Intertidal zone of Delaware Inlet,Nelson, New Zealand

Abstract

A study was made of Delaware Inlet (41° 10'S, 173° 26’ E), Nelson, New Zealand, during February—April 1976. The catchment contains sparse animal and human populations, and supplies unpolluted influent waters.

Over 90% of the inlet was intertidal, with surfaces of predominantly sand interspersed with mud, gravel, cobbles, and shell. Less than 10% of the sediments were colonised by macroscopic vegetation, principally Juncus spp. with Salicornia australis, Zostera muelleri, Viva lactuca and Enteromorpha spp. Two microscopic organisms (Euglena obtusa and Oscillatoria ornata) were studied. Dense aggregations of molluscs, particularly Amphibola crenata (mud snail) and Chione stutchburyi (cockle) were present in specific areas.

Salinity of the water fluctuated widely from <4‰ at the river mouth to 35.0‰ in the main channel at high tide. Nitrogen levels (N0₂‐N, NO₃‐N, NH₄‐N, Kjeldahl‐N) were determined on influent and waters of the inlet. For the main channel, levels of NO₃‐N, NH₄‐N and Kjeldahl‐N tended to be substantially higher around low water than at high tide; respective maxima and minima were 0.016 and 0.001 g.m^?3, 0.050 and 0.001 g.m^?3, and 0.35 and 0.10 g.m^?3. For water from river and streamlets, average levels of nitrogen components were similar to those for the main channel at low tide.