Sampling Trips

Invertebrate Sampling 12/09/2017

What a cold, grey day! But that didn’t stop the teams from Otago Girls’ and John McGlashan heading out into the chilly lower lagoon to collect pelagic (in the water column) and benthic (in/on the sediment) samples of macroinvertebrates from their sites.

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What can these tell us about the health of the Lagoon? Freshwater invertebrate taxa (groups of species) have been found to have different tolerance levels to pollution such as excessive nutrients, so their presence or absence (and in some cases abundance) is often used in rivers to give an idea of the probable pollution level and therefore the water quality. Scientists call this the Macroinvertebrate Community Index (MCI), and it works by using a number or ‘score’ that scientists have assigned to each taxa based on their tolerance, and this score is simply added up for all of the taxa found.
It’s slightly more complex in Tomahawk Lagoon unfortunately, being a brackish lake that’s often quite salty from seawater, so it is unknown just how accurate these macroinvertebrates will be at indicating water quality.. But it’s worth having a dig around to see.
We can also use our macroinvertebrate findings to give us insights into the foodweb in the lagoon- we are basically finding what the fish eat. We’ll build up a foodweb based on our sampling trips and post it here soon.. stay tuned 🙂