Info

Hudson estuaries lakes

Figure 19.6. Biomass of zooplankton and zoobenthos in large rivers, the freshwater tidal Hudson River, estuaries, and lakes. Boxes show25th and 75th percentiles (horizontal line is the median), whiskers show 5th and 95th percentiles, and dots show outliers. For zoobenthos, sample sizes are as follows: large rivers (10), Hudson River (2; i.e., pre- and post zebra mussel invasion), estuaries (23), and lakes (41). Zooplankton data from Pace, Findlay, and Lints (1992); zoobenthos data compiled from various sources.

that benthic biomass is especially high in estuaries (Fig. 19.6). Perhaps estuaries support higher benthic biomass than lakes because estuaries have greater inputs of physical energy (especially tidal currents), which leads to better vertical mixing and higher rates of food supply to the sediments (Nixon, 1988). The beneficial effects of physical energy may be reduced in rivers because of high temporal variance in energy supply rates, leading to scour, fill, and disturbance of the benthos. Further, food quality may be lower in rivers than in estuaries because of greater relative inputs of detrital allochthonous material of low nutritional quality. Thus, although site-to-site variation will be high, zoobenthos/zooplankton ratios might be highest in rivers, intermediate in estuaries, and lowest in lakes.

Traditionally, the ecological communities of the sediments and open water are considered separately, probably because the different habitats

Figure 19.7. Diagram of the major community interactions in aquatic ecosystems such as the Hudson River. Arrows show the hypothesized direction of control. Note that many interaction arrows cross the sediment-water interface.

are studied by different groups of scientists using different methods. Nevertheless, connections between the benthos and the overlying water of the Hudson are numerous and strong (Fig. 19.7). Benthic suspension-feeders, especially bivalves, can regulate the amount and kind of plankton (Dame, 1996; Strayer et al., 1999), as was shown most clearly by the zebra mussel invasion of the Hudson (Cole and Caraco, Chapter 9, this volume; Pace and Lonsdale, Chapter 16, this volume). The benthic animal community in turn depends on the amount and kind of plankton as a key food source. Seasonal, interannual (Johnson, Bostrom, and van de Bund, 1989), or long-term changes in the plankton can cause large changes in the zoobenthos. In the Hudson, the removal of edible suspended particles by zebra mussels led to large changes in the zoobenthos (Fig. 19.4). Ben-thic plant communities likewise depend on the amount of suspended particles, which regulate the amount of light that penetrates to the sediments. A concrete example of this link was the possible increase in rooted plants (Caraco et al., 2000; Findlay et al., Chapter 17, this volume) and associated animals (Fig. 19.4) after zebra mussels reduced plankton biomass in the Hudson. Further, rooted plants may negatively influence phytoplankton, through a complex series of interactions (Scheffer, 1998). Finally, as shown in Table 19.1, benthic prey dominates fish diets in the Hudson, so that there maybe strong reciprocal links between fish and zooben-thos in aquatic ecosystems (e.g., Strayer, 1991).

Thus, manyaquatic ecosystems, especiallyshallow, well mixed habitats like the Hudson, function more as unified systems than as the isolated boxes suggested by compartmentalized research studies and textbook diagrams.

Acknowledgments

I appreciate the dedicated assistance of Chris Anderson, Chris Borg, Karyl Brewster-Geisz, David Cohen, Chris Edelstein, David Fischer, Dean Hunter, Jeff Janota, Carolyn Klocker, Craig Jankowski, Greg Lampman, Colleen Lutz, Heather Malcom, Erik Molinaro, Alex Nixon, Elizabeth Pangia, Sarah Poppenhouse, Bill Shaw, Lane Smith, Martha Young, and Brian Zielinski, and the continued intellectual support of my colleagues Nina Caraco, Jon Cole, Stuart Findlay, and Mike Pace. Stuart Findlay offered helpful comments on the manuscript. I am grateful to the Hudson River Foundation and the National Science Foundation for their support of my work on the Hudson's zoobenthos. This is a contribution to the program of the Institute of Ecosystem Studies.

references

Bath, D. W., and O'Connor, J. M. 1985. Food preferences of white perch in the Hudson River estuary. New York Fish and Game Journal 32: 63-70. Beckett, D. C. 1992. Phenology of the larval Chirono-midae of a large temperate Nearctic river. Journal of Freshwater Ecology 7: 303-316.

Bode, R. W., Novak, M. A., Fagnani, J. P., and Denicola, D. M. 1986. The Benthic Macroinvertebrates of the Hudson River from Troy to Albany, New York. Final Report to the Hudson River Foundation, NewYork.

Burch, J. B. 1975. Freshwater unionacean clams (Mollusca, Pelecypoda) of North America. Revised edition. Hamburg, MI: Malacological Publications.

Caraco, N. F., Cole, J. J., Findlay, S. E. G., Fischer, D. T., Lampman, G. G., Pace, M. L., and Strayer, D. L. 2000. Dissolved oxygen declines associated with the invasion of the zebra mussel (Dreissena poly-morpha). Environmental Science and Technology 34: 1204-1210.

Caraco, N. F., Cole, J. J., Raymond, P. A., Strayer, D. L., Pace, M. L., Findlay, S. E. G., and Fischer, D. T. 1997. Zebra mussel invasion in a large, turbid river: phytoplankton response to increased grazing. Ecology 78: 588-602.

Carlson, D. M., and Simpson, K. W 1987. Gut contents of juvenile shortnose sturgeon in the Upper Hudson River estuary. Copeia 1987: 196-202.

Cole, J. J., Caraco, N. F., and Peierls, B. 1992. Can phytoplankton maintain a positive carbon balance in a turbid, freshwater, tidal estuary? Limnology and Oceanography 37: 1608-1617.

Crandall, M. E. 1977. Epibenthic invertebrates of Croton Bay in the Hudson River. New York Fish and Game Journal 24: 178-86.

Crumb, S. E. 1977. Macrobenthos of the tidal Delaware River between Trenton and Burlington. Chesapeake Science 18: 253-65.

Curran, H. W, and Ries, D. T. 1937. Fisheries investigations in the lower Hudson River, in E. Moore (ed.). A Biological Survey of the Lower Hudson watershed. Supplement to the 26th Annual Report of the New York State Conservation Department, Albany, NY, pp. 124-45.

Dame, R. F. 1996. Ecology of Marine Bivalves:AnEcosys-tem Approach. Boca Raton, FL: CRC Press.

Dekay, J. E. 1844. Zoology of New York. Part 5. Mollusca. Albany, NY: Carroll and Cook.

Diaz, R. J. 1989. Pollution and tidal benthic communities of the James River estuary, Virginia. Hydrobi-ologia 180: 195-211.

Duryea, M. and Schmidt, R. E. 1987. Feeding biology of tesselated darter (Etheostoma olmstediatromacu-latus)atTivoli North Bay, Hudson River, New York, inE. A. Blair and J. C. Cooper (ed.). Polgar Fellowship reports of the Hudson River National Estuar-ine Research Reserve Program, i986.HudsonRiver Foundation, New York, NY, pp. III-1-III-19.

Ettinger, W. S. 1982. Macrobenthos of the freshwater tidal Schuylkill River at Philadelphia, Pennsylvania. Journal of Freshwater Ecology 1: 599-606.

Findlay, S., Pace, M. L., and Fischer, D. T. 1998. Response ofheterotrophicplanktonic bacteria to the zebra mussel invasion of the tidal freshwater Hudson River. Microbial Ecology 36: 131-40.

Findlay, S., Schoeberl, K., and Wagner, B. 1989. Abundance, composition, and dynamics of the invertebrate fauna of a tidal freshwater wetland. Journal of the North American Benthological Society 8:

Was this article helpful?

0 0

Post a comment