bloom timing known from observations, and the simpler direct relationship between the two that has been observed on the northern middle shelf (62°N, station M8). The relationship between simulated mean primary production and mean temperature in spring (15 February to 15 July) is generally positive, although this was found to be an indirect relationship which does not continue to apply across a future projection of temperature and ice cover in the 2040s. At M2, the leading direct controls on total spring primary production are found to be advective and turbulent nutrient supply, suggesting that mesoscale, wind-driven processes - A dvective transport and storminess - may be crucial to long-term trends in spring primary production in the southeastern Bering Sea, with temperature and ice cover playing only indirect roles. Sensitivity experiments suggest that direct dependence of planktonic growth and metabolic rates on temperature is less significant overall than the other drivers correlated with temperature described above

Climate impacts on U. S. living marine resources: National Marine Fisheries Services concerns, activities and needs

With the increasing recognition that climate change is occurring and having large impacts on living marine resources, a sound ecosystem approach to management of those resources requires both understanding how climate affects ecosystems and integration of that understanding into management processes. The National Marine Fisheries Service (NMFS) must identify how changing climatic conditions will impact its mission and must be prepared to adapt to these changes. This document identifies the climate related ecosystem concerns in the regional marine ecosystems for which NMFS has living marine resource management responsibilities, what NMFS is currently doing to address these concerns, what NMFS must do going forward to address these concerns, and what climate information is needed to integrate climate into resource management. The regional ecosystems included in this analysis are: the Northeast U.S. Continental Shelf; the Southeast U.S. Continental Shelf, Gulf of Mexico, and U.S. Caribbean; the California Current Ecosystem; the Alaskan Ecosystem Complex; the Pacific Island Ecosystem Complex; the Eastern Tropical Pacific; North Pacific Highly Migratory Species; and the Antarctic

A system of state-dependent delay differential equation modelling forest growth I: semiflow properties

In this article we investigate the semiflow properties of a class of state-dependent delay differential equations which is motivated by some models describing the dynamics of the number of adult trees in forests. We investigate the existence and uniqueness of a semiflow in the space of Lipschitz and $C^1$ weighted functions. We obtain a blow-up result when the time approaches the maximal time of existence. We conclude the paper with an application of a spatially structured forest model

Model-Driven Software Engineering for Computational Science Applied to a Marine Ecosystem Model

The ever-increasing complexity of in silico experiments in computational science is reflected in the growing complexity of the simulation software enabling these experiments. However, computational scientists rarely employ state-of-the-art software engineering methods, which negatively affects their productivity as well as the reliability of their scientific results. To tackle this challenge, this book introduces the Sprat Approach, which hierarchically integrates multiple domain-specific languages to facilitate the cooperation of scientists from different disciplines and to support them in creating well-engineered software without extensive software engineering training. To evaluate the Sprat Approach, it is applied to the implementation of the Sprat Marine Ecosystem Model in an exploratory case study. The Sprat Marine Ecosystem Model is a novel end-to-end ecosystem model based on population balance equations. In order to evaluate the Sprat Model, it is parametrized for the eastern Scotian Shelf ecosystem with its intertwined direct and indirect fish stock interactions, which previously could not be modeled satisfactorily. The simulation results described in this book provide new insights into the main drivers of regime shifts in marine ecosystems

PICES Press, Vol. 22, No. 2, Summer 2014

FUTURE and the FUTURE Open Science Meeting— The future of FUTURE (pp. 1-2); 2014 Inter-sessional Science Board Meeting: A note (pp. 3-5); More attractive science ecosystem design for FUTURE and beyond: A personal view (pp. 6-8); OSM Session on “Identifying multiple pressures and system responses in North Pacific marine ecosystems” (pp. 9-10); OSM Session on “Regional climate modeling in the North Pacific” (pp. 11-11); OSM Session on “Challenges in communicating science and engaging the public” (pp. 12-15); OSM Sessions on “Ecosystem status, trends, and forecasts” and “Ecosystem resilience and vulnerability” (pp. 16-17); OSM Session on “Strategies for ecosystem management in a changing climate” (pp. 18-19); OSM Workshop on “Top predators as indicators of climate change” (pp. 20-23); OSM Workshop on “Bridging the divide between models and decision-making” (pp. 24-26); OSM Workshop on “Climate change and ecosystem-based management of living marine resources” (pp. 27-28); OSM Workshop on an “Ecosystem projection model inter-comparison and assessment of climate change impacts on global fish and fisheries” (29-34); ICES Symposium on the “Ecological basis of risk analysis for marine ecosystems” (pp. 35-38); Human dimensions in the Russian Federation (pp. 39-42); Microbial Culture Collection at the National Institute for Environmental Studies, Tsukuba, Japan (pp. 43-45); The Bering Sea: Current status and recent trends (pp. 46-48); The state of the western North Pacific in the second half of 2013 (pp. 49-50); Unusual warming in the Gulf of Alaska (pp. 51-52); Obituary – Dr. Toshiro Saino (pp. 53-55); Program of topic sessions and workshops at PICES-2014 (pp. 56-56); 3rd International Symposium on “Effects of climate change on the world’s oceans” (pp. 57-57); PICES Interns (pp. 58-58