By Kate H (guest blogger)

Catalina Island is a foraminiferal hub, located 35 km south-southwest off the coast of LA, California. The island is pretty spectacular to take in, it consists of metamorphic schists intruded and overlain by volcanics, all uplifted from the seafloor. At first the island was first used for smuggling, hunting and gold digging but then was developed into a tourist (and later scientific) destination by William Wrigley Jr (founder of the gum).

Catalina Island is ideal for culturing foraminifera as the continental shelves are quite narrow and drop off steeply into the ocean basin. This means that we can quickly and easily reach the deep water habitat that the planktonic forams love to live in.

A typical day ‘at work’ on the island involves blue water scuba diving for planktonic foraminifers at 5-10 meters depth. When forams are alive with their spines they are very easy to see compared to the shells most people are used to seeing in sediment cores.

Foram finders hard at work - picture thanks to Bärbel Hönisch!
Foram finders hard at work – picture thanks to Bärbel Hönisch!

Blue water diving can be quite dangerous (not only for the sharks that enjoy said blue waters) but also for keeping track of what depth you are at in such a vast expanse of blue. For safety we are tethered to a trapeze (the ropes in the picture) which are attached to a boat. Also attached to the boat are collection bags. The top bag has jars full of seawater which we take, collect forams into, and then put into the lower bag. We collect about 100 foraminifers in a dive to them to the lab to measure and experiment on. We measure and observe them before putting them in experimental seawater, so that we know exactly how much they’ve grown in the lab by the end of the experiment. Every second day we feed our forams brine shrimp (AKA sea monkeys), which is strangely satisfying.

ForamForams have a sticky rhizopodia which ‘streams’ up and down their spines, which you can sort of make out in the picture of a foram feasting on a brine shrimp. The rhizopodia is used for nutrient/waste transport into and out of their central cell inside the shell. The rhizopodia is very sticky, which makes them very good passive predators, as well as dangerous when stuck to or caught up in a pipette (rendering both the foram and pipettor unhappy).

Forams typically live for a week or two in culture and end their life cycle by expelling their gametes, leaving an empty shell for us to take back to the ANU for isoptoic and trace element analysis.

There is a very enjoyable youtube about the whole process: