Population assessment and potential functional roles of native mussels in the Upper Mississippi River

Abstract

ABSTRACT1. Despite a heightened global concern for native mussels, fundamental research on mussel ecology in large rivers is lacking. These gaps in knowledge about where mussels occur, and why, are limiting habitat restoration activities.2. Large-scale systematic surveys for native mussels in three reaches of the Upper Mississippi River documented mussel communities composed of 16-23 species and ranging from 2.9-4.5 live mussels m À2 that were actively recruiting new cohorts into their populations (87-100% of the species were found as juveniles p5 years old). Estimates of mean tissue biomass and production in these reaches ranged from 2.1-3.1 g C m À2 and 0.4-0.6 g C m À2 year À1 , respectively. 3. Mussels filtered a significant amount of water (range, 0.05-0.07 m 3 m À2 d À1) over a 480 km reach of the Upper Mississippi River -amounting to a filtration rate of 53.1 million m 3 day À1 . The filtration rate of mussels as a percentage of river discharge ranged from 0.5-1.4% at high flows (5% exceedance), from 1.5-4.4% at moderate flows (50% exceedance) and from 4.4-12.2% during low flows (95% exceedance).4. Collectively, these data suggest that native mussels play an integral role in this ecosystem by sequestering suspended materials that can be used by other benthic organisms.

Simulated mussel mortality thresholds as a function of mussel biomass and nutrient loading

“…Twelve adult A. plicata and 13 adult L. cardium were placed in one mesocosm and 13 A. plicata and 12 L. cardium were placed in another mesocosm. This approximates a density of 70 mussels m −2 , which although high, is still a realistic density in some reaches of the UMR (Newton et al, 2011). Across both mesocosms, shell length (±1 standard deviation) was 95 ± 20 mm in A. plicata and 120 ± 25 mm in L. cardium .…”

“…These benthic, burrowing, and suspension-feeding bivalves stimulate production across multiple trophic levels (Vaughn, Nichols & Spooner, 2008); the biomass of healthy mussel beds can exceed the biomass of all benthic organisms by an order of magnitude (Negus, 1966; Layzer Gordon & Anderson, 1993). There are billions of mussels within the Upper Mississippi River (UMR) and the filtration capacity in a 480 km segment (about 13% of the river length), as a percentage of river discharge, is estimated to be up to 1.4% at high flows, up to 4.4% at moderate flows, and up to 12.2% during low flows (Newton et al, 2011). Collectively, these mussels filter over 14 billion gallons of water, remove tons of particulate organic matter from the overlying water, and deposit tons of ammonium (NH), associated ammonia (NH 3 ), and carbon at the sediment-water interface each day.…”

“…The model was calibrated using literature values and water chemistry measurements from a separate, 7-d mesocosm sampling period reported in our previous work (Bril et al, 2014). The mussel species Amblema plicata and Lampsilis cardium were selected due to their abundance in the Iowa River (Zohrer, 2006) and throughout the UMR Basin (Newton et al, 2011), where N runoff from industrial agriculture severely impacts the aquatic N cycle. This research is novel in that a multi-rate nitrification/denitrification model was developed, calibrated, and evaluated with sensor-based, highly time-resolved data from mesocosms containing mussels.…”

Sensor data as a measure of native freshwater mussel impact on nitrate formation and food digestion in continuous-flow mesocosms

“…As a consequence, mussels can influence a variety of biogeochemical cycles in waters they inhabit. Amblema plicata and Lampsilis cardium are mussels of interest for N-cycle studies because they make up a large fraction of the mussel biomass in the Iowa River (Poole and Downing 2004) and the Upper Mississippi River watershed (Zohrer 2006, Newton et al 2011, which are plagued with N management issues (Goolsby et al 2001).…”

Developing a shared understanding of the Upper Mississippi River: the foundation of an ecological resilience assessment

“…Mussel community Native freshwater mussels play an important role in the functioning of large river ecosystems through effects on nutrient and energy cycling that results from their substantial rates of water filtration and processing (Newton et al 2011). In general, mussels have experienced a substantial, long-term decline because of historical, commercial exploitation, and periods of poor water quality Theiling 1999, Anthony andDowning 2001).…”