Patricio De los Ríos Escalante

Salinity effects on the abundance of Boeckella poopoensis (Copepoda, Calanoida) in saline ponds in the Atacama desert, northern Chile

[The calanoid copepod, Boeckella poopoensis Marsh, 1906 inhabits shallow saline ponds located in the Andes mountains in Argentina, Bolivia, Chile, and Peru, as well as in the plains of southern Argentina. The species is halophilic and can tolerate salinity levels of 1 to 90 ppt. This paper describes the relative abundance of the species in shallow mountain ponds in northern Chile from 23° to 27° S. A direct correlation was observed between salinity and the relative abundance of B. poopoensis (r2 = 0.4139), and between 45 and 90 ppt S the species was found to be dominant in zooplankton assemblages. Crustacean species richness at the sites studied showed a significant, inverse trend with salinity (r2 = 0.7329), and this trend became even stronger (r2 = 0.7681) when data previously published for the Bolivian Andean plateau were included. Ecological and biogeographical issues related with these results are discussed. El copepodo calanoideo Boeckella poopoensis Marsh, 1906 vive en lagunas salinas poco profundas localizadas en el altiplano Andino de Argentina, Bolivia, Chile y Peru, y en el sur de Argentina. Esta especie es marcadamente halofilica, y tolera salinidades entre 1 y 90 g/l, estos habitats tienen una pobre riqueza especifica de crustaceos zooplanctonicos. Este estudio describe la abundancia relativa de esta especie en lagunas poco profundas de montana en el norte de Chile, entre los 23 y 27 grados sur de latitud. Se observo una relacion directa notoria entre la salinidad y la abundancia relativa de B. poopoensis (r2 = 0.4139), encontrandose practicamente esta especie como habitante exclusivo a salinidades superiores entre 45 g/l y 90 g/l, lo que coincide con las descripciones de la literatura. La riqueza especifica de especies de crustaceos presento una relacion inversa notoria con la salinidad en los sitios estudiados (r2 = 0.7329), lo cual fue mas robusto al incorporar informacion publicada para el Altiplano de Bolivia (r2 = 0.7681). En este estudio se discutieron implicancias ecologicas y biogeograficas relacionadas con los resultados observados., The calanoid copepod, Boeckella poopoensis Marsh, 1906 inhabits shallow saline ponds located in the Andes mountains in Argentina, Bolivia, Chile, and Peru, as well as in the plains of southern Argentina. The species is halophilic and can tolerate salinity levels of 1 to 90 ppt. This paper describes the relative abundance of the species in shallow mountain ponds in northern Chile from 23° to 27° S. A direct correlation was observed between salinity and the relative abundance of B. poopoensis (r2 = 0.4139), and between 45 and 90 ppt S the species was found to be dominant in zooplankton assemblages. Crustacean species richness at the sites studied showed a significant, inverse trend with salinity (r2 = 0.7329), and this trend became even stronger (r2 = 0.7681) when data previously published for the Bolivian Andean plateau were included. Ecological and biogeographical issues related with these results are discussed. El copepodo calanoideo Boeckella poopoensis Marsh, 1906 vive en lagunas salinas poco profundas localizadas en el altiplano Andino de Argentina, Bolivia, Chile y Peru, y en el sur de Argentina. Esta especie es marcadamente halofilica, y tolera salinidades entre 1 y 90 g/l, estos habitats tienen una pobre riqueza especifica de crustaceos zooplanctonicos. Este estudio describe la abundancia relativa de esta especie en lagunas poco profundas de montana en el norte de Chile, entre los 23 y 27 grados sur de latitud. Se observo una relacion directa notoria entre la salinidad y la abundancia relativa de B. poopoensis (r2 = 0.4139), encontrandose practicamente esta especie como habitante exclusivo a salinidades superiores entre 45 g/l y 90 g/l, lo que coincide con las descripciones de la literatura. La riqueza especifica de especies de crustaceos presento una relacion inversa notoria con la salinidad en los sitios estudiados (r2 = 0.7329), lo cual fue mas robusto al incorporar informacion publicada para el Altiplano de Bolivia (r2 = 0.7681). En este estudio se discutieron implicancias ecologicas y biogeograficas relacionadas con los resultados observados.]

The use of null models to explain crustacean zooplankton associations in shallow water bodies of the Magellan region, Chile

Southern Patagonia is characterized by the presence of numerous shallow ponds with variable trophic and conductivity conditions, and a relatively high species richness of Crustacea. In the present study, published information and data collected in field work on shallow ponds in the Magellan region was reviewed and analysed using co-occurrence of null models, with the aim to determine potential random factors as regulators on crustacean zooplankton assemblages, using a presence-absence matrix. The results of C-score analysis revealed the existence of non-random effects mainly in data collected in 1989-1990 for Torres del Paine National Park, and in data on coastal shallow ponds close to Punta Arenas, collected in October 2006. A different situation is reported for shallow ponds located in other zones of the Magellan region, including also some in the Torres del Paine National Park collected in October 2001, and for shallow ponds close to Porvenir on Tierra del Fuego Island, collected in April 2007. The existence of non-random effects was probably due to markedly different zooplankton assemblages, assumed to be caused mainly by the conductivity gradient and trophic level. Random effects can probably be explained by the condition that a few species occur practically at all localities studied, in many of which species richness is very low. This obviously means the variability in species composition is very limited, yielding similar zooplankton assemblages in the many ponds sampled. Ecological and biogeographical topics are also discussed. La zona sur de la Patagonia se caracteriza por la presencia de numerosas lagunas poco profundas, con diferentes condiciones troficas y de conductividad y relativamente alta riqueza de especies. En el presente estudio se considero informacion publicada y datos colectados en trabajos de campo en la region de Magallanes, esta informacion fue analizada sobre la base de modelos nulos de co-ocurrencia, con el objetivo de determinar potenciales efectos aleatorios en la composicion de los ensambles de crustaceos zooplanctonicos, usando una matriz de presencia y ausencia. Los resultados del factor C-score, revelaron la no existencia de efectos aleatorios principalmente en datos colectados para el Parque Nacional Torres del Paine en 1989-1990, y lagunas costeras cercanas a Punta Arenas en Octubre de 2006. Una situacion diferente se reporto en lagunas superficiales en diferentes lagunas de la region de Magallanes, incluido el Parque Nacional Torres del Paine colectados en Octubre de 2001, y lagunas superficiales cercanas a Porvenir en la Isla de Tierra del Fuego colectadas en Abril de 2007. La ausencia de efectos aleatorios se debio probablemente al gradiente de conductividad y de condiciones troficas. Mientras que la existencia de efectos aleatorios, se debio probablemente a pocas especies que se encontraron en practicamente todos las localidades estudiadas, muchas de las cuales tuvieron bajo numero de especies, esto obviamente significa que la variabilidad en composicion de especies es limitada, obteniendose similares patrones en las asociaciones de especies zooplanctonicas en los sitios estudiados. Se discutieron aspectos ecologicos y biogeograficos en el presente estudio.

A checklist of marine crustaceans known from Easter Island

Easter Island constitutes the most isolated terrestrial ecosystem in the Pacific Ocean. The fauna of that site is interesting from a biogeographical point of view because species from Pacific Asia and South America can be found there, as well as endemic species. The aim of the present study was to compile a literature review of published records of marine Crustacea from Easter Island with the emphasis on the heterogeneity in habitats reported for each species. The results confirm the presence of species otherwise known from Pacific Asia, South America, as well as the expected endemic species. In spite of the little information that is generally provided in the habitat records for most species, it may still be possible to find a marked heterogeneity of ecosystems, together generating a complex system that warrants more detailed studies.

Crustacean zooplankton communities in Chiloé Island coastal lakes (42°S, Chile)

The lakes of Chiloe Island have a high dissolved organic carbon concentration (known as “humic”) and show a connection with brackish water. They also display a high species richness of crustacean zooplankton. The aim of the present study is to characterize the potential factors that explain crustacean species richness in Chiloe Island lakes. To that purpose parameters of the abiotic environment were determined. The results of PCA performed on those data revealed the existence of three lakes with high crustacean species richness that are relatively deep, show high nitrogen concentrations, and are located at relatively high altitude. In contrast, there are two lakes with low species richness, high mineral concentration, and situated at low altitude. One of these lowland lakes gives rise to a river effluent to the sea, and it is connected to the other lake; these observations agree with the results of a performed cluster analysis. Nevertheless, the co-occurrence null model analysis revealed the absence of regulator patterns in species associations, which could be explained to the fact that many of the species occur in most of the lakes. These results are markedly different in comparison to Patagonian lakes of Argentina and Chile that have a low crustacean species number.

An update on the global stressors and constraints affecting Daphnia populations in large Chilean Patagonian lakes (39-51°S)

The zooplankton communities in Chilean Patagonian lakes (39-51°S) are characterized by the low presence of daphniid cladocerans, i.e., under conditions of the usual native oligotrophy and, thus, low mineral concentrations. Nevertheless, from some northern Patagonian lakes (39-41°S) a marked abundance of daphniids has been reported. According to the literature, as well as evidence from field observations, the main causes of such marked changes in the local zooplankton assemblages would be changes in phytoplankton quantity and quality, providing increased energetic resources for the zooplankton communities. Such energetic resources might decrease the stress effects of low calcium concentrations, as calcium constitutes an essential nutrient for caparace formation in Daphniidae; in addition, energetic expenses needed to perform vertical migrations due to fish predation and exposure to natural ultraviolet radiation can better be provided for. This is a markedly different situation compared to North Patagonian lakes, where daphniid abundance and number of species are related only to phytoplankton quantity and quality in term of phosphorus/nitrogen molar ratio.

Crustacean zooplankton assemblages in inland waters of southern Patagonia (Alacalufes National Reserve), Chile (49-51°S)

The inland water crustacean communities in southern Chilean Patagonia (46-55°S) are characterized by their marked low species number, and many recurrent species among a wide ecological and geographical gradient, that is due to oligotrophy of lakes and lagoons and the fluvial parameters (i.e., high flow velocities) in rivers. The aim of the present study was to describe the zooplankton communities in lakes and respective outflow river estuaries in Alacalufes National Reserve on islands of Chilean southern Patagonia (49-51°S). Species abundance and presence/absence were considered. The results obtained revealed the presence of a low number of species and also multiple sites in which zooplankton was not recorded at all. This is probably due the low zooplankton diversity of cold lakes at these high latitudes and the often turbulent flow of the outflow rivers studied.

Observaciones mediante modelos nulos de comunidades zooplanctónicas en lagunas temporales costeras de las Dunas de Puaucho (38º S, Chile)

El zooplancton lacustre chileno se caracteriza por un alto predominio de copepodos calanoideos y bajo numero de especies, lo que esta asociado principalmente a condiciones de oligotrofia. El presente estudio es una primera descripcion de la comunidad de crustaceos zooplanctonicos y litorales en lagunas temporales en la zona costera de Puaucho mediante el uso de modelos nulos de co-ocurrencia de especies y sobreposicion de nicho. Los resultados del modelo de co-ocurrencia de especies indican que las asociaciones de estas son aleatorias, mientras que el analisis de sobreposicion de nicho indica estos no se sobreponen. Los resultados concordarian con descripciones similares para lagos de la Patagonia de Argentina y Chile.

Culture of native species of zooplanktonic crustaceans: Tumeodiaptomus diabolicus (Brehm, 1935) from northern Patagonian lakes (Chile)

The inland waters of Chile hold endemic species of crustaceans, and these habitats are threatened at present due to pollution as a result of human activities. Until now, the environmental studies performed have not considered native species for evaluating environmental risks. The aim of the present study was to do a first culture experiment with the freshwater copepod Tumeodiaoptomus diabolicus that inhabits central and northern Chilean Patagonian lakes. The copepods were cultured under two dietary regimes, i.e., a diet of microalgae and an artificial diet. The experiment was conducted over 12 days, and the maximum growth was obtained with the artificial diet. The present results would agree with similar results obtained for pseudodiaptomid copepods, that are massively used for aquaculture activities. In accordance with the obtained results and published data in the literature, T. diabolicus culture could be relatively easily done, and would thus qualify as an assay for investigating environmental conditions.

Calanoid copepods in central Chilean and Chilean Patagonian lakes (33-55'S, Chile), probable ecological key role in pelagic environments

The Patagonian lakes (38-55°S) are characterized by their marked oligotrophy, low number of species of crustacean zooplankton, and a marked predominance of calanoid copepods. Within this context, we considered that a review about the ecology of the zooplankton in central and southern Chilean lakes would be useful, aiming to understand the ecological importance of this group. Data obtained from the literature for freshwater bodies in central and southern Chilean lakes were analysed. In addition, data from various bays with widely differing trophic status in Llanquihue Lake were examined. The results revealed the existence of originally pristine and oligotrophic sites, all with a low number of species and marked calanoid dominance. However, in northern Patagonia there are many lakes in which human intervention has caused an increase in phytoplankton activity, with a consequent replacement of calanoid copepods by daphniid cladocerans. Other important factors that could affect the zooplankton community would be fish predation, which is due to generate a decrease in large-bodied groups of zooplankton; and stress due to exposure to natural ultraviolet radiation. Ecological, biogeographical, and evolutionary topics are discussed within the framework described.

First ecological observations on littoral marine decapods of rocky shores of Easter Island

Easter Island is the most isolated and remote territory of the Pacific Ocean, situated at least 2250 km away from the Pitcairn Islands, and at 3500 km from the South American continent (Fernandez et al., 2014; De los Ríos-Escalante & Ibáñez-Arancibia, 2016). There are many literature reports that mention species composition in marine environments on Easter Island, but most studies do not report sufficient details about the sites of collection, and neither is there usually any relevant information about the local community structures in the habitats sampled (DiSalvo et al., 1988; Goddard, 2003; Kensley, 2003; Coloma et al., 2004; Retamal, 2004; Fernandez et al., 2014). The first descriptions of ecological structure for marine environments mentioned species composition in molluscs (Coloma et al., 2004), copepods (Goddard, 2003), and decapods (Retamal, 2004). These respective records are all detailed and based on the presence/absence of species in certain bays of limited extension, but they also are restricted in the sense that they constitute short-term field work. The only, and indeed unique, study based on absolute abundances was done about species associations between crabs of the family Grapsidae (De los Ríos-Escalante, 2011). On the basis of ecological community theory, a heterogeneous and stable habitat would provide several advantages for the establishment of a more speciesrich community (Loureau, 2010). Accordingly, Easter Island can be expected to provide more, and more diverse, microhabitats that thus most probably will allow the presence of different communities, all with their own specific composition (Goddard, 2003; Retamal, 2004; De los Ríos-Escalante, 2011). This would explain