1
Prepared in cooperation with The Nature Conservancy and Sullivan County Division of Planning and Environmental Management
Relations of Environmental Factors with Mussel-Species Richness in the Neversink River, New York
Significant Findings
• A 6-year study of mussel communities and their habitat in the Neversink River basin in southeastern New York found that the principal factors apparently affecting mussel-species richness were site (reach) elevation, drainage-area size, channel width, bottom- material composition, water velocity, shear stress at bankfull discharge, and water quality (acid- neutralizing capacity (ANC) and concentrations of calcium, phosphorus, and sulfate). Together these 10 factors explained as much as 94 percent of the variability in mussel-species richness across the watershed. Swollen wedgemussel (Alasmidonta varicosa) from the Neversink River. • The number of species in mussel communities throughout the basin typically increases in a downstream progression from zero or one species in upstream sites to as many as six species in downstream sites. • A recently removed dam in the lower part of the river may have confined populations of two rare mussel species to lower reaches of the Neversink River; its removal in 2004 could allow those species to populate additional reaches in the upper basin.
U.S. Department of the Interior Printed on recycled paper Open-File Report 2007–1283 U.S. Geological Survey March 2008 2 Introduction flow patterns have recently been (richness) were quantified through 2-hour proposed by TNC and could benefit snorkeling searches at 28 sites during the Declines in the distribution, the established mussel populations summer of 1997; of these, 17 were on abundance, and diversity of freshwater- and aquatic communities. The ability the main stem and 11 were on tributaries. mussel species (family Unionidae1) have to protect mussel populations and the Habitat and hydraulic features at each been reported worldwide (Bogan, 1993; potential to increase mussel richness study site were measured using point- Strayer and Jirka, 1997). The principal in the Neversink River is unknown, and-transect methods modified slightly causes of the observed declines are however, because the environmental from those presented in Meador and difficult to confirm, however, because factors that affect the seven mussel others (1993). Water depth, substrate only a few of the many factors that affect species are poorly defined, and the types, and water velocity were measured mussel-species populations have been distribution of mussel beds is patchy and at five to seven equally spaced points identified (Strayer and Ralley, 1993; thus difficult to quantify. across each transect and at the thalweg, Strayer, 1999; Baldigo and others, 2003; In 1997, the U.S. Geological and bank and riparian characteristics Strayer and others, 2006). Survey, in cooperation with TNC, began were measured or visually estimated at The Neversink River, which a 6-year study along the Neversink both ends of each transect. Water samples drains the Catskill Mountains in River and its tributaries to (1) document were collected at the same time from southeastern New York (fig. 1), contains the current distribution of each mussel single samples collected under base-flow seven species of mussels (Strayer and species, (2) assess environmental factors conditions and analyzed for acid- Ralley, 1991; Strayer and Jirka, 1997). in relation to mussel-species richness neutralizing capacity, and concentrations Populations of the endangered dwarf and distribution, and (3) identify the of calcium, phosphorus, sulfate, and 13 wedgemussel (Alasmidonta heterodon) factors that most strongly affect mussel other constituents. and the threatened swollen wedgemussel populations and develop an equation Mussel-transect surveys were done (Alasmidonta varicosa) coexist with other that relates environmental factors to in 2001 and 2002 at the 28 sites studied unionid mussels in the Neversink River mussel-species richness. This report during 1997 and at 4 additional main- (Strayer and Ralley, 1991, 1993; Baldigo (a) summarizes the methods used to stem sites. These surveys counted the and others, 2003). Dwarf wedgemussel quantify or qualify environmental number of each mussel species through populations had previously been found factors and mussel-species distribution snorkel surveys, measured wetted- only downstream from the site of an and abundance, (b) presents a list channel widths and water velocities, abandoned dam in the lower part of the of environmental factors that were documented the bankfull indicators, river at Cuddebackville (fig. 1), and correlated with mussel-species richness, and estimated bankfull width, depth, swollen wedgemussels were only found and (c) offers an empirical model to and cross-sectional area within three in the lower and middle reaches of the predict richness of mussel species bank-to-bank transects across each river. The limited distribution of these in benthic communities throughout study site. Channel-slope measurements two species suggests that they may be the basin. from longitudinal bed-elevation surveys susceptible to local extinctions. were used with bankfull dimensions The distribution of mussel to calculate mean water velocities and populations can be limited by shear stresses for each transect at high impoundments. Mussel larvae develop Methods bankfull-discharge stages for 21 of the in species-specific host fish; thus, 32 study sites. Surveys were conducted during impoundments that restrict passage of The relations between mussel- the summers of 1997–2002 on the these host fish also restrict the extent species richness and water chemistry, Neversink River and its tributaries to of mussels. The Neversink River is habitat features, bankfull-channel document mussel communities, water impounded by the Neversink Reservoir geometry, and basin characteristics (such quality, habitat characteristics, and [241 square kilometers (km2)], a as elevation and size of drainage area) bankfull discharge and geomorphology major source of drinking water for were assessed through simple, multiple, at 28 sites ranging in length from the City of New York, and was also and quantile regression analyses. Ten 100 meters (m) (for habitat assessments) impounded 50 km downstream by the variables (site elevation, drainage-area to 600 m (for geomorphology surveys). Cuddebackville Dam until 2004, when size, mean channel width, amount of sand Habitat characteristics and bankfull the latter was removed by The Nature as a percentage of streambed material, discharge were measured at least once Conservancy (TNC) and the U.S. Army water velocity, shear stress, ANC, and at all sites, whereas complete bankfull Corps of Engineers to improve fish concentrations of calcium, phosphorus, geomorphology surveys were done passage. The removal of this dam has and sulfate) were identified as important provided previously unavailable habitat at only 21 main-stem sites. Sampling to mussel-species richness. The number for diadromous and other fish species methods for each environmental factor of data points used to assess the relations that act as hosts for rare mussel species. and mussel community are summarized of mussel-species richness with each of In addition, releases from the Neversink below and provided in greater detail by the ten factors typically varied between Reservoir that mimic the river’s original Baldigo and others (2002, 2003). 21 and 32 because of the different The number of each mussel species number of sites sampled for each survey 1 Words in boldface are explained in the glossary collected per hour (relative abundance) and ranged as high as 41 when transect on page 6. and the number of mussel species data from 21 sites were used to assess 3
er NY VT k Riv ersin r ev Rive N ink h s Catskill State Park nc ever ra h N MA t B nc Neversink Basin es ra W B st PA CT Ea 74°25' 41°55'0"N nv17 41°55' NJ nv16 nv12 74°45' nv15 41°52'30" nv14 Neversink nv13 Reservoir
tr11 nv11
nv10
tr10 nv09
tr09 nv08 r
ve tr07
i tr05 R tr08
k n i s tr06
er 74°45' v
Ne nv07 41°32'30"
tr04 tr02 41°30' tr03 74°22'30" nv06 Cuddebackville Dam nv05
r e v nv04 i R tr01 k nv03 in rs ve Ne nv02
nv01 0 2 4 6 8 10 MILES 0 2 4 6 8 10 KILOMETERS
Base from U.S. Geological Survey digital data, 1:100,000, 1983, Universal Transverse Mercator Projection, Zone 18 Mussel species (picture at site indicates presence of species) EXPLANATION Dwarf wedgemussel (Alasmidonta heterodon) Sample site Alewife floater (Anodonta implicata) Triangle floater (Alasmidonta undulata) nv Neversink River reach Swollen wedgemussel (Alasmidonta varicosa) tr Tributary to the Neversink River Creeper (Strophitus undulatus) Absence of mussel-species bar Eastern elliptio (Elliptio complanata) indicates no mussels found. Eastern floater (Pyganodon cataracta)
Figure 1. Location and number of mussel species collected during mussel surveys at 28 sites of the Neversink River basin in southeast New York, June–August 1997. 4
Biologists conducting timed snorkel surveys for mussels in the Neversink River.
relations with velocity and shear stress. no mussels were found in 7 of the 11 located between the Cuddebackville Dam Separate equations describing the tributaries, nor in the 5 most upstream and site nv10 (fig. 1). maximum species richness, as a function of the 17 main-stem sites (fig. 1). The Relative-abundance data indicate of each variable, were standardized to most widely distributed species in the that the eastern elliptio was the most maximum values of 1. Averaged together, basin was the eastern elliptio (Elliptio abundant mussel species at nearly all these metrics form an unweighted complanata), which is tolerant of a study sites (fig. 2). Relative abundance index capable of predicting mussel- wide range of environmental conditions increased downstream and was generally species richness from similar data and habitat disturbances (Strayer and greatest at main-stem sites in the lower collected at other sites throughout the Jirka, 1997). It was the only species at basin; the primary exception to this Neversink River. several middle-basin sites and at the trend was at site nv01, where only one lowest site (nv01, fig. 1). In contrast, species (eastern elliptio) was present in the dwarf wedgemussel (Alasmidonta low numbers. The eastern elliptio was heterodon) and the alewife floater moderately common at the other sites, but Mussel-Species (Anodonta implicata) were found only the swollen wedgemussel (Alasmidonta Distributions and downstream from the Cuddebackville varicosa), the creeper (Strophitus Dam; their sparse distribution indicates undulatus), and the triangle floater Abundance that both species either are intolerant of (Alasmidonta undulata) were uncommon local environmental conditions, or are or absent at most sites in the middle and The number of mussel species varied restricted by the inability of host-fish upper basins. No dwarf wedgemussels widely at sites surveyed in the Neversink species to migrate upstream past the or alewife floaters were found at River. Species richness was greatest in Cuddebackville Dam. Two to four mussel study sites located upstream from the main-stem reaches in the lower basin; species were found at all main-stem sites Cuddebackville Dam. 5
er k Riv VT ersin er NY v k Riv Ne sin ch ever an N Catskill State Park Br ch st an MA We Br Neversink Basin Neversink st Ea nv17 74°25' CT Reservoir 41°55' PA nv16 NJ nv12 74°45' nv15 41°52'30" (1) nv11 nv10 nv14 (1) nv13 tr11 (43) (0.06) nv09
tr10 nv08 (22.3) tr09 (6) nv07
(19.5)
r
e v
tr08 i tr07
R tr05
nk i
s
ever N tr06 nv06 74°45' (56) 41°32'30" tr02 (42) tr04 Cuddebackville 41°30' nv05 (30) Dam tr03 74°22'30"
nv04
r (50) e iv nv03 (34.9) tr01 R
k in rs (10.3) ve Ne nv02 nv01
(4)
Base from U.S. Geological Survey digital data, 1:100,000, 1983, Universal Transverse Mercator Projection, Zone 18 (86.9) 0 2 4 6 8 10 MILES (71) 0 2 4 6 8 10 KILOMETERS EXPLANATION Sample site Mussel species nv Neversink River reach Dwarf wedgemussel (Alasmidonta heterodon) Creeper (Strophitus undulatus) tr Tributary to the Neversink River Mussel-species distribution– Alewife floater (Anodonta implicata) Eastern elliptio (Elliptio complanata) absence of “pie” indicates no mussels found. Triangle floater (Alasmidonta undulata) Eastern floater (Pyganodon cataracta) Number of mussels collected per hour (30) Swollen wedgemussel (Alasmidonta varicosa)
Figure 2. Relative abundance of each of seven mussel species and the total number of mussels collected per hour, at 28 sites of the Neversink River basin in southeast New York, June–August 1997. (Modified from Baldigo and others, 2002.) 6 Effect of Environmental • the amount of sand was between 10 and the absence of strong individual and 17 percent of streambed material; and linear relations indicate that many factors influence species richness; this Factors • site elevations were less than 350 meters; further implies that no single variable Mussel-species richness was can be used to model richness of mussel found to be strongly correlated with • sulfate concentrations were between species in the Neversink River basin and 10 environmental and geomorphologic 5.4 and 8.0 milligrams per liter; and probably in other basins. factors, though rarely in a linear fashion • total phosphorus concentrations were In an effort to measure model (fig. 3). In general, mussel-species between 16 and 24 milligrams per liter. precision, the 10 variables were used to richness was highest where: estimate species richness for each site and Many environmental factors, both • water velocities were between 0.4 and compare to the observed richness. The measured and unmeasured, appear to 1.0 meter per second (fig. 3A); affect mussel-species populations and richness index explained 76 percent of • shear stresses were less than 0.5 pound community richness to different degrees the variability in mussel-species richness per square foot (fig. 3B); in the Neversink River. Species richness at all Neversink River and tributary sites and metric scores generally decreased and generally predicted richness to within • calcium concentrations were between to zero at the highest and (or) lowest 1 species (fig. 4A). Anomalous local 0.75 and 0.9 milligram per liter values of each variable (fig. 3). The conditions resulted in overprediction of (fig. 3C); 95-percent quantiles for water velocity richness at one small headwater tributary • ANC was between 1.0 and and bankfull shear stress produced the below a highland marsh (site tr02) and 1.2 microequivalents per liter; strongest correlations (fig. 3A and 3B) underprediction of richness at site nv01, and suggest that water velocity and shear just upstream from the mouth of the • drainage areas were larger than stress have an important effect on the Neversink River (fig. 4A). The richness 600 square kilometers; distributions of most mussel species in index explained 94 percent of the • mean channel widths averaged more the Neversink River. The spread of data variability in species richness when only
than 35 meters (log10 1.5) (fig. 3D); points below each regression line (fig. 3) main-stem sites were evaluated (fig. 4B).
A B
4 1.0 4 1.0
3 3
2 0.5 2 0.5
1 1
0 0 0 0 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 WATER VELOCITY, SHEAR STRESS, IN METERS PER SECOND IN POUNDS PER SQUARE FOOT C D
6 1.0 6 1.0 METRIC SCORE
4 4 NUMBER OF SPECIES PER TRANSECT 0.5 0.5
2 2
0 0 0 0 0 0.2 0.4 0.6 0.8 1 1.2 0 0.5 1 1.5 2 LOG CALCIUM CONCENTRATION, LOG MEAN CHANNEL WIDTH, IN MILLIGRAMS PER LITER IN METERS
Figure 3. Relations between mussel-species richness at selected sites in the Neversink River basin and four predictor variables chosen to show the diversity of relations between richness and environmental condition: (A) bankfull water velocity, (B) bankfull shear stress, (C) alcium concentration, and (D) mean channel width. 7
These results provide empirical A 7 evidence that the 10 variables used in the All main-stem and tributary sites richness index have an important effect 6 R² = 0.76 on mussel-species richness and mussel 5 distributions in the Neversink River 4 basin. Though the index described herein is specific to the Neversink River, these 3 same factors could have comparable 2 relations with mussel species in other 1 nearby systems. Such relations are critical 0 to managing watersheds as they provide B one method to model the potential effects 7 that changing climatic and environmental Main-stem sites (except nv01) 6 conditions may have on endangered R² = 0.94 mussels and other sensitive benthic 5 invertebrates inhabiting riverine systems. 4 Figure 4. Relations between
OBSERVED SPECIES RICHNESS observed mussel-species 3 richness and the richness index 2 in the Neversink River basin, Conclusions 1 1997–2002, at (A) all main-stem 0 and tributary sites and (B) main- The Cuddebackville Dam may have 0 0.2 0.4 0.6 0.8 1 stem sites only (except nv01). restricted dwarf wedgemussel and alewife RICHNESS INDEX floater populations to the lower sites of the river. The removal of the dam in 2004 potentially could increase mussel diversity upstream of the former dam site by permitting passage of host-fish species carrying larval stages of one or more References Cited mussel species. At least 10 environmental factors Baldigo, B.P., Riva-Murray, K.R., and Schuler, G.E., 2003, Effects of environmental appeared to affect richness of mussel and spatial features on mussel populations and communities in a North American communities. The factors that were river: Walkerana, v. 14, no. 31, p. 1–32. most strongly correlated with maximum species richness were water velocity and Baldigo, B.P., Schuler, G.E., and Riva-Murray, K.R., 2002, Mussel community shear stress at bankfull flow. composition in relation to macrohabitat, water quality, and impoundments in the A richness index was developed that Neversink River, New York: U.S. Geological Survey Open-File Report 2002–104, explained 76 percent of the variability in 26 p. mussel-species richness at all Neversink River sites and 94 percent of the Bogan, A.E., 1993, Freshwater bivalve extinctions (Mollusca:Unionidae)—A search variability at main-stem sites. for causes: American Zoologist, v. 33, p. 599–609. Such models may be used to assess Meador, M.R., Hupp, C.R., Cuffney, T.F., and Gurtz, M.E., 1993, Methods for the effects that changing climatic and characterizing stream habitat as part of the National Water-Quality Assessment environmental conditions might have Program: U.S. Geological Survey Open-File Report 1993–408, 48 p. on mussel species and other benthic invertebrates of the Neversink and similar Strayer, D.L., 1999, Freshwater mollusks and water quality: Journal of the North river systems. American Benthological Society, v. 18, no. 1, p. 1. Strayer, D.L., and Jirka, K.J., 1997, The pearly mussels of New York State: Albany, N.Y., The State University of New York, 113 p. Strayer, D.L., Malcom, H.M., Bell, R.E., Carbotte, S.M., and Nitsche, F.O., 1 1 By Barry P. Baldigo , Anne G. Ernst , 2006, Using geophysical information to define benthic habitats in a large river: George E. Schuler2, and Colin D. Apse3 Freshwater Biology, v. 51, no. 1, p. 25–38.
1U.S. Geological Survey, New York State Water Strayer, D.L., and Ralley, J., 1991, The freshwater mussels (Bivalvia:Unionidea) of Science Center, 425 Jordan Rd., Troy, N.Y. 12180 the upper Delaware River drainage: American Malacological Bulletin, v. 9, no. 1, 2The Nature Conservancy, Neversink River p. 21–25. Preserve, P.O. Box 617, Cuddebackville, N.Y. 12729 Strayer, D.L., and Ralley, J., 1993, Microhabitat use by an assemblage of stream- 3The Nature Conservancy, 108 Main Street, New dwelling unionaceans (Bivalvia), including two rare species of Alasmidonta: Paltz, NY 12561 Journal of the North American Benthological Society, v. 12, no. 3, p. 247–258. 8
Glossary
B bankfull The level of water in a stream channel just below the point where the water would overflow the channel onto the flood plain. base flow The part of the stream discharge that does not include direct runoff from precipitation; it is usually sustained by ground water.
D diadromous Species that use both marine and freshwater habitats during their life cycles. These species are generally susceptible to impoundments on streams because of their migration patterns.
E endangered Species whose population is so small that it is at risk of becoming extinct. The federal government maintains a list of endangered species.
G geomorphology The study of the size and shape of river channels and the effect of For more information on the USGS--the water in controlling the channels. Federal source for science about the Earth, its natural and living resources, M natural hazards, and the environment: metric A measure of a community characteristic that summarizes data and facilitates World Wide Web: http://www.usgs.gov comparisons among sites. Telephone: 1-888-ASK-USGS R Any use of trade, product, or firm names relative abundance The number of each species of mussel collected per unit of time. is for descriptive purposes only and richness The number of species present in a given area. does not imply endorsement by the U.S. Government. richness index An index that combines data from several variables to predict the number of mussel species.
S For additional information write to: shear stress The propensity of flowing waters to mobilize bed materials. Shear stress New York Water Science Center depends on depth and velocity of the water and size of the particles. U.S. Geological Survey 425 Jordan Road T Troy, NY 12180 threatened A species that is likely to become endangered in the near future unless changes are made to improve its environment. The federal government maintains a list of Information requests: threatened species. (518) 285-5602 U or visit our Web site at: Unionidae The family of mussels that includes freshwater mussels found in the http://ny.water.usgs.gov Neversink River.