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.