Guest blog post by Iryna Kapshyna, Gritta Veit-Köhler, Leon Hoffman and Sahar Khodami.
During a relaxing beach vacation, most people probably give little thought to whether the beach would still be there if it was not regularly replenished.
In fact, sand nourishment is a common and frequently used coastal protection measure whereby sand is sucked up from the seabed by a flushing ship, transported to the coast, washed up and spread with bulldozers.
Due to continuous erosion – the removal of sand by storms, waves and currents – sand nourishment has to be repeated regularly. Otherwise, uncontrolled erosion would mean the loss of beaches, shore areas, coastal cliffs and dunes.
But, while they are important, coastal protection measures such as sand nourishments incur high costs and often lead to the disturbance of ecosystems.
In a study published in the open-access journal Metabarcoding & Metagenomics, A research team from Senckenberg am Meer in Wilhelmshaven show how such disturbances and the subsequent recovery can be monitored efficiently and reliably.
At Ahrenshoop on the Baltic Sea, researchers investigated the effects of sand nourishment on the meiofauna – organisms less than one millimeter in size – and found significant results.
“State-of-the-art genetic methods and the traditional method of identifying and counting the animals under the microscope show the same result. The communities of meiofauna changed drastically after the sand was washed up and slowly recovered over the course of a year.”
Project coordinator, Dr Gritta Veit-Köhler.
Immediately after the impact, mites (Acari) and annelid worms (Annelida) had almost completely disappeared from the swash zone, copepods (Copepoda) declined significantly, while the number of flatworms (Platyhelminthes) increased.
Meiofauna organisms are the most numerous animals on the seabed and play an important role in the food webs there. They are well suited as ‘bioindicators’ to detect and study environmental impacts and various forms of ecosystem disturbance, including those caused by humans. Due to their small body size, ubiquity and large numbers, their communities can be studied with small sample sizes.
Over a period of one and a half years, the researchers took and analysed a total of 246 sand samples from the beach-water interface.
“Using the classic taxonomic method, we identified 27,445 individuals under the microscope, which we assigned to ten higher taxonomic groups such as nematodes and copepods. But it was only the genetic analysis that brought the full diversity of species to light.”
Iryna Kapshyna, doctoral student and first author of the study.
Using the ‘metabarcoding’ method, in which all animals in a sample are analysed together and differences in specific gene segments (here V1&V2) are searched for, a large number of samples can be analysed quickly and reliably.
The researchers were able to identify a total of 843 so-called ‘operational taxonomic units’ (OTUs) – in simple terms, different species.
“843 species sounds like a lot – but in fact, the beach studied had a lower diversity of meiofauna compared to the deep sea or other marine areas.”
Dr Sahar Khodami, Senckenberg am Meer.
The size of the organisms studied means they have previoulsy been difficult to study and have not received as much attention as larger species.
“When considering the effects of coastal protection measures on ecosystems, the smallest marine animals should not be overlooked! Metabarcoding can replace the traditional morphological method, after initial studies using both methods.”
The research team.
Original study:
Kapshyna I, Veit-Köhler G, Hoffman L, Khodami S (2024) Impact of a coastal protection measure on sandy-beach meiofauna at Ahrenshoop (Baltic Sea, Germany): results from metabarcoding and morphological approaches are similar. Metabarcoding and Metagenomics 8: e127688. https://doi.org/10.3897/mbmg.8.127688
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