Standing on the shore, I look out at the horizon, the cold wind tangling my hair and sending a chill through me. The appearance of the sun lifting my mood and motivating me to jump into the cold winter sea in front of me.
As a small child I got to know the Adriatic Sea for the first time. I had no idea what lay beneath the waves. Then, finally I got my first mask and a pair of fins to look beneath the waves and lift the blurry surface of mystery. I remember snorkelling very carefully, making sure not to touch anything of this strange weightless world. Back then, of course, I only ever explored during warmer seasons, that was until last year. Until I was asked to film a marine biological program that teaches students about the Mediterranean Sea and specifically the Northern Adriatic in winter. I saw this fascinating place in a whole new light.
My friend and marine ecologist Sandra Bračun, who works at the University of Graz and Morska škola in Pula as an educator, opened my eyes to the winter sea. Through the years working with Sandra on my documentary films, she has shown the Mediterranean Sea to me in a new light and had sparked my interest in marine biology. Sandra is an amazing educator, so who better to learn from than her! Last year I learned about changing salinity and water currents and discovered animals that I found deeper in the ocean in summer, now higher up in winter. It is an incredible silent kingdom with nobody around during the cold season.Let’s discover the Mediterranean winter sea through Sandra’s knowledge.
The Mediterranean Sea and its importance:
Why is the Mediterranean Sea considered a biodiversity hotspot, and what factors contribute to its ecological richness?
The Mediterranean Sea is considered a biodiversity hotspot due to its high variety of marine species and unique ecosystems. It hosts approximately 17,000 species, with around 20% being endemic, meaning they are found nowhere else in the world. Despite taking up less than 1% of the world’s ocean surface. The Mediterranean Sea is home to 11% of all marine species. This extraordinary biodiversity is closely linked to the sea’s geological history. Extreme events like the Messinian Salinity Crisis when the Mediterranean almost completely dried out around 5.6 million years ago – and the extreme temperature fluctuations during the last Ice Age significantly influenced species diversification. These events pushed species to adapt to new environments, creating new habitats and promoting evolutionary processes. As a result, many species developed unique adaptations, contributing to the region’s rich ecological variety.
What role does the Mediterranean Sea play in global ocean circulation and climate regulation?
The Mediterranean Sea plays a crucial role in global ocean circulation through the process of thermohaline circulation. The sea’s high salinity and temperature differences between its surface and deep waters create dense water masses that sink and flow out into the Atlantic Ocean through the Strait of Gibraltar.This exchange of water contributes to the Atlantic Meridional Overturning Circulation (AMOC), which helps regulate global climate patterns by distributing heat and influencing weather systems.
How do endemic species in the Mediterranean adapt to its unique environmental conditions?
Endemic species in the Mediterranean Sea have developed specialized adaptations to survive in its unique environmental conditions. For example, the Posidonia oceanica seagrass. This is an important endemic species that thrives in clear, shallow waters with high light availability and plays a key role in stabilizing sediments and providing habitat for marine life. This plant has existed for about 100 million years, it dates back when dinosaurs still roamed the Earth. Don’t get it mistaken with an alga, it is a true flowering plant (spermatophyte) that evolved from land and returned to the sea. This plant holds incredible history, it is one of the oldest living organisms on the planet. Some seagrass meadows in the Mediterranean are estimated to be up to a 100,000 years old.
Seasonal Differences in the Northern Adriatic
How does water temperature in the Northern Adriatic differ between summer and winter, and what are the ecological differences of these changes?
Water temperature in the Northern Adriatic varies significantly between summer and winter. During summer, surface waters can reach temperatures above 27°C, creating stratified layers that limit vertical mixing. However, during summer, excessive nutrient input from agricultural runoff or wastewater discharge can lead to extreme algal blooms, which may disrupt the ecosystem by causing oxygen depletion and harming marine life. In contrast, winter temperatures drop to around 8-10°C, and the water column becomes well-mixed due to strong winds and storms. This mixing increases nutrient availability, enhancing primary productivity and supporting different species assemblages.
Ocean Currents & Their Effects
Major Surface and Deep-Water Currents in the Mediterranean and Their Influence on Local Ecosystems
The Mediterranean Sea is characterized by complex circulation patterns driven by differences in temperature, salinity, and wind. The major surface currents include the Atlantic Water inflow through the Strait of Gibraltar, which moves eastward along the North. This current influences nutrient transport and supports productive ecosystems. The deep-water currents, such as the Levantine Intermediate Water and the Eastern Mediterranean Deep Water, play a crucial role in oxygenating deep-sea habitats and distributing nutrients across different regions, significantly affecting benthic communities.
Salinity & Its Effects
Geographic and Seasonal Variations in Mediterranean Sea Salinity
Salinity in the Mediterranean Sea varies both geographically and seasonally. The western basin generally exhibits lower salinity due to the inflow of Atlantic Water, while the eastern basin reaches higher salinities.
Main Drivers of Salinity Changes in the Northern Adriatic
Salinity in the Northern Adriatic is primarily driven by river inflows, particularly from the Po River, which reduces salinity levels near the coast. Wind patterns, such as the Bora wind, can also influence salinity distribution by promoting mixing and upwelling.
Seasonal Animal Distribution & Ecosystem Shifts
Differences in Fish Community Composition Between Summer and Winter in Coastal vs. Offshore Environments
Coastal fish communities exhibit higher diversity in summer due to increased productivity and warmer temperatures, favoring the species such as seabreams and mullets. Offshore environments show more stable community compositions year-round, with dominant species like anchovies and sardines. In winter, both coastal and offshore communities experience reduced abundance and diversity. During this season it seems there are fewer fish, as if they were falling into a winter torpor or retreating. However, many nudibranchs appear, including the very large vail snail (Tethys fimbria), along with othermollusks such as octopuses and squids. Notably, there is also a high number of crustaceans such as crabs and lobsters.
The ocean is an amazing place all year round. If you want to learn more about thewinter ocean, Morska śkula (Meeresschule Pula) offers programs to explore the winter sea. You can also follow along Sandra’s ocean journey on her Instagram@sandra.bracun where she often posts interesting information about marine life.
Introduction text: Sabine M. Probst, Mairne Biological Content: Sandra Bracun, Photos: Sabine M. Probst