The role of ecosystem ecology in estuarine ecosystem managment Mike Piehler UNC-CH Institute of Marine SciencesUNC Coastal Studies Institute

“We can't solve problems by using the same kind of thinking we used when we created them.” Albert Einstein

A.Partnerships -- Those people most affected by management decisions are involved throughout and shape key decisions. B.Geographic Focus -- Activities are directed within specific geographic areas, typically the areas that drain to surface water bodies or that recharge or overlay ground waters or a combination of both. C.Sound Management Techniques based on Strong Science and Data i.assessment and characterization of the natural resources and the communities that depend upon them; ii.goal setting and identification of environmental objectives based on the condition or vulnerability of resources and the needs of the aquatic ecosystem and the people within the community; iii.identification of priority problems; iv.development of specific management options and action plans; v.implementation; and vi.evaluation of effectiveness and revision of plans, as needed. Watershed Approach

Watershed conservation, restoration and rehabilitation Terrestrial Land-water margin Aquatic Atmospheric

Sources Transport Transformation

Water management Minimize consumptive uses Remove obstructions Maintain natural connectivity between aquatic and terrestrial systems Consider flow management where tenable

Nutrient management Identify limiting nutrients Identify sources of the limiting nutrients in the watershed Identify a tenable and effective reduction target Manage point sources where possible Manage non-point sources as appropriate

Application of ecosystem ecology Are BMPs really the best? Can estuarine nutrient management exacerbate eutrophication? Is the application of ecological threshold theory of value to estuarine nutrient management?

A cap on nitrogen load and a 30% loading reduction have been mandated for the Neuse River Estuary (NRE) watershed Neuse River Estuary

Includes rules for wastewater, urban stormwater, agriculture and general nutrient management Utilization of agricultural Best Management Practices (BMPs) is among the alternatives for agricultural operations in the NRE to become compliant under the Neuse Rules Understanding the effectiveness of BMPs such as constructed wetlands is critical to guiding the process and eventually assessing the success of the nutrient reduction efforts “The Neuse Rules”

Open Grounds Farm ~45,000 acre row crop farm Crops include corn, soybeans, wheat and cotton Constructed wetland built in 1999 on 20 acre site Significant proportions of the runoff from OGF enters the South River and then the NRE

Monitoring and Analyses

32% 46% 34% The bottom line…

Open Grounds Farm – 2001 Dry much of the year Watershed of the wetland was planted in corn Fertilizer spill ~ gallons 50% UAN 50% (N-P-K)

Wetland Nutrient Loading

Nitrate removal and Denitrification

ug l -1 nitrate ammonium phosphate Neuse River Estuary

Why worry about stimulating estuarine microbial N 2 fixation? Many N 2 fixing species are nuisance organisms, and their proliferation may decrease water quality Biological fixation of N 2 may circumvent engineered N loading reductions Selection for N 2 fixing organisms may cause trophic disruption by increasing abundances of less palatable or less nutritious phytoplankton 10  m a. f. d. c. b. e. Anabaena aphanizomenoides (a) Anabaenopsis sp. (b) Cylindrospermopsis raciborskii (c, d) Anabaena compacta (e, f)

Dilution Bioassay Setup Control 30% Dilution 10L Neuse River 7L Neuse River Water 3L Major Ion Solution 30% Dilution water +P Marker 15 N & P reduced N reduced N:P reduced

July 1997 Acetylene Reduction / chlorophyll a (nmol C 2 H 4 l -1  g Chl a -1 h -1 ) Assimilation Number (mg C mg Chl a -1 h -1 ) Assimilation Number Acetylene Reduction

July 1998 Acetylene Reduction / chlorophyll a (nmol C 2 H 4 l -1  g Chl a -1 h -1 ) Assimilation Number (mg C mg Chl a -1 h -1 ) Assimilation Number Acetylene Reduction

August 1998 Acetylene Reduction / chlorophyll a (nmol C 2 H 4 l -1  g Chl a -1 h -1 ) Assimilation Number (mg C mg Chl a -1 h -1 ) Assimilation Number Acetylene Reduction

What is the potential importance of N 2 fixation to the NRE N budget? 7x10 7 m x 10-5 mol N m-3 y d y-1 12 h d-1 2 m deep 3.5X10 4 kg N as much as 3% of riverine DIN load to NRE

Evolving scientific basis for management Ecological thresholds Ecosystem responses to forcing are often discontinuous and non-linear Threshold - A critical value of a pressure beyond which a state indicator shifts to a different regime

Ultimate Driver Proximal Driver Status Indicator = f Ecological goods and services e.g. nutrient concentrations and/or flow regime e.g. land use

TP Year TP (µM) TP Year Chlorophyll a (µg L ) Chl a

nitrogen load phytoplankton estuarine ecosystem services  TMDL for nitrogen in the Neuse River Estuary  

Riverine DIN and mid-estuary chlorophyll a