EVIDENCE OF IMPACTS

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EVIDENCE OF IMPACTS FROM EXCESS NUTRIENTS IN
NARRAGANSETT BAY Past , Present , Future
 Christopher F. Deacutis Dept Biol. Sciences,
URI Brown University Center For Environmental
Studies (Adjunct) deacutis_at_gso.uri.edu Special
Thanks To Drs. Warren Prell David Murray,
Emily Saarman (Brown U.), Drs. Dana Kester
(deceased), Deanna Bergondo, Candace Oviatt, URI
GSO all the 1999-2003 Insomniacs RI
SeaGrant Nutrient Symposium November 17-18,
2004 Block Island, RI  
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A word of caution dont forget the response in
the shallows!
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Multi-Species Kills in Narragansett Bay
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Dead are bacteria- food Hydrogen Sulfide
(rotten eggs) grows sulfur bacteria mats on the
bottom in the anoxic areas
Beggiatoa mats on bottom anoxic zone
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Evidence of change in demersal fish community ?
From M. Gibson (RIDEM FW)
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Hypoxia Duration ?
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Stage 3 Stage 1 deeper living sp
shallow/surface (aerate the sed.) living deep
aRPD shallow aRPD equilibr.sp
opportunist -
pioneering sp. deposit deposit
feeders filter feeders high individual
low indiv. Biomass
biomass long-lived short-lived
Zone of decreased Nitrific Denitric
Measuring Benthic Community Impacts
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Benthic Community Impacts ?
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Temp. loss of sens. sp.
Perm. loss of other sens. sp.
Perm. loss of the most sens. sp.
Degraded benthos- pollution-tolerant opport. sp.
Major degradation - small short- lived
opport. sp.
Hypothesized relationship between hypoxia freq.
duration and summer benthic succession stage in
Narragansett Bay (modified from Diaz and
Rosenberg 1995)
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SEVERITY DRIVERS water col. Chl a TOC / (SOD
?)( ) Duration of stratification (no change
expected) local residence time while under
stratified condition (FW-climate driven)
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• CONCLUSIONS
• Upper Half of Narragansett Bay is under excess
  nutrient stress and resulting ecological impacts
• Impacts include significant SAV loss hypoxia
  (lt3.0 mg/L) and even short-duration severe
  hypoxia (lt1.0 mg/L) from head of Bay all way to
  Upper Bay, Greenwch Bay, Upper West Passage
  Upper East Passage
• Proposed Treatment Levels for major WWTFs (5 mg/L
  TotN) - projected to decrease present Prov R
  totN load by 58-42 (drops to 42 - 28
  decrease at design flows)
• Could reach 1900 loadings levels period of
  good shellfish (aquaculture) yields and eelgrass
  in the Upper Bay
• Potential to Decr. Severity geogr extent of
  hypoxia less likely duration
  change watch the hot zone Upper Bay
  So. Prov. River

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Any evidence of Positive Responses in Other
Systems w/ Decreased N load ?
Is there potential to reach tot N level too low
to sustain present fisheries w/ the projected AWT
load decreases?
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DRY HOT Aug 6, 2002
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Softshell Kill (Mya arenaria) 8-28-03
So. of Chepiwanoxet Cedar Tree
Pt-Greenwich Bay ( day 15 of bottom
anoxia) (15-20 day endurance) Adult
Quahogs gt30days!
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WWTF Between 66-73 of total N load
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Estuarine Flow Patterns
Lynn Carlson, Brown U. GIS lab