Between the tides
Text: Thomas Jermann, Christoph Dieffenbacher
Since the middle of the 1980s zoology students have been examinating the same coastal section every year in the northern Brittany.
No comfort is spared for these budding marine researchers roaming the sandy beach or clambering along densely vegetated cliffs to examine the soil laid bare by the tide. Sporting rubber boots and armed with nets, buckets and magnifying glasses, they manage to remain completely dry. Each year, in late summer, a group of zoology students descends on the intertidal zone of Erquy, on the north coast of Brittany, to conduct applied research in marine biology.
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Dog whelks attach egg capsules to the rocky substrata. Each capsule contains around 500 eggs of which only 25 will develop – the remaining eggs function as ’nurse eggs’ to feed the hatchlings. (Image: University of Basel, Thomas Jermann)link.zoom -
What look like eyes on the underside of the thornback ray are actually gill slits. (Image: University of Basel, Thomas Jermann)link.zoom -
Around 7 centimetres in length, the cockle lives just under the surface in sandy sediment. It creates a permanent flow of water in order to filter plankton. What resembles a pair of puckered lips is the so-called ‘mantle crest’. It creates the two calcium carbonate shell halves and seals them together completely. When viewed from the end, the cockle has a perfect heart shape. (Image: University of Basel, Thomas Jermann)link.zoom -
The individual zooids of the star ascidian form star-shaped colonies that are often very varied in color. They grow directly on rocks or large pieces of red or brown algae. (Image: University of Basel, Thomas Jermann)link.zoom -
Algae provide both a surface and nutrition for young sea snails: the young animals eat their way right into the surfaces they attach to. (Image: University of Basel, Thomas Jermann)link.zoom -
Colorful sea anemones live in shallow residual water pools. Snakelocks anemones are underwater animals that look like flowers. The anemone extends its sticky stinging tentacles to catch as much plankton as possible. Its brownish to bright green coloring comes from plant symbionts: internal photosynthesizing unicellular algae produce glucose which provides the majority of the anemone’s nutrition. (Image: University of Basel, Thomas Jermann)link.zoom -
Common prawns are undoubtedly the most robust species of shrimp found at the coast. When there is a lack of oxygen in the residual pools at night, the prawns hang below the surface of the water on their stomachs. Here, they benefit from the slightly elevated oxygen concentration. They can survive on only a tenth of the oxygen required by fish. During the day, these omnivores graze on algae or eat dead plants and animals. (Image: University of Basel, Thomas Jermann)link.zoom
Especially in fall and spring, the tidal range here is enormous. At full and new moon, daily sea level fluctuations can exceed twelve meters, making it a harsh environment for sea creatures to survive in. Dehydration, oxygen deprivation, extreme heat or cold, pounding surf, submersion, downpours and changing acidity levels are all regular hazards for the organisms that live here. Even so, evolution has given rise to a staggering range of plant and animal life: A single kilometer of coastline is home to up to 500 animal species and 600 species of algae.
The students are led by Dr Thomas Jermann, curator of the Basel Zoo aquarium, who took over the course from Professor David Senn. The project is remarkable for its continuity: young researchers have been going over this section of coastline with a fine-toothed comb every year since the mid-1980s. Over the years, the students from Basel have amassed a wealth of findings and research ideas at Erquy, with some choosing to return later on to write their final thesis.
Thomas Jermann works full time as curator of the Vivarium at Basel Zoo and is also a passionate photographer. The zoologist completed his doctorate at the University of Basel, where he has organized events on biology and marine biology for over 20 years – including excursions to the intertidal zones of northern Brittany.
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