Copyright
Peggy M Murray.

Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR) : results of a REMOTS survey, August 1992 online

. (page 2 of 3)
Online LibraryPeggy M MurrayRecolonization of the Mill-Quinnipiac River Disposal Mound (MQR) : results of a REMOTS survey, August 1992 → online text (page 2 of 3)
Font size
QR-code for this ebook


12



Successional Stage Distribution




Code Successional Stage

1 Azoic

2 Stage I

6 Stage III

7 Stage I on Stage ill
9 Indeterminate



4 5 6 7

Successional Stage Code




June 1991



August 1992



Figure 3-3. Frequency distribution of successional stages from the 1991 and 1992
REMOTS® surveys at MQR



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



13

The presence of Stage III organisms is a rough indicator of the species progression of
that area. Only 20% of the replicates in the June 1991 survey at MQR contained signs of
Stage III organisms. This number doubled in the August 1992 MQR survey (39%). Again,
reference values were considerably higher; in the 1991 CLIS survey, 84% of the reference
area replicates contained Stage III organisms.

3.2.2 Organism-Sediment Index

The apparent RPD, the successional status, and indicators of methane or low oxygen
(Section 3.3) are summarized in a value called the Organism-Sediment Index (OSI). OSIs
can range from -10 (no apparent macrofaunal life and methane gas present in the sediment)
to 11 (aerobic bottom with a deep apparent RPD, evidence of a mature macrofaunal
assemblage, and no apparent methane). The index is useful in mapping disturbance and
ecosystem recovery.

OSI values can vary widely even among three replicates at the same station. The
median OSI from three replicates is reported, therefore, to best represent the overall
conditions at that site. Since the index is a number, it also can be useful to track historical
changes at any site, if these numbers are compared with reference values.

Median OSI values from all stations of the 1992 MQR survey ranged from 3 to 7.
This range is lower than the range measured at the CLIS reference area in June, 1991 (5-9).
Again, the value of this indicator has improved since the 1991 survey, when the OSIs ranged
from -8 to 3 within 200 meters of the center of the MQR mound (Figure 3-4).

The distribution of OSIs displays no particular spatial pattern in either 1991 or 1992
(Figure 3-5). The southern part of the mound has higher OSI values, probably due to this
area being farthest from the MQR mound boundary. Since active disposal is no longer
taking place, a "footprint" of activity is no longer apparent.

3.3 General Observations

3.3.1 Methane

Methane was present in both the REMOTS® surveys of 1991 and 1992.
Approximately 10% of the stations from the 1992 survey contained evidence of methane,
while double the number of stations (approximately 20%) within 200 meters of the center of
the 1991 survey contained methane.

This persistence of methane, documented in several prior DAMOS reports (e.g.,
SAIC 1990a, 1990b), is the most conclusive piece of evidence presented by REMOTS® data
that the capping material at MQR is conducive to the formation of methane. The presence of

Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



14



MQR OSI Comparison



50



40



30



£ 20

<D

3
CT

"- 10



1



N =21

August

N =9

June



2.5 i 2 3 4 5 6 7 8 9 10 11

Median OSI



["31 June 1991 J§ August 1992



Figure 3-4. Frequency distribution of OSI values from the 1991 and 1992 REMOTS®
surveys at MQR



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



15



DC

a



CD

C/)


J3

CD
>

O



c

D



CO

Q



M.9'ES oZZ.












□ June 1991
A August 1992




M,8'£S oZL


IT)

V










in i t "> n co

D SI «*n<«

CO

M.O't'g oZL


•4 ^ "4 « 1

to r» cm |^ i co

^ <4 a ^ ^c5 □

< + <
^4«




M.z'fg oZZ.


r

°?

cn n ^S^


o
~~ I °

— to
DC

— (-
LU

— 5
'— ' o


■z.

CO

od

5


z
co

5





OS



00

H

O

w
2

tN

ON



oo
O



00



3
OX)



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



16

methane is indicative of organic loading of the sediments and is easily discemable in
REMOTS® photographs because of an irregular, generally circular shape and glassy texture.
If methane is detected, the OSI calculation is decreased by 2. Thus, OSI values for MQR
took into account this factor.

3.3.2 Low Dissolved Oxygen

REMOTS® photographs are flagged when a condition of apparent low or nonexistent
dissolved oxygen (DO) exists at the sediment surface. This classification is based on the
presence of reduced, low reflectance sediment at the sediment- water interface. If a sample is
flagged due to low DO, the OSI calculation is decreased by 4; obviously this classification
can greatly affect the final calculation of OSI.

None of the 1992 MQR stations were flagged as having low DO. Of the stations
within 200 meters of the June 1991 center station at MQR, 16% were flagged as having low
DO, while 2 replicates outside of this boundary (300E and 300W) also were flagged. All of
the flagged samples were associated with azoic conditions.



Recolomzation of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



17

4.0 DISCUSSION

4.1 Summary of Ecological Conditions at MQR, 1992

All of the REMOTS® parameters indicated that the benthic environment has improved
in the year between the 1991 and 1992 surveys. No apparent "fresh" dredged material was
observed in 1992. This was a significant difference from the results in 1991. The fresh
dredged material appearance was a function of the low RPD (and low DO) conditions at
several stations in 1991 combined with boundary roughness values which emulated the
appearance of newly disposed dredged material. The combination of increased RPD, less
methane, and the lack of low DO in 1992 resulted in overall higher OSIs relative to the 1991
survey.

Although the 1992 REMOTS® results indicate an improvement in benthic habitat over
1991, the fact remains that several parameters are still significantly out of the range of CLIS
reference values. Comparing REMOTS® results between different years and stations is
somewhat risky; however, the overall historical trend of OSIs at the CLIS reference area
indicates that the average OSI of the undisturbed area hovers between 8 and 10. The
persistence of slow recolonization at MQR and the continuing presence of methane almost 10
years after dredged material deposition suggest that there is still an inherent quality of MQR
sediments which discourages normal benthic recolonization.

4.2 Historical Progression of the MQR Benthic Habitat

The DAMOS Program benefits from the fact that over ten years of data have been
collected at MQR. MQR historically has been the slowest among the disposal mounds at
CLIS to recover from stress. This characteristic has triggered more intensive monitoring in
recent years (Table 1-1). Observations from REMOTS® surveys were summarized in order
to approach the problem of MQR benthic habitat recovery from a historical context. In
summarizing these data, OSI values from the CLIS reference areas were averaged for each
time period the site was sampled. Historical OSIs from MQR and other CLIS dredged
material disposal mounds were plotted relative to the CLIS reference area to map the long-
term trends of habitat quality (Figure 4-1, Figure 4-2).

A concise summary of several CLIS mounds is necessary as a reference to the MQR
mound. A complete history of the disposal mounds at CLIS was recently compiled (SAIC
1994). In the spring of 1983, contaminated material from Black Rock Harbor was disposed
at several CLIS mounds including MQR, the Field Verification Program mound (FVP), and
Cap Sites 1 and 2 (CS-1 and CS-2; Figure 1-1). Both Cap Site mounds and MQR were
capped with material from New Haven Harbor, while FVP remained uncapped.



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



18



12



9.6 -



7.2 H

0)

CD

§4.8^
<



2.4




Feb




-82



Nov-84



Aug-87
Survey Date



May-90



Jan-93



CLIS REF



MQR Center -©- CS-1 Center



Figure 4-1. Average OSI values from the CLIS Reference Area (all stations), and data
collected from the centers of MQR and CS-1



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



19



12



9.6



O 7.2

CD
D)
CD

L.

CD

% 4.8



2.4















OSIs averaged for all stations within
100 meters of the center station.


■ 9










▲ \ /








^"\^


Postdisposal N
Surveys


/ X

■ /

Post-Hurricane
Gloria Surveys




N A Hurricane
I Bob


i






i


T

i



Feb-82



Nov-84



Aug-87
Survey Date



May-90



Jan-93



FVP



MQR



CLIS REF



Figure 4-2. Comparison of the progression of OSI values at MQR and FVP relative to the
CLIS Reference Area



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



20

REMOTS® postdisposal surveys indicated that recolonization was occurring at all of
these mounds, including FVP, and that MQR was the slowest to recover. Hurricane Gloria
had a substantial impact on the benthos at most of the CLIS mounds in 1985, especially the
FVP mound (Figure 4-2). Following the Hurricane Gloria survey, two REMOTS® surveys
in 1986 and 1987 documented the cycle of recovery following the storm and again indicated
that MQR did not recover quite as quickly as the other mounds.

The 1986 survey at CLIS concluded that the lowest mean OSIs occurred at STNH-S,
NH-83, and MQR, which are all located along the southern border of CLIS (Figure 1-1).
One suggestion to explain this phenomenon was hypoxic bottom water conditions,
concentrated at the southern rim of CLIS, which would prevent or inhibit colonization of
these mounds (SAIC 1990a).

The 1986 report also noted that MQR "continues to have the slowest rate of benthic
ecosystem recovery, possibly the result of chemical contamination combined with hypoxic
effects." RPD values were significantly shallower than at the reference area. The low OSI
values were a function of the thin RPDs, dominance of Stage I, and presence of methane.
Surface sediment chemistry results from MQR indicated that the mound had statistically
higher concentrations of metals and oil/grease relative to reference area values. Conversely,
the FVP mound showed that trends towards shallower RPDs which had been documented in
March and October of 1985 had been reversed and that the percent of stations showing Stage
III had increased (SAIC 1990a).

In the following year, MQR had RPDs which were consistently deeper than the
previous survey (SAIC 1990b). The presence of dredged material and pockets of methane
were similar to the previous survey. Methane was noted as being unusually high and
persistent in this sediment. The presence of Stage III organisms increased from 31% of
replicate images in 1986 to 46% in the 1987 survey.

The OSI is sensitive to conditions which cause stress to the benthic environment. A
clear example is the passage of Hurricane Gloria; surveys were conducted immediately
following the storm, and the resulting change in OSIs demonstrates the substantial effects on
the benthos (especially at the mound apices), most clearly displayed at the FVP mound
(Figure 4-1, Figure 4-2).

Comparing MQR and FVP is appropriate since (1) they were created at the same time
and (2) FVP remained uncapped and MQR capping material apparently contains some
elevated levels of contaminants (Murray 1992). Figure 4-2 shows the average OSI from all
stations within 100 meters of the center station for both MQR and FVP through time.

Postdisposal surveys at both MQR and FVP indicated that benthic communities of
both were detrimentally affected by disposal of dredged material. Although FVP was

Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



21

monitored more frequently, the resultant OSIs from both mounds are not significantly
different.

Hurricane Gloria affected FVP more severely than MQR; however, FVP recovered
more quickly than MQR (Figure 4-2). By 1987, both were progressing towards normal
(reference) OSI levels. The June 1991 survey documented the radical shift of OSIs at MQR
stations. Finally, Hurricane Bob and the "Halloween" storm of 1991, both of which
occurred after the 1991 CLIS survey, did not prevent the recolonization documented in the
1992 survey.

It is apparent that MQR has cycled through several stages of stress and recovery, and
that the recovery has been slower than at other CLIS mounds. The current state of MQR,
improved since 1991 but still below reference, is a result of the decrease of habitat quality
observed between the 1987 and 1991 REMOTS® surveys. A smaller scale decrease in OSI
values also occurred at CS-1 (from 11 to 7) during the same time interval (Figure 4-1). The
cause of the stress recorded at MQR during this time period is crucial to understanding
recolonization factors at MQR.

4.3 Recolonization Factors at MQR

Factors affecting habitat quality and postdisturbance recolonization are either chemical
or physical or both. Previous explanations of the slow benthic recolonization at MQR have
been chemical, including the presence of hypoxic water, a high organic content of MQR
sediments, and elevated levels of sediment contaminants (SAIC 1990a, Murray 1992).
Physical factors which may be responsible for benthic disturbance include both large-scale
and small-scale processes. Large-scale events include storms as in the obvious case of
Hurricane Gloria (SAIC 1989b); these events should affect all of the mounds at CLIS, as
well as the CLIS reference areas. Small-scale disturbances include biological (macrofauna)
and anthropogenic (trawling, etc.) sources. Both of these types of small-scale disturbances
could occur within individual mounds.

It is clear that both the concentrations of contaminants and the content of organic
carbon in the sediments at MQR are higher than at other capped CLIS mounds. High
organic carbon would be expected to ameliorate contaminant effects, to some extent, by
"removing" or binding contaminants so that they are not as available to biota. Results from a
recent coring study at MQR indicated that the capping material at MQR does contain
relatively high levels of polyaromatic hydrocarbons (PAHs) (Murray 1992). The presence of
methane in REMOTS® pictures as recent as the present survey indicates that relatively high
concentrations of organic carbon remain in the MQR sediments. However, the pattern of
recolonization determined from the sequence of OSIs at MQR suggests that recolonization
does occur, despite the potential stress associated with contaminated sediments.



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



22

The key question for MQR is the dramatic drop of OSIs which occurred in the time
interval between the 1987 and 1991 REMOTS® surveys. This sharp, localized decrease
suggests a physical cause (such as trawling), perhaps exacerbated by adverse chemical
conditions. The presence of numerous mud clasts and rip-ups, and evidence of surface
erosion in the REMOTS® photographs of the 1991 survey support this conclusion.
Additionally, since this decrease in OSI values is not widespread among the mounds at CLIS,
the cause of the stress must be localized physical disturbance.



Recolonizatwn of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS' 6 Survey, August 1992





5.0 SUMMARY AND RECOMMENDATIONS

• Routine monitoring at MQR has indicated a pattern of anomalous
recolonization relative to other CLIS capped mounds. Historically, MQR has
exhibited slow recolonization rates relative to other capped mounds at CLIS.

• MQR provides an excellent test case for the dredged material management
protocols as described in the Tiered Monitoring Program created for the NED.
It is the first mound to trigger higher tiers of monitoring and testing, under the
tiered monitoring framework. Following these tiered protocols, several
monitoring surveys, including REMOTS® work and sediment sampling, have
been conducted at MQR.

• A reconnaissance REMOTS® and bioassay survey in 1991 showed a substantial
regression of benthic environmental parameters since the previous survey in
1987, which suggested a small-scale physical disturbance.

• Results from the 1992 REMOTS® survey at CLIS showed a clear improvement
of the habitat quality at MQR since the 1991 survey, although still anomalous
relative to the CLIS reference area.

• The persistence of slow recolonization since the formation of MQR, together
with sediment chemical results presented in an earlier report, indicate that
MQR should be further capped, and monitoring should continue.



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



24

6.0 REFERENCES

Germano, J. D.; Rhoads, D. C; Lunz, J. D. 1994. An integrated, tiered approach to

monitoring and management of dredged material disposal sites in the New England
region. DAMOS Contribution No. 87 (SAIC Report No. SAIC-90/7575&234). US
Army Corps of Engineers, New England Division, Waltham, MA.

Murray, P. M. 1992. Sediment core chemistry data summary from the MQR Mound, August
and December, 1991. SAIC Report No. CI 05. Final report submitted to US Army
Corps of Engineers, New England Division, Waltham, MA.

Rhoads, D. C; Germano, J. D. 1982. Characterization of organism-sediment relations using
sediment-profile imaging: an effective method of Remote Ecological Monitoring of
the Seafloor (REMOTS™ System). Mar. Ecol. Prog. Ser. 8: 115-128.

SAIC. 1985. Standard operating procedure manual for DAMOS monitoring activities.

DAMOS Contribution No. 48 (SAIC Report No. SAIC-85/7516&C48). US Army
Corps of Engineers, New England Division, Waltham, MA.

SAIC. 1989a. Monitoring surveys at the New London Disposal Site, August 1985 - July
1986. DAMOS Contribution No. 60 (SAIC Report No. SAIC-86/7540&C60). US
Army Corps of Engineers, New England Division, Waltham, MA.

SAIC. 1989b. 1985 monitoring surveys at the Central Long Island Sound Disposal Site: an
assessment of impacts from disposal and Hurricane Gloria. DAMOS Contribution
No. 57 (SAIC Report No. SAIC-86/7516&C57). US Army Corps of Engineers, New
England Division, Waltham, MA.

SAIC. 1990a. Monitoring cruise at the Central Long Island Sound Disposal Site, July 1986.
DAMOS Contribution No. 63 (SAIC Report No. SAIC-87/7514&C63). US Army
Corps of Engineers, New England Division, Waltham, MA.

SAIC. 1990b. Monitoring cruise at the Central Long Island Sound Disposal Site, August and
September, 1987. DAMOS Contribution No. 68 (SAIC Report No. SAIC-
88/7523&C68). US Army Corps of Engineers, New England Division, Waltham,
MA.

SAIC. 1994. Sediment capping of subaqueous dredged material disposal mounds: an

overview of the New England experience. SAIC Report No. SAIC-90/7573&C84.
Final report submitted to US Army Corps of Engineers, New England Division,
Waltham, MA.



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



25



Wiley, M. B.; Charles, J. 1994. Monitoring cruise at the Central Long Island Sound

Disposal Site, June 1991. SAIC Report No. SAIC-92/7621&C100. Draft report
submitted to US Army Corps of Engineers, New England Division, Waltham, MA.



Recolonization of the Mill-Quinnipiac River Disposal Mound (MQR): Results of a REMOTS® Survey, August 1992



INDEX



aerobic 13
azoic 10, 16

benthos v, 1,4, 5, 7, 8, 10, 17,
20, 21, 23
amphipod 1, 3, 5, 10
bivalve 10
deposit feeder 10
macro- 8, 13, 21
polychaete 10
bioassay 1, 3, 5, 7, 23
bioturbation

feeding void 10
Black Rock Harbor 1, 3, 17
body burden 3

bioassay 1, 3, 5, 7, 23
boundary roughness iv, 8-10, 17
capping 5, 7, 13, 20, 21, 24
Central Long Island Sound (CLIS)
iv, v, 1, 2, 4, 5, 7,
8, 10, 13, 17-25
Capsite-1 (CS-1) iv, 17,

18, 21
Capsite-2 (CS-2) 17
FVP iv, 17, 19-21
MQR 1, ii, iii, iv, v, 1,

3-24, 27
New Haven-83 (NH-83) 20
STNH-S 20
colonization 5, 20
contaminant 20, 21
currents 8
density 3, 5, 7
deposition 1, 10, 17
disposal site

Central Long Island Sound
(CLIS) iv, v, 1, 2,
4, 5, 7, 8, 10, 13,
17-25
New London 24
dissolved oxygen 10, 16
erosion 22
feeding void 10

Field Verification Program (FVP)
17



grain size 5, 7, 8

habitat v, 1,4, 7, 10, 17, 21, 23

hurricane 3, 20, 21, 24

methane 13, 16, 17, 20, 21

mud clast 8, 22

organics

polyaromatic hydrocarbon
(PAH) 21
oxidation 5
recolonization 1, v, 1, 17, 20, 21,

23
reference area iv, v, 4, 5, 7, 8,
10, 13, 17-20, 23
REMOTS®

boundary roughness iv,

8-10, 17
Organism-Sediment Index
(OSI) iv, 7, 13-22
redox potential discontinuity
(RPD) 10, 20
REMOTS® 1, ii, iv, v, 1, 3-9,
11-17, 20-23, 27
camera 7
RPD

REMOTS®; redox potential
discontinuity (RPD)
iv, 10, 11, 13, 17,
20
RPDs

REMOTS®;redox potential
discontinuity (RPD)
10, 20
sediment

chemistry 20
clay 7
silt 7
sediment sampling 23
cores 3, 24
grabs 5
species

dominance 20
statistical testing 20
succession 10

pioneer stage 10



INDEX (cont.)



successional stage iv, 7, 10, 12
survey

bathymetry 3, 5

postdisposal 3, 20

predisposal 3

REMOTS® 1, iv, v, 1, 4,
5, 7, 9, 11-15, 17,
20-23
topography 8
toxicity 5
trace metals 3, 20
trawling 21, 22
waves 8



APPENDIX



MQR REMOTS®DATA, AUGUST 1992



y-








CM


en


"*


ID






■f


CO


m


00


CO


m


CO


00




1^- CD


■*


CO


■*r


CO


in


co


■«t


in


in m


Q L7j

Q.


LO


oo


CO


CO


CD


•*t


o


1-


co


m


">!-


CN


CO


CM


CO


IT)


■f CT)


CO


o


r^


CN


in


o


o


T—


T- 00


■<r


T


■<*


m


CO




ID


IT)


-*


in


m


r-


•<*■


CD




CD


CO


cd m


■«»■


in


■<T


m


t


CD


CD


r^


r^ co


























































IS


























































o


o


o


o


o


o


O


o


O


o


O


o


o


o


o


o


O


o


o o


co


o


o


o


o


o


o


o


O CN


«3


o


o


o


o


o


o


o


o


o


o


o


o


o


o


o


o


O


o


o o


in

CD


o


o


o


o


o


o


o


CD

°5


t-


























































P5


o


o


o


o


o


o


o


o


o


o


o


o


o


o


o


o


o


o


o o


-


o


o


o


o


o


o


o


O T-


Q.


























































W








■a


■a








TO




























TO




TJ




TO


T3 T3


s <


X


75
CD


X


CD
N
TO

x


a>

N
TO
X


sz
75

m


X


X


a>

N
TO

'x


X


X


X


X


X


X


X


X


X


X X


X


sz
75
CD


sz
75
CD


CD
N
TO
X


X


cu

N
TO
X


X


cu

N
T3
X


<u a>

N N
TO TO
X X


03








O O








U




























o




O




O O O


O <
^5




co




<*


T


co






>*
























h-


CD


co




,_




r^-


1^- CN


o


■>3-


o


CD


CO


o


o


r*-


o


o


o


o


o


o


o


o


o


o o


o


r-~


■<J-


o


in


o


r-


r^ r^




o




O


o








o
























o




o




o




o


o o


i3


o


CO


o


■*


CN


CN


o


o


*-


o


o


o


o


o


o


o


o


o


o o


o


m


■*


CN


o


■*


o


in


CO i-


o














































co












Q LU


co


■*


CN


-*


m




■*




■f


co


cr>


oo


■<*


CJ)


,_


CO


CN


^r


t- CN


CO


.^


00


r-


oo


co


CO


co ■<*


0- >


CM


r^-


CO


•*


T—


r-


o


CO


T -


r-


co


O)


«""


00


o


o


O)


CO o


CD


m


o


oo


r-


U)


oo


t-


CN CD


a: <


*-




*~


T_


T_




T_




*-


"■-


o


T_


o


,,_


o


CN


"-


o


O T-


O


"-


CN


o


"-


o


T_


"-


*- ^


n w


T


'S-


t


-«■


-*


■<*


■*




>*


"3"


••T


•<t


■*


•«f


TT


TT


■*!-


■<!-


•*!■ •*


■*


tj-


"*


"fr


t


■«3-


2

Online LibraryPeggy M MurrayRecolonization of the Mill-Quinnipiac River Disposal Mound (MQR) : results of a REMOTS survey, August 1992 → online text (page 2 of 3)