Cam and I collected water chemistry samples at locations along each of our three study watersheds, but this year water seems as difficult to “catch” as Arctic grayling were this spring. With ultra-dry conditions prevalent across most of Alaska, current water level and flow across our study area ranged from zero to low. While in some locations water flowed freely, in others we found only puddles, if anything at all, from which to draw water. These samples will help us determine fine-scale variation in water chemistry, specific to each location within each river system. You might wonder, “What does water chemistry have to do with fish?” Well, I’ll tell you… Fish have earbones called otoliths. Otoliths comprise layers of calcium carbonate, continually incorporating elements from the water that the fish is in over time. This chemical signal becomes permanently embedded in the otolith. So, as the water chemistry varies across the watershed, the otolith chemistry reflects that variation, allowing us to decipher past movement patterns of the fish throughout its lifetime. So cool!
This bag full of water samples represents the first step toward seeing our water chemistry data. I’ll need to acidify these samples back at the lab, then travel with them to the Woods Hole Oceanographic Institute for weeks of strontium reduction chemistry in the ultra-clean room, after which, I will finally run the samples on the mass spectrophotometer, a.k.a. the Neptune.
This otolith holds clues to fish movement from the birth of the fish to its demise. After prepping this earbone by carefully grinding and polishing to expose layers from core to edge, I will run chemical analyses by laser ablation under the mass spectrophotometer to collect a lifetime’s worth of chemically coded movement data.