Seasonal phytoplankton response to increased temperature and phosphorus inputs in a freshwater coastal lagoon, Southern Brazil: a microcosm bioassay

Abstract

Aim: the present study aimed at assessing the response of phytoplankton biomass (as chlorophyll-a) to simulated conditions of increased water temperature and phosphorus (P) inputs in Peri lagoon, a subtropical coastal lagoon dominated by Cylindrospermopsis raciborskii most of the year; Methods: microcosm experiments were conducted in thermostatic light chambers during 3 and 7 days in austral summer, autumn and winter 2009. Control temperatures were tested against 3 and 5 °C rises in water temperature in each season. In each temperature treatment, three P concentrations were tested: control (non-enriched, ~1.5 µg.L -1 PO 4 3+ ) and enrichments of four (+6 µg.L -1 PO 4 3+ ) and eight (+12 µg.L -1 PO 4 3+ ) times natural concentrations; Results: the results showed that P enrichments alone did not increase chlorophyll-a concentrations, but temperature increases significantly elevated phytoplankton biomass in autumn and winter microcosms. Water temperature increases were followed by significant elevations in the oxygen saturation levels in all microcosms and seasons. The combined effect of increased temperature and P enrichments resulted in the highest chlorophyll-a levels also in autumn and winter. Summer microcosms seem to have been negatively affected by the experimental conditions (too high water temperatures); Conclusions: the bioassays showed that global temperature rises can significantly elevate the phytoplankton biomass in Peri coastal lagoon, especially in colder months and if followed by increased P inputs, what can lead to major ecological consequences to the water body and to water supply issues in the region.

Dissolved organic matter signatures vary between naturally acidic, circumneutral and groundwater-fed freshwaters in Australia

“…Seasonal variation in a number of DOM quality indices have been reported previously from a number of different studies (Jaffe et al 2008, Awad et al 2017, Holland et al 2017. Phytoplankton and periphyton growth is known to increase at warmer temperatures (Hennemann andPetrucio 2010, Schabhüttl et al 2013). The significant difference in aromaticity and abundance of humic-like and fulvic-like components, respectively, suggests that higher amounts of autochthonous DOM produced during the summer/autumn season may have led to differences in CDOM shown in this study.…”

Paleolimnological record as an indication of incipient eutrophication in an oligotrophic subtropical coastal lake in Southern Brazil

“…Alterations in rainfall patterns and temperatures could have increased nutrient input to Peri Lake and stimulated primary production. Hennemann and Petrucio (2010) showed in microcosm experiments in the same lake that higher temperatures can indeed significantly increase chlorophyll-a concentration, especially in colder seasons and if followed by higher P inputs. The study conducted by Trolle et al (2010) showed that vertical concentration profiles of C, N and P in lake sediments can be higher in the upper, most recently deposited sediment strata, driven largely by natural diagenetic processes and not necessarily by eutrophication, since organic species of C, N and P will undergo a natural decay with time, thereby generating naturally lower concentrations in the deeper and older sediments.…”

Spatial variation of nutrients and primary productivity in the Rufiji Delta mangroves, Tanzania

“…Phytoplankton growth was low during September 2013. Hypothetically, this might have been due to cyanobacterial growth, which would hinder primary productivity (Hennemann and Petrucio 2010), but this needs to be confirmed based on monitoring data.…”