DSpace Angular :: Browsing by Author "Perez-Matus, Alejandro"

Browsing by Author "Perez-Matus, Alejandro"

Now showing 1 - 20 of 31

A High-Resolution Global Map of Giant Kelp (Macrocystis pyrifera) Forests and Intertidal Green Algae (Ulvophyceae) with Sentinel-2 Imagery
(2020) Mora-Soto, Alejandra; Palacios, Mauricio; Macaya, Erasmo C.; Gomez, Ivan; Huovinen, Pirjo; Perez-Matus, Alejandro; Young, Mary; Golding, Neil; Toro, Martin; Yaqub, Mohammad; Macias-Fauria, Marc
Giant kelp (Macrocystis pyrifera) is the most widely distributed kelp species on the planet, constituting one of the richest and most productive ecosystems on Earth, but detailed information on its distribution is entirely missing in some marine ecoregions, especially in the high latitudes of the Southern Hemisphere. Here, we present an algorithm based on a series of filter thresholds to detect giant kelp employing Sentinel-2 imagery. Given the overlap between the reflectances of giant kelp and intertidal green algae (Ulvophyceae), the latter are also detected on shallow rocky intertidal areas. The kelp filter algorithm was applied separately to vegetation indices, the Floating Algae Index (FAI), the Normalised Difference Vegetation Index (NDVI), and a novel formula (the Kelp Difference, KD). Training data from previously surveyed kelp forests and other coastal and ocean features were used to identify reflectance threshold values. This procedure was validated with independent field data collected with UAV imagery at a high spatial resolution and point-georeferenced sites at a low spatial resolution. When comparing UAV with Sentinel data (high-resolution validation), an average overall accuracy >= 0.88 and Cohen's kappa >= 0.64 coefficients were found in all three indices for canopies reaching the surface with extensions greater than 1 hectare, with the KD showing the highest average kappa score (0.66). Measurements between previously surveyed georeferenced points and remotely-sensed kelp grid cells (low-resolution validation) showed that 66% of the georeferenced points had grid cells indicating kelp presence within a linear distance of 300 m. We employed the KD in our kelp filter algorithm to estimate the global extent of giant kelp and intertidal green algae per marine ecoregion and province, producing a high-resolution global map of giant kelp and intertidal green algae, powered by Google Earth Engine.
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.
Behavioral and chromatic dynamics describing mating interactions of the south American octopus Robsonella fontaniana (Cephalopoda: Octopodidae)
(2023) Cifuentes, Victor; Perez-Matus, Alejandro; Fernandez, Miriam; Ibanez, Christian M.; Carrasco, Sergio A.
Cephalopods are characterized by a substantial behavioral flexibility during reproductive interactions; however, for octopods rather few studies have provided empirical information on the mechanisms operating during male-male and male-female encounters. Using the small south American octopus Robsonella fontaniana (similar to 270 mm total length, similar to 70 mm mantle length), we evaluated the mating behavior based on octopuses from central Chile. Eighteen male-female and five male-male interactions were characterized in laboratory using ethograms divided into precopulatory and copulatory stages. Although subjects' interactions occurred in both treatments, extended mating periods (81-196 min) were only observed in the male-female trials, and specifically, in those involving larger octopuses (39% of the interactions; > 43 mm mantle length). During the precopulatory stage (4-20 min), different behavioral displays were evidenced in 57% of these male-female interactions, including: contact, exhibition of chromatic displays, swimming, and mounting. Larger pairs had longer copulation times, with a maximum of similar to 200 min in octopuses of 50 mm mantle length. The observed mating in adult male-female pairs and the practically null interaction between juveniles suggest that a maturity-conditional reproductive behavior (similar to 43 mm mantle length; similar to 38 gr), could be one of the mechanisms modulating mating interactions of R. fontaniana in the wild, potentially influencing aspects such as mate guarding behavior, possible sperm removal or sperm loading. (c) 2023 Elsevier B.V. All rights reserved.
Different kelp species support unique macroinvertebrate assemblages, suggesting the potential community-wide impacts of kelp harvesting along the Humboldt Current System
(2022) Carbajal, Patricia; Gamarra Salazar, Alex; Moore, Pippa J.; Perez-Matus, Alejandro
Kelp forests provide habitat for myriad species yet remain poorly studied in some ecoregions, including where there is increasing interest in commercial kelp harvesting for the lucrative alginate industry. To identify indicators for monitoring the impacts of kelp harvesting, the structure and composition of macrobenthic invertebrate assemblages associated with large brown macroalgae, Eisenia cokeri, Lessonia trabeculata and Macrocystis pyrifera, from the Humboldt Current System of Peru were determined. Within kelp habitats two distinct habitats were sampled: (a) adult kelp holdfasts; and (b) the benthos adjacent to the kelp sporophyte (hereafter under-canopy rock). For each sample, organisms were identified, enumerated and weighed. Totals of 108, 102 and 113 different species were found associated with Eisenia cokeri, M. pyrifera and L. trabeculata, respectively comprising distinct assemblages associated with each kelp forest. Both habitat types (holdfasts and under-canopy rock) supported diverse, but different, macroinvertebrate assemblages, with richness, abundance and functional trophic groups in general higher in holdfasts compared with on under-canopy rock. Lastly, macroinvertebrate abundance, biomass, and species richness significantly increased with holdfast size. Results confirm that each kelp species is unique in terms of associated assemblage composition and indicate that kelp harvesting for the alginate industry may have large impacts. We suggest that these effects on associated biodiversity should be incorporated within kelp harvesting management plans. We suggest that holdfast diameter is a good ecological indicator as reductions in holdfast size across the population will indicate a decline in the diversity of macroinvertebrates that are important food sources for higher order organisms. We therefore suggest that monitoring studies include morphological measurements as well as measurement of kelp density.
DNA reconciles morphology and colouration in the drunk blenny genus Scartichthys (Teleostei: Blenniidae) and provides insights into their evolutionary history
(2022) Delrieu-Trottin, Erwan; Hartmann-Salvo, Hans; Saenz-Agudelo, Pablo; Landaeta, Mauricio F.; Perez-Matus, Alejandro
The blenniids of the genus Scartichthys are one of the most common fishes of Central and South American Pacific coastal reefs. This being said, Scartichthys spp. remain difficult to identify in the field, and identification is particularly challenging across the c. 6000 km where three of the four currently accepted species are known to occur in sympatry. A reason for this is that the main taxonomic characters from traditional taxonomy are indeed elusive. In addition, at the same time, species can display multiple colour patterns in the field, depending on their ontogenetic stage, habitat association and reproductive behaviour. Overall, molecular characterization is warranted to help address these issues. In this study, the authors have used a novel approach to revise the genus by combining colouration, morphological and molecular data of representative specimens of the four currently valid species and seven described colour patterns. From this, the authors show that only three of the four species should be considered as valid; Scartichthys gigas (Steindachner, 1876), Scartichthys variolatus (Valenciennes, 1836) and Scartichthys viridis (Valenciennes, 1836), whereas Scartichthys crapulatus (Williams, Smithsonian Contributions to Zoology, 1990, 492, 1-30) should be synonymized with S. viridis. In the same way, the analyses in this study show that one of the colour patterns attributed so far only to S. gigas is characteristic of the juvenile stages of S. viridis. The time-calibrated phylogeny of this study shows that this genus is relatively young and that the estimated time of divergence between S. gigas and S. viridis is c. 1.71 Ma. In comparison, the Desventuradas and Juan Fernandez Islands endemic S. variolatus diverged c. 1.95 Ma. The results of this study help to clarify the taxonomy of Scartichthys.
Effects of harvesting on subtidal kelp forests (Lessonia trabeculata) in central Chile
(2022) Bularz, Bryan; Fernandez, Miriam; Subida, Maria Dulce; Wieters, Evie A.; Perez-Matus, Alejandro
The systematic degradation of marine ecosystems is a global phenomenon that has important and diverse consequences including biodiversity loss and reduced ecosystem service provisions. In temperate regions, subtidal kelp forests are dominant ecosystems in rocky coasts, subjected to the influence of local-scale stressors and regional environmental variation. For example, kelps within the Humboldt Current System are at risk of degradation from live-harvesting by fisheries. However, limited information exists regarding the long-term consequences of kelp harvesting, which, in turn, limits the ability to provide effective management and conservation efforts. Here, we examined the ecosystem-level consequences of the artisanal subtidal Lessonia trabeculata fishery along the coast of central Chile during a 2-year period, assessing (1) the change in adult and juvenile L. trabeculata density within harvested and nonharvested (control) plots (similar to 90 m(2)), (2) the impact of L. trabeculata harvesting on reef fish and macroinvertebrate assemblages, and (3) the change in density of the most abundant L. trabeculata-associated species. The experiment was conducted over a 2-year period, from December 2016 to May 2019. Approximately 90% of L. trabeculata was removed by an experienced kelp fisherman in experimental plots. After 2 years, L trabeculata and its associated community showed a lack of recovery in the harvested plots. Within these plots, the average abundance of the rock shrimp, Rhynchocinetes typus, and the herbivorous snail, Tegula tridentata, was greater than in nonharvested plots and the pattern persisted over the study period. The difference in abundance of associated species may be key to the (lack of) recovery of L. trabeculata forests. Our study highlights the impact of L. trabeculata harvesting on associated fauna; however, significant knowledge gaps remain regarding the capacity and time frame to reestablish the original biomass of L trabeculata, as well as its associated fauna. The management of L. trabeculata fisheries needs to account for ecosystem-wide impacts in order to better manage and protect vital coastal ecosystems.
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.
Evolutionary origin of the Atlantic Cabo Verde nibbler (Girella stuebeli), a member of a primarily Pacific Ocean family of antitropical herbivorous reef fishes
(2021) Beldade, Ricardo; Longo, Gary C.; Clements, Kendall D.; Robertson, D. Ross; Perez-Matus, Alejandro; Itoi, Shiro; Sugita, Haruo; Bernardi, Giacomo
Nibblers (family Girellidae) are reef fishes that are mostly distributed in the Indo-Pacific, with one exception: Girella stuebeli, which is found in the Cabo Verde Archipelago, in the Atlantic Ocean. We capitalized on this unusual distribution to study the evolutionary history of the girellids, and determine the relationship between G. stuebeli and the remaining nibbler taxa. Based on thousands of genomic markers (RAD sequences), we identified the closest relatives of G. stuebeli as being a clade of three species endemic to the northwestern Pacific, restricted to the Sea of Japan and vicinity. This clade diverged from G. stuebeli approximately 2.2 Mya. Two alternative potential routes of migration may explain this affinity: a western route, from the Tropical Eastern Pacific and the Tropical Western Atlantic, and an eastern route via the Indian Ocean and Southern Africa. The geological history and oceanography of the regions combined with molecular data presented here, suggest that the eastern route of invasion (via the Indian Ocean and Southern Africa) is a more likely scenario.
Functional community structure of shallow hard bottom communities at Easter Island (Rapa Nui)
(2014) Wieters, Evie A.; Medrano, Alba; Perez-Matus, Alejandro
Important, often abrupt, and irreversible shifts associated with the degradation of ecosystem functioning and services are increasingly commonplace. Thus, a trait-based view of communities may be more insightful than that based solely on species composition, especially when inferring ecological responses to environmental change. This underscores the importance and urgency of establishing benchmarks against which future community changes and functional structure can be evaluated. As a first step toward setting these baselines and their current spatial variability, we here describe geographic and among-habitat patterns in the functional structure of shallow hard bottom communities, including fish assemblages, across the northeast and west coasts of Rapa Nui. We also document temporal patterns of change in dominant benthic functional groups that have taken place over the past 15 years at selected sites on this isolated Pacific island. Generally weak vertical zonation patterns were observed, with most striking differences due to the paucity of branching pocilloporid corals in shallow waters(<7 m), where massive corals of Porites predominate. We identified three main 'groups' of sites in terms of the relative abundance of major functional groups and these did not follow geographic arrangement or strict coastline orientation. The similar spatial change in benthic and fish functional community structure documented here suggests there may be strong coupling with coastal oceanographic conditions that varies on scales of 1s-10s of km. Temporal patterns document relatively rapid recovery of total coral cover, largely via compensatory change in relative coral composition with an increase in Porites upon abrupt decline of Pocillopora, following extensive coral mortality caused by thermal stress (coral bleaching) in 2000. Moreover, coral abundance in shallow habitats increased beyond pre-disturbance levels (i.e., 1999-2000). In contrast to shallow habitats, corals again suffered extensive mortality and reduced cover by 2005 at mid-(10-15 m) and deep (>15 m) habitats, with contrasting recovery. These results suggest depth-dependent disturbance regimes that differ in types and frequency of events, as well as capacity to recover. Overall, our results highlight the apparent resilience of the current system and provide a first-cut benchmark as to where management subsystems might be prescribed so as to spatially match ecosystem characteristics.
Pseudanthias hangapiko, a new anthiadine serranid (Teleostei, Serranidae, Anthiadinae) from Rapa Nui (Easter Island)
(2021) Shepherd, Bart; Pinheiro, Hudson T.; Phelps, Tyler A. Y.; Perez-Matus, Alejandro; Rocha, Luiz A.
Pseudanthias hangapiko sp. nov. (Teleostei, Serranidae, Anthiadinae) is herein described from three specimens collected from a depth of 83 m in a mesophotic coral ecosystem off Hanga Piko, Rapa Nui (Easter Island), Chile. Pseudanthias hangapiko sp. nov. can be distinguished from its congeners in live coloration and by the following combination of characters: dorsal-fin rays X, 17; anal-fin rays III, 8; pectoral-fin rays 16 (left side of one specimen 17); vertebrae 10+16; scales relatively large, two scales above lateral-line to base of fifth dorsal spine, and 16-17 circumpeduncular scales; gill rakers 11+23; and a slender body, with greatest body depth 3.6 (3.4- 3.8) in SL. The most similar DNA barcodes (mitochondrial COI gene) are from Pseudanthias ventralis Randall, 1979 and Pseudanthias hawaiiensis Randall, 1979, with 16.8% and 17.0% uncorrected divergence, respectively. This fish is one of four new species that were documented from a pair of technical dives at a single location in Rapa Nui, emphasizing the high number of undescribed species likely still unknown in mesophotic coral ecosystems, especially in geographically remote locations. Pseudanthias hangapiko sp. nov. adds to the Rapa Nui ichthyofauna, which hosts the second-highest level of endemism in both shallow and deep-water fishes.
Independent Effects of Species Removal and Asynchrony on Invariability of an Intertidal Rocky Shore Community
(2022) Fica-Rojas, Eliseo; Catalan, Alexis M.; Broitman, Bernardo R.; Perez-Matus, Alejandro; Valdivia, Nelson
Ecological stability depends on interactions between different levels of biological organization. The insurance effects occur when increasing species diversity leads to more temporally invariable (i.e., more stable) community-level properties, due in part to asynchronous population-level fluctuations. While the study of insurance effects has received considerable attention, the role of dominant species that contribute with particular functional traits across different level of organizations is less understood. Using a field-based manipulative experiment, we investigated how species richness and different types of parameters at the population level, such as the invariability of dominants, population invariability, and population asynchrony, influence the community invariability. The experiment involved the repetitive removal of the canopy forming alga Mazzaella laminarioides (hereafter "Mazzaella") during 32 months in two rocky intertidal sites of northern-central Chile. We predicted that the invariability of dominants enhances community invariability, that the effect of multispecies population-level parameters on community invariability are dependent on species richness, and that subdominant algae are unable to fully compensate the loss of canopies of the dominant species. Biomass of algae and mobile invertebrates was quantified over time. We observed independent effects of Mazzaella removal and community-wide asynchrony on community invariability. While canopy removal reduced community invariability, population asynchrony boosted community invariability regardless of the presence of canopies. In addition, filamentous and foliose algae were unable to compensate the loss of biomass triggered by the experimental removal of Mazzaella. Canopy removal led to a severe decrement in the biomass of macrograzers, while, at the same time, increased the biomass of mesograzers. Asynchrony stemmed from compensatory trophic responses of mesograzers to increased abundances of opportunistic algae. Thus, further work on consumer-resource interactions will improve our understanding of the links between population- and community-level aspects of stability.
Limited effects of management and ecological subsidies on the size-spectra of kelp forest fish communities
(2024) Gartenstein, Simon; Perez-Matus, Alejandro; Heather, Freddie J.; Godoy, Natalio; Torres-Canete, Felipe; Catalan, Alexis M.; Valdivia, Nelson
Animal body size influences key ecological processes across biological hierarchies. For instance, densities (N) and community biomass (B) are allometric functions of body mass (M). Energetic equivalence predicts that density scales with body size as N proportional to M-0.75 and that biomass scales with body size as B proportional to M0.25. However, the way fish size-spectra are influenced by external processes, such as ecological subsidies (e.g. nutrients from upwelling zones) and fisheries management, is not well understood. We investigated the relationship of body size with density and biomass of reef fishes associated with subtidal kelp forests of Lessonia trabeculata that were influenced by the separate and interactive effects of management (Territorial Use Rights for Fisheries [TURF] or open access) and upwelling regimes (upwelling or non-upwelling zones). Fish densities and lengths were recorded using underwater visual censuses. Within each of 4 locations, paired TURF and open-access sites were surveyed. We surveyed 18 fish species, encompassing 1511 individuals ranging between 2 and 6639 g. We observed that fish size-spectra deviated from energetic equivalence, as N proportional to M-0.32 and B proportional to M2.2, indicating that the contribution of large-sized fishes to community density and biomass was greater than that predicted by energetic equivalence. Multi-model inference suggested that TURF and upwelling scenarios had weak effects on fish size-spectra. Results indicated that fish communities may have access to external food sources beyond local kelp forests. In addition, size-spectra may be a spatially persistent attribute of these fish communities.
Macroalgal meadow habitats support fish and fisheries in diverse tropical seascapes
(2020) Fulton, Christopher J.; Berkstrom, Charlotte; Wilson, Shaun K.; Abesamis, Rene A.; Bradley, Michael; akerlund, Carolina; Barrett, Luke T.; Bucol, Abner A.; Chacin, Dinorah H.; Chong-Seng, Karen M.; Coker, Darren J.; Depczynski, Martial; Eggertsen, Linda; Eggertsen, Maria; Ellis, David; Evans, Richard D.; Graham, Nicholas A. J.; Hoey, Andrew S.; Holmes, Thomas H.; Kulbicki, Michel; Leung, Priscilla T. Y.; Lam, Paul K. S.; van Lier, Joshua; Matis, Paloma A.; Noble, Mae M.; Perez-Matus, Alejandro; Piggott, Camilla; Radford, Ben T.; Tano, Stina; Tinkler, Paul
Canopy-forming macroalgae can construct extensive meadow habitats in tropical seascapes occupied by fishes that span a diversity of taxa, life-history stages and ecological roles. Our synthesis assessed whether these tropical macroalgal habitats have unique fish assemblages, provide fish nurseries and support local fisheries. We also applied a meta-analysis of independent surveys across 23 tropical reef locations in 11 countries to examine how macroalgal canopy condition is related to the abundance of macroalgal-associated fishes. Over 627 fish species were documented in tropical macroalgal meadows, with 218 of these taxa exhibiting higher local abundance within this habitat (cf. nearby coral reef) during at least one life-history stage. Major overlap (40%-43%) in local fish species richness among macroalgal and seagrass or coral reef habitats suggest macroalgal meadows may provide an important habitat refuge. Moreover, the prominence of juvenile fishes suggests macroalgal meadows facilitate the triphasic life cycle of many fishes occupying diverse tropical seascapes. Correlations between macroalgal canopy structure and juvenile abundance suggests macroalgal habitat condition can influence levels of replenishment in tropical fish populations, including the majority of macroalgal-associated fishes that are targeted by commercial, subsistence or recreational fisheries. While many macroalgal-associated fishery species are of minor commercial value, their local importance for food and livelihood security can be substantial (e.g. up to 60% of landings in Kenyan reef fisheries). Given that macroalgal canopy condition can vary substantially with sea temperature, there is a high likelihood that climate change will impact macroalgal-associated fish and fisheries.
Mismatch between shape changes, early growth, and condition for a temperate reef fish from an oceanic island
(2021) Landaeta, Mauricio F.; Figueroa-Gonzalez, Yanara; Moyano, Gonzalo; Vera-Duarte, Javier; Perez-Matus, Alejandro; Plaza, Guido
Settlement is a key process in the life history of marine fish, when shape and ecological changes occur during the transition from a pelagic larva to a benthic juvenile. We studied the covariation of shape changes, condition, and pre- and post-settlement growth of settlers (17-30 mm) of the wrasse, Pseudolabrus gayi, from the Robinson Crusoe island, south-eastern Pacific. Specimens were collected during late March 2018 from four locations at 20 m depth and from a large, natural intertidal pool. The morphospace and the allometry were characterised by landmarkbased geometric morphometrics, size and growth were estimated using sagittae otolith microstructure analysis, and condition was determined using the Fulton index. The settler's phenotype varied from a robust shape with ventrally oriented mouth opening, to slender specimens with frontally oriented mouth, with similar body morphospace among sites. The mean pelagic larval duration was 44.8 +/- 4.6 days, settling at 19 +/- 2 mm SL. The mean post-settlement growth rate was low (0.09 mm day(-1)), showing low static allometry (3%). Differences among locations occurred in terms of settler's condition and growth prior and after settlement, suggesting effects of the microhabitat and potential predators. Therefore, the variability in the settler's morphospace was decoupled of pre- and post-settlement growth and condition during the transition from pelagic to benthic habitat. Finally, this study highlights the dynamic nature of the settlement-transition period for a temperate reef fish in a period when phenotype variations in body shape and early life-history traits vary asynchronously.
Multiscale Spatial Variability and Stability in the Structure and Diversity of Bacterial Communities Associated with the Kelp Eisenia cokeri in Peru
(2023) King, Nathan G.; Uribe, Roberto; Moore, Pippa J.; Earp, Hannah S.; Gouraguine, Adam; Hinostroza, Diego; Perez-Matus, Alejandro; Smith, Kathryn; Smale, Dan A.
Ecological communities are structured by a range of processes that operate over a range of spatial scales. While our understanding of such biodiversity patterns in macro-communities is well studied, our understanding at the microbial level is still lacking. Bacteria can be free living or associated with host eukaryotes, forming part of a wider "microbiome," which is fundamental for host performance and health. For habitat forming foundation-species, host-bacteria relationships likely play disproportionate roles in mediating processes for the wider ecosystem. Here, we describe host-bacteria communities across multiple spatial scales (i.e., from 10s of m to 100s of km) in the understudied kelp, Eisenia cokeri, in Peru. We found that E. cokeri supports a distinct bacterial community compared to the surrounding seawater, but the structure of these communities varied markedly at the regional (similar to 480 km), site (1-10 km), and individual (10s of m) scale. The marked regional-scale differences we observed may be driven by a range of processes, including temperature, upwelling intensity, or regional connectivity patterns. However, despite this variability, we observed consistency in the form of a persistent core community at the genus level. Here, the genera Arenicella, Blastopirellula, Granulosicoccus, and Litorimonas were found in >80% of samples and comprised similar to 53% of total sample abundance. These genera have been documented within bacterial communities associated with kelps and other seaweed species from around the world and may be important for host function and wider ecosystem health in general.
Observations on the early development of the kelpfish Myxodes viridis (Clinidae) with the first description of their spawning habitat in subtidal kelp forests (Lessonia trabeculata)
(2021) Ruz, Catalina S.; Garmendia, Vladimir; Munoz-Cordovez, Rodrigo; Wieters, Evie; Perez-Matus, Alejandro
The spawning sites, embryonic development, and initial larval stages were described for the Chilean kelpfish, Myxodes viridis. Six different egg clutches were found attached by an elastic filament to the fronds of the subtidal kelp, Lessonia trabeculata, at shallow depths (0-7 m). All egg clutches were cared for by one large (>15 cm TL) male, and egg color varied depending on the developmental stage. Embryonic development until hatching was categorized into 7 stages, which were completed within about 18 days in the laboratory. Recently hatched larvae presented fully pigmented eyes, a well-developed mouth with major shape changes in the head during the first week suggesting their ability to feed on plankton early in their larval development.
One of the least disturbed marine coastal ecosystems on Earth: Spatial and temporal persistence of Darwin's sub-Antarctic giant kelp forests
(2021) Mora-Soto, Alejandra; Capsey, Austin; Friedlander, Alan M.; Palacios, Mauricio; Brewin, Paul E.; Golding, Neil; Dayton, Paul; Van Tussenbroek, Brigitta; Montiel, Americo; Goodell, Whitney; Velasco-Charpentier, Catalina; Hart, Tom; Macaya, Erasmo C.; Perez-Matus, Alejandro; Macias-Fauria, Marc
Aim Marine habitats and their dynamics are difficult to systematically monitor, particularly those in remote locations. This is the case with the sub-Antarctic ecosystem of the giant kelp Macrocystis pyrifera, which was already noted by Charles Darwin in his accounts on the Voyage of the Beagle and recorded on the nautical charts made during that expedition. We combined these and other nautical charts from the 19th and early 20th centuries with surveys conducted in the 1970s and 1980s and satellite detection algorithms from 1984 to 2019, to analyse kelp distribution through time and the factors that correlate with it. Location Marine ecoregions of Channels and Fjords of Southern Chile, Falkland Islands (Malvinas), and the island of South Georgia. Taxon Macrocystis pyrifera. Methods We characterised 309 giant kelp forests by their coastal geospatial attributes. Statistically significant variables were included in a conditional inference tree to predict kelp forest size. Sea surface temperature (SST) records were analysed to confirm temperature ranges over the last four decades. Nautical charts, historical surveys, aerial photogrammetry, unmanned aerial vehicle (UAV) surveys and satellite imagery were overlaid to assess spatial distribution of kelp forest canopies, spanning the period 1829-2020. Results Considering the extensive natural and human caused changes over the last two centuries, this diverse kelp ecosystem is remarkably persistent. We found that the ocean currents and wave exposure, combined with the geomorphological settings of the coastline are the most critical factors predicting the extent of the kelp forests. Main conclusions We have described the long-term ecological persistence of the kelp forests in this vastly under-studied region that offers a conceptual biogeographical model supporting the global importance proposed by Charles Darwin 200 years ago (Darwin, 1845). In the current context of global change, the need for conservation of this persistent and well-preserved marine ecosystem has never been more important.
Phylogeography of the California sheephead, Semicossyphus pulcher: the role of deep reefs as stepping stones and pathways to antitropicality
(2013) Poortvliet, Marloes; Longo, Gary C.; Selkoe, Kimberly; Barber, Paul H.; White, Crow; Caselle, Jennifer E.; Perez-Matus, Alejandro; Gaines, Steven D.; Bernardi, Giacomo
In the past decade, the study of dispersal of marine organisms has shifted from focusing predominantly on the larval stage to a recent interest in adult movement. Antitropical distributions provide a unique system to assess vagility and dispersal. In this study, we have focused on an antitropical wrasse genus, Semicossyphus, which includes the California sheephead, S.pulcher, and Darwin's sheephead, S.darwini. Using a phylogenetic approach based on mitochondrial and nuclear markers, and a population genetic approach based on mitochondrial control region sequences and 10 microsatellite loci, we compared the phylogenetic relationships of these two species, as well as the population genetic characteristics within S.pulcher. While S.pulcher and S.darwini are found in the temperate eastern Pacific regions of the northern and southern hemispheres, respectively, their genetic divergence was very small (estimated to have occurred between 200 and 600 kya). Within S.pulcher, genetic structuring was generally weak, especially along mainland California, but showed weak differentiation between Sea of Cortez and California, and between mainland California and Channel Islands. We highlight the congruence of weak genetic differentiation both within and between species and discuss possible causes for maintenance of high gene flow. In particular, we argue that deep and cooler water refugia are used as stepping stones to connect distant populations, resulting in low levels of genetic differentiation.
Predator tactics and prey densities modulate the strength of trophic interactions in a temperate rocky reef
(2021) Munoz-Cordovez, Rodrigo H.; Carrasco, Sergio A.; Ojeda, F. Patricio; Perez-Matus, Alejandro
Evaluating the species-specific effects of multiple predators on shared prey helps to identify the mechanisms regulating predator impacts. Here, we investigate the trophic impact of two predators of the Chilean rocky subtidal, the fish Graus nigra [F] and the octopus Robsonella fontaniana [O] on their shared prey, the porcelain crab, Petrolisthes violaceus. Manipulative laboratory experiments were performed to evaluate mortality and behavior of porcelain crab in different treatments, including prey alone; prey with single predator ([O] or [F]); and prey with combined predators ([F + F], [O + O], and [O + F]). Different prey densities (N = 3, 9, and 12 individuals) were used to explore density-dependent predation mortality for single and combined predators using an orthogonal (crossed) design that allows to tease apart the effects of predator taxonomic identity from prey density. Behavioral responses of interacting species were registered every 4 h for 2 consecutive days, and were used to identify predator foraging strategies and prey refuge use. Mortality values (proportional prey mortality and predator per capita consumption) were compared among treatments. Results indicated differences in mortality among treatments. The cause of increase of prey proportional mortality was due to an increase in prey availability outside the refuge in fish treatments at high initial prey densities, while it was density independent in octopus' treatments. Changes in predator per capita consumption were registered depending on the predator combination and the initial prey density. These patterns may reflect contrasting predator foraging strategies and changes in refuge use by porcelain crabs, suggesting effects on prey mortality and predator impacts.
Reef Fish Diversity Across the Temperate South Pacific Ocean
(2022) Perez-Matus, Alejandro; Neubauer, Philipp; Shima, Jeffrey S.; Rivadeneira, Marcelo M.
Patterns of species richness and their structuring forces at multiple scales provide a critical context for research efforts focusing on ecology, evolution, and conservation. Diversity gradients have been demonstrated in tropical reef fish, but corresponding patterns and mechanisms remain poorly understood in temperate regions. We conducted hierarchical (spatially nested) sampling of temperate reef fish faunas across > 140 degrees of longitude in the eastern and western South Pacific Ocean. Our sampling efforts spanned five distinct provinces: the Southeast Australian Shelf (SAS), Northern and Southern New Zealand (N-SNZ), Juan Fernandez and Desventuradas Islands (JFD), and the Warm Temperate Southeastern Pacific (WTPA). We evaluated (i) spatial variation in patterns of species richness and abundance (using Chao 1 index), and distribution of functional diversity (using several functional attributes: max body size, trophic groups, feeding guilds, trophic level, habitat use, gregariousness, and activity patterns) and (ii) scale-dependencies in these patterns. Species richness declined from west to east across the temperate South Pacific, but this pattern was detectable only across larger spatial scales. A functional redundancy index was significantly higher in the western South Australian Shelf at multiple scales, revealing that species contribute in equivalent ways to an ecosystem function such that one species may substitute for another. We also detected that patterns of variation in functional diversity differed from patterns of variation in species richness, and were also dependent on the spatial scale of analysis. Lastly, we identified that species' traits are not equally distributed among reef fish assemblages, where some provinces are characterized by a distinct functional component within their reef fish assemblages. Planktivorous and schooling species, for instance, dominated the assemblages in the eastern Pacific, which is characterized by higher primary productivity and steep bathymetric slopes favoring these traits. Demersal and pairing behavior traits dominated the reef fish assemblages in western Pacific provinces (SAS, SNZ). We conclude that combining the identifies and species' traits allow us to disentangle historical, biogeographic and environmental factors that structure reef fish fauna.

Browsing by Author "Perez-Matus, Alejandro"

Results Per Page

Sort Options