Cyanobacterial dynamics in shallow Lake Apopka (Florida, U.S.A.) before and after the shift from a macrophyte‐dominated to a phytoplankton‐dominated state

Abstract

Summary Paleolimnological data were used to reconstruct the primary producer history of shallow, hyper‐eutrophic Lake Apopka, Florida, U.S.A. Lake Apopka changed from a macrophyte‐dominated state to a phytoplankton‐dominated state in 1947. It has remained phytoplankton‐dominated despite efforts to re‐establish clear‐water conditions and submersed aquatic plants. Photosynthetic pigments, organic matter and nutrients (C, N, P) were analysed in a 4.28‐m sediment core that spans the past c. 8000 years. Our objectives were to: (i) reconstruct the primary producer history of Lake Apopka throughout its c. 8000‐year existence, (ii) determine whether the cyanobacterial dominance established in 1947 in Lake Apopka is the only period of cyanobacterial dominance in the lake's history and (iii) relate changes in the cyanobacterial community to known human impacts and recent management efforts. Lake Apopka possessed a macrophyte‐dominated primary producer community throughout most of its Holocene history, with diatoms, green algae and some cyanobacteria characterising the non‐macrophyte, primary producer component of the community. Since 1947, however, higher plants have been virtually absent in the lake and cyanobacteria have dominated the primary producer community, marking the first time that cyanobacteria have played such an important role in the lake. The cyanobacterial community itself has undergone multiple changes since 1947, confounding management efforts that have focused on a single driver of the primary producer community, that is phosphorus.

Reducing the Phytoplankton Biomass to Promote the Growth of Submerged Macrophytes by Introducing Artificial Aquatic Plants in Shallow Eutrophic Waters

“…The principal characteristics of aquatic macrophytes are their ability to accumulate nutrients and sustain biogeochemical cycles in aquatic environments [1,2]. However, shallow lake eutrophication with the concomitant occurrence of cyanobacterial blooms has led to the decline of submerged macrophytes and the degeneration of water functions [3,4], which have transformed from a macrophyte-dominated state (clear water state) to a phytoplankton-dominated state (turbid water state) [5,6]. Environmental stressors, such as nutrient enrichment [7], high temperatures [8], and water level changes [9], favor cyanobacterial communities.…”

A Review on the Study of Cyanotoxins in Paleolimnological Research: Current Knowledge and Future Needs

“…While paleolimnological techniques (photosynthetic pigments, akinetes) have been used to infer past cyanobacteria presence in lake systems [20,[53][54][55][56], few studies have attempted to infer historic MC production. Cyanotoxin measurements in sediments are not common, but investigations have confirmed conditions that favor toxin preservation, as well as the potential use of fossilized toxins as a paleolimnological tool.…”

Pigments in surface sediments of South American shallow lakes as an integrative proxy for primary producers and their drivers

“…Although aquatic macrophytes as well as plant material from the surrounding catchment may contribute to the sediment pigments, their share is generally low (Leavitt & Hodgson, 2001). Revelation of longer-term trends (decades to centuries or millennia) in controls of algal abundance and composition in shallow lakes has been sought through palaeolimnological studies (Buchaca et al, 2011;McGowan et al, 2005;Waters, Schelske, & Brenner, 2015). Revelation of longer-term trends (decades to centuries or millennia) in controls of algal abundance and composition in shallow lakes has been sought through palaeolimnological studies (Buchaca et al, 2011;McGowan et al, 2005;Waters, Schelske, & Brenner, 2015).…”

“…Therefore, when collected from the deepest part of the lake, pigments from lake surface sediments integrate habitats (pelagic and benthic) (Buchaca & Catalan, 2008;Steinman, Havens, Louda, Winfree, & Baker, 1998) and temporal variation (seasons to years) (Buchaca & Catalan, 2007;Leavitt, Carpenter, & Kitchell, 1989;Leavitt & Findlay, 1994) and represent different groups of in-lake microbial primary producers. Revelation of longer-term trends (decades to centuries or millennia) in controls of algal abundance and composition in shallow lakes has been sought through palaeolimnological studies (Buchaca et al, 2011;McGowan et al, 2005;Waters, Schelske, & Brenner, 2015). Amongst the different pigments present in the sediment, Chl-a and β-carotene are used as proxies for total algal biomass, including cyanobacteria, while carotenoids are biomarkers of different taxa, including phototrophic bacteria (Liaaen-Jensen, 1964;Rowan, 1989).…”