Phytoplankton structure is more influenced by nutrient enrichment than by temperature increase: an experimental approach upon the global changes in a shallow subtropical lake

Abstract

Phytoplankton structure is more influenced by nutrient enrichment than by temperature increase: An experimental approach upon the global changes in a shallow subtropical lake Climate change is considered one of the greatest threats to aquatic ecosystems around the globe. Among the expected changes, including the dynamics of phytoplankton, the growth of cyanobacteria is often cited. This study evaluated the individual and combined effects of increased temperature and nutrients on phytoplankton community structure in a large, oligo-mesotrophic subtropical shallow lake (Mangueira Lake, southern Brazil). The study was conducted in microcosms to simulate possible scenarios of climate change, alone and in combination with nutrient enrichment (N and P); water samples were collected in winter and summer. Phytoplankton total biomass, species richness and diversity did not vary significantly with manipulation of temperature alone, either in winter or in summer. Only cyanobacteria biomass increased significantly with an increase in temperature, in the winter experiments. In summer, phytoplankton total biomass, species richness, Bacillariophyceae and Cyanobacteria increased significantly with enrichment of N and P. The interaction between temperature increase and nutrient addition did not significantly affect phytoplankton attributes. Temperature increase alone was not sufficient to cause structural changes in the phytoplankton community. Instead, nutrient addition (N and P) proved to be the most significant influence on most phytoplankton attributes, even though turnover of bloom-forming cyanobacteria was not observed. Further studies on the resilience of aquatic ecosystems to climate changes may contribute to the conservation and management of these environments.

Phytoplankton response to differences in light and the addition of phosphorus in Lake Cikaret

“…This observation also indicated that the addition of phosphorus will increase the abundance of phytoplankton compared to treatments without phosphorus (Figure 1). According to Wieliczko et al (2020), in their research on Lake Mangueira, nutrient enrichment indirectly contributes to an increase in species richness and the total amount of phytoplankton. Although the result of the statistical analysis was insignificant (Table 4), there were differences in the response of phytoplankton to the addition of phosphorus and varied light levels.…”

Projeções de vazão para avaliação de estimativa de carga de nutrientes afluentes à lagoa Mangueira, Rio Grande do Sul, em cenários de mudanças climáticas do Quinto Relatório de Avaliação das Mudanças Climáticas

“…Tentativas de prever os possíveis efeitos de mudanças climáticas globais em ambientes aquáticos envolveram experimentação (DAVIS et al, 2009;FEUCHTMAYR et al, 2009;WIELICZKO et al, 2020) e uso de modelagem (DOMIS;MOOIJ;HUISMAN, 2007;ELLIOTT;DEFEW, 2011;BRÊDA et al, 2020). Nesse contexto, esta pesquisa contribui para a análise das alterações das vazões e cargas de nutrientes afluentes a lagos, como consequência da alteração no padrão de precipitação na bacia provocada por mudanças climáticas.…”