The following short videos provide insights into threats from human activity to the marine environment. Their message is very straightforward – Slow down, enjoy the sea, you may hear, see and feel more than you think!
Underwater noise adversely affects marine animals which use hearing as their primary sense. In waters deeper than 30m, where light penetration is low or minimal, many marine animals replace the use of sight with a sonar sensory system primarily for navigation. Among the most vulnerable are fish and marine mammals, such as dolphins and whales, which have developed a very sophisticated system of receiving and transmitting audio signals – echolocation, used when hunting and orientating. Due to, among other, intense urbanization and tourism, human activities that occur on the coast or at sea generate underwater noise (“Anthropogenic noise”); maritime transport, with emphasis on nautical tourism, is an acute cause. Recent scientific studies point to the seriousness of this problem on a global level. Noise from vessels disguise sound signals, including those necessary for survival; intense noise exposure can cause temporary or permanent damage to the hearing of dolphins and whales. Beyond individual incidents, long-term exposure to intense noise results in behavioural and habitat use pattern changes, and negatively affect reproduction and survival success. In some species, exposure to noise causes behavioural change of the males that use noise to attract females during breeding season. Continuous exposure can cause dolphins to dive or move away from important feeding or nursing areas. Dolphins may try to adjust to noise by changing the frequency and intensity of sound produced so they can continue communicating, however, any response or adaptation to sound pollution results in energy loss and stress. Humans can reduce their noise pollution and its impact by acting responsibly and applying protective measures.
In Croatia, dolphins have been protected against any form of disturbance by law since 1995. However, some human activities leading to disturbance are often related to recreational boating tourism. Specifically, motor and speed boats are unpredictable and often aggressive, from the viewpoint of the dolphins. They are perceived as a threat thus leading to a change in behaviour, most commonly manifested by prolonged dives in order to move away from the boat. The physical presence of vessels, and the loud noise produced by the engines place the animals under great stress and forces them to consume additional energy to avoid them. Prolonged exposure to stress has a negative impact not only on the individual but also on the entire population, reducing their reproduction rate and overall social behaviour. Sailors using boats for recreation and sport, can be more informed about the rules of conduct of vessels in the vicinity of a group of dolphins (Code of Conduct EN).
Land-based pollution is a major stressor on the marine environment. Solid waste, oil and tar, and a range of organic and inorganic pollutants threatens marine life. Plastics and plastic products – bags, bottles, shoes, nets, cellophane, and Styrofoam are particularly important. They are one of the most widespread forms of floating solid waste in the sea. Many animals, particularly whales, dolphins, seals, sea turtles and sea birds die because they swallow pieces of floating plastic, especially plastic bags, mistaking them for prey. Micro-plastics –the finer pieces resulting from plastic decomposition – is absorbed as food and accumulates in the digestive system causing disease and weakening of the animals. Animals might get entangled in the larger debris which becomes a deadly trap in the sea. When plastic sinks in large quantities, it creates anaerobic conditions on the sea bed and benthic, slow moving organisms, are likely to die. When the plastic reaches the shore, it becomes an obstacle to animals trying to exit to the coast, particularly monk seals and sea turtles. When sea turtle hatchlings or seabirds make their way back to the sea, small amounts of waste on the shore are a deadly trap. Moreover, people are visiting the shores of the Adriatic Sea and the amount of waste is increasing proportionately with them, exacerbating the existing problem of poorly organised collection and disposal at the local community level. Lastly, large ships such as tourist cruisers dispose large amounts of garbage. The preventive measures are simple – avoid and recycle, reduce the amount of waste, use alternative products, take away your garbage, and recycle if you can. Ask others politely to do the same.
Documentary: The Open Sea
The Open Sea is a natural history film about the life of marine species in the Adriatic Sea during spring. After winter storms and the mixing of water layers, the sea is again rich with nutrients. Plenty of food and light allow the proliferation of phytoplankton algae, which begins the spring explosion of life. Phytoplankton is the primary food of zooplankton species, among which are the shrimps and copepods; the open-sea food web ends with the larger marine predators such as tuna, dolphins or the 15-meter long fin whales. In the open Adriatic Sea one can catch the rarely seen species such as the zooplankton Salpa, pelagic crabs, wreckfish, giant devil rays, striped dolphins and many others. The shore and offshore islands and reefs are inhabited by indigenous algae and invertebrates. They are all part of this story of marine life at the open sea, which is still poorly understood. This film was made as part of the “NGO capacity building for implementation of Natura 2000 priority actions” project, funded by the European Union. The content of this film is the sole responsibility of the Blue World Institute and in no way reflects the views of the European Union.