Wind Influences phytoplankton biomass and composition in a shallow, productive lake

Abstract

Factors that regulate phytoplankton dynamics in shallow, productive lakes are poorly understood. Water-column phytoplankton chlorophyll (avg 105 pg liter-') determined on 39 occasions over a 22-month period in shallow (mean depth, 1.7 m) Lake Apopka, Florida, correlated best with average daily windspeed compared with other environmental variables. High phytoplankton biomass reflects windinduced resuspension of a meroplanktonic algal maximum (MAM) that exists on the aphotic lake bottom in a layer -5 cm thick; this assemblage is dominated by microplankton-sized diatoms (>60% of total biomass) that can occur in cellular resting stages. Experiments demonstrate that the MAM can grow and photosynthesize at rates similar to surface populations when exposed to moderate irradiances. Direct inoculation of this meroplanktonic assemblage into surface waters during periods of high wind can account for a doubling in surface phytoplankton and diatom biomass as well as an increase in algal community size. A conceptual model outlines the influence that resuspension of the MAM has on ecosystem structure and function-in the lake.It is often assumed that phytoplankton dynamics are regulated by biogeochemical cycles of suspended materials in lakes, despite the fact that the water column in many lakes may interact readily with underlying sediments (e.g. Dokulil et al. 1979) especially in shallow lakes that are susceptible to changes in light fields due to bottom mixing (Carper and Bachmann 1983). In these globally common systems, mixing events can produce large increases in phytoplankton production and shifts in community composition (Padisak et al. 1988). However, it is unclear whether changes in phytoplankton biomass are associated with pulses

Extreme13 C enrichments in a shallow hypereutrophic lake: Implications for carbon cycling

“…Thick deposits of unconsolidated flocculent sediments that average Ͼ60% organic matter are present on the lake bottom (Gale and Reddy 1994;Schelske et al 2000). Frequent resuspension of sediments due to wind mixing occurs in this polymictic lake (Carrick et al 1993).…”

Blooms of the picoplanktonic cyanobacterium Synechococcus in Florida Bay, a subtropical inner‐shelf lagoon

“…The surficial sediments in these areas lost a major structural component of sediment stabilization, thereby becoming more susceptible to resuspension and enhancing diffusive processes. Resuspension and diffusion are known to be potential sources of internal nutrient supply for phytoplankton production (Stumm and Leckie 1971;Bachmann and Jones 1974;Hansen et al 1997) as well as a mechanism for reintroduction of meroplankton into the water column (Carrick et al 1993). Certain unique aspects of the chemistry of the sediments in this region may further enhance the potential for internal nutrient loading.…”

Can Hydrodynamics Change Phosphorus Strategies of Diatoms?—Nutrient Levels and Diatom Blooms in Lotic and Lentic Ecosystems

“…Reynolds et al [59] demonstrated that artificial mixing in large enclosures could either prolong diatom dominance or induce new growth for diatoms. Such increases in phytoplankton biomass are related to new growth resulting from resuspended nutrients (such as TP and TN) in lentic waters, where typical mixing episodes in thermally stratified lake systems occur once or twice annually during destratification [2,5,64]. In some lakes, the inhibition of resuspension can decrease the nutrient release from sediments [64], and resuspension is associated with increases in the concentration of phytoplankton biomass and nutrients [27].…”