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Experimental studies on the recovery potential of submerged aquatic vegetation after flooding and desiccation in a large subtropical lake
Harwell, M.C.; Havens, K.E. (2003). Experimental studies on the recovery potential of submerged aquatic vegetation after flooding and desiccation in a large subtropical lake. Aquat. Bot. 77(2): 135-151. dx.doi.org/10.1016/s0304-3770(03)00101-3
In: Aquatic Botany. Elsevier Science: Tokyo; Oxford; New York; London; Amsterdam. ISSN 0304-3770, more
Peer reviewed article  

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Keywords
    Aquatic plants; Droughts; Emergence; Experimental research; Flooding; Freshwater lakes; Recovery; Subtropical zones; Chara Linnaeus, 1753 [WoRMS]; Vallisneria americana; USA, Florida, Okeechobee L. [Marine Regions]; Fresh water

Authors  Top 
  • Harwell, M.C.
  • Havens, K.E.

Abstract
    In Lake Okeechobee (Florida), above average water depths from 1994 to early 2000 created poor light conditions on the lake bottom, leading to a widespread loss of submerged aquatic vegetation. In 2000, a controlled laboratory study quantified seedling emergence of Vallisneria americana (80±20 m-2; mean±S.E.) and emergence of Chara spp. (504±21 m-2; mean±S.E.) from sediments collected at a variety of sites confirming that a viable seed bank had persisted through years of poor light conditions. Considerable variance existed among the five sites from which seed banks were collected. Other species of submerged vegetation were hardly encountered. Additionally, a field transplant study using young V. americana plants examined the survival potential of V. americana in regions that had not supported submerged vegetation in the recent past. Although all transplants lost biomass, they produced new shoots and stolons in both sediment types. Transplants fared better in peat sediments than in the sandy sediments characteristic of areas where submerged vegetation was lost in the recent past. In summer 2001, an extensive drought exposed thousands of hectares of near-shore lake bottom, killing much of the submerged vegetation community. The potential for recovery of submerged vegetation from a desiccated and re-inundated seed/oospore bank was examined with cores taken from areas that had previously supported submerged vegetation. Extensive emergence of Chara spp., including a faster rate of emergence and a greater magnitude of emergence observed in desiccated cores (mean from three sites: 2728 m-2; 1S.E.: ±192) relative to cores still inundated (mean from one site: 918 m-2; 1S.E.: ±165), suggests that the drought may have led to an increased germination response for Chara. In contrast, there was little germination of vascular species, except for a few seedlings of the native V. americana and a few plants of Hydrilla verticillata.

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