Introduction
An integrated aquatic plant management plan should consist of six basic components
(Table 1): prevention, assessment, site-specific management, evaluation, monitoring
and education. An aquatic plant management plan should integrate multiple techniques
to manage plant problems, both spatially and temporally, while also including with
some operational treatments some level of prevention, problem assessment, prevention,
evaluation, monitoring and education. Planning before beginning operational treatments
will spell the difference between success and failure (Nichols et al. 1988). Several
guides are available for developing lake management plans (Moore 1989; Nichols et
al. 1988; NYSDEC and FOLA 1990) and for developing integrated aquatic plant management
plans (Gibbons et al. 1994).
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Table 1
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Prevention
The best time to develop an integrated aquatic plant management plan is before a
problem occurs. However, few management groups have this level of foresight. Nevertheless,
prevention mechanisms can be invoked later, once management actions have reduced
problem levels of plant occurrence. In addition, prevention activities may reduce
or eliminate the introduction of other undesirable and nonnative species.
Assessment of the Aquatic Plant Problem
When developing a management plan for public or "common" areas, include all significant
user groups such as lakeshore owners, and lake user groups such as fisherman (even
different fishing groups), boaters, and local businesses dependent on the lake.
In a group context, the problem should be identified and defined. The group as a
whole should agree with the problem definition(s). The problem should be more detailed
than "plants get in the way," because problem identification is the first important
step to finding acceptable management solutions.
The problem should then be studied and as much information gathered as possible
to understand the problem. As part of the assessment component, local municipalities,
interested parties and resource agencies should cooperatively undertake a comprehensive
project to manage the water body in question, beginning with the development of
a Master Plan. The Master Plan would serve as a guide in the preservation, conservation,
restoration, maintenance, management, and development of the natural and man-made
resources of the lake. Guided by a Master Plan, a lake management plan should then
be developed, including an integrated aquatic plant management plan.
Management goals should be set in concentric layers, e.g., prevent introduction
of new species to the lake, set allowable levels of plants at swimming areas and
boat launches, establish monitoring at low-intensity use areas. As part of the problem
identification and study process, relevant resource management agencies, regulatory
agencies, and various layers of government agencies having overlapping jurisdictions
must be included. Early on, discover who does what, and what they will allow. Some
regulatory agencies have a core of unbending rules, but another layer of rules or
guidelines that can be negotiated. Once the regulatory agency develops some confidence
in the management group, it may become more willing to allow a given level of activity.
For instance, a core of unbending rules would be the label restrictions on herbicides
placed by both the EPA and state pesticide regulatory agencies. However, both levels
of government have some discretion in granting either special use or special needs
permits. Every locality has different requirements; some states require permits
for herbicide applications or even any aquatic management activity, while others
do not. Many groups wear themselves out fighting these layers of bureaucracy rather
than figuring out how to work with them; in the long run, the latter usually is
quicker and more efficient.
As part of the assessment process, information on your system needs to be gathered.
This may require hiring persons with special expertise. At a minimum, a species
list for the lake should be made and the areas with the problem plant identified.
Areal extent can be estimated on maps or through remote sensing (Table 2) . Even
if maps are made, some locations should be surveyed using semiquantitative techniques
(Madsen and Bloomfield 1992, 1993).
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Table 2
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An important component of making a species list is to identify correctly the species
collected and to maintain an herbarium (pressed plant) record of what was collected
(Hellquist 1993). Although many projects may never require legal verification of
what was collected, such a collection will, in the long run, reduce confusion and
aid in proper management. Identification of some species is difficult enough so
that expert verification may be required. Sometimes, even these experts will resort
to additional molecular techniques to separate species or races of plants that may
have management implications. For instance, flavonoid pigment analysis (Ceska and
Ceska 1986; Newroth 1993) has been used to separate the often similar species of
Myriophyllum in British Columbia. Likewise, isozyme analysis (Langeland 1989; Ryan
1989; Ryan et al. 1991) and random amplified polymorphic DNA (RAPD) analysis (Ryan
and Holmberg 1994) have been used not only to differentiate between monoecious and
dioecious hydrilla but to track different genetic "families" of these plants around
the country.
Assessment methods can also be used to evaluate potential levels of plants that
might be acceptable within the ecosystem. These may be based on environmental characteristics
(Wong and Clark 1979), based on acceptable risk to life and property (Madsen et
al. 1988; Madsen 1993), or based on user-group preference (Wilde et al. 1992; Henderson
1994). This provides a quantitative target for aquatic plant management.
Finally, management goals need to be set within a project management framework.
Available resources (funds, equipment, expertise and personnel) need to be identified
and a reasonable timeline to accomplish the management goals needs to be developed.
Developing both realistic resources and timelines will aid in scheduling when accomplish
management tasks can be accomplished.
Site-Specific Management
Management should be tailored to the priority and goals of each site. All areas
within the lake should be categorized as to use, restrictions, and priority. Based
on these categories, management techniques can be selected. For instance, swimming
beaches and boat launches are high-use areas, and should have a high priority. Wildlife
areas (e.g., refuges) probably have lower intensity use and also likely some restrictions
attached. Based on these categories, management techniques can be selected. The
high-priority, high-intensity use sites might justify high-cost management techniques
such as benthic barriers or diver-operated suction harvesting. Low-intensity use
areas might either remain untreated if resources are low, or would be categorized
for less expensive techniques such as herbicides. Likewise, areas with higher concentrations
of plants should receive more resources than areas with no plants or with acceptable
levels of infestation.
As dense colonies are brought under control, maintenance management approaches can
be used (Deschenes and Ludlow 1993). After a target plant species has entered a
system, continuous management will be required. However, under no circumstances
should management be discontinued once plant densities are low. If management techniques
are very successful, management may entail only monitoring the system and hand-removing
individuals that are occasionally found. Scale the control technique to the level
of infestation, the priority of the site, the use, and the availability of resources.
Evaluation
All management techniques should be evaluated on a routine schedule to make sure
that they are in fact effective in managing plants, cost-effective economically,
and in some cases, effective in managing plants in acceptable environmental thresholds.
Evaluations should be quantitative. This may require that expertise in plant-community
quantification be hired. Expertise can be sought either from environmental consulting
firms or, in some instances, from universities. Several quantification methods are
useful for evaluation; each has strengths and weaknesses (Table 3) . Transect methods,
biomass methods, and remote-sensing techniques are the most appropriate for evaluations.
Transect methods are most appropriate for examining the distribution of species
within an area, as well as for evaluating species richness or diversity (Madsen
and Bloomfield 1992, 1993; Madsen et al. 1994a; Titus 1993). Biomass techniques
are the most sensitive to changes in plant abundance; as such they are best for
evaluating the effectiveness of control techniques in given plots (Madsen 1993).
For best results, these evaluation studies should be based on rigorous experimental
principles (Spencer and Whitehand 1993). Remote sensing may provide a large-scale
image of the distribution (near the water’s surface, at least) of problem aquatic
plants. As such, it may help to evaluate the overall effectiveness of management
(Anderson 1990; Andrews et al. 1984; Frazier and Moore 1993). Remote sensing can
also be used to evaluate effects on nontarget plants (Farone and McNabb 1993). Suggested
practices for evaluating management techniques are presented in Table 3.
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Table 3
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Economic analyses have been woefully neglected in aquatic plant management planning.
For most, the extent of any cost/benefit analysis has been only an estimate of direct
treatment costs of different management techniques (Conyers and Cooke 1983). Although
these comparisons are important, the economic effects of aquatic plant management
are far broader. Detailed economic models and analyses are important for large management
programs (Henderson 1993, 1994, 1995). For instance, the 20-year-old British Columbia
program for managing aquatic plants was evaluated in 1991 (Newroth and Maxnuk 1993).
Results indicated a benefit:cost ratio of 11.3:1. A direct provincial contribution
of $265,000 in 1991 resulted in $3 million in provincial revenues. A contribution
of $360,000 by the province in 1990 also resulted in $85 million in tourist revenues,
1700 tourist industry jobs, and $360 million in real estate values. Typically, an
extensive cost:benefit analysis of aquatic plant management programs yields a high
benefit:cost ratio and an excellent return on the investment.
Other techniques may help in evaluating management techniques and in developing
management plans. Geographic Information Systems (GIS) are computer systems that
utilize digital base maps and overlay databases for categorizing information on
these maps. In other words, each point on the digital map can be labeled with various
attributes such as depth, abundance of a given plant species, or use intensity.
Although these systems require a large input of time, personnel, and money, for
larger management efforts they are well worth the investment. In addition, the GIS
can be combined with simple models to predict expected outcomes such as distribution
of plants within a lake (Remillard and Welch 1993). Data acquisition becomes important
when a GIS is being used. One piece of helpful equipment is the Global Positioning
System (GPS), which uses U.S. Department of Defense satellites to pinpoint (at various
levels of accuracy) the latitude, longitude, and elevation of the receiver. GPS
units can be used to map plant distributions, make bathymetric maps, record where
herbicides or other management techniques were applied, and find sampling locations
(Kress and Morgan 1995). Since these units have become quite inexpensive, simple
GPS receivers are within reach of almost any volunteer group.
Computer models in the past have been too complex for the average citizen or resource
manager to use for evaluating management practices. However, several user-friendly
models in Windows format were developed for resource managers through the U.S. Army
Corps of Engineers Aquatic Plant Control Research Program (APCRP) (Table 4). These
programs may be obtained by contacting the Assistant Director, Center for Aquatic
Plant Research and Technology (CAPRT), (ph. (601) 634-3722).
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Table 4
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Another excellent source of information on target and nontarget plants and their
management is the Aquatic Plant Information Retrieval System, operated by the University
of Florida's Center for Aquatic Plants (ph. (352) 392-1797). In addition to free
bibliographic searches, the Center has a variety of educational materials available.
An excellent example of integrating all aspects of prevention, assessment, evaluation,
and monitoring for the Province of British Columbia is presented by Newroth (1993).
Monitoring
Monitoring is distinct from evaluating plant-management success in that the goal
of monitoring should be to watch for ecosystem changes in target and nontarget plant
species, physical and environmental parameters, and other nontarget species such
as fishes and macroinvertebrates. Much of the monitoring efforts can be done by
volunteer citizens; several guides are available to assist (Michaud 1991). In addition,
several states such as New York (NYSDEC and FOLA, No Date) and Michigan (MIDNR 1990)
have statewide citizen-based monitoring programs in which the state will assist
in data analysis and the minimal costs involved. As with assessment of the plant
problem and evaluation of plant management techniques, occasional expert assistance
will probably be required.
In some instances, monitoring for the environmental impact of herbicides may be
desired. Herbicide residue levels may be measured directly in the water column or
hydrosoil by standard analytical techniques. In addition, immunoassay approaches
such as enzyme linked immunosorbent assay (ELISA) techniques are being developed
for selected herbicides. These techniques cost much less and can sensitively detect
presence or absence of a given herbicide, but, at present, accuracy is highly dependent
on the skill of the analyst. In some instances, the effects of herbicides on nontarget
plants may be of interest. Several techniques, including peroxidase analysis, have
been used to measure stress levels in aquatic plants (Byl et al. 1994; Sprecher
et al. 1993; Sprecher and Netherland 1995). The effectiveness of a herbicide on
the target plant may also be desired, particularly in the case of a long-acting
herbicide such as glyphosate or fluridone, which may take 30 to 90 days to be effective.
During this time, symptoms may even be present, but mortality may not occur. Phytoene
analyses are being prepared, in the case of fluridone treatments, to be able to
predict if plants will in fact die after the required waiting period (Sprecher and
Netherland 1995).
Education
Educational programs are not simply a frill of an aquatic plant management plan,
but are a long-term requirement for a successful plan. Education involves creating
public awareness of the problem and the potential for resolution, soliciting assistance
both for labor and resources, persuading key individuals and the public at large
concerning the management solutions decided on, and educating members of the management
planning group on the nature of the problems and their solutions. Many activities
can be used for education: workshops, public meetings, press conferences and releases,
classes, invited speakers, and so on. However, it is important to use all available
educational methods, including the media, to get the message out, to build public
consensus, and to educate group members and get their assistance in decision-making.