Mid-Atlantic Migratory Corridor and Wind Farm Construction

Daniel Salisbury, October 1, 2018

September comes every year with a sense of excitement. Students go back to school, football players take to the field, and there is a promise of cooler temperatures to offer some relief from the dog days of summer. For me, this September offers another level of excitement, as I find myself at the end of a three-year project to study the migratory patterns of several baleen whale species off the coast of Virginia. Rarely do I get a chance to step back from the day-to-day workflow and look at the big picture, but as I reflect back on this project, it is remarkable to think of the countless hours that were dedicated to collecting and analyzing this dataset. Successfully bringing together field technicians, software developers, research analysts, data archivists, audio engineers and program managers is truly a shining example of how the Bioacoustics Research Program operates as a team-oriented organization. So, as I enjoy my pumpkin spice latte on this cold and rainy September day, I’d like to share with you a bit about what we can learn when we listen to the same spot in the ocean for years at a time.

Map of the study area with recorders positioned across the continental shelf and in the wind energy lease blocks.

Mid-Atlantic Migratory Corridor and Wind Farm Construction

Within the last five years, there has been interest in developing off-shore wind energy from multiple states in the mid-Atlantic. Virginia was one of the first states to auction off lease blocks to energy companies and, as a result, we started to deploy our marine recorders in the area to collect baseline data. This two-year effort led to being awarded a contract for a three-year study on how baleen whales use the area around the potential off-shore wind farm. While a large amount of research has been conducted on whales in their northern feeding grounds in Cape Cod Bay and the Gulf of Maine, and in southern calving grounds off the coast of Georgia and Florida, not as much research has focused on the mid-Atlantic. We know many whales partake in a migration down south to calve, but it’s not clear how much of the population migrates each year, or where they go if they don’t migrate south. Recent research suggests that whales travel throughout the mid-Atlantic more often than suspected. Our goals for the project were to better understand baleen whale spatial and temporal trends in the mid-Atlantic corridor off the coast of Virginia and to document the ambient noise levels in the area in order to inform the wind farm development process as they work to mitigate the risks posed to marine mammals from their construction and operation activities.

Presence of four baleen whale species over 5 years of recordings. Sea surface temperature is overlaid to show potential correlations with seasonal presence trends of each species. The ocean has so many variables and is such a rapidly changing environment, that the value in having five years of acoustic data to explore potential patterns cannot be overstated.
Acoustically located North Atlantic right whales within the wind energy area recording array.

One of the biggest questions we have is: when are different species of whales present? Do they have distinct seasonal trends or are they present year-round? How long do they stay in the area? Do these patterns vary drastically from year to year? To answer some of these questions, we comb through the audio data to identify whale vocalizations and create long-term presence plots like the one below.

When whales are present in the area, we want to know if they have particular areas that they spend more or less time in. Is their distribution uniform and how does it relate to the wind farm placement? Using an array of recorders, we can locate individual whale vocalizations and map them over the study area.

Finally, we can measure how loud the background noise levels are throughout the recording period. Noise pollution from human activities is an increasing threat to marine mammals as the ocean becomes louder and louder. I highly recommend watching the film Sonic Sea (https://www.sonicsea.org/) to learn more about this interesting and critically important topic.

While we can use this data to help wind energy developers minimize risks to whales, these results are a sample of some of the ways we go about answering questions we have about how whales use this habitat. Like most research, we create more questions than answers. The ocean is a vast and complex environment and trying to understand the variability in temperature, currents, prey availability, nutrients, ocean chemistry, and noise their role in driving marine mammal patterns of behavior across thousands of miles is a daunting but very exciting task. Thanks for reading and I hope you all have a wonderful fall season.

Noise levels at one recording site over a one year period. Red shades are louder periods of time and blue shades represent quieter periods of time. For reference, 60 dB (dark blue) is about as loud as a normal conversation, whereas 120 db (red) is louder than a rock band performance. 100 dB (yellow) is as loud as riding a motorcycle.

Acknowledgements: A special thanks to our funding sponsor for this project, the Bureau of Ocean Energy Management (BOEM) and project manager Desray Reeb.