UV Radiation as a Potential Driving Force for Zooplankton Community Structure in Patagonian Lakes

Abstract

This article explores the potential role of UV radiation (UVR) as an influence on zooplankton communities. In the first section we provide a general overview of UVR effects on freshwater zooplankton, with an emphasis on Argentine and Chilean environments. In the second section we present the results of a survey involving 53 temperate lakes across a gradient of UVR exposure to determine patterns of species richness and specific diversity. These community characteristics decreased at high potential UVR exposure (i.e. high mean water column irradiance or low lake optical density). A threshold value of mean water column irradiance of approximately 10% of the surface level seems to limit both richness and diversity to minimum values. On the basis of the collected evidence it is not possible to definitely conclude that UVR rather than another covarying factor is responsible for the decrease in specific diversity observed at the lowest end of lake optical depth. However, lakes with values above the previous threshold are likely to exhibit highly depauperate zooplankton communities regardless of the mechanism. As a cautionary note we suggest that changes in the optical characteristics (i.e. changes due to atmospheric conditions, precipitation patterns or vertical displacement of the tree line) may result in sudden shifts in zooplankton community structure.

Morphometric differences in two calanoid sibling species, Boeckella gracilipes and B. titicacae (Crustacea, Copepoda)

“…Similarly, these descriptions are consistent with the results of comparative studies of the frontal knobs in males of the brine shrimp Artemia (Crustacea, Branchiopoda) exposed to extreme environments, primarily to variation in salinity and temperature (De Bayly & BoxShall, 2008). This species is exposed to high levels of ultraviolet radiation in tropical and subtropical latitudes (CaBrera et al, 1997;helBling et al, 2002;SCheihing et al, 2010) and in Patagonian inland waters (Marinone et al, 2006). Salinity variations and ultraviolet radiation exposure are accelerators of molecular changes in aquatic crustaceans (heBert et al, 2002).…”

Plankton crustaceans in bays with different trophic status in Llanquihue lake (41° S Chile)

“…In unpolluted conditions the calanoids copepods would have an important role as grazer on phytoplankton and in turn would be eaten by zooplanktivorous fishes in Argentinean and Chilean Patagonian lakes (Soto and Zuñiga, 1991;De los Rios-Escalante, 2010;Reissig et al, 2015;Trochine et al, 2015). Additionally, the natural ultraviolet radiation exposure that increased in Patagonia affect zooplankton assemblages because the species have different tolerance to UV radiation under trophic gradient (Marinone et al, 2006;De los Ríos-Escalante, 2010;Hylander et al, 2012). Then considering both view point, the zooplankton composition can be regulated by trophic variations, ultraviolet radiation exposure and fish predation.…”

Vertical distribution of zooplankton in subalpine and alpine lakes: Ultraviolet radiation, fish predation, and the transparency‐gradient hypothesis

“…Southern Hemisphere calanoids in the genus Boeckella appear to be more variable in their UV tolerance than Diaptomids (Zagarese et al 1997;Wubben et al 2001), though most species of Diaptomids have yet to be tested for their UV tolerance levels. Perhaps some of the most compelling evidence for the importance of UV in controlling zooplankton community structure in alpine lakes is that only a single species of large red copepod persists in systems where the maximum lake depth is less than the 10% UV 320 nm attenuation depth of the lake (Marinone et al 2006).…”