New Zealand Journal of Marine and Freshwater Research abstracts

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Influence of hydrologic exchange patterns on water chemistry and hyporheic invertebrate communities in three gravel-bed rivers

Reece T. Fowler^1*
Mike R. Scarsbrook²

¹Institute of Natural Resources-Ecology
Massey University
Private Bag 11 222
Palmerston North, New Zealand
²National Institute of Water and Atmospheric Research Limited
P.O. Box 11 115
Hamilton, New Zealand
*Present address: Kingett Mitchell Limited, P.O. Box 33 849, Takapuna, Auckland, New Zealand. email: rfowler@kma.co.nz

Abstract   The influence of hydraulic exchange patterns on hyporheic water chemistry and invertebrate community composition was measured in three gravel-bed rivers of southern Hawke’s Bay, North Island, New Zealand. Based on patterns reported overseas we predict that down-welling waters will be similar to surface waters in chemical characteristics and epigean animals will be more common in down-welling waters than in up-wellings, which would have a different chemical signature to the surface waters and a fauna dominated by hypogean invertebrates. Conductivity, pH, and temperature of hyporheic water were least like those of surface waters at up-wellings in the groundwater-fed Makaretu River. Only 6% of the invertebrate fauna of these up-wellings comprised epigean animals. In contrast, in the groundwater-recharging Tukituki and Waipawa Rivers, hyporheic water chemistry was similar to that of surface water in down-wellings and 40% of the community comprised epigean animals by abundance. Significant increases (P < 0.05) in species diversity and taxonomic richness was also identified in down-welling zones compared with up-wellings. Species diversity and taxonomic richness were lowest in up-wellings in the Makaretu where hypogean animals dominated the hyporheic fauna. Species diversity and taxonomic richness were higher in down-wellings than up-wellings because more epigean taxa were present.

Keywords   down-welling; epigean taxa; groundwater; hydrology; hypogean taxa; hyporheic zone; hyporheos; piezometer; subsurface; up-welling; water chemistry

M01084 Received 17 October 2001; accepted 3 January 2002; published 17 September 2002
New Zealand Journal of Marine and Freshwater Research, 2002, Vol. 36: 471-482 0028-8330/02/3603-0471 $7.00 © The Royal Society of New Zealand 2002

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