Graduate Student Research 2016
- Humpback Whale Vocal Communications Between Mothers and Calves
- Wastewater’s Influence on Coastal Groundwater Quality and the Health of Coral Reefs in Maunalua Bay, O‘ahu
- Attack of the Drones: Characterizing Groundwater Discharge on Maui Using the Latest Research Tools
- Simulating Sea-Level Rise Induced Groundwater Inundation of O‘ahu’s Most Highly Developed Coastal Zones
- 2015 Peter J. Rappa Sustainable Coastal Development Fellow
“Thar she blows!”
Lahaina, Maui was a bustling port for whaling ships in the 1800s, called the whaling capital of the world during the mid-1800s. Nowadays it is still a popular destination for whales, but for the activity of whale watching rather than hunting. A portion of the North Pacific humpback whale (Megaptera novaeangliae) population migrates every winter from the cold waters off Alaska and the Bering Sea to the warm waters of Hawai‘i to give birth, begin raising their calves, and mate. The Maui Nui area between Maui, Kaho‘olawe, Lāna‘i, and Moloka‘i is a particularly popular area for mother-calf pairs due to the warm shallow waters.
Although whaling has decreased significantly since the 1982 moratorium imposed by the International Whaling Commission, humans still pose a threat to all whales. Some threats include loss of food resources due to overfishing, pollution, and climate change, risk of entanglement from fishing lines and gear, ship strikes from increased number of vessels in the ocean, and disturbance from human generated sounds. We are interested in studying the effects of human generated sound. In Hawai‘i underwater noise may come from small recreational or fishing boats, whale watching boats, large barges and cargo ships, military ships, sonar and fish-finders, and coastal construction. In particular, we want to know what effects underwater noise may have on humpback whale mother-calf pairs.
Less is known about humpback whale vocalizations termed “social sounds,” used to communicate when feeding or traveling in groups, than “song,” comprehensively studied since the 1970s. In addition, little is known about vocal development, or how whales learn to make their many song and social vocalizations. Since whales produce so many types of sounds it is logical to assume the sounds are essential for communication. Learning is most likely involved because of the wide diversity of sounds produced; vocalizations are not limited to stereotyped calls produced by all animals and appear to be important in a social context.
How do whales learn to make the varied sounds they use for communication? What are the important aspects of these sounds? We can speculate based on what we know about other species. However, it is almost impossible to know exactly how a humpback whale learns, especially when we still do not know how they produce sounds or what sounds they can hear! We also have no way of knowing what aspects of a sound are most important to a whale. What we can do is characterize the sounds the humpback whale calves make by determining parameters such as frequency (pitch), amplitude (loudness), and type (frequency modulated, amplitude modulated, or burst pulse). Pairing acoustics with a calibrated underwater video system, we can examine whether the calves develop more complex sounds as they grow older, or if they produce fully formed sounds from birth. The video can also be examined for behavioral context of sound production. For example, does the calf call to the mother when separated, or together? Does it make certain sounds when disturbed by a boat or swimmer?
The characterization of humpback whale sounds produced by calves and mothers also allows us to determine possible effects of human made noises. If they make sounds in the same range as local whale watching boat engines, their communications are more likely to be obscured than if they call at higher or lower frequencies or they may be more likely to be affected by the lower frequency noise from large cargo ships. Because vocalizations are apparently very important to humpback whales, it is imperative for the whales to be able to hear each other, especially when a calf is young and in the process of learning.
To learn about the sounds and behavior of humpback whales, we use suction cup acoustic recording tags placed on the whale, an array of underwater microphones (hydrophones), underwater video, photo identification, and behavioral observations. Throughout the last three humpback whale seasons, I have deployed tags on three calves and seven mothers. So far, analysis of the sound recordings from the tags indicate that both mothers and calves are relatively quiet. In fact, one 3.5 hour recording from a mother contained no vocalizations! Vocalizations also tend to occur in bouts, rather than being evenly spaced throughout the recording. The vocalizations recorded from calves so far show much less variation than song units, and appear to be largely stereotyped. Vocalizations recorded from mothers show slightly more variation in sound parameters. In the ongoing analysis, I plan to develop a more robust categorization system and to correlate vocalization production to behavioral state and location in the water column. If vocalizations are correlated with certain behavioral states, acoustic disruption may be more likely to occur when the whales are exhibiting certain behaviors such as traveling or resting. In the future, vocalization parameters will be compared to recordings of local whale-watching boats. This will allow us to determine if boat engine noise is likely to mask the social sounds of mothers and calves, which could jeopardize the calf’s learning or safety. I hope to continue this line of research to collect enough samples to create a timeline of vocal development, furthering the understanding of whale behavior and interaction with humans.
Groundwater is vitally important in Hawai‘i as it supplies over 99 percent of our drinking water. Beyond its consumptive uses, groundwater also creates unique coastal estuaries in the Hawaiian Islands – areas where groundwater mixes with sea water in coastal embayments inhabited by corals. My research focuses on three of these “coastal estuaries” in Maunalua Bay, O‘ahu: Black Point, Kawaikui, and Wailupe. Previous studies in the area have documented high nutrient loads (nearly 200 times greater than oceanic concentrations) in groundwater discharging along the coast at Black Point. Elevated nutrient concentrations can affect a range of marine organisms in Hawai‘i since our ocean water is typically nutrient-poor. Many algal species thrive in these nutrient-rich conditions while corals suffer from increasingly poor water quality and decreased sunlight availability as algae clouds the water column.
In January 2015, working alongside my primary advisor, Dr. Henrietta Dulai, I completed field surveys at each location to monitor the nutrient concentrations in groundwater and the surrounding coastal water. I also sampled three terrestrial groundwater wells in the Black Point area to see how land-use may be affecting groundwater chemistry as it traveled mauka (toward the mountains) to makai (toward the sea). Black Point’s groundwater is entrained in an entirely separate storage unit, or aquifer, than that of Wailupe’s and Kawaikui’s groundwater. The implications of this are that land-use practices that impact groundwater in the Black Point area will not affect the neighboring Kawaikui and Wailupe field sites. Similar to past studies, we found that nutrient loads were highest in coastal groundwater in the Black Point area whereas Wailupe’s and Kawaikui’s groundwater nutrients resembled concentrations commonly observed upgradient of development. So, where are the nutrients at Black Point coming from?
To answer this question, I looked at nitrate stable isotopes which are commonly used to track sources of nitrogen in water. The resulting stable isotope values can tell scientists whether the nitrate originates from a waste source or fertilizer, for example. As such, I also sampled the upland wells and groundwater sources at each of my three coastal field sites for these water constituents. My results suggested that Black Point’s elevated nutrient loads were the result of wastewater inputs. Both Wailupe’s and Kawaikui’s groundwater showed no signs of wastewater influence, however.
In Hawai‘i, on-site sewage disposal systems (OSDS) are a common alternative to wastewater treatment facilities for disposing of household waste. Cesspools are the dominant form of OSDS in Hawai‘i, with an estimated 14,000 units on the island of O‘ahu alone. A cesspool is an unlined underground pit that directly receives household waste. Little to no primary treatment of sewage occurs in these units. This untreated wastewater is free to percolate down into the water table where it can be readily conveyed to the ocean via groundwater.
Working with Dr. Robert Whittier at the Hawai‘i State Department of Health, I examined the locations and density of OSDS in each field area. Black Point’s aquifer contained 328 OSDS, primarily cesspools, and nearly 120 of these were within 1 km of the coast. For comparison, the aquifer feeding both Kawaikui and Wailupe contained a total of just 51 units. To confirm the wastewater hypothesis, I also utilized a computer model that estimated the relative volumetric contribution of wastewater to groundwater in the aquifer and associated nutrient loads. The results from this model aligned with my geochemical data. It was clear that the elevated nutrients in the groundwater discharging at Black Point were indeed influenced by wastewater.
Studies have shown that high nutrient concentrations may also influence the ecological composition of reefs by shifting community dominance from coral to algae. This shift from coral to algal dominance results in changes to carbonate system chemistry. I completed two 24-hour surveys at Black Point and Wailupe in the fall to examine night-day changes in carbonate chemistry. My preliminary results show larger fluctuations in carbonate system parameters at Black Point compared to Wailupe, evidence that the excess nutrients in Black Point groundwater may be fueling biological activity.
Hawai‘i recently passed HAR 62, legislation prohibiting the construction of new cesspools. The future of OSDS in Hawai‘i and how to handle wastewater leachate from established OSDS such as cesspools is still widely debated though. This research is an important aid for community members and lawmakers as it will help elucidate the potential effects of OSDS-derived wastewater on our nearshore environment. Additionally, it is one of the first studies to document wastewater originating from OSDS discharging into Hawai‘i’s coastal ocean.
The bay below was about as idyllic as it gets, but I was focused on the tiny object in the sky above when I heard someone say “that thing sure is noisy!” When I looked over to see who made that statement I saw a lady staring at me with a look of annoyance on her face. I responded back, “you should hear it when it’s actually close, but it’s for a good cause. I’m with the University of Hawai‘i doing coastal research.” There was an initial look of bewilderment as you could tell that was not the answer she was expecting. The research drone I was flying was some 400 feet above over water and could barely be heard from that altitude, so I knew her comment probably stemmed from a previous interaction with a drone. This was a wonderful opportunity to counter her perception of drones or unmanned aerial vehicles (UAV) with information that would help her see the beneficial side of the dramatic increase in UAV usage that is happening these days. I continued to explain that I was a graduate student at the University of Hawai‘i at Mānoa working on my master’s degree. Her demeanor quickly changed from annoyance to one of intrigue as she watched me fly the UAV and land it in the clearing behind us. Once it was on the ground, I was able to focus on having an engaging conversation about how UAVs are being used in the sciences, but more specifically my graduate research.
I am studying submarine groundwater discharge (SGD), which is an important part of the water cycle that continuously supplies new naturally occurring nutrients to the coastal waters of Hawai‘i. However, increased urbanization and agricultural development have the potential to introduce excess nutrients and other dissolved components into the groundwater that flows beneath such areas and carry them to the coastline where groundwater seeps out into the ocean as SGD. The island of Maui has been the focus of SGD research for over 20 years due to the rapid decline of coral reefs as well as recurring macroalgal blooms that not only contribute to coral loss but also foul picturesque beaches that have cost Maui County millions of dollars in lost revenue. This has been a big concern for coastal managers like the State of Hawai‘i Division of Aquatic Resources as they make decisions on how best to care for the dynamic yet fragile ecosystems that are a huge draw for tourists.
SGD is intrinsically difficult to detect, and while hydrological budgets and groundwater models can provide estimated discharge rates on a regional scale, they are unable to provide researchers with specific locations of discharge for detailed analysis. My research efforts therefore initially focused on mapping large portions of the Maui coastline using thermal infrared (TIR) imagery from an airplane to locate specific areas where cold groundwater is discharging into the warmer coastal waters. These efforts highlighted key areas where SGD is prevalent, however, imagery from one single flight is extremely limited in its ability to provide quantitative information about the temporal nature of SGD. It was at this point in my research that the idea of possibly using a drone to obtain imagery at a much higher frequency became a reality.
The rise of unmanned aerial vehicles (UAVs) has seen a drastic increase of interest due to the possible uses for research that exist. The most common UAVs are multi-copter radio-controlled vehicles under one meter in length. They are capable of taking off and landing in extremely tight spaces and able to hover over areas for upwards of 15-20 minutes. They are inexpensive to operate and can fly over the same area repeatedly as they can be re-launched within minutes with the change of a battery. UAVs also have the ability to be programmed to fly specific routes based on GPS waypoints and image the exact same area as often as needed. These aspects make UAVs an ideal platform for mounting a thermal infrared camera to obtain time series imagery of SGD.
My advisor and I quickly educated ourselves on the latest UAV technology and eventually managed to obtain the necessary UAV research equipment. The idea was to combine it with the second phase of my research, time series radon measurements for SGD flow rate quantification and associated nutrient fluxes. This had never been done before, but the benefits were well worth the steep learning curve that comes with attempting something new. Radon time series deployments provide valuable information about the amount of groundwater that discharges into the coastal zones and the associated nutrient concentrations that are brought to these sensitive ecosystems. The incorporation of simultaneous time series TIR imagery from a UAV with time series radon deployments further enabled us to elucidate the variable nature of SGD by giving us the ability to see how point source discharge and diffuse seepage changes both in magnitude and spatial distribution over the course of a tidal cycle and within various coastal conditions. The most significant aspect however, is that this research has shown that UAVs have quickly become a valuable research tool for obtaining inexpensive TIR imagery of the constantly changing nature of SGD within the dynamic coastal zone. It is clear that such technological advances will empower land managers to make the best decisions possible in regards to the sustainability of Maui’s valuable coastal resources.
Local mean sea level in Honolulu, Hawai‘i is expected to rise 0.23 – 0.38 meters by mid-century and 0.63 – 1.14 meters by the year 2100. Groundwater in low-lying coastal areas is closely tied to oscillations of the ocean surface; hence, it can be assumed that as sea-level rise (SLR) continues, the water table will be elevated by a similar magnitude.
Honolulu’s coastal zones have generally narrow unsaturated soil space (vadose zones) such that many construction projects working below grade require dewatering of worksites. Tidally influenced groundwater and narrow vadose zones produce localized temporary flooding during extreme tide events. Since a 20 centimeter tide above the mean higher high water (MHHW) point produces flooding in Honolulu, as SLR continues, vadose zones will become progressively narrowed or eliminated altogether, thus resulting in groundwater inundation (GWI).
As the water table breaches the elevation of built infrastructure, flood damage will ensue. Underground infrastructure such as basements and an array of essential utilities (sewer mains, vented utility corridors, and cesspools) will be the first to be compromised by inundation. This is especially concerning for corroded sewer mains due to the likelihood of sewage based contamination of groundwater. Since much of this infrastructure was installed between the 1930s and the 1950s, sewer mains in Honolulu experience occasional structural failure due to corrosion.
The threat of GWI has not been considered in most adaptation planning. However, the state has relayed its concern regarding the threat that GWI poses to miles of underground infrastructure. The conversation has begun in determining whether anticipatory climate change adaptive design standards should be adopted. It is agreed that adopting such standards is prudent; however, the lack of hazard projections and mapping is the limiting factor.
This research is quantifying the extent of GWI projected for the years 2050 and 2100 along O‘ahu’s populous and low lying regions of Waikīkī, Kaka‘ako, and Mo‘ili‘ili. The results reveal that one quarter of the study area currently has a narrow vadose zone of less than 1 meter, and sea level-rise of 1 meter could produce flooding over 20 percent of the study area. These results were achieved through the combination of hydrologic modeling, terrain modeling, and GIS layer data visualization. Flood maps will be extended to various local agencies for use in determining where and in what time-frame breaching of infrastructure is likely to ensue.
Ultimately, hazards related to SLR will become part of the operational cost of urbanized areas. Honolulu and surrounding areas are arguably the most economically valuable business locations in Hawai‘i. Drainage problems due to GWI are already problematic at the convergence of high tide and rainfall events, but with continued SLR, chronic drainage problems due to GWI will plague this network of commerce, threatening the exchange of tens to hundreds of millions of dollars annually.
Tatiana Oje was born in Kāne‘ohe on the windward side of O‘ahu. Her family moved from O‘ahu to Kaua‘i, then to Tulsa, Oklahoma, and then to the state of Washington. Tatiana returned to O‘ahu a few years after she graduated from high school, and since moving back to O‘ahu she has been working on her bachelor’s degree in engineering. She attributes the contrast between the places she has lived to her interest in how urban communities fit into the ecosystem. It was this interest that guided Tatiana to study civil and environmental engineering and to apply for the University of Hawai‘i Sea Grant College Program (Hawai‘i Sea Grant) Peter J. Rappa Sustainable Coastal Development Fellowship.
It was in college that she realized she wanted to be an engineer. While volunteering at Kapi‘olani Community College’s native plants garden, she was approached by the volunteer coordinator and offered a position on a research project. The goal of the project was to design a mounting system for meteorological instruments on campus. Tatiana wanted the mounting system to reflect the project’s integration of Science, Technology, Engineering, and Math (STEM) and Hawaiian culture. She did this by carving the Hawaiian moon calendar into the wooden post that the sensor would be installed on. The moon calendar carving represents the connection between contemporary climate monitoring and how Hawaiians kept track of the seasons. Once the instruments were up, Tatiana combined their data with Hawaiian mo‘olelo (story, legend) to study how topography and land cover affects wind behavior.
After transferring from Kapi‘olani Community College (KCC) to the University of Hawai‘i at Mānoa, Tatiana joined Dr. Oceana Francis’s lab and focused on modeling waves off the coast of Kaho‘olawe, an island off the coast of Maui. In this project she had the opportunity to apply what she had learned about the atmosphere from her research at KCC, this time researching how the wind interacts with the ocean. When the wind sweeps over the ocean it produces surface waves, and those waves travel thousands of miles across the open sea until they interact with the coast. The wind from storms produces huge swells that can have a devastating impact on Hawai‘i’s shoreline, and coastal communities throughout the Pacific are facing this and many other challenges due to the impacts of climate change.
During her fellowship with Hawai‘i Sea Grant, Tatiana worked with Matthew Gonser, Hawai‘i Sea Grant’s community planning and design extension agent, to research green infrastructure for stormwater management. Her research took her around the Hawaiian islands to Kaua‘i, Maui, and O‘ahu. On O‘ahu she discovered that much of the nonpoint source pollution is a result of urban runoff. Her trips to the windward side of O‘ahu were especially impactful as she had the opportunity to see the places where she grew up from a different perspective.
Throughout her fellowship it became clear that there is no one-size-fits-all solution, and that addressing nonpoint source pollution requires integrated rather than discrete solutions. This project exposed her to the issue of nonpoint source pollution and the possible approaches to resolving this threat to water quality. It illuminated the need for smart and integrated approaches to stormwater infrastructure planning, and further fueled Tatiana’s interested in coastal planning as a career. Creativity and community are two long standing interests of hers, and in this fellowship Tatiana had the opportunity to weave these passions into science and engineering. She hopes to take what she has learned from this fellowship and apply it in future studies and work.