APPENDIX 1. Recommendations from invasion biologists

MARK BERTNESS, Brown University

Understanding the mechanisms and consequences of biological invasions is an important issue that has received considerable recent attention due to the accelerated rate of anthropogenic introductions over the past few centuries. Of particular concern in estuarine habitats are invasions of numerically dominant habitat modifying organisms like marsh grasses and gregarious filter feeders and top consumers. Invasive habitat modifiers such as cordgrass, mussels, clams and canopy-forming algae like Codium are all capable of dramatically impacting estuarine habitats. Invasive top consumers like green crabs are similarly capable of dramatically impacting estuarine communities directly by their control of food webs or indirectly by controlling the abundance of habitat modifying organisms.

Invasive species, however, are not the only or even the most critical anthropogenic problem confronting North American estuaries. Sea-level rise associated with climate change, over harvesting, eutrophication, shoreline development and large-scale manipulations of the freshwater that feeds estuaries are all massive problems. Each of these problems is serious enough, but can also potentially interact with biological invasions to accelerate the homogenization of estuarine biota. The bottom line - North American estuarine habitats are currently undergoing massive change due to human population pressure. Invasive species are only one of the problems. This needs to be kept in perspective in designing any long-term estuarine monitoring program.

The NERRS is a relatively new partnership between NOAA and state or local private organizations. NERRS represents a valuable network of research reserves set aside for research and education. Increasing development pressure on coastal habitats has made the reserves critical refuges for researchers to study coastal systems. The reserve system also has great untapped potential to monitor coastal systems. In spite of wide recognition that estuarine habitats are undergoing or are on the verge of rapid human-induced changes, however, no monitoring program of habitats in the reserve system is in place. This is shameful. NERRS managers cannot really answer such simple critical questions as "How are the biological communities in your reserve changing?" or "What kind of shape are the biological communities in your reserve in?" In 1999 in collaboration with the Ecological Society of America NERRS sponsored a meeting to discuss establishing a system wide monitoring program. The outcome was extremely disappointing. NERRS sites currently only monitor weather conditions and water quality. No monitoring of biological communities is going on or even planned that could detect long-term shifts in estuarine communities driven by the variety of stresses being applied to these habitats by expanding human populations and shoreline development.

Describe an ideal monitoring program to answer invasion biology questions. Any system-wide monitoring program should be designed to detect long-term changes and assess community status as the major objective. Designing a monitoring program to explicitly answer invasion biology questions rather than to best detect change and habitat status, in my opinion, would be irresponsible. It is getting the bandwagon way in front of the horse. Using the current interest in invasive species to get a monitoring program in place, however, is great. An ideal monitoring program would provide annual data on the abundance and distribution of key species along with data on the primary production of the major primary producers. The exact data that would be important to collect would differ among reserves dictated by the types of habitats within each reserve. Using GPS and digital photography could simplify and standardize data collection. On the east coast of North America where most NERRS sites are dominated by salt marshes, monitoring permanent plots on zonal borders, fish and crustacean utilization of marsh creeks, the primary productivity of cordgrass and the abundance and distribution of shallow water benthic assemblages, including seagrass beds, would generate a data set that would detect short and long term changes in these system including the spread of invasive species.

How would the results of this sort of monitoring program be of value in investigations of invasions? A broadly designed monitoring program for NERRS biological communities would provide an unprecedented data set that would give reserve managers hard data on the status of their reserves biological resources. This would include the impact and spread of invasive species, but not be constrained by focusing only on invasive species.

Would the type of monitoring program you propose be useful to managers or would it be of more scientific interest? The general type of monitoring program I envision would be immensely valuable to both reserve managers and estuarine scientists. Monitoring efforts targeted on quantifying the abundance of specific taxa are shortsighted because they can typically only address anticipated questions. A long-term monitoring program focused on assessing the status and detecting change in reserve communities would give resource managers the quantitative data they need to convince funding agencies and the public that changes are occurring in North American estuaries. This would include documenting invasions, but would also detect changes due to sea-level rise, eutrophication and other anthropogenic forces impacting estuaries.

How would the data from this monitoring program have been useful to coastal managers? Currently Narragansett Bay, where I do much of my work, is being heavily impacted by shoreline development, eutrophication and population expansions of nuisance species, some of which may be non-native. In many shallow water benthic habitats shoreline development is precipitating eutrophication, which is leading to anoxia and dense blooms of weedy, ephemeral seaweeds that are suffocating the benthic community. In adjacent salt marshes, increased nitrogen loading is upsetting the traditional competitive relationships of the marsh building halophytes leading to marshes being displaced by monocultures of cordgrass and Phragmites. Unfortunately, it is very difficult to unambiguously document even these massive changes since virtually no baseline data exist. If a basic biological community monitoring program had been established 20 years ago, these changes would be well documented and easy to communicate to the general public, regulatory agencies and the scientific community.

APPENDIX 1

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