Light availability as a possible regulator of cyanobacteria species composition in a shallow subtropical lake

Abstract

1. Variations in the relative biovolumes of dominant cyanobacterial taxa were evaluated in the context of environmental conditions using canonical correlation analysis (CCorrA) and Redundancy Analysis (RDA). The objective was to test a conceptual model in which underwater irradiance determines dominance by bloom‐forming (high light adapted) or non‐blooming (low light adapted) taxa. 2. The data set consisted of 404 contiguous observations, collected over a 3‐year period at eight pelagic sites, in shallow Lake Okeechobee, Florida, U.S.A. Data included species biovolumes, total phosphorus (TP), total nitrogen (TN), dissolved oxygen (DO) and chlorophyll a concentrations, as well as two indices: underwater irradiance (Secchi depth) and the ratio of Secchi:total depth. 3. The first environmental canonical variable was strongly correlated with the two light‐related indices, and negatively correlated with TP. This reflects the predominant role of resuspended P‐rich lake sediments in controlling underwater irradiance in the shallow lake. The first species canonical variable displayed a strong negative correlation with Lyngbya limnetica and L. contorta, and positive correlations with Anabaena circinalis, Aphanizomenon flos aquae and Microcystis spp. The results support the conceptual model; the first pair of canonical variables explained 55% of the variation in the species–environmental data set. RDA results provided further support for the hypothesis that irradiance was the major force controlling community structure. 4. One unexpected result was a positive association between Oscillatoria spp. dominance and indicators of high irradiance. This conflicts with past research indicating that Oscillatoria is a low light adapted taxon, and the finding that it is the most abundant taxon in Lake Okeechobee. This may reflect the fact that the two Lyngbya taxa were more strongly associated with low light conditions than Oscillatoria. CCorrA results indicated that Oscillatoria densities are strongly controlled by water temperature. There is a need for more detailed studies of cyanobacteria ecophysiology in order to explain fully the seasonality of phytoplankton in this and other shallow subtropical lakes.

Tracking management-related water quality alterations by phytoplankton assemblages in a tropical reservoir

“…Cyanobacterial abundance decreased from 2007 to 2010 after the applied EEM contributed to decrease TP concentrations and to reduce underwater light intensity. As already observed by Havens et al (1998) in a shallow sub-tropical lake, phytoplankton biomass, especially that of high-light adapted, bloomforming taxa such as the S-strategist Microcystis spp. strongly decreased when water transparency decreased due to the shading effect of floating beds.…”

Patterns and controls of nitrogen stable isotopes of particulate organic matter in subtropical lakes

“…We found 15 N depletion in several eutrophic lakes known to have nitrogen-fixing cyanobacterial blooms (Chapman and Schelske, 1997;Havens et al, 1998;Gu et al, 2006). Previous studies have found low d 15 N POM and the presence of nitrogen-fixing cyanobacteria in eutrophic lakes (Gu and Alexander, 1993;Lehmann et al, 2004).…”

A spatial investigation of the environmental controls over cryoconite aggregation on Longyearbreen glacier, Svalbard

“…As mentioned, an inverse relationship between cumulative IR and chlorophyll a concentration could be seen, with factors such as shading, period of exposure and erosion likely affecting chlorophyll a concentration. In addition, these comparisons between IR and chlorophyll a concentration suggest that low-light adaptation of photoautotrophic microorganisms, shown as important in shallow, turbid lacustrine ecosystems (Scheffer et al, 1997;Havens et al, 1998), may be a further factor controlling photosynthesis and thus bioaggregation. Furthermore, given that carbohydrate concentrations were found to increase up-glacier, it could be that radiation stresses necessitate microbial carbohydrate production (Chen et al, 2009) to provide a matrix for UV-protective mycosporine-like amino acids (Quesada and Vincent, 1997), in addition to the potential for cryoprotection and nutrient scavenging roles.…”