1. The Bay After Nutrient Reduction
Habitat Indicators: Primary Production, Winter Spring Diatom Bloom, Summer Hypoxia and Fish Biomass
Candace Oviatt, Heather Stoffel, Laura Reed, Edwin Requintina
Graduate School of Oceanography, URI
CHRP Presentation – Coastal Institute Hazzard Rooms
May 19, 2016

2. Improvements in the Bay due to the Clean Water Act of 1972
and Amendments of 1977, 1987
1988 Used Oil Recycling Program
Heavy Metal Recycling Program
Millions of gallons of used oil collected and recycled.
Heavy metals at low background concentrations during 2001
Providence River Survey.
1993- Combined Sewer Over-Flow Abatement Program
Phase I and 2 completed in 2008 and 2014.
Reduced bacterial contamination of Bay beaches and new shell-fishing
grounds opened.
% Reduction in Standing Stock nitrogen concentrations in the Bay
% Reduction in Standing Stock nitrogen concentrations in the Bay

3. Summer Production 2013

6. Summer Surface System Apparent Production, g O2 m-3 d-1

7. Winter-Spring Diatom Bloom 2014 in the Upper Bay (CP), Mid Bay (GB & TW) and Lower Bay (GSO)

8. The Number of Summer Days of Hypoxia has Decreased.

9. Percent Reduction in Hypoxia from 2012 to 2013 - 2014
Phillipsdale 27
Bullock Reach 46
Conimicut Pt 19
North Prudence 43
Popposquash Pt 37
Greenwich Bay 32
Mt. View
T-Wharf
100
Quonset Pt
GSO Dock

11. Total Fish Biomass Before and After Nitrogen Reduction.

12. Conclusions Managed DIN reduction has achieved about a 60% reduction.
Primary Production in the Bay has declined in mid Bay by 31-45%.
The Winter-Spring Diatom Bloom has declined by over 50%.
Summer hypoxia has declined in the upper Bay by 30%.
Fish biomass in the Bay has increased particularly in upper Bay areas prone to hypoxia.
The fish biomass after the 50% nitrogen reduction has decreased but is still higher than the decade prior to nitrogen reduction. This trend bears watching.
Overall water quality in the Bay has improved.