B. F. Branco

Diurnal sediment resuspension and settling: impact on the coupled physical and biogeochemical dynamics of dissolved oxygen and carbon in a shallow water body

Small, shallow, inland water bodies are ubiquitous on the landscape and may be significant hotspots for biogeochemical transformations. However, the coupled physical and biogeochemical dynamics of these systems have received little attention compared with larger and deeper systems. Here, we examine the coupling between physical dynamics, sediment dynamics and oxygen-carbon dynamics in Mirror Lake, a small shallow pond in Storrs, CT, USA, using high frequency monitoring data and a simple coupled physical-biogeochemical model. The physical dynamics are characterised by a diurnal pattern of daytime thermal stratification and nighttime mixing. Observations show that the distribution of oxygen is tightly coupled with both the diurnal physical dynamics and photosynthesis-respiration reactions. Two 24-h periods in the summer of 2003 with similar meteorological conditions but distinctly different oxygen dynamics were simulated with a coupled physical-biogeochemical model. The model results suggest that the dynamics of sediment resuspension during nighttime convective overturn and subsequent settling during daytime stratification are critical in explaining the observed oxygen and dissolved inorganic carbon distributions. The diurnal dynamics provide a biogeochemical hot spot and hot moment by coupling meterologic forcing, resuspension of sediments, physical mixing and biological activity to hypoxia and anoxia in Mirror Lake.

Survival of juvenile northern quahogs during seasonal temperature decline likely a function of diet and NMI-fatty acid synthesis

ABSTRACT Aquacultured northern quahogs, Mercenaria mercenaria, set in the environment for overwintering have experienced episodes of anomalous, highly variable and site-specific overwinter mortality. Prior research has revealed factors likely contributing to mortality during isothermal winter lows, when M. mercenaria do not feed, and the postwinter approach to spring. However, a synthesis of prior studies suggests juvenile M. mercenaria survival during the prewinter period of temperature may be subject to the timely dietary availability of two highly unsaturated fatty acids, 20:5n-3, eicosapentaneoic acid, and 22:6n-3, docosahexaneoic acid, and the biosynthesis of the nonmethylene interrupted fatty acids, 22:2Δ7,13 and 22:2Δ7,15.

Nitrogen regulation by natural systems in “unnatural” landscapes: denitrification in ultra-urban coastal ecosystems

ABSTRACT Dense cities represent biogeochemical hot spots along the shoreline, concentrating fixed nitrogen that is subsequently discharged into adjacent coastal receiving waters. Thus, the ecosystem services provided by natural systems in highly urban environments can play a particularly important role in the global nitrogen cycle. In this paper, we review the recent literature on nitrogen regulation by temperate coastal ecosystems, with a focus on how the distinct physical and biogeochemical features of the urban landscape can affect the provision of this ecosystem service. We use Jamaica Bay, an ultra-urbanized coastal lagoon in the United States of America, as a demonstrative case study. Based on simple areal and tidal-based calculations, the natural systems of Jamaica Bay remove ~ 24% of the reactive nitrogen discharged by wastewater treatment plants. However, this estimate does not represent the dynamic nature of urban nitrogen cycling represented in the recent literature and highlights key research needs and opportunities. Our review reveals that ecosystem-facilitated denitrification may be significant in even the most densely urbanized coastal landscapes, but critical uncertainties currently limit incorporation of this ecosystem service in environmental management.

Extending Classrooms into Parks Through Informal Science Learning and Place-Based Education

Parks are spaces where lived experiences and science learning could come together in ways not afforded by brick and mortar informal science institutions. They offer unique opportunities for authentic science learning in that learners interact with diverse ecosystems within urban settings and engage in authentic data collection practices while making salient connections to place. In urban settings where greenspace is often a premium, parks are opportunities for educators to facilitate experiences with nature that are unparalleled in the classroom. In order to make the most of parks and other similar spaces we ask, in what ways can we engage learners in these environments? Using a theoretical lens of place attachment and identity this chapter describes how teachers form attachments to and build identities around places for science learning and place value on facilitating such experiences for their students. First, a theoretical approach to place attachment is outlined which precedes a description of the urban National Park and the teacher learning programs. Then teacher experiences and reflections juxtaposed with place attachment framework highlight notions of environmental stewardship, culturally-relevant learning, student-centered learning, and place-relevant experiences for both teachers and their students. The chapter concludes with reflections of and implications for teacher learning in park settings.

Resilience Practice in Urban Watersheds

Over the past few decades, the word “resilience” has become part of the daily lexicon of scientists, resource managers, urban planners, government agencies, and members of the public who are actively involved in stewardship of natural areas. In fact, resilience has become the new paradigm for managing coastal resources and communities in an era of increasing urbanization and changing climate. For example, President Obama signed an executive order in 2013 establishing a Task Force on Climate Preparedness and Resilience. In March 2014, the mayor of New York City established the Office of Recovery and Resiliency and made resilience a goal in One New York: The Plan for a Strong and Just City, the 2015 update of New York City’s sustainability plan.

Environmental Process Analysis, 1: Residence Time and First Order Processes

The environment is a system of coupled physical, chemical and biological processes that yield either a change in the state of the system or a dynamic steady-state. The conservation of mass equation is used to quantify such dynamic systems and is presented here with the acronym ‘IPOLA’. The time scale for a change in state of a system can be understood with the concept of residence time. We describe a simple salt flushing laboratory activity that allows detailed investigation of rates, processes and principles of dynamic systems for both the algebra-skilled student and the minimal-calculus prepared (high school and university) student. The activity focuses on the calculation and use of the residence time as a fundamental principle defining rates-of-change in systems (“How long will it take to…?”). The ‘rules-of-thumb’ (time to change by 50%, time to change by 95%) and simple estimates that can be made from real data (concentration vs. time) generated by this activity provide a useful starting point for the evaluation of the environment as a dynamic process with inherent timescales for change. Students are also introduced to conversion factors, instrument correction factors, analysis of real data and a problem solving approach based on ‘IPOLA’.

Environmental Process Analysis, 2: Dynamic Steady States

Environmental analysis requires an understanding of processes that contribute to a system and the concept of dynamic balances. The Conservation of Mass (Heat) equation for a system determines whether (e.g.) concentration (heat) in the system will increase, decrease or remain constant. The rate at which change occurs in a system and the magnitude of that change are functions of the dynamic balance and the rate constants (residence times−1) for individual processes. We express this mass (heat) balance concept as a simplified algebraic expression (“IPOLA”) and use it to evaluate the dynamics of systems. We present a classroom activity that can be accomplished in a short time with minimal cost to demonstrate these principles. Our experience suggests that this activity and the “IPOLA” equation build knowledge by developing a conceptual understanding of systems and their component processes.