Climate change and stoichiometric implications for zooplankton

BALSEIRO, E. G.

Torino

Congreso; SIL-2016 Torino; 2016

SIL Societas International Limnologie

Globalchange is affecting aquatic systems in many ways, through temperature increase,changes in transparency, irradiation and nutrient loads, affecting ecosystemstoichiometry, and so organismic fitness. Due to temperature increase, glaciersaround the globe are melting rapidly, threatening the receiving environments ofthe world?s fresh water reservoirs with significant changes. The meltwater,carried by rivers, contains large amounts of suspended sediment particles, affectingdownstream lakes. These suspended particles modify lake transparency dependingif the suspended material tends to increase or decrease according to glacierrecession. Changes in underwater photosynthetically active radiation wouldaffect food quality for zooplankton by changes the light-nutrient ratio in thewater column. In addition, changes in water transparency also affects URVpenetration, and hence the oxidative stress generated by these lightwavelengths. Here we analysed how food quality, in terms of elemental ratios,interact with factors as UVR and oxidative stress. In a first step, throughlaboratory and field experiments, we analysed how food quality affects thecapacity of zooplankters (Daphnia andcalanoid copepods) to respond to UVR generated oxidative stress. Then we movedto field studies to evaluate these results in natural zooplankton populations. LakeMascardi, located in the North-Patagonian Andean lake district, is a deepultra-oligotrophic lake that receives the Upper Manso River, which begins atthe largest glacier of Tronador Mountain (3554 m a.s.l.). Glacier fluctuationson Mountain Tronador have been observed since 1976 and show a continuousrecession. We took advantage of a 10 km light gradient in Lake Mascardi, analysinginterannual variations in water transparency, UVR penetration and food qualityas interacting factors affecting zooplankton populations. Along thistransparency gradient we found significant differences in light:nutrient ratioand stoichiometric food quality of the seston, together with a switch fromdominance of P-rich Daphnia in lowcarbon:nutrient stations to the dominance of low-P copepods in highcarbon:nutrient stations. In addition, we analysed the oxidative stress due toUVR in Daphnia commutata and how thisfactor can modulate the coexistence with other potential competitors such asthe copepod Boeckella gracilipes. Insummary, here we showed how climate change would affect zooplankton via changesin food quality and UVR effect.