Papers by Rodrigo J Gonçalves
Earth Systems and Environment, 2022
Unfortunately, in the original publication one of the coauthor name is published wrongly as Rrodr... more Unfortunately, in the original publication one of the coauthor name is published wrongly as Rrodrigo Gonçalves, it should be Rodrigo J. Gonçalves. We regret the inconvenience caused. The original article has been updated.
Plankton Ecology of the Southwestern Atlantic, 2018
In aquatic ecosystems, global change encompasses human-induced variations in the upper layer of t... more In aquatic ecosystems, global change encompasses human-induced variations in the upper layer of the water column, where most of the carbon fixation takes place. These changes include increments of exposure to solar UV radiation, mean temperature of surface seawater, ocean acidification and variations in nutrient concentrations. These factors are well known to affect plankton ecosystems, although not all organisms are equally affected. In addition, many times these factors interact so that the final results are not always additive or synergistic as expected. Finally, indirect effects (e.g. through trophic interactions) are often more pronounced than direct ones (e.g. survival or growth), which in some cases mask overall and long-term expected ecological shifts in plankton communities. We review the main contributions in this field from the Atlantic coast of South America and discuss in a final section what have we learned and what is still unknown as global changes seem to be here to stay.
Oceanography, 2018
Patagonian Dust as a Source of Macronutrients in the Southwest Atlantic Ocean ABSTRACT. The role ... more Patagonian Dust as a Source of Macronutrients in the Southwest Atlantic Ocean ABSTRACT. The role of Patagonian wind-borne dust as a source of macronutrients to the surface waters of the Southwest Atlantic Ocean was evaluated for the first time. During spring 2016, a series of experiments with dust was conducted to evaluate the dynamics of macronutrient dissolution in seawater. The results showed a differential contribution of macronutrients to seawater depending on the dust source and the amount added. Addition of a conservative amount of Patagonian dust to the seawater contributed nitrate (NO 3 −) and silicic acid (Si(OH) 4), but not phosphate (PO 4 3-). Additional dust input to the system resulted in higher macronutrient concentrations. Particles collected from a nearby burned field did not contribute any macronutrients to the seawater. Thus, each dust event may affect biological productivity differently, depending on the source of the particles. Dissolution experiments suggest that macronutrients from dust are available immediately after particle deposition on the sea surface. The study includes field measurements of macronutrient concentrations before and after a dust storm at three nearshore marine stations. The data are consistent with macronutrient increase after the storms. Dust storms could become a very important source of nutrients to the ocean in future global warming scenarios.
Ciencias Marinas, 2016
The aim of this study is to analyze the annual zooplankton succession at a coastal station in Pat... more The aim of this study is to analyze the annual zooplankton succession at a coastal station in Patagonia (Argentina), with special emphasis on copepods and their potential preys, using solar radiation and temperature as environmental factors. The annual plankton cycle exhibited autumn/winter and spring/summer phases. During the autumn/winter phase, low temperature and radiation were correlated with higher diatom abundance and copepod diversity. This period was characterized by a dominant classical herbivorous food web in which the large copepod Calanoides carinatus dominated the community. On the contrary, during the spring/summer period, with high radiation and temperature levels, flagellates were the dominant food available for zooplankton and correlated with smaller species of copepods such as the harpacticoid Euterpina acutifrons. Also, intensive reproduction of the small copepods E. acutifrons and Paracalanus parvus occurred mainly in summer. On the other hand, high species dive...
ICES Journal of Marine Science, 2017
The effects of ultraviolet radiation (UVR) under future expected conditions of acidification and ... more The effects of ultraviolet radiation (UVR) under future expected conditions of acidification and increase in nutrient inputs were studied on a post-bloom phytoplankton and bacterioplankton community of Patagonian coastal waters. We performed an experiment using microcosms where two environmental conditions were mimicked using a cluster approach: present (ambient nutrients and pH) and future (increased nutrients and acidification), and acclimating the samples for five days to two radiation treatments (full solar radiation [+UVR] and exclusion of UVR [–UVR]). We evaluated the short-term (hours) sensitivity of the community to solar UVR through chlorophyll a fluorescence parameters (e.g. the effective photochemical quantum yield of PSII [ΦPSII]) at the beginning, at the mid-point and at the end of the acclimation period. Primary production and heterotrophic bacterial production (HBP) were determined, and biological weighting functions were calculated, at the beginning and at the end of...
Annual Review of Marine Science, 2016
The size of an individual organism is a key trait to characterize its physiology and feeding ecol... more The size of an individual organism is a key trait to characterize its physiology and feeding ecology. Size-based scaling laws may have a limited size range of validity or undergo a transition from one scaling exponent to another at some characteristic size. We collate and review data on size-based scaling laws for resource acquisition, mobility, sensory range, and progeny size for all pelagic marine life, from bacteria to whales. Further, we review and develop simple theoretical arguments for observed scaling laws and the characteristic sizes of a change or breakdown of power laws. We divide life in the ocean into seven major realms based on trophic strategy, physiology, and life history strategy. Such a categorization represents a move away from a taxonomically oriented description toward a trait-based description of life in the oceans. Finally, we discuss life forms that transgress the simple size-based rules and identify unanswered questions.
Marine Ecology Progress Series, 2014
We examined size-dependent prey detection and prey capture in free-swimming Temora longicornis us... more We examined size-dependent prey detection and prey capture in free-swimming Temora longicornis using video observations, particle image velocimetry (PIV), and bottle incubations with phytoplankton prey sizes within the range 6−60 µm equivalent spherical diameter (ESD). T. longicornis generates feeding currents by oscillating its appendages at about 25 Hz. Prey cells >10 µm ESD are perceived and captured individually. A capture response was elicited when prey was touched by (or within a few cell radii from) the setae on the feeding appendages. The extension of the setae defines the prey encounter cross section, which is therefore independent of prey size. The flux of water through the encounter area, estimated from PIV, was ca. 150 ml ind. −1 d −1 , which represents the maximum possible clearance rates and was similar to that estimated in incubation experiments. However, while the detection probability was nearly 100% for cells >10−15 µm, it declined rapidly for smaller cells. Conversely, the probability that a cell which elicited a capture response was actually ingested declined with increased cell size, from nearly 100% for small cells, to ~0% for the largest cells examined. The resulting prey size spectrum, predicted as the product of the cell-size-specific encounter rates and capture probabilities, was domeshaped, with a maximum around 20−30 µm ESD. The prey size spectrum from incubation experiments had a similar shape and an optimum range of 30−50 µm ESD. The mechanistic underpinning of the prey size spectrum suggested here deviates from previous descriptions mainly in the mechanism and range of prey detection.
Proceedings of the National Academy of Sciences of the United States of America, 2014
Interactions between planktonic organisms, such as detection of prey, predators, and mates, are o... more Interactions between planktonic organisms, such as detection of prey, predators, and mates, are often mediated by fluid signals. Consequently, many plankton predators perceive their prey from the fluid disturbances that it generates when it feeds and swims. Zooplankton should therefore seek to minimize the fluid disturbance that they produce. By means of particle image velocimetry, we describe the fluid disturbances produced by feeding and swimming in zooplankton with diverse propulsion mechanisms and ranging from 10-μm flagellates to greater than millimetersized copepods. We show that zooplankton, in which feeding and swimming are separate processes, produce flow disturbances during swimming with a much faster spatial attenuation (velocity u varies with distance r as u ∝ r −3 to r −4) than that produced by zooplankton for which feeding and propulsion are the same process (u ∝ r −1 to r −2). As a result, the spatial extension of the fluid disturbance produced by swimmers is an order of magnitude smaller than that produced by feeders at similar Reynolds numbers. The "quiet" propulsion of swimmers is achieved either through swimming erratically by short-lasting power strokes, generating viscous vortex rings, or by "breast-stroke swimming." Both produce rapidly attenuating flows. The more "noisy" swimming of those that are constrained by a need to simultaneously feed is due to constantly beating flagella or appendages that are positioned either anteriorly or posteriorly on the (cell) body. These patterns transcend differences in size and taxonomy and have thus evolved multiple times, suggesting a strong selective pressure to minimize predation risk. biological fluid dynamics | optimization Z ooplankters move to feed, find food, and find mates, so
Biomass and Remote Sensing of Biomass, 2011
Latin American Journal of Aquatic Research, 2014
Many marine species spend part of their development in upper layers of the water column, where th... more Many marine species spend part of their development in upper layers of the water column, where they may be exposed to solar ultraviolet radiation (UVR). For many of these species, light is one of the key environmental clues which triggers behaviorally-mediated adjustments in vertical distribution. We incubated planktonic larvae of the crab Cyrtograpsus altimanus in column-like aquaria to study their responses with/without UVR (under a solar simulator) and with/without a potential prey (the dinoflagellate Alexandrium tamarense). Their vertical distribution was recorded and used to evaluate the combined effects of UVR and the presence of the dinoflagellate on larval behavior. When UVR was absent, most larvae showed a tendency to swim upwards and to aggregate near the surface, regardless of the dinoflagellate presence. However, UVR inhibited this tendency and induced a repellent effect, which resulted in a more homogeneous vertical distribution of larvae. A. tamarense did not affect the vertical distribution of larvae. These results suggest that UVR-triggered, quick adjustments in vertical distribution might be an important strategy for C. altimanus larvae to cope with high solar radiation, which typically occur during the hatching season.
Journal of Plankton Research, 2014
First larval stage (Zoea I) of the crab Cyrtograpsus altimanus can obtain photoprotective compoun... more First larval stage (Zoea I) of the crab Cyrtograpsus altimanus can obtain photoprotective compounds (PPCs) from their mother (indirect acquisition) and also via feeding on PPC-producers such as phytoplankton (direct acquisition). The bioaccumulation of PPC resulted in higher survival of larvae exposed to ultraviolet radiation (UVR), when comparing larvae with high and low content of PPC. Thus, both ways of acquiring PPC may contribute to maximize survival of Zoea I when they are exposed to natural UVR.
Ecología …, 2010
Recibido: 27 de noviembre de 2009; Fin de arbitraje: 23 de abril de 2010; Revisión recibida: 6 de... more Recibido: 27 de noviembre de 2009; Fin de arbitraje: 23 de abril de 2010; Revisión recibida: 6 de mayo de 2010; Aceptado: 8 de mayo de 2010 ... Ecología Austral 20:129-153. Agosto 2010 Asociación Argentina de Ecología ... Responses of plankton and fish from temperate ...
Latin American Journal of Aquatic Research, Feb 11, 2011
A natural plankton population from the eutrophic lake Cacique Chiquichano, in the Argentine Patag... more A natural plankton population from the eutrophic lake Cacique Chiquichano, in the Argentine Patagonia, was monitored for one year to evaluate changes in photosynthetic parameters as a result of exposure to ultraviolet radiation (UVR, 280-400 nm), grazer abundance, and the taxonomic composition of the phytoplankton community. Both physical (temperature, solar radiation) and biological (grazers, taxonomic composition, photosynthetic parameters) variables fluctuated throughout the study. Crustacean zooplankton showed alternating dominance between cladocerans (Daphnia spinulata) and copepods (Metacyclops mendocinus). The phytoplankton community underwent concomitant changes throughout the year, with cyanobacteria and diatoms alternately dominating. In addition, although copepod abundance was not significantly related to changes in phytoplankton, the presence of D. spinulata was significant during periods of more transparent water; these periods were dominated by diatoms. On the other hand, cyanobacteria dominated the phytoplankton assemblage when the penetration of solar radiation into the water column was lower. Photosynthetic inhibition due to UVR decreased during the diatom-dominated periods. In contrast, inhibition increased along with the proportion of cyanobacteria, likely as a result of acclimation to low irradiance during the lake's phase of lower transparency. Moreover, the presence of D. spinulata was associated with the increased penetration of solar radiation into the water column, resulting in an indirect increment in the inhibition of cyanobacteria photosynthesis. The results suggest that both solar radiation and grazing abundance strongly influence the dynamics and photosynthetic activity of the phytoplankton in Lake Cacique Chiquichano.
Plankton Ecology of the Southwestern Atlantic
Land-derived dissolved and particulate matter (allochthonous matter) affect pelagic ecosystems by... more Land-derived dissolved and particulate matter (allochthonous matter) affect pelagic ecosystems by changing factors which include light penetration, nutrient availability, substrate concentration, and in general, biogeochemical cycles in the ocean. In a context of growing anthropogenic impact, this material may not only increase its load but also carry toxic substances. Riverine runoff is the most studied mechanism of particulate matter input from the continent to the sea in the southern region of South America where the continental shelf is widest (e.g., Atlantic Patagonia). However, there are other sources of particulate matter which are not affected by rivers in this semiarid region: aeolian material. Winds in this region (notably the Southern Hemisphere westerlies) are the only way continental aeolian material (atmospheric aerosols or “dust”) can reach not only the shelf but even further onto oceanic HNLC (high nutrient–low chlorophyll) regions of the Atlantic Southern Ocean. This potential impact of Patagonian dust beyond the continental shelf attracts the attention of the global climate community, and at the same time, it opens questions about the potential effects of dust in coastal waters. According to previous work and ongoing studies, deposited particles can have significant impacts in the chemical and biological components in the euphotic zone. However the effects of this airborne material in plankton communities of South America are largely unknown, mostly due to the lack of in situ studies and observations. Since the events of dust mobilization, transport, and deposition are expected to increase (due to climate change) and interact with other global change factors such as warming and more intensive land use, the influence of dust input may become more prominent for coastal and oceanic regions of southern South America in the next decades.
Estuarine, Coastal and Shelf Science
Limnology and Oceanography, 2016
We reply to the comments of Paffenh€ ofer and Jiang (2016) who argues that remote chemical prey p... more We reply to the comments of Paffenh€ ofer and Jiang (2016) who argues that remote chemical prey perception is necessary for feeding-current feeding copepods to fulfill their nutritional requirements in a dilute ocean, that remote chemical prey detection may only be observed at very low prey concentrations, and that chemical prey perception is feasible if prey cells release dissolved organic material in short-lasting but intense bursts. We demonstrate that mechanoreception at a very short range is sufficient to sustain a living, even in a dilute ocean. Further, if chemoreception requires that prey cells have short intense leakage burst, only a very small fraction of prey cells would be available to the copepod at any instance in time and, thus would be inefficient at low prey concentration. Finally, we report a few new observations of prey capture in two species of copepods, Temora longicornis and Centropages hamatus, offered a 45-lm sized dinoflagellate at very low concentration. The observed short prey detection distances, up to a few prey cell radii, are consistent with mechanoreception and we argue briefly that near-field mechanoreception is the most likely and common prey perception mechanism in calanoid copepods.
Limnology and Oceanography, 2015
ABSTRACT Feeding-current feeding copepods detect and capture prey individually, but the mechanism... more ABSTRACT Feeding-current feeding copepods detect and capture prey individually, but the mechanism by which nonmotile prey is detected has been unclear. Early reports that copepods detect phytoplankton prey at distances of one body length or more led to the hypothesis that solutes leaking from the prey would be carried to the copepod by the sheared feeding current and arrive prior to the prey, thus allowing the copepod to adjust the feeding current to bring the prey within reach of the feeding appendages. Many subsequent studies have been interpreted assuming this mechanism, which appears currently to be the main accepted view. Here, we review the observations available in the literature and add our own data to show that in most cases the prey, whether phytoplankton cells or inert particles, has to be within a few prey radii from the setae of the feeding appendages to elicit a capture response. We further demonstrate that (1) long-range chemical detection is incompatible with known algal leakage rates and reasonable assumptions of sensitivity, (2) that near-field chemical detection is constrained by diffusion across the boundary layer of the sensor and takes longer than observed near-contact times, and (3) that most reported detection distances are well predicted by models of fluid mechanical signal generation and detection. We conclude that near-field mechanoreception is the common prey detection mode in pelagic copepods. Prey detection distances are thus governed mainly by the reach of the feeding appendages, in contrast to the strong prey size-dependency implied by remote chemical prey detection.
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Papers by Rodrigo J Gonçalves