Browsing by Author "Bonicelli, Jessica"

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    Abundance, composition and succession of sessile subtidal assemblages in high wave-energy environments of Central Chile : temporal and depth variation
    (2019) Navarrete C., Sergio; Parrague Guzmán, Mirtala Adriana; Osiadacz, Nicole; Rojas, Francisca; Bonicelli, Jessica; Fernández, Miriam; Arboleda Baena, Clara María; Pérez Matus, Alejandro A.; Finke, Randy
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    Diel variability in the vertical distribution of coastal barnacle larvae in the Bay of Cartagena, Chile
    (2023) Bonicelli, Jessica; Jeneral, María J.; Bularz, Bryan; Weidberg, Nicolas; Plummer, Katalin Andra; Calderon Rivera, Ricardo Alonso; Cifuentes, Ursula; Alarcón, Darly; Navarrete Campos, Sergio Andrés
    Abstract Background Vertical distribution of zooplankton is an important biological factor that can modulate zooplankton transport, dispersal, and survival in the ocean. Seawater temperature and the associated formation of a thermocline can affect the spatial distribution of organisms in the water column and possibly modulate larval vertical distribution in coastal waters. In this study, we examined larval vertical distribution over small spatial scales where environmental conditions could exhibit strong and fairly predictable variability. Methods Diel variation in vertical distributions of barnacle larvae across the thermocline was characterized within the Bay of Cartagena of central Chile. Two intensive 21- and 24-h surveys were conducted in the northern (ECIM) and southern (CTGN) extremes of the bay in summer 2016 and spring 2017. In each survey, vertical tows were conducted at both sites every 3 h above and below the thermocline. Results During summer 2016, larval vertical distribution differed between taxa (balanids and verrucids), barnacle stages (nauplii, cyprids), and sites within the bay. Of all taxa analyzed Balanid nauplii at ECIM were more abundant in the bottom layer during the day and at the surface during the night, suggesting they can control their vertical distribution and follow a diel pattern.Acording to the results all barnacle larvae were found in diferent positions in the water column between day and night during periods of high stratification in this survey.. In spring 2017 all barnacle larvae were confined to the upper layer, despite the strength of stratification, potentially as a result of the intrusion of hypoxic water (< 2 mL L−1) at the bottom, which reached up to around 5 m deep. Conclusions We conclude that diel vertical distribution is not uniform across different barnacle larvae taxa and stages within the Bay of Cartagena and is not affected by stratification. Of all the taxa analyzed, only balanid nauplii showed a pattern of diel vertical migration across the thermocline under certain hydrographic conditions.
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    Macrobenthic communities in a shallow normoxia to hypoxia gradient in the Humboldt upwelling ecosystem
    (2018) Fajardo, Maritza; Andrade, Diego; Bonicelli, Jessica; Bon, Melanie; Gomez, Gonzalo; Riascos, Jose M.; Pacheco, Aldo S.
    Hypoxia is one of the most important stressors affecting the health conditions of coastal eco-systems. In highly productive ecosystems such as the Humboldt Current ecosystem, the oxygen minimum zone is an important abiotic factor modulating the structure of benthic communities over the continental shelf. Herein, we study soft-bottom macrobenthic communities along a depth gradient-at 10, 20, 30 and 50 m-for two years to understand how hypoxia affects the structure of shallow communities at two sites in Mejillones Bay (23 degrees S) in northern Chile. We test the hypothesis that, during months with shallow hypoxic zones, community structure will be much more dissimilar, thereby depicting a clear structural gradient with depth and correlated abiotic variables (e.g. organic matter, temperature and salinity). Likewise, during conditions of deeper hypoxic zones, communities will be similar among habitats as they could develop structure via succession in conditions with less stress. Throughout the sampling period (October 2015 to October 2017), the water column was hypoxic (from 2 to 0.5ml/l O-2) most of the time, reaching shallow depths of 20 to 10 m. Only one episode of oxygenation was detected in June 2016, where normoxia (> 2ml/l O-2) reached down to 50 m. The structure of the communities depicted a clear pattern of increasing dissimilarity from shallow normoxic and deep hypoxic habitat. This pattern was persistent throughout time despite the occurrence of an oxygenation episode. Contrasting species abundance and biomass distribution explained the gradient in structure, arguably reflecting variable levels of hypoxia adaptation, i.e. few polychaetes such as Magelona physilia and Paraprionospio pinnata were only located in low oxygen habitats. The multivariable dispersion of community composition as a proxy of beta diversity decreased significantly with depth, suggesting loss of community structure and variability when transitioning from normoxic to hypoxic conditions. Our results show the presence of semi-permanent shallow hypoxia at Mejillones Bay, constraining diverse and more variable communities at a very shallow depth (10-20 m). These results must be considered in the context of the current decline of dissolved oxygen in most oceans and coastal regions and their impact on seabed biota.