Nutrients limiting the growth of planktonic and benthic-littoral primary producers in Patagonian Andean Lakes

Abstract

In this work, we assess differences in nutrient limitation (nitrogen and phosphorus) between benthic-littoral (in the littoral habitat) and planktonic (in the epi-pelagic habitat) primary producers of seven Patagonian Andean lakes in southern South America. We conducted nutrient enrichment experiments using nitrate, ammonium, and phosphate to identify which nutrient(s) restrict primary producers’ growth in each lake habitat. Also, we determined the concentration of dissolved inorganic nitrogen (DIN), soluble reactive phosphorous (SRP), and the nitrogen to phosphorous ratio (DIN:SRP) at the littoral and epi-pelagic habitats of each lake. For all the lakes, benthic-littoral primary producers were limited by nitrogen, while planktonic primary producers in the epi-pelagic habitat were colimited by nitrogen and phosphorus. Our study is the first to show that different nutrients limit the growth of benthic-littoral and planktonic primary producers in Patagonian Andean lakes. This contributes to our understanding of lake ecology in a region where there is limited information on benthic-littoral habitats. This is important because globally, there is an increase in periphyton blooms in the benthic-littoral habitats of oligotrophic lakes, while the pelagic habitats remain unchanged. Additionally, we found nutrient concentrations in the lakes are up to 7.4 times higher than those described in previous studies, which may be related to anthropogenic impact and natural events. If nutrient levels continue to increase, algal blooms in Patagonian Andean lakes may become a regional issue, especially in the benthic-littoral habitats.