BIOCRITERIA FOR ASSESSING THE BIOLOGICAL INTEGRITY OF HAWAII'S STREAMS
Michael H. Kido and Gordon C. Smith
Hawaii Stream Resarch Center - University of Hawaii Center for Conservation Research & Training
Paper presented at the 1997 Conservation Conference, July 24-25, Maui, Hawaii
The idea of utilizing biological attributes of ecosystems as indicators of quality is a relatively old one and it actually has been fairly well developed for use in streams and rivers in such states as Ohio, North Carolina, and Maine. The impetus for such work has arisen from concern over the declining quality of water resources in the US over the past several decades and associated with this concern, some strong federal legislation, most notably the Clean Water Act passed in 1977, which mandates States to safeguard their water resources.
Here in Hawaii, one of the major lessons learned from what has come to be called the 'Waiahole Controversy', is that we are ill-equipped to deal with water resource protection and conservation issues, particularly with regard to the allocation disputes which inevitably will arise when there are competing uses for a finite resource. For those of you from out-of-state, the controversy in this case is the classic one, with large landowners tugging on one side of the rope for water to develop their lands and stimulate the economy and on the other end of the rope, the small subsistence user demanding that water be returned to their stream to protect rural lifestyles and maintain habitat for native species. A crucial environmental question being asked is, 'How much water should be left in the stream to protect native species and maintain natural function?' This is followed with the corollary question, 'How would we know that the negotiated level of conservation flow actually improved stream quality over time?'
In order to address these crucial questions, we must first of all be able to measure the condition of the resource and then be able to assess improvement or impairment of that resource as a result of the decisive management action. The approach that has shown remarkable success in other states, is the use of narrative and numeric biological criteria or biocriteria, as it is perhaps better known, that describe the preferred biological condition of aquatic communities. Trying to agree upon what is the preferred condition, however, can get pretty sticky when opposing parties each bring their own experts to the table. And this, in fact, is what happened in the Waiahole deliberations. We, therefore, must first agree upon some standard and my suggestion, is that we adopt as this standard of Hawaiian stream quality, the condition of the native components in a stream as indicators of the functioning ecosystem. In this standard, then, we focus on native species as well as the functional aspects of their environment which keep them healthy.
How, then, could this standard integrated into biocriteria, be applied to assess and monitor the impacts of these diverse uses of the Hanalei River on Kauai island? Implied in the term biocriteria is the notion of comparison to the highest attainable condition. This concept therefore incorporates the reality that that there are no more biologically pristine ecosystems, streams or otherwise, left in Hawaii. The general approach is to use minimally impacted streams to provide reference conditions. For Hawaii, this would mean that we would use the best streams on each island as a basis for developing a set of biological attributes, or metrics, which will be used to measure water quality. Biotic integrity for Hawaiian streams would be conceptually defined as the most robust native aquatic community expected in a natural condition and biocriteria will be used to protect these resource values. In this system, natural or minimally impaired water resource conditions, therefore, become the criteria for judgment and management
The metrics that are chosen to assess biotic integrity must not only reflect community characteristics but also change in predictable ways with increased human influence. In other words, two sets of metrics are required, one which contrasts the elements of the ecosystem with functional relationships and a second set, which measures the degradative effects of human activities on the resident biota. The challenge in implementing biocriteria is to develop reliable and cost-effective ways to quantify these attributes using carefully selected representative taxa. The end-product of this work will be a set of quantified metrics obtained through standardized protocols which will yield a single, ecologically-based index of water resource quality.
One of the problems that we have been struggling with lately in our assessment work has to do with making biotic comparisons in streams which may differ drastically in physical attributes. Do streams which differ significantly in flow velocities, oxygen saturation, and dominant substrate type, for example, differ naturally in biotic attributes as well? Can we compare streams across islands for these biotic attributes using some statewide set of metrics? Judging from some recent work that we've done comparing physical and chemical attributes of sites at similar elevations on Onomea and Alakahi Streams on the Big Island with Limahuli Stream on north Kaua'i, that answer appears to be, MAYBE NOT. Streams within-islands or island-regions appear to have certain characteristic signatures of hydrology and physiography that may govern their biotic attributes. Physical metrics, therefore, should be incorporated into protocols for standardization and reference conditions may need to be developed for regional streams within-islands or groups of islands.
On this map are located study sites on Kauai streams where we have applied standardized assessment protocols over the past several years. These data will be used as a basis for examining the range of suitable metrics. GIS or Geographical Information System displays, like this one and others used throughout this presentation, demonstrate the usefulness of this system as a powerful tool for resource management application in Hawaii.
One of the advantages of working in Hawaiian streams for biocriteria development, is the simplified nature of its native components and the fact that, for most taxa anyway, we can readily distinguish natives from aliens. Focusing on flowing, wadable Hawaiian streams for now, leaving aside deep estuaries which will require a separate set of metrics, the abundances and composition of populations of our native stream fish species, known locally as 'o'opu, are obvious choices for community metrics. These species are readily distinguishable and respond to varying degrees, inter-specifically, to human intervention. While we have made advances in understanding their functional roles, and have put considerable effort into developing robust methods of quantifying their densities, there is still much we need to learn about their population dynamics.
For example, we know little about temporal variation in population structure or the factors which influence such variation. In Kalalau Stream on Kauai's Na Pali coast 'o'opu populations are structured in definite patterns with certain species exhibiting higher densities in certain elevational segments until all fish disappear above around 250 meters in elevation. For our fish metrics to be meaningful, then, we need to get a better handle on the dynamics of population change and then incorporate this in some fashion into the metrics that we choose to use.
Fish condition and the relative abundances of alien fish species in streams provide potential metrics for assessing biotic impairment. Huge die-offs of native oopu chronically occur in de-watered stream reaches which are preceded by rampant disease in the population. In degraded streams native oopu are often infested with Myzobdella lugubris, an alien freshwater leech, which attach to their fins and eyes and are agents of disease and mortality. Bill Font, from Southeastern Louisiana University, has connected the infestation of native oopu with Asian tapeworms to high densities of alien poeciliids (Poeciliidae), such as swordtails (Xiphophorous helleri), which are becoming more common now in many of Hawaii's streams. While poeciliids were introduced into Hawaii for mosquito control, I'm not sure why anyone in their right mind would want to introduce Tilapia mossambica into Hawaiian streams but people have and now this aggressive cichlid (Cichlidae) from Africa preys upon and competes directly with native oopu for food and space. Higher scores on these metrics would, obviously, correlate with increased impairment and therefore lower stream quality.
Many states also incorporate metrics using indicator insect taxa such as EPT, which stands for the insect orders Ephemeroptera-Plecoptera-Tricoptera, none of which include species native to Hawaiian streams. Based on our intensive sampling of swift-water habitat in a variety of streams over the years, it turns out that most of the insect biomass now collected off the stream bottom in Hawaii, are three alien species; a midge, Cricotopus bicinctus (Diptera: Chironomidae) and two caddisfly species, Cheumatopsyche pettiti (Tricoptera: Hydropsychidae) and Hydroptila arctia (Tricoptera: Hydroptilidae). Since their introductions, these aliens have spread throughout Hawaii and now dominate swift-water stream habitat. Our diet studies on native stream fishes, interestingly, have shown that these alien insects are now used by them as food, particularly in the case of the o'opu-nakea. Although alien species, they may be useful as indicators of biotic impairment as they do seem to be intolerant of reduced flow, chemical pollution, and low dissolved oxygen.
Certain native macroinvertebrates are good candidate indicator taxa. Native mountain shrimp, opae kalaole, as well as the native stream snail, hihiwai, are more abundant in higher quality streams and appear to be quite sensitive to sedimentation, dewatering and low oxygen. For insects, Dan Polhemius (formerly with Bishop Museum now with the Smithsonian Institute) has suggested incorporation of a 'torrenticlous guild' which I'll call T-S-P for Telmatogeton spp., Scatella spp, and Procanace spp., as a metric. Flies from at least one of these endemic genera are nearly always present in moderate to excellent quality stream habitat and they appear to be extremely sensitive to flow reduction. Similarly, the presence of native odonates, damselflies and dragon flies, suggest high stream quality and therefore are also probably effective indicator taxa. Quantifying the abundances of these invertebrates, however, is notoriously difficult and we have been testing traps and other devices for their efficacy in sampling protocols.
Algae have been infrequently used in assessment programs for a variety of reasons yet for Hawaiian streams, anyway, they may be an important functional metric. Our diet studies have shown, for example, that algae provide the bulk of the food for all native stream fishes. From the little we know of their ecology, most immature forms of native aquatic insects appear to utilize algae for food, shelter, or in various phases of their development. This possibly new Telmatogeton species, for example, builds its pupal case within and feeds upon this green alga identified as Cladophora glomerata. Our benthic data also indicates that certain algal species are common in unaltered stream habitat which suggests that, as with fish and invertebrates, we may be able to find suitable indicator algal species. Two possibilities are this green alga you see here, Cladophora glomerata and a blue-green Nostoc verrucosum. There may be other algae, such as Spirogyra sp. and Ulothrix sp., which are more abundant in dewatered or degraded conditions and these may then be useful in a series of algal metrics that measure impairment.
There is good reason to be concerned about the quality of Hawaii's freshwater resources for, after all, we do live on islands and depend upon these finite resources for our very survival. Streams inter-connect the terrestrial landscape to the marine environment and we must recognize this as we shift our emphasis away from saving single species to the conservation of functional island ecosystems. We must also somehow come to grips with our society's seemingly insatiable need for more water. Perhaps the place to start, is to recognize that the water that sustains us in our island ecosystem and the water that sustains native stream organisms are one and the same, and by protecting one, we can also protect the quality of the other.