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

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. 2005- 30% Reduction in Standing Stock nitrogen concentrations in the Bay 2013 50% Reduction in Standing Stock nitrogen concentrations in the Bay

Summer Production 2013

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

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

The Number of Summer Days of Hypoxia has Decreased.

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

Total Fish Biomass Before and After Nitrogen Reduction.

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.