The Mediterranean Sea: A biodiversity and plastics hotspot - marine biologist

Despite making up only one per cent of the global ocean surface area, the Mediterranean Sea hosts around 10 per cent of all marine species in the world, marine biologist and academic Alan Deidun has told The Malta Independent.

Deidun said that while the Mediterranean flourishes with such biodiversity, it is also a plastics hotspot, being one of the areas in the world most affected and polluted due to the high concentration of plastics found.

The Malta Independent met Deidun to discuss how the Mediterranean Sea has changed due to further urbanisation of the countries around it, and the damage caused by single-use plastics.

“Plastic has become man’s blueprint. It damages the Mediterranean, and damages sectors which are heavily reliant on the Mediterranean Sea,” explained Deidun. “Aesthetically, macro litter is bad for business where the sea plays a vital role, as plastic litter is an eyesore.” He goes on to explain that once this litter sinks to the seabed, it smothers marine communities such as coral, and ultimately traps them.

“We have gone down 300 meters near Filfla, and all you see are whole coral communities covered in nylon rope from previous fishing seasons, where nylon ropes are cut but not recovered.”

The biggest threat of all is micro and nano plastics, which end up in the food chain, he said.

“The smaller pieces of plastic are then absorbed or eaten by zooplankton, which are then consumed by smaller fish, which in time end up on our plate. According to most recent studies, plastic particles have been found in human stool for the first time. We need to be more concerned about our marine life, even if it is from a selfish perspective; as the waste we are throwing into the sea is the same waste we will consume.”

Over the summer months, the main news headlines have highlighted the issue of trees being chopped down and uprooted. Environmental issues are not a new topic, but more and more people are discussing the environmental impact of uprooting such trees, especially on an island which lacks green open spaces to begin with. Yet, there has not been as much discussion on the environmental importance of the Mediterranean Sea. Gulia Magri spoke to marine biologist and lecturer ALAN DEIDUN about how the Mediterranean Sea has changed over time due to the increase in population, invasion of alien species and climate change. Would you say there is enough focus on the importance of the sea and marine biodiversity?

The public’s perception of the marine environment is quite ambiguous, and at times the sea is really overlooked. Although we are an island, our marine area is large, and just taking into consideration our territorial waters, the ratio is 14.1 – all this without considering the fisheries zone or search-and-rescue area. When we discuss environmental issues and climate change, we must see what is happening to our seas and we should have a much greater interest and appreciation of the role the ocean plays in our lives.

We normally think of trees as providing us with oxygen, but at least half of the oxygen we breathe comes from the ocean, where we find oxygen-producing phytoplankton.

Subconsciously, we have a link to the sea, as we draw ourselves closer to the presence of the sea, which can bring about feelings of nostalgia and memories. The sea has both a direct and indirect tie to the island’s economy. Directly: fishing and aquaculture; while indirectly, when tourists come to our beaches and restaurants serve the catch of the day. There is also a booming diving industry. Many Maltese people do not know enough about the sea and are hesitant to learn more.

What changes have you seen over the past 10 to 20 years in marine biodiversity due to climate change?

As temperatures continue to rise, this has an impact on our seas. It is the third consecutive summer, where by the end of it we will see maximum water temperatures above 30 degrees Celsius. There is no exact threshold as to how high the temperature can get before causing damage, but we do know that there are some species which suffer when the temperatures rise, especially those found in shallow areas, where it gets very hot. Many algae disappear by the end of summer. Also, when there is a prolonged heatwave, a mass of hot water sits on cold water, and over time the hot water pushes further down and ends up affecting species which are not adapted to such high temperatures.

Another major impact of climate change would be the invasion of alien species entering the Mediterranean Sea and causing harm to our native marine life. Most alien species keep a low profile and are not always an issue, but then there are a few, such as the lionfish, which displace the native species, with potentially devastating results. There are also harmful algae which are harming the sea grass species, such as the posidonia, the lung of the Mediterranean Sea. The sea grass is vital as it keeps the sea clear, provides oxygen and is also a place for other species to lay their eggs. This grass covers less than two per cent of the Mediterranean. Anchoring and pollution harms these meadows as well.

Going back to the lionfish, there was also a time when one could buy a lionfish in a pet shop and release it back into the sea, unaware of the harm or impact on the biodiversity. Another example of this is the release of crayfish into freshwater valleys, such as Chadwick Lakes, where they run riot and affect indigenous species such as the native frog and freshwater crab. We must continue to raise awareness and monitor aquarium releases and customer behaviour.

You said that we see alien species entering our waters, but do we ever see our own native species migrating and moving to other parts of the Mediterranean?

In terms of our own native species, we have a particular species of fish, the salema, better known as xilpa, which is slowly being replaced by the alien rabbit fish. The native fish are moving, yes; so now we find that species which were exclusive to the east Mediterranean are now moving west, while those observed in the south are moving north. This could also be happening with the dolphin fish (lampuki) because catches have dwindled in recent years and this might be because there are more fishermen moving in our area catching this fish. Previously, Maltese fishermen were specialised in catching this fish,

but now there are other nationalities. It might be that this fish is moving because its prey species are also travelling through different routes; therefore their own routes are changing.

Does the overcrowding of beaches during the summer impact our marine life?

The main issue with overcrowding would be trampling, on both land and sea. On land coastal communities, we see that the native sand dunes (għaram tarramel) have been trampled on over time, either by people driving over them or camping on them. Currently, one can find such sand dunes on a few beaches such as Golden Bay, Ramla l-Ħamra in Gozo, the Bird Sanctuary at Għadira and Santa Marija in Comino. An example of trampling at sea would be when one finds fragile communities such as algae or coral on a shallow reef, which people might trample over.

Another issue, apart from overcrowding, would be the ever-increasing number of boats during the summer months. Anchoring destroys sea grasses and leaves shallow holes behind, and dumping the discharge of the boat pollutes the sea. One must also remember that the noise caused by the boats is amplified underwater, and many times scares or disorientates slow moving species. Such boats also end up colliding with migrating animals; earlier this summer we had a loggerhead turtle hit by a boat propeller. Although Nature Trust rescued the turtle, it ended up dying due to injuries.

What can one do to decrease the harm and damage being caused to the Mediterranean Sea?

I would start with the very basics, that being raising more awareness and fostering a more oceanliterate society. Ocean literacy is all about making people more aware of the ocean’s role in our lives. One example would be how the ocean plays a role as a climate regulator, taking the heat from the tropics to the poles to regulate temperature. If this were to stop, we would see extreme changes in our climate.

We need to remember that the effects of climate change are not exclusive to land. A healthier ocean means a better chance of fighting climate change. We should not take our seas for granted, and always be prepared for any massive pollution event which can affect us negatively, such as a massive oil spill. We are, to a certain extent, prepared, as there is constant training and a partnership between the University of Malta and the Civil Protection Department, which handles such training.

Preparation is extremely important, especially since we get 60 per cent of our drinking water from the sea; so God forbid there is ever a massive oil spill.

““A healthier ocean means a better chance of fighting climate change. We should not take our seas for granted