Underwater Video Mapping of Benthic Habitats in Buzzards
Bay, Massachusetts Records the Pelagic Colonial Pyrosome
Tunicate Pyrosoma atlanticum
Kristin L. Osborne and William A. Hubbard
Northeastern Naturalist, Volume 25, Issue 3 (2018): N19–N23
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2018 Northeastern Naturalist Notes Vol. 25, No. 3
K.L. Osborne and W.A. Hubbard
Underwater Video Mapping of Benthic Habitats in Buzzards
Bay, Massachusetts Records the Pelagic Colonial Pyrosome
Tunicate Pyrosoma atlanticum
Kristin L. Osborne1 and William A. Hubbard1,*
Abstract - High-definition underwater-video mapping of Buzzards Bay, MA, photographed a pyrosome
tunicate. Positive identification to the species level was not possible because to do so requires a
live, undamaged specimen. However, the most probable species is Pyrosoma atlanticum, a common
species in temperate waters worldwide, which has not been docum ented in Buzzards Bay until now.
Introduction. Massachusetts Maritime Academy (MMA) had been conducting highdefinition
(HD) underwater video transects in Buzzards Bay under a grant from the
Massachusetts Environmental Trust. This funding has enabled MMA to conduct at-sea
mapping of Buzzards Bay substrates focusing on extensive seafloor areas covered with
Crepidula fornicata L. (Common Slipper Shell). In June 2016, a pyrosome was photographed
at the edge of one of one of these shell reefs (Fig. 1). Consultations with regional
experts have not identified any previous records of this colonial tunicate in bays or sounds
of New England.
The pyrosomes are an interactive group of small animals that form together as a holoplanktonic
colony, which filters water into their tube-like colony structure as it maintains 1
direction of movement and passively migrates at the mercy of currents. These organisms are
often found offshore in temperate waters, drifting in the pelagic zones.
Pyrosomes are members of the Tunicata (previously the Urochordata), a sub-phylum
within the phylum Chordata. Hallmark traits of this phylum include a post-anal tail,
1Massachusetts Maritime Academy, Buzzards Bay, MA 02532. *Corresponding author -
WHubbard@maritime.edu.
Manuscript Editor: Melisa Wong
Notes of the Northeastern Naturalist, Issue 25/3, 2018
Figure 1. A Pyrosome filmed with the Massachusetts Maritime Academy towed high-definition
video camera. (Photograph © Massachusetts Maritime Academy).
2018 Northeastern Naturalist Notes Vol. 25, No. 3
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K.L. Osborne and W.A. Hubbard
pharyngeal gill slits; a dorsal, hollow nerve cord; and a notochord. The tunicates are a
unique subphylum of the chordates because they revert to a more simplistic body plan by
the eventual loss of these features during their metamorphosis from the embryonic stages
to their adult forms (Lemaire et al. 2008). Interestingly, molecular analyses indicate that
the Tunicata are the closest invertebrate relatives of the sub-phylum Vertebrata (Delsuc
et al. 2006, Vienne and Pontarotti 2006). The class Thaliacea (within the Tunicata), is a
group of ~72 pelagic species (Govindarajan et al. 2011). The pyrosomes are classified
within the order Pyrosomatida. In this paper, we describe the first known record of a pyrosome
in New England.
Field-site description. Buzzards Bay is a 650-km2 temperate estuary characterized by
semi-diurnal tides and broad seasonal climate and water-temperature variations. Substrates
are diverse, ranging from boulder and rock to sand and silt/clay. Water temperatures vary
from 22 °C in summer to 1 °C in winter (BBCCMP 2013). In 2012 and 2013, maximum
annual temperatures of 25.57 °C in August 2012 and 26.11 °C in July 2013 were recorded
0.5 m off the bottom at a station 6.5-km east of where the pyrosome was discovered (CAF
East) (Hubbard 2016).
Methods. The MMA 30-foot RV Liberty used a SIMRAD® NSS-2 navigation-chart
plotter to conduct benthic mapping transects from 2016 through 2017. High-definition
underwater video transects were recorded as part of the Common Slipper Shell reef (hereafter,
C-reef) mapping on a Seaviewer® underwater video-camera system. The unit paired
a Seadrop 5500 HD camera with a surface-recording unit. The Seadrop 5550 camera was
installed in a vertical tow tube with laser pointers for a 10-cm scale in all recorded video
(Fig. 2). The surface-recording display system was programmed to continuously overlay
latitude, longitude, date, time (UTC), and course over ground (COG) on all video. This
overlay on high-definition video was accomplished by running the video signal through a
Videologic® PROTEUS II unit. The images were captured on a HDMI H.264 recorder while
simultaneously being displayed on the recording console and research-vessel navigationchart
plotter.
Commercially available software (PowerDirector14®) was used for post-processing
which allowed the capture of still images (with location and time data overlaid). Thousands
of C-reef images were analyzed and classified by ecological function according to the national
Coastal and Marine Ecological Classification System (CMECS 2010). This review
of individual video frames captured for classification allowed the team to identify the pyrosome
on the edge of a C-reef adhered to the sandy/shell substrate at an 8-m depth in upper
Buzzards Bay, MA (Fig. 3).
Results and discussion. We identified the organism photographed in Figure 1
(video clip is avaialable at https://youtu.be/0U-LSDyCaaA) as a member of the family
Pyrosomatidae, according to the taxonomic descriptions of Kott (2005) and upon consultation
with pelagic tunicate experts (e.g., M. Corrales-Ugalde, University of Oregon,
Eugene, OR; pers. comm.). The Pyrosomatidae is the only family within the order Pyrosomatida
and contains 8 species (van Soest 1981). In 1981, van Soest discussed a benthic
pyrosome species identified as Pyrosoma benthica (Monniot and Monniot 1966)—an
organism at the mercy of currents, with motion in only 1 direction. Logically, a pelagic
colony caught on the substrate would be exposed to benthic predators and therefore could
not survive. The most common pelagic North Atlantic species is Pyrosoma atlanticum
Péron. The specimen depicted in Figure 1 was found in shallow waters adjacent to the
open-ocean native range of P. atlanticum.
P. atlanticum colonies can range in color from clear to a translucent white, grey, pink,
or blue-green (Palma and Apablaza 2004). Colonies can reach up to 60 cm in length, with
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2018 Northeastern Naturalist Notes Vol. 25, No. 3
K.L. Osborne and W.A. Hubbard
Figure 2. Massachusetts Maritime
Academy 2016 underwater
video high-definition
camera system.
Figure 3. Pyrosome located just west of Stony Point Dike along Hog Island Channel—the
entrance to Cape Cod Canal. Base chart provided by NOAA office of Coast Survey; nauticalcharts.
noaa.gov.
2018 Northeastern Naturalist Notes Vol. 25, No. 3
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K.L. Osborne and W.A. Hubbard
individual blastozooids measuring ~8–9 mm each (Palma and Apablaza 2004). The specimen
captured in this dataset presents characteristics (e.g., outside colonial-wall morphology)
consistent with P. atlanticum. With a live specimen, siphon orientation, bud-growth direction,
and zooid-row formation could also be used to provide additional taxonomic support
for identification (Esnal 1996, Kott 2005), but the size, color, geographic location, and expert
consultations support the high likelihood of this being a P. atlanticum colony.
Identification to the species level is impossible with only a video and frame capture;
it requires a live, undamaged specimen. The 10-cm laser-pointer scale in the video output
allowed us to estimate the size of this colony as 8 x 40 cm. Various post-processing and
photographic magnifications showed some details, but not enough structural components to
positively identify the species. Further, it is important to note that although it is likely that
this organism is P. atlanticum, additional surveys and collection are needed to substantiate
the observations of the present study. We communicated our putative discovery via email
to both the Benthic and Pelagic Working Groups of the Northeast Regional Association of
Coastal and Ocean Observing Systems (NERACOOS) and other academic, governmental,
and private organizations. None of these organizations had previously documented a pyrosome
in New England.
P. atlanticum is a temperate, cosmopolitan, pelagic species. In this case, the pyrosome
was likely pushed downward by currents and thus adhered to the ocean floor despite not
being a benthic species. It is plausible that there are other pyrosomes in New England bays,
and the high-definition technology being deployed by research teams such as those operating
at Massachusetts Maritime Academy is just now allowing for their discovery. This
specimen may have been swept into Buzzards Bay from a warm core breaking off the North
Atlantic Gulf Stream current; as our oceans warm, we may expect to observe more exotic
visitors such as this colonial pelagic tunicate.
Acknowledgments. The Massachusetts Environmental Trust has financially supported this effort.
Literature Cited
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