Ocean Acidification

SESSION A: Ocean Acidification – What is it, what have we learned, what are the critical knowledge gaps, and what can we do about it?

Chair: Susie Arnold, Island Institute

Session Description: Improving our understanding of Maine’s susceptibility to ocean acidification (OA) is of the utmost precedence. With nearly 90% of Maine’s fisheries landing by value from shell producing species, the potential implications of OA are sobering. Predictions of continuing declines of pH raise questions about the long-term viability of these fisheries. One recommendation for local action to mitigate acidification of coastal waters coming out of the recent Legislative Study Commission on OA included the need to identify and reduce nutrient loading and organic carbon from sources determined to cause or contribute to OA. The goal of this session is to raise awareness about OA and present updates on research and monitoring as well as remediation, mitigation, and adaptation strategies.

Presentations Available

Session Overview

8:30-8:55 am
Ocean Acidification: A Global Problem Being Addressed Locally
Michael Devin, Maine House of Representatives

Ocean acidification is a global problem and associated with other phenomena impacting Earth. It is complex and most state and national governments are reluctant to address it, even as their fisheries and aquaculture industries are impacted. The common belief is OA cannot be addressed locally. Several states, including Washington State and Maine, reject this tenet and moved forward to create a political environment to address the issues associated with OA.

The 126th Legislature established Maine’s Commission to Study the Effects of Coastal and Ocean Acidification and Its Existing and Potential Effects on Species That Are Commercially Harvested and Grown along the Maine Coast. Over the course of five months the commission developed six goals to mitigate the impacts of OA Maine’s coastal and marine environment, which provide the basis for moving forward. Follow-on legislation has been introduced into the 127th Legislature.   Additionally, Maine legislators are working to ensure all states and provinces that border the Gulf of Maine develop similar policies to address OA.

9:00-9:25 am
Sediment Acidification in Casco Bay

Mike Doan, Friends of Casco Bay, South Portland, ME

In lab studies, sediment with high acidity and low aragonite saturation state has led to reduced clam spat settlement and potential shell dissolution. Over the past few years Friends of Casco Bay has been exploring ways to measure coastal sediment pH and identify flats that may exhibit acidic conditions. Since 2011, a baseline of clam flat pH conditions has been established, and data has been collected on the relationship between pH and organic enrichment. More recently, spatial and temporal trends in sediment pH have been identified at one flat in Casco Bay, and sediment pH and sediment aragonite saturation state have been compared. Overall, the data suggests that clam flats in Casco Bay are showing signs of acidification.

9:30-9:55 am
Tracking low pH episodes in the Georges River Estuary; ocean acidification from the land and sea
Theodore Willis,
University of Southern Maine, Environmental Science, Portland, ME
Jonathan Eaton, Georges River Tidewater Association, Thomaston, ME
Celeste Mosher, Georges River Tidewater Association, Thomaston, ME

Eutrophication and its contribution to poor water quality has been a concern in the St. George River Estuary since 2002. The estuary is a long, narrow drowned river mouth located between Port Clyde and Thomaston, ME, on the eastern edge of Muscongus Bay. River flows are a “trickle”, except after storm events, so the tidal signal is strong well into the lower St. George River. Consequently, water turnover in the estuary requires upwards of 15 days to fully flush. This is a concern because the St. George Estuary hosts one of the most valuable softshell clam fisheries in the state of Maine. Volunteer based estuary monitoring in 2012 revealed low dissolved oxygen episodes related to rainfall events, and low pH episodes that did not correspond with rainfall events. Further investigation in 2013 and 2014 also indicated that low pH, on the order 6.8 near the bottom, occurred in the lower estuary and lasted for over three weeks in late summer. Data from 2013 indicated that low pH episodes correlated most strongly with prolonged, strong SW winds. The long, narrow topography of the drowned river mouth extends underwater for several miles within Maine state waters, where depths may be 300 ft. Persistent winds combined with the Coriolis effect may create upwellings that bring deep water with high CO2 content to the surface along the coast, where it produces pH readings well below levels predicted to impact bivalves and other shell forming organisms.

10:00-10:25 am
Management of Nutrients in Point and Non-Point Sources in Maine
Aubrey Strause, Past President, Maine Water Environment Association, Scarborough, ME
Robyn Saunders, Program Director, Cumberland County Soil & Water Conservation District, Windham, ME

Maine’s Commission to Study the Effects of Coastal and Ocean Acidification and Its Existing and Potential Effects on Species That Are Commercially Harvested and Grown along the Maine Coast has identified nutrient management and reduction as a critical component of mitigating the effects of ocean acidification in Maine.

Nutrients enter surface waters through a combination of point sources (such as wastewater treatment facilities and engineered stormwater systems) and non-point sources (such as agricultural runoff, residential application of fertilizer, and improper disposal of pet waste). Point and non-point sources across the State are regulated under a number of programs that have resulted in improvements to water quality in recent decades.

In this session, the authors will review the management of nutrients from point and non-point sources, with the purpose of providing insight into regulatory programs that are not well understood by the public. We will provide a context of the relative loadings of nutrients to surface waters derived from models across New England, identify current and proposed funding sources for these programs, identify outreach programs that are demonstrating improvements, and review proposals to expand or revamp regulatory framework.

Finally, we will review challenges facing municipalities as they seek to further reduce nutrients entering surface waters, including fiscal constraints, incomplete understanding of the issue by the general public, and the limits of technology for nutrient removal.