José M. Fariña

Can conservation biologists rely on established community structure rules to manage novel systems? … Not in salt marshes

We experimentally examined plant zonation in a previously unstudied Chilean salt marsh system to test the generality of mechanisms generating zonation of plants across intertidal stress gradients. Vertical zonation in this system is striking. The low-lying clonal succulent, Sarcocornia fruticosa, dominates the daily flooded low marsh, while intermediate elevations are dominated by the much taller Spartina densiflora. Irregularly flooded higher elevations are dominated by Schoenoplectus californicus, with the small forb, Selliera radicans, found associated with Schoenoplectus at its base. Transplant studies of all four species into each zone both with and without competition revealed the mechanisms driving these striking patterns in plant segregation. In the regularly flooded low marsh, Sarcocornia and Spartina grow in the zone that they normally dominate and are displaced when reciprocally transplanted between zones with neighbors, but without neighbors they grow well in each others zone. Thus, interspecific competition alone generates low marsh zonation as in some mediterranean marshes, but differently than most of the Californian marshes where physical stress is the dominant factor. In contrast, mechanisms generating high marsh patterns are similar to New England marshes. Schoenoplectus dies when transplanted to lower elevations with or without neighbors and thus is limited from the low marsh by physical stress, while Selliera grows best associated with Schoenoplectus, which shades and ameliorates potentially limiting desiccation stress. These results reveal that mechanisms driving community organization across environmental stress gradients, while generally similar among systems, cannot be directly extrapolated to unstudied systems. This finding has important implications for ecosystem conservation because it suggests that the mechanistic understanding of pattern generation necessary to manage and restore specific communities in novel habitats cannot rely exclusively on results from similar systems, and it identifies a critical role for experimental ecology in the management and conservation of natural systems and the services they provide.

Osmoregulatory capacity and the ability to use marine food sources in two coastal songbirds (Cinclodes: Furnariidae) along a latitudinal gradient

Cinclodes nigrofumosus and C. oustaleti are two closely related songbirds that inhabit the northern Chilean coast during the austral fall and winter.This stretch spans a dramatic north to south latitudinal gradient in rainfall and temperature. Whereas C. nigrofumosus lives exclusively on coastal environments, C. oustaleti shifts seasonally from coastal environments to inland freshwater ones. We used the δ13C of these two species’ tissues to investigate whether the reliance on marine versus terrestrial sources varied from the hyper-arid north to the wet south. We also investigated latitudinal variation in the renal traits that mediate how these birds cope with dehydration and a salty marine diet. Both species increased the incorporation of terrestrial carbon, as measured by δ13C, as terrestrial productivity increased southwards. However, C. nigrofumosus had consistently more positive (i.e. more marine) and less variable δ13C values than C. oustaleti. The osmoregulatory traits of both species varied with latitude as well. Urine osmolality decreased from extremely high values in the north to moderate values in the south, while C. nigrofumosus produced more concentrated urine than C. oustaleti. In both species, the proportion of kidney devoted to medullary tissue decreased from north to south, and kidney size increased significantly with latitude. Cinclodes nigrofumosus had larger kidneys with larger proportions of medullary tissue than C. oustaleti. C. nigrofumosus and C. oustaleti are terrestrial organisms subsidized by a rich marine environment where it is adjacent to an unproductive terrestrial. Variation in the reliance on marine food sources seems to be accompanied by adjustments in the osmoregulatory mechanisms used by these birds to cope with salt and dehydration.

Temporal variation in the diversity and cover of sessile species in rocky intertidal communities affected by copper mine tailings in northern Chile.

Several coastal rocky shores in the northern Chile have been affected by the discharges of copper mine tailings. In spite of this, the temporal and spatial variation on the diversity and composition of their intertidal benthic communities has scarcely been studied. The objectives of the present study were to analyse and to compare quantitatively the temporal variation on the diversity, cover and composition of sessile species in rocky intertidal benthic communities of the northern Chilean coast, in relation to the presence of copper mine tailings. The results show that the drastic reduction on the sessile species diversity and the monopolization of the substrate exerted by the green algae Enteromorpha compressa, are common and permanent features of the intertidal rocky shores affected by copper mine tailings. Such spatial (between sites) and temporal (seasonal) variation of these changes has been associated with the relative concentrations of trace metals and inorganic particles of the mining wastes. Our results suggest that the mechanical effects of resuspended and settling tailings are a more likely cause.

Bromeliad growth and stoichiometry: responses to atmospheric nutrient supply in fog-dependent ecosystems of the hyper-arid Atacama Desert, Chile

Carbon, nitrogen, and phosphorus (C, N, P) stoichiometry influences the growth of plants and nutrient cycling within ecosystems. Indeed, elemental ratios are used as an index for functional differences between plants and their responses to natural or anthropogenic variations in nutrient supply. We investigated the variation in growth and elemental content of the rootless terrestrial bromeliad Tillandsia landbeckii, which obtains its moisture, and likely its nutrients, from coastal fogs in the Atacama Desert. We assessed (1) how fog nutrient supply influences plant growth and stoichiometry and (2) the response of plant growth and stoichiometry to variations in nutrient supply by using reciprocal transplants. We hypothesized that T. landbeckii should exhibit physiological and biochemical plastic responses commensurate with nutrient supply from atmospheric deposition. In the case of the Atacama Desert, nutrient supply from fog is variable over space and time, which suggests a relatively high variation in the growth and elemental content of atmospheric bromeliads. We found that the nutrient content of T. landbeckii showed high spatio-temporal variability, driven partially by fog nutrient deposition but also by plant growth rates. Reciprocal transplant experiments showed that transplanted individuals converged to similar nutrient content, growth rates, and leaf production of resident plants at each site, reflecting local nutrient availability. Although plant nutrient content did not exactly match the relative supply of N and P, our results suggest that atmospheric nutrient supply is a dominant driver of plant growth and stoichiometry. In fact, our results indicate that N uptake by T. landbeckii plants depends more on N supplied by fog, whereas P uptake is mainly regulated by within-plant nutrient demand for growth. Overall, these findings indicate that variation in fog nutrient supply exerts a strong control over growth and nutrient dynamics of atmospheric plants, which are ubiquitous across fog-dominated ecosystems.

Terrestrial birds living on marine environments: does dietary composition of Cinclodes nigrofumosus (Passeriformes: Furnariidae) predict their osmotic load?

Alimentarse de presas marinas representa un desafio para aves paseriformes que no poseen glandula de la sal y tienen una habilidad limitada para concentrar orina. Para reducir la carga osmotica asociada al consumo de presas marinas estas aves podrian optar por incluir presas con bajas concentraciones salinas en su dieta y/o aumentar la ingestion de agua dulce. El genero Cinclodes es particular entre los paseriformes debido a que incluye especies que habitan riberas de lagos, rios y costas marinas. Analizamos la dieta de Cinclodes nigrofumosus y exploramos la posible relacion entre la composicion de esta y la carga salina en dos sitios costeros de Chile, uno mesico y otro arido. En este estudio planteamos que desde una perspectiva biogeografica, la disponibilidad de agua dulce es un factor que determina la relacion entre la composicion dietaria y la carga osmotica de esta especie. Nuestro analisis de abundancia y distribucion de presas indico que la dieta de C. nigrofumosus esta compuesta principalmente por presas marinas independiente de la disponibilidad de insectos terrestres en ambos sitios. La osmolalidad del contenido estomacal fue mayor en el sitio arido, pero no se correlaciono con el tipo de presas consumidas, sugiriendo que Cinclodes evita una alta carga osmotica a traves de ingerir agua dulce cuando esta disponible. Estos resultados apoyan que una restriccion fisiologica seria el factor que modula la amplitud de nicho en Cinclodes

THE “IDIOSYNCRATIC” EFFECT OF A “SENTINEL” SPECIES ON CONTAMINATED ROCKY INTERTIDAL COMMUNITIES

Depending on their biological characteristics, some species can exert strong (idiosyncratic) effects on ecosystem process. Human impacts on biological communities are related to biodiversity declines but also with species shifts and replacements. In northern Chile, the occurrence of copper mine tailings in seawater is associated with a decrease in the number of sessile species and with rocky intertidal substrate monopolization by one sentinel species, the green ephemeral-opportunistic algae Entermorpha compressa. In spite of these changes, several consumer species persist on the contaminated sites. In this study, we test the hypothesis that changes in benthic species dominance and composition is associated with an increase in productivity, which affects intertidal consumer abundance, biomass, and/or diversity. We compare benthic species richness, composition, and productivity as well as the abundance, diversity, and diet of consumer species on contaminated and noncontaminated sites. Our results show that ...

Distribución espacial de la macrofauna en una playa expuesta de Chile central: efectos de la morfodinámica intermareal

Although spatial heterogeneity (patchiness) is common in sandy beaches, it has been poorly studied. Patchiness in sandy beach populations has been well documented, but its explanation is usually unknown. In the present paper we propose that the spatial variability of intertidal morphodynamic affect the macrofauna spatial distribution (zonation) and abundance along the beach. We analyzed in a sandy beach of central Chile the effects of the spatial variability of the intertidal morphodynamic, upon macrofaunal density and zonation, by comparing sites of contrasting morphology: bays and horns. In comparison, bays were zones of gentler slope, greater intertidal amplitude, lesser swash frequency, and have lesser percentage of coarse sand than horns. In general, the macrofaunal species tend to be more abundant on bays, but only Excirolana braziliensis showed significantly differences. Accordingly with this general trend, the total macrofauna density was significantly higher on bays. By contrast, the species richness per transect was not different between bays and horns. The species of the macrofauna showed evident zonation patterns, which were demonstrated by important differences of abundance among intertidal levels (i.e., high, mid, low). The zonation of the macrofauna, as well as the zonation patterns of Excirolana hirsuticauda, Orchestoidea tuberculata and Euzonus heterocirrus differed between bays and horns. We concluded that the spatial variability of abundance and zonation alongshore, would be associated in some species with variations in the intertidal morphodynamic.

Effect of drift kelp on the spatial distribution pattern of the sea urchin Tetrapygus niger: a geostatistical approach

Geostatistical analysis was used to investigate the effect of drift kelp on the spatial distribution of the sea urchin Tetrapygus niger . The positions of all sea urchins were mapped in four experimental plots in the rocky intertidal zone of the central Chilean coast. When drift macroalgae were added, the sea urchins left the substratum irregularities, increased in number inside the experimental plots, and tended to form a dense aggregation around the kelp. After the drift macroalgae was removed, the aggregations disappeared and the sea urchins returned to the depressions and/or interstices of the substratum. The results suggest that the influx of drift kelp is the triggering factor in the formation of dense aggregations of this species.

Ecología trófica de Girella laevifrons (Pisces: Kyphosidae) en zonas intermareales rocosas del norte de Chile afectadas y no afectadas por contaminantes derivados de la minería del cobre

La zonas intermareales de localidades de la costa norte de Chile afectadas por contaminantes derivados de la mineria del cobre, presentan una diversidad de especies sesiles menor que las localidades no afectadas. Girella laevifrons es un pez altamente representado en zonas intermareales rocosas del norte de Chile. En el presente trabajo se analiza y compara la ecologia trofica de esta especie, en relacion con las diferencias en la composicion de especies sesiles de sitios contaminados y no contaminados. Los resultados muestran diferencias significativas en la composicion trofica de los ejemplares presentes en los sitios afectados y no afectados. Dentro de los sitios afectados, se observan diferencias en los tamanos y en las concentraciones de cobre corporales, las cuales pueden estar relacionadas directamente con la disponibilidad de alimento e indirectamente con interacciones con otros organismos intermareales

Bottom-up and top-down human impacts interact to affect a protected coastal Chilean marsh.

Many ecosystems, even in protected areas, experience multiple anthropogenic impacts. While anthropogenic modification of bottom-up (e.g., eutrophication) and top-down (e.g., livestock grazing) forcing often co-occurs, whether these factors counteract or have additive or synergistic effects on ecosystems is poorly understood. In a Chilean bio-reserve, we examined the interactive impacts of eutrophication and illegal livestock grazing on plant growth with a 4-yr fertilization by cattle exclusion experiment. Cattle grazing generally decreased plant biomass, but had synergistic, additive, and antagonistic interactions with fertilization in the low, middle, and high marsh zones, respectively. In the low marsh, fertilization increased plant biomass by 112%, cattle grazing decreased it by 96%, and together they decreased plant biomass by 77%. In the middle marsh, fertilization increased plant biomass by 47%, cattle grazing decreased it by 37%, and together they did not affect plant biomass. In the high marsh, fertilization and cattle grazing decreased plant biomass by 81% and 92%, respectively, but together they increased plant biomass by 42%. These interactions were also found to be species specific. Different responses of plants to fertilization and cattle grazing were likely responsible for these variable interactions. Thus, common bottom-up and top-down human impacts can interact in different ways to affect communities even within a single ecosystem. Incorporating this knowledge into conservation actions will improve ecosystem management in a time when ecosystems are increasingly challenged by multiple interacting human impacts.