Andi filtering water over pre-weighed filters for particular matter analysis to compare the turbidity of our sites
Pre-weighed GF/F filters
Preparing for nutrient analysis – a calibration for nitrate which is a key nutrient to indicate anthropogenic input
The transition from fieldwork into a laboratory is an interesting one; from days baking in the sun (or soaking in the rain) filled with carrying tanks and diving gear, spending hours underwater and living in a wetsuit to days sitting in a lab, wearing a lab coat, dealing with corrosive chemicals and handling precise and delicate equipment… One of the strangest transitions for me is that from never wearing shoes to wearing safe ‘close-toed’ shoes!
During our fieldwork, at each site that we visited, Andreas Eich (Andi) and myself collected water samples for particulate matter (PM) analysis (both to measure turbidity and for later C/N ratio analysis which indicates nutrient input) and chlorophyll a, as well as filtered water for nutrient analysis. Each time we collected water for PM and chlorophyll a, the hours following the dive are spent filtering water with a vacuum pump over pre-weighed GF/F filters which can prove challenging when dealing with Suva’s many powercuts… We also collected algal leaves from Lobophora and Padina spp. to investigate the concentration of phlorotannins; similar to the tannins which give the dry feeling in the mouth when you drink red wine, but these are specifically produced by macroalgae and have been found to deter fish from feeding. Part of Andi’s project is to investigate which factors influence the production of these phenolic compounds.
Since Christmas, the two of us have therefore been spending half of our time in the lab with the much-appreciated support of the University of the South Pacific’s Chemistry Department. Ideally, the nutrient analysis would have started earlier but of course ordering the hazardous chemicals to Fiji that we could not bring ourselves has been a very long procedure… Luckily the final chemicals cleared customs two days before Christmas so at least a few weeks before the end of our trip! Typically, the first day we wanted to start our nutrient calibrations the photometer that we shipped from Bremen decided that although it worked when we arrived it no longer wanted to cooperate, and thus the Chemistry Department again saved the day and provided us access to their equipment.
We are gradually working our way through all of the samples with the ongoing and gratefully-received support from Matthais Birkicht back home at ZMT. Although we have both had to extend our stays, for Andi now there are just a few hard days left, and for myself a couple more weeks to wrap up this very productive field session in Fiji!