How many fish species are there?

The first global census of life in the sea has logged some 230,000 species, however a ten year study on the subject performed by over 300 scientists warns of mass extinctions.

This ten year study has been the largest, most extensive study to attempt a stab at that age old question “Just how many fish are there in the sea?”

The ten year study, which was published today, is attempting to answer that question. It has analyzed the diversity, distribution and abundance of life in the world’s oceans. This study, dubbed The Census of Marine Life, hopes to give a ballpark estimate of the present marine life, and has estimated that there are more than 230,000 species living in our oceans.

“From coast to the open ocean, from the shallows to the deep, from little things like microbes to large things such as fish and whales,” explained Patricia Miloslavich of Universidad Simón Bolívar, Venezuela and co-senior scientist of the COML.
The study which was carried out also covers animals such as; crabs, plankton, birds, sponges, worms, squids, sharks and slugs.

Moe than 360 scientists from around the world got together and have spent the past ten years surveying 25 different regions, ranging from the Antarctic through the more temperate and tropical seas, to the Arctic, to attempt a head count of the different kinds of plants and animals.

The results of the study show that just about twenty percent of the marine species of the world are crustaceans such as lobsters, krill, barnacles, and crabs. Toss in Molluscs (such as squid and octopus) and fish (which include sharks) and that adds up to half of the number of species which are found in the oceans of the world.

The charismatic species often used in those ecological conservation campaigns – sea lions, turtles, whales and sea birds – make up less than 2% of the species in our world’s oceans.

Which is really interesting when you think about it.. We tend to only take notice of the species right on the surface, without really giving a second thought to those that dwell within the depths..

The surveys also pointed out the major areas of concern for the conservationist groups. “In every region, they’ve got the same story of a major collapse of what were usually very abundant fish stocks or crabs or crustaceans that are now only 5-10% of what they used to be,” explained Mark Costello of the Leigh Marine Laboratory, University of Auckland in New Zealand. “These are largely due to over-harvesting and poor management of those fisheries. That’s probably the biggest and most consistent threat to marine biodiversity around the world.”

The main threats that have been found up till now are; overfishing, degraded habitats, pollution and the arrival of invasive species. However, it was pointed out that more problems are on the horizon including; rising water temperatures, acidification thanks to global warming, and the expansion of areas unable to support life in the ocean.

Hopefully this survey will raise global awareness, and as a race, we can get together and start trying to preserve the abundant life, which is at the depths of our oceans.

According to the simplest version of the so called Iron Hypothesis, plankton blooms move atmospheric carbon down to the deep sea and increased carbon dioxide levels in the atmosphere can therefore be counteracted by promoting plankton blooms. The Iron Hypothesis derives its names from the suggestion that global warming can be thwarted by fertilizing plankton with iron in regions that are iron-poor but rich in other nutrients like nitrogen, silicon, and phosphorus, such as the Southern Ocean.

New research from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory is now dealing a powerful blow to this hypothesis by showing that most of the carbon used for plankton blooms never reaches to deep sea.

Using data collected around the clock for over a year by deep-diving Carbon Explorer floats, Oceanographers Jim Bishop* and Todd Wood** have revealed that a lot of the carbon tied up by plankton blooms never sink very far.

“Just adding iron to the ocean hasn’t been demonstrated as a good plan for storing atmospheric carbon,” says Bishop. “What counts is the carbon that reaches the deep sea, and a lot of the carbon tied up in plankton blooms appear not to sink very fast or very far.”

The reasons behind this behaviour are complex, but the seasonal feeding behaviour of planktonic animal life is believed to play major part.

Photoplankton

The Carbon Explorer floats used in the study were launched in January 2002, as a part of the Southern Ocean Iron Experiment (SOFeX)***, and experiment meant to test the Iron Hypothesis in the waters between New Zealand and Antarctica during the Antarctic summer.

SOFeX fertilized and measured two regions of ocean, one in an HNLC (high-nutrient, low-chlorophyl) region at latitude 55 degrees south and another at 66 degrees south. Carbon Explorers were launched at both these sites while a third Carbon Explorer was launched well outside the iron-fertilized region at 55 degrees south as a control.

Bishop and Wood were originally assigned to the project to monitor the iron-fertilization experiment for 60 days, but the Carbon Explorers continued to transmit data throughout the Antarctic fall and winter and on into the following spring.

“We would never have made these surprising observations if the autonomous Carbon Explorer floats hadn’t been recording data 24 hours a day, seven days a week, at depths down to 800 meters or more, for over a year after the experiment’s original iron signature had disappeared,” Bishop explains. “Assumptions about the biological pump – the way ocean life circulates carbon – are mostly based on averaging measurements that have been made from ships, at intervals widely separated in time. Cost, not to mention the environment, would have made continuous ship-based observations impossible in this case. Luckily one Carbon Explorer float costs only about as much as a single day of ship time.”

The scientific hypothesis that iron can be used to stimulate phytoplankton growth in regions low in iron but rich in other nutrients is still intact and experiments show that algal blooms do in fact occur if you add iron to such waters. The study by Bishop and Wood only shows that the carbon bound by the plankton do not end up far down in the depths of the sea.

Jim Bishop’s team. (From left) Christopher Guay,
Phoebe Lam, Jim Bishop, Todd Wood, and David Kaszuba.

During the early stages of the South Sea experiment, the Iron Hypothesis seemed to hold up to scrutiny as the Berkeley researchers could detect not only a vigorous plankton bloom in the fertilized region at 55°N, but also how carbon particles sank beneath the bloom carrying 10-20 percent of the fixed carbon away from the surface layer and down to a dept of at least 100 meters. These results were published in the 2004April issue of Science.

But since the Carbon Explorers continued to submit information even when the 3-month study was officially over, Bishop and Wood could continue their monitoring of South Sea carbon levels throughout fall and winter and well into the following spring; a continued monitoring that would prove invaluable.

The two Carbon Explorers released at 55 degrees south continued to report for over 14 months and almost reached South America before they turned silent. After this, the explorer launched at 66 degrees south continued to transmit for another four months, despite having spent much of the Arctic winter recording at a dept of 800 meters where the pressure is immense. This explorer also had several encounters with the underside of chunky sea ice as it tried to surface to report during the Arctic winter.

All this new data surprisingly showed that there seemed to be much less particulate matter reaching the depth where the biomass was highest, i.e. in plankton blooms. Reports from the 66°S explorer showed how particulate carbon levels decreased sharply as the perpetually dark Arctic winter commenced and ice began to cover previously open waters. As the sun returned in spring and melted the ice the levels made a modest increase, but no sinking (sedimentation) of large amounts of carbon to the deep ocean was observed.

Another even more surprising report came from the control float, dubbed 55 C, which reported higher sedimentation of carbon 800 meters under a region with no plankton bloom than what the other 55°S (dubbed 55A) reported from the fertilized, blooming region.

Researchers are currently pondering several ideas as to explain these unforeseen results but have not reached any conclusion. A higher biomass seems to be linked to a lower export of carbon, but one knows why. One of the most promising hypotheses takes into account how phytoplankton needs sufficient amounts of light to survive and grow. Latitude 55°S is located far enough from the Arctic for light to reach the ocean year round, even though the amount is severely reduced during the winter months. But the notorious winter storms occurring in these waters can cause mixing between near-surface water and underlying water layers all the way down to a dept of 400-500 meters. Phytoplankton are dragged down to depths where it is too dark for them to grow and where hungry zooplankton waits for them.

“Mixing is the dumbwaiter that brings food down,” says Bishop. “The question is whether the dumbwaiter is empty or full.”

If mixing is consistently below the critical light level, phytoplankton can not grow, i.e. the dumbwaiter stays empty and the zooplankton gets no food. As the winter storms stop with the advent of spring, the phytoplankton can quickly rebound, aided by increased levels of sunlight. But since a lot of zooplankton starved to death during the winter, the zooplankton population is not large enough to keep steps with the phytoplankton bloom and intercept carbon loaded material as it sinks between 100 and 800 meters.

In the part of the South Sea where Carbon Explorer 55C spent the winter collecting data, storms where not continuous and the mixing was therefore halted now and then. More zooplankton survived, zooplankton which fed on the phytoplankton in spring, keeping their numbers down and increasing carbon sedimentation.

Bishop says these observations point to an important lesson: “Iron is not the only factor that

determines phytoplankton growth in HNLC regions. Light, mixing, and hungry zooplankton are fundamentally as important as iron.”

You can find more information about Bishop and Wood’s study in the journal Global Biogeochemical Cycles. Preprints of the issue are already available to subscribers at http://www.agu.org/journals/gb/papersinpress.shtml.

* Jim Bishop is a member of Berkeley Lab’s Earth Sciences Division and a professor of Earth and planetary sciences at the University of California at Berkeley.

** Todd Wood is a staff researcher with the U.S. Department of Energy’s Laurence Berkley National Laboratory.

*** The Southern Ocean Iron Experiment (SOFeX) is a collaboration led by scientists from Moss Landing Marine Laboratory and the Monterey Bay Aquarium Research Institute.

A record number of North Atlantic Right Whale (Eubalaena glacialis) calves have been found in winter nursery waters off the coast of Florida and Georgia this winter. No less then 39 calves have been confirmed by researchers, a number which breaks the old record from 2001 when 31 calves where spotted.

The North Atlantic Right Whale is one of three right whale species belonging to the genus Eubalaena. Earlier, all three species were classified as a single species. Since 2001, only 20 calves have been born in these waters each year, on average, and 39 new calves in one season is therefore very good news for an endangered North Atlantic species that numbers only about 400 animals.

“Right whales, for the first time in a long time, are doing their part: They’re having the babies; they’re having record numbers of babies,” says Monica Zani, an assistant scientist at the New England Aquarium who works with North Atlantic Right Whales. “We need to be vigilant and still do our part to prevent the whales from being killed“, she adds.

“For me, personally, it is a source of optimism,” says Barb Zoodsma, a marine mammal biologist with the National Oceanic and Atmospheric Administration. “I just think we’re on the right track.“

It is however important not to put too much weight on one single year. “It’s definitely good news, and it’s the most that we’ve seen, but it’s only one year,” says Kate Longley, who works on a team with the Provincetown Center for Coastal Studies to monitor right whales in Cape Cod Bay. “I think it would be premature to make any sort of prediction or any sort of statement about the state of the species based on one year of high calving. There hasn’t been much indication that the species is rebounding significantly.“

To get from their feeding grounds in the Gulf of Maine to their winter nursery areas off the coast of Georgia and Florida, the North Atlantic Right Whales have to migrate through areas with heavy shipping traffic and deaths from collisions with shipping poses a serious risk for this already depleted population.*

During recent years, several attempts have been made to decrease the amounts of deaths and injury from collisions, but it is too early to tell if these changes have contributed to the record number of calves.

In 2003, discussions between Irving Oil Corp. officials and Moira Brown, a Canadian expert on right whales and a senior scientist with the New England Aquarium in Boston, caused the corporation to shift shipping lanes in the Bay of Fundy to protect the North Atlantic Right Whales. That same year, Canadian and international shipping officials agreed to shift shipping lanes in the bay between Maine, New Brunswick, and Nova Scotia, about four nautical miles east in hope of decreasing the risk of whale collisions. Four years later, the US government changed shipping routes out of Boston in an attempt to make the U.S. coastal waters safer for whales, especially the North Atlantic Right Whale.

Another problem faced by the North Atlantic Right Whale is fishing ropes. Today’s modern fishing ropes are strong enough to entangle a whale and rub through its tough skin and thick flesh, all the way into the bone. This year, researchers had to rescue five entangled whales in the southeast Atlantic, using small boats, knives and grappling hooks.

The calving season is now over and the North Atlantic Right Whales are heading back to feed in the Gulf of Maine. Hopefully, a large portion of the newborn calves will stay clear of both ships and fishing gear. If they survive for an additional 5-7 years, they will be able to reproduce and aid this dwindling population on its way to recovery.

* Vanderlaan & Taggart (2007). “Vessel collisions with whales: the probability of lethal injury based on vessel speed” (PDF). Mar. Mam. Sci. http://www.phys.ocean.dal.ca/~taggart/Publications/Vanderlaan_Taggart_MarMamSci-23_2007.pdf.

The hydrothermal vents that line the mid-ocean ridges are a major source of iron for the creatures living in the sea. Humans are not the only ones who suffer when iron becomes scarce; creatures such as phytoplankton are known to grow listless in waters low in iron, even if they are drifting around in an environment rich in many other types of nutrients.

Earlier, scientists assumed that the iron exuded from hydrothermal vents immediately formed mineralized particles as soon as it came in contact with the salty water – a form of iron that is hard to utilize for living creatures.

New research has however unveiled that some of the iron spewed out from these vents actually remain in a form that is easy to absorb for oceanic beings. According to researcher Brandy Toner, a surprising interaction between iron and carbon in hydrothermal vents serves to stop the corrosion.

“Iron doesn’t behave as we had expected in hydrothermal plumes. Part of the iron from the hydrothermal fluid sticks to particulate organic matter and seems to be protected from oxidation processes,” Toner explains.

The research was carried out on hydrothermal vent particles collected by the team from the Tica vent in the Eastern Pacific Rise. With the help of the Advanced Light Source synchrotron at the Lawrence Berkeley National Laboratory, Toner was able to analyze the particles using focused X-ray beams.

Iron is a key player in this newly discovered process in the ocean, but the exact mechanisms remains unknown.

“So the question becomes, what are those organic compounds? Are they organic compounds like in oils and tars or is it actually the stuff of life?”, says Chris German, co-author of the paper. “Brandy’s work doesn’t mean that these [carbon-iron] complexes are definitely alive. But, this is a possible smoking gun. This paper opens up a whole new line of research and asks a new set of questions that people didn’t know they should be worrying about until now. A bit of work on a tiny nanometer scale can force you to ask questions of global significance.

Perhaps hydrothermal venting, a process traditionally believed to be a completely inorganic process, actually is a part of the organic carbon cycle on our planet.

The paper “Preservation of iron (II) by carbon-rich matrices in a hydrothermal plume” by Brandy Toner and her colleagues[1] has been published in Nature Geoscience[2].

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Aquarium Toplist function added

The oceans of the world absorb a large part of the carbon dioxide released into the atmosphere by us burning fossil fuels, burning forests to make room for fields, etc. This have helped slow down global warming, but new studies shows that it might have a devastating effects on certain fish species such as clown fish. Tests performed on clown fish larvae have shown that increased levels of carbon dioxide can make them disoriented an unable to find a suitable home and avoid predators. The pH level in the ocean has dropped 0.1 since pre-industrial times due to the absorption of carbon dioxide and researchers believe that it will fall another 0.3-0.4 before the end of this century.

This increased acidicy of the water can cause serious problems for clown fish larvae, since clownfish larvae lose the ability to sense vital odours in more acidic waters – probably owing to the damage caused to their olfactory systems. Kjell Døving (Oslo University), co-author of the rapport that was published in US journal Proceedings of the National Academy of Sciences, says “They can’t distinguish between their own parents and other fish, and they become attracted to substances they previously avoided. It means the larvae will have less opportunity to find the right habitat, which could be devastating for their populations.“

The research indicates that other species might be affected in a similar way and might have a hard time finding their way to suitable habitats if carbon dioxide levels raises in the oceans.

About the study

The study was executed in such a way that the researchers checked how well clownfish larvae could detect smells in normal sea water (pH 8.15) and how well they could detect odours in more acidic water (at levels predicted to be a reality around the year 2100 and later). The test showed that at pH 7.8 the larvae stopped following scent trails released by reefs and anemones and started following sent trails they would normally avoid; scents that are associated with environments not suitable for clown fish. The larvae also lost the ability to use smell to distinguish between their parents and other fish. At pH 7.6 the larvae were unable to follow any kind of odour in the water, and instead swam in random directions.

As we release more and more carbon dioxide from fossil fuel into the atmosphere, the world’s oceans become more and more acidic. Exactly how this will affect marine life remains unknown, but a paper published this week by marine chemists Keith Hester and his co-authors at the Monterey Bay Aquarium Research Institute is now shedding some light on how a change in acidity affects sound waves under water.

Beluga Whale

So, why is the speed of sound underwater of any interest to Monterey Bay Aquarium researchers? As sounds travel faster, the amount of background noise in the sea will increase and this could affect the behaviour of marine mammals. Many marine mammals, such as whales, dolphins, and porpoises, relay on sounds for communication and food location.

According to conservative projections by the Intergovernmental Panel on Climate Change (IPCC), the chemistry of seawater could change by 0.3 pH units by 2050. According to Hester and his colleges, such a change in acidity would allow sounds to travel up to 70 percent farther underwater in some areas, especially in the Atlantic Ocean. The paper also states that sound may already be travelling 10 percent farther in the oceans than it did a few centuries ago.

According to Hester et al, a change by 0.3 pH units by 2050 will have the greatest effect on sounds below about 3,000 cycles per second. This range includes most of the low frequency sounds that marine mammals are known to use, but it also includes a lot of sounds produced by human activity, such as boating, shipping, and certain military activities. As if acidification of the ocean wasn’t enough, the amount of underwater sound produced by human activities has increased dramatically over the last 50 years. So, even if acidification would make it possible for sound produced by marine mammals to travel farther than ever before, it might also cause these sounds to be effectively drenched by a cacophony of human generated low frequency noise. In such a noisy sea, a marine mammal’s ability to locate prey animals and a suitable mate and could be severely impinged on.

The paper will be published in the October 1, 2008 issue of Geophysical Research Letters.

A group of Indian fishermen have threatened to commit suicide unless the authorities take necessary action to stop other fishermen from using prohibited purse seine and hair nets. The banned equipment can catch at least three tonnes of fish and sea food in a single trip; efficiently depriving lawful fishermen of fish.

According to the affected fishermen, roughly 300 boats continue to use prohibited fishing gear in the waters off Ramanathapuram. Since the present regulation against the practise has proven ineffective, the fishermen now demand confiscation of boats and nets from unlawful fishermen. Officials from the fisheries department have expressed powerlessness, since the unlawful fishermen enjoy political patronage.

Located in India’s south-eastern coastal region, close to Sri Lanka, Ramanathapuram is a city and a district in the Tamil Nadu state.