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Filtering rates of Dreissenids in Lake Erie
Collaborators
Steve Ruberg, GLERL
Hans Biberhofer, Environment
Canada
Project Rationale
The filtering impacts of larval and sessile dreissenids on the western
Lake Erie ecosystem are large. MacIsaac (1992) concluded that sessile
mussels would graze more than 1000 times the phytoplankton biomass that
planktonic veligers would feed upon. Their calculations showed that the
sessile mussels could filter 14 times the volume of the western basin
in just 1 day. Madenjian (1995) used a bioenergetics model for growth
of zebra mussels to estimate the removal of phytoplankton by mussels.
The zebra mussel population, as estimated in 1990, consumed 5.0 million
tons of phytoplankton and another 1.4 million tons of phytoplankton were
deposited as psuedofeces. If primary production is estimated to be 24.8
million tons, then zebra mussels removed 26% of the primary production
in western Lake Erie. There are no estimates of filtering impacts by mussels
in the central and eastern basin of Lake Erie.
More recent observations by various investigators have found that biomass of phytoplankton (chlorophyll a) in the central and eastern basins is at historically low levels. At the same time, the concentrations of total phosphorus (TP) have been increasing over the past 5 years, even though TP loadings to Lake Erie have not risen. It has also been observed that the central basin oxygen demand has not changed through the 1990s, and central basin hypolimnial oxygen depletion continues to occur. Such patterns are inconsistent with predictions and dynamics of models of internal lake function originally developed to guide management of Lake Erie's nutrient budget. These observations may represent situations that have naturally occurred at times prior to monitoring records. Alternatively, they may reflect consequences of novel environmental and biological pressures modifying energy and nutrient flow through the ecosystem. The compartments and transfer pathways hypothesized to be most important in explaining recent changes in energy flow patterns are:
- allochthonous particulate and dissolved organic carbon inputs;
- carbon fixation through benthic primary production, phytoplanktonic primary production and, increasingly, microbial food web production;
- particulate detrital carbon production (dreissenid feces and pseudofeces; feces from other zoobenthos and zooplankton) - sedimentation processes, resuspension processes or sublittoral-to-profundal particulate transport ('nearshore shunt' of Smith et al. 2000);
During an investigators meeting in Windsor, ON (November 9, 2002), it was determined that the largest gap in knowledge was better estimates of dreissenid population abundance. It was determined that distribution and biomass of dreissenids was the most limiting information for modeling the impact of dreissenids on the Lake Erie ecosystem. We hope to partially fill this gap through our modeling and field activities.
2006 Plans
Ecological models will be developed from both theoretical and phenomenological approaches to make ecosystem forecasts. The theoretical approach is based on established theories for a process or mechanism while phenomenological predictions are based on curve fitting (Carpenter 2002). The focus of my research will be on the impact of exotic species to ecosystem measures of primary and secondary production. It has been well established that chlorophyll, a measure of phytoplankton biomass, and phosphorus are correlated (Schindler 1977). It was also found that the relationship could be further defined by food web structure (Brooks and Dodson 1965, Shapiro et al. 1975). In recent years the filtering capacity of dreissenids has been implicated in a decoupling of phosphorus-chlorophyll relationship (Mellina et al. 1995, Nicholls et al. 1999). Another component of the research will be to determine how best to combine slow and fast processes, e.g. the fast kinetics of phosphorus uptake versus the influence of land use on watershed phosphorus inputs.
APPROACH
As an initial step to developing ecological models based on phenomenological measurements, I propose to collect, organize, and analyze (statistical and pattern recognition techniques) historical data collected by the US EPA GLNPO and EC monitoring data collected in Lake Erie over the last 30 years. These data were collected from the open waters of Lake Erie and all the tributaries draining into the lake. Data recovery is not completed, much of the more current monitoring data still resides at EPA and EC. The files that are currently at GLERL span the years from 1963 to 1993 and include over 200 different physical, biological, and chemical parameters. One of the first tasks will be to obtain more current monitoring data.
Another important task will be to organize the data to allow data analysis
and synthesis. The shear size and variability in the measurements will
require the help of a computer programmer to organize the data. For example,
there are over 63,000 DO measurements collected in the open waters of
Lake Erie between 1963 and 1993. These measurements were taken from over
15,300 different geographical locations and 35,900 different time periods.
Some binning of data measurements into spatial and temporal intervals
will be useful.
2005 Progress
The filtering and input of nutrients by dreissenid mussels to ecosystem measures of primary and secondary production in the central basin of Lake Erie are a major forcing function to the lower food web production and ultimately fish production. To assist in our assessment, we are creating a data repository of limnological data from the Environmental Protection Agency (EPA) and Environmental Canada (EC) The organization and analysis of the historical data collected by the US EPA GLNPO and EC monitoring data collected in Lake Erie over the last 30 years has began. The data include over 63,000 DO measurements collected in the open waters of Lake Erie between 1963 and 1993. These measurements were taken from over 15,300 different geographical locations and 35,900 different time periods. Data are being organized into web base data files that will be accessible to all IFYLE scientists.
2004 Progress
Bioenergetic and filtering models for determination of the flux of phytoplankton filtered by dreissenids in the Lake Erie ecosystem are dependent upon accurate estimates of dreissenid biomass. In 2004, 285 sites were sampled for dreissenids by collaborators of the Lake Erie Millennium Project. At each site, depth, water temperature, conductivity, DO, pH, oxidation reduction potential (mV), and sediment characteristics were measured. In the laboratory, the abundance and lengths of zebra and quagga mussels were measured. Weights were calculated from length-weights regressions. At present, all limnological data has been distributed to the Millennium collaborators and 260 benthic samples have been counted and mussels measured. The remaining samples will be completed by October 2006. Hans Biberhofer, EC, has begun to create sediment distribution maps from his 2002 and 2003 Rox Ann surveys.
Past Accomplishments
Between 2002 and 2003, ponar grab samples were collected at 45 sites in Lake Erie by co-investigators of the Lake Erie Millennium Project and from Don Schlesher, USGS (see Nalepa Proposal). Their study will provide length/weights, age, and live/dead estimates for each of the 45 sites. In 2002, Hans Biberhofer used the Rox Ann System to create a sediment map of western Lake Erie. In 2004, we will be collecting video and acoustic data with a Questor Tangent Sediment system and the video cam at the 45 sites to improve the spatial coverage of mussel distribution and to verify the mapping information provided by Hans. Acoustic and video data will be processed and interpreted by a summer fellow.
The mussel bioenergetic model was developed by Schneider (1992) and modified by Madenjian (1995). Since quagga mussels have completely replaced zebra mussels in Lake Erie, the bioenergetic parameters of Schneider and Madenjian will need to be updated. Density estimates of dreissenids will be obtained from our current work, the work of co-investigators on the Tropic Status of Lake Erie, and from the literature. Biomass estimates will be obtained from Nalepa (see above). Model runs will provide new phytoplankton consumption rates of mussels and will be compared to estimates made by Madenjian (1995). As sediment maps and mussel biomass estimates become available, we will extend our modeling to the central and eastern basins of Lake Erie.
References
Brooks, J.L. and S.I. Dodson (1965). Body size and composition of plankton. Science 150: 28-35.
Carpenter, S.R. 2002. Ecological futures: building an ecology of the long now. Ecology 83: 2069-2083.
Madenjian, C.P. 1995. Removal of algae by the zebra mussel (Dreissena polymorpha) population in western Lake Erie: a bioenergetics approach. Can. J. Fish. Aquat. Sci. 52: 381-390.
MacIsaac, H.J., WG. Sprules, O.E. Johannsson, and J.H. Leach. 1992. Filtering impacts of larval and sessile zebra mussels (Dreissena polymorpha) in western Lake Erie. Oecolgia 92: 30-39.
Mellina, E. and J.B. Rasmussen (1994). "Patterns in the distribution and abundance of zebra mussel (Dreissena polymorpha) in rivers and lakes in relation to substrate and other physicochemical factors." Can. J. Fish. Aquat. Sci. 51: 1024-1036.
Nicholls, K.H., G.J. Hopkins, and Standke, S.J. (1999). "Reduced chlorophyll to phosphorus ratios in nearshore Great Lakes waters coincide with the establishment of dreissenid mussels." Can. J. Fish. Aquat. Sci. 56: 153-161.
Schindler, D. E., S. R. Carpenter, K. L. Cottingham, X. He, J. R. Hodgson, J. F. Kitchell, and P. A. Soranno. 1995. Food web structure and littoral zone coupling to pelagic trophic cascades. Pages 96-105 in G. A. Polis and K. O. Winemiller, editors. Food webs: integration of pattern and dynamics. Chapman and Hall, New York, New York, USA.
Shapiro, J., V. Lamarra, and M. Lynch. 1975. Biomanipulation: an ecosystem approach to lake restoration. Pp. 85-96 in P. L. Brezonik and J. L. Fox, editors. Water Quality Management through Biological Control. University of Florida, Gainesville, Florida, USA.
Smith, R.E.H., D.R. Barton, S. Guildford, R. Hecky and W.D. Taylor. 2000. Implications of Dreissena for nutrient management in lakes. Research proposal submitted to N.S.E.R.C. Strategic Grants Program.
Last updated: 2006-07-17 mbl