Personal Profile
Dr. Shawn R. Noren
Biography
The ocean fascinated me ever since the early age of 5. In order to satisfy my desire to learn about the marine environment, I passed my time as a child watching the Undersea World of Jacques Cousteau, reading Ranger Rick Magazine, and writing poems about human-marine mammal conflict (i.e., harp seal clubbing, manatee boat strikes, and the dolphin-tuna fishery interaction). I did not actually see the ocean with my own eyes until I was 8 years old; the memories of this experience still burn bright with the sounds, smells and sight of the deep blue water body. It was then that my passion to study some aspect of the marine environment was solidified.
In seventh grade I had an amazing opportunity to participate in a 2-week summer program that included kayaking and camping along the Chesapeake Bay. Our days were filled with recording the flora and fauna of the Bay along transect lines to understand how species’ assemblages changed with increasing proximity to land and with increasing salinity levels, as we got closer to the mouth of the Bay. We witnessed first hand the devastation that 200 years of pollution had on the bay’s ecosystem. More than twenty years later clean-up efforts are still in progress.
Throughout high school I remained determined to major in marine biology in college. I focused on my studies because I could only attend college if I earned a full-scholarship because my parents could not afford to send me to college. I graduated valedictorian and earned full-scholarships to the University of Maryland, College Park (UMCP) where I enrolled in the biology program. UMCP did not offer a marine biology program, but I was able to take elective biology courses such as marine ecology, biological oceanography, Chesapeake Bay laboratory, and a shark class (with the world-renowned professor, Dr. Eugene Clark). My mentor, Dr. Bill Higgins, encouraged me that the most important thing to do as an undergraduate was to get a well-rounded biology background (chemistry, physics, biology, and math) and to start an independent research project; this would provide the necessary skills that I would need if I wanted to study marine biology in graduate school. He was right,and this is what I tell my COSMOS high school students.
In graduate school I had the opportunity to work with Dr. Terrie Williams, a renowned scientist at the University of California, Santa Cruz. Dr. Williams studies the comparative physiology of aquatic mammals. Under her mentorship I developed my own research interests. Growing up as a swimmer and water polo player, I was well aware of the inadequacies that humans have holding their breath, staying warm, and locomoting in an aqueous environment. Therefore, the adaptations that marine mammals have acquired over evolutionary time to meet these demands fascinated me. These thoughts launched the direction of my career.
Research Interests
My research endeavors have primarily focused on the whole animal level with emphasis on the respiratory, cardiovascular, and musculature systems in an effort to understand the effects of body size and ontogeny on physiological performance. Because of the large variation in body size, extreme conditions at birth, and cosmopolitan distribution throughout various environmental regimes, marine mammals are an ideal system to study these questions. My investigations have included biochemical, physiological, morphological, behavioral, and kinematic studies, which have enabled me to master many laboratory and field techniques including, biochemical analyses, motion analyses software, veterinary procedures, tritiated water, radio telemetry, oxygen analyzers, and time-depth-recorders (to name a few). Ultimately, I aim to understand how marine mammals “make a living” in an “extreme environment”. In light of the changing marine ecosystem, it is critical to understand how pliable these groups are so that we may predict how perturbations to the environment may impact these populations.
In comparison to terrestrial mammals, little is known about the physiology of marine mammals. The majority of my graduate research was geared towards studying the diving and thermoregulatory physiology of marine mammals. For example, for my master’s degree I analyzed the muscle biochemistry of eleven species of cetacean to assess diving capacity. This research determined that inter-specific differences in body size and locomotor muscle biochemistry influence inter-specific variability in diving performance (Noren and Williams 2000; Noren 2005). To further understand the effect of body size on diving capacity, changes in blood gas, pH, and lactate were measured during diving for three species of odontocetes, representing a wide range in body size (Pacific white-sided dolphins, killer whale, and bottlenose dolphin). Results showed that larger species have slower blood oxygen depletion rates, which in turn afforded comparatively longer aerobically supported dive durations. However, smaller-bodied species may rely on enhanced oxygen stores as an adaptation for prolonging dive duration (Noren et al. in revision).
My most recent focus has been on postnatal development, because little is known about the physiology of immature marine mammals and this segment of the population is the most vulnerable to environmental perturbations. My dissertation research focused on the development of diving capacity in dolphins. As a side project, I also studied the development of thermoregulation in dolphins. The accessibility of bottlenose dolphins in the field and captivity facilitated these studies. In order to understand the diving and thermal limits of immature dolphins, morphological, biochemical, physiological, and behavioral studies were conducted. This research determined that in addition to physiological limitations associated with small body size, immature dolphins require postpartum development to acquire traits for diving, such as enhanced muscle (Noren et al. 2001) and blood (Noren et al. 2002) oxygen stores, enhanced muscle acid buffering capacity (Noren 2005), reduced heart rate at depth (Noren et al. 2004), and prolonged breath-hold capacity (Noren in prep). Furthermore, small body size and limitations in blubber deposition put immature cetaceans at a thermal disadvantage (Noren in prep, Noren et al. in prep.).
During my postdoctoral tenure at Smithsonian’s National Zoological Park I was interested in understanding how body condition at weaning and postpartum physiological development may interact to affect gray seal pup survivorship to age one. I measured body condition at weaning, post-weaning fast duration, movement patterns during the fast, and the development of body oxygen stores during the fast in wild gray seals at a remote field site during winter (Sable Island, Nova Scotia, Canada). Body condition at weaning correlated to the duration of the post-weaning fast (Noren et al. submitted) and postpartum development of the oxygen stores occurred throughout the fasting period (Noren et al. 2005). Consequently, lean pups, which prematurely terminated their fast to conserve lipid reserves, disembarked for their first foraging trips with relatively underdeveloped diving physiology compared to fat pups, which were able extend their terrestrial developmental period. Because successful foraging at depth requires long breath-holds supported by enhanced oxygen stores, these relationships may, in part, explain the competitive advantage granted to better-conditioned pups.
Currently, I am contracted by Southwest Fisheries Science Center (part of NOAA’s National Marine Fisheries Service) to assess a potential impact of tuna purse-seine fisheries on dolphin populations in the Eastern Tropical Pacific (ETP). Tuna purse-seine fisheries in the ETP capture schools of large yellowfin tuna (Thunnus albacares) by chasing and encircling pods of associated dolphins. Fishery-related dolphin chase can last for several hours with speeds approaching 1.3-1.9 times normal adult dolphin cruising speeds. Underdeveloped musculature makes dolphin calves susceptible to separation during tuna purse-seine fishery chase and their prolonged maternal dependence increases their risk of mortality once they are permanently separated (Noren and Edwards in press). My investigations of the swimming kinematics of mother-calf dolphin pairs provided the first empirical evidence that echelon swimming (calf swims alongside mother’s dorsal fin to gain a hydrodynamic boost) enables neonates to travel at group speed with a decreased tailbeat frequency and stroke amplitude; however, once echelon position is disrupted, independently swimming 0-1 month-old calves are unable to maintain adult speeds (Noren et al. submitted). The ontogeny of locomotor performance and efficiency of independently swimming dolphin calves from 0-2 years postpartum is currently being investigated (Noren et al. submitted.). These findings, in combination with other studies, are being used to assess whether tuna from Mexican fisheries, which utilize the dolphin chase method, can be labeled ‘dolphin safe’. Currently tuna are not imported from these fisheries, but if granted the ‘dolphin safe’ label tuna from these fisheries can be imported and sold in the United States. This potential change to US policy was highlighted in Nature, Vol. 427, page 575.
I am also a research associate at the Institute of Marine Science at the University of California, Santa Cruz. During my upcoming Antarctic expedition I aim to explore the ontogeny of thermoregulation in the Weddell seal, an animal that experiences extreme thermoregulatory challenges at birth. Morphological measurements and muscle, skin, and core body temperatures be taken from several age classes to investigate key characteristics that establish an animal’s thermal tolerance, such as surface area to volume ratio, ability for muscle thermogenesis, blubber conductivity, and total body conductivity.
Shawn_noren's Recent Blog Entries
Final thoughts from Dr. Shawn
Posted By Shawn_Noren, Dr. Kanatous on Mon Dec 18 18:07:10 2006
Hello Polar Scientists
We finished the season and spent the last few days cleaning and returning field gear and lab equipment. We had a few “hiccups” on the day we were supposed to fly out; the type of plane, time we were to depart, and runway that we were to use changed on us about four times. It felt like the rug was jerked out from under our feet each time they changed the itinerary because we were so close to leaving and getting closer to seeing our loved ones.
Although I.....
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Week 8 Report from the Ice Team
Posted By Shawn_Noren, Dr. Kanatous on Sun Nov 26 17:38:29 2006
Hi everyone,
Our report this week gives you an introduction to sonography.
So far we have shared with you details about our fieldwork in Antarctica and we have talked a little bit about some of the laboratory analyses. Fieldwork here is slowing down as we preparing to leave Antarctica on December 1st. Thus with this update, Week 8 Report from the Ice Team, we want to educate you on ultrasound, which is a vital methodology used for a.....
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Week 6 Challenge Questions from the Ice Team
Posted By Shawn_Noren, Dr. Kanatous on Sun Nov 12 18:04:36 2006
Read our Week 6 report in the Expedition News focus area or from this link.
Question #10
Looking at the temperature graph in the Week 6 update answer the following question: Why are the seals’ skin temperatures intermediate to that of their core body temperatures and the air temperature. Think about how the animal does this physiologically and why this is.....
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Answer to last week's Challenge Question from the Ice Team
Posted By Shawn_Noren, Dr. Kanatous on Sun Nov 12 17:51:15 2006
Answer to Last Week's Challenge Question (#9 from the Ice Team)
One of the reasons scientists work with Weddell seals is because they are extremely docile and gentle by nature. In contrast, many species of seals that live in the Arctic Circle are skittish and difficult to approach. Why do you think that Weddell seals are not aggressive toward humans? (Hint: it is related to predator-prey relationships.)
Weddell seals are not aggressive.....
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Week 6 Report from the Ice Team
Posted By Shawn_Noren, Dr. Kanatous on Sun Nov 12 17:31:50 2006
Hi everyone,
This past week has been another very busy and successful week for the Ice Team.
Read our full report in the Expedition News focus area.
Dr. Shawn
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To Homelearners
Posted By Shawn_Noren, Dr. Kanatous on Mon Oct 16 22:14:11 2006
How do the seals make their holes...do they dig them with their claws only or do they bite the ice too?
Seals can not make their own holes. They can make an already existing hole larger by reaming. Reaming is when they use their teeth in a back and forward motion to shave the ice off. The holes are actually from natural cracks within the sea ice. Cracks can appear in the ice through several mechanisms. A few examples of how cracks can occur are: 1) Tidal cracks occur from the movement.....
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To Boundary Street P.S.
Posted By Shawn_Noren, Dr. Kanatous on Mon Oct 16 22:01:15 2006
1. Any seal hunters come to where you are and what
happens if they do ?
There are no seal hunters in Antarctica. Different nations possess territoralities in Antarctica and under that jurisdiction, the seals and the other animals of Antarctica are protected from poaching or other disturbances.
2. Where do the seals go when it is a bad storm?
The seals do not appear to change their behavior when faced by storms. They can still be found resting on the ice.
Quick Challenge Question:
Why.....
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a"What is the "ice team"?"
Posted By Shawn_Noren, Dr. Kanatous on Fri Oct 6 22:17:09 2006
This is an answer to the question from Big Bad Wolves, "What is the "ice team"?"
The ice team is the group of scientists in Antarctica that will be capturing the Weddell seals to collect morphological measurements (girth, length, mass, blubber thickness) and muscle samples (for protein and RNA analyses). In addition to spending long days in the field we will also be doing lab work down at McMurdo. The scientists on "The Ice" include Dr. Shane Kanatous, Dr. Steve Trumball, Dr. Shawn Noren,.....
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I'm Excited!
Posted By Shawn_Noren, Dr. Kanatous on Tue Sep 26 09:48:09 2006
I wanted to say "hi" to everyone personally before I depart on Saturday. I am busy in Colorado getting to know the rest of the team and learning how to use the new equipment that we bought for this project. We are going to be using an ultrasound, something that doctors and veterinarians use on people and animals, respectivly. We will be using the ultrasound to look at how the blubber layer develops as the seal pup grows after birth so that the seal can handle the very cold extreme weather of.....
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