Grant Milne, PhD Candidate

Developing better ways to monitor marine habitats
UNH doctoral candidate Grant Milne collecting sediment samples

Grant Milne graduated from Thiel College in 2019 with a Bachelor of Science in conservation biology and a Bachelor of Arts in biology before joining COLSA's biological sciences: marine biology Ph.D. program. The Portville, New York native, who once had a gray seal chew on his fin while he was SCUBA diving, is driven in his work by his life-long love of water.

“Nearly all my hobbies have revolved around water from childhood into adulthood,” says Milne, “and I have a strong desire to give back to the aquatic ecosystems to which I attribute so many positive experiences in life.”

COLSA: How would you explain your research to a non-scientist?

Grant Milne: The object of my research is to use passive acoustic monitoring and genetic seawater sampling to identify sentinel indicators of environmental factors that impact both transmission loss and the ambient noise level, to predict the propagation environment that exists in various coastal habitats.

A sentinel indicator is a measurable variable that represents some process, system or key component of an ecosystem that is impacted by environmental pressures and that can be monitored over time. For example, forage fish species (especially Atlantic herring and river herring) serve as sentinel indicators of ecosystem health, as they play a key role in the trophic web, serving as a food source for large cetaceans as well as many other marine predators.

An example of a sentinel habitat is an eelgrass community, because eelgrass has a sensitivity to pollution that allows it to serve as an indicator of pollutants in seawater and can also serve as an indicator for fish populations as eelgrass is important for the protection of the juvenile forms of many commercially important fishes in the Gulf of Maine. Eelgrass is also sensitive to high levels of nitrogen, as heightened phytoplankton and macroalgae productivity in the presence of increased nitrogen levels can restrict eelgrass growth. These are just a couple of examples, but there are many more exist. 

The acoustic propagation environment is the physical environment within which a given sound propagates. It also refers to the environmental characteristics. like ambient noise level, that impact the detectability of a sound and the level of transmission loss the sound experiences as it passes through the environment.

COLSA: Why is your research important?

Grant: One of the major obstacles for research in marine habitats is reduced accessibility when compared to terrestrial research. Reduced light transmission in water means that visual observation is difficult, hands-on research requires special training in SCUBA and is time and depth limited, and many methods for surveying marine biota are disruptive or destructive such as trawl surveys, hooks or long lines, trapping and other methods that involve disturbance or removal of organisms in their natural habitat.

My research aims to provide a means for long-term, minimally invasive monitoring of marine habitats. As waters in the Gulf of Maine continue to warm at unprecedented rates, the ecosystems present undergo rapid change. The geographic ranges of warm water species are expected to expand, and native species will experience new biological and geophysical pressures, making techniques for monitoring temporal change in Gulf of Maine habitats essential for assessing the impact of these environmental shifts.

Furthermore, knowledge of coastal habitat distribution is valuable for industrial and military application, as knowledge of the acoustic environment is essential for the calibration of acoustic sensing equipment such as echosounders.

COLSA: What do you wish your colleagues/friends/family knew about your work?

Grant: Environmental DNA sampling and passive acoustic monitoring (PAM) are two exciting forms of data collection that allow scientists to answer all sorts of different research questions, and yet the average person outside of the field of genetics or acoustics has likely never heard of either of these interesting observational techniques, including me before beginning my current research project! For this reason, when trying to explain to family or friends what it is that I do, I often try to explain to them what eDNA sampling and PAM are, and what sorts of questions can be answered with these two techniques.

Environmental DNA sampling involves collecting free-floating genetic material from the environment without isolation of a target organism. In the context of my research, this involves collecting seawater, filtering it to concentrate the genetic material present in a sample, extracting the DNA from the filter, amplifying it using universal primers to target a broad array of organisms in a sample, and then sequencing the sample to determine which organisms’ genetic material are present in the sample. In this way, I am able to obtain a genetic “snapshot” of the species present in a given area at a given time, without actually having to capture any organisms.

Passive acoustic monitoring involves recording underwater sounds using a hydrophone and then analyzing the recordings to detect anthropogenic, biological, and geophysical sound sources, which collectively make up the underwater soundscape. These data can be used to answer a myriad of questions regarding the behavior of marine animals, habitat composition, the influence of anthropogenic noise, and many others.

COLSA: Have you learned/discovered anything during your research that’s surprised you? If so, what?

Grant: While I am still in the process of analyzing data from the first round of collection that took place over the summer, I encountered a surprising observation during my fieldwork. I collected data from three different habitat types in two different locations, for a total of six sites. My two research locations were located around 1.5 km apart. Despite the relative proximity of the locations, I was surprised to find that the eelgrass bed at one site began dying off rapidly through the month of August, yet the eelgrass meadow located at my other location was still going strong at the end of data collection on October 1st. I found it surprising to have such a strong contrast in timing between the two habitats despite such a small difference in spatial distribution.

COLSA: What do you consider your biggest challenge?

Grant: The biggest challenge that I have faced since starting my graduate research has been developing the skillset necessary to conduct acoustics research, given that my previous education was in conservation biology.

Prior to graduate school at UNH, I had zero experience with acoustics research and didn’t have the math and coding skills to conduct this type of research. As a result, I have been working hard to balance taking the necessary courses for acoustics research with dedicating enough time to my research project. This has proven difficult at times, but I feel that by taking on another field I am expanding the interdisciplinary nature of my research and will hopefully uncover some surprising and interesting new discoveries through the integration of the fields of genetics and acoustics.

COLSA: What drives you?

Grant: My passion for conducting research on aquatic ecosystems comes primarily from spending countless hours of my life in lakes, streams and rivers, which cultivated a deep internal appreciation for the water and the organisms that call the water their home. Nearly all my hobbies have revolved around water from childhood into adulthood, and I have a strong desire to give back to the aquatic ecosystems to which I attribute so many positive experiences in life. I hope to spend my career acting as a caretaker, protector and steward of these ecosystems so that future generations are able to have similar experiences in the water to those for which I am so grateful.

COLSA: What are you most proud of?

Grant: I am pursuing a career that allows me to contribute to the conservation of ecosystems. I have had an immense appreciation for the natural environment, and biology in particular, since I was a kid watching Steve Irwin and Jeff Corwin almost every day. This drive to give back to ecosystems through research has influenced the majority of my educational and career decisions, and now working toward a PhD in narine biology, it feels like I am closer than ever to achieving this goal. I am proud that I didn't give up on this dream, and I think that there is a sense of fulfillment that lies in conducting research that positively impacts the environment. 

COLSA: Why did you choose UNH?

Grant: A number of factors contributed to my decision to choose UNH. I have family in New Hampshire and spent a lot of time vacationing here when I was younger and really loved the area and the close proximity to the ocean. I visited UNH when I was looking at undergraduate schools, but I opted to attend a school that was a little more affordable and closer to home. However, I always kept UNH in mind, and when I was looking for graduate programs in aquatic research, UNH appeared to offer immense opportunity in this area.

COLSA: What do you plan to do with your degree?

Grant: I plan to use my degree to continue my research of aquatic ecosystems. While I am really enjoying my current research involving marine ecosystems, I hope to one day be able to conduct research on the freshwater ecosystems that have had such a strong positive impact on my personal growth. It is my dream to one-day give back to these ecosystems through my research. I am currently torn between the decision to pursue a career in academia or seek out a job in research through a government agency, but I am positive that in the future I would like to conduct research on freshwater ecosystems in the northeastern United States.

Learn More