Drainage to Dragonflies:
Conservation of Aquatic Invertebrates in Rivers and Streams of Eastern Massachusetts

by Frederick H. SaintOurs
Department of Biology, University of Massachusetts Boston

Table of Contents: Introduction Aquatic Invertebrates in a Human Landscape Dragonflies in Environmental Monitoring Using Stream Invertebrates for Conservation of Aquatic Biodiversity Internet Resources References Southern Pygmy Clubtail Lanthus vernalis - F. SaintOurs, Norwell. Left: Larvae, showing two sizes found together in a single sample as evidence of semi-voltine life cycle.; Middle: Adult male.; Right: Habitat – a tiny, sand-bottomed, spring-fed creek with neutral pH. Keywords: dragonflies, damselflies, Odonata, aquatic macroinvertebrates, aquatic ecology, insect diversity, water quality monitoring, streams, Southeastern Massachusetts

Introduction

Lotic macroinvertebrates -- the insects, crustaceans, and mollusks that spend most or all of their lives in environments of running water – constitute a significant portion of aquatic diversity, as well as a major component of aquatic and terrestrial food webs (Allan 1995). These animals play a vital role in the ecology of lotic systems by processing organic matter and promoting the flow of nutrients to other life forms (Cummins 1983; Wallace and Webster 1996). Therefore, aquatic insects have long held the attention of fishermen, who have gone to great lengths to learn the timing of caddisfly, mayfly, and stonefly hatches on rivers in pursuit of predatory game fish. Plagued by the public’s intolerance of midges, blackflies, and disease-spreading mosquitoes, however, most aquatic insects have generally been regarded as pests, and either ignored or exterminated.

The aquatic animals that depend on streams and rivers are considered to be among the most threatened organisms worldwide (Allen and Flecker 1993, Saunders et al. 2002), mainly because domination of Earth’s surface by Homo sapiens has eroded the ecological integrity of the majority of our rivers and streams (Shiklomanov 1993). It has been estimated that humans already utilize half of Earth’s available freshwater runoff (Loh et al. 1998), a figure that is projected to increase to more than 60% by 2025 (Postel et al. 1996). The U.S., which ranks highest in species diversity worldwide for many groups of freshwater arthropods and mollusks (Master et al. 1998, Braun et al. 2000), now ranks as the second-most dammed country with more than 5500 dams over five feet in height (McCully 1996), and tens of thousands of smaller ones, leaving only about two percent of its flowing waters unaffected by the demands of civilization (Benke 1990).

Aquatic Invertebrates in a Human Landscape

Altered flow patterns and pollution resulting from a long history of use and neglect of natural waterways have been touted as the leading causes of extinctions and endangerment of riverine arthropods, mollusks, and fish (Richter et al. 1997, Pyle et al. 1981). Declines in freshwater biodiversity have been attributed to landscape changes associated with human activities (Klein 1979; Richards et al. 1996), particularly to in-stream habitat degradation caused by the removal of forest and the construction of roads and impoundments (Bolstad and Swank 1997; Moyle and Randall 1998; Roth et al. 1996; Trombulak and Frissell 2000; Wang et al. 1997). Unspoiled headwater streams are considered to be one of the most threatened habitats in North America for aquatic insects, especially for rare dragonflies (Bick 1983), while small, spring-fed streams are known to be unique habitats harboring a number of obligate species (Illies and Botosaneanu 1963). Today, organisms of lotic habitats (flowing water) continue to face ever-increasing threats from land development including erosion and deposition from storm water discharge, alteration of temperature and nutrient regimes from pavement and lawns, ecological disruption from small and large-scale pesticide applications, and decreased flow due to water draw-down (See Box 1: Human Impacts on Stream Fauna).

Map of North River tributary system - Data source: MassGIS; F. SaintOurs.

In addition to altering water flow and chemistry, human land use affects running-water ecosystems by altering or reducing the nutritional resources of a small stream. Unlike lakes and ponds, which depend largely on the photosynthetic production of aquatic plants, biological production in a stream is based on terrestrial sources of organic matter, mostly in the form of fallen leaves and branches. Normally, more than half of the organic matter entering a first-order stream is retained by woody debris (Anderson and Sedell 1979), where detritus and leaves are colonized and conditioned by an assortment of fungi and other microorganisms and fed upon by larger invertebrates. Natural detritus dams from fallen trees, branches and leaves, referred to as “snags”, play an integral part in the ecology of stream organisms by catching debris and providing both food and shelter for invertebrates, amphibians, and fish. Attempts to improve drainage from a human standpoint can affect stream communities by decreasing the available standing crop of detritus that normally accumulates behind obstructions in the stream channel. In summary, the composition of riparian vegetation, surrounding forest, and human constructions directly and indirectly affect water temperature and flow, habitat structure, and the characteristics of organic matter in small streams (Wallace and Merritt 1980), which in turn affect benthic invertebrate assemblages (Lammert and Allen 1999).Passage of the Massachusetts Rivers Protection Act in 1995 has increased protection of perennially flowing waters, but it ignores semi-permanent streams, which are critical habitat for some lotic organisms that have adapted to intermittent flow (see Stehr and Branson 1938; SaintOurs, unpublished data). Most intermittent streams have been omitted from USGS topographic maps, compounding the difficulties in proper documentation and study. As more and more water is diverted for human use with each passing year, persistently reduced base-flow levels will lead to disruption of natural ecological processes in perennial and semi-permanent (intermittent) stream habitats; there is likely a point at which water flow is too sparse (episodic) to support lotic macroinvertebrate communities. Thus, classification with regard to hydro-period of small streams is necessary as differences among running water habitats and communities and their importance to biological conservation become more evident (Feminella 1996; Williams 1996).

Despite the ecological significance of freshwater invertebrates, their centuries-old popularity with fly-fishermen, and their importance in human health concerns, detailed regional information and conservation strategies on this vastly diverse group are virtually non-existent. Adequate knowledge of the ecology and historical distributions of local species is lacking, species-level identifications are often difficult to achieve, and analysis of invertebrate survey data is typically complicated by variables too numerous to mention, making it difficult to interpret results clearly enough to prompt conservation action. A notable and successful effort to protect aquatic invertebrates of seasonally dry habitats was the public recognition of vernal pools as critical habitat for Fairy Shrimp (Eubranchipus sp.) and the publication of a field guide (Kenney and Burne 2000) for these and other animals threatened by loss of this habitat to development. Finally, some of the most photogenic inhabitants of vernal pools, bogs, lakes, streams and rivers throughout the world have also enjoyed a recent lift in popularity with conservationists and the general public - the dragonflies.

Dragonflies in Environmental Monitoring

The Odonata, better known as dragonflies and damselflies, are currently sparking great public and scientific interest, and are a useful group in biological assessments for conservation planning. Because of their habitat specificity, their role as top invertebrate predators, and their conspicuous nature – along with a practical number of species that are well known to science -- these colorful and charismatic insects work well as both “indicator” and “flagship” organisms (Corbet 1999; Samways 1993) to enhance public awareness of the links between land use, water supplies, and biodiversity (see Primack et al. 2000). The popularity of dragonfly-watching has recently been elevated by improvements in the accessibility of information, from the first published field guides to dragonflies of North America (Dunkle 2000, Nikula and Sones 2002) to regional and national list-servers and the Odonata Information Network on the World Wide Web (see Internet Resources). (See Box 2)

In Massachusetts, much has been done to assess the diversity of Odonata since the pioneering efforts of Howe (1916, 1920), Davis (1940), and others. Over the past few years, a rapidly-expanding network of odonatists has documented more than 164 dragonfly and damselfly species throughout the state (Nikula et al. 2001). As a result of their work, the Massachusetts Natural Heritage and Endangered Species Program now lists thirty-two species of Odonata as Special Concern, Threatened, or Endangered (MNH&ESP 2001a). Most studies based in the eastern part of the state were focused on lentic habitats (e.g. Carpenter 1987; Nikula 2001a) and “hotspots” for rare species , such as Ponkapoag Bog in Canton (e.g. Aliberti and Mello 1998; White 1979). However, the numbers underscore the threatened status of lotic species: 44% of the state-listed species are associated almost exclusively with rivers and streams (B. Nikula, pers. com.), although fewer than 25% of all Odonata species known to occur in Massachusetts are obligate stream-dwellers in the larval stages. This regional estimate is low when compared to an earlier assessment by the well-known odonatist G.H. Bick, who suggested that up to 82% of the Odonata species considered to be at risk in North America are associated with flowing water (Bick 1983).

More than 100 species of Odonata have been documented in Plymouth County to date. The recent addition of several rare species to the county list (Table 1), Somatochlora linearis (Corduliidae) and Gomphus abbreviatus (Gomphidae) in particular, were notable events in the documentation of aquatic insects in eastern Massachusetts. S. linearis inhabits forest streams and is difficult to document due to low densities and secretive larvae. This species was reported in Massachusetts for the first time in 1968 in nearby Norfolk County (White et al. 1974), and only a small number of times since. G. abbreviatus provided the first reported observation of an endangered lotic dragonfly in the region. A third state-listed species, the Umber Shadowdragon (Neurocordulia obsoleta), was discovered in 1998 during a Dragonfly Walk sponsored by the North and South Rivers Watershed Association. The sighting was another first for the county and one of only a handful of sightings throughout the state.

Three different Spiketail (Cordulegaster) species in adult form

In addition to state-listed species, the presence of uncommon but non-listed species is worthy of documentation. From 1997 to 2002, five such species associated with tributaries of the North River, Arigomphus villosipes, Cordulegaster maculata, C. obliqua, Lanthus vernalis, and Stylogomphus albistylus* were added to the Plymouth County list (* the observation of this species was actually an update to a historic reference). Larvae and adults of the Southern Pygmy Clubtail (L. vernalis), an inhabitant of pristine, spring-fed headwater streams (Carle 1980), were discovered in Norwell in 1997 (SaintOurs 1998) (Fig. 2), providing the first documented account of Pygmy Clubtails in Plymouth County. The Arrowhead Spiketail C. obliqua (Fig. 3A) was first documented in the county in 1998, also (J. Sones pers.com.). The larvae of this large dragonfly (Fig. 4) are known to inhabit semi-permanent streams and seeps (Clifford 1966; A. Santos, unpublished data) that, like the Pygmy Clubtail’s habitat , are often severely compromised in public and private development plans due to lack of sufficient protective legislation for both the species and their habitats.

The two clubtail dragonflies identified in Table 1 deserve further discussion in the treatment of rare Odonata in Massachusetts. Lanthus vernalis, an inhabitant of spring-fed creeks that are known to harbor rare invertebrate fauna, (Illies and Botosaneanu 1963; SaintOurs, unpublished data), is listed in Maine as a Species of Special Concern and is proposed as S2S3 in Connecticut (Wagner and Thomas 1999); however, it is not listed in Massachusetts. On the other hand Gomphus abbreviatus is listed in Massachusetts as Endangered but not listed in either CT or ME. Known to inhabit rapids of relatively clean rivers, G. abbreviatus is fairly common throughout the northeast (D. Wagner, personal communication), while L. vernalis is known only from four counties in Massachusetts and a handful of sightings elsewhere in the Northeast. Both species are restricted in range to a narrow belt along the east coast of the United States (Dunkle 2000; Needham et al. 2000), as is the more frequently-encountered Delta Spotted Spiketail Cordulegaster diastatops). Regardless of their current conservation rankings, these species need more vigilant documentation and protection.

Using Stream Invertebrates for Conservation of Aquatic Biodiversity

The concept of using invertebrates to determine the health of aquatic systems is not new, however, identifying additional indicator species for lotic habitats could greatly improve monitoring programs (See Box 3). Some aquatic insects are more useful in habitat assessments than others, depending on natural history and adult dispersal traits (Schwenneker and Hellenthal 1984), as well as our understanding of their tolerances to disturbance. For example, reservations over the use of dragonflies and damselflies as indicators are largely due to the poor correlations found between Odonata communities and human disturbance for sampled water bodies (see Barbour et al. 1996). Difficulties in using dragonflies as monitoring subjects have also been attributed to a general lack of knowledge of the larval descriptions and scarcity of baseline data (Carle 1979).

In order to effectively protect aquatic biodiversity, the first- to third-order tributary streams that constitute about 85% of the river continuum (Leopold et al. 1964) must be given greater consideration in land-use planning and development (Saunders et al. 2002). Because of limitations in our knowledge of the organisms, and limits in environmental regulations and program funding, only a marginal effort, if any, is currently put towards mitigating negative effects from small and large scale development projects on headwater stream communities. Fortunately, with heightened awareness of biodiversity conservation issues, citizen-based biological surveys and monitoring programs have found their place in NGOs and school curricula around the world. Public, private, and non-profit groups can aid in the conservation of stream habitats and species by adopting the following measures:

• Select potential indicator organisms.
  With their popularity on the rise, dragonflies and damselflies could be significant players in championing the protection of aquatic biodiversity. The key is to find appropriate indicator species for monitoring. In eastern Massachusetts, for example, adults of G. abbreviatus have been found far away from suitable larval habitat (D. Wagner, pers. com.), suggesting that they may be useful as an indicator organism in river restoration projects due to their ability to disperse and repopulate new areas. On the other hand, although local populations of L. vernalis are relatively stable (SaintOurs, pers. obs.), this tiny dragonfly exhibits poor dispersal capabilities and may not easily re-colonize a stream after a major disturbance, casting doubt on its usefulness as an indicator species (Folsom and Manuel 1983).
  
  
• Conduct baseline surveys and establish long-term monitoring programs for rare species.
  Documentation of the persistence and natural fluctuations of local dragonfly (Schmidt 1979) and other aquatic insect populations from year to year can facilitate a better assessment of the status of rare species. Statewide assessments of dragonflies have been conducted recently for other New England states, most extensively in Maine (Brunelle 1999), Connecticut (Wagner and Thomas 1999), and Rhode Island (Carpenter 1999). Although some argue that creating larger lists of “endangered” species may not advance conservation efforts, monitoring relatively rare species is necessary to detect population declines that might lead to endangerment. In addition to listing several aquatic invertebrate species, the Massachusetts Natural Heritage and Endangered Species Program has established an official “Odonata Watch List” so that rare but unprotected species can be better documented.
  
  
• Create better identification tools.
  The problems inherent in volunteer-based surveys and monitoring projects largely stem from difficulties in getting correct identifications for the many species that may be encountered in a single stream. Traditional keys produced for the identification of aquatic insects (e.g. Peckarsky et al. 1995; Merritt and Cummins 1996; Smith 1995), though indispensable to entomologists, can be difficult to use without expert help. Published range maps, if available, are usually incomplete. Training and extensive experience have been the only ways to ensure accurate identifications.
  
  Without easy-to-use and accurate identification tools, conservation efforts for most invertebrates have been slow compared to such photogenic subjects as butterflies. Until recently, using photography for taxonomically diverse groups with limited public appeal, such as aquatic insect larvae, was not cost effective and was nearly impossible for a graduate student with limited resources to master. Traditional photography techniques for tiny organisms require a great deal of experience, materials, and time. However, an alternative to relying on paper-bound keys and guides is the production of Electronic Field Guides (EFGs) (http://www.cs.umb.edu/~alyons/efg_web/). EFGs are the convergence of field guides, biological databases, and identification keys to assist individuals, institutions, and non-governmental organizations in effectively documenting and researching biodiversity. Using ever-improving digital imaging technology, rapid production of high-quality images for the assembly of identification tools is possible. For most people, the image-based approach offers advantages over keys. Also, electronic field guides overcome the economic constraints of producing standard, printed field guides.
  
  
• Support independent research projects.
  The benefits of individual studies are many. Contributions to the knowledge of aquatic macroinvertebrates by interested individuals are indispensable to the various organizations working to protect water resources. These include local watershed organizations, municipal authorities, educational institutions, and other groups concerned with the fate of their water supply or backyard stream. Regular reports to town selectmen and conservation commissions should include species lists for sites relevant to current construction proposals and water supply protection efforts. With this information, further development of watersheds can be investigated more thoroughly in hopes that stream-dwelling organisms will be protected from human encroachment well into the future.

Larvae of the Arrowhead Spiketail Dragonfly - Cordulegaster obliqua inhabit intermittent streams in eastern Massachusetts. These large predators have a life span of several years, reaching almost 2 inches in length before they emerge. Neither the dragonfly nor its habitat are currently protected in the state.

Internet Resources: Freshwater Conservation Environmental Protection Agency’s Watershed Protection Homepage (http://www.epa.gov/owow/watershed/) The Nature Conservancy’s Freshwater Initiative (http://www.freshwaters.org/home.html) Massachusetts Natural Heritage and Endangered Species Program (http://www.state.ma.us/dfwele/dfw/nhesp/heritage.htm) Massachusetts Riverways Program: List of MA watershed organizations (http://www.state.ma.us/dfwele/river/rivbasin.htm) Odonata Odonata Information Network (http://www.afn.org/~iori/) Odonata Bibliography compiled by R. Beckemeyer (http://www.windsofkansas.com/odbib.html) USGS Biological Survey Odonata distribution maps (http://www.npwrc.usgs.gov/resource/distr/insects/dfly/DFLYUSA.HTM) Ode News: An occasional newsletter about dragonflies and damselflies in southern New England (http://www.odenews.net/). This is by far the most comprehensive source of information on Odonata of Massachusetts. The site includes species lists organized by taxonomic family as well as by county, and has hundreds of excellent photographs and links to other relevant sites. Maine Dragonfly and Damselfly Survey (http://mdds.umf.maine.edu/~odonata/) Michigan Odonata Survey (http://insects.ummz.lsa.umich.edu/MICHODO/MOS.html) For those interested in getting more involved, the following list-servs facilitate interactions among experts and enthusiasts from around the world. National and International. Odonata@orion.ups.edu Regional. http://www.odenews.net/NEodes.html

ACKNOWLEDGEMENTS

Thanks to Blair Nikula and David Wagner for their expertise, Anna Santos for her field assistance, Hal White III and Marsha Salett for their comments on earlier versions of this paper, Michael May, Dennis Paulson and everyone on the Odonata list for advice, Fred Goodwin of the Massachusetts Audubon Society for his donation of larval specimens, photos, and information on C. obliqua, the Massachusetts Environmental Trust, George Zoto and the Executive Office of Environmental Affairs, Massachusetts Riverways Program, K.D.B. Dijkstra and the Flying Dutchmen, Brian Reid, Lance Van Lenten and the First Herring Brook Watershed Initiative, the North and South Rivers Watershed Association, UMass Boston, and Dr. R.D. Stevenson for his patience and support.

Image credits:

1. Map of North River tributary system - Data source: MassGIS; F. SaintOurs.
2. Southern Pygmy Clubtail Lanthus vernalis - F. SaintOurs, Norwell.
a. Larvae, showing two sizes found together in a single sample as evidence of semi-voltine life cycle.
b. Adult male.
c. Habitat – a tiny, sand-bottomed, spring-fed creek with neutral pH.
3. Three species of Spiketails, showing differences in abdominal patterns.
a. Arrowhead Spiketail Cordulegaster obliqua - F. Goodwin, Topsfield.
b. Twin Spotted Spiketail C. maculata - F. SaintOurs, Pembroke.
c. Delta Spotted Spiketail C. diastatops - F. SaintOurs, Pembroke.
4. Arrowhead Spiketail C. obliqua larva - F. SaintOurs, Marshfield (courtesy of Mass. Environmental Trust).

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