• Dr. Pedro Nogueira

to the North Sea and the Baltic Sea


Walther Herwig III, sea blog of the 411th cruise

Duration: December 1 to 18, 2017

Survey area: North Sea and Baltic Sea

Purpose: Investigations on fish diseases and biological effects of pollutants / Projects PlasM and DAIMON

Fahrtleiter: Dr. Pedro Nogueira, Thünen Institute of Fisheries Ecology

After two days waiting for a new steward we left Bremerhaven at 7 am, leaving our new institute and the shoreline behind. We started off towards our first area of interest, GB1, located south of Helgoland. At 1 pm we got our first haul. We were somehow disappointed to see that we only caught very few of the desired dab (the reference fish used for monitoring of biological effects). The second haul provided a similar result. Looking for a more successful catch, we moved on to the area N01, where we got our last haul of the day. This haul revealed itself very successful with a great number of dabs and after three hours we managed to analyze our 250 dabs. Finally, around 9 pm we got to rest, after an exciting first day at sea.

++Dec. 2, 2017++ Skagerrak

After steaming all night northwards along the Danish cost we arrived at the Skagerrak and entered the Baltic See.

At 3:30 pm during the safety training in form of a test fire alarm, we were instructed how to savely leave our chamber, put on the life jackets, dress ourselves with survival suits and what to do if we had to leave the ship in case of an emergency.

At 9 am sharp, we arrived to our destination, the first sampling site in the Baltic Sea, B01. We cast our net and hoped for a good catch. In parallel to our regular fishing activities we deployed a Neuston Net for sampling of planktonic particles that will be used for shore-based analyses of microplastics at the sea surface in the areas visited during the cruise. 

PhD-student Ivo Int-Veen reports:

> Neuston Net / Microplastics

In addition to our fish samples, we sampled fish for investigation of microplastics inside the organisms. Microplastics, leftovers of our disposable society, are small plastic particles (< 5mm). In general, microplastics are distinguished in primary and secondary microplastics, where the first ones are manufactured in microscopic size and find application in personal care products or as raw pellets for production of plastic materials. Secondary microplastics are the product of fragmentation of bigger plastic items in the natural environment. Transported by the wind or rivers, most plastic waste ends up in the oceans. Here, it accumulates and persists for a very long time. While larger plastic pieces cause obvious harm to marine wildlife like entanglement or suffocation, the microplastics are considered an “invisible” threat for marine animals. A broad range of organisms is susceptible to misinterpret microplastics as prey, followed by blockages of the digestive tracts, false feelings of satiation and other health problems. Additionally, microplastics are considered a vector for various toxicants into marine organisms. Microplastics and associated toxins are subject to bioaccumulation within the food web and across trophic levels. Therefore, fishes are especially threatened by these contaminants.

In order to investigate the amount and consequences of the uptake of microplastics by different fish species, we collect fish samples for the PlasM project. In the laboratory on shore the digestive tracts of all fish specimens will be screened for microplastic and their health condition will be ascertained.

To gain a more holistic view about the microplastic pollution of the Baltic Sea and the North Sea, we were also sampling planktonic samples with a Neuston Net. The gear is trawled for 15 minutes at the water surface and catches all pelagic particles larger than 300 µm. In the shore-based laboratory these samples will be screened and analyzed to investigate the abundance and composition of microplastics in the surface waters of the sampling areas.

++Dec. 4, 2017++ Fishing lines

Upon our arrival to B13 close to Bornholm, an area known to yield excessive amounts of dumped munitions at the seafloor, we were surprised to observe that a fishing boat had placed its salmon fishing lines directly across the dumpsite. Since, in this area is only a restriction for bottom trawling apply, they were fishing legally in this area, despite of the potential assimilation of toxic explosive substances in the fish around here. The lines are several nautical miles in length and stay at the surface of the sea slowly drifting, where they are a threat to boats crossing, since, they may block the propellers. As a result, we were forced to fish only in the northernmost part of the area of interest and to cancel our plan for conducting an echo sounder survey during the night.

After dinner the decision was taken to head towards the next significant area for our expedition, B14 in the Gotland Basin.

Nadine Goldenstein reports:

> Hydroacoutstic Survey of munition dump sites

The CTD-Rosette is used to measure the conductivity, temperature, and pressure of seawater (© Pedro Nogueira/Thünen-Institut)

Two areas of investigation were associated with munition-dumpsites, a German heritage from the days after WW II. The detonators are nowadays corroding at the seafloor, slowly releasing their toxic explosives into the Sea. Dissolved in seawater, compounds like Trinitrotoluene (TNT) enter the marine ecosystem and the fish organism via respiration and nutrition. To investigate the behavioural adaptation of fish present at the dumpsites, we monitor their migration in the water column via single-fish tracking.

Unfortunately, upon arrival in our first survey area north-east of Bornholm, on December 4th, our target coordinates were not in reach due to salmon-fishery nets stationary deployed in the water column. Hence, we decided to head further east to the Gotland Basin, our second site of investigation affected by sunken munitions. Here, we conducted a comprehensive hydroacoustic survey, on December 5th. In addition, hydrographic data were acquired at the four outermost points of the survey as well as at the central intersection. Hydrographic sensor profiles included conductivity, temperature, pressure (CTD) as well as dissolved oxygen, pH, turbidity as well as fluorescence. Further, seawater was sampled at the eastern most site of the survey below and above the thermocline, as well as in the upper water column. Based on these data, the scientific team around chief scientist Pedro Nogueira hopes to gain a conclusive picture of the prevailing conditions and to understand how the presence of toxic chemical warfare agents might alter the oceanic habitat in this part of the Baltic Sea.

++Dec. 5, 2017++ Gotland deep

Finally, we arrived at the deepest part of the Baltic Sea. This area was the first dumpsite for chemical warfare agents created during the disarming of Germany after WW II. However, due to expensive costs for transportation, this site was dropped early on and B13 close to Bornholm became the major dumpsite for munitions in the Baltic Sea.

Our goal in this area was to collect cod samples for genetic analyses, the major research interest of PhD-student Peggy Weist. In addition, we collected sediments samples, using a Van Veen grab provided by the Alfred Wegener Institute (AWI). The sediments will be investigated by Michal Czub (IOPAS Poland). After three hauls and three bagger grabs, we had fulfilled our objectives and continued to polish waters. What we did not expect was that a storm was rising.

PhD-student Peggy Weist reports:

> Mixing dynamics of Baltic cod

In the Baltic Sea two distinct cod stocks occur. The western Baltic cod stock which is the smaller stock inhabits the waters of Kiel Bight and the Belt Seas. The larger stock of the eastern Baltic cod can be found in the areas east of Bornholm. However, it has long been suggested that both stocks mix in the transition area, the Arkona Sea, while it was not clear to what extent individuals of both stocks mix. Our project is embedded in the European Data Collection Framework and aims to get a solid understanding of mixing dynamics of western and eastern Baltic cod.

During this cruise, we caught cod in different areas of the Baltic Sea and took tissue samples and otoliths (auditory stones) from each individual. Later in the shore-based laboratory, we will be able to assign individuals to their population of origin using genetics and otolith shape analysis. Our results will help to improve future Baltic cod management plans.

Michal Czub, IOPAS Poland, reports:

> Sediment sampling at the Gotland Deep reference dumpsite

During our cruise we got the possibility to collect scientific material at a station that was selected as a reference site for chemical warfare dumpsites. Sediment samples were collected at a station in the Gotland Deep with three Van Veen grab casts. Sediment was divided into five subsamples for Mercury and Arsenic pore water analyses, four subsamples for measurements of chemical warefare agent concentrations and nine subsamples for taxonomical analyses of meio- and infauna. Samples for meiofaunal analyses were preserved with 70% ethanol, while the remaining material was stored frozen. Analyses of the sediments will be performed in IOPAS, MUT, VERIFIN and University of Gdańsk.

++Dec. 6, 2017++ Seasickness

After a rough night with waves up to 3 meters and westerly winds up to 8 Bft we arrived at the B09 area in polish waters. On that day, only few of us were hungry upon arrival at the breakfast table. Approximately half of the scientific crew showed symptoms of seasickness, like tiredness, dizziness and serious headaches.

This day was also marked by unsuccessful catches. After four hauls we only had caught 29 cods. Consequently, we decided to stay overnight for another half day and two additional catches as well as a more quiet night to get some rest and recover.

Leonie Breidenbach, student of the University of Bielefeld, reports:

> Seekrankheit (in German)

Seekrank zu sein ist wahrlich keine Freude! Am ersten Tag unserer Reise merkte ich noch nichts, da die See sehr ruhig war. Doch bereits in der zweiten Nacht auf See wurde das Schaukeln stärker und wuchs zu einem Schwanken heran. Im Liegen merkte ich noch nichts, doch als ich aufstehen wollte wurde mir so schwindelig, dass ich mich auf den Boden legen musste um nicht umzukippen. Den ganzen Tag über hatte ich Druck auf dem Kopf, mir war übel und schwindelig. Nach Einnahme eines Medikaments wurde ich müde und legte mich zum Schlafen hin. Als es auch nach zwei Stunden Schlaf nicht besser war, beschloss ich, dass Ablenkung bestimmt gut täte. Also ging ich auf das Arbeitsdeck und half bei drei Hols mit. Auch die nächsten Tage fühlte ich mich elend, nur zum Abend hin wurde es etwas besser.

Seekrank zu sein ist ziemlich unangenehm, gerade weil es auch auf die Psyche schlägt. Man fühlt sich müde und antriebslos, selbst Gespräche am Tisch sind anstrengend. Das konnte man auch in der Messe beim Essen feststellen: Je mehr es schwankte, desto weniger wurde sich unterhalten. Meine Bilanz: Zur See zu fahren macht Spaß, bis es schwankt und die Seekrankrankheit einem alle Energie raubt.

++Dec. 7, 2017++ Walther Herwig III and Storm Walter

Herrings for analyses in the radio-ecology department of the Thünen Institut (© Pedro Nogueira/Thünen-Institut)

Our last try to catch the missing cod for genetic analyses, the 6 kg muscle for analyses in the radio-ecology department of the Thünen Institute and the 100 cod for the disease survey, consisted of three new hauls this morning. Around noon we started our journey to the West fighting against westerly winds up to 9 Bft and waves of 3.3 m height. We were directly heading towards the storm “Walter”.

++Dec. 8, 2017++ Arkona Sea

Early morning, chief scientist Pedro Nogueira received good news from the first officer: the weather had changed in our favor and we had made great progress during the night steaming towards B11 in the Arkona Sea. Luckily, the westerly winds had shifted, now blowing from the south-west. Hence, our close proximity to land protected us from the major effects of the bad weather. On this day, we were able to quickly fulfill our sample requirements what helped to light up everyone’s mood after sickness and misfortunate catch.

++Dec. 9, 2017++ Cleaning fire

On our way to Kiel we took a stop at Mecklenburg Bay (B12) to collect additional samples from this area. Before entering the harbor, we cleaned the laboratories and the work-deck with detergent and hot water, as required. Suddenly, the fire alarm went on and the crew ran up and down all floors, eager to find the fire. But no fire was to be found! After a close inspection, the first officer found out that the hot water condensation on the walls and ceilings of the work-deck had activated one of the smoke detectors. Relieved, knowing to be safe we continued cleaning and preparing for the Christmas party.

++Dec. 10, 2017++ Stop-over in Kiel

The arrival to Kiel marked the end of the Baltic Sea part of the expedition and went along with having to say goodbye to two of our scientific crew members: Peggy Weist and Michal Czub, the polish observer. After a short visit at the Kiel Christmas market with an icy wind blowing thick snowflakes into our faces, we returned to the warmth and safety of the Walther Herwig III. Once again, we had to spend another night in the harbor due to an exchange of personnel with our new steward arriving on the next day.

++Dec. 11, 2017++ Ship mail

This morning our colleague Klaus Wysujack arrived, who was taking the vacant spot left in the scientific team. We were happy to get again another helping hand on board and Klaus was eager to identify his first dub and to get hands on experience in addressing fish-diseases for our monitoring program. Before departure, we managed to get some postcards written and to send them off via the ship-mail. Then we started off, steaming towards the North Sea, again crossing the Skagerrak.

++Dec. 12, 2017++ Skagerrak by day

Today, we continued our long journey towards our northernmost sampling site in the North Sea, heading again towards rough weather, accompanied by the comparably long waves beginning to swell once again as we steamed westwards.

++Dec. 13, 2017++ marine litter

Marine litter: old rubber boot overgrown by a variety of marine organisms (© Nadine Goldenstein/Thünen-Institut)

We returned to our fishing activities in the North Sea area P02. This area is known for its oil platforms and is the most remote location in our survey within the North Sea. However, due to the anthropogenic activities in the area characterized by oil-platforms and ocean fishing, we encountered considerable amounts of marine litter in our catches. Among the items we found was an old rubber boot, all overgrown with algae and barnacles.

PhD-student Ivo Int-Veen reports:

> Marine litter

Environmental pollution is one of the most urgent manmade threats for natural ecosystems. In order to monitor the abundance and composition of marine litter in our sampling areas, every haul conducted by the Thünen Institue for Fishery Ecology is screened for anthropogenic leftovers. We are following the International Bottom Trawl Survey (IBTS) procedure of the International Council for the Exploration of the Sea (ICES). They established a system in which marine litter is categorized according to its source, previous usage, size and weight, which is applied since about 1970 to harmonize different sampling approaches in marine sciences. Every item is categorized, photographed and listed in the ICBT protocol. In the labs the specific materials will be identified and the results uploaded to an international data collection of marine litter.

So far the range of collected items ranged from fishing lines, fishing nets, plastic bags and processed wood to socks, shoes and rubber boots. We will continue fishing for litter – wondering what oddities of the human waste generation are awaiting us in the upcoming sampling areas.

++Dec. 14, 2017++ Ordinary working day

A day of regular fishing and sampling activities at GB4, half-way on our transect back towards Bremerhaven.

++Dec. 15, 2017++ New Problems

The day started with some bad news: a fishing boat had placed its fishing lines over the north part of our area of interest, thus limiting us to fish only considerably small part of N11. Luckily, the first haul revealed very successful, as we caught almost all dabs we needed for the analyses. As we were setting the net for the second haul the captain aborted the catch immediately as he found out that new lines had been placed now also covering the southern part of our sampling area. After a quick chat with the fishing boat we got the positions of the newly placed lines and it was immediately clear that no more fishing was possible for us in this area. In syncopation we decided to move on to GB3 and continued fishing in the afternoon.

++Dec. 18, 2017++ Home sweet home

After two successful days, we completed the remaining areas of interest in the North Sea and returned to our initial position at the beginning of the journey, GB1. After having achieved all our objectives and it was time to clean the labs and working spaces on board. Therefore, we took a sheltered position in the Weser estuary and prepared to leave the vessel. We are excited to get home in a days’ time.