Phillip Wunder Water Hyacinth May 9 2005 Water Hyacinth Assessing Recovery from Salinity Induced Stress Phillip Wunder Abstract Water hyacinth Eichhornia crassipes recognized as one of the world s most noxious aquatic invasive species is currently invading the San Francisco Bay Delta Although water hyacinth can tolerate a wide range of environmental conditions salinity is known to limit its spread in estuaries and tidally influenced streams suggesting that a better understanding of water hyacinth s tolerance to salinity may facilitate its control While extensive information exists on the salinity levels needed for water hyacinth mortality 6 0 8 0 virtually no information exists on water hyacinth recovery when the plant experiences temporary exposure to lethal levels of salinity This study determined the recovery ability of water hyacinth as a function of three factors exposure duration salinity level and recovery time Water hyacinth were exposed to salinity levels of 5 0 6 0 and 7 0 for 7 14 21 and 28 day periods After exposure the water hyacinth were allowed 7 and 14 days to recover in non saline environments Wet plant weight and leaf chlorophyll were used as indictors of water hyacinth health The multiple linear regression of weight on salinity exposure duration recovery and interactions explained 77 of the variability in weight and was highly significant p 0 0001 Recovery did not significantly affect leaf chlorophyll Recovery rates were greatest for water hyacinth experiencing the shortest exposure times at the lowest salinity levels This study determined that the base level needed for water hyacinth mortality where no recovery would occur is an exposure of 21 days at 7 ppt salinity p 1 Phillip Wunder Water Hyacinth May 9 2005 Introduction Recognized as one of the world s most noxious aquatic weeds Eichhornia crassipes Mart Solms is native to the Amazon River Basin and now occupies numerous new tropical and sub tropical habitats throughout the world Penfound and Earle 1948 Barret 1980 Known more commonly as water hyacinth this species is recognized by the California Invasive Plant Council Cal IPC as a most invasive wildland pest plant Water hyacinth has an incredible rate of growth populations can double their numbers in two weeks through vegetative reproduction alone Penfound and Earle 1948 Barret 1980 Harley 1990 Through water hyacinth s engulfing presence large amounts of sunlight are blocked thorough oxygen exchange is prevented and dissolved oxygen levels drop the food web is altered habitat for water fowl and other organisms is either destroyed or changed and the biological diversity of the invaded area is greatly reduced Denny et al 2001 Brendonck et al 2003 Water hyacinth can be a problem economically as it negatively affects fisheries slows or even prevents water traffic impedes irrigation reduces the water supply obstructs water ways and slows hydropower generation Denny et al 2001 Brendonck et al 2003 Despite water hyacinth s ability to survive in wide ranges of sunlight pH and water supply Tag El Seed 1975 elevated levels of salinity inhibit its health and vitality Salinity levels become lethal for water hyacinth between 6 0 and 8 0 with no individuals able to persist concentrations greater than 8 0 Muramoto and Oki 1988 While there is adequate information on the fatal levels of salinity for the water hyacinth when the exposure duration is indefinite Earle and Penfound 1948 Haller et al 1974 Muramoto and Oki 1988 Casabianca and Laugier 1995 very few studies have provided information on the plants recovery abilities from salinity stress after temporary exposures to these salinity levels Although Casabianca and Laugier 1995 looked at water hyacinth recovery from saline stress in a petroliferous wastewater medium information on recovery in naturally saline environments is still lacking The current project investigates water hyacinth s performance given 7 and 14 days to recover in a non saline solution after 7 14 21 and 28 days of continuous exposure to salinity solutions of 5 0 6 0 and 7 0 An understanding of the combination of factors exposure duration concentration and recovery time that lead to water hyacinth death will be of value in the development of plausible control methods in environments where salinity levels can be manipulated In the San Francisco p 2 Phillip Wunder Water Hyacinth May 9 2005 Bay Delta salinity varies between 0 1 and 33 due to tidal seasonal and anthropogenic influences These techniques may be used separately or in combination with other control methods that are currently in use such as chemical spraying biological control using a weevil or mechanical removal Further study will need to be done in order to assess the effects of higher salinity concentrations on an environment and determine which combination of control methods will maximize hyacinth control while minimizing ecosystem damage Methods To increase population level variability within the test specimens the water hyacinth plants that were used in this experiment were collected from two separate populations the Dow Wetlands in Antioch CA and the Stone Lakes National Wildlife Refuge in Elk Grove CA Fig 1 Only pre flowering daughter rhizomes i e young individuals arising from vegetative reproduction were collected to ensure that all specimens were in roughly the same developmental stage Plants for the 5 0 and 6 0 exposures were collected on September 15 2004 and plants for 7 0 exposure were collected on October 29 2004 The plants were collected in buckets and immediately transferred one hour drive from Antioch and a two hour drive from Stone Lakes to a greenhouse at the University of California Berkeley s Oxford tract where the experiment was conducted Figure 1 The location of the two water hyacinth collection sites p 3 Phillip Wunder Water Hyacinth May 9 2005 Once in the greenhouse all water hyacinth were placed in nutrient solution for an initial seven day stabilization period to ensure that all plants started the experiment in similar health conditions Three plants from each location n 6 were placed in 38 L holding containers Treatments were then tested with combinations of three factors salinity level exposure duration and recovery All possible combinations of salinity exposure duration and recovery were tested The plants were exposed to four salinity levels 0 0 5 0 6 0 and 7 0 for four exposure durations 7 14 21 and 28 days and allowed to recover for two time periods 7 and 14
View Full Document
Unlocking...