Thursday, January 17, 2013

Patterns of aquatic plant species domination

In an earlier blog post, we informed you of collaborative research in which CI is involved.  We’ve touched on how species presence/absence surveys using methods like point-intercept and full system acoustic surveys of abundance can be combined to fully understand the dynamics of aquatic plant communities and how they are responding to range of “forces.”  These forces may be natural like seasonal or interannual variability, human induced but unintentional like accelerated eutrophication, or the introduction of invasive species, or intentional management interventions to control nuisance aquatic plant growth.  Whatever the case, entire lake ecosystems are likely to be affected these forces including plant species composition, abundance, and spatial patterns of plant growth.

We can generally expect a bell curve-like response of plant growth at differing levels of productivity (Figure 1).  In nutrient-poor oligotrophic lakes, aquatic plants are typically never very abundant because of nutrient limitations or sediment hardness.  At the other side of the spectrum in overly productive or hypereutrophic systems, the lake is often too murky from algae growth or sediment suspension to support much plant growth.  Goldilocks finds her sweet spot in moderately productive meso- or eutrophic lakes (Figure 1).  The cumulative effects of various stressors continually move the ball towards the right of the productivity curve where thresholds are being approached and sometimes breached.  We've spoken about this resilience issue also in a previous post.

Figure 1. Conceptual model describing general patterns of aquatic plant abundance  in  shallow to moderately  deep lakes as a function of lake productivity.  O = Oligotrophic or low nutrient levels; M = Mesotrophic or moderate nutrient levels; E = Eutrophic or high nutrient levels; HE = Hypereutrophic or really high nutrient levels.

Likewise, we could replace the Y-axis in Figure 1 with Species Richness and we’d have the same conceptual model and predictions for how lakes should respond to environmental or human stressors.  Maybe this brings back memories of the Intermediate Disturbance Hypothesis a la Connell (1978) for our readers with an academic history in Ecology?

Having understood these patterns, researchers and managers have done much work to assess aquatic plant communities, make prescriptions on their management or conservation, and evaluate outcomes of management efforts.  Still, assessment techniques have generally been focused either on species occurrence patterns or gross plant abundance patterns but rarely both, and especially at the whole-lake scale.

For instance, the point-intercept method has been used to describe species occurrence patterns in many systems throughout the upper Midwestern US (Madsen et al. 2002, Beck et al. 2010, Mikulyuk et al 2010, Valley and Heiskary 2012).  Indeed, this work and many other studies not cited here has contributed great knowledge on factors contributing patterns of what species grow where.  But they can’t tell us “how much.”

In contrast, hydroacoustics assessments of plant abundance has shed light on how various factors affect patterns of plant abundance in lakes (Valley and Drake 2007, Winfield et al. 2007, Zhu et al. 2007, Sabol et al. 2009, Netherland and Jones 2012).  So hydroacoustics can tell us “how much” but generally not what species grow where unless you are dealing with monocultures.

Duh! Combine results from both methods!

Although it seems obvious regarding the proper solution, prior to today, there were many budget and technological difficulties that made combining both species and abundance surveys at the whole lake scale not very feasible.

Most of these barriers were with the acoustic techniques.  Equipment was costly, it required a lot of specialized training to operate and make sense of the data, you needed powerful computers and a lot of data storage capacity.  

Innovations in acoustic and computing technology has smashed these barriers and now valuable high resolution data on aquatic plant abundance can be logged passively to a $650 depth finder while you conduct your species occurrence surveys.  When you return from the field, just add “upload sonar data” to your list of things to tidy up before heading home for dinner.  30-min later all the abundance data will be waiting in the queue to be combined with your frequency of occurrence species data.

Combining point-intercept and acoustic data into meaningful statistics

In our point-intercept on steroids post we described how to append a biovolume column to your point-intercept data file.  In this investigation we have now taken matters to the next step and defined a potentially useful metric (Dominance) and evaluated its utility across several Minnesota and Wisconsin Lakes and one natural North Carolina Lake (Table 1).

Table 1.  Lakes part of a collaborative study demonstrating a technique for quantifying the impact of individual species on plant abundance patterns.  Zmax = max depth in feet; Prod. = productivity as described in Figure 1.  Invasive plants include Eurasian watermilfoil (EWM), Curly-leaf pondweed (CLP), and Hydrilla (HYD).
What we define as Dominance is a metric that ranges from 0 (no plant growth at all) to 1 (surface growth of one species).  The number of species combined with the biovolume at a survey point determines the dominance value.  So at each survey point:

Species1 / Total Species* x Biovolume = Dominance

*Excludes emergent and free-floating species

This means that 10 species sampled at point X with a biovolume of 100% only gets a value of 0.1.  In many natural glacial lakes, surface growth of aquatic plants is common in shallow areas, but typically, many species contribute to the local assemblage.  In a disturbed or invasive dominated lake, surface growth is common but usually only 1-2 species (e.g., D = 1 and 0.5 respectively) contribute to these dense beds.

Figure 2 demonstrates what we find in lakes that range from oligotrophic, uninfested lakes to borderline hypereutrophic infested lakes.
Figure 2. Patterns in aquatic plant growth in lakes that span a range of productivity (ordered from left to right - see Figure 1 for productivity definitions).  BVw is the average total biovolume in the surveyed areas generated from ciBioBase grid reports. Freq. Monocultures is the frequency of species survey points that had only 1 or 2 species and growth was near the water surface.  BV Natives is the biovolume of species survey points where only native submersed or floating leaf plants were growing.  BV Invasives is the biovolume at sites with invasive species present.
First, with the exception of bog stained Waccamaw that naturally depresses plant growth, the overall abundance of plants as expressed as average biovolume (Blue bars- BVw) by in large follows the bell shaped curve in Figure 1.  Second, the biovolume where only native plants grow is pretty stable across all lake types (again excluding Waccamaw) and invasives (in this case Eurasian watermilfoil) push the biovolume higher.  This patterns of biovolume at surveyed points give us another quantitative indicator about the actual impact of invasives and could serve as a benchmark for management objectives.  Third, the red bars tell us how frequent during each survey we saw surface growing beds of one species.  Interestingly, the frequency increases as the lakes become more productive with invasive plants.

Lake Wingra – an extreme example of Eurasian watermilfoil domination

Lake Wingra is a shallow, eutrophic lake near the campus of University of Wisconsin in Madison, Wisconsin.  Wingra resides in an urban watershed and the lake today is a reflection of a long legacy of watershed and in lake impacts from high runoff, sedimentation, and invasive species proliferation such as common carp and Eurasian watermilfoil.  More information on this lake can be found here.

Today, the lake is dominated by Eurasian watermilfoil (there's that word again: dominated).  What we are doing now is putting numbers behind this descriptive word so the situation can be improved.

So what does "domination" mean in Wingra?  It means that 50% of the sampled points in the lake had only Eurasian watermilfoil or one other species growing to the surface (Figure 2).  It means that 130 acres of the 281 total acres mapped (45%) were essentially surface-growing monocultures of Eurasian watermilfoil (Figure 3).  These represent objective benchmarks that form the foundation of solutions.  It’s probably not a stretch to assume that 129 acres of surface growing Eurasian watermilfoil is not desirable.  With the tools described here local managers and citizens can work out what is desirable and take measures to get there.  But getting there requires objective, repeatable assessment methods that shed light on both species AND abundance patterns.
Figure 3.  Contours (yellow) delineating the extent of surface-growing Eurasian watermilfoil  beds on Lake Wingra (Dane Co. WI).  The background map is a heat map of aquatic plant biovolume collected with a Lowrance HDS-5 and processed with ciBiobBase.  Areas of red is vegetation growth near the surface.  The few red areas outside of the yellow contour lines represent areas where 1 or more native species contributed to the surface growth.

The future: national risk assessment models

Contour Innovations is currently developing data import capabilities to overlay species surveys on ciBioBase maps.  This will have immediate local benefits for our clients, but the real power of such functionality is the building of a powerful national database of species and abundance surveys.  This can lead to independent research efforts to model aquatic plant growth patterns and model risk of certain aquatic systems to domination by an invasive aquatic plant species.  But a critical mass of cooperation by the water and fisheries resource community including academia and public and private institutions is needed to develop robust models.  Contact us if you are interested in being a part of this effort.  We will be taking this concept to the road at the Midwest Aquatic Plant Management Society meeting in Cleveland, Western Aquatic Plant Management Society in Idaho, Minnesota Chapter of the American Fisheries Society in St. Cloud MN and other to be determined venues.

Ray Valley
Chief Aquatic Biologist

Literature Cited

Beck, M. W., L. Hatch, B. Vondracek, and R. D. Valley. 2010. Development of a macrophyte-based index of biotic integrity for Minnesota lakes. Ecological Indicators 10:968-979.

Connell, J. H. 1978. Diversity in tropical rain forests and coral reefs. Science 199:1302–1310.

Madsen, J. D., K. D. Getsinger, R. M. Stewart, and C. O. Owens. 2002. Whole Lake fluridone treatments for selective control of Eurasian watermilfoil: II. impacts on submersed plant communities. Lake and Reservoir Management 18:191–200.

Mikulyuk, A., J. Hauxwell, P. Rasmussen, S. Knight, K. I. Wagner, M. E. Nault, and D. Ridgely. 2010. Testing a methodology for assessing plant communities in temperate inland lakes. Lake and Reservoir Management 26:54–62. doi: 

Sabol, B. M., J. Kannenberg, and J. G. Skogerboe. 2009. Integrating Acoustic Mapping into Operational Aquatic Plant Management : a case study in Wisconsin. Journal of Aquatic Plant Management 47:44–52.

Valley, R. D., and M. T. Drake. 2007. What does resilience of a clear-water state in lakes mean for the spatial heterogeneity of submersed macrophyte biovolume? Aquatic Botany 87:307–319.

Valley, R. D., and S. Heiskary. 2012. Short-term declines in curlyleaf pondweed in Minnesota: potential influences of snowfall. Lake and Reservoir Management 28:338–345.

Winfield, I. J., C. Onoufriou, M. J. O’Connell, M. Godlewska, R. M. Ward, A. F. Brown, and M. L. Yallop. 2007. Assessment in two shallow lakes of a hydroacoustic system for surveying aquatic macrophytes. Hydrobiologia 584:111–119.

Zhu, B., D. G. Fitzgerald, S. B. Hoskins, L. G. Rudstam, C. M. Mayer, and E. L. Mills. 2007. Quantification of historical changes of submerged aquatic vegetation cover in two bays of Lake Ontario with three complementary methods. Journal of Great Lakes Research 33:122–135.

Monday, January 14, 2013

An Unfair War with Aquatic Invasive Species


The Importance of Aquatic Vegetation Abundance Mapping and Long Term Monitoring from a Layman’s Perspective

 

From a layman’s point of view it can be very difficult to understand the importance of lake weeds as they relate to aquatic invasive species (AIS).  I should know . . . I’m a layman.  I started asking questions, and it turns out it’s a bit more complex than I thought.  Sure, I want the Minnesota Lakes I love to be clear with tons of fish, but do we really need these weeds?  Of course we need some “weeds” (“aquatic plants”), and, if you get rid of too many you can throw the entire lake ecology out of balance for years.  When I asked how much is a good amount and how it is being tracked in Minnesota I was disappointed with the answer.  During my time working for the software company Contour Innovations, focusing on automated lake mapping, I've had the pleasure of working with some of the most talented aquatic biologists in the Country, both in-house and through our customer base.  I’ve spent the last few years learning the language and attempting to catch on from a neutral, outsider’s perspective.  Slowly, I realized that the complicated topic could be effectively communicated to anyone that cares about and has an interest in water quality . . . which should technically be everyone.

Let’s face it, the DNR has done a great job demonizing invasive species for good reason and with some positive results.  There’s more awareness now and budgets in place to attempt to manage the spread and introduction.  But, eradicating AIS once introduced into a lake is only half the story.  . .

I’ve learned a lot over the last few years but I still had some questions:  Why should our customers really care about the total habitat when Eurasian Water Milfoil has already invaded their lake?  Don’t they just want to know where the Milfoil is so they can get rid of it?  If a monitoring program can’t distinguish between species does it still have a use in aquatic research or management?  I originally thought that identifying where the Milfoil is located is key, but I actually found the opposite to be true.  If we live by the idea that “AIS are bad and should be eliminated at all costs,” wouldn’t the results be easier to obtain? 

The concepts of ecosystem balance are extremely complex but vital.  After early discussions with our biologists it become clear to me that abundance is one of the most important metrics to consider when monitoring water quality and lake health.  This remains true if an invasive species has already been introduced or it’s just knocking on the doorstep.  We need to focus our analysis on total abundance and the overall aquatic habitat instead of speciation as a sole predictor of lake health.  What really matters is knowing if your lake is at risk of the negative impacts from invasive species and if your lake ecology is within certain “healthy” parameters.  A lake’s resilience to invasive species and current water quality regime is going to be a major indicator of lake health and prospects for the future.  It’s also important to quantify your management interventions and determine if they are having their desired effect.  These were difficult questions to answer in the past. 

Invasive species are coming.   We can try to stop it but more likely we’re just delaying it.  The reason these species are thriving is because they’re designed to thrive.  With the right conditions they can easily steal the resources required to grow from other plants, effectively eliminating competition from the lake.  They’re opportunistic and the microscopic amount required for infestation is astonishing.  We should accept this fact and be realistic about what we’re dealing with.  It doesn’t mean we roll over and stop the cleaning stations or citations for failing to drain your bilge, but a proactive management and monitoring plan is a good idea.   

Let’s understand our lake’s resilience and identify if it’s at risk.  Let’s get our resource managers identifying which lakes need close attention and devote our stretched budgets to the ones that need it.  The chips are already stacked against us and without good quantitative data, they’re stacked even further.   With mismanaged resources it becomes a war we can’t win.

At a certain level of productivity, an invasive species will win the war against a diverse ecological aquatic habitat and turn into a lake of a single species.  This isn't a good thing for any lake ecosystem or water quality.  It’s all about balance and a healthy lake habitat can help keep an infestation in check.  It’s also possible that certain management techniques could push a lake towards a higher risk scenario if decisions were made without quality abundance data.  Understanding the risks of this happening are key in designing a management plan to be proactive instead of reactive.  Identifying hot spots in abundance and potential causes could be more important than identifying where the invasive species exist.  The best thing is that it’s never too early or late to start. 

The entire ecosystem is tied together.   The cumulative effect of lake stressors can lead to the low resilience required for an invasive species to thrive.  Identifying the stressors and dealing with them could prove more valuable than eliminating an invasive species.  Much like a healthy body can deal with the flu virus better than an unhealthy one, a lake with good shorelines, healthy fish communities, and healthy diversity of plant abundance can keep an infestation in check.  In certain conditions, taking plants out of the lake might be a bad decision that could have a negative effect on lake ecology depending on the lake regime and characteristics of the lake.  

In fact, there are ideal targets and optimal or idea habitat levels and conditions.  Our own Ray Valley, a 10 year veteran of the Minnesota DNR, has devoted a majority of his career to habitat monitoring and interactions between plant abundance, fish, lake resilience and relationships to water quality.  His research on ecosystem balance, namely lake resilience, is instrumental in understanding what’s really happening in a lake and when lakes are at risk.  Much of this is actually tied to plant abundance and changes over time.

Through a long term monitoring program it’s possible to identify the red flags.  Plant abundance growing at deeper depths from year to year could show an increase in water clarity allowing more light penetration.  This might be caused by a recent zebra mussel infestation or a shift in the lakes ecology.  Regardless, something as simple as the depth aquatic plants grow tells us a ton about the direction the lake is going.  In another example, unusual increases in plant abundance in specific areas could indicate, among other things, a home with a leaking septic tank on the lake, a change in the landscape, changes in sedimentation, a run-off issue or a bigger problem upstream.  All of these, left unchecked, could cause more problems for the lakes balance and resilience leading to higher risk of negative impacts of an invasive species introduction.   These changes don’t show up in a visual reconnaissance, presence/absence surveys with a rake, or a single map.   But getting these items resolved could be the management technique that keeps an invasive species from dominating a lake habitat in the future and early detection of these problems could prevent an unfair fight against AIS in the future.

Complete dominance of an invasive species is another story but it’s also the exception.  I’ve seen a number of groups continue to dump massive amounts of money into management without quantitative goals or the ability to effectively quantify the whether they are meeting their management expectations.  Maybe we’re not asking the right types of questions or maybe the technology didn’t exist to get the information we need.  No one is at fault yet.  Once the dialog shifts away from hysterical talking points and towards pragmatic management approaches, we’ll start making real strides in getting ahead of AIS and start achieving improvements in our precious lakes.

So where do we start?  With crowd-sourced solutions like ciBioBase.com we can all start getting the volume of data we really need to have this realistic and proactive discussion.  With cloud computing we’ve broadened the base of individuals that can participate allowing passionate home owner groups to take matters into their own hands instead of waiting for an understaffed DNR.   Aquatic plant abundance maps that took a highly trained hydrographer a week or more and to complete can be done by anyone with a boat, a depth finder and GPS, and 20 minutes for computers do the work of processing the collected data.  This is the future of monitoring and lake management.  There are no longer barriers to getting the kind of data we need for identifying the red flags, eliminating stressors and improving lakes across Minnesota and the globe.
So, let’s understand the lakes heartbeat first.  Let’s get a clear picture of the lakes resilience and its current status for optimal health.  Then we move forward to a future with cleaner lakes.

This article represents and aggregation of my thoughts as I’ve journeyed through this industry and tried to learn the ropes.   This is merely an appeal to think differently about our lakes, expectations, and what the future holds.  The future of our most important resource is brightest if we take a step back, think about what we’re doing and where we need to go.
 
Let’s have those realistic and proactive discussions with real data . . .
                                                         -Matt Johnson, CEO, Contour Innovations, LLC

 

CONTOUR INNOVATIONS AND CIBIOBASE

ciBioBase (ciBioBase.com) removes the time and labor required to create aquatic maps! ciBioBase leverages log file formats recorded to SD cards using today’s Lowrance™ brand depth finders and chart plotters. Data you collect while on the water is uploaded to an online account where it is processed by our servers automatically! We rely on automation to make vegetation mapping cost effective by reducing the technical skills, staff, and hours to produce vegetation abundance maps from raw sonar collection. With the human element gone, you get accurate and objective mapping at lightening speeds! The result is a uniform and objective output all over the world!
I’m proud to be a part of this step in the right direction of a positive future for lake management and overall quality of our most precious resource.  We’re shaking things up and this is a time when everyone benefits.  We work as a huge team to define the best uses and features of one of our products, BioBase, to change the lake management industry.  We’re using expert opinions and powerful cloud computing to create amazing contour and vegetation maps and gain important quantitative metrics of lake health.

Our Company has a culture that considers its social responsibility and contribution.  Our sales team is motivated by how they are changing the future of lakes and resources management.  I was most intrigued by what we might be contributing to the future of a resource that means so much to me.  I’m still intrigued!