How we do it: Species identification

No matter how carefully you look, many of the aquatic flora species can’t be identified by naked eyes only. Some of the specific identification characteristics have to be looked at with a microscope. If you want to identify for example a water moss Oxyrrhyncium speciosum, you have to look at the edges of the leaves – are they serrated (saw-like) or not. Or if you want to identify a filamentous algae Ulothrix zonata, you have to look at the cell structure inside the algal filaments.

Oxyrrhyncium speciosum, photo by Essi Keskinen, Metsähallitus.

Some of the characteristics can already be seen with a field magnifying glass (for example the stipuloids in the various species of Charales). If this doesn’t work, and the species can’t be identified in the field, we take a sample.

Plant sample under a microscope, photo by Essi Keskinen, Metsähallitus,

Marine biologists at Metsähallitus are a huge user of plastic zip-lock bags. Unfortunately, we can’t use anything more environmentally friendly because the bags have to close properly to hold water and the sample and they have to be made of a material, where the sample doesn’t stick to. Also, they have to go into a small space (the pockets of the survival suit) when they don’t contain a sample yet. This pretty much leaves us to play with different brands of zip-lock bags. So far, the double zip-lock ones that Ikea sells seem the best for the purpose. For field inventories done with scuba diving, we use hard plastic containers with lids, or old-fashioned camera film containers. But the good thing is that we use these plastic bags and containers again and again, Summer after Summer.

Sample bags drying at the office after use. Photo by Essi Keskinen, Metsähallitus.

We mark each bag with a number or a letter combination, for example “A1” and then in the field when we’re taking the sample, we mark “A1” to the field paper in the correct place to indicate that a sample was taken from this specific point.

Marking the identified species to field paper. Photo by Essi Keskinen, Metsähallitus.

Then, back at the office or in the field accommodation, we start the task of microscopying each and every sample taken in the field. We use a dozen or so identification books for different species (one for water mosses, two or three for vascular plants, two for Charales, two for algae) and try to do our best. If our best isn’t enough and we can’t get the species identification solved, we store the sample and turn to real experts.

Microscoping at the research station in Ulkokrunni. Photo by Essi Keskinen, Metsähallitus.

The real experts are taxonomists who have been studying various groups of flora, sometimes for decades. We usually find them at the universities and natural history museums. Some of them are emeritus professors, who have been working on taxonomy since the 1960s. One of these specialists in Finland is an emeritus professor Tauno Ulvinen, 90 years old, at the University of Oulu Botanical museum. If we have anything to ask about weird water mosses, we turn to Prof. Ulvinen. When we can’t identify a Charophyte, we send it to Senior Museum Technician Marja Koistinen at Natural History Museum. Etc etc. We have different experts for each group of macrophytes.

Emeritus professor Tauno Ulvinen checking our water moss samples. Photo by Essi Keskinen, Metsähallitus.

When the answer gets back to us, it’s sometimes very frustrating to find out that it was the same species that we are always unable to identify. Sometimes we get a pleasant or an exciting surprise and find out that we found a species which we haven’t found before or which wasn’t previously known from the area.

Of course, most of the species can be identified right then and there in the field, underwater or at the shoreline. It’s the ones that we have to take a sample of that will consume so much of our time after returning from the field.

Chara aspera, photo by Essi Keskinen, Metsähallitus.

Written by Essi Keskinen, Metsähallitus

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