They investigate the massive death of mussels on the beaches of Puerto Madryn | It is a species with a key role in water purification

2023-04-25 04:31:12

Scientists from the Institute of Biology of Marine Organisms (IBIOMAR-Conicet) analyze the causes of the disappearance of mussels on the beaches of Puerto Madryn. Although it is similar to a mussel, it is a different species. Until recently they covered approximately 90 percent of the surface they inhabited, but today it is almost impossible to find them. The increase in air and sea water temperatures, the impact of tourism, pollution and the devastation caused by invasive species –such as the green crab, which feeds on these animals– are some of the causes that explain this freak.

When the tide goes out, a very diverse world of marine organisms appears on the beaches that are covered with rocks. A few years ago it was very common to see mussels everywhere. However, the current situation is different. “A decade ago we began to study mussels and we observed the impact that tourism had on this community through human trampling and vehicle traffican activity that drastically decreases coverage”, recalls Maria MendezIBIOMAR researcher.

In the summer of 2019, there was a massive die-off of mussels, even in places where people did not step. In addition, their number continued to dwindle during the pandemic, when tourism was not allowed and vehicles were not on the road. “There it was evident that, in addition to the trampling, something was happening,” Mendez points out.

At the weather

Thus, a team of specialists began to evaluate environmental issues related to climate change and observed an increase in air and water temperatures over the past ten years. The number of very hot days is becoming more frequent in the region and the mussels are covered and uncovered by the sea every six hours, depending on how the water rises or falls. When they are out in the open, they close their valves to protect themselves and reduce any type of interaction. Nevertheless, hot air raises their internal temperature and they have no way to regulate it.

According to the scientific team, there are no other previous records of such large mortality of these animals in the world. “During 2017, an all-time high in air temperature of 44.7 degrees was recorded and the following year the mussel population began to decrease,” Mendez highlights.

“We analyzed historical records and observed that came to be exposed to temperatures of more than 40 degrees, when the normal thing is that they do not exceed 35 in the air. Besides were exposed to 24 degrees of water temperature, when it rarely exceeds 20”, describe John Paul Livoreresearch member.

Thermometers on the coast

During 2022, scientists placed thermometers on the coast to continuously measure the temperature of the water and air in the summer. What the researchers will do is replicate these increases in the laboratory to be able to observe the effects they cause on the mussels.

However, it is impossible to point to a single reason that explains its mortality. “Another factor that affects the drop in coverage is the arrival on these beaches in 2015 of the European green craban invasive species that is highly predatory and feeds on mussels,” says Mendez.

In addition, the scientist points out that another reason to understand the phenomenon is the increase in pollution in relation to the increase in maritime traffic in the Nuevo Gulf, located northeast of Chubut. In addition to the experiments, they will study the aquarium and the amount of mussels consumed by the green crab in order to find out their incidence in the recorded mortality.

Filters and purifiers

These animals play an important role within trophic chains. They are the prey of many animals, mainly birds and other invertebrates. Besides, Being filter-feeding organisms, they collaborate in the purification of water.

“They are habitat-forming species. What they do is create an environment with less difficult conditions so that other species can live within that framework that they form.. When they covered between 90 and 100 percent of the substrate, a lot of associated species lived below and between the mussels,” says Livore.