Nutrient ratios and phytoplankton community structure in the large, shallow, eutrophic, subtropical Lakes Okeechobee (Florida, USA) and Taihu (China)

Abstract

Analysis of ten-and four-year datasets for the large, shallow, subtropical, and eutrophic Lakes Okeechobee (USA) and Taihu (China), respectively, suggest that resource-ratio explanations for cyanobacteria dominance may not apply to these two lakes. Datasets were examined to identify relationships between nutrient ratios [total nitrogen (TN):total phosphorus (TP) and ammonium (NH 4 ? ):oxidized N (NO x )] and phytoplankton community structure (as proportions of cyanobacteria and diatoms to total phytoplankton biomass). Datasets were pooled by sampling month, averaged lake-wide, and analyzed with linear regression. In Okeechobee, the cyanobacteria proportion increased and the diatom proportion decreased with increasing TN:TP. In Taihu, cyanobacteria decreased with increasing TN:TP, but the opposite trend observed for diatoms was marginally significant. Okeechobee cyanobacteria increased and diatoms decreased with increasing NH 4 ? :NO x , but no significant relationships between phytoplankton and NH 4 ? :NO x were observed in Taihu. Both lakes had significant relationships between phytoplankton community structure and total nutrients, but these relationships were the opposite of those expected. Relationships between phytoplankton community structure and water quality parameters from the previous month resulted in improved relationships, suggesting a predictive capability. Statistical analysis of the entire datasets (not pooled) supported these and additional relationships with other parameters, including temperature and water clarity.

Long-term seasonal nutrient limiting patterns at Meiliang Bay in a large, shallow and subtropical Lake Taihu, China

“…Upon death, the algae settle to the benthos and cause N loss through denitrification in the sediment bed, which, in return, amplifies N-limiting conditions . Although studies of other shallow lakes have found that N-fixing cyanobacteria may supplement N (Mccarthy et al, 2009), during periods of cyanobacterial blooms, past research showed that the proportion of N-fixing cyanobacteria and N fixation efficiency were low in Lake Taihu (Mccarthy et al, 2007;Paerl et al, 2011). Hence, N concentrations in Meiliang Bay may have had little supplementation in summer and fall (Fig.…”

“…It is found that secondary N limitation was a transition phase that remained nearly a decade. In Lake Okeechobee, N reduction can drive blooms of N-fixing cyanobacteria (Mccarthy et al, 2009); therefore, to restore water quality in the lake, a plan was proposed to reduce P concentrations to create the historical natural P-limited conditions in Lake Okeechobee (Mccarthy et al, 2009). In Meiliang Bay, however, the cyanobacterial community is dominated by Microcystis spp., which is not an N-fixing species (Chen et al, 2003a;Chen et al, 2003b;Mccarthy et al, 2009).…”

“…In Lake Okeechobee, N reduction can drive blooms of N-fixing cyanobacteria (Mccarthy et al, 2009); therefore, to restore water quality in the lake, a plan was proposed to reduce P concentrations to create the historical natural P-limited conditions in Lake Okeechobee (Mccarthy et al, 2009). In Meiliang Bay, however, the cyanobacterial community is dominated by Microcystis spp., which is not an N-fixing species (Chen et al, 2003a;Chen et al, 2003b;Mccarthy et al, 2009). Some studies in Meiliang Bay have observed that N-fixation does not seem to occur, even by the genera Anabeana and Aphanizomenon (Mccarthy et al, 2007), which suggests that N fixation efficiency is limited.…”

Changes in phytoplankton communities along nutrient gradients in Lake Taihu: evidence for nutrient reduction strategies

“…N limitation occurred in summer and P limitation in winter, which affected the phytoplankton markedly (McCarthy et al, 2007;Xu et al, 2010). It was presumed that dominant species in Lake Taihu would shift from non-N 2 -fi xing Microcystis to potentially N 2 -fi xing cyanobacteria genera ( Anabaena and Aphanizomenon ) for N-limitation (or co-limitation) over the growing season (McCarthy et al, 2009). Most studies only focused on the bloom-forming species of Microcystis and the bloom-prone northern part.…”

Dinâmica do fitoplâncton e assimilação de nitrato, amônio e ureia em reservatórios subtropicais com diferentes graus de trofia

“…Em reservatórios tropicais, diversos fatores como a RSFA disponível (HENRY et al, 2006;CUNHA & CALIJURI, 2011), o TDH (BEAVER et al 2013, temperatura (MCCARTHY et al, 2009), períodos de estratificação e de mistura da coluna de água (CALIJURI et al, 2002), parecem ser importantes para regular a comunidade fitoplanctônica. Especialmente em ambientes com maior estado trófico (HUSZAR et al, 2006 Não houve variação significativa entre as profundidades para a maioria das variáveis, apenas para RSFA e para a assimilação de ureia.…”