Abstract
This study describes a hyporheic zone that exists beneath a river-dominated estuary in North Wales, and which spans the freshwater/saltwater boundary. A series of 72 cores was taken from the Aber Estuary, in September, at depths from 10–60 cm below the bed surface. Site 1 was above the extreme high water mark and therefore was never inundated by salt water. Site 5 was the furthest downstream and was inundated twice daily by incoming tides. Substrates contained more gravel at the upstream sites and closer to the bed surface, with more sand and silt at downstream sites and at depth. Salinity of interstitial water increased both with distance away from Site 1 and with increasing depth into the zone, reaching a maximum of 15‰ at 60 cm at Site 5, as measured at low tide. Longitudinal and vertical zonations of the invertebrate taxa were evident, and densities were greater in the top 40 cm than below. Nematodes were especially abundant from 10–60 cm, and genera differed along the estuary. Oligochaetes were well represented at most sites, with the less saline sites yielding Naididae, Enchytraeidae, Aeolosomatidae and Tubificidae; Site 5 was dominated by Tubifex costatus. Chironomid larvae were most abundant to 40 cm at Sites 1 and 2 (primarily Brillia modesta, Corynoneura sp., Tanytarsus sp., and unidentified Tanypodinae), but they were also found at Site 3 (to 60 cm), and at 10 cm at Site 5 (Orthocladius sp.). Nymphs of mayflies and caddisfly larvae were found primarily at Site 1, but small stonefly nymphs and elmid beetle larvae were taken at Site 2 depths where the interstitial water was brackish. The most saline sediments were populated by the triclad Uteriporus vulgaris, the polychaete Nereis sp., and snails (Hydrobia sp.). Site, salinity, pH, and sand and silt contents appeared to influence species distribution most; together, these explained 37.8% of the variance (CANOCO). There was an overall negative relationship between silt content of the sediments and total invertebrate density. The hyporheic zone of the Aber Estuary is thus not only influenced by surface water and, presumably, estuarine groundwater exchanges, but is further complicated, biologically, by having a salinity gradient running through it. The term `brackishwater hyporheic zone' (BHZ) is proposed to describe this and similar systems.
Similar content being viewed by others
References
Ansari, A., C. U. Rivonkar & U. M. Sangodkar, 2001. Population fluctuation and vertical distribution of meiofauna in a tropical mudflat at Mandovi estuary, west coast of India. Indian Journal of Marine Science 30: 237-245.
Bassett, D. A., 1967. A Source-Book of Geological, Geomorphological and Soil Maps for Wales and the Welsh Borders (1800-1966). Amgueddfa Genedlaethol Cymru, Cardiff. 322 pp.
Beukema, J. J., 1974. Seasonal changes in the biomass of the macrobenthos of tidal flat areas in the Dutch Wadden Sea. Netherlands Journal of Sea Research 8: 94-107.
Boulton, A. J., P. Marmonier & J. A. Davis, 1999. Hydrological exchange and subsurface water chemistry in streams varying in salinity in south-western Australia. International Journal of Salt Lakes Research 8: 361-382.
Boulton, A. J., C. Hakenkamp, M. Palmer & D. Strayer, 2002. Freshwater meiofauna and surface water-sediment linkages: a conceptual framework for cross-system comparisons. In Rundle, S. D., A. L. Robertson & J. M. Schmid-Araya (eds), Freshwater Meiofauna: Biology and Ecology. Backhuys Publishers, Leiden: 241-259.
Bouwman, L. A., K. Romeyn & W. Admiraal, 1984. On the ecology of meiofauna in an organically polluted estuarine mudflat. Estuarine, Coastal and Marine Science 19: 1-17.
Boyden, C. R. & C. Little, 1973. Faunal distributions in soft sediments of the Severn estuary. Estuarine, Coastal and Marine Science 1: 203-223.
Brinkhurst, R. O., 1964. Observations on the biology of the marine oligochaete Tubifex costatus. Journal of the Marine Biological Association of the United Kingdom 44: 11-16.
Brown, E. H., 1960. The Relief and Drainage of Wales, a Study in Geomorphological Development. University of Wales Press, Cardiff, 264 pp.
Buzzelli, C. P., R. A. Luettich, S. P. Powers, C. H. Peterson, J. E. McNinch, J. L. Pinckney & H. W. Paerl, 2002. Estimating the spatial extent of bottom-water hypoxia and habitat degradation in a shallow estuary. Marine Ecology Progressive Series 230: 103- 112.
Coull, B. C., 1999. Role of meiofauna in estuarine soft bottom habitats. Australian Journal of Ecology 24: 327-343.
Crofton, H. D., 1966. Nematodes. Hutchinson University Library, London, 160 pp.
Cummins, K. W., 1962. An evaluation of some techniques for the collection and analysis of benthic samples with special emphasis on lotic waters. American Midland Naturalist 67: 477-504.
Dame, R. F. & D. M. Allen, 1996. Between estuaries and the sea. Journal of Experimental Marine Biology and Ecology 200: 169- 185.
Di Sabatino, A., P. Martin, R. Gerecke & B. Cicolani, 2002. Hydrachnidia (Water Mites). In Rundle, S. D., A. L. Robertson & J. M. Schmid-Araya (eds), Freshwater Meiofauna: Biology and Ecology. Backhuys Publishers, Leiden: 105-133.
Dyer, K. R., 1973. Estuaries: A Physical Introduction. John Wiley, London, 140 pp.
Essink, K. & H. Keidel, 1998. Changes in estuarine nematode communities following a decrease of organic pollution. Aquatic Ecology 32: 195-202.
Fraser, B. G. & D. D. Williams, 1998. Seasonal boundary dynamics of a groundwater/ surface-water ecotone. Ecology 79: 2019-2031.
George, C. L. & J. A. Lindley, 1997. Hatching nauplii of planktonic calanoid copepods from intertidal estuarine sediments. Journal of the Marine Biological Association of the United Kingdom 77: 899-902.
Giere, O., 1973. Oxygen in the marine hygropsammal and the vertical microdistribution of oligochaetes. Marine Biology 21: 180-189.
Godbout, L. & H. B. N. Hynes, 1982. The three dimensional distribution of the fauna in a single riffle in a stream in Ontario. Hydrobiologia 97: 87-96.
Goodey, T., 1963. Soil and Freshwater Nematodes (2nd ed. revised and rewritten by J. B. Goodey) Methuen, London, 544 pp.
Green, J., 1968. The Biology of Estuarine Animals. Sidgwick and Jackson, London, 401 pp.
Gyedu-Ababio, T. K., J. P. Furstenberg, D. Baird, & A. Vanreusel, 1999. Nematodes as indicators of pollution: a case study from the Swartkops River system, South Africa. Hydrobiologia 397: 155-169.
Hakenkamp, C. C. & M. A. Palmer, 2000. The ecology of hyporheic meiofauna. In Jones, J. B. & P. J. Mulholland (eds), Streams and Ground Waters. Academic Press, Boston: 307-336.
Hayashi, M. & D. O. Rosenberry, 2002. Effects of ground water exchange on the hydrology and ecology of surface water. Groundwater 40: 309-316.
Hynes, H. B. N., T. T. Macan, & W. D. Williams, 1960. A key to the British species of Crustacea: Malacostraca. Freshwater Biological Association of the United Kingdom, Scientific Publication 19: 1-36.
Jones, J. B. & P. J. Mulholland (eds), 2000. Streams and Ground Waters. Academic Press, Boston, 456 pp.
Jones, M. B., 1972. Osmoregulation in the Jaera albifrons group of species. Journal of the Marine Biological Association of the United Kingdom 52: 419-427.
Kumar, R. S., 1997. Vertical distribution and abundance of sediment-dwelling macroinvertebrates in an estuarine mangrove biotope. Indian Journal of Marine Science 26: 26-30.
Li, J., M. Vincx & P. M. J. Herman, 1997. Carbon flows through meiobenthic nematodes in the Westerschelde Estuary. Fundamentals of Applied Nematology 20: 487-494.
Macan, T. T., 1977. A key to the British fresh-and brackish-water gastropods. Freshwater Biological Association of the United Kingdom, Scientific Publication 13: 1-46.
Mannino, A. & P. A. Montagna, 1997. Small-scale spatial variation of macrobenthic community structure. Estuaries 20: 159-173.
Marshall, D. J., R. Perissinotto, C. Nozais, C-J. Haines & S. Proches, 2001. Occurrence of the astigmatid mite Tyrophagus in estuarine benthic sediments. Journal of the Marine Biological Association of the United Kingdom 81: 889-890.
McLusky, D. S., 1981. The Estuarine Ecosystem. John Wiley & Sons, New York.
Michaelis, H., H. Fock, M. Grotjahn & D. Post, 1992. The status of the intertidal zoobenthic brackish-water species in estuaries of the German Bight. Netherlands Journal of Sea Research 30: 201-207.
Miller, D. C., S. L. Poucher & L. Coiro, 2002. Determination of lethal dissolved oxygen levels for selected marine and estuarine fishes, crustaceans, and a bivalve. Marine Biology 140: 287-296.
Ndaro, S. G. M. & E. Olafsson, 1999. Soft-bottom fauna with emphasis on nematode assemblage structure in a tropical intertidal lagoon in Zanzibar, eastern Africa: I. Spatial variability. Hydrobiologia 405: 133-148.
Odum, W. E., 1988. Comparative ecology of tidal freshwater and salt marshes. Annual Revue of Ecology and Systematics 19: 147-176.
Remane, A. 1958. Ökologie des Brackwassers. In Die Biologie des Brackwassers. Schweizerbartsche Verlag, Stuttgart: 1-213.
Rundle, S. D., M. J. Attrill & A. Arshad, 1998. Seasonality in macroinvertebrate community composition across a neglected ecological boundary, the freshwater-estuarine transition zone. Aquatic Ecology 32: 211-216.
Seys, J., M. Vincx & P. Meire, 1999. Spatial distribution of oligochaetes (Clitellata) in the tidal freshwater and brackish parts of the Schelde Estuary (Belgium). Hydrobiologia 406: 119-132.
Smith, I. M. & D. R. Cook, D. R., 1991. Water mites. In Thorpe, J. H. & A. P. Covich (eds), Ecology and Classification of North American Freshwater Invertebrates. Academic Press, New York: 523-592.
Smith, I. M., E. E. Lindquist & V. Behan-Pelletier, 1998. Mites (Acari). In Scudder, G. G. E. & I. M. Smith (eds), Assessment of Species Diversity in the Montane Cordillera Ecozone. Ecological Monitoring and Assessment Network, Burlington, Ontario, Canada: http://www.eman-rese.ca/eman/reports/publications/99_montane/intro.html
Stanley, E. H. & J. B. Jones, 2000. Surface-subsurface interactions: past, present, future. In Jones, J. B. & P. J. Mulholland (eds), Streams and Ground Waters. Academic Press, Boston: 405-417.
Stoch, F. & P. Pospisil, 2000. Redescription of Diacyclops disjunctus (Thallwitz, 1927) from Austria, with remarks on the Diacyclops languidus-group in Europe (Copepoda, Cyclopoida, Cyclopidae). Crustaceana 73: 469-478.
Storey, R. G., K.W. F. Howard & D. D. Williams, 2003. Factors controlling riffle-scale hyporheic exchange flows and their seasonal changes in a gaining stream: a three-dimensional groundwater flow model. Water Resources Research 39: 1-17.
ter Braak, C. J. F., 1987-1991. CANOCO: A Fortran programme for canonical community ordination by partial detrended canonical correspondence analysis, principal components analysis and redundancy analysis. Technical Report LWA-88-02, Agricultural & Mathematical Group, Wageningen, The Netherlands, 233 pp.
Traunspurger, W, 2002. Nematoda. In Rundle, S. D., A. L. Robertson & J. M. Schmid-Araya (eds), Freshwater Meiofauna: Biology and Ecology. Backhuys Publishers, Leiden: 63-104.
Vopel, K., J. Dehmlow & G. Arlt, 1996. Vertical distribution of Cletocamptus confluens (Copepoda, Harpacticoida) in relation to oxygen and sulphide microprofiles of a brackishwater sulphuretum. Marine Ecology Progressive Series 141: 129-137.
Warwick, R. M. & R. Price, 1975. Macrofauna production in an estuarine mud-flat. Journal of the Marine Biological Association of the United Kingdom 55: 1-18.
Wharfe, J. R., 1977. The intertidal sediment habitats of the lower Medway Estuary, Kent. Environmental Pollution 13: 79-91.
Williams, D. D., 1981. Evaluation of a standpipe corer for sampling aquatic interstitial biotopes. Hydrobiologia 83: 257-260.
Williams, D. D., 1993. Nutrient and flow vector dynamics at the hyporheic/ groundwater interface and their effects on the interstitial fauna. Hydrobiologia 251: 185-198.
Williams, D. D. & T. Hamm, 2002. Insect community organisation in estuaries: the role of the physical environment. Ecography 25: 372-384.
Williams, D. D. & H. B. N. Hynes, 1974. The occurrence of benthos deep in the substratum of a stream. Freshwater Biology 4: 233- 256.
Williams, D. D. & N. E. Williams, 1998a. Seasonal variation, export dynamics and consumption of freshwater invertebrates in an estuarine environment. Estuarine, Coastal and Shelf Science 46: 393-410.
Williams, D. D. & N. E. Williams, 1998b. Aquatic insects in an estuarine environment: densities, distribution and salinity tolerance. Freshwater Biology 39: 411-421.
Yozzo, D. J. & R. J. Diaz, 1999. Tidal freshwater wetlands: invertebrate diversity, ecology, and functional significance. In Batzer, D. P., R. B. Rader, & S. A. Wissinger (eds), Invertebrates in Freshwater Wetlands of North America: Ecology and Management. John Wiley & Sons, Inc., New York: 889-918.
Ysebaert, T., P. Meire, D. Maes & J. Buijs, 1993. The benthic macrofauna along the estuarine gradient of the Schelde Estuary. Netherlands Journal of Aquatic Ecology 27: 327-341.
Ysebaert, T., D. Meire, J. Coosen & K. Essink, 1998. Zonation of intertidal macrobenthos in the estuaries of Schelde and Ems. Aquatic Ecology 32: 53-71.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Williams, D.D. The brackishwater hyporheic zone: invertebrate community structure across a novel ecotone. Hydrobiologia 510, 153–173 (2003). https://doi.org/10.1023/B:HYDR.0000008642.64116.8f
Issue Date:
DOI: https://doi.org/10.1023/B:HYDR.0000008642.64116.8f