Why do we need ocean?

Fortunately, society is more concerned about the state of conservation of the environment due to human activities, both on land and at sea. In case there are still who think we do not need sea at all, this article aims to show what benefits gives us the sea.

WHICH ISSUES ARE AFFECTING THE SEA?

Did you know that some studies suggest that the entire surface of the seas and oceans of the Earth is hit by some human activity? In fact, 41% of the surface is affected by more than a factor of anthropogenic origin.

According to the United Nations Environment Programme (UNEP), there are several anthropic impacts at sea:

• Ocean acidification.
• Coral bleaching [More information here].
• Chemical contamination.
• Global change [You can read about the effects of global change on plants, whales, corals, reptiles and the current sea level rise].
• Increase in toxic algae.
• Increased invasive species [Discover what is an invasive species!].
• Increase of jellyfish [If you want to know how are jellyfish and want to learn to identify the species of the Mediterranean, visit this article].
• Loss of biodiversity.
• Loss of habitats.
• Nutrient overload.
• Overexploitation of species with commercial interests.
• Dead zones.

There are many anthropic impacts at sea, like pollution by several types of products and materials (Picture: NOAA, Creative Commons).

Not only do they affect marine ecosystems, but also affects the human population because the ecosystem services promote our welfare. So we can ask: why do we need the sea?

WHICH BENEFITS DO WE OBTAIN FROM SEA?

According to TEEB, ecosystem services are all those direct and indirect ecosystem and biodiversity contributions to human welfare. These services are: supply services, cultural services and regulation services.

SUPPLY SERVICES

All those contributions of ecosystems that take place directly or indirectly to human welfare, whether they have a biological or geological origin, are part of supply services.

Foods that the sea provides is one of the most important supply services to humans, including fish, shellfish and algae. An example of this is the fact that supplies 20% of the animal protein intake to 3,000 million people and that more than 120 million tons of fish were consumed in 2010. For all this, the current situation of exploited populations is critical in many cases, as you can read in this article.

Sea supplies 20% of the animal protein intake to 3,000 million people  (Picture: Pixabay).

Sea is also a source of renewable energy because it is the source of many weather events (like wind) and tides and currents. Thus, sea provides wind energy and tidal power (generated by tides, currents and waves).

Another benefit that we get is different biotic or geologic materials, such as salts, ornamental materials and mineral resources. Without going into the details of the high environmental impact of extracting marine mineral resources, materials such as sand, diamonds, metals such as gold and tin, coal, gas hydrates, oil, gas and some others are exploited [can read more in this document of the International seabed Authority (ISA)].

The exploitation of marine geologic resources, which is not free of impacts, lets obtain many diverse resources (Picture: National Geographic).

In addition, we benefit from certain substances and organisms that have some beneficial property to humans, such as medicines and cosmetics.

CULTURAL SERVICES

Cultural services are those that are obtained through direct experience with ecosystems. Although they are not the most important, we must also taken into consideration.

Ecosystems help to the creation and maintenance of cultural identity and sense of belonging to a community. What would we be without our festivities and without the different types of food?

Marine ecosystems enable developing advocacy and awareness by sea. They also contribute to the increase of scientific knowledge through research of different types. If you’re a biologist, would you like to discover a new species?

Research in marine environment let obtain useful knowledge for society (Picture: Perplex Me Not).

It is also the basis for many recreational activities such as whale watching, diving, tourism, recreational fishing and navigation activities [Do you want to know if recreational fishing is compatible in marine reserves?].

Here we could talk about more services, but I focused on the most relevant.

REGULATION SERVICES

Last but not least, marine ecosystems are responsible for the proper functioning of ecosystems as a whole. They are the most important services because from them depend all the rest.

In marine ecosystems, it occurs a set of processes by which they maintain or improve water and sediment quality. To give an example, they are involved in the oxygenation of dead zones and to absorb waste or pollutants.

But, certainly, it is important to highlight its key role in regulating the Earth’s climate. Earth’s oceans are the largest sink for greenhouse gases because they capture  carbon dioxide away from the air and distributes it in depth. So, they help to fight against global change, but everything has its limit.

Due to the power of oceans in absorbing dioxide carbon, they play a key role in climate regulation  (Picture: El Confidencial).

On countless occasions, we have seen beaches to disappear after a storm, a hurricane and other extreme events. Do you want to know the reason? The main reason is that due to human action, our coast has lost its protective function, ie, has lost the ability to buffer natural disturbances. In a healthy beach, after a storm, it would regenerate naturally. Well, when a beach disappears, then  we have problems in promenades or houses built  at first line of the coast.

Although we could explain some more benefits, I will finish by mentioning its importance in providing the necessary nutrients for marine organisms and habitat maintenance of biodiversity.

REFERENCES

• FAO. (2012). The State of World Fisheries and Aquaculture. FAO. Rome.
• Fernando Santos-Martín, Carlos Montes, Paloma Alcorlo, Susana García-Tiscar, Blanca González, María Rosario Vidal-Abarca, María Luisa Suárez, Laura Royo, Inmaculada Férriz, Juan Barragán, Juan Adolfo Chica, César López y Javier Benayas. 2015. La aproximación de los servicios de los ecosistemas aplicada a la gestión pesquera. Fondo Europeo de Pesca, Fundación Biodiversidad del Ministerio de Medio Agricultura, Alimentación y Medio Ambiente. Madrid.
• Jackson, J.B., Kirby, M.X., Berger, W.H., Bjorndal, K.A., Botsford, L.W., Bourque, B.J., Bradbury, R.H., Cooke, R., Erlandson, J., Estes, J.A., et al. (2001). Historical overfishing and the recent collapse of coastal ecosystems. Science 293, 629–637.
• MA (Millennium Ecosystem Assessment). (2005). Ecosystem and Human Well-being. Island Press. Washington.
• Notes of the subject “Geología de los océanos” of the Master in Oceanography and Marine Environment Management (UB).
• TEEB. (2012). The Economics of Ecosystems and Biodiversity in Business and Enterprise. Joshua Bishop (ed.). Earthscan, London and New York. Urquhart, J., Acott, T., Reed, M., Courtney, P. (2011). Setting an agenda for social science research in fisheries policy in Northern Europe. Fish. Res. 108,
  240–247.
• UNEP. (2006). Marine and coastal ecosystem and human well-being. A synthesis report based on the finding of the Millennium Ecosystem Assesment. UNEP.
• Main picture: Stilts fishhermen Sri Lanka (Bernard Gagnon, Creative Commons).

You can save bluefin tuna!

Bluefin tuna is an endangered predator fish. Last week, we explained that other species like sardines and mackerel are also endangered due to overfishing. This week, we will focus on this species and we will explain its biology and distribution, in addition to the reasons why it is under threat. 

BIOLOGY

Bluefin tuna (Thunnus thynnus) is the biggest species of the Scombridae family and one of the biggest bony fishes. Despite they can achieve a length of 3 meters, they usually range between 0.4 and 2 meters. Moreover, they weight between 140 and 680 kilos, but it is difficult to find an organism that exceed 450 kilos. It is a migratory animal with a high economical value for its red and dusky meat. The body is fusiform and can be distinguished from the rest of tunas by pectoral fins: they are rather short and reach the 11th or 12th dorsal spine.

Bluefin tuna (Thunnus thynnus) (Picture from Club de la Mar).

Back and upper sides are dark blue to black, with a grey or green iridescence. Inferior sides are silvery with grey spots and bands. Anal in is dark and yellow.

Diet of bluefin tuna includes squids, eels and crustaceans, but also schooling fishes like herrings and mackerels.

DISTRIBUTION

Bluefin tuna lives in subtropical and temperate waters of North Pacific, Atlantic, Mediterranean and Black Sea. Despite bluefin tuna can be found along the year in the Mediterranean, they are present mainly in June and July.

Free bluefin tuna (Picture from Animals on Earth).

CONSERVATION STATUS AND PROBLEMS

According to IUCN, bluefin tuna is endangered and its population is in decline. Due to overfishing, being the most important the illegal fishing, it is estimated that Western Atlantic population has decreased in an 87% since 1970. Anyway, other references indicates that this drop has been between 29 to 51%. In 1996, scientist alarmed that worldwide catch quotas must be reduced an 80% to recover populations in 20 years, but in fact they were increased. Nevertheless, it seems like the reduction of captures recently has produced an increase of populations.

Because they achieve maturity in an advanced age, they are specially vulnerable to overexplotation. Despite catch quotas have been established, the measure have not had always success for several reasons: disembark of small fishes (and big) has continued, the lack of regulations in some areas, fishermen ignore restrictions in some countries and the lack of fines when breaking the lows.

Between 2000 and 2004, it had been captured about 32,000 – 35,000 tonnes per year in the Eastern Atlantic and Mediterranean, achieving 50,000-60,000 tonnes in 2006, so the stock status is overexploited. Nowadays, the catch quota is restricted to 13,500 annual tonnes, but 3,000 tones are for Spain.

This tuna is captured with different types of fishing: purse-seine, longline and tramps. The reason of its fishing is to meet demand of Japanese market of sashimi (just one piece of tuna can be sold for 90,000€), what caused its overfishing. In addition, it is a goal species in recreational fishing of United States and Canada.

Bluefin tuna sashimi (Picture from TripAdvisor).

So, fisheries are being reduced and, at the moment, neither European Union nor other countries have acted to save it. In addition, governments have ignored experts.

¿WHAT WILL IT HAPPEN IF WE RUN OUT OF BLUEFIN TUNA?

Bluefin tuna is a predator of jellyfishes. Its reduction, together with the rise of sea temperature, is causing a rising of jellyfishes. Moreover, its disappearance would produce an imbalance of food webs.

If you are worried about the status of bluefin tuna and the oceans, when you go to a fish market, don’t buy it and also when you go to a Japanese restaurant, refuse to eat any dish with tuna. Only reducing the demand, we will be able to stop its fishing. 

REFERENCES

• Schultz, K (2003). Field guide to Saltwater fish. Wiley (1 ed).
• IUCN: Thunnus thynnus. 
• Slow Food: El atún rojo.
• WWF: Atún rojo

Mediterranean Monk Seal: Until when will it survive?

In this post, we will do an approach to Mediterranean Monk Seal (Monachus monachus), a critically endangered species that, in fact, is the most endangered pinniped species in the world. Here, we are going to do a short historical review and we are going to talk about its natural history, its habitat and distribution, its threats and status and, finally, its conservation. 

INTRODUCTION

Mediterranean Monk Seal (Monachus monachus) is one of the three species included in the genus Monachus (Monk Seals). The other two species are Hawaiian Monk Seal (Monachus schauinslandi), which is critically endangered, and Caribbean Monk Seal (Monachus tropicalis), which is extinct.

Mediterranean Monk Seal (Monachus monachus) (Photo: Sá, Wild Wonders of Europe)

Mediterranean Monk Seals were hunted for fur, oil and meat since Prehistory. Romans were responsible of an important decline, but thanks to the empire’ fall the animals were able to recover. More recently, the two world wars, the industrial revolution, the explosion of tourism and industrial fishing have produced the reduction and disappearance of the species in some regions.

MEDITERRANEAN MONK SEAL’S NATURAL HISTORY

When they are born, their length is 94 cm and their weight is 15-20 kg. Until weaning (at about 16-17 weeks), growth takes place fast. The pups’ pelt is soft and downy and the coat is black to dark brown, with a white patch in the belly.

Adult individuals have a length of 2.4 m (from nose to tail) and weigh 250-300 kg. Males are only slightly bigger than females. Juveniles and adults have very short hair. While adult males are black with a white patch in the belly, adult females are brown and grey with a lighter belly colouration. In any case, they can present more patches on the throat (males) and back (females).

Female individual of Mediterranean Monk Seal (Photo: Sá, Wild Wonders of Europe)

Male individual of Mediterranean Monk Seal (Photo: Sá, Wild Wonders of Europe)

Males and females reach sexual maturity between 5 and 6 years. After a gestation lasting 9-11 month, one pup is born (generally in autumn).

They feed on fish and cephalopods.

HABITAT AND DISTRIBUTION

This species’ habitat is inaccessible caves with underwater entrances. The truth is that in ancient times, they inhabit open beaches of sand and rocks. Mediterranean monk seals can be found in warm temperate, subtropical and tropical waters of the Mediterranean Sea and the east Atlantic Ocean.

Mediterranean Monk Seal habitat (Photo: Sá, Wild Wonders of Europe)

Mediterranean Monk Seal on beach (Photo: Hellio & Van Ingen)

In ancient times, the species’ distribution was bigger than now. While now they just are present only in the northeast Mediterranean and in the northeast Atlantic, long ago they were present in all through the Mediterranean Sea, Black Sea, Atlantic coast of Africa and some Atlantic islands.

Distribution map of Mediterranean Monk Seal (Monachus monachus) (Picture: TheAnimalFiles.com)

STATUS AND THREATS

With just 350-450 individuals (maybe 550), the Mediterranean Monk Seal is one of the world’s most endangered marine mammals and is the most endangered pinniped species and it is described as critically endangered by IUCN.

Mediterranean Monk Seal is critically endangered, according to IUCN (Picture: IUCN).

The main threats against the species are:

• Habitat degeneration and loss by development in the coast. The driving causes to this may be hunting, mass tourism, pleasure boats and diving. The result is that the caves occupied now are not adequate for their survival, so the recovery is only possible if they return to sandy beaches.
• Killing them on purpose by fisherman and fish farm operators because they find it a nuisance that destroys their nets and steals their fish. In Greece, deliberate killing accounts for 43% of the deaths of adult and juvenile animals.

Deliberate killing of a Mediterranean Monk Seal (Monachus monachus) (Picture: E. Tounta, MOm).

• Accidental entanglement in fishing gear. It is unknown if this has an important impact nowadays, but in the recent past it was and, in fact, it has played a significant role in the elimination of the species from some parts.
• Decreased food availability due to overfishing. Malnourishment; susceptibility towards pathogens; affected growth, reproduction, juvenile survival and mortality rate and dispersion are the possible effects of this.
• Unusual events: disease (like morbillivirus), toxic algae, rockslides, cave collapses or oil spills.
• Pollution, maybe caused by organochlorine compounds used in pesticides.
• Inbreeding depression, that results in reduced fecundity and pup survival. This factor is not a significant threat in the short term, but it can be a future threat because this causes reduced fertility, increased infant mortality and a distorted sex ratio.

CONSERVATION

Since 1970s, conservation measures have been developed, but the improvements are hardly seen. Conservation measures include:

• Development of marine protected areas (MPA) in Madeira, Greece, Turkey and Cabo Blanco. In fact, what is necessary is a network of MPA.
• Orphaned and hurt animals are rescued.
• Educational programs.
• Scientific investigation to identify its habitat areas.
• International coordination of conservation activities.

On the other hand, ex situ conservation measures (like captive breeding and translocation) are not used because the species is so sensitive to human disturbance that it could be another threat.

REFERENCES

• Fauna Iberica: Foca monje
• IUCN Red List: Monachus monachus 
• MarineBio: Mediterranean Monk Seals
• NOAA Fisheries, Office of Protected Resources: Mediterranean Monk Seal
• The Monachus Guardian (main source)
• Wildscreen Arkive: Mediterranean Monk Seal

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