Some­thing in the wa­ter

Marlborough Express - The Saturday Express, Marlborough - - GARDENING - MAIKE VAN DER HEIDE

Un­der the Wairau Plain, within the tiny pores of our aquifers, lives a sub­ter­ranean colony of blind, colour­less and, for hu­mans, largely mys­te­ri­ous crea­tures.

The mi­nus­cule in­ver­te­brates, rang­ing from less than 1mm to 8mm in size, are rarely seen, but may in fu­ture play a big part in un­der­stand­ing the health of Marl­bor­ough’s aquifers.

Marl­bor­ough District Coun­cil ground­wa­ter sci­en­tist Peter David­son says the in­ver­te­brates respire and feed on or­ganic mat­ters, ‘‘so if there’s waste com­ing down from the sur­face then the ben­e­fit for us as hu­mans is that they prob­a­bly tidy that for us’’.

In his book Ground­wa­ters of Marl­bor­ough (2011), Peter wrote that the crea­tures are ‘‘po­ten­tially bio-in­di­ca­tors of aquifer wa­ter qual­ity and in­di­rectly the im­pacts of over­ly­ing land-uses.’’

They were first dis­cov­ered in New Zealand in the 1880s, but their func­tion is largely un­known. ’’To man­age them and know what to do with them we need more knowl­edge. It’s fas­ci­nat­ing that there’s a whole com­mu­nity of life there.’’

Peter says sci­en­tists agree there is a need for a New Zealand-wide bench­mark study about the in­ver­te­brates to dis­cover what they can tell us about the state of, and hu­man im­pact on, our aquifers and water­ways.

A na­tional ini­tia­tive is un­der­way to seek fund­ing for such a study across New Zealand’s ma­jor eco­nomic aquifers, in­clud­ing Marl­bor­ough, but this was in the ini­tial stages, says Peter.

What is known is that the in­ver­te­brates are present in the tran­si­tional zones be­tween aquifers and spring-fed streams, as some have been found in stream sam­ples, and past stud­ies have iden­ti­fied about a dozen different species in Marl­bor­ough, though there are likely more.

Peter says the in­ver­te­brates are most likely to be found in porous grav­els which ex­ist northwest of Ren­wick, and less likely to­wards the coast of the lower Wairau Plains where the aquifer is deeper and there is less oxy­gen and food.

Coun­cil fresh­wa­ter ecol­o­gist Peter Hamill hap­pened upon some of the in­ver­te­brates a few years ago when they blocked up a landowner’s well­wa­ter fil­ter. Many look like tiny white or trans­par­ent sand­hop­pers.

The chal­lenge to study­ing the in­ver­te­brates was re­triev­ing them from a well with­out the pump mush­ing them up like the fil­ter had, which re­quired spe­cial­ist equip­ment that only went to a cer­tain depth in the ground, he says.

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