Heterogeneity in Urban River Ecosystems:Understanding the contribution of natural and anthropogenic factors on whole stream metabolism in ponded areas of the

Ipswich River Watershed

Joshua S. CainWil Wollheim

1. BackgroundThe Issue: Many reaches within the Ipswich River Watershed are characterized by low dissolved oxygen content, which threatens fish populations, aquatic organisms, and the health of the entire ecosystem. •Anthropogenic factors, including nutrient loading, road crossings, etc. and natural beaver dams found in this suburban watershed influence metabolism . •Little is known about the influence of fluvial wetlands on the dissolved oxygen, metabolism, and nutrient dynamics of a river network (O Brien et al. 2012).

Project Summary: This study will focus on understanding the interaction of geomorphology, dissolved oxygen, metabolism, and nutrients in a suburban river network. The project proposes to measure stream metabolism in natural and anthropogenically altered portions of a river network to better understand the influence of fluvial wetlands on dissolved oxygen content and metabolism rates observed downstream.

2. Research Question and Hypotheses:Q1:What Is causing the extremely low dissolved oxygen content and high metabolic rates observed in streams of the Ipswich river watershed?Hypotheses: •Fluvial wetlands are extremely heterotrophic, driving down oxygen, while re-aeration in channels is low, keeping depressed oxygen levels over long reaches.•Humans are exacerbating this issue through road crossings with inadequate culverts, and water withdrawals, that are increasing inundation of fluvial wetlands, and reducing re-aeration rates.

5. Preliminary Results (Chestnut site)•Dissolved oxygen steadily decreases along the transect from above the wetland to outflow of the lower wetland (Figure 2).

4. Approach:

Overarching Approach: Dissolved oxygen, metabolism, and biogeochemical patterns will be measured continuously for weeklong periods at each study site during base flow conditions.•There will be 8 sites• Within each site, there will be 3 logger locations (sub sites)

• one channel uninfluenced by fluvial wetland, one fluvial wetland (pool), one channel downstream of wetland

•Seasonality will be addressed: measurements in spring, summer, fall.

Site Selection: • Encompass a variety fluvial wetland/ponds. (Figure 1)

• beaver ponds, through-flow wetlands, back ups from culverts and debris dams, etc.

Metabolism Measurements:• Single Station Method• dDO/dt = GPP – R – A (Odum 1956)

• Hobo DO loggers • above the ponded environment, just below the pond, and further down

stream (channelized).• Odyssey light loggers will be placed in accordance with each DO logger.• Measurements will be taken every 15 min. •GPP and Respiration will be calculated based on the diel change in DO (Owens 1974). •re-aeration will be calculated using dark regression method (Young and Huryn 1999).

Site Characteristics:•Surface Area of water will be measured using either physical measurements, or GIS • Quantify the area each station is characterizing and investigate if the percent of DO depleted increases with pond area.• Discharge will be calculated to characterize the water movement at each site (flow meters? rating curve?)

Nutrients:•Grab samples will be taken 3 times per week to and tested for multiple constituents, including ammonium, anions (including NO3, SO4, and Cl), phosphate, dissolved organic carbon (DOC), and total dissolved nitrogen (TDN). •This will allow us to understand interactions between GPP, R, and nutrients.

References:1.O’Brien, J. M., Hamilton, S. K., Kinsman-Costello, L. E., Lennon, J. T., & Ostrom, N. E. (2012). Nitrogen transformations in a through-flow wetland revealed using whole-ecosystem pulsed 15 N additions, 57(1), 221–234. doi:10.4319/lo.2012.57.1.02212.Odum, H.T. 1956. Primary production in flowing waters. Limnology and Oceanography 1(2):102-117.3.Owens, M., 1974. Measurements on non-isolated natural communities in running waters. In: Vollenweider, R.A. (Ed.), A Manual on Methods for Measuring Primary Production in Aquatic Environments. Blackwell Scientific Publications, Oxford, UK, pp. 111–119.4.Young, R. G., & Huryn, A. D. (1999). EFFECTS OF LAND USE ON STREAM METABOLISM AND ORGANIC MATTER TURNOVER. Ecological Applications, 9(4), 1359–13765.http://www.ourworldfoundation.org.uk/turbine.jpg - - background photo

6. Next Steps:•Identify Sites•Is the one station method going to highlight patterns observed in the entire pond, or do measurements need to be taken within the pond as well?• Transect sampling to understand why DO remains low even in channelized areas

Above Wetland (channel)

Within Wetland (before culvert)

Below Wetland (channel)

Figure 2: Dissolved oxygen and temperature patterns at the Chestnut Site during October and into November

Figure 1: Chestnut Street Site. Courtesy of Ken Sheehan