Observations of the tropical atmosphere are fundamental to the understanding of global changes in air quality, atmospheric oxidation capacity and climate, yet the tropics are under-populated with long-term measurements. The first three years (October 2006 -September 2009) of meteorological, trace gas and particulate data from the global WMO/Global Atmospheric Watch (GAW) Cape Verde Atmospheric Observatory Humberto Duarte Fonseca (CVAO; 16° 51' N, 24° 52' W) are presented, along with a characterisation of the origin and pathways of air masses arriving at the station using the NAME dispersion model and simulations of dust deposition using the COSMO-MUSCAT dust model. The observations show a strong influence from Saharan dust in winter with a maximum in super-micron aerosol and particulate iron and aluminium. The dust model results match the magnitude and daily variations of dust events, but in the region of the CVAO underestimate the measured aerosol optical thickness (AOT) because of contributions from other aerosol. The NAME model also captured the dust events, giving confidence in its ability to correctly identify air mass origins and pathways in this region. Dissolution experiments on collected dust samples showed a strong correlation between soluble Fe and Al and measured solubilities were lower at high atmospheric dust concentrations.Fine mode aerosol at the CVAO contains a significant fraction of non-sea salt components including dicarboxylic acids, methanesulfonic acid and aliphatic amines, all believed to be of oceanic origin. A marine influence is also apparent in the year-round presence of iodine and bromine monoxide (IO and BrO), with IO suggested to be confined mainly to the surface few hundred metres but BrO well mixed in the boundary layer. Enhanced CO 2 and CH 4 and depleted oxygen concentrations are markers for air-sea exchange over the nearby northwest African coastal upwelling area. Long-range transport results in generally higher levels of O 3 and anthropogenic non-methane hydrocarbons (NMHC) in air originating from North America. Ozone/CO ratios were highest (up to 0.42) in European air masses that contain relatively less well-aged air. In air heavily influenced by Saharan dust the O 3 /CO ratio was as low as 0.13, possibly indicating O 3 uptake to dust. Nitrogen oxides (NO x and NO y ) show generally higher concentrations in winter when air mass origins are predominantly from Africa. High photochemical activity at the site is shown by maximum spring/summer concentrations of OH and HO 2 of 9 × 10 6 molecule cm -3 and 6 × 10 8 molecule cm -3 , respectively. After the primary photolysis source, the chemistry of IO and BrO, the abundance of HCHO, and aerosol uptake are important for the HO x budget in this region.3
The interaction between native fishes and salmonids introduced in Patagonia at the beginning of the 20th Century, developed at the same time as the environmental change. The phenomenon of global warming has led to the formulation of predictions in relation to changes in the distribution of species, in the latitudinal dimension, both at intralacustrine, or small streams levels. The aim of the present work includes three main objectives: a) to compose a general and updated picture of the latitudinal distribution range of native and alien fishes, b) to analyze the historical changes in the relative abundance of Percichthys trucha, Odontesthes sp., and salmonids in lakes and reservoirs, and c) to relate the diversity and relative abundance of native and salmonid fishes to the environmental variables of lakes and reservoirs. We analysed previous records and an ensemble of data about new locations along the northern border of the Patagonian Province. We compared current data about the relative abundance of native fishes and salmonids in lakes and reservoirs, with previous databases (1984)(1985)(1986)(1987). All samplings considered were performed during spring-summer surveys and include relative abundance, as proportions of salmonids, P. trucha, and Odontesthes sp. For the first time, we found changes in fish assemblages from twenty years back up to the present: a significant decline in the relative abundances of salmonids and an increase of P. trucha. We studied the association between the diversity and relative abundance of native and salmonid fishes and the environmental variables of lakes and reservoirs using Canonical Correspondence Analysis. Relative abundance showed mainly geographical cues and the diversity relied largely on morphometric characteristics. Relative abundance and diversity seem to have a common point in the lake area, included into the PAR concept. Native abundance and alien diversity were negatively related with latitude. Greater native diversity was observed in lakes with high PAR compared with salmonids.Historical changes such as southward dispersion, relative abundance changes, and geographical patterns for relative abundance and diversity are basic concepts needed not only in future research but also in management design for Patagonian fish populations.
Aim To provide an objective geographic framework displaying the distribution patterns of freshwater fishes from Argentina. Location Argentina, southern South America. Methods Parsimony analysis of endemicity (PAE) and similarity and cluster analyses were applied to presence and absence data on 440 fish species from 52 localities in Argentina. Both 50% majority consensus and strict consensus analyses were undertaken in the first case, and the Jaccard similarity index was used in the second. Results Five ichthyogeographic provinces are described based on a PAE of the 52 localities. A cluster analysis provided similar results. Main conclusions The following zoogeographic provinces are proposed for Argentine freshwater fish fauna following the International Code of Area Nomenclature: Andean Cuyan, Patagonian, Aymaran, Great Rivers and Pampean. The former two are placed within the Andean Subregion of the Austral Region, and the latter three within the Neotropical Subregion of the Holotropical Region. These provinces, based on results coinciding with PAE and cluster analysis, represent the first classification of Argentine provinces based on objective methods. Some small regions of endemism and some localities remain separated from the proposed regions. The new scheme includes valuable empirical information from previous schemes, and is in agreement with ecological zones and other environmental arrangements proposed earlier.
The latitudinal extension of southern South America imposes a thermal gradient that affects the structure of marine and freshwater fish assemblages and the biology of the species through direct exposure to the temperature gradients or by means of a web of historical and ecological relationships. We have reviewed biological and ecological data of marine and freshwater fishes from the southern Neotropics, including Patagonia, and report several examples of dependence on temperature, from glacial times to today's climate change. We were able to identify historic and present effects on the diversity of fish assemblages, isolation, southern limits for the distribution of species, and morphological variation among populations. There is a wide range of characteristics that exemplify an adaptation to low temperatures, including biochemical peculiarities, physiological adjustments, and alternative life history patterns, and these appear in both freshwater and marine, and native and exotic fishes. The consequences of stable temperature regimes in both the ocean and thermal streams deserve special mention as these shape specialists under conditions of low selective pressure. At present, habitat use and interactions among species are being subject to changes as consequences of water temperature, and some of these are already evident in the northern and southern hemispheres.
ABSTRACT1. The Lower La Plata River basin contains between 160 and 260 native species depending on the river segment, with a few stretches containing locally endemic species.2. Extinction risk analysis for 185 freshwater fish in the lower La Plata River basin is presented for the first time on the basis of regionally standardized International Union for Conservation of Nature (IUCN) Red List criteria and is compared with alternative methods within the region.3. There were 11 threatened species (6%), of which three were considered as Endangered and eight as Vulnerable. A further three were rated as Near Threatened; while 121 (66%) were assessed as being of Least Concern, and 49 (26%) remained Data Deficient. The application of regional guidelines after using the global criteria did not change the categories established.4. The application of the IUCN criteria A and B presented considerable challenges because of insufficient information, with criterion C being inapplicable; whereas criterion D proved valid in five instances where endemic species were found highly restricted in geographical range and only inhabiting small streams.5. The use of other approaches, such as the Sum of Index (SUMIN) method and the Assessment Method of Threat Degree (MEGA), resulted in only an 11% agreement with the IUCN results for the main commercial and recreational target species.6. The discrepancies between the IUCN and the other methods may be explained in that the former measures the extinction risk by population decline as the main criterion, whereas the latter two put more emphasis on the assessment of intrinsic vulnerability and the threat status, with these additional criteria being incorporated in order to define conservation priorities.7. Further research is strongly recommended for the application and improvement of the IUCN regional criteria based on better ecological information, particularly data on non-target species inhabiting small tributaries, wetlands, and headwaters across the basin.
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