Kawainui Marsh Restoration Project
Through a joint project between the Army Corps of Engineers and the Hawaii Department of Forestry and Wildlife (DOFAW), the southern portion of Kawaianui Marsh was restored to create a habitat for four endangered Hawaiian waterbirds: Stilt, Moorhen, Coot and Koloa. The site consists of two ponds (North and South) excavated from upland pasture adjacent to Kawainui Marsh. Preferred habitat requirements (water depth, vegetation cover, etc.) for each of the listed waterbird species vary, therefore the depth of the ponds is designed to have a maximum range from 18 in. to 24 in.. Each of the two ponds are subdivided into five or six interior cells in an arrangement that follows the site topography to collectively drain downslope from mauka to makai. Rainfall is the primary source of water supplying the ponds supplemented by two solar powered pumps utilizing groundwater wells to provide adequate water circulation within the ponds. Ample water circulation is critical to prevent outbreaks caused by natural toxins produced by bacteria in pond soils.
Through a joint project with the Center for Conservation Research and Training, the Hawaii Department of Forestry and Wildlife has begun the implementation of continuous monitoring of the restored Kawainui Marsh pond environments through the use of wireless sensors. The wireless sensors will monitor local climate, water level and water quality in strategic locations in the Kawainui Marsh. These sensors will assist the DOFAW staff in optimizing habitat suitability for each of the managed waterbird species.
Water quality monitoring for favorable bird habitat and health at the Kawainui Restoration Ponds
Clean water is important to human and ecosystem health, and measuring chemical data (e.g. Dissolved Oxygen, Salinity and pH) is one method to determine water quality. Not only does water have to be safe for human use (drinking, commercial, recreation, etc.), most plants and animals have small ranges of temperature where they live best. Large fluctuations in water quality can affect the health of these organisms and often may result in death if exposed for prolonged periods of time. All states are required to meet specific water quality standards and continuously monitor coastal water, rivers, streams, lakes, wetlands, drinking and wastewater.
In freshwater streams in Hawaii, like Maunawili and Kahana Iki Streams, water quality parameters are very different than those found in Kawainui Marsh, and even more so in a closed pond system in the restoration area. Generally, the parameters increase or decrease as freshwater makes its way from high up in the mountains to the ocean, whether it is above or below ground (Table 1).
In the Kawainui Ponds, water quality is hand measured as a means to maintain favorable wetland bird habitat and health, and also to compare with other water sampling locations (Table 1).
In addition to semi-monthly hand sampling of each of the 11 ponds and drainage/evaporation, three near real-time monitoring stations were deployed to better understand changes in bird habitat conditions and water quality throughout the day (Figure 1).
Access to substantial volumes of fresh water (from wells / stream?) is critical to provide and maintain habitat quality for birds and to prevent outbreaks of avian botulism caused by deadly toxins produced by naturally occurring bacterium, Clostridium botulinum, in wetland sediments.
Figure 1. Kawainui pond cells and current configuration of monitoring stations. Handheld water quality monitoring sites = 1 – 15, W = real-time weather station and cellular gateway for all stations, sites 5 and 10 currently have water quality and pond height sensors. Dashed line = Fenceline. Opacity of ponds indicates height of water/evaporation from wet to dry season.
Researchers have suggested specific water quality parameters that can be measured to anticipate potential outbreaks of avian botulism in wetlands, including water temperature, pH, salinity, oxidation-reduction potential (ORP), dissolved oxygen (DO) and turbidity (NTU) (Table 1). “High risk” thresholds for these parameters that have been agreed upon in the literature and include combinations of the following:
- Temperature = 25°C- 40°C (or 60°F - 92°F). In Hawaii, water temperature varies by elevation and throughout the day. Stream headwaters tend to be coldest and warms from contact with land and as it is exposed to the sun, on it’s way to the ocean. However, closed systems like that in shallow ponds may experience warmer temperatures since water exposed to warmer air/land temperatures for longer periods of time. (Question: What can be done to reduce pond temperature in the afternoon, when it is highest?)
Hawaiian Common Moorhen / Gallinula chloropus sandvicensis / ‘Alae ‘ula (“red forehead”)
- pH = 7.5 - 9.0. pH levels in water bodies can fluctuate with temperature, and also as it moves towards the ocean. Freshwater streams tend to be between 6.0-7.0 but can drop by up to 0.5 lower during heavy rainfall / runoff (since rainfall is slightly acidic from dissolved carbon dioxide [H2O + CO2 = H2CO3 or carbonic acid] absorbed from air), and increase in pH as it reaches the ocean. pH in the Kawainui Ponds are often much higher than natural water bodies, and can be attributed mainly to the high concentrations of phytoplankton (greener ponds) and high rates of photosynthesis. Peak sunlight in the afternoon results in peak photosynthesis, and therefore decreases the amount of carbon dioxide and carbonic acid in the ponds. This is why we see pH decrease at night (high carbon dioxide/carbonic acid) and is at its lowest before sunrise, and highest in the day (high oxygen / low carbon dioxide) in our station data. (Question: What can be done to keep pH lower or more stable/neutral during the day?)
- Salinity = 1.0-5.0 ppt. Freshwater is almost absent of saline at high elevations, but increases slowly as it moves towards the ocean. As mentioned earlier, rain is slightly acidic and can physically erode rocks, which eventually result as dissolved salts and minerals that flow into streams and ends up in the ocean. The amount of salt in water is usually constant where tested, except during periods of heavy rain. (Question: What water source has the least amount of saline and how do we lower the concentration of salt in the ponds?)
Hawaiian Coot / Fulica alai / ‘Alae ke‘oke‘o
- ORP = low values or large drops when above thresholds are met. Oxidation Reduction Potential is the ability of a solution to gain or lose electrons, like how pH is determined by the transfer of hydrogen ions. ORP is sometimes used to measure water quality and disinfection/anti-microbial potential. Some types of waste related bacteria (e.g. E. coli) are reduced in number in higher ORP
systems, whereas water lower in ORP can be more habitable for those bacteria. Water ORP values from mauka to makai do not fluctuate as greatly as observed in the Kawainui Ponds, though values do increase to some extent after heavy rainfall and/or flooding. (Question: If large drop in ORP were to occur in the ponds, what would be the best action to take to increase it?)
- Dissolved Oxygen = Low values or large drops. DO is important for all aquatic animals to respire, and low concentrations can cause large die offs for species that cannot tolerate these conditions. DO is usually near 100 % saturation in high elevation streams, where water movement is often faster. DO levels may decrease when water movement decreases, like in low elevation streams, but can also increase in estuaries when high concentrations of phytoplankton are present. DO in the ponds is super saturated in the day (> 300%) and almost 0% at night, because of photosynthesis by phytoplankton during the day and respiration at night. Low oxygen environments (coupled with low ORP) in the ponds can increase the amount of nutrients in water by converting sediment solids to aqueous forms. (Question: What source of water would be best to stabilize DO in the ponds and why? What time of day should it be added to ponds?)
- High turbidity Turbidity, or a measurement of water cloudiness, generally increases as water moves from the mountains to estuaries. However, during heavy rainfall, sediment from the land creates runoff and causes high levels of turbidity. Sediment often settles in estuaries prior to reaching the ocean, but if it remains suspended, turbidity will be high. High primary productivity from phytoplankton may also increase turbidity measurements.
- Low Water Height: Intentionally lowering pond heights in a closed system can increase temperature, but does not necessarily result in poorer water quality readings for other parameters. Poorer water quality conditions can occur when water is lost from evaporation, when supplemental water of equal or better quality is not able to be added into the ponds. (Question: How do lower pond heights affect water temperature and salinity?
Hawaiian Stilt / Himantopus mexicanus knudseni / Ae‘o
- Dead/Decaying animals: large numbers of dead animals (e.g., fish and macro-invertebrates) and decaying organic matter, and conditions that would promote this, e.g. fluctuating water levels, agricultural pesticides/chemicals, raw sewage spill nutrient enhancement, should be monitored and minimized as well. Not only does this foul water quality, but also the decaying organisms
(particularly animals) are thought to serve as primary substrates for C. botulinum and toxin production. The toxin is transferred from these decomposing animals to invertebrate food items of waterfowl, e.g. zooplankton and maggots, and ultimately eaten by birds, which create more substrate for the bacteria to spread. The cycle is well documented and known as the “carcass-maggot cycle” of avian botulism.
- Higher temperatures have been found to magnify toxin concentration in carcass substrates as well as produce bacteria laden maggots at a higher rate.
- Station Alerts and Bird Monitoring: Over the past year, bird abundance / deaths were recorded and approximately compared with hand sampled and near real-time water quality data to determine if symptoms of avian botulism outbreaks were observed during periods when water quality thresholds were met or exceeded. Thresholds were met months prior to any bird deaths in 2014, however several bird deaths did occur when water quality observations exceeded thresholds the most, in summer months. Email and text alerts are currently being tested in the spring/summer of 2015, primarily to verify if bird deaths are observed during similar water quality parameters in 2014. If we can predict when avian outbreak risks are highest, better actions by wildlife managers can be taken to help treat sick birds and reduce the spread of disease. The ultimate goal would be to prevent outbreak conditions from occurring by actively being able to improve habitat and water quality for the birds.
Water Quality Sensors located in Kawainui Restoration Ponds (South) Located in Cell #5. (Double-click on video to see Cell #5 & 6)