June 2025

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June 2025 | Oceanography

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of various sources and explored different approaches to quanti­

fying their effects. The detections of vessels (Figure 3) differed

significantly between stations. HAT and JAX, which were closer

to shipping lanes, had higher daily counts than the other loca­

tions. Detections at HAT were reduced in the second year due to

masking by high overall sound levels.

The ADEON data were employed to develop a soundscape

code (Wilford et  al., 2021), which was subsequently used to

explore the differences between ADEON sites with (SAV) and

without (BLE, WIL) live hard bottom deep-water coral and a

tropical coral reef. The tropical coral reef was unique to the

deep-water sites; however, the two deep-water coral reefs (one

from ADEON and one from ADEON’s sister NOPP project,

DeepSearch) were also different from the sites without live hard

bottom, indicating that soundscape metrics can distinguish

these deep-water habitats (Wilford et al., 2023).

The 2019 and 2020 ADEON data were studied to determine

if there were differences in the soundscape associated with the

global COVID shutdown in March 2020. Changes in sound lev­

els that were detected in this offshore region did not align with

the shutdown period (Miksis-Olds et al., 2022).

Kowarski et al. (2022) examined the presence of cetaceans in

the ADEON area. A total of eight odontocete and six mysticete

cetacean species/groups were identified in the ADEON data.

There was higher species diversity during winter months than

summer months, suggesting that species were moving north in

the summer and south in the winter. Dolphins were the most

commonly detected species group, with presence at all stations

in all months. BLE and SAV were identified for the first time

as sites with regular presence of beaked whales that exhibited

species-​specific site fidelity. Blainsville’s beaked whales were

present in most months at BLE, while SAV

had either True’s or Gervais beaked whales

present in most months. North Atlantic

right whales were only confirmed on one

occasion, in January 2018 at HAT. For the

other mysticete species, ADEON con­

firmed results first reported in Davis et al.

(2020) that the distribution of blue and sei

whales is moving northward, and that sei,

blue, and fin whales are using the deeper

waters of the OCS more than previously

reported. Minke whales were highly vocal

at the southern and offshore ADEON sites

in the winter months, which confirmed

the proposal by Risch et  al. (2014) that

the OCS is an important mating ground

for minke whales. Kiehbadroudinezhad

et al. (2021) developed a new detector for

minke whales’ pulse trains and proposed

a new method for relative abundance esti­

mation to compare the presence of minke

whales in space and time using the ADEON data. Continued

acoustic ocean monitoring is important to document further

shifts and potential human-cetacean interactions in the future.

Active Acoustics

Pelagic zooplankton and fish distributions are spatially and tem­

porally patchy, requiring large amounts of data to fully cap­

ture their variability (Mackas et al., 1985). This makes estimat­

ing pelagic population abundances difficult, expensive, and time

consuming. Scientific echosounders historically deployed from

vessels are efficient for acquiring temporal and spatial data to

characterize the physical properties of the water columns that

pelagic organisms occupy (e.g., internal waves) (Benoit-Bird and

Lawson, 2016). Technological advances have resulted in auton­

omous systems that can be deployed on moorings or landers to

collect time series of longer duration than ship-based sampling,

though at a single location (Trevorrow, 2005). Multiple station­

ary systems spread across a region of interest can provide infor­

mation at broader spatial scales; however, the spacing of these

systems depends on the intrinsic biological and physical pro­

cesses present. The ADEON team objectives focused on biologi­

cal scatter in the water column, and it is hoped that the publicly

available data will inspire future research focused on the physi­

cal parameters linked to the backscatter signals.

The ADEON program incorporated both bottom-deployed

upward-looking and vessel-based downward-looking active

acoustic data collection and biological net tows (Figure 4a) to

provide information relevant to the placement of the stationary

AZFP sampling systems operating at 38, 125, 200, and 455 kHz.

Blair et al. (2021) describe FSASs measuring 38 kHz backscat­

ter from a vessel (Figure 4b) over an area of 100 km2 (Figure 4c)

FIGURE 3. Average number of vessel closest points of approach (CPAs) are

shown as detected at ADEON stations by month for the second and third

monitoring years.

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