Mediterranean Sea: an example of the oceans' destiny?

A recent review describes how the Mediterranean Sea could offer an idea of the disastrous future of the oceans.

This review of more than 100 studies on the Mediterranean’s changing ecological dynamics, describes the convergence of climate change and human impacts in waters that had been stable since the time of Aristotle.

Rising temperatures, disrupted deep-water hydrology, overfishing, shrinked food-webs, mass die-offs, diseases and pollution are some of the threats that are affecting the Mediterranean Sea. Other sea areas on Earth may not escape from this sad degradation destiny. The future doesn’t look so nice...

Silvia Bonizzoni

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Lejeusne C., Chevaldonné P., Pergent-Martini C., Boudouresque C.F., Pérez T. 2009. Climate change effects on a miniature ocean: the highly diverse, highly impacted Mediterranean Sea. Trends in Ecology and Evolution. doi:10.1016/j.tree.2009.10.009

Abstract:
Little doubt is left that climate change is underway, strongly affecting the Earth's biodiversity. Some of the greatest challenges ahead concern the marine realm, but it is unclear to what extent changes will affect marine ecosystems. The Mediterranean Sea could give us some of the answers. Data recovered from its shores and depths have shown that sea temperatures are steadily increasing, extreme climatic events and related disease outbreaks are becoming more frequent, faunas are shifting, and invasive species are spreading. This miniature ocean can serve as a giant mesocosm of the world's oceans, with various sources of disturbances interacting synergistically and therefore providing an insight into a major unknown: how resilient are marine ecosystems, and how will their current functioning be modified?

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For more information:
http://www.wired.com/wiredscience/2009/12/mediterranean-degradation/

Mega-flood filled the Med in under two years

Around 5.6 million years ago tectonic movements and a drop in sea level cut the Mediterranean out of the worlds' oceans. For 300 million years our sea dried up almost everywhere, in what is called the Messinian salinity crisis.

The water then returned: what started like a trickle, later became an event of biblical proportions which filled the Mediterranean in under two years. At peak times, the sea level rose by up to ten meters a day - the largest known flood in Earth's history.

Daniel Garcia-Castellanos of the Jaume Almera Institute of Earth Sciences in Barcelona, Spain, and colleagues, who published their work on Nature, estimate the peak flow to have been around 1000 times higher than the present Amazon river at its highest rate.

For more information:
- Catastrophic flood of the Mediterranean after the Messinian salinity crisis
- Castellano's page

Mediterranean region: ever drier by 2100

'A new study suggests that the impact of climate change on the Mediterranean region will change precipitation and evaporation rates over land and sea, creating even drier conditions. A greater amount of atmospheric moisture will be lost from the region. Agriculture may suffer as a result, and the salinity of the Mediterranean Sea could increase.
The study suggests that many of the projected changes will have started by 2020-2049, with further changes gradually intensifying until 2070-2099.
Long-term changes project a decrease in precipitation and an equal increase in evaporation over the Mediterranean Sea, making the sea increasingly saline: the degree of salinity will depend on the inflow of fresh water from the Atlantic Ocean through the Gibraltar Strait.
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For more information:
Original article by EU DG Environment

How climate influences the deep sea

Picture the Grand Canyon in Arizona - then place it under the sea: the Mediterranean seafloor is criss-crossed with deep submarine canyons that in sheer size put their land counterpart to shame. Rivers of dense waters flow through these canyons, their capacity varying depending on climate-induced phonomena.

During such an event, the amount of water transported in 4 months from the Gulf of Lion to the deep Western Mediterranean via the Cap de Creus canyon equalled 2 years of input from all rivers draining in the Mediterranean.

How these dense shelf water cascading in the Gulf de Lion affect the population of the deep sea shrimp Aristeus antennatus, the most valuable deep-sea living resource in the Mediterranean Sea, was recently discovered by Spanish researchers. Initially, the strong currents (up to 80 cm/sec) displace shrimp populations from the normal fishing grounds, producing a temporary fishing collapse. However, the food provided by the currents soon leads to a large increase in recruitment - which results in plentiful landings of large shrimps 3-5 years after major cascading events.

These new findings resolve the paradox of a long-overexploited fishery that has not collapsed after 70 years of intense deep-sea trawling. But climate change is expected to cause a decrease of winter deep water formation in the Gulf de Lion, which in turn could decrease the frequency and intensity of dense shelf water cascading events. Without this regenerative mechanism, fishery pressure could quickly deplete the stock of Aristeus antennatus and other valuable deep-sea living resources in the area.

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For more information:
Company et al (2008) Climate influence on deep sea populations. PLoS ONE 3(1): e1431.
Eureka alert press release (Jan 15th 2008)

Mediterranean forecast

A great information tool for scientists working in our inland sea is the Mediterranean Ocean Forecasting System (MFS) created by GNOO, the Italian National Applied Oceanography Group.

Daily temperature, salinity, height, anomalies at the surface or in the depths; a forecast for the next 10 days and an analysis of the past 7 days are available.

Other regional forecasting systems, amongst others:

• the Adriatic Sea
• the Sicilian Channel
• the North-West Mediterranean

(image: MFS)

Ocean deserts

The world oceans are deeply affected by human activities, from pollution to resource overexploitation, but now there is a new problem.

The least biologically productive areas of the oceans are expanding much faster than predicted. This is the result of a new study conducted by researchers at the National Oceanic and Atmospheric Administration (NOAA) and the University of Hawaii.

The evidence of this expansion comes from data collected by a visual satellite sensor that reads reflective colour to measure the density of chlorophyll in phytoplankton, the microscopic organisms that are the base of the marine food web. Atlantic and Pacific Oceans are characterized by huge 'black' spots, which indicate zones of very low productivity. These zones, likened to deserts, now cover an estimated 51 million square kilometres in the two oceans and are replacing very fast adjacent prolific areas.

This change in ocean biology, probably linked to the warming of sea surface waters, can have deep consequences to all marine ecosystems. It may negatively affect all the marine food web from plankton to fishes, turtle and cetaceans.

Silvia Bonizzoni

(The image by NOAA shows black areas considered the least biologically productive)

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For more information:
www.noaanews.noaa.gov

What is Mediterranean Conservation?

Mediterranean Conservation explores the possibility of merging the communication efforts of individuals committed to marine conservation in the ancient Tethys Ocean.