The following abstracts were selected from presentations made at the 11th annual meeting of the St. Croix River Research Rendezvous. The meeting was held on October 19, 1999 at Marine on the St. Croix, Minnesota and sponsored by the Science Museum of Minnesota. All abstracts presented at the meeting may be viewed on the Web at http://www.smm.org/information_zone/research/SCWRS/Rendezvous.html.

TAXONOMIC IDENTIFICATION OF FRESHWATER MUSSELS OF THE ST. CROIX RIVER THROUGH DNA ANALYSIS

Megan Albert, Cynthia Harrison, James G. Straka, Mark Hove and Daniel Hornbach, Departments of Biology and Chemistry, Macalester College, St. Paul, MN 55105

Freshwater mussels are an important component of freshwater ecosystems, storing energy that otherwise would be lost downstream, while serving as good ecological indicators and food sources for other organisms. They are a highly diverse family of organisms that are rapidly declining in species richness and abundance. Mussels undergo a period of parasitic encystment on fish hosts during the larval (glochidial) stage of their life cycle. A better understanding of host- parasite relationships would be highly beneficial to mussel conservation; however, mussels in the glochidial stage are very small and therefore extremely difficult to identify. In this project, we use the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) techniques on the ITS-1 region of the mussel genome in an attempt to identify genetic markers for each species. To do this, genomic DNA is extracted from adult mussel specimens, the ITS-1 region is amplified using PCR and the amplified DNA digested with a selected array of restriction enzymes. Our goal is to create an identification key based on these genetic markers for all the mussel species of the St. Croix River. The resulting taxonomic key may be used to unambiguously identify mussels while in their glochidial forms. To date, DNA patterns have been recorded for 22 mussel species. Currently, we are working on expanding this database, and refining our protocols to make identification more accurate and efficient. Our data thus far suggests that the mussel species of the St. Croix River can indeed be distinguished using this technique, and that these methods may serve as a valuable tool for mussel conservationists.

Preserving the Biodiversity of Unionid Mussels in the St. Croix River by Development of In Situ Refugia

Michelle R. Bartsch¹, Diane L. Waller¹, Gregory Cope², Heidi L. Dunn³, Sue Jennings⁴, and Ronald G. Rada⁵. ¹U.S. Geological Survey, Upper Midwest Environmental Sciences Center; ²Department of Toxicology, North Carolina State University; ³ Ecological Specialists, Inc. St. Peters, Missouri; ⁴National Park Service, Big South Fork NRRA; ⁵River Studies Center, University of Wisconsin-La Crosse.

Relocation of native mussels to refugia has been considered as a potential mechanism for protecting unionid populations at risk from colonization by the zebra mussel Dreissena polymorpha. Types of refugia that have been proposed include relocating mussels to man-made ponds or to fish hatcheries. The use of system-specific, in situ refugia, offers several advantages over other types of refugia because of the similarity of water quality, substrate characteristics, and the availability of necessary fish hosts. Moreover, in situ refugia allow the retention of genetic diversity of the mussel and host fish populations in the system. In 1996, we relocated 450 unionid mussels into system-specific, in situ refugia in the National Park Service managed zone of the St. Croix River, in Minnesota and Wisconsin. The purpose of our project was to refine protocols for relocating mussels and to serve as a conservation measure for protecting the mussel fauna of the St. Croix from zebra mussel infestation. Two species of unionids representing the subfamily Ambleminae (Pimpleback, Quadrula pustulosa and Spike, (Elliptio dilatata) and one representing the subfamily Lampsilinae (Higgins' Eye Pearly mussel, Lampsilis higginsi) were collected from the lower St. Croix River near Lakeland, Minnesota, and relocated to three 5 x 5 m study grids, two in the experimental refuge 40 miles upstream, near Franconia, Minnesota, and one at Lakeland, Minnesota, which served as a source-site control. Mussel survival, recovery, and substrate characteristics were evaluated annually at each of the sites for two years. Recovery of all three species at the sites ranged from 90 to 98% in 1997 and from 81 to 100% in 1998. The survival of recaptured mussels ranged from 85 to 100% in 1997 and from 93 to 100% in 1998. Among the three species, the lowest recovery (81%) and survival (93%) occurred with E. dilatata at the reference site in 1998 and was due to sedimentation of sand that had deposited over several of the randomly selected placement cells in the grid where E. dilatata was placed. The textural characteristics (cobble-gravel and sand fractions) of the substrate differed significantly (ANOVA, p < 0.01) between the reference site and the two refuge sites at the beginning of the study, and did not differ from this initial status among subsequent years. The relatively high survival and recovery of mussels during this study demonstrates the importance of proper handling and transport protocols when relocating mussels and the selection of suitable relocation habitat with stable substrate. If established correctly, the use of system-specific, in situ refugia is a viable tool for preserving the biodiversity of unionid mussels.

SUGGESTED READING:

Cope, W. G. and D. L. Waller. 1995. Evaluation of freshwater mussel relocation as a conservation and management strategy. Regulated Rivers: Research & Management. 11:147-155.

The Efficacy of Mussel Relocation as a Resource Management Tool:

An Experiment in the St. Croix River

Leda A. Cunningham, Daniel J. Hornbach, Mark C. Hove

Macalester College, Biology Department, 1600 Grand Avenue, Saint Paul, MN 55105

Increasing threats to the native mussel community in the St. Croix River (e.g. bridge construction, zebra mussel outbreaks) make it necessary to study the efficacy of relocating mussels to less-threatened parts of the river. To determine the effects of relocation on mussel growth and survival a three-year in situ experiment was conducted at Wild River State Park, Minnesota. In 1997 a 25 m² study grid containing 25 cells was placed near the confluence of the St. Croix and Sunrise rivers (reference site), and another was placed at the eastern boat launch at Wild River State Park (relocation site). Each cell was randomly assigned one of the following treatments: (1) double resident mussel density, (2) addition of 10 pimplebacks, (3) addition of 10 spikes, (4) addition of 10 pocketbooks, and (5) control (no manipulation occurred during the first year). In 1997 mussels were collected from the reference site, placed into study grids, and individuals from the first four treatments were measured, weighed, and marked. In 1998 and 1999 mussels were measured and weighed. Those found without a number were recorded as "new" and marked, those missing from the 1998 census were logged as "missing", and the rest were logged as "recovered", "control", or "dead" as applicable to their status. Preliminary examination of data indicates no difference in growth or mortality between treatments. Mortality was low (5 %) compared to similar studies (Cope and Waller 1995). Results suggest that relocating mussels to similar habitats may be an effective strategy for conserving mussel populations living in potentially harmful parts of the St. Croix River.

Funding provided by the Minnesota Legislative Commission on Minnesota Resources.

Suggested Reading:

Cope, W.G. and D.L. Waller. 1995. An evaluation of freshwater mussel relocation as a conservation and management strategy. Regulated Rivers: Research and Management 11: 147-155.

A 1998 Unionid Mollusk Translocation, Lake Mallalieu/Williow River Dam, St. Croix River Mile 17.9, Between Hudson/North Hudson, Wisconsin

Marian E. Havlik Malacological Consultants, La Crosse, WI.

Lake Mallalieu dam, at the mouth of the Willow River, St. Croix River Mile 17.9, between Hudson/North Hudson, WI, is being rehabilitated. A scour hole below the dam, 30.5m X 30.5m, was to be filled. This site, including a 6 m buffer zone on 3 sides, was 36.58 m out into the channel and 42.67 m long (1561 m2). A mussel survey was done 22 September 1998. 5-0.25 m² quadrats were sampled on each of 6 transects below the dam, perpendicular to the St. Croix flow. 30 samples yielded a live mean mussel density of 0.53 mussels/m². One Dreissena polymorpha (Pallas 1771), 25 mm long, 3-4 yrs of age, was attached to an anchor-line caught on a submerged tree. This D. polymorpha was probably brought into the area in 1998, attached to the anchor line, judging by the condition of the anchor and rope. Although there were very low densities, one living federally endangered Lampsilis higginsi (Lea 1857) was found on the first random survey dive, within 6 m of the shoreline, near the southern limits of the project site. This male, 93 mm L, 63 mm H, and 9-10 yrs of age, was marked 550 on the lower anterior edge of both valves. All living unionids were returned to the St. Croix, 65 m upstream from the dam. Divers reported more mussels at Translocation Site 1, than at the dam, apparently because of more suitable substrata. After federal consultation, translocation, all mussels (15 species including another L. higginsi, #650, 105 mm L, 70 mm H, 20 yrs old, probably a sterile female), were moved to Translocation Site 2, a gravel bar 25-30 m offshore, 2-3 m deep, St. Croix River Mile 18.0, 22-25 October 1998. Amblema p. plicata (Say 1817) was 36.6%, Potamilus alatus (Say 1817) 23.3%, and Pyganodon grandis corpulenta (Cooper 1834) was 17.1% of the fauna, an unusual species distribution. One WI special status mussel was found at Translocation Site 2, Pleurobema sintoxia (Raf. 1820) (34 mm long, 30 mm high, 10 yrs old). Two species were represented by empty shells. A Necturus m. maculosus (Rafinesque 1818) from the dam-face substrata was photographed. After discussion regarding construction techniques, we also moved mussels from Translocation Site 1, because the site was too close to the project area. Water temperatures were 53-56 °F. One year follow-up was done August 1999. WI DNR divers recovered L. higginsi #650, and about 20 hash-marked unionids (100% survival). In 1999 2 unmarked L. higginsi were found within 3 m of Translocation Site 2 confirming a very suitable substrata of sand and gravel.

SUGGESTED READING:

Fuller, S. L. H. 1978. Fresh-water mussels (Mollusca: Bivalvia: Unionidae) of the Upper Mississippi River: Observations at selected sites within the 9-foot channel navigation project on behalf of the United States Army Corps of Engineers. Academy of Natural Sciences, Philadelphia, PA. 401 pp.

Dawley, C. 1947. Distribution of aquatic mollusks in Minnesota. American Midland Naturalist 38:671-697.

LONG TERM CHANGES IN MUSSEL POPULATIONS OF THE ST. CROIX RIVER

Thomas W. Hermanson, Leda A. Cunningham, Katie G. Esse, Jensen C. Hegg, Mark C. Hove, Jennifer L. Mann, and Daniel J. Hornbach

Macalester College, Biology Department, 1600 Grand Avenue, St. Paul, Minnesota 55105

Population dynamics of freshwater mussels (Unionidae) were observed since 1991 at three locations in the St. Croix River. Mussel communities were assessed quantitatively and qualitatively to calculate density, species richness, and age structure to identify long-term trends. Mussels and substrate were collected from at least 100 0.25 m² quadrats at each location. Substrate was separated into 5 size classes and all mussels were identified and measured. From these measurements, population density and community diversity were calculated at each location and compared to past sampling years. At Franconia mussel density decreased from 10.44 mussels/m² in 1991 to 9.76 mussels/m² in 1995, and 4.52 mussels/m² in 1999. Species richness decreased from 26 species in 1991 to 19 species in 1995, and 15 species in 1999. One endangered winged mapleleaf mussel was found in quantitative samples in 1995. At Wild River State Park, mussel density decreased from 37.36 mussels/m² in 1993 to 29.56 mussels/m² in 1996 continuing to decline to 21.08 mussels/m² in 1999. Species richness decreased from 21 species in 1993 to 18 species in 1996, and remained the same in 1999. At Prescott, Wisconsin mussel density decreased from 7.8 mussels/m² in 1994 to 5.64 mussels/m² in 1999, while species richness declined from 21 to 18 species. One Higgins’ Eye (Lampsilis higginsi) was found in both 1994 and 1999. In addition we found two invasive bivalve species at Prescott: one live zebra mussel attached to an threeridge (Amblema plicata) as well as one Asian clam (Corbicula fluminea.). We will statistically analyze these data to determine if these trends are significant and warrant management action.

RANGE EXTENSION OF THE FEDERALLY ENDANGERED WINGED MAPLELEAF MUSSEL: SHELLS COLLECTED FROM THE UPPER ST. CROIX RIVER

Mark C. Hove, Leda A. Cunningham, Katie G. Esse, and Daniel J. Hornbach

Macalester College, Biology Department, 1600 Grand Avenue, St. Paul, MN 55105

Work conducted this summer extends the range of the winged mapleleaf to the upper St. Croix River. The historic distribution of the species ranged throughout the upper Mississippi River basin including 34 rivers across 12 states. Since the 1920’s the community has declined drastically to where now only two small populations are known, one in the Ouachita River, Arkansas, and the last known reproducing population in the lower St. Croix River. Prior to this summer the winged mapleleaf had only been observed in the lower St. Croix River (the reach downstream of the falls). This summer three winged mapleleaf shells were collected at Wild River State Park, Minnesota. Two of the valves are worn and old, the other valve is less eroded and may have been deposited more recently. Ten sites were surveyed for live winged mapleleaf 1 mile upstream and downstream of the western Wild River State Park boat launch but none were observed. The mussel community at Wild River State Park is diverse and robust. It is difficult to ascertain the cause(s) for the status of winged mapleleaf in this portion of the river. Some thought should be given to the suitability of this habitat if it is to be considered as a relocation site for winged mapleleaf should zebra mussels threaten the population in lower reach of the river.

Suggested reading:

Effects of Ammonia on Unionid Mussels: A Threat to their Biodiversity in the St. Croix National Sceninc Riverway

Teresa J. Naimo, William B. Richardson, Michelle R. Bartsch, and Bradley E. Frazier.

U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin.

The St. Croix River basin (SACN) is experiencing rapid land-use changes--from forest and agriculture to suburbanization--as the metropolitan area of Minneapolis-St. Paul expands. Although the upper reaches of the St. Croix and the Namekagon rivers contain surface waters of high quality, threats to water and sediment quality have accelerated in recent years. These threats include agricultural runoff, urban development, and toxic contaminants from one of the 15 point-source discharges in the SACN. The National Park Service is concerned that increased urbanization will also increase the output of nutrient-laden effluent from wastewater treatment plants, as well as other point and non-point source discharges, into the St. Croix River. One potential result of this urbanization may be an elevation of ammonia in sediment porewater. At alkaline pH, ammonia dissociates from organic molecules into un-ionized ammonia which is quite toxic to benthic organisms. The SACN contains an extremely rich fauna of unionid mussels–animals sensitive to changes in habitat quality--and increased sedimentary ammonia may pose a significant threat to this fauna. Our objectives are: (1) to describe the density and species richness of the molluscan community at selected sites along a eutrophication gradient in the SACN; (2) to examine the in situ effects of ammonia enrichment on the survival and growth of juvenile unionids in the SACN; and (3) to determine the tolerance thresholds for total ammonia nitrogen in juvenile unionids in laboratory sediment toxicity tests. In August 1999, we conducted preliminary sampling for sedimentary ammonia at 28 sites in the basin (River Miles 0 to 94), including sites on three tributaries (Snake, Sunrise, and Apple rivers) to define the range of ammonia concentrations in the basin and to assist with selection of study sites. Total ammonia nitrogen (TAN) ranged from 0.3 to 19.0 mg/L and un-ionized ammonia (NH³) ranged from 2.5 to 141.5 ug/L. Highest concentrations were observed in the South Branch of the Sunrise River, with a mean of 12.3 mg TAN/L and 84.7 ug NH³/L‹levels approaching those shown to be toxic to molluscs in laboratory tests. Furthermore, concentrations of sedimentary ammonia generally increased as river miles decreased‹paralleling spatial patterns in nutrients in the water column. We intend to use this presentation to solicit input from our colleagues on potential study sites and experimental design options.