Sergio Navarrete - Academia.edu (original) (raw)

Papers by Sergio Navarrete

Over the past decades, our understanding of the vital role microbes play in ecosystem processes h... more Over the past decades, our understanding of the vital role microbes play in ecosystem processes has greatly expanded. However, we still have limited knowledge about how microbial communities interact with larger organisms. Many existing representations of microbial interactions are based on co-occurrence patterns, which do not provide clear insights into trophic or non-trophic relationships. In this study, we untangled trophic and non-trophic interactions between macroscopic and microscopic organisms on a marine rocky shore. Five abundant mollusk grazers were selected, and their consumptive (grazing) and non-consumptive (grazer pedal mucus) interactions with bacteria in biofilms were measured using 16S rRNA amplicon sequencing. While no significant effects on a commonly used measure of biofilm grazing (Chlorophyll-a concentration) were observed, detailed image analysis revealed that all grazers had a detrimental impact on biofilm cover. Moreover, different grazers exhibited distinct...

Ecology, 2018

Co‐occurrence methods are increasingly utilized in ecology to infer networks of species interacti... more Co‐occurrence methods are increasingly utilized in ecology to infer networks of species interactions where detailed knowledge based on empirical studies is difficult to obtain. Their use is particularly common, but not restricted to, microbial networks constructed from metagenomic analyses. In this study, we test the efficacy of this procedure by comparing an inferred network constructed using spatially intensive co‐occurrence data from the rocky intertidal zone in central Chile to a well‐resolved, empirically based, species interaction network from the same region. We evaluated the overlap in the information provided by each network and the extent to which there is a bias for co‐occurrence data to better detect known trophic or non‐trophic, positive or negative interactions. We found a poor correspondence between the co‐occurrence network and the known species interactions with overall sensitivity (probability of true link detection) equal to 0.469, and specificity (true non‐intera...

Journal of Marine Science and Engineering

Current advances in wave energy technologies have enabled the development of new integrated measu... more Current advances in wave energy technologies have enabled the development of new integrated measurement platforms powered by the energy of wave motion. Instrumentation is now being deployed for the long-term observation of the coastal ocean, with the objectives of analyzing the performance of wave energy converters (WECs) and studying their interactions with the surrounding environment and marine life. In this work, we present the most relevant findings of the installation and initial operation of the Open Sea Lab (OSL), the first coastal observatory in Latin America powered entirely by a WEC device. We evaluated the preliminary data regarding the combined operation of the system, the generation of energy, and the observations obtained by the continuous monitoring of physical variables at the site. The data showed the seasonal variability of the energy produced by the WEC for a range of wave heights during the period of observation. We also investigated the rapid development of biof...

Limnology and Oceanography: Methods, 2016

The importance of the submersion regime for the physiology, behavior and ecology of intertidal or... more The importance of the submersion regime for the physiology, behavior and ecology of intertidal organisms, as well as limitations of available measurement methods, motivated us to develop a new remote sensing method. This new method is based on video monitoring of visual references installed at interest positions in the intertidal zone. Video imagery processing algorithms discriminate between states of submersion and emersion. The signal is based on the fluctuation in the color contrast between the visual reference and the adjacent rock. Our remote sensing method was validated favorably by comparing with direct field observations of submersion time series and comparison of different submersion metrics, including submersion percentage and maximum emersion duration. Since the remote sensing method captures and stores imagery remotely, obtaining long records of high temporal resolution is facilitated and the risk of discontinuity of time series is reduced in comparison to the use of sensors at the zone of wave impact. The high temporal resolution is critical for environments with high exposure to waves and allows for reliable estimates of a wide variety of relevant submersion metrics. This low cost remote sensing method should encourage quantification of submersion regimes of organisms inhabiting rocky intertidal zones, as well as the exploration of physiological, behavioral and ecological consequences of these regimes. Identifying the character of the forces underlying submersion regimes, together with critical environmental variables, such as temperature and solar radiation, will allow better hind-casts and forecasts of the ecological consequences of past and future climate change on these communities.

Marine Ecology Progress Series, 2011

In consumer assemblages, the organization of individual foraging behavior, as well as spatial dis... more In consumer assemblages, the organization of individual foraging behavior, as well as spatial distribution, can largely determine environmental risks, and the intensity of intra-and interspecific interactions. We characterized distributional and behavioral patterns of the most common benthic grazers coexisting in the rocky shores of central Chile: the chiton Chiton granosus, the pulmonate limpet Siphonaria lessoni, the scurrinid limpet Scurria araucana and the keyhole limpet Fissurella crassa. C. granosus and F. crassa were strictly nocturnal foragers whereas S. lessoni foraged during daytime. Most S. araucana individuals foraged at night, but daytime foraging was also common. The spatial distribution at resting varied from aggregated for C. granosus and S. lessoni to a more dispersive pattern for F. crassa and S. araucana. C. granosus dispersed slightly from aggregation when foraging whereas S. lessoni foraged in tight conspecific aggregations. Foraging excursions varied from over 60 cm in F. crassa to less than 7 cm in S. araucana. Homing behavior ranged from extreme fidelity in F. crassa to low fidelity in S. lessoni. Positive associations were observed between C. granosus and F. crassa during resting and foraging whereas negative associations were observed between these species and S. lessoni. These general patterns varied little between 2 sites separated by a few kilometers. Interspecific competition might be important in structuring this guild, but it may affect only some species pairs. Direct interference in the use of shelter or while foraging, rather than food exploitation, seems the most likely mechanism. The marked differences in individual behavior among species, despite ample diet overlap, might translate into different functional effects, which should be explored in future experiments.

Proceedings of the Royal Society B: Biological Sciences, 2022

Climate change has led to intensification and poleward migration of the Southeastern Pacific Anti... more Climate change has led to intensification and poleward migration of the Southeastern Pacific Anticyclone, forcing diverging regions of increasing, equatorward and decreasing, poleward coastal phytoplankton productivity along the Humboldt Upwelling Ecosystem, and a transition zone around 31° S. Using a 20-year dataset of barnacle larval recruitment and adult abundances, we show that striking increases in larval arrival have occurred since 1999 in the region of higher productivity, while slower but significantly negative trends dominate poleward of 30° S, where years of recruitment failure are now common. Rapid increases in benthic adults result from fast recruitment–stock feedbacks following increased recruitment. Slower population declines in the decreased productivity region may result from aging but still reproducing adults that provide temporary insurance against population collapses. Thus, in this region of the ocean where surface waters have been cooling down, climate change is...

Journal of Marine Science and Engineering, 2021

Maritime enterprises have long sought solutions to reduce the negative consequences of the settle... more Maritime enterprises have long sought solutions to reduce the negative consequences of the settlement and growth of marine biofouling (micro- and macro-organisms) on virtually all surfaces and materials deployed at sea. The development of biofouling control strategies requires solutions that are cost-effective and environmentally friendly. Polymer-based coatings, such as the poly (3,4-ethylenedioxythiophene) (PEDOT) and its potential applications, have blossomed over the last decade thanks to their low cost, nontoxicity, and high versatility. Here, using multiple-choice larval settlement experiments, we assessed the efficacy of PEDOT against the balanoid barnacle Notobalanus flosculus one of the most common biofouling species in Southeastern Pacific shores, and compared results against a commercially available antifouling (AF) coating, and biofilms at different stages of succession (1, 2, 4 and 8 weeks). We show that larval settlement on PEDOT-coated surfaces was similar to the sett...

Ecology, 2020

Understanding the drivers of geographical variation in species distributions, and the resulting c... more Understanding the drivers of geographical variation in species distributions, and the resulting community structure, constitutes one of the grandest challenges in ecology. Geographical patterns of species richness and composition have been relatively well studied. Less is known about how the entire set of trophic and non-trophic ecological interactions, and the complex networks that they create by gluing species together in complex communities, change across geographical extents. Here, we compiled data of species composition and three types of ecological interactions occurring between species in rocky intertidal communities across a large spatial extent (~970 km of shoreline) of central Chile, and analyzed the geographical variability in these multiplex networks (i.e., comprising several interaction types) of ecological interactions. We calculated nine network summary statistics common across interaction types, and additional network attributes specific to each of the different types of interactions. We then investigated potential environmental drivers of this multivariate network organization. These included variation in sea surface temperature and coastal upwelling, the main drivers of productivity in nearshore waters. Our results suggest that structural properties of multiplex ecological networks are affected by local species richness and modulated by factors influencing productivity and environmental predictability. Our results show that non-trophic negative interactions are more sensitive to spatially structured temporal environmental variation than feeding relationships, with non-trophic positive interactions being the least labile to it. We also show that environmental effects are partly mediated through changes in species richness and partly through direct influences on species interactions, probably associated to changes in environmental predictability and to bottom-up nutrient availability. Our findings highlight the need for a comprehensive picture of ecological interactions and their geographical variability if we are to predict potential effects of environmental changes on ecological communities.

The American Naturalist, 2008

Striking differences in the dispersal of coexisting species have fascinated marine ecologists for... more Striking differences in the dispersal of coexisting species have fascinated marine ecologists for decades. Despite widespread attention to the impact of dispersal on individual species dynamics, its role in species interactions has received comparatively little attention. Here, we approach the issue by combining analyses of simple heuristic predator-prey models with different dispersal patterns and data from several predator-prey systems from the Pacific coasts of North and South America. In agreement with model predictions, differences in predator dispersal generated characteristic biogeographic patterns. Predators lacking pelagic larvae tracked geographic variation in prey recruitment but not prey abundance. Prey recruitment rate alone explained more than 80% of the biogeographic variation in predator abundance. In contrast, predators with broadcasting larvae were uncorrelated with prey recruitment or adult prey abundance. Our findings reconcile perplexing results from previous studies and suggest that simple models can capture some of the complexity of life-history diversity in marine communities.

Revista chilena de historia natural, 2000

Marine Ecology Progress Series, 2001

We conducted field surveys of rocky intertidal communities at 18 sites distributed between 29°S a... more We conducted field surveys of rocky intertidal communities at 18 sites distributed between 29°S and 36°S on the coast of central Chile in order to document broad patterns of functional and trophic group abundance and evaluate their association with oceanographic features. Results showed that the main sessile components of the landscape throughout the region were kelps (16%) and crustose algae (48%) in the low intertidal zone, while mussels beds (30%) and corticated algae (32%) dominated the mid-intertidal zone. Geographic trends in abundance across the entire region varied from no clear regional patterns for some groups (e.g. barnacles), to smooth gradients increasing or decreasing toward higher latitudes for others (kelps and ephemeral algae) and to an abrupt switch from dominant to scarce northward of 32°S in 1 group (mussels). Significant among-site negative correlations were detected between the abundances of most algal functional groups and between mussels and barnacles. Herbivore density was negatively correlated with kelp and corticated algal cover, and positively correlated with crustose algal abundance. These correlations reinforce the notion that local biological interactions can partially account for the among-site variability in functional group abundance. We assessed the influence of mesoscale oceanographic features through satellite image analyses, by classifying the study sites as either strongly or weakly influenced by coastal upwelling. At sites strongly influenced by upwelling, we found significantly higher cover of kelps in the low intertidal zone and of corticated algae in the mid-intertidal zone. Cover of ephemeral algae in the mid-intertidal zone was significantly lower at sites strongly affected by upwelling. Contrary to predictions of bottom-up community regulation models, we found no significant differences in abundance of sessile filter feeders (mussels or barnacles), herbivores or carnivores. A significant proportion of the regional variation in abundance in some of the most abundant functional groups within each tidal level was associated with the latitudinal gradient in annual mean sea surface temperature (SST). We detected a significant correlation between SST and the abundance of kelps and crustose algae in the low intertidal zone, and mussels and ephemeral algae in the mid-intertidal zone. The abrupt change in the abundance of mussels in the mid-intertidal zone at about 32°S may indicate a similarly abrupt change in biological or environmental conditions. Lack of significant correlation between the abundance of mussels and other functional groups suggests that biological interactions may not be responsible for this geographic discontinuity. We suggest that oceanography may be largely involved in the geographic variability detected in patterns of community structure. Recent remote sensing studies documenting oceanographic discontinuities around the 32°S zone support our suggestion. Our results highlight the need for further experimental and oceanographic studies in areas where strong biophysical gradients are observed. Such areas may well reflect the existence of steep oceanographic gradients sensitive to large-scale environmental forcing.

Marine Ecology Progress Series, 2007

Recruitment is among the processes that most directly influence spatio-temporal patterns of abund... more Recruitment is among the processes that most directly influence spatio-temporal patterns of abundance, productivity, and persistence in marine populations. Understanding the connection between patterns of recruitment and environmental forcing has major implications for the conservation and management of marine ecosystems. Theoretical and empirical studies have shown that dispersal and regional variability in environmental conditions may synchronize distant populations and generate patterns of spatial synchrony (i.e. decay in synchrony with distance). Here, we submit that recruitment synchrony patterns may be used to identify processes shaping the distribution of marine populations. We used artificial substrates to estimate patterns of spatial synchrony in recruitment for 15 intertidal invertebrates at 16 exposed rocky platforms spanning 120 km of the central coast of Chile. Clear and significant synchrony patterns were found for only 4 species: the barnacles Jehlius cirratus, Notochthamalus scabrosus, and Notobalanus flosculus, and the bivalve Perumytilus purpuratus, all of which occur at comparatively high abundance across the study region. The strength of synchrony decayed with distance, from positively correlated fluctuations for sites separated by < 30 km, to negatively correlated for sites > 40 km apart. Patterns of spatial synchrony in recruitment resembled those of fluctuations in sea surface temperature, suggesting that mesoscale processes such as coastal upwelling may shape recruitment patterns by way of modulating larval dispersal. A lack of clear synchrony patterns in the remaining species could be ascribed to their low abundance, or, for those with potentially limited larval dispersal (e.g. direct development), it could indicate our lack of adequate spatio-temporal resolution to detect recruitment variability at small scales.

Marine Ecology Progress Series, 2002

In this study we assessed the impact of the spatial scale of analysis on patterns of latitudinal ... more In this study we assessed the impact of the spatial scale of analysis on patterns of latitudinal diversity of rocky intertidal invertebrates and on the relationship between local and regional species richness. Fifty-three wave-exposed sites were sampled along the coast of Chile between 18°40' S and 42°35' S, covering a range of over 2600 km and 25°of latitude. Three spatial scales were defined to analyze latitudinal trends of diversity: (1) regional, based on species range limits across the entire region (100s of km), (2) site, corresponding to hundreds of square meters sampled at each location, (3) sampling unit scale, corresponding roughly with a square meter of rocky shore. The analysis showed that spatial patterns of species richness and species turnover varied according to the scale used. At a regional scale, species richness showed a mid-latitudinal peak (i.e. around 30 to 32°S), decreasing toward northern and southern latitudes. No clear latitudinal trends in diversity were detected at site and especially at sampling unit scales. Despite the fact that at regional scale species turnover was low and geographically uniform, at the site scale beta diversity showed the existence of 2 zones of higher species turnover (19 to 20°S and 30 to 32°S), which may be attributed to changes in ecological and oceanographical regimes. The relationship between regional and local species richness changed depending on the 'local' scale used; unsaturated patterns (linear positive relationship between local and regional diversity) were evident at site scale, whereas saturated patterns (quadratic trend between local and regional diversity) were observed when the local scale was defined in terms of the sampling unit. We suggest that different regulating processes, operating at different spatial scales, may explain the latitudinal trends in diversity at site and sampling unit scales. While regional processes may set an upper limit in species richness at site scale, species interactions (e.g. competition) may control species richness at sampling unit scales. These findings question the current idea of the disproportionate prevalence of regional factors over local ones in determining diversity of local assemblages. They also suggest that regulation of local diversity results from the interplay of regional and local processes.

Ecology Letters, 2004

Theory suggests that variation in resource supply should propagate up trophic webs influencing pl... more Theory suggests that variation in resource supply should propagate up trophic webs influencing plant-herbivore interactions and abundances. Community regulation models have been tested in several ecosystems, but benthic marine ecologists have largely overlooked bottom-up factors except at the largest spatial scales. We used naturally occurring variation in nutrient supply associated with upwelling intensity (over 10s of kilometre) to test community regulation models. Higher upwelling intensity was strongly associated with increased abundance of late-successional, corticated algae, which in turn had apparent negative effects on ephemeral algae. Corticated algae were resistant to extant levels of herbivory. As a result, corticated algae were more abundant at sites of high upwelling intensity, while ephemeral algae were more abundant at sites of low upwelling intensity. We speculate that human removal of large grazers that can feed on corticated algae may interact with natural variation in nutrient supply to shift community structure over mesoscales.

Marine Ecology Progress Series, 1993

The rocky intertidal zone of central Chile compnses a diverse array of invertebrate and vertebrat... more The rocky intertidal zone of central Chile compnses a diverse array of invertebrate and vertebrate (i.e. birds, fish, humans) predators In this system, like in most temperate rocky shores, predation by small 'terrestrial' mammals such as mice and rats has been largely overlooked. This study documents predation on intertidal organisms by Norway rats Rattus norvegicus in a marine preserve in Las Cruces, central Chile. Five species of small mammals, 3 endemic and 2 introduced, were found in the littoral zone of the marine preserve. R. norvegicus was the most abundant of these species throughout the year-long mark-recapture study. Ten burrows of R. norvegicus containing remains of intertidal organisms were located in the littoral zone, 8 inside the marine preserve and 2 ca 200 m outside. Remains found in the burrows and stomach content analyses showed that rats prey on 40 d~fferent intertidal species, including both mobile and sessile organisms from the mid to the very low intertidal zone. The most numerous prey species in the burrows were keyhole limpets (490 individuals), mostly Fissurella crassa, followed by porcelanid crabs (187 individuals) and cancrid crabs of the genus Acanthoc}/clus (101 individuals). Prey composition in the burrows varied greatly. Some burrows were dominated by keyhole limpets and others by crabs, suggesting some degree of specialization by individual rats. Comparison between keyhole limpets found in burrows and on intertidal rocks inside the marine preserve showed that rats remove the smaller, less abundant sizes of keyhole limpets from the population, probably due to mechanical restrictions to dislodging larger individuals. The number of small keyhole limpets (<55 mm long) that Norway rats can potentially remove from the marine preserve in a year (over 8730) as compared to numbers of small limpets in the preserve, suggest that R. norvegicus may have important effects on the population structure and abundance of these species. Since humans deplete keyhole limpet populations outside the marine preserve, rats may compensate for part of the effects of humans harvesting inside the preserve. Preliminary data suggest that rats are less abundant in places distant from human populations and thus the proximity to human populations can be an important factor in deciding the location of marine preserves.

The way strong environmental gradients shape multispecific assemblages has allowed us to examine ... more The way strong environmental gradients shape multispecific assemblages has allowed us to examine a suite of ecological and evolutionary hypotheses about structure, regulation, and community responses to fluctuating environments. But whether the highly diverse co-occurring, free-living microorganisms are shaped in similar ways as macroscopic organisms, across the same gradients, has yet to be addressed in most ecosystems. The ‘everything is everywhere’ hypothesis suggests they are not, at least not to the same extent. Here we characterize the structure of intertidal microbial biofilm communities and compare the intensity of zonation at the ‘species’ level, changes in taxonomic diversity and composition at the community level, and network attributes, with those observed in co-occurring macroalgae and invertebrates. At the level of species and OTUs, for dominant macro and microorganisms respectively, microbes showed less variability across the tidal gradient than macroorganisms. At the...

Disruptions can be defined as interference with the orderly course of a process. Several differen... more Disruptions can be defined as interference with the orderly course of a process. Several different general mechanisms can be considered as ecological disruptions. Perhaps the most discussed is the concept of disturbance. Two general perspectives of disturbance have emerged in the literature. A view generally taken by terrestrial ecologists is that disturbance is a pulsed perturbation from an equilibrium state (White and Pickett 1985) . This definition follows more closely the dictionary definition of disturbance, and is similar to the idea of ecological disruption. Implicit in this definition is that an identifiable equilibrium state of a system exists, and that the system tends to converge to that equilibrium state in the absence of disturbance. A second definition of disturbance is a physical process that removes living biomass from an ecosystem (Sousa 1984b) . This definition requires neither that an equilibrium reference point be identified, nor that the system must reach the eq...

Scientific reports, Jan 12, 2018

Understanding the factors that modulate bacterial community assembly in natural soils is a longst... more Understanding the factors that modulate bacterial community assembly in natural soils is a longstanding challenge in microbial community ecology. In this work, we compared two microbial co-occurrence networks representing bacterial soil communities from two different sections of a pH, temperature and humidity gradient occurring along a western slope of the Andes in the Atacama Desert. In doing so, a topological graph alignment of co-occurrence networks was used to determine the impact of a shift in environmental variables on OTUs taxonomic composition and their relationships. We observed that a fraction of association patterns identified in the co-occurrence networks are persistent despite large environmental variation. This apparent resilience seems to be due to: (1) a proportion of OTUs that persist across the gradient and maintain similar association patterns within the community and (2) bacterial community ecological rearrangements, where an important fraction of the OTUs come t...

PLOS Biology, 2016

Species are linked to each other by a myriad of positive and negative interactions. This complex ... more Species are linked to each other by a myriad of positive and negative interactions. This complex spectrum of interactions constitutes a network of links that mediates ecological communities' response to perturbations, such as exploitation and climate change. In the last decades, there have been great advances in the study of intricate ecological networks. We have, nonetheless, lacked both the data and the tools to more rigorously understand the patterning of multiple interaction types between species (i.e., "multiplex networks"), as well as their consequences for community dynamics. Using network statistical modeling applied to a comprehensive ecological network, which includes trophic and diverse non-trophic links, we provide a first glimpse at what the full "entangled bank" of species looks like. The community exhibits clear multidimensional structure, which is taxonomically coherent and broadly predictable from species traits. Moreover, dynamic simulations suggest that this non-random patterning of how diverse non-trophic interactions map onto the food web could allow for higher species persistence and higher total biomass than expected by chance and tends to promote a higher robustness to extinctions.