DSpace Angular :: Browsing by Author "Navarrete, Sergio A. "

Browsing by Author "Navarrete, Sergio A. "

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A Decade of Death and Other Dynamics: Deepening Perspectives on the Diversity and Distribution of Sea Stars and Wasting
(2023) Dawson, Michael N.; Duffin, Paige J.; Giakoumis, Melina; Schiebelhut, Lauren M.; Beas-Luna, Rodrigo; Bosley, Keith L.; Castilho, Rita; Ewers-Saucedo, Christine; Gavenus, Katie A.; Keller, Aimee; Konar, Brenda; Largier, John L.; Lorda, Julio; Miner, C. Melissa; Moritsch, Monica M.; Navarrete, Sergio A.; Traiger, Sarah B.; Turner, Mo S.; Wares, John P.
Mass mortality events provide valuable insight into biological extremes and also ecological interactions more generally. The sea star wasting epidemic that began in 2013 catalyzed study of the microbiome, genetics, population dynamics, and community ecology of several high-profile species inhabiting the northeastern Pacific but exposed a dearth of information on the diversity, distributions, and impacts of sea star wasting for many lesser-known sea stars and a need for integration across scales. Here, we combine datasets from single-site to coast-wide studies, across time lines from weeks to decades, for 65 species. We evaluated the impacts of abiotic characteristics hypothetically associated with sea star wasting (sea surface temperature, pelagic primary productivity, upwelling wind forcing, wave exposure, freshwater runoff) and species characteristics (depth distribution, developmental mode, diet, habitat, reproductive period). We find that the 2010s sea star wasting outbreak clearly affected a little over a dozen species, primarily intertidal and shallow subtidal taxa, causing instantaneous wasting prevalence rates of 5%-80%. Despite the collapse of some populations within weeks, environmental and species variation protracted the outbreak, which lasted 2-3 years from onset until declining to chronic background rates of similar to 2% sea star wasting prevalence. Recruitment began immediately in many species, and in general, sea star assemblages trended toward recovery; however, recovery was heterogeneous, and a marine heatwave in 2019 raised concerns of a second decline. The abiotic stressors most associated with the 2010s sea star wasting outbreak were elevated sea surface temperature and low wave exposure, as well as freshwater discharge in the north. However, detailed data speaking directly to the biological, ecological, and environmental cause(s) and consequences of the sea star wasting outbreak remain limited in scope, unavoidably retrospective, and perhaps always indeterminate. Redressing this shortfall for the future will require a broad spectrum of monitoring studies not less than the taxonomically broad cross-scale framework we have modeled in this synthesis.
Alteration of coastal productivity and artisanal fisheries interact to affect a marine food web
(2021) Isidora Avila-Thieme, M.; Corcoran, Derek; Perez-Matus, Alejandro; Wieters, Evie A.; Navarrete, Sergio A.; Marquet, Pablo A.; Valdovinos, Fernanda S.
Top-down and bottom-up forces determine ecosystem function and dynamics. Fisheries as a top-down force can shorten and destabilize food webs, while effects driven by climate change can alter the bottom-up forces of primary productivity. We assessed the response of a highly-resolved intertidal food web to these two global change drivers, using network analysis and bioenergetic modelling. We quantified the relative importance of artisanal fisheries as another predator species, and evaluated the independent and combined effects of fisheries and changes in plankton productivity on food web dynamics. The food web was robust to the loss of all harvested species but sensitive to the decline in plankton productivity. Interestingly, fisheries dampened the negative impacts of decreasing plankton productivity on non-harvested species by reducing the predation pressure of harvested consumers on non-harvested resources, and reducing the interspecific competition between harvested and non-harvested basal species. In contrast, the decline in plankton productivity increased the sensitivity of harvested species to fishing by reducing the total productivity of the food web. Our results show that strategies for new scenarios caused by climate change are needed to protect marine ecosystems and the wellbeing of local communities dependent on their resources.
Aphrastura spinicauda change their reproductive strategy with altitude in the Andean temperate forest of South America
(2015) Altamirano, Tomás A.; Ibarra Eliessetch, José Tomás; Maza, Mariano de la; Navarrete, Sergio A.; Bonacic Salas, Cristian
Elevational gradients have been proposed as a driver of change in avian reproductive lifehistory strategies. The eventual shorter breeding season and higher predation risk at highaltitudes can produce a decline in fecundity, a reduction of clutch sizes, and an increase inparental care and survival. We studied whether the breeding strategy of the Aphrasturaspinicauda varies along an elevation gradient in the Andean temperate forests of Chile. Weinstalled 240 nest-boxes between 260 and 1,115 m a.s.l., and monitored the breedingactivity of 162 nests over two seasons (2010-2011, 2011-2012). As predicted, the breedingseason was 28% and 55% shorter in highland forests during the two seasons. Timing of egglaying (1 egg every second day) and incubation period (average 15 days) did not vary withaltitude. We found smaller clutch sizes (average 4.1 vs. 4.5), a fewer number of nestlingsper clutch (average 3.5 vs. 4.2), and longer nestling period (22.2 vs. 21.6 days) in highlandthan lowland forests. The breeding success declined with altitude, mainly due to predationby the Dromiciops gliroides which was 83% in highland and 35% in lowland forests. Ourfindings suggest that Aphrastura spinicauda change their reproductive strategy alongaltitudinal gradients to a slower one, likely as an adaptation to shorter breeding seasons.Yet, these changes do not appear to compensate for the increased predation rates at higherelevations, questioning the potential adaptive significance of this strategy
Beyond tides: surge-dominated submersion regimes on rocky shores of central Chile
(2019) Flores, Gabriela; Cienfuegos, Rodrigo; Navarrete, Sergio A.
By definition, intertidal organisms are exposed to fluctuations between submersion and exposure to air due to the variation in the sea level caused, primarily, by tides and waves. Such submersion regimes have great consequences on the evolution, physiology, behavior, and ecology of intertidal marine organisms, but, paradoxically, our quantitative knowledge about submersion regimes is extremely limited, especially in wave-exposed shores. We here quantify submersion regimes during summer (February 2012) in a wave-exposed rocky shore of central Chile (Las Cruces, 33 degrees 30S, 71 degrees 38W) using a remote sensing method that permits high-frequency measurements. We provide metrics of submersion for the high (barnacle), mid (mussel) and low (upper kelp) intertidal zones and developed statistical models to hindcast submersion regimes from tide and wave data. Results revealed that the submersion consists solely of numerous but brief submersion events produced by waves. The three intertidal zones therefore experience intermittent submersion most of the time, and submersion events are so brief that, in these three zones, emersion predominates over submersion. In this region, submersion cannot be determined from tidal charts, because most of the intertidal zone lies above the highest tidal level, but still the tidal cycle strongly modulates submersion regimes, by altering wave swash into the shore. Combined statistical models including tides and waves are necessary to reproduce the most biologically relevant aspects of submersion. We discuss the consequences of these findings for our understanding of adaptation to intertidal life, and the design of studies on responses to current environmental variability and future climate change.
Easy, fast and reproducible Stochastic Cellular Automata with chouca
(2024) Genin, Alexandre; Dupont, Guillaume; Valencia, Daniel; Zucconi, Mauro; Avila-Thiem, M. Isidora; Navarrete, Sergio A.; Wieters, Evie A.
Stochastic cellular automata (SCA) are models that describe spatial dynamics using a grid of cells that switch between discrete states over time. They are widely used to understand how small-scale processes scale up to affect ecological dynamics at larger spatial scales, and have been applied to a wide diversity of theoretical and applied problems in all systems, such as arid ecosystems, coral reefs, forests, bacteria, or urban growth. Despite their wide applications, SCA implementations are often ad-hoc, lacking performance, guarantees of correctness and poorly reproducible. De novo implementation of SCA for each specific system and application also represents a major barrier for many practitioners. To provide a unifying, well-tested technical basis to this class of models and facilitate their implementation, we built chouca, an R package that translates definitions of SCA models into compiled code, and runs simulations in an efficient way. chouca supports SCA based on rectangular grids where transition probabilities are defined for each cell, with performance typically two to three orders of magnitude above typical implementations in interpreted languages (e.g. R, Python), all while maintaining an intuitive interface in the R environment. Exact and mean-field simulations can be run, and both numerical and graphical results can be easily exported. Besides providing better reproducibility and accessibility, a fast engine for SCA unlocks novel, computationally intensive statistical approaches, such as simulation-based inference of ecological interactions from field data, which represents by itself an important avenue for research. By providing an easy and efficient entry point to SCAs, chouca lowers the bar to the use of this class of models for ecologists, managers and general practitioners, providing a leveled-off reproducible platform while opening novel methodological approaches.
Emergent Spatial Patterns Can Indicate Upcoming Regime Shifts in a Realistic Model of Coral Community
(2024) Genin, Alexandre; Navarrete, Sergio A.; Garcia-Mayor, Angeles; Wieters, Evie A.
Increased stress on coastal ecosystems, such as coral reefs, seagrasses, kelp forests, and other habitats, can make them shift toward degraded, often algae-dominated or barren communities. This has already occurred in many places around the world, calling for new approaches to identify where such regime shifts may be triggered. Theoretical work predicts that the spatial structure of habitat-forming species should exhibit changes prior to regime shifts, such as an increase in spatial autocorrelation. However, extending this theory to marine systems requires theoretical models connecting field-supported ecological mechanisms to data and spatial patterns at relevant scales. To do so, we built a spatially explicit model of subtropical coral communities based on experiments and long-term datasets from Rapa Nui (Easter Island, Chile), to test whether spatial indicators could signal upcoming regime shifts in coral communities. Spatial indicators anticipated degradation of coral communities following increases in frequency of bleaching events or coral mortality. However, they were generally unable to signal shifts that followed herbivore loss, a widespread and well-researched source of degradation, likely because herbivory, despite being critical for the maintenance of corals, had comparatively little effect on their self-organization. Informative trends were found under both equilibrium and nonequilibrium conditions but were determined by the type of direct neighbor interactions between corals, which remain relatively poorly documented. These inconsistencies show that while this approach is promising, its application to marine systems will require detailed information about the type of stressor and filling current gaps in our knowledge of interactions at play in coral communities.
Environmental and demographic factors influence the spatial genetic structure of an intertidal barnacle in central-northern Chile
(2019) Barahona, Mario; Broitman, Bernardo R.; Faugeron, Sylvain; Jaugeon, Lucie; Ospina-Alvarez, Andres; Veliz, David; Navarrete, Sergio A.
Understanding the multiplicity of processes producing genetic patterns in natural populations can shed light on the ecology and evolution of species, and help guide effective management and conservation strategies. Here we investigated the role of environmental, demographic, and geographic factors in shaping the spatial patterns of genetic diversity and differentiation of the intertidal barnacle Notochthamalus scabrosus along the central-northern coast of Chile (28-34 degrees S). We analyzed genetic data from 7 microsatellite loci genotyped for 300 individuals sampled from 10 sites and combined this information with 8 site-specific environmental (4), demographic (2), and geographic (2) variables using least squares linear regressions, generalized linear models, and matrix regression analyses. We found a strong association between the spatially structured genetic diversity of N. scabrosus and patterns of temporal variability in chlorophyll a, and among-site differences in seawater temperature and adult abundance. Our results illustrate that population size, partly driven by recruitment success, can leave a signal on genetic structure of this highly dispersive marine species. The significant effect of temperature and chlorophyll a stresses that local adaptation may be key to understanding the spatial genetic structure of our model species. Hence, the results of this work represent an advance towards understanding the usually complex causal relationships between environmental variables, gene flow, and genetic diversity patterns of coastal populations.
Environmental DNA reveals temporal variation in mesophotic reefs of the Humboldt upwelling ecosystems of central Chile: Toward a baseline for biodiversity monitoring of unexplored marine habitats
(2024) Saenz-Agudelo, Pablo; Ramirez, Paula; Beldade, Ricardo; Campoy, Ana N.; Garmendia, Vladimir; Search, Francesca V.; Fernandez, Miriam; Wieters, Evie A.; Navarrete, Sergio A.; Landaeta, Mauricio F.; Perez-Matus, Alejandro
Temperate mesophotic reef ecosystems (TMREs) are among the least known marine habitats. Information on their diversity and ecology is geographically and temporally scarce, especially in highly productive large upwelling ecosystems. Lack of information remains an obstacle to understanding the importance of TMREs as habitats, biodiversity reservoirs and their connections with better-studied shallow reefs. Here, we use environmental DNA (eDNA) from water samples to characterize the community composition of TMREs on the central Chilean coast, generating the first baseline for monitoring the biodiversity of these habitats. We analyzed samples from two depths (30 and 60 m) over four seasons (spring, summer, autumn, and winter) and at two locations approximately 16 km apart. We used a panel of three metabarcodes, two that target all eukaryotes (18S rRNA and mitochondrial COI) and one specifically targeting fishes (16S rRNA). All panels combined encompassed eDNA assigned to 42 phyla, 90 classes, 237 orders, and 402 families. The highest family richness was found for the phyla Arthropoda, Bacillariophyta, and Chordata. Overall, family richness was similar between depths but decreased during summer, a pattern consistent at both locations. Our results indicate that the structure (composition) of the mesophotic communities varied predominantly with seasons. We analyzed further the better-resolved fish assemblage and compared eDNA with other visual methods at the same locations and depths. We recovered eDNA from 19 genera of fish, six of these have also been observed on towed underwater videos, while 13 were unique to eDNA. We discuss the potential drivers of seasonal differences in community composition and richness. Our results suggest that eDNA can provide valuable insights for monitoring TMRE communities but highlight the necessity of completing reference DNA databases available for this region.
Environmental variability and larval supply to wild and cultured shellfish populations
(2022) Broitman, Bernardo R.; Lara, Carlos; Flores, Raul P.; Saldias, Gonzalo S.; Pinones, Andrea; Pinochet, Andre; Mejia, Alexander Galan; Navarrete, Sergio A.
Coastal upwelling ecosystems support some of the most productive fisheries of the planet together with a large shellfish aquaculture sector that depends on oceanographic processes to deliver planktonic larvae to replenish and feed the farmed stock. Coastal shellfish aquaculture operations in Chile and Peru have experienced large interannual fluctuations in larval supply over the past decade, yet the drivers of such variability remain unidentified. We focused on the effects of environmental variability on larval supply of the farmed Peruvian bay scallop Argopecten purpuratus in a bay in northern Chile (Tongoy Bay, 30 circle S) that accounts for over 90% of countrywide landings. We examined the hypothesis that the environmental processes governing larval supply were shared with wild benthic invertebrates with planktonic larval development and compared time series of larval abundance for the scallop with larval supply rates to benthic populations of two well-studied wild intertidal species: the Chthamalid barnacle Jehlius cirratus and the purple mussel Perumytilus purpuratus. To this end, we examined the cross-correlation of larval supply to environmental variability using MODIS satellite fields of sea surface temperature (SST) chlorophyll-a concentration (chl-a) and fluorescence line height (nFLH), together with three climate indices relevant for the south east Pacific sector: the Southern Oscillation index (SOI), the Pacific Decadal Oscillation (PDO) and the Antarctic Oscillation Index (AAO). Our results showed that over the five-year study period (2009-2013), patterns of larval supply to the scallop population were related to interannual variability in the environmental processes as captured by their Empirical Orthogonal Functions (EOFs), likely to adult condition before spawning. Surprisingly, larval supply for none of the wild species showed a clear association to the EOFs. In contrast, scallops and wild species showed significant association to lower frequency climate variability as captured by the SOI and the PDO, but not the AAO. Results suggest that larval supply patterns to Tongoy Bay may be modulated by regional patterns of climatic variability, particularly of tropical origin. Thus, changes in coastal oceanography associated with ongoing changes in global climate could have strong and lasting effects on the supply of seedstock for wild and cultivated species across this eastern boundary coastal system and argue for the establishment of long-term ocean observing and early warning systems along the region.
Geographic variation in diversity of wave exposed rocky intertidal communities along central Chile
(2011) Broitman, Bernardo R.; Veliz, Fredy; Manzur, Tatiana; Wieters, Evie A.; Randall Finke, G.; Fornes, Paulina A.; Valdivia, Nelson; Navarrete, Sergio A.
Along the coast of central Chile, geographic trends of diversity have been inferred from literature compilations and museum collections based on species range limits for some taxonomic groups. However, spatially-intensive field-based assessments of macrobenthic species richness are largely missing. Over the course of a multiyear study (1998-2005), we characterized latitudinal patterns of rocky intertidal diversity at 18 sites along the coast of central Chile (29-36 degrees S). At each site, the number of sessile and mobile macrobenthic species was quantified in 0.25 m(2) quadrats. Two estimators of local (alpha) diversity were used: observed local species richness, calculated from the asymptote of a species-rarefaction curve, and the Chao2 index, which takes into account the effect of rare species on estimates of local richness. We identified a total of 71 species belonging to 66 genera for a total of 86 taxa. The most diverse groups were herbivorous mollusks (27 taxa) and macroalgae (43 taxa). Diversity showed a complex spatial pattern with areas of high species richness interspersed with areas of low richness. In accordance with previous work, we found no trend in the number of herbivorous mollusks and an inverse and significant latitudinal gradient in the number of algal species. Our results highlight the need for taxonomically diverse assessments of biodiversity of the dominant taxa that conform intertidal communities.
Historias de vida en la cordillera: el rayadito (Aphrastura spinicauda) cambia su estrategia reproductiva en un gradiente altitudinal en el bosque templado andino
(2014) Altamirano Oyarzún, Tomás Alberto; De la Maza, Mariano; Ibarra Eliessetch, José Tomás; Navarrete, Sergio A.; Bonacic Salas, Cristian
Los gradientes altitudinales han sido propuestos como impulsores de cambio en laestrategia reproductiva de las aves. Las características ambientales asociadas con zonas demayor altitud generalmente inducen un cambio hacia estrategias reproductivas “lentas”. Específicamente, la eventual temporada reproductiva más corta y el mayor riesgo dedepredación en zonas altas, pueden producir una declinación en la fecundidad, reducción enlos tamaños de puesta y un incremento en el cuidado parental y sobrevivencia. Estudiamos la estrategia reproductiva del Rayadito (Aphrastura spinicauda) varía a lo largo de ungradiente altitudinal en el bosque templado andino de Chile. Instalamos 240 cajas-nidoentre los 260 y 1.115 m.s.n.m., y monitoreamos la actividad reproductiva en 162 nidosdurante dos temporadas reproductivas (2010-2011, 2011-2012). La temporada reproductivafue un 28% y un 55% más corta en bosques de zonas altas (> 700 m) durante las dostemporadas. El pulso de puesta (1 huevo cada dos días) y el periodo de incubación (15 días)no variaron con la altitud. El tamaño de puesta fue entre tres y cinco en bosques de zonasaltas y entre dos y siete en bosques de zonas bajas (< 700 m). El tamaño de puesta (4,1 vs.4,5) y el número de crías (promedio 3,5 vs. 4,2) fueron significativamente más pequeños, yel periodo de cría (22,2 vs. 21,6 días) fue significativamente más largo, en bosques dezonas altas más que en bosques de zonas bajas. El éxito reproductivo declinó con la altitud, principalmente debido a la depredación de nidos por el monito del monte (Dromiciops gliroides). Un 83% de los nidos en bosques de zonas altas y 35% en bosques de zonas bajasfueron depredados. Nuestros resultados sugieren que el rayadito cambia su estrategiareproductiva a lo largo de gradientes altitudinales, probablemente como adaptación atemporadas reproductivas más cortas
Influence of larval traits on dispersal and connectivity patterns of two exploited marine invertebrates in central Chile
(2019) Blanco, Marta; Ospina-Alvarez, Andres; Navarrete, Sergio A.; Fernandez, Miriam
Environmental variability can influence larval development rates and affect critical processes in the dynamics of natural populations, such as dispersal distances and connectivity, when modulated by different larval traits. Knowledge of connectivity patterns in marine populations is fundamental for defining population viability and progressing with management and conservation goals. Here, we developed a biophysical, individual-based larval dispersal model to assess the effect of oceanographic variability and biological traits (i.e. larval diel vertical migration [DVM] and temperature-dependent larval development [PLD]) on recruitment success, dispersal distance, and alongshore connectivity patterns. We selected 2 species exploited by Chilean artisanal fisheries: Loxechinus albus (PLD: 20 d) and Fissurella latimarginata (PLD: 5 d). A sensitivity analysis was used to examine the effect of intrinsic (DVM and PLD) and extrinsic (release depth, latitude, and timing) processes. Release location and timing of release explained respectively 24.30 and 5.54% (F. latimarginata) and 34.8 and 4.19% (L. albus) of the variability observed in recruitment success, and 23.80 and 6.94% (F. latimarginata) and 26.10 and 19.60% (L. albus) of the variability observed in dispersal distance. Most recruitment to local populations was allochthonous, presenting low levels of self-recruitment and local retention, including species with short PLD. Similar geographic patterns of source and destination strengths were observed in both species, showing a geographic mosaic of source and sink populations with relatively higher importance towards the northern region of the study area. Our findings allow us to identify primary determinants of recruitment success and dispersal distance for 2 important exploited species in Chile.
Integration of biophysical connectivity in the spatial optimization of coastal ecosystem services
(ELSEVIER, 2020) Ospina Alvarez, Andres; de Juan, Silvia; Davis, Katrina J.; Gonzalez, Catherine; Fernandez, Miriam; Navarrete, Sergio A.
Ecological connectivity in coastal oceanic waters is mediated by dispersion of the early life stages of marine organisms and conditions the structure of biological communities and the provision of ecosystem services. Integrated management strategies aimed at ensuring long-term service provision to society do not currently consider the importance of dispersal and larval connectivity. A spatial optimization model is introduced to maximise the potential provision of ecosystem services in coastal areas by accounting for the role of dispersal and larval connectivity. The approach combines a validated coastal circulation model that reproduces realistic patterns of larval transport along the coast, which ultimately conditions the biological connectivity and productivity of an area, with additional spatial layers describing potential ecosystem services. The spatial optimization exercise was tested along the coast of Central Chile, a highly productive area dominated by the Humboldt Current. Results show it is unnecessary to relocate existing management areas, as increasing no-take areas by 10% could maximise ecosystem service provision, while improving the spatial representativeness of protected areas and minimizing social conflicts. The location of protected areas was underrepresented in some sections of the study domain. principally due to the restriction of the model to rocky subtidal habitats. Future model developments should encompass the diversity of coastal ecosystems and human activities to inform integrative spatial management. Nevertheless, the spatial optimization model is innovative not only for its integrated ecosystem perspective, but also because it demonstrates that it is possible to incorporate time-varying biophysical connectivity within the optimization problem, thereby linking the dynamics of exploited populations produced by the spatial management regime. (C) 2020 Elsevier B.V. All rights reserved.
Long-term monitoring of coastal ecosystems at Las Cruces, Chile: Defining baselines to build ecological literacy in a world of change
(2010) Navarrete, Sergio A.; Gelcich, Stefan; Castilla, Juan C.
Marine coastal habitats are being increasingly impacted by human activities. In addition, there are dramatic climatic disruptions that could generate important and irreversible shifts in coastal ecosystems. Long-term monitoring plays a fundamental and irreplaceable role to establish general baselines from which we can better address current and future impacts and distinguish between natural and anthropogenic changes and fluctuations. Here we highlight how over 25 years of monitoring the coastal marine ecosystem within the no-take marine protected area of Las Cruces has provided critical information to understand ecological baselines and build the necessary ecological literacy for marine management and conservation. We argue that this understanding can only be gained with simultaneous monitoring of reserves and human-impacted areas, and the development of complementary experimental studies that test alternative hypothesis about driving processes and mechanisms. In this contribution we selected four examples to illustrate long-term temporal fluctuations at all trophic levels including taxa from algae to sea birds. From these examples we draw a few general lessons: a) there is co-occurrence of rapid- and slowly- unfolding ecological responses to the exclusion of humans within the same rocky shore community. The sharp differences in the pace at which depleted populations recover is at least partly related to differences in life history (dispersal capabilities) of the targeted species. b) Long-term monitoring of the supply-side of marine communities is critical to evaluate the potential feedback effects of local changes in abundance into the arrival of new individuals and to correctly evaluate environmental and human-induced perturbations. c) Unexpected changes in local population dynamics can occur in "independent" and apparently non-interactive modules of the marine ecosystem, such as roosting sea birds inside the reserve. In addition we discuss the way in which ecological data generated from long-term monitoring at marine reserves was institutionalized in a national marine management policy. At the same time, we highlight the mismatch between the gained scientific information and principles from these studies and the current concept of marine protected areas that is being implemented by some government agencies in Chile. Information from long term monitoring programs has proved essential to understand how marine environments respond to anthropogenic and/or natural disturbances, however funding these schemes, which generally have no short term gains for funding agencies in both developing and developed countries, still remain a major challenge.
Monitoring the fabric of nature: using allometric trophic network models and observations to assess policy effects on biodiversity
(2023) Navarrete, Sergio A.; Avila-Thieme, M. Isidora; Valencia, Daniel; Genin, Alexandre; Gelcich, Stefan
Species diversity underpins all ecosystem services that support life. Despite this recognition and the great advances in detecting biodiversity, exactly how many and which species co-occur and interact, directly or indirectly in any ecosystem is unknown. Biodiversity accounts are incomplete; taxonomically, size, habitat, mobility or rarity biased. In the ocean, the provisioning of fish, invertebrates and algae is a fundamental ecosystem service. This extracted biomass depends on a myriad of microscopic and macroscopic organisms that make up the fabric of nature and which are affected by management actions. Monitoring them all and attributing changes to management policies is daunting. Here we propose that dynamic quantitative models of species interactions can be used to link management policy and compliance with complex ecological networks. This allows managers to qualitatively identify 'interaction-indicator' species, which are highly impacted by management policies through propagation of complex ecological interactions. We ground the approach in intertidal kelp harvesting in Chile and fishers' compliance with policies. Results allow us to identify sets of species that respond to management policy and/or compliance, but which are often not included in standardized monitoring. The proposed approach aids in the design of biodiversity programmes that attempt to connect management with biodiversity change.This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'.
Morphological and Molecular Identification of Ulva spp. (Ulvophyceae; Chlorophyta) from Algarrobo Bay, Chile: Understanding the Composition of Green Tides
(2024) Mutizabal-Aros, Javiera; Ramirez, Maria Eliana; Haye, Pilar A.; Meynard, Andres; Pinilla-Rojas, Benjamin; Nunez, Alejandra; Latorre-Padilla, Nicolas; Search, Francesca V.; Tapia, Fabian J.; Saldias, Gonzalo S.; Navarrete, Sergio A.; Contreras-Porcia, Loretto
Green algae blooms of the genus Ulva are occurring globally and are primarily attributed to anthropogenic factors. At Los Tubos beach in Algarrobo Bay along the central Chilean coast, there have been blooms of these algae that persist almost year-round over the past 20 years, leading to environmental, economic, and social issues that affect the local government and communities. The objective of this study was to characterize the species that form these green tides based on a combination of ecological, morpho-anatomical, and molecular information. For this purpose, seasonal surveys of beached algal fronds were conducted between 2021 and 2022. Subsequently, the sampled algae were analyzed morphologically and phylogenetically using the molecular markers ITS1 and tufA, allowing for the identification of at least five taxa. Of these five taxa, three (U. stenophylloides, U. uncialis, U. australis) have laminar, foliose, and distromatic morphology, while the other two (U. compressa, U. aragoensis) have tubular, filamentous, and monostromatic fronds. Intertidal surveys showed that U. stenophylloides showed the highest relative coverage throughout the seasons and all intertidal levels, followed by U. uncialis. Therefore, we can establish that the green tides on the coast of Algarrobo in Chile are multispecific, with differences in relative abundance during different seasons and across the intertidal zone, opening opportunities for diverse future studies, ranging from ecology to algal biotechnology.
Oceanographical-driven dispersal and environmental variation explain genetic structure in an upwelling coastal ecosystem
(2024) Peluso, Livia; Faundez, Juan; Navarrete, Sergio A.; Broitman, Bernardo R.; Aiken, Christopher M.; Saenz-Agudelo, Pablo
The seascape comprises multiple environmental variables that interact with species biology to determine patterns of spatial genetic variation. The environment imposes spatially variable selective forces together with homogenizing and diverging drivers that facilitate or restrict dispersal, which is a complex, time-dependent process. Understanding how the seascape influences spatial patterns of genetic variation remains elusive, particularly in coastal upwelling systems. Here, we combine genome-wide SNP data, Lagrangian larval dispersal simulated over a hydrodynamic model, and ocean environmental information to quantify the relative contribution of ocean circulation and environmental heterogeneity as drivers of the spatial genetic structure of two congeneric intertidal limpets, Scurria scurra and S. araucana, along the central coast of Chile. We find that a genetic break observed in both limpet species coincides with a break in connectivity shown by the Lagrangian dispersal, suggesting that mean ocean circulation is an important seascape feature, in particular for S. scurra. For S. araucana, environmental variation appears as a better predictor of genetic structure than ocean circulation. Overall, our study shows broad patterns of seascape forcing on genetic diversity and contributes to our understanding of the complex ecological and evolutionary interactions along coastal upwelling systems.
Ontogenetic changes in habitat use and diet of the sea-star Heliaster helianthus on the coast of central Chile
(2010) Manzur, Tatiana; Barahona, Mario; Navarrete, Sergio A.
Ontogenetic shifts in habitat use and diet are ubiquitous in nature and usually have profound consequences for the ecology and evolution of the species. In the case of species with strong interactions within their communities, such as keystone predators, understanding this kind of size-related change is critical to understand variation and connectivity among spatially distinct habitats of coastal communities. Yet the ecology of early life stages of marine benthic invertebrates, particularly asteroids, is poorly understood. Here we describe the results of surveys to characterize the habitat and quantify the abundance and diet of recruits of the sun star Heliaster helianthus, a keystone predator at rocky intertidal sites in central Chile. Our results support the existence of size-related, ontogenetic changes in habitat use and diet of this species. Recruits occupy boulders and crevices in the high or mid-high intertidal zones of wave-protected habitats and as they grow they move down towards lower tidal levels. Adults are characteristically found in the low intertidal zone of wave exposed and semi-exposed habitats. These changes in habitat use are accompanied by changes in diet composition and particularly by a broadening of the prey species incorporated in the diet. Since early stages of Heliaster appear to be most sensitive to predation and abiotic stress and since adults are such important predators in wave exposed rocky shores, knowledge of the basic ecology of early stages of this species is critical to fully understand the dynamics of intertidal communities.
Phenotypic variability in byssus thread production of intertidal mussels induced by predators with different feeding strategies
(INTER-RESEARCH, 2008) Caro, Andres U.; Escobar, Joan; Bozinovic, Francisco; Navarrete, Sergio A.; Castilla, Juan Carlos
Predator-induced defenses have a significant influence on the expression of morphological and behavioral traits of marine species. In mussels, common responses to predators include thickening of the shell, enlargement of the adductor muscle and increases in byssus production. We hypothesize that predators with different feeding strategies have different effects on byssus production of the common intertidal mussels Perumytilus purpuratus and Semimytilus algosus in central Chile, Predators that dislodge prey mussels before killing them, such as crabs and seastars, should elicit increased byssus production in their prey compared to other predators such as whelks, which use different feeding mechanisms. Laboratory experiments with the seastar Heliaster helianthus, the crab Acanthocylus gayi, and the muricid gastropods Concholepas concholepas and Acanthina monodon showed that: only A. gayi induced significant increases in byssus production, causing remarkably similar responses in both mussel species. Further experiments in which individual mussels with different: attachment strengths were offered to A. gayi showed that the crabs first tried different mussels and then selected those with the weakest attachment, leading to consumption rates of weakly attached mussels that were 5 to 6 times higher than those of mussels with strong attachment to the substratum. Measurements of mussel attachment: strengths in the field showed that, where A. gayi is abundant, both mussel species are more strongly attached than in habitats where this predator is scarce. While responses of mussels to crabs seem to be adaptive, the lack of a response to H. helianthus is intriguing, because it is one of the most important. mussel predators in the system which can dislodge entire Clumps Of Mussels at a time. It is possible that increased byssus production is ineffective in reducing predation by this large predator; however, this adaptive explanation requires further studies. These results highlight the predator-specific nature of many prey phenotypic responses and the importance of considering the multiplicity of predators typically present in most habitats.
Predator control of marine communities increases with temperature across 115 degrees of latitude
(2022) Ashton, Gail, V; Freestone, Amy L.; Duffy, J. Emmett; Torchin, Mark E.; Sewall, Brent J.; Tracy, Brianna; Albano, Mariano; Altieri, Andrew H.; Altvater, Luciana; Bastida-Zavala, Rolando; Bortolus, Alejandro; Brante, Antonio; Bravo, Viviana; Brown, Norah; Buschmann, Alejandro H.; Buskey, Edward; Calderon Barrera, Rosita; Cheng, Brian; Collin, Rachel; Coutinho, Ricardo; De Gracia, Luis; Dias, Gustavo M.; DiBacco, Claudio; Flores, Augusto A., V; Angelica Haddad, Maria; Hoffman, Zvi; Ibanez Erquiaga, Bruno; Janiak, Dean; Jimenez Campean, Anali; Keith, Inti; Leclerc, Jean-Charles; Pedro Lecompte-Perez, Orlando; Ortigara Longo, Guilherme; Matthews-Cascon, Helena; McKenzie, Cynthia H.; Miller, Jessica; Munizaga, Martin; Naval-Xavier, Lais P. D.; Navarrete, Sergio A.; Otalora, Carlos; Palomino-Alvarez, Lilian A.; Gabriela Palomo, Maria; Patrick, Chris; Pegau, Cormack; Pereda, Sandra, V; Rocha, Rosana M.; Rumbold, Carlos; Sanchez, Carlos; Sanjuan-Munoz, Adolfo; Schloder, Carmen; Schwindt, Evangelina; Seemann, Janina; Shanks, Alan; Simoes, Nuno; Skinner, Luis; Yolimar Suarez-Mozo, Nancy; Thiel, Martin; Valdivia, Nelson; Velez-Zuazo, Ximena; Vieira, Edson A.; Vildoso, Bruno; Wehrtmann, Ingo S.; Whalen, Matt; Wilbur, Lynn; Ruiz, Gregory M.
Early naturalists suggested that predation intensity increases toward the tropics, affecting fundamental ecological and evolutionary processes by latitude, but empirical support is still limited. Several studies have measured consumption rates across latitude at large scales, with variable results. Moreover, how predation affects prey community composition at such geographic scales remains unknown. Using standardized experiments that spanned 115 degrees of latitude, at 36 nearshore sites along both coasts of the Americas, we found that marine predators have both higher consumption rates and consistently stronger impacts on biomass and species composition of marine invertebrate communities in warmer tropical waters, likely owing to fish predators. Our results provide robust support for a temperature-dependent gradient in interaction strength and have potential implications for how marine ecosystems will respond to ocean warming.

Browsing by Author "Navarrete, Sergio A. "

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