Capturing episodic impacts of environmental signals

Environmental scientists frequently rely on time series of explanatory variables to explain their impact on an important response variable. However, sometimes, researchers are less interested in raw observations of an explanatory variable than in derived indices induced by episodes embedded in its time series. Often these episodes are intermittent, occur within a specific limited memory, persist for varying durations, at varying levels of intensity, and overlap important periods with respect to the response variable. We develop a generic, parametrised, family of weighted indices extracted from an environmental signal called IMPIT indices. To facilitate their construction and calibration, we developed a user friendly app in Shiny R referred to as IMPIT-a. We construct examples of IMPIT indices extracted from the Southern Oscillation Index and sea surface temperature signals. We illustrate their applications to two fished species in Queensland waters (i.e., snapper and saucer scallop) and wheat yield in New South Wales.Comment: 27 page

Inferring the occurrence of regime shifts in a shallow lake during the last 250 years based on multiple indicators

Regime shifts are ecosystem-scale phenomena. In lake studies, most supporting evidence is frequently based on a single state variable. We examined the sediment record of the shallow lake Blanca Chica (Argentina) to explore the response of multiple proxies belonging to different trophic levels (nutrients, chlorophyll and carotenoid pigments, diatoms, Cladocera remains, and Rotifera resting eggs) over the last 250 yr. We explored different ecological indicators to assess changes consistent with regime shifts. To do so, first we identified the timing of transitional periods on multiple-proxies. Then, we explored (1) the nature of the change (linear versus non-linear dynamics), (2) different indicators of a shift across the food web: multimodality and resilience indicators (standard deviation and autocorrelation), and (3) examined the synchronicity of the detected indicators at multiple-trophic levels. Generalized additive models fitted to the ordination scores of the assemblages analyzed revealed two transitions: ca. 1860–1900, and 1915–1990. Ecological indicators of regime shifts revealed that the first transition is consistent with a threshold state response (change in the ecosystem state manifest as a jump when the driver exceeds a state threshold), and the second one with a critical transition (hysteretic transition in which the system change to an alternate stable state). After the first transition lake structure shifted from littoral to pelagic species dominance (evidenced by Cladocera and diatom assemblages), and turbidity increased, indicating a rise in lake water level. This transition was non-linear, showed multimodality, and is most likely driven by an increase in precipitation registered in the region since 1870. During the second transition, nutrient levels rose, all indicators showed multimodality, non-linear dynamics and an increase in standard deviation prior to the regime shift. These dynamics are consistent with a critical transition in response to eutrophication, and coincides with a post-1920 change in land use. Our results show that several ecological indicators of regime shifts need to be examined to perform an accurate diagnosis. We highlight the relevance of a multi-proxy approach including multiple-trophic level responses as the appropriate scale of analysis to determine the occurrence, type and dynamics of regime shifts. We also show that resilience indicators and critical transitions can be detectable in the whole food web and that shallow lakes can undergo different types of regime shifts.Fil: Gonzalez Sagrario, Maria de Los Angeles. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Musazzi, Simona. Consiglio Nazionale delle Ricerche; ItaliaFil: Cordoba, Francisco Elizalde. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mendiolar, Manuela. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Lami, Andrea. Consiglio Nazionale delle Ricerche; Itali

Daniel Raúl Hernández: Matemático

Daniel Hernández has passed away and after his disappearance our INIDEP community will no longer be the same...Daniel Hernández ha fallecido y luego de su desaparición nuestra comunidad del INIDEP ya no será la misma..

¿Qué criterios y consideraciones debemos tener en cuenta cuando hablamos de cambio de régimen en los lagos someros?

Los lagos someros o lagunas, experimentan cambios de régimen. Sin embargo, para dar cuenta de ello diversos criterios y/o indicadores necesitan ser evaluados. Este trabajo tiene como objetivo mostrar las distintas herramientas que pueden considerarse a la hora de definir un cambio de régimen en un ecosistema. Para ello, se tomó como ejemplo un estudio paleolimnológico realizado en la Laguna Blanca Chica (Olavarría), que incluye el análisis de múltiples indicadores pertenecientes a distintos niveles tróficos y el empleo de distintas herramientas estadísticas (GAM, density curves, Early warning signals). De este estudio se desprende que para poder establecer si un cambio de régimen ocurrió es necesario contar con una serie temporal de datos extendida en el tiempo, testear la ocurrencia de transiciones y caracterizar su dinámica considerando diversos niveles de la trama trófica del ecosistema.Fil: Gonzalez Sagrario, Maria de Los Angeles. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Muzzasi, Simona. Consiglio Nazionale delle Ricerche; ItaliaFil: Cordoba, Francisco Elizalde. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; ArgentinaFil: Mendiolar, Manuela. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Lami, Andrea. Consiglio Nazionale delle Ricerche; ItaliaX Congreso de Ecología y Manejo de Ecosistemas Acuáticos Pampeanos (EMEAP 2019)AzulArgentinaInstituto de Hidrología de Llanuras "Dr. Eduardo J. Usunoff"Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentabl

Evolución temporal de la diversidad, abundancia y estructura del ensamble de peces costeros en el área de “El Rincón” (39° S-41° 30′ S), Argentina

‘El Rincón’ area (39° S-41° 30′ S) is a highly complex system, of relevance as a reproductive and nursery area for numerous species subject to various fisheries management    measures. The objective of this study was to evaluate the temporal evolution of the coastal fish assemblage in the area. We analyzed 591 fishing hauls and oceanographic stations during 1994-2012 based on fish density, diversity and assemblage structure, evaluating interannual differences and their relationship with oceanographic variables. Seventy species of coastal fish were recorded, eleven of them responsible for the differences in assemblages between years. Most notable results were the decreasing trend in fish density, as well as the positive relationship between density and bottom temperature. This work is relevant as a baseline of the evolution of the coastal fish assemblage, together with an exhaustive characterization of the biological and physical dynamics of the region over a period of almost two decades. Results obtained are of importance for the management of coastal resources, future studies framed in the global climate change paradigm and evaluation of the anthropic impact on this coastal ecosystem of the Southwest Atlantic that provides numerous ecosystem services.El área de “El Rincón” (39° S-41° 30′ S) es un sistema de alta complejidad oceanográfica, de relevancia como área reproductiva y cría de numerosas especies, sujeta a diversas medidas de manejo pesquero. El objetivo del trabajo fue evaluar la evolución temporal del ensamble de peces costeros en el área. Se analizaron 591 lances de pesca y estaciones oceanográficas durante el período 1994-2012 en función de la densidad de peces, la diversidad y la estructura del ensamble, evaluando diferencias interanuales y su relación con variables oceanográficas. Se registraron 70 especies de peces costeros, once de ellas responsables de las diferencias en los ensambles entre años. Los resultados más destacables fueron la tendencia decreciente de la densidad de peces, así como la relación positiva entre la densidad y la temperatura de fondo. El presente trabajo reviste importancia como línea de base de la evolución del ensamble de peces costeros, junto a una exhaustiva caracterización de la dinámica biológica y física de la región en un período de casi dos décadas. Los resultados obtenidos son de importancia para la gestión de recursos costeros, futuros estudios enmarcados en el contexto del cambio climático global y evaluación del impacto antrópico en este ecosistema costero del Atlántico Sudoccidental que brinda numerosos servicios ecosistémicos

Phytoplankton and protozooplankton on the southern Patagonian shelf (Argentina, 47°–55°S) in late summer: Potentially toxic species and community assemblage structure linked to environmental features

On the southern Patagonian shelf (Argentina, 47°–55°S) phyto- and protozooplankton are key structural and functional components of a complex trophic web that sustains commercially important species. During late summer 2004, spatial structure, assemblage species and their association with environmental characteristics of water masses were studied for the 2–200 μm phyto- and protozooplankton communities. Ultraplankton 2–5 μm was the most abundant size-fraction (90%), followed by the lower nanoplankton 5–10 μm (7.5%), the larger nanoplankton 10–20 μm (1.5%), and microplankton 20–200 μm (1%). Several of the 319 morpho-species found are potentially toxic taxa (the dinoflagellates Alexandrium tamarense, Protoceratium reticulatum, Dinophysis acuminata, Prorocentrum cordatum, Karenia and amphidomataceans and the diatom genus Pseudo-nitzschia), and this is important since the area sustains significant fisheries. A ultraphytoeukaryotic coccal cell (probably chlorophyte/prasinophyte) (3 μm), P. cordatum, and a microplankton naked ciliate were the morpho-species with the highest abundance and occurrence. Abundance and biodiversity patterns indicated that the plankton community structure was heterogeneous vertically, cross-shelf, and along-shelf, suggesting shifts in community structure over the region. Five areas with dissimilar plankton assemblages were defined, each corresponding to different environments. Depth, bathymetry, latitude and temperature were the most explanatory variables for the assemblage distribution patterns observed. This south Patagonian region possesses important fisheries and, considering expected environmental changes, our results help to understand the spatial structure of plankton communities over a broad size spectrum.Fil: Antacli, Julieta Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Silva, Ricardo L. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Jaureguizar, Andrés Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Hernández, Daniel R. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Mendiolar, Manuela. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Sabatini, Marina Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Akselman, Rut. Instituto Nacional de Investigaciones y Desarrollo Pesquero; Argentin

Cost–benefit analysis of ecosystem modeling to support fisheries management

Mathematical and statistical models underlie many of the world's most important fisheries management decisions. Since the 19th century, difficulty calibrating and fitting such models has been used to justify the selection of simple, stationary, single-species models to aid tactical fisheries management decisions. Whereas these justifications are reasonable, it is imperative that we quantify the value of different levels of model complexity for supporting fisheries management, especially given a changing climate, where old methodologies may no longer perform as well as in the past. Here we argue that cost-benefit analysis is an ideal lens to assess the value of model complexity in fisheries management. While some studies have reported the benefits of model complexity in fisheries, modeling costs are rarely considered. In the absence of cost data in the literature, we report, as a starting point, relative costs of single-species stock assessment and marine ecosystem models from two Australian organizations. We found that costs varied by two orders of magnitude, and that ecosystem model costs increased with model complexity. Using these costs, we walk through a hypothetical example of cost-benefit analysis. The demonstration is intended to catalyze the reporting of modeling costs and benefits

Cost–benefit analysis of ecosystem modeling to support fisheries management

Abstract Mathematical and statistical models underlie many of the world's most important fisheries management decisions. Since the 19th century, difficulty calibrating and fitting such models has been used to justify the selection of simple, stationary, single-species models to aid tactical fisheries management decisions. Whereas these justifications are reasonable, it is imperative that we quantify the value of different levels of model complexity for supporting fisheries management, especially given a changing climate, where old methodologies may no longer perform as well as in the past. Here we argue that cost-benefit analysis is an ideal lens to assess the value of model complexity in fisheries management. While some studies have reported the benefits of model complexity in fisheries, modeling costs are rarely considered. In the absence of cost data in the literature, we report, as a starting point, relative costs of single-species stock assessment and marine ecosystem models from two Australian organizations. We found that costs varied by two orders of magnitude, and that ecosystem model costs increased with model complexity. Using these costs, we walk through a hypothetical example of cost-benefit analysis. The demonstration is intended to catalyze the reporting of modeling costs and benefits