Geo SubSea Part 4: Protected Species Monitoring and Mitigation for Offshore Marine Activities

Contributed by:

Jeff Gardner – President, Marine Geologist & Oceanographer

Megan McManus– Senior Environmental Project Manager

Geo SubSea Part 1: Who We Are & What We Do
Geo SubSea Part 2: U.S. History of Offshore Wind & the Park City Wind Project
Geo SubSea Part 3: The Aunt Polly at Gillette Castle State Park

View Geo SubSea’s website here.

Protected Species Monitoring and Mitigation for Offshore Marine Activities

There are a number of activities that man performs in the ocean that create noise in the water column. Some of this noise is potentially harmful to whales, dolphins, sea turtles, seals, and manta rays, collectively referred to as protected species. The monitoring and mitigation of human noise and its impact is governed by the Marine Mammal Protection Act and overseen by the National Marine Fisheries Service (NMFS).

The following sections provide a general overview of these efforts to help prevent harassment or injury to marine animals during activities associated with offshore wind development.

Background on Protected Species Hearing

Marine protected species use sound for communication, social interactions, foraging, mating, predator avoidance, and navigation.  Due to this, marine protected species are heavily dependent upon sound and their auditory capabilities for many critical behaviors.

Marine mammal vocalizations are most often discussed based in terms of vocalization frequency (measured in Hertz) and amplitude (measured in decibels). Frequency indicates the pitch of a sound while amplitude indicates the loudness of a sound. Experts believe lower frequency sound is the most harmful to the animals, specifically less than 180 kHz. If animals come too close to some of these sound sources, it could cause changes in their behavior or injury which the federal agencies have termed as a form of harassment. Man-made noises of the same frequency as a protect species vocalization will also create a masking effect, hindering their ability to perform the previously mentioned key aspects. Exposure to loud noises can also contributes to temporary or permanent hearing loss. Since protected species are extremely acoustically dependent, masking or hearing loss can be extremely detrimental to their survival.

Underwater acoustics research and general protected species behavior research are ongoing in order to more fully understand the nuances of how sound in the water affects these species.  However, most scientists and regulators agree that the implementation of preventative measures can be nothing but beneficial.

Figure 2. dolphin-audio-spectrogram

Offshore Survey Activities

Offshore surveying is a broadly used term that covers various activities that generally involve using sound sources in the water column to map the ocean floor and layers below the seafloor. The sound source, frequency, and amplitude depend on the objective of the survey.

Because specified survey equipment overlaps with protected species vocalizations, Protected Species Observers (PSOs) and Passive Acoustic Monitoring (PAM) Operators are utilized to ensure that no harm comes to protected species throughout the survey. PSOs stand watch, looking out over the water day and night during a survey to request vessel maneuvers to avoid potential vessel strikes (vessel strike avoidance) and equipment shutdowns to avoid potential noise exposure when protected species are observed within specific distances, known as exclusion zones.

PSOs utilize a wide variety of tools to help detected protected species during surveys. Binoculars and polarized sunglasses are the basic tools for a day on the water (Figure 1).  Surveys with operations during nighttime or during times of reduced visibility may also utilize PAM (Figure 2), night vision goggles, and thermal imaging cameras, often electing to use more than one technology in tandem.

Figure 1. Megan-scanning the water for protected species at sunrise

Other Forms of Mitigation and Monitoring 

PSOs can’t always be utilized offshore for a variety of reasons, so alternate forms of mitigation and monitoring are used to ensure the safety of protected species. Widespread speed restrictions are one of these measures that greatly reduces the chance of vessel strikes of protected species. Requested speed restrictions are broadcast over the VHF radio to marine traffic and posted on special agency websites. Aerial surveying is another alternative method of protected species monitoring. This allows an observer to view large portions of the ocean simultaneously, and over a short time-periods, aerial surveys are often used to develop species abundance counts and to monitor the need for reduced speed zones during critical times of the year when an abundance of species are in a particular region.

Results of Monitoring and Mitigation 

Through all the mitigation efforts summarized above, the offshore wind industry is doing an excellent job of keeping impacts to marine life negligible.

Unfortunately, the heavy commercial use of the world’s oceans as (1) the marine traffic highway and (2) for fishing, cause ship strikes and entanglements which are the two largest causes of protected species fatalities, particularly for the slow-moving animals. There is no better example of this than the North Atlantic Right Whale (Top of Blog, WILDESTANIMAL 2017), which is the focus of much of our efforts here in the northeast. There are only an estimated 360 of these animals left on the planet, so there is a grave concern for their continued existence as a species.


Geo SubSea has protected species experts on staff that help supervise and manage these monitoring and mitigation efforts and provide quality control for the submission of data and reports to federal agencies. These scientific data and observations are very important to inform NMFS and all stakeholders of the estimated species populations and trends to determine if our mitigation and conservation efforts are having any success.

As you can imagine at a company staffed by marine and environmental scientists, we are driven to help these animals because we share the same planet, and research has shown the amazing intelligence they possess, and symbiosis that exists among all creatures that is critical for maintaining nature’s balance and keeping the earth healthy overall. Our company is very proud to be a part of this effort.

Think globally, act locally.

Stay safe and healthy until the next Geo SubSea post,

Megan and Jeff

For more information related to protected species monitoring click on links below:
Right Whale Sighting Advisory System
Marine Traffic Global Monitoring System

Recommended Posts
Contact Us

We're not around right now. But you can send us an email and we'll get back to you, asap.

Not readable? Change text. captcha txt

Start typing and press Enter to search