From simple nets to high-tech tools as future environmental specialists sample the sea

A textbook is one thing – reality another. In the master's course ‘Environmental field studies’ students learn how to assess the marine environment in practice, using both simple and advanced methods.

– Waders, wellies or barefoot – the choice is yours!

The master's students in Environmental Science have brought their brail nets, buckets and identification literature to one of the rocky shores, rich in bladderwrack, close to the Askö Laboratory. The task is to find gravid amphipods whose eggs and embryos can be used as an indicator of the environmental state of the sea.

Some of the students slip into waders, others roll up their trousers and enter the water barefoot. They hand over equipment to each other, then fall silent, as they crouch over the water and net through the seaweed.

– Take the chance to look at the beautiful river nerites too, says Ann-Kristin Wiklund, researcher and director of studies at the Department of Environmental Science (ACES) at Stockholm University.

– We have used those small gastropods in previous studies to investigate the damage caused by toxic anti-fouling paints, she says.

 

Different stressors cause different types of damage

Earlier in the morning, the students gathered in the field station's lecture hall and learned about the advantages and difficulties of field studies, and about one of the sub-programmes in the environmental monitoring of the Baltic Sea, on the amphipods Monoporeia affinis and Pontoporeia femorata, which has been running since 1994.

The netting takes place at a rocky shore close to the field station. Photo: Michaela Lundell
The netting takes place at a rocky shore close to the field station. Photo: Michaela Lundell

After almost 30 years of sampling, the researchers now know which stress factors cause which damage to the animals: heavy metals and organic contaminants cause malformations of embryos, completely dead broods are often due to oxygen deficiency, and the brood size depends mainly on the temperature and availability of food.

The species used in environmental monitoring live in the bottom sediments, eat plankton that has settled, and are themselves important food for fish. But they only reproduce once a year – in the middle of winter. Now it's May, so the students are looking for other species from the same group of crustaceans, which live in shallow water among the bladderwrack and reproduce during the warm months of the year.

– Here are two of them, attached to each other! Which one is the female and which one is the male? a student asks.

The students examine their findings with scientist Ann-Kristin Wiklund. Photo: Michaela Lundell
The students examine their findings with scientist Ann-Kristin Wiklund. Photo: Michaela Lundell

They find amphipods of the genus Gammarus. In spring and summer, it is common to see them swimming around in pairs, with the larger male clinging to the female's back – waiting for her to moult (shed her skin). Only then can they mate, and to be sure to be there on time, the male holds on to the female for days beforehand. Gravid females carry their eggs on the ventral side of their body, like shrimp, and release them when the fully developed juveniles are a few days old.

 

Comparing with images in methodology study

After an hour at the shore, the students carry their catch to the field station's course laboratory. There follows the fine motor skills exercise to detach the eggs and embryos from the females, using tweezers and a needle.

– If you are careful, you can do it without harming the female, and then we can release her back into the sea afterwards, says Ann-Kristin.

Students examining embryonic development of amphipods at the Askö laboratory
At the field station’s course laboratory, the students examine the embryonic development of the amphipods. Photo: Michaela Lundell

The students look at the eggs through a stereo microscope and compare them with the images in the methodology study 'Malformations in embryos of the deposit-feeding amphipod Monoporeia affinis in the Baltic Sea'. The embryonic development is the same for all amphipods.

– Look, here are the embryos in stage E-F, the different body parts are developing already! says one student and shows the others.

 

Sampling the seabed

Meanwhile, at sea on board the high-tech research vessel Electra af Askö, the second half of the course group is learning about the seabed and how to sample sediments to analyse the levels of oxygen, nutrients and various pollutants.

Professor Christoph Humborg and postdoctoral research fellow Martijn Hermans from the Baltic Sea Centre demonstrate how to collect sediment cores and then extract pore water from different layers of the core using Rhizon samplers.

Professor Christoph Humborg shows how pore water is sampled from different layers of the sediment core with Rhizon samplers. Photo: Michaela Lundell

They have collected two cores from a depth of 48 meters.

– Sediment cores are like archives that can tell us about the environmental conditions of the seabed in the past, such as the availability of oxygen. Here you can see a light layer, where we have iron that has oxidised to iron oxides, says Martijn Hermans.

– And here we have a darker layer – this indicates iron monosulphide, which is formed in oxygen-free conditions.

– You can also measure the amount of methane gas, which is important to monitor because it is such a powerful greenhouse gas. As long as the methane is in the sediment or in the water, it can be oxidised by bacteria and archaea. But any methane that bubbles up to the surface of the sea and reaches the atmosphere contributes to the greenhouse effect. There are no bacteria in the air that can metabolise methane, explains Martijn Hermans.

Reserachers show sediment cores on the aft deck of research vessel Electra af Askö
Postdoctoral fellow Martijn Hermans (left) och professor Christoph Humborg (right) from the Baltic Sea Centre show one of the sediment cores collected from the seafloor at a depth of 48 metres. Photo: Michaela Lundell

The reality is different

The students of this master's course in environmental field studies come from several different countries, with different study backgrounds and ideas about what they want to do in their professional life.

Despoina Kouvousi from Greece wants to ‘turn waste into gold’, making people value waste instead of polluting the world with it. Gian Waldinsperger from Switzerland wants to create a collective cultural house for ‘social transformation’ of people's values and behaviour. Molly Jansson from Sweden wants to work with pollution analysis, either as a scientist or in a municipality.

– It is good to do field studies and see different environments with your own eyes, says Molly Jansson. In pictures in course books things can look very neat and tidy – the reality is different.

– Even for an environmental specialist who will mostly work with numbers and modelling, it is important to understand how data are obtained, says Ann-Kristin Wiklund.

– And that both very advanced and very simple methods are used. As an environmental consultant, you have to be prepared to do field work and conduct different types of sampling.
 

Students try to find amphipods in bucket by the shore. Askö laboratory
The task is to find gravid amphipods, but students take the chance to study other species of the Baltic Sea as well. Photo: Michaela Lundell

Environmental Field Studies is a master’s course at the Department of Environmental Science, that combines hands-on experience with advanced techniques, preparing students to design, plan and execute field investigations and draw nuanced interpretations and conclusions from the data. The course includes two days at the Askö laboratory.
 

Read more about the course

Read more about the Askö laboratory 

Text: Michaela Lundell