Letelier Ricardo M.

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Ricardo M.

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  • Preprint
    Hierarchical and dynamic seascapes : a quantitative framework for scaling pelagic biogeochemistry and ecology
    ( 2013-10-07) Kavanaugh, Maria T. ; Hales, Burke ; Saraceno, Martin ; Spitz, Yvette H. ; White, Angelicque E. ; Letelier, Ricardo M.
    Comparative analyses of oceanic ecosystems require an objective framework to define coherent study regions and scale the patterns and processes observed within them. We applied the hierarchical patch mosaic paradigm of landscape ecology to the study of the seasonal variability of the North Pacific to facilitate comparative analysis between pelagic ecosystems and provide spatiotemporal context for Eulerian time-series studies. Using 13-year climatologies of sea surface temperature (SST), photosynthetically active radiation (PAR), and chlorophyll a (chl-a), we classified seascapes in environmental space that were monthly-resolved, dynamic and nested in space and time. To test the assumption that seascapes represent coherent regions with unique biogeochemical function and to determine the hierarchical scale that best characterized variance in biogeochemical parameters, independent data sets were analyzed across seascapes using analysis of variance (ANOVA), nested-ANOVA and multiple linear regression (MLR) analyses. We also compared the classification efficiency (as defined by the ANOVA F-statistic) of resultant dynamic seascapes to a commonly-used static classification system. Variance of nutrients and net primary productivity (NPP) were well characterized in the first two levels of hierarchy of eight seascapes nested within three superseascapes (R2 = 0.5-0.7). Dynamic boundaries at this level resulted in a nearly 2-fold increase in classification efficiency over static boundaries. MLR analyses revealed differential forcing on pCO2 across seascapes and hierarchical levels and a 33 % reduction in mean model error with increased partitioning (from 18.5 μatm to 12.0 μatm pCO2). Importantly, the empirical influence of seasonality was minor across seascapes at all hierarchical levels, suggesting that seascape partitioning minimizes the effect of non-hydrographic variables. As part of the emerging field of pelagic seascape ecology, this effort provides an improved means of monitoring and comparing oceanographic biophysical dynamics and an objective, quantitative basis by which to scale data from local experiments and observations to regional and global biogeochemical cycles.
  • Article
    Seascapes as a new vernacular for pelagic ocean monitoring, management and conservation
    (Oxford University Press, 2016-07-18) Kavanaugh, Maria T. ; Oliver, Matthew J. ; Chavez, Francisco P. ; Letelier, Ricardo M. ; Muller-Karger, Frank E. ; Doney, Scott C.
    For terrestrial and marine benthic ecologists, landscape ecology provides a framework to address issues of complexity, patchiness, and scale—providing theory and context for ecosystem based management in a changing climate. Marine pelagic ecosystems are likewise changing in response to warming, changing chemistry, and resource exploitation. However, unlike spatial landscapes that migrate slowly with time, pelagic seascapes are embedded in a turbulent, advective ocean. Adaptations from landscape ecology to marine pelagic ecosystem management must consider the nature and scale of biophysical interactions associated with organisms ranging from microbes to whales, a hierarchical organization shaped by physical processes, and our limited capacity to observe and monitor these phenomena across global oceans. High frequency, multiscale, and synoptic characterization of the 4-D variability of seascapes are now available through improved classification methods, a maturing array of satellite remote sensing products, advances in autonomous sampling of multiple levels of biological complexity, and emergence of observational networks. Merging of oceanographic and ecological paradigms will be necessary to observe, manage, and conserve species embedded in a dynamic seascape mosaic, where the boundaries, extent, and location of features change with time.
  • Article
    A framework for a marine biodiversity observing network within changing continental shelf seascapes
    (The Oceanography Society, 2014-06) Muller-Karger, Frank E. ; Kavanaugh, Maria T. ; Montes, Enrique ; Balch, William M. ; Breitbart, Mya ; Chavez, Francisco P. ; Doney, Scott C. ; Johns, Elizabeth M. ; Letelier, Ricardo M. ; Lomas, Michael W. ; Sosik, Heidi M. ; White, Angelicque E.
    Continental shelves and the waters overlying them support numerous industries as diverse as tourism and recreation, energy extraction, fisheries, transportation, and applications of marine bio-molecules (e.g., agribusiness, food processing, pharmaceuticals). Although these shelf ecosystems exhibit impacts of climate change and increased human use of resources (Halpern et al., 2012; IPCC, 2013, 2014; Melillo et al., 2014), there are currently no standardized metrics for assessing changes in ecological function in the coastal ocean. Here, we argue that it is possible to monitor vital signs of ecosystem function by focusing on the lowest levels of the ocean food web. Establishment of biodiversity, biomass, and primary productivity baselines and continuous evaluation of changes in biological resources in these economically and ecologically valuable regions requires an internationally coordinated monitoring effort that fully integrates natural, social, and economic sciences to jointly identify problems and design solutions. Such an ocean observing network is needed to protect the livelihoods of coastal communities in the context of the goals of the Future Earth program (Mooney et al., 2013) and of the Intergovernmental Platform on Biodiversity and Ecosystem Services (http://www.ipbes.net). The tools needed to initiate these assessments are available today.
  • Article
    Ocean time series observations of changing marine ecosystems: An era of integration, synthesis, and societal applications
    (Frontiers Media, 2019-07-12) Benway, Heather M. ; Lorenzoni, Laura ; White, Angelicque E. ; Fiedler, Björn ; Levine, Naomi M. ; Nicholson, David P. ; DeGrandpre, Michael D. ; Sosik, Heidi M. ; Church, Matthew J. ; O'Brien, Todd D. ; Leinen, Margaret S. ; Weller, Robert A. ; Karl, David M. ; Henson, Stephanie A. ; Letelier, Ricardo M.
    Sustained ocean time series are critical for characterizing marine ecosystem shifts in a time of accelerating, and at times unpredictable, changes. They represent the only means to distinguish between natural and anthropogenic forcings, and are the best tools to explore causal links and implications for human communities that depend on ocean resources. Since the inception of sustained ocean observations, ocean time series have withstood many challenges, most prominently availability of uninterrupted funding and retention of trained personnel. This OceanObs’19 review article provides an overarching vision for sustained ocean time series observations for the next decade, focusing on the growing challenges of maintaining sustained ocean time series, including ship-based and autonomous coastal and open-ocean platforms, as well as remote sensing. In addition to increased diversification of funding sources to include the private sector, NGOs, and other groups, more effective engagement of stakeholders and other end-users will be critical to ensure the sustainability of ocean time series programs. Building a cohesive international time series network will require dedicated capacity to coordinate across observing programs and leverage existing infrastructure and platforms of opportunity. This review article outlines near-term observing priorities and technology needs; explores potential mechanisms to broaden ocean time series data applications and end-user communities; and describes current tools and future requirements for managing increasingly complex multi-platform data streams and developing synthesis products that support science and society. The actionable recommendations outlined herein ultimately form the basis for a robust, sustainable, fit-for-purpose time series network that will foster a predictive understanding of changing ocean systems for the benefit of society.
  • Article
    Short-term variability in euphotic zone biogeochemistry and primary productivity at Station ALOHA : a case study of summer 2012
    (John Wiley & Sons, 2015-08-13) Wilson, Samuel T. ; Barone, Benedetto ; Ascani, Francois ; Bidigare, Robert R. ; Church, Matthew J. ; del Valle, Daniela A. ; Dyhrman, Sonya T. ; Ferroon, Sara ; Fitzsimmons, Jessica N. ; Juranek, Laurie W. ; Kolber, Zbigniew S. ; Letelier, Ricardo M. ; Martinez-Garcia, Sandra ; Nicholson, David P. ; Richards, Kelvin J. ; Rii, Yoshimi M. ; Rouco, Monica ; Viviani, Donn A. ; White, Angelicque E. ; Zehr, Jonathan P. ; Karl, David M.
    Time-series observations are critical to understand the structure, function, and dynamics of marine ecosystems. The Hawaii Ocean Time-series program has maintained near-monthly sampling at Station ALOHA (22°45′N, 158°00′W) in the oligotrophic North Pacific Subtropical Gyre (NPSG) since 1988 and has identified ecosystem variability over seasonal to interannual timescales. To further extend the temporal resolution of these near-monthly time-series observations, an extensive field campaign was conducted during July–September 2012 at Station ALOHA with near-daily sampling of upper water-column biogeochemistry, phytoplankton abundance, and activity. The resulting data set provided biogeochemical measurements at high temporal resolution and documents two important events at Station ALOHA: (1) a prolonged period of low productivity when net community production in the mixed layer shifted to a net heterotrophic state and (2) detection of a distinct sea-surface salinity minimum feature which was prominent in the upper water column (0–50 m) for a period of approximately 30 days. The shipboard observations during July–September 2012 were supplemented with in situ measurements provided by Seagliders, profiling floats, and remote satellite observations that together revealed the extent of the low productivity and the sea-surface salinity minimum feature in the NPSG.
  • Article
    Satellite sensor requirements for monitoring essential biodiversity variables of coastal ecosystems
    (John Wiley & Sons, 2018-03-06) Muller-Karger, Frank E. ; Hestir, Erin ; Ade, Christiana ; Turpie, Kevin ; Roberts, Dar A. ; Siegel, David A. ; Miller, Robert J. ; Humm, David ; Izenberg, Noam ; Keller, Mary ; Morgan, Frank ; Frouin, Robert ; Dekker, Arnold G. ; Gardner, Royal ; Goodman, James ; Schaeffer, Blake ; Franz, Bryan A. ; Pahlevan, Nima ; Mannino, Antonio ; Concha, Javier A. ; Ackleson, Steven G. ; Cavanaugh, Kyle C. ; Romanou, Anastasia ; Tzortziou, Maria ; Boss, Emmanuel S. ; Pavlick, Ryan ; Freeman, Anthony ; Rousseaux, Cecile S. ; Dunne, John P. ; Long, Matthew C. ; Salas, Eduardo Klein ; McKinley, Galen A. ; Goes, Joachim I. ; Letelier, Ricardo M. ; Kavanaugh, Maria T. ; Roffer, Mitchell ; Bracher, Astrid ; Arrigo, Kevin R. ; Dierssen, Heidi M. ; Zhang, Xiaodong ; Davis, Frank W. ; Best, Benjamin D. ; Guralnick, Robert P. ; Moisan, John R. ; Sosik, Heidi M. ; Kudela, Raphael M. ; Mouw, Colleen B. ; Barnard, Andrew H. ; Palacios, Sherry ; Roesler, Collin S. ; Drakou, Evangelia G. ; Appeltans, Ward ; Jetz, Walter
    The biodiversity and high productivity of coastal terrestrial and aquatic habitats are the foundation for important benefits to human societies around the world. These globally distributed habitats need frequent and broad systematic assessments, but field surveys only cover a small fraction of these areas. Satellite‐based sensors can repeatedly record the visible and near‐infrared reflectance spectra that contain the absorption, scattering, and fluorescence signatures of functional phytoplankton groups, colored dissolved matter, and particulate matter near the surface ocean, and of biologically structured habitats (floating and emergent vegetation, benthic habitats like coral, seagrass, and algae). These measures can be incorporated into Essential Biodiversity Variables (EBVs), including the distribution, abundance, and traits of groups of species populations, and used to evaluate habitat fragmentation. However, current and planned satellites are not designed to observe the EBVs that change rapidly with extreme tides, salinity, temperatures, storms, pollution, or physical habitat destruction over scales relevant to human activity. Making these observations requires a new generation of satellite sensors able to sample with these combined characteristics: (1) spatial resolution on the order of 30 to 100‐m pixels or smaller; (2) spectral resolution on the order of 5 nm in the visible and 10 nm in the short‐wave infrared spectrum (or at least two or more bands at 1,030, 1,240, 1,630, 2,125, and/or 2,260 nm) for atmospheric correction and aquatic and vegetation assessments; (3) radiometric quality with signal to noise ratios (SNR) above 800 (relative to signal levels typical of the open ocean), 14‐bit digitization, absolute radiometric calibration <2%, relative calibration of 0.2%, polarization sensitivity <1%, high radiometric stability and linearity, and operations designed to minimize sunglint; and (4) temporal resolution of hours to days. We refer to these combined specifications as H4 imaging. Enabling H4 imaging is vital for the conservation and management of global biodiversity and ecosystem services, including food provisioning and water security. An agile satellite in a 3‐d repeat low‐Earth orbit could sample 30‐km swath images of several hundred coastal habitats daily. Nine H4 satellites would provide weekly coverage of global coastal zones. Such satellite constellations are now feasible and are used in various applications.