Periphyton responses to nitrogen decline and warming in eutrophic shallow lake mesocosms

Combined effects of eutrophication and warming on polyunsaturated fatty acids in complex phytoplankton communities: A mesocosm experiment

“…Potamogeton crispus (Pacheco et al, 2021), and filamentous green algae, as well as grazers, such as snails and zooplankton, which were not controlled in the experiment. The proportion of macrophytes and filamentous green algae, which compete for nutrients with phytoplankton, varied between mesocosms, as after 15 years the mesocosms have developed differently as is also the case for natural lakes.…”

“…Mesocosms are constantly mixed with a paddle-shaped mixer without visibly disturbing the sediment. Mesocosms contain also periphyton and submerged macrophytes, mainly Elodea canadensis and Potamogeton crispus (Pacheco et al, 2021), as well as small planktivorous fish (Gasterosteus aculeatus). All mesocosms received nutrients from the groundwater input in which total P (TP) and total N (TN) concentrations have varied with time, in 2014 averaging 0.01 (range 0-2) μg TP/L, and 3.2 (range 2-3.8) mg TN/L, equivalent to 0.15 mg P/m 2 /d and 43 mg N/m 2 /d on average.…”

“…Nutrient manipulations included three treatments: 1) control, which received only groundwater, i.e., no additional nutrient additions, and represented low nutrient conditions, and two treatments with additional nutrient additions, representing high nutrient conditions: 2) P addition and 3) addition of both P and N. Nutrient input and variation in the N:P ratio control phytoplankton production and community structure (Abell et al, 2010). On June 14, 2018, the N additions were discontinued to decrease the N:P ratio potentially inducing N limitation (Pacheco et al, 2021). The N additions resumed on June 14, 2019.…”

Preface: advances in the ecology of shallow lakes

“…Warmer temperatures may reduce nitrogen availability to primary producers due to accelerated denitrification and may also affect phytoplankton and periphyton biomass and composition. Pacheco et al ( 2022 ) compared periphyton responses to N decline in 12 shallow lake mesocosms during one year at low N and high N under three temperature scenarios: ambient, A2 IPCC scenario, and A2 increased by 50%. They used two submerged macrophyte species and artificial imitations of these as substrates for periphyton growth.…”