Marine biological excursion in Tarifa

Text: Gina Birrer; Photos: Gina and Dr. Jürgen Holm

In the early summer of 2018, a group of students from the University of Basel set off for Tarifa to get to know marine biology characteristics on the coast and in the Strait of Gibraltar.

Again, the annual excursion was awaited with excitement and anticipation. Already the trip through Spain offered various impressions regarding the climatic conditions. The weather at the east coast of Spain promised summer feeling with oppressive heat. The contrast of the temperatures in comparison to Tarifa itself was impressive. The Atlantic made itself noticeable there, because the air was moved by the thermals and was pleasantly fresh. As was already communicated before the excursion, Tarifa, the southernmost city in Europe, is very interesting due to its climatic and geographical conditions. The Strait of Gibraltar forms the inflow and outflow of the Mediterranean Sea to the Atlantic Ocean. The associated currents between the Atlantic and the Mediterranean lead to complicated, fascinating and interesting peculiarities.

The flora and fauna in the Strait was discussed in more detail during the marine biology excursion. The morning program in the first days consisted of presentations of the excursion participants on plankton distribution and ocean acidification, underwater noise, traditional tuna fishing, whale watching and other topics as well as lectures by Prof. Dr. Holm on the interstitial fauna of the marine sands and the occurring fish species. On the third day Katharina Heyer told about her foundation firmm and documented everything with pictures and Videos.

Exploring the littoral Zone

Actually, practical learning content should also be in the foreground. Due to the Levante, the east wind known in Tarifa, which began on the day of arrival, trips to the sea were not possible during the first five days of the course. Of course the kitesurfers enjoyed these conditions, while we set off after the morning lectures to explore the littoral. Marine biology can also be studied in the coastal zone of the sea, because the changing conditions due to topography and tides provide a great zoological diversity. The qualitative inspection of the littoral was relatively flexible and the students were able to follow their curiosity and desire to discover. Interesting sightings and catches were made, such as a nudibranch, sea cucumbers, many crabs and shells.

The field binocular helped to visualize even small creatures or peculiarities of the larger Fauna.The quantitative littoral, i.e. the collection of data in the littoral according to a scheme, was more adventurous however, as the high tide could not be avoided. The aim was to record and count the organisms in the given littoral zoning. For this purpose, the specific organisms in the individual quadrants were counted and thereby a diagram of the occurrence of organisms and the environmental conditions was created.The examined littoral was on the Mediterranean side of the Strait, as the following picture shows.

Plankton samples and fish market

So, thanks to the wind, during the first few days we were only busy along the Strait of Gibraltar, but not yet with the creatures in the open sea. After a few days the students were almost impatiently awaiting the investigations and experiences during the trips with firmm.

Plankton samples could for the time being only be taken in the harbour and then they were examined in the beautiful apartments near the city centre, which served as accommodation. To see the incredible variety under the microscope with one's own eyes was very impressive.Hundreds of different structures and creatures were visible. In addition to the plankton samples also samples of the interstitial fauna of the marine sands were taken, and shells and foraminifera were determined and drawn. Also here, there is an unbelievable variety available, which one cannot imagine straight away. The identification books helped to find one's way around the genera and species. The sketch-like depiction of the discovered living beings helped to focus on important characteristics.Visits to the fish market were also announced. There the different fish species could be determined - in Spanish as well as in German and English. The fishermen were very helpful and were happy to tell us about their catches.

 

Whale watching with firmm

On the 6th day it was finally time. The Levante was calming down and we were able to make trips to the Strait of Gibraltar. Several trips per day were planned. The few hours were overwhelming. Although the first 45 minutes of the first tour were full of hope and waiting, we were rewarded for the rest of the time. During all trips pilot whale groups - partly also with young whales, and Sperm whales and their impressive flukes rising out of the water when diving down, were sighted! Altogether we had three encounters with sperm whales! The first time there was a distance of about 30m between boat and whale and the second time only 15m-20m! The third time was from a distance of 50m. The probability to see a sperm whale diving down is about 1:50 - so we were really lucky. These animals are sighted mainly because of their blow. This recognition feature of the sperm whales is visible at a great distance.The blow of each large whale species is very characteristic, in shape, size and orientation. The fin whale and the sperm whale can be distinguished at larger distances among other things by its shape and ejection angle.

Furthermore, we also saw dolphins during the trips, namely bottlenose dolphins. We did not encounter common or striped dolphins or other species.The bottlenose dolphins were incredibly playful and surfed very close to the boat in the bow wave (bowriding). In addition, we also observed behaviours like body roll, bellyup, breaching, spy-hopping, fluking and chasing.

The firmm team always documents the many trips on the Strait with sighting reports. In addition to date, time and conditions such as tide, wind, visibility and clouds, the behaviour of the animals and distance to the observer are recorded. This is very valuable for research on animals in the Strait, as it can be used to determine their occurrence, distribution and routes.The Strait of Gibraltar is extremely busy. There are always problems and the danger of collision between cargo ships and whales and other animals. The data collected can be used, for example, to bring about or prevent changes in freighter routes if there is a high risk of collisions with animals.

 

We also saw non-mammals on the trips. Especially many sunfish "Mola Mola". According to Katharina Heyer, this was due to the fact that before our trips there was still Levante and the sunfish swim close to the surface especially at the end and after the Levante. These are also very impressive animals.The specimens sighted were rather young, since they were not very large. Molas grow their whole lives. I.e. the older the animals, the bigger. Also tunas were sometimes spotted. Their pointed fins and shiny bodies are very impressive.

These sightings of whales and fish touched us all emotionally.To experience animals like this - incredibly beautiful.Many thanks to firmm and  Prof. Dr. Holm.