Heterogeneity of fresh-water Patagonia ecosystems (original) (raw)
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NEW ZEALAND JOURNAL OF MARINE AND FRESHWATER RESEARCH, 2023
Herbivores in wetlands are key organisms that shape the structure and composition of wetland plant communities (algae and vascular plants). The detritus produced by herbivory contributes to nutrient cycling and provides important resources for other organisms in the ecosystem. Due to their importance, we decided to survey a set of 12 seasonal wetlands located in Andean Patagonian forests. We registered the biotic and abiotic variables of each wetland and the diversity and abundance of herbivores. We found two groups of wetlands: short hydroperiod and long hydroperiod. Despite this, the structure of the communities was not related to the hydroperiod length, abundance, or species composition. In particular, the abundance of herbivores was explained by chlorophyll, pH and dissolved oxygen, among others. Their diversity and abundance were (in decreasing order): rotifers, copepods, cladocerans, caddisflies, and amphibians. Probably, the species found in these wetlands are well adapted to different hydroperiod regimens and, even in short hydroperiods, can complete their life cycle. The results found here do not match with the model of hydroperiod gradient; however, other variables not measured here, such as diversity and abundance of aquatic plants or predation by invertebrates, could impact the composition and abundance of herbivores in these wetlands.
Anales del Instituto de la Patagonia, 2018
Understanding how communities are structured under relatively pristine conditions is critical to understanding their ecology and evolution. In this study, we examined the structure of aquatic communities in the Torres del Paine National Park in Chilean Patagonia. Using dipnet surveys, we quantified the distribution of larval anurans and all macroinvertebrates from 81 habitats across a hydroperiod gradient (lakes, ponds, permanent wetlands, semi-permanent wetlands, and temporary wetlands). Compared to surveys conducted at similar northern latitudes that have high species richness and hydroperiod specialization, Patagonian habitats contained a dramatically lower richness with many taxa widely distributed across the hydroperiod gradient. Overall, taxonomic richness was lowest in temporary wetlands and lakes, but highest in habitats with intermediate hydroperiods. The cause of this unimodal relationship was a small decline in the prevalence of all taxa on the temporary end of the gradient (due to habitat desiccation) but a complete exclusion of several taxa on the most permanent end of the gradient (due to fish predation). These results are consistent with North American studies of aquatic communities and lend support to the hypothesized effect of disturbance on the distribution of biodiversity. The fact that most biodiversity occurs in the temporary and intermediate hydroperiods underscores the importance of managing the full range of aquatic communities rather than only concentrating on the larger and more apparent lakes.
Latin American Journal of Aquatic Research, 2015
Changes in land use which directly or indirectly affect freshwater fauna constitute one of the principal anthropic factors which have caused world biological diversity to disappear rapidly during recent decades. This fauna includes aquatic benthic macroinvertebrates, organisms presenting temporal and spatial variation due to a variety of factors, one of which is the diverse food resources available in the rivers. To assess the effect of anthropic activities on this fauna, the distribution, abundance and characterisation of the functional feeding groups of aquatic macroinvertebrates were analysed, together with the physical and chemical variables in the environments of four coastal river basins of southern south-central Chile. A total of 104 taxa of macroinvertebrates were recorded, the principal component of the community being the Diptera (26 taxa). The abundance and richness of taxa were greater in summer and lower in winter. The most abundant species belong to the order Ephemeroptera and Plecoptera. Macroinvertebrates were affected by different land use: stations with less anthropic activity and greater altitude had higher macroinvertebrates abundance, while the lowest abundance was found at the lowest stations. The functional feeding groups which were most abundant spatially and temporally were the collector-gatherers and the shredders. The physical and chemical water quality variables proved to be of exceptional quality in all the stations. These results suggest that policies governing changes in land use in central and southern Chile should take into account the dramatic alterations that these changes impose on the macroinvertebrates community. Policies for biodiversity conservation should therefore focus on these small but important organisms in the north Patagonian region of South America, which is a hotspot of world diversity.
Impact of fish introduction on planktonic food webs in lakes of the Patagonian Plateau
Biological Conservation
Patagonia fishless ponds have been stocked with fishes for recreational purposes since early in the 20th century. We carried out a summer plankton sampling in 18 Patagonian lakes; 12 fishless, 5 with introduced fishes and 1 with endemic fish fauna. The lakes are sit-uated on a latitudinal gradient from 39° to 49°S. Zooplankton and phytoplankton composi-tion, phytoplankton relative abundance, and zooplankton body size and mouthpart morphology were analyzed. Results showed differences between lakes with and without fishes; in the presence of fish zooplankton size spectrum tended to be narrower because of the disappearance of Daphnia and large centropagid copepods. Zooplankton composition changed: centropagid species richness decreased and rotifers dominated. Contrarily, in fishless lakes 3 or 4 centropagid species, differing markedly in body size and exploiting dif-ferent food niches, were observed co-occurring. These changes in zooplankton seemed to cascade down to phytoplankton. Fis...
Pelagic communities and ecosystem processes in Andean Patagonian lakes
Limiting nutrients, nitrogen and phosphorus, are of crucial importance in the structure and dynamics of freshwater plankton. Oligotrophic lakes are nutrient limited environments and therefore their plankton dynamics depends mostly on internal mechanisms of recycling. The plankton dynamics and food web structure of Andean lakes were analysed linking the biogeochemical cycles and classic food web ecology. As in other oligotrophic waters, the producer trophic level of Andean lakes is formed by a phytoplankton dominated by small cells. A particular feature of these lakes is that the herbivorous zooplankton is restricted to rotifers and small crustaceans with body length < 1 mm. The direct effect of grazing decreases nanoplanktonic cells abundance but, the indirect effect of zooplankton (through nutrient recycling) results in an increase in netphytoplankton, particularly diatoms. Changes ín the zooplankton constitution over the annual cycle may change the nutrient supply ratio. The copepod Boeckella gracilipes decreased P limitation lowering the N:P ratio whereas the dominance of the cladoceran Bosmina longirostris increased the N:P ratio and therefore increased P limitation during summer. In addition, predation by larvae of the authoctonous fish Galaxias maculatus change the quality and quantity of grazers since their predation on Boeckella nauplii provokes the failure of the summer cohort of the copepod. Consequently, zooplankton composition and the elemental ratios of recycled nutrients change. These results suggest that top-down and bottom-up effects of pelagic food webs cannot be easily separated.
River Research and Applications, 2004
Composition and structure of macroinvertebrate communities were documented in relation to hydrochemical variables over a 10-month period in four headwater tributaries of the Futaleufú River, northwestern Chubut, Argentina. The streams are located along the strong rainfall gradient that decreases from west to east and they have different basin features. At Blanco and Baggilt streams, riparian vegetation consisted primarily of native Nothofagus forest, while in the Nant y Fall and Rifleros, basins with a long legacy of domestic grazing, the introduced Salix fragilis was the dominant riparian species. Macroinvertebrate species richness, density, and biomass were similar among rivers; however, biomass of shredders was highest in the Nothofagus forested streams and collector-filterers were significantly higher in Salix fragilis-bordered rivers. Water temperatures were higher in nonnative Salix sites than in the native or mixed forested sites. Canonical community analysis indicated community composition was related to geomorphic attributes of the rivers, especially slope, basin height (elevation change), distance to the source, substratum size, and Salix coverage. Moreover, seasonally dynamic variables, rainfall and water temperature were good community predictors. Land-use change (conversion from Nothofagus to pastures and the Salix fragilis invasion in the riverbanks of pasture-dominated catchments) was interactive with natural stream attributes as determinants of macroinvertebrate distribution and abundance.
Evidence of the Anthropic Impact on a Crustacean Zooplankton Community in Two North Patagonian Lakes
Sustainability
Lately, agriculture, livestock, forestry, and aquaculture activities have been greatly developed in Chilean North Patagonia, negatively impacting the balance of the environmental conditions in lakes and affecting the development and survival of several native species. The aim of this study was to assess the anthropic impact on a zooplankton community in two North Patagonian lakes. We collected samples from four sites belonging to Lake Icalma and Lake Llanquihue, including four replicates per site. Water samples were analyzed for physicochemical characteristics and zooplankton communities. We focused on the presence of Daphnia pulex, a species of zooplanktonic crustacean that performs a key role in capturing energy from primary producers to deliver it to final consumers such as fish. We found that Llanquihue showed higher total phosphorus, nitrogen, copper, iron, manganese, total dissolved solids (TDS), and conductivity (EC) than Icalma. Furthermore, ecological variables were greatly...
Ecological Connections Across the Marine-Terrestrial Interface in Chilean Patagonia
2022
Chilean Patagonia encompasses the two southernmost terrestrial ecoregions of the temperate forest biome of South America (North-Patagonian and Sub-Antarctic Magellanic) and the two western marine ecoregions of the Magallanes Province (Chiloense, and Channels and Fjords of Southern Chile). These ecoregions are immersed in a complex mosaic of terrestrial (with marked altitudinal gradients), freshwater (including wetlands, rivers, lakes, and lagoons) and marine ecosystems (with myriad islands, channels, and fjords). With more than
Crustaceana, 2017
The Chilean north Patagonian inland waters are characterized by their low mineral concentrations. In their original status, many of these ecosystems have native vegetation in their surrounding drainage basins, but in the last decades the native vegetation was replaced by agricultural, urban, and industrial zones, with as a result of these human alterations that those aquatic communities changed. The aim of the present study was to make a literature review about the ecological role of crustaceans in Chilean north Patagonian lakes and rivers. The literature mentioned the presence of amphipods (Hyalella), crayfishes (Samastacus spinifrons), and freshwater crabs (genusAegla), and many of these species hold a conservation risk due to the consequences of habitat damage and/or their high endemism. These crustaceans are important for the degradation of particulate organic matter originating from the surrounding vegetation, and are prey for native and introduced salmonid fishes. Similar patt...