It's Not Easy Being Green

 Initial feedback from the community survey can be found here.  

Under  Kentucky's Energy and Environment Cabinet, the Department of Environmental Protection Division of Water  has been monitoring water quality in Kentucky's streams, rivers, and reservoirs for more than 40 years.

Kentucky wetlands were added to the list of monitored water systems in 2010, initially for rapid assessment of wetland condition to inform permitting decisions. However, the program has since expanded to include measurements of biological integrity and wetland health assessments. More information on the program is found at   this link.  

Wetland monitoring protects much more than wetlands themselves, since wetlands filter out pollutants that may otherwise impact streams and rivers.

If streams and rivers are Earth’s circulatory system, then wetlands are its kidneys, retaining and removing pollutants such as fertilizers and heavy metals that would otherwise be carried downstream, through the Mississippi River basin, and ultimately to the Gulf of Mexico.

The next section below highlights a few interesting wetlands across the Commonwealth of Kentucky and was produced by the  Kentucky Division of Water .

Wetlands can be small but mighty! Small wetlands (~1-10 acres) still provide many of the ecosystem services that larger wetlands do, but on a community-level scale. 

There are 2.6-9 million small artificial ponds (surface area <10,000 m ² ) that contribute at least 20% of the total standing water area across the conterminous United States.

• Given their ubiquitous presence, these small ponds may make important contributions to carbon (C) budgets across North America
• Mounting evidence suggests that they emit greenhouse gases (GHG) at substantially higher rates per unit area when compared to larger bodies of water.

Specifically, most vegetated wetlands are  net sinks for carbon dioxide (CO ₂ ) , removing more CO ₂  from the atmosphere than they release. However, wetlands are also the  largest natural sources of methane (CH ₄ )  to the atmosphere.

Healthy wetlands can sequester and store large amounts of atmospheric greenhouse gases, primarily because photosynthesis by aquatic plants removes carbon dioxide (CO2) and converts it into sugar, which is then used to create new plant cells.

When those aquatic plants die and decompose, some CO2 is returned to the atmosphere. However, because rates of plant growth are faster than the rates at which they decompose, some of the carbon that they accumulated during their life is buried in sediments and locked away from the atmosphere. For this reason, the restoration and preservation of ponds and wetlands can be important nature-based solutions to help mitigate the emissions of greenhouse gases from the burning of fossil fuels.

However, when ponds and wetlands are impacted by fertilizer runoff, they can get overrun by harmful algal blooms and floating plants (e.g., duckweed). Wetlands in this state tend to emit large amounts of methane (CH4), a potent greenhouse gas. As a result, ponds receiving lots of fertilizers may not provide as many useful services and are less likely to function as storage vaults for atmospheric carbon.

A team of researchers from the University of Louisville are investigating different approaches for wetland assessment to inform carbon source-sink status of small ponds. Current work is focused in park areas around on Louisville, KY.

The project objectives include assessment of the GHG source-sink status of small constructed wetlands in Kentucky, the influence of the primary producer community on GHG uptake and emissions, and our ability to identify healthy small wetlands from science and community-based perspectives.

We are actively involved in collaboration with  Olmsted Parks Conservancy , and in partnership with  Louisville Metro Parks ,  Parklands of Floyds Fork ,  Cave Hill Cemetery , and  KY state parks. 

Our intent is to provide new insight into parkland management regarding small urban wetland systems, while also providing training in mapping, field techniques, sample collection, and data analysis to both undergraduate and graduate students at the University of Louisville. Additionally, our work involves a community science piece to compare varying perspectives of what a "healthy" wetland should look like.

We will use of high resolution  remotely sensed data  combined with field sampling techniques to determine wetland plant community composition, GHG source-sink status, and better targeting of wetlands in need of remediation. The GHG emissions are measured directly in three different ways: from the water surface, from escaping bubbles of methane and as they are produced in sediments. And while observers on the ground can readily see the green color caused by algal blooms, methods for rapid detection across broad spatial scales using remote sensing can enhance our ability to efficiently target “problem sites'' in need of remediation.

A critical part of our work involves feedback from the community. We want to hear from folks regarding their opinion of small pond conditions around different parks in Louisville. A participatory science perspective provides valuable insight for increasing knowledge and understanding of a given environmental system. It also provides a path forward to engage in meaningful ways on environmental monitoring efforts.

Citizen science, more inclusively community science, or participatory science are terms that represent a means of gathering data by way of stakeholders or members of the general public for scientific research.

At various ponds around Louisville there is signage requesting real-time photographs and quick feedback by individuals on pond conditions. An overview of the scientific research intent and participatory consent for the data collection is provided  here . Initial summaries of participatory responses in 2023 are outlined  here .

The last big component of this project involves using geospatial tools, notably  remote sensing , to measure and monitor conditions of the small urban wetlands.

Remote sensing is the acquisition of information about an object or phenomenon from a distance.

The video provides an overview of how we can depict Earth's surface using NASA  Landsat  bands over Everglades National Park in South Florida. Landsat provides the longest, continuous space-based record of mapping Earth's surface area. With remote sensing, we have a powerful way to easily and consistently collect data over a variety of scales and resolutions. A more in-depth overview of remote sensing is found  here .

In our project, we are interested in spatial scales that provide a detailed, high-resolution view of the small wetland ponds. To best capture pond conditions, imagery from the European Space Agency's  Sentinel-2  (10-60 m spatial resolution) or  Planet Labs  (3-5 m spatial resolution) provide useful satellite imaging platforms for mapping the land and wetland characteristics across the study area.

With remotely sensed data, we can look for patterns, shapes, and signals from the different colors in the image to identify wetland conditions.

Notably, specific wavelengths and combinations of those wavelengths provide insight on algae blooms versus floating aquatic vegetation. We can leverage spectral information from the visible (400-700 nm) and infrared (700 nm - 1100 nm) portions of the electromagnetic spectrum about plant chlorophyll and use that signal as a proxy for a variety of environmental monitoring applications including algae blooms and water quality monitoring

The typical human eye has color-detecting receptors that sense light in the 'blue' (420-440 nm), 'green' (534-550 nm) and 'red' (564-580 nm) ranges. We see water with high chlorophyll content looking green because it reflects strongly in the green part of the spectrum. A full on-line webinar that provides a great introduction to aquatic remote sensing is provided through the NASA Applied Remote Sensing Training Program. Watch the webinar  here .

Currently, we are investigating how to best associate satellite signals with algae and floating plants in the small ponds. To do this, we measure chlorophyll concentrations in as many ponds as possible in a single day, on days when specific satellites are passing overhead. In-situ measures of chlorophyll along with measurements for dissolved organic matter and water turbidity are then compared with remotely sensed signals concurrent with the sampling.

We can use spectral reflectance signals from the satellite imagery to match to each of the above surface conditions as well as open surface water to start to characterize wetland conditions across larger areas and with more time steps than feasible using field sampling alone. Below is a figure illustrating the spectral separation of different wetland surfaces from an October 2021 image of the pond in Chickasaw Park in west Louisville.

These data will ultimately help to determine if remotely-sensed blooms of algae or floating plants can be used as indicators of greenhouse gas emissions hotspots. The project will continue through 2024 and is funded from the  Kentucky Water Resources Research Institute . Any questions should be directed to co-investigators, Dr.  Andrew Mehring  (UofL Biology, andrew.mehring@louisville.edu) and/or  Andrea Gaughan  (UofL Geographic and Environmental Sciences, ae.gaughan@louisville.edu).