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Environmental forensics

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In this interactive click on Candida to learn more about environmental forensics in the marine environment. Follow her to look for clues in the estuary and when you’re ready click on the research vessel to move to the fiords.



We just were interested in seeing the connection of… if we change our practices on land, what are the knock-on effects for the ecology of these systems that are downstream? I like to call it environmental forensics because we’re trying to understand changes in the environment using a whole suite of different clues.

Seaweed sampling

We sample several different levels of the food chain as well as actual water column samples. So we sample nutrients from the water column, which tells us how much nitrogen is in the system, how much phosphorus. We’re also interested in seaweeds, which are the primary producers of the ecosystems. The seaweeds are largely sampling the environment for us all the time. They are growing in this water and so they are basically sucking up those nutrients and reflecting the light conditions as well. And so by sampling those seaweeds, we can tell a little bit about what the nutrient conditions have been like over longer periods of time than just from the water column.

Chemical markers

DR CANDIDA SAVAGE Trying to quantify and show direct linkages between land use and the ecological changes is really difficult, and that’s something that is probably the largest or the biggest challenge that we have to deal with. But there are certain key changes that we can look for, and we often rely on chemical signatures in these organisms, so we’ll look for particular chemical signatures or markers inside the seaweeds and the bivalves and in the fish. And we also have to back that up with experiments that we do in the laboratory setting. We've seen that, if we look at their gut content and if we look at chemical signatures that are carried in these fish, we see the fish that are occurring in the more pristine estuaries tend to have a much wider range of food sources that they can eat. The ones that are occurring in the more impacted areas tend to have a narrower group of organisms that they can eat.

Phytoplankton clues

In terms of phytoplankton, they not only are at the base of the food web and so important for everything else in ecology, but they also respond quite rapidly to changes in environmental conditions. And there are a suite of different species of phytoplankton which have different tolerances. So by looking at the groups of phytoplankton that we have, we can try and see if there has been changes in salinity, for instance, changes in the light environment and also changes in nutrient availability. So they are also sampling the water column for us and telling us what conditions were like when they were growing there because of their narrow tolerances.

Sediment cores

We don't have the luxury of having data that goes back 100 years or more, and we don't often have the data that goes back 10 years, so we try and reconstruct the situation that was present using what I call environmental forensics, so basically trying to use records that are preserved in sediments. It’s the same idea as using tree rings on land and also using the ice records down in the Antarctic. So we’ll take a core that’s about a metre long, which we take from the boat, and then we basically section that core down the middle and we sample through time. And basically over time, naturally the phytoplankton have been settling down to the sea bed and being preserved there. And so what we can do is section back through time, and we can try and reconstruct changes in that phytoplankton over a 100-year or 200-year time period. And some phytoplankton are preserved whole. Those that dissolve basically and disintegrate, they leave behind chemical markers that will tell us which groups of phytoplankton were there in the water column previously.