Environmental Variability and Cyanobacterial Blooms in a Subtropical Coastal Lagoon: Searching for a Sign of Climate Change Effects

Abstract

Cyanobacterial blooms in marine and freshwater environments may be favored by shifts in physical water column parameters due to warming under climate change. The Patos Lagoon (PL), a subtropical coastal environment in southern Brazil, is known for recurrent blooms of Microcystis aeruginosa complex (MAC). Here, we analyze the variability of these blooms and their relation to changes in wind direction and speed, rainfall and freshwater run-off from 2000 to 2017. Also, we discuss both longer time-series of air temperature and rainfall and a review of local studies with microcystins produced by these noxious species. Since the 1980s, MAC blooms were associated to negative anomalies in annual precipitation that occur during La Niña periods and, in the last years (2001–2014), accompanied by a trend in low river discharge. MAC blooms were conspicuous from December to March, i.e., austral summer, with massive patches seen in satellite images as for 2017. We suggest that low rainfall and run-off years under NE wind-driven hydrodynamics might accumulate MAC biomass in the west margin of the PL system. In contrast, a positive, long-term trend in precipitation (from 1950 to 2016; slope = 3.9868 mm/yr, p < 0.05) should imply in high river discharge and, consequently, advection of this biomass to the adjacent coastal region. Due to the proximity to urban areas, the blooms can represent recreational and economic hazards to the region.

A Multi Proxy Assessment of Long-Term Anthropogenic Impacts in Patos Lagoon, Southern Brazil

“…In this sense, Microcystis aeruginosa blooms were recorded in Patos Lagoon since the 1980s (Yunes et al, 1998;de Souza et al, 2018), but previous observations of locals date back to the beginning of the 20 th century. Anyway, the system displays still fairly undisturbed conditions, thus highlighting the highly dynamic dilution potential of the lagoon.…”

Microcystins and Daily Sunlight: Predictors of Chronic Liver Disease and Cirrhosis Mortality

“…The results highlighted a potential correlation between total microcystins, mean daily sunlight, and age-adjusted chronic liver disease and cirrhosis death rates. Warming climate is expected to promote cyanobloom formation worldwide [42]. Since warm temperatures increase microcystin production in waterbodies [40] and earlier work has identified cyanotoxins in areas of increased liver cancer/disease prevalence [31,32], then a possibility exists that both factors co-exist to impact health.…”

Meteorological and potential climatic influence on high cyanobacterial biomass within Patos Lagoon (southern Brazil): A case study of the summer of 2019–2020

“…However, the major extension of PL is an oligohaline and freshwater system that is still understudied regarding cyanobacteria dynamics. The cyanobacterial dynamics in this limnic system might influence the phytoplankton dynamics farther downstream, to the lower part of PL and its adjacent coastal area (Souza et al, 2018), as seen in other estuaries (e.g., San Francisco Bay estuary, Lehman et al, 2005). The link between the limnic and estuarine parts of PL is mainly due to advection processes caused by continental freshwater contributions and wind forcing (Moller et al, 2001;Möller et al, 2009) on time scales varying from synoptic to interannual (Bitencourt et al, 2020;Távora et al, 2020) since the region is under microtidal influence.…”

“…Some important environmental alterations are related to regime shifts in rainfall and dry cycles worldwide (Paerl et al, 2015 and references therein;Thompson et al, 2015;Masson-Delmotte and Zhou, 2021) and have been reported to alter PL continental discharge contributions and wind regimes (Bitencourt et al, 2020;Távora et al, 2020). For instance, the alternation between flood and drought events can impact the structure and dynamics of cyanobacterial populations, since floods might produce high export rates of nutrients and organic material to adjacent coasts (Souza et al, 2018). On the other hand, dry periods can result Meteorological and climatic influence on cyanobacteria Canever et al in high phytoplankton biomass (Michalak et al, 2013;Ho and Michalak, 2017) and an increase in residence time (Fernandes et al, 2002;Aguilera et al, 2020), which can promote the development and extension of cyanoHABs in lagoons, such as in the main PL waterbody.…”