COMIDA: What determines spatial distribution of epibenthic communities in the Chukchi Sea?
Brenda Konar (University of Alaska Fairbanks), Jackie Grebmeier (University of Maryland), Ken Dunton (University of Texas), Martin Schuster and Alexandra Ravelo (University of Alaska Fairbanks),
Results:
COMIDA is the Chukchi Offshore Monitoring In Development Area project. The overall
goal of COMIDA is to initiate sampling to monitor anthropogenic chemicals associated
with offshore oil and gas exploration and development and to monitor benthic biota in the
area of potential or actual offshore drilling areas in the Chukchi Sea.
Objectives of the Epibenthic Component:
Forty-four genera (or higher) were sorted, identified, counted, and weighed for analyses of community structure. In general, the MDS ordinations illustrate that there are five
community types, based on abundance and biomass (Figs. 2 and 3). While the study area was fairly homogeneous as far as abundance, some stations were outliers (stations
14, 4, 46, and 109, Figs. 1 and 2). Many of the dominant organisms structuring these communities (Echinarachnius and ophiuroids, Fig 2a and b) were patchily distributed,
while others (Chionoecetes and shrimp, Fig. 2c and d) were more evenly distributed. Other organisms that were dominant in structuring the community included hermit crabs,
and the gastropods, Neptunia and Cryptonatica. Approximately 96% of the community structure for abundance was described by these seven groups (BEST Routine within
Primer-E).
1) Produce a detailed community description for monitoring purposes.
2) Identify the potential physical drivers that are structuring the community.
3) Initiate monitoring to distinguish changes in benthic biota due to oil and gas activities
from those due to changes in climate.
2D Stress: 0.12
Transform: Square root
Resemblance: S17 Bray Curtis similarity
Transform: Square root
Resemblance: S17 Bray Curtis similarity
Transform: Square root
Resemblance: S17 Bray Curtis similarity
2D Stress: 0.12
Echinarachnius
2E3
2
1) Are epibenthic communities distributed in patches?
-Are all species evenly distributed throughout the study area?
2) Which species are most important in determining community structure
as far as abundance and biomass?
3) Which physical drivers are structuring the community?
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Fig 2a. MDS based on invertebrate abundance.
Bubbles correspond to Echinarachnius abundance.
Green circles represent 40% similarity among sites.
107
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1.4E4
1010
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240
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109
4.9E4
1330
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1010
7E4
Fig 2b. MDS based on invertebrate abundance.
Bubbles correspond to ophiuroid abundance. Green
circles represent 40% similarity among sites.
shrimp
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2.8E4
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109
2D Stress: 0.12
14
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46
Transform: Square root
Resemblance: S17 Bray Curtis similarity
Chionoecetes
14
7E3
8E3
Questions:
2D Stress: 0.12
ophiuroid
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43 20
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Fig 2c. MDS based on invertebrate abundance.
Bubbles correspond to Chionoecetes abundance.
Green circles represent 40% similarity among sites.
2.1E3
1330
32
26
2915
1010
3E3
Fig 2d. MDS based on invertebrate abundance.
Bubbles correspond to shrimp abundance. Green
circles represent 40% similarity among sites.
MDS ordinations based on biomass show a similar grouping of sites as in the abundance MDS with the same outlying stations (Fig. 3). Similar organisms also dominate the overall
structure of the community with some organisms being patchily distributed (Echinarachnius and ophiuroids) and others (Chionoecetes and shrimp) being more evenly distributed.
Other organisms that were dominant in structuring the community included the cucumbers, Psolus and Ocnus, hermit crabs, the basket star, Gorgonocephalus, the gastropod,
Neptunia, and the crab, Hyas. Approximately 96% of the community structure for abundance was described by these nine groups (BEST Routine within Primer-E).
Marisa Guarinello
Transform: Square root
Resemblance: S17 Bray Curtis si milarity
T ransform: Square root
Resemblance: S17 Bray Curtis similarity
2D Stress: 0.15
2D Stress: 0.15
Echinorachnius
1
● Sampling was completed during two cruises (summers 2009
and 2010)
● 1 beam trawl was deployed at each of 53 stations within the
COMIDA study area (Fig. 1)
Each trawl was (or adjusted to ) 2.5 minutes at 1.5 knots
Depths ranged from 27 to 56m (mean of 44.4 ± 0.8m)
● Trawls were sorted on deck
Epibenthic organisms were identified, counted & weighed
● Physical data collected with SONDE & VanVeen grab:
Bottom water temperature, salinity, pH, chlorophyll,
sediment chlorophyll a, TOC, TON, C/N, various measures of
grain size and DO, and water depth
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Beam Trawl
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Fig 3b. MDS based on invertebrate biomass.
Bubbles correspond to ophiuroid abundance. Green
circles represent 40% similarity among sites.
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103
103
1010
46
Fig 3a. MDS based on invertebrate biomass.
Bubbles correspond to Echinarachnius abundance.
Green circles represent 40% similarity among sites.
Fig 3c. MDS based on invertebrate biomass.
Bubbles correspond to Chionoecetes abundance.
Green circles represent 40% similarity among sites.
Fig 3d. MDS based on invertebrate biomass.
Bubbles correspond to shrimp abundance. Green
circles represent 40% similarity among sites.
Stations with similar dominant organisms generally did not appear to spatially group together (Fig. 4). MDS ordinations show that sites that are spatially grouped may or may not
have the same abundances of the dominant organisms, as can be seen for the ophiuroids and Chionoecetes. Several physical parameters were tested to determine which
parameter might be structuring the biological community using the BEST BIO-ENV routine within Primer-E. It was found that for abundance, 32% of the variability was
accounted for by depth, a grain size measurement (the percent of 2 phi in the sample), % total organic nitrogen (TON), and temperature. For biomass, 42% of the variability was
accounted for by depth, two grain size measurements (the percent of 2 and 4 phi in the sample), % TON, and temperature. It should be noted that TON and total organic carbon
were correlated so only TON was used in the BIO-ENV analysis.
Resemblance: D1 Euclidean distance
2D Stress: 0
Resemblance: D1 Euclidean distance
ophiuroid
2D Stress: 0
7E3
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Fig 4a. MDS based on spatial location of stations.
Bubbles correspond to ophiuroid abundance.
Trawl contents from Station 32 showing
a dominance of ophuroids.
Chionoecetes
Summary:
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Figure 1. Map of COMIDA study area showing the trawling sites in each year.
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shrimp
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2D Stress: 0.15
Chionoecetes
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VanVeen Grab
2D Stress: 0.15
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Methods:
Transform: Square root
Resemblance: S17 Bray Curti s similarity
Transform: Square root
Resemblance: S17 Bray Curtis similarity
ophuroid
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Fig 4b. MDS based on spatial location of stations.
Bubbles correspond to Chionoecetes abundance.
Trawl contents from Station 18 showing a
dominance of Chionoecetes.
● The epibenthic organisms in the COMIDA study area are generally patchily
distributed but the same suite of organisms appear at many of the stations.
● There are 7 (for abundance) to 9 (for biomass) organisms that primarily
structure this community, including the economically important snow crab,
Chiocoecetes opilio.
● Stations that were located spatially close to one another did not necessarily
have similar community structure.
● The environmental variables controlling the distribution of organisms was not
conclusive, however it appears that water depth, grain size, total organic carbon,
total organic nitrogen, and temperature may be playing a role.
Acknowledgments: Special thanks to Dick Prentki of the Bureau of
Ocean Energy Management, Regulation and Enforcement, the captain
and crew of the RV Alpha Helix, Eric Hersh for providing Figure 1,
Brenda Norcross for supplying the beam trawl, and Susan Schonberg
and Nora Foster for taxonomic assistance. Additional pictures supplied
by Heloise Chenelot. This project is funded by the Bureau of Ocean
Energy Management