Diaries of the Ocean

Learn about life in the ocean, how ocean ecosystems function, how scientists study the ocean, and the challenges we face in sustaining healthy oceans for the future. Explore the charismatic marine species - the most compelling creatures in the ocean that capture our attention and inspire us to learn more - and what they can tell us about how the ocean works and why it is so important for all life on earth.

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Harmful Algal Blooms

What are they? Harmful algal blooms, or HABs, occur when colonies of algae — simple plants that live in the sea and freshwater — grow out of control and produce toxic or harmful effects on people, fish, shellfish, marine mammals and birds. The human illnesses caused by HABs, though rare, can be debilitating or even fatal. Ranging from microscopic, single-celled organisms to large seaweeds, algae are simple plants that form the base of food webs. Sometimes, however, their roles are more sinister. Under the right conditions, algae may grow out of control — and a few of these “blooms” produce toxins that can kill fish, mammals and birds, and may cause human illness or even death in extreme cases. Other algae are nontoxic, but eat up all of the oxygen in the water as they decay, clog the gills of fish and invertebrates, or smother corals and submerged aquatic vegetation. Still others discolor water, form huge, smelly piles on beaches or contaminate drinking water. Collectively, these events are called harmful algal blooms, or HABs. With climate change and increasing nutrient pollution potentially causing HABs to occur more often and in locations not previously affected, it's important for us to learn as much as we can about how and why they form and where they are, so that we can reduce their harmful effects. Why do they happen? While we know of many factors that contribute to HABs, how these factors come together to create a “bloom” of algae is not well understood. HABs occur naturally, but human activities that disturb ecosystems seem to play a role in their more frequent occurrence and intensity. Increased nutrient loadings and pollution, food web alterations, introduced species, water flow modifications and climate change all play a role. Studies show that many algal species flourish when wind and water currents are favorable. In other cases, HABs may be linked to “overfeeding.” This occurs when nutrients (mainly phosphorus and nitrogen) from sources such as sewers and agriculture flow into bays, rivers, and the sea, and build up at a rate that “overfeeds” the algae that exist normally in the environment. Some HABs appear in the aftermath of natural phenomena like sluggish water circulation, unusually high water temperatures, and extreme weather events. Other factors, such as the structure of the coast, runoff, oceanography, and other organisms in the water, can also change the scope and severity of HAB impacts.

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Ocean acidification: a disturbing story

For good reason, ocean acidification is often called “climate change’s evil twin.” The overload of carbon dioxide in our oceans is literally causing a sea change, threatening fragile, finite marine life and, in turn, food security, livelihoods and local to global economies.

Like a sponge, our oceans are absorbing increasing amounts of CO2 from the atmosphere. Over the past 200 years, the world’s seas have absorbed more than 150 billion metric tons of carbon from human activities. CO₂ concentrations are now higher than at any time during the past 800,000 years, and the current rate of increase is likely unprecedented in history.

The ocean's role in the global carbon cycle

The ocean plays a critical role in the global carbon cycle as it is a vast reservoir of carbon, naturally exchanges carbon with the atmosphere, and consequently takes up a substantial portion of anthropogenic carbon from the atmosphere. This accumulation of carbon in the ocean is also impacting marine life through a process known as ocean acidification.

Image source: NOAA 

The consequences of disrupting what has been a relatively stable ocean environment for tens of millions of years are beginning to show. The massive amount of carbon dioxide being absorbed by the oceans dissolves in seawater as carbonic acid. This process is known as ocean acidification, and it’s causing a sea change that is threatening the fundamental chemical balance of ocean and coastal waters from pole to pole. Increasingly, corrosive waters are making it difficult for fragile marine life to build their protective shells and skeletons.

While much is still unknown about ocean acidification, science already shows that its consequences can be profound. Some of the most vulnerable species are the small life forms that commercially-important fish depend on for food. How these fish may adapt to an eroding food supply is a critical question. Along with increasingly acidified waters, the oceans are warming, and the oxygen critical to marine life is decreasing. Each stressor is a problem. But all three hitting our oceans at one time is a triple threat, with enormous implications for food security, local to global economies, jobs, and vital consumer goods and services.

Ocean acidification impact on pteropods

Image source: Smithsonian Ocean Portal 

Pteropods, or sea butterflies, are a vital food source for salmon and other commercially important fish. Shown here in laboratory conditions are (left) a pteropod that has lived for six days in normal waters and (right) a pteropod showing the effects of living in acidified water for the same time period. The white lines indicate shell dissolution and explain why ocean acidification is often called "osteoporosis of the sea." (NOAA)

Osteoporosis of the sea

Ocean acidification can create conditions that eat away at the minerals that oysters, clams, lobsters, shrimp, coral reefs, some seaweed plants and other marine life use to build their shells and skeletons.

Human health, too, is a concern.  Many harmful algal species produce more toxins and bloom faster in acidified waters. This could harm people eating contaminated shellfish and sicken fish and marine mammals. And while ocean acidification won’t make seawater dangerous for swimming, it will upset the balance among the microscopic life found in every drop of seawater. Such changes can affect seafood supplies and the ocean’s ability to store pollutants, including future carbon emissions.

What actions are needed 

Smart investments in monitoring and observing are critical to hedging the risks. We can‘t manage what we don’t measure, and observations are requisite to providing the environmental intelligence that underpins sound approaches to countering acidification.

To prevent ocean acidification from being a game-changer, robust forecasting capabilities and public/private partnerships are needed to interpret not only the global picture but regional and community conditions. 

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Think you can’t live without males? Think again

Reproduction takes two… right? This is true for most animal species. However, one fish species has taken a different approach. The Amazon Molly is entirely female. 

When they are ready to reproduce, members of this species must find a male of another, related species, and mate with him. However, instead of using the sperm from this male to provide half of the genetic information for the future offspring, the female Amazon Molly merely uses the sperm as a signal to trigger embryogenesis, in a process known as gynogenesis.

In this process, no genetic information is taken from the male at all. The female is capable of producing her own diploid eggs, and only requires the male to provide a physiological trigger in the form of his sperm.

The males that the Molly is able to trick into mating with her get nothing for their trouble, while she produces offspring who are genetically identical to her. 

The amazon molly doesn’t live in the Amazon River. It was named for the Amazon warriors of Greek mythology, an all female warrior society. 

Photo - http://biologicalexceptions.blogspot.com 

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Mediterranean - Human Impact

Bounded by mountains, man has made his impact mainly on the narrow coastal plain some 20 to 30 km wide, and in some areas humans have literally carved spaces from the mountains themselves. 

With the notable exception along the African coast, virtually all of the Mediterranean population can be found along this narrow coastal strip and its associated islands. 

Much of the coastal plain was dominated by mosquito-infected swamps and history tells of the canal and irrigation systems which drained the swamps and irrigated land for cultivation. 

Much of the original forest has been cut down leaving a rather sparse and scrubby landscape. 

The Mediterranean basin and surrounding countries have 450 million people, more than half of them living around its shores. 

Economic and industrial growth has resulted in vastly increased population levels. The need to feed this increasing population, and its annual tourist influx of over 100 million visitors, has put further strain on the sea and its marine life.

Much of the coastline has been irreparably changed by human expansion and development, with yacht marinas, harbors and housing developments. 

The Mediterranean Sea is undoubtedly one of the world’s most threatened seas, owing solely to the increased demand on its natural resources primarily through pollution from homes, industry and intensive agricultural methods., and the unsustainable fishing industry.

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The Mediterranean - a Sea of Seas

Although not truly one sea, but several jointed together, the individual seas are defined by the surrounding land masses formed when the earth’s crust collided.  A shallow submarine ridge (the Strait of Sicily) between the island of Sicily and the coast of Tunisia divides the sea in two main regions: the Western Mediterranean, with an area of about 850,000 km2 and the Eastern Mediterranean, of about 1.65 million km2. 

A characteristic of the coastal Mediterranean are submarine karst springs, which discharge pressurized groundwater into the coastal seawater from below the surface; the discharge water is usually fresh, and sometimes may be thermal.

The Alboran Sea is found in the west, connecting to the Algerian Sea or Balearic Basin between Algeria, Sardinia, Spain and France. 

The Gulf of Lyons and the Ligurian Sea stretch along the southern coast of France, the Tyrrhenian Sea surrounded by Corsica and Sardinia to the west, Italy to the east and Sicily to the south. 

The Gulf of Trieste, in the northern area of the Adriatic Sea, is formed with Italy on its west, Croatia and Albania to its east; further south the Ionian Sea separates the southern coasts of Italy and Sicily with the Maltese islands to the west with Greece and its many islands to the east. 

Separating Greece and Turkey is the Aegean Sea which is connected to the Black Sea in the north-east by the Dardanelles, Sea of Marmara and the Bosporus. 

In the east can be found the Levant Sea bordered by Turkey and the islands of Crete and Cyprus to the north, and Syria, Lebanon and Palestine to the east, with Egypt and Libya to the south. 

The Ionian Sea and the Levant Sea are roughly divided by a shallow stretch of water sometimes referred to as the Libyan Sea.  

 The Mediterranean Sea has an average depth of 1,500 m and the deepest recorded point is 5,267 meters in the Calypso Deep in the Ionian Sea. The coastline extends for 46,000 km. 

In Egypt can be found the man-made Suez Canal, opened in 1869, which links the Mediterranean with the Red Sea. 

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The Mediterranean

Known as the Cradle of Civilization, the Mediterranean Sea is now set in a massive flooded depression in the Earth’s crust formed over millennia. This vast expanse of water is almost completely landlocked, stretching from the Straits of Gibraltar in the west, to the coasts of Syria, Lebanon and Palestine in the east. The Mediterranean both links and divides three continents, Europe, Africa and Asia. The varies depths of this basin also support varying communities of marine life. 

With water temperatures that never drop below 10oC, the Mediterranean has remained fairly isolated over the years and has evolved a distinct ecosystem only troubled by human’s intrusion. The region is complex and diverse in its geography, history and climate. 

Known for its very singular climate, the present shores of the Mediterranean were roughly formed five million years ago. However, it took early form over twenty million years ago when the western shores were still closed and the eastern end was still linked to the vast primeval Tethys Sea.

As the years passed, Africa slipped anticlockwise, Arabia split from Africa forming the Red Sea and the eastern stretches of the Mediterranean also became landlocked. While this continental movement was progressing, the land areas were gradually crumpled up forming a ring of mountains which comprise the Sierra Nevada, the Alps, the Rhodope Mountains, the Akhdar Heights and the Taurus Mountains. Over the subsequent two to three million years, the now landlocked Mediterranean filled and evaporated several times as the earth’s crust shifted, often leaving gigantic salt marshes and mud pools where dinosaurs once roamed. 

As far as can be agreed between scientists, about five million years ago there was a massive cataclysmic earthquake which opened up the Gibraltar sill, and the Atlantic Ocean poured into the basin taking almost a century to fill. Today, this connection to the Atlantic Ocean is still very evident and water pours into the Mediterranean at approximately 4 km/h in a layer from 75 to 300 meters deep. This sea water gradually evaporates and the heavier, more salty water sinks and eventually flows back out through the Straits of Gibraltar, taking around 80 years to replenish the water column. 

This has had several effects, one of which is the reduced amount of plankton to be found in the Mediterranean, and what plankton there is often flows back out into the Atlantic in the deeper ocean currents. This ultimately produces less marine life, but also clear water in general. As always, there are notable exceptions and wherever there is a large river run-off, there will be periodic algal blooms which reduce visibility. 

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Male toadfish have to win the right to mate

The toadfish male has a gas-filled organ called a swim bladder, which helps fish maintain neutral buoyancy. By controlling how much oxygen fills its swim bladder, the toadfish can avoid constantly adjusting up or down with flips of its fins, thus saving energy. Sharks, famous for energy conservation, use a similar method, but they don’t have a swim bladder. Instead, they maintain their position with the help of their giant liver, which may make up to 25% of their weight. The male toadfish can vibrate the muscles that attach to the resonating chamber as many as 150 times a second, producing a hum that drives the females mad.

Yet not all male toadfish hum. The males are split into two types, an alpha variety, which actively hums for females, and a so-called sneaker variety. The alphas are 8 times larger than the sneakers, and have swim bladder muscles that are 6 times as big. The sneakers, though, have the alphas beat on testicle size, sporting gonads that are 7 times as large as those of their counterparts.

Why? Well, the alphas maintain nests on the seafloor, and they sing for as long as 2 hours straight with their big, highly developed muscles powering their swim bladders. The female they manage to attract will approach and drop off a batch of eggs, and the alpha will fertilize them and continue to look after the developing young. But a sneaker male will lie silently in wait nearby, then dash in and fertilize the eggs himself. And here’s where the big testicles come to play: the sneaker may get only on chance to fertilize a clutch, so he wants to produce as much sperm as possible in one go. The alphas on the other hand, invest more energy and resources into growing giant to defend their nests. The sneaker avoids using energy to all that stuff - growing outsized, building a nest, calling to the females and looking after the eggs once fertilized. So the genes that make for a clever sneaker toadfish persist through evolutionary time, alongside the pissed off alphas who are doing the actual work.

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Marine flatworms penis-fence their way out of motherhood

In the animal kingdom, males typically have to put in the effort to get laid, but the true biological burden lies with the female, who expends enormous amounts of energy producing eggs, and in the case of mammals, bearing and looking after the young. But what if you’re a hermaphrodite, like some species of marine flatworms? Who’s going to bear the maternal burden then?

Whoever loses the bout of penis fencing, that’s who. In coral reefs, certain species of flatworm do battle with their members. 

It starts off innocently enough. Two often brilliantly colored flatworms approach each other and nuzzle a bit. But soon each rears up and exposes its weapons: two sharp white penises. Each flatworm will stab the other, trying to inject it with sperm anywhere on its body, while doing its best to avoid getting inseminated itself. And this can go on for an hour until the two retract their double penises, lower themselves and go their separate ways. 

When the struggle is over, both can be marked with white stab wounds filled with sperm, and you can see pale streaks running along their bodies: semen on its way to fertilize the eggs. 

This violent process - intradermal hypodermic insemination - has evolved because neither of the flatworms wants to be the female. Developing those eggs is very energy intensive, and the loser is deeply wounded. The winner gets to pass its genes without taking the trouble of raising the young. The most accomplished fencers are the ones who will have the most reproductive success, and their genes are what other flatworms want to pass down to their offspring, who will in turn be more likely to become skillful combatants and fertilizers. It is one of nature’s cruelest ironies: the flatworm doesn’t want to be stabbed with a penis and inseminated, but if it must, it may as well get stabbed with a penis and inseminated thoroughly. 

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Thinning and retreat of West Antarctic glacier began in 1940s

New research by an international team shows that the present thinning and retreat of Pine Island Glacier in West Antarctica is part of a climatically forced trend that was triggered in the 1940s.

The team -- made up of scientists from Lawrence Livermore National Laboratory, the British Antarctic Survey, University of Copenhagen, University of Alaska, Naval Postgraduate School, NASA Goddard Space Flight Center, Lamont-Doherty Earth Observatory of Columbia University, University of Leipzig, University of Geneva and University of Cambridge -- analyzed sediment cores recovered beneath the floating Pine Island Glacier ice shelf. The team concluded the date at which the grounding line retreated from a prominent seafloor ridge was in 1945 at the latest.

The team also found that final ungrounding of the ice shelf from the ridge occurred in 1970.

"Our results suggest that, even when climate forcing (such as El Niños, which create warmer water) weakened, ice-sheet retreat continued," said James Smith of the British Antarctic Survey and lead author of an article appearing in the Nov. 23 issue of the journal, Nature.

The West Antarctic Ice Sheet is one of the largest potential sources of water that will contribute to rising sea levels. Over the past 40 years, glaciers flowing into the Amundsen Sea sector of the ice sheet have thinned at an accelerating rate, and several numerical models suggest that unstable and irreversible retreat of the grounding line -- which marks the boundary between grounded ice and floating ice shelf -- is under way. Understanding this recent retreat requires a detailed knowledge of grounding-line history, but the locations of the grounding line before the advent of satellite monitoring in the 1990s are poorly dated.

Pine Island Glacier, which drains into the Amundsen Sea, has retreated continuously throughout the short period for which there are observational records (from 1992 to the present). The coherent thinning of this and other glaciers along the Amundsen Sea coast indicates a response to external forcing and has been attributed to high basal melting of the floating ice shelves by warm circumpolar deep water. Thinner ice shelves are less able to buttress inland ice, leading to glacier acceleration and ice-sheet thinning.

Evidence gathered by Autosub, an autonomous underwater vehicle operating beneath the ice shelf of Pine Island Glacier, revealed a prominent sea-floor ridge that probably acted as the most recent steady grounding-line position. The earliest visible satellite image, from 1973, showed a bump on the ice surface that was interpreted as the last point of grounding on the highest part of the ridge. The bump had disappeared several years later, suggesting that the present phase of thinning was already underway.

"This finding provided the first hint that the recent retreat could be part of a longer-term process that started decades or even centuries before satellite observations became available," Smith said.

For the study, the team drilled three 20-centimeter holes through the Pine Island Glacier ice shelf during December 2012 and January 2013 to access the ocean cavity below. Sediment cores were recovered at each site. Changes in the lithology and composition of sediment deposited beneath the glacier record the transition from grounded glacier to freely floating ice.

Measurements of lead (Pb-210) and plutonium in the sediment were used to determine when the ice retreat began. Analyses of trace levels of global fallout plutonium in the sediment were performed by high-precision mass spectrometry at LLNL. The appearance of plutonium in the sediment marks the onset of above-ground testing of nuclear weapons in the 1950s, and indicates that ice-sheet retreat began before this time. The Lab's Amy Gaffney contributed to this portion of the study.

"Despite a return to pre-1940s climatic conditions in the ensuing decades, thinning and glacier retreat has not stopped and is unlikely to be reversible without a major change in marine or glaciological conditions," Smith said. "A period of warming in the Antarctic shelf waters triggered a substantial change in the ice sheet, via the mechanism that we see today -- that is, ocean-driven thinning and retreat of ice shelves leads to inland glacier acceleration and ice-sheet thinning."

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Deep sea coral in North Atlantic faces threat from climate change

North Atlantic coral populations - key to supporting a variety of sea life - are under threat from climate change, a study suggests.

Changes to winter weather conditions could threaten the long-term survival of coral in the region, upsetting fragile ecosystems that support an array of marine species, researchers say.

Corals allow diverse forms of marine life to thrive by building reef structures that provide protection from predators and safe spaces to reproduce.

The team focused on a species of cold-water coral - known as Lophelia pertusa - which grows in deep waters, creating elaborate reefs that are hotspots of biodiversity. These populations are maintained by tiny, fragile coral larvae that drift and swim on ocean currents, travelling hundreds of miles between reefs where they attach and begin to grow.

Researchers at the University of Edinburgh used computer models to simulate the migration of larvae across vast stretches of ocean. They did so to predict the effect weather changes could have on the long-term survival of Lophelia pertusa populations in the North Atlantic.

They found that a shift in average winter conditions in western Europe - one of the predicted impacts of climate change - could threaten coral populations. Ocean currents - affected by changing wind patterns - could drive larvae away from key sites in a new network of marine areas established to help safeguard coral populations, researchers say.

The team found Scotland's network of Marine Protected Areas - or MPAs - appears to be weakly connected, making it vulnerable to the effects of climate change. A coral population on Rosemary Bank seamount, an undersea mountain off Scotland's west coast, is key to maintaining the network.

Corals also thrive on oil and gas platforms in the North Sea and west of Shetland, which may help to bridge a gap in the MPA network between populations in the Atlantic and along the coast of Norway, the team says.

The study is published in the journal Royal Society Open Science. It was carried out in collaboration with Heriot-Watt University through a Daphne Jackson fellowship and as part of the ATLAS project, funded by the European Union's Horizon 2020 research and innovation programme.

Dr Alan Fox, of the University of Edinburgh's School of GeoSciences, who conducted the analysis, said: "We can't track larvae in the ocean, but what we know about their behaviour allows us to simulate their epic journeys, predicting which populations are connected and which are isolated. In less well connected coral networks, populations become isolated and cannot support each other, making survival and recovery from damage more difficult."

Professor Murray Roberts, of the University of Edinburgh's School of GeoSciences and co-ordinator of the ATLAS project, said: "Scotland's seabed plays a unique role as a stepping stone for deep-sea Atlantic species. By teaming up with researchers in Canada and the US, we will expand this work right across the Atlantic Ocean."

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Marine microalgae, a new sustainable food and fuel source

Taken from the bottom of the marine food chain, microalgae may soon become a top-tier contender to combat global warming, climate change and food insecurity, according to a study published in the journal Oceanography (December 2016).

"We may have stumbled onto the next green revolution," said Charles H. Greene, professor of earth and atmospheric sciences at Cornell University, and lead author of the new paper, "Marine Microalgae: Climate, Energy and Food Security From the Sea." The study presents an overview of the concept of large-scale industrial cultivation of marine microalgae, or ICMM for short.

ICMM could reduce fossil fuel use by supplying liquid hydrocarbon biofuels for the aviation and cargo shipping industries. The biomass of microalgae remaining after the lipids have been removed for biofuels can then be made into nutritious animal feeds or perhaps consumed by humans.

To make the biofuel, scientists harvest freshly grown microalgae, remove most of the water, and then extract the lipids for the fuel. The remaining defatted biomass is a protein-rich and highly nutritious byproduct -- one that can be added to feeds for domesticated farm animals, like chickens and pigs, or aquacultured animals, like salmon and shrimp.

Growing enough algae to meet the current global liquid fuel demand would require an area of about 800,000 square miles, or slightly less than three times the size of Texas. At the same time, 2.4 billion tons of protein co-product would be generated, which is roughly 10 times the amount of soy protein produced globally each year.

Marine microalgae do not compete with terrestrial agriculture for arable land, nor does growing it require freshwater. Many arid, subtropical regions -- such as Mexico, North Africa, the Middle East and Australia - would provide suitable locations for producing vast amounts of microalgae.

A commercial microalgae facility of about 2,500 acres would cost about $400 million to $500 million. Greene said: "That may seem like a lot of money, but integrated solutions to the world's greatest challenges will pay for themselves many times over during the remainder of this century. The costs of inaction are too steep to even contemplate."

Microalgae's potential is striking. "I think of algae as providing food security for the world," said Greene. "It will also provide our liquid fuels needs, not to mention its benefits in terms of land use. We can grow algae for food and fuels in only one-tenth to one one-hundredth the amount of land we currently use to grow food and energy crops.

"We can relieve the pressure to convert rainforests to palm plantations in Indonesia and soy plantations in Brazil," Greene said. "We got into this looking to produce fuels, and in the process, we found an integrated solution to so many of society's greatest challenges."

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Rockfish siblings shed new light on how offspring diffuse and disperse

A splitnose rockfish's thousands of tiny offspring can stick together in sibling groups from the time they are released into the open ocean until they move to shallower water, research from Oregon State University shows.

The study conducted in the OSU College of Science sheds new light on how rockfish, a group of multiple species that contribute to important commercial and recreational fisheries in the Northwest, disperse through the ocean and "recruit," or take up residence in nearshore habitats. Previously it was believed rockfish larvae dispersed chaotically to wherever currents carried them.

"When you manage populations, it's really important to understand where the young are going to and where the young are coming from - how populations are connected and replenished," said Su Sponaugle, a professor of integrative biology based at OSU's Hatfield Marine Science Center. "This research helps us better understand what's possible about offspring movement. We don't know fully by what mechanisms the larvae are staying together, but these data are suggestive that behavior is playing a role."

The findings were published today in Proceedings of the National Academy of Sciences. Primary funding came from the Hatfield Marine Science Center's Mamie L. Markham Research Award.

The discovery of "spatial cohesion" among the larvae came via the collection of newly settled rockfish in a shallow nearshore habitat off the central Oregon coast. Nearly 500 juvenile fish that had started out up to six months earlier as transparent larvae at depths of a few hundred meters were collected and genetically analyzed, with the results showing that 11.6 percent had at least one sibling in the group.

"That's much higher than we would have expected if they were randomly dispersing," Sponaugle said.

Bearing live young - a female can release thousands of able-to-swim larvae at a time - and dwelling close to the sea floor in the benthic zone, rockfishes make up a diverse genus with many species.

Adult splitnose rockfish live in deep water - usually 100 to 350 meters - but juveniles often settle in nearshore habitats less than 20 meters deep after spending up to a year in the open sea. Taking into account dynamic influences such as the California Current, siblings recruiting to the same area suggest they remained close together as larvae rather than diffusing randomly and then reconnecting as recruits.

"This totally changes the way we understand dispersal," said lead author Daniel Ottmann, a graduate student in integrative biology at the Hatfield Marine Science Center. "We'd thought larvae were just released and then largely diffused by currents, but now we know behavior can substantially modify that."

Splitnose rockfish range from Alaska to Baja California and can live for more than 100 years. Pelagic juveniles - juveniles in the open sea - often aggregate to drifting mats of kelp, and the large amount of time larvae and juveniles spend at open sea is thought to enable them to disperse great distances from their parental source.

"This research gives us a window into a stage of the fishes' life we know so little about," added Kirsten Grorud-Colvert, an assistant professor of integrative biology at OSU's Corvallis campus. "We can't track the larvae out there in the ocean; we can't look at their behavior early and see where they go. But this genetic technique allows us to look at how they disperse, and it changes the conversation. Now that we know that siblings are ending up in the same places, we can consider how to more effectively manage and protect these species."

Because larval aggregation shapes the dispersal process more than previously thought, Ottmann said, it highlights the need to better understand what happens in the pelagic ocean to affect the growth, survival and dispersal of the larvae.

"Successful recruitment is critical for the population dynamics of most marine species," he said. "Our findings have far-reaching implications for our understanding of how populations are connected by dispersing larvae."

In addition, Grorud-Colvert adds, there's the simple and substantial "gee whiz" factor of the findings.

"These tiny little fish, a few days old, out there in the humongous ocean, instead of just going wherever are able to swim and stay close together on their epic journey," she said. "These tiny, tiny things, sticking together in the open ocean - it's cool."

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Filefish: Now you see it. Now you don’t.

Species: The slender filefish (Monacanthus tuckeri) Habitat: Shallow waters in the Caribbean Sea

The slender filefish has a way to stay off the seafood menu – it has evolved the ability to become almost invisible. The fish can camouflage its body patterns and shape to match its marine surroundings in seconds (see video).

The small fish lives near soft corals on reefs and feeds on small crustaceans and zooplankton. But larger predators are on the lookout for a filefish snack.

To see an object for what it is, you need to be able to perceive its edges, which mark it out as being separate from the background. The filefish changes its coloration to create "false edges". For example, it can make a dark, longitudinal stripe appear on its body that looks like a real edge. The eye sees this false edge, and so can miss the true outline of the fish. And if you don't see the real outline, you won't recognize what's in front of you.

To alter its patterning, the fish gathers visual information from its surroundings, then its brain signals to pigment-containing cells in the skin. Depending on the signal, the pigment can either aggregate at the center of cells, covering a smaller area of the skin, or disperse to cover a larger area. The fish also has small, protruding skin projections, called dermal flaps that help it hide itself from others. They make the physical edges of the fish look less smooth or "fishlike" and more jagged and complicated. The dermal flaps often resemble underwater structures such as coral polyps, small clumps of sand or bits of algae.

This is enough to confuse predators and even practiced researchers.

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Propagule predation by crabs limits establishment of an endemic mangrove

Crabs love mangrove swamps. But the mangroves may not love them back. The crabs' voracious appetite for mangrove seeds can be a prime reason why efforts to replant lost mangroves often fail. So keeping crabs out could sometimes help their recovery, says Emily Dangremond of the University of California in Berkeley.

To see how much mangrove the crabs can munch through, she used nylon mesh enclosures to keep crabs away from mangrove seeds in areas of swamp regrowth on the Pacific and Caribbean coasts of Panama in Central America.

Comparing these areas with similar regions where crabs were free to roam, she found that their consumption varied depending on the type of mangroves around, and they ate more in saltier waters. In the worst cases, they munched up to 90% of the seeds of the rare neotropical mangrove tree, Pelliciera rhizophorae. Hungry crabs prevented new seedlings from establishing in the muddy swamp beds, effectively limiting their populations.

Mangroves are vital parts of many coastal ecosystems in the tropics. They grow widely in brackish lagoons and provide coastal communities with protection against storms – even tsunamis. They also nurture fish stocks and act as carbon stores (http://diariesoftheocean.tumblr.com/post/118470018289/why-oceans-matter-episode-2)

But many have been destroyed in recent decades. Mangroves are disappearing at rates three times as fast as tropical rainforests.

Major programs are under way around the world to revive lost mangrove swamps. Many have failed, however, and the reasons have often been unclear. Some foresters have blamed crabs, but there was previously little experimental evidence to back this suspicion.

Dangremond's findings put crabs firmly in the frame for restoration failures and provide a strong case for keeping crabs out of mangroves to help their re-establishment.

"People often attempt restoration projects by planting mangrove propagules (seeds). In those cases, it might be useful to exclude crabs," says Dangremond.  

 However, not everyone agrees that interfering with the crab-mangrove interactions is the best way to get healthy mangrove forests. Some scientists argue that mangroves and crabs have evolved together for millions of years and they need each other.  Crabs keep essential nutrients within the mangrove system. They also dig burrows that oxidize the sediment.

Excluding crabs would probably be unpopular with the locals, too. Many coastal communities harvest crabs from mangrove swamps. Indeed, many see the crab harvest as an important reason for protecting mangroves.

Journal reference: Hydrobiologia, DOI: 10.1007/s10750-015-2238-9

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Environmental threats and the future of estuaries

Among the most important environments of the coastal zone are estuaries, which constitute transition zones or ecotones, where fresh water from land drainage mixes with seawater, creating some of the most biologically productive areas on Earth. These complex systems vary considerably in geomorphology, hydrography, salinity, tidal characteristics, sedimentation, and ecosystem energetics. As a result, biotic communities also differ substantially in estuarine systems.

Estuaries have been defined repeatedly in the literature. The definition of Pritchard (1967) states that an estuary is a semi-enclosed coastal body of water with a free connection to the open sea and within which seawater is measurably diluted with fresh water derived from land drainage.

Numerous anthropogenic perturbations affect estuarine environments, contributing to habitat alteration and changes in the structure and dynamics of biotic communities. Environmental problems encountered in these systems invariably stem from overpopulation and uncontrolled development in coastal watersheds, as well as human activities in the estuarine embayment themselves. Human activities are significantly altering estuarine systems worldwide, threatening their resources and the commercial and recreational uses dependent on them. It is necessary, therefore, to identify the major anthropogenic activities impacting estuaries and to recommend remedial actions for improving the health and viability of these systems. Included among the most serious stress factors in the estuarine environment are pollution inputs (e.g. nutrient enrichment, organic carbon loading, and chemical contaminants) and several other anthropogenic factors (e.g. habitat loss and alteration, overfishing, freshwater diversions, and introduced species).

 Estuaries exhibit a wide array of human impacts that can compromise their ecological integrity, because of rapid population growth and uncontrolled development in many coastal regions worldwide. Long-term environmental problems plaguing estuaries require remedial actions to improve the viability and health of these valuable coastal systems. Detailed examination of the effects of pollution inputs, the loss and alteration of estuarine habitat, and the role of other anthropogenic stress indicates that water quality in estuaries, particularly urbanized systems, is often compromised by the overloading of nutrients and organic matter, the influx of pathogens, and the accumulation of chemical contaminants. In addition, the destruction of fringing wetlands and the loss and alteration of estuarine habitats usually degrade biotic communities. Estuaries are characterized by high population densities of microbes, plankton, benthic flora and fauna, and nekton; however, these organisms tend to be highly vulnerable to human activities in coastal watersheds and adjoining embayments. Trends suggest that by 2025 estuaries will be most significantly impacted by habitat loss and alteration associated with a growing coastal population. Habitat destruction has far reaching ecological consequences, modifying the structure, function, and controls of estuarine ecosystems and contributing to the decline of biodiversity. Other anticipated high priority problems are excessive nutrient and sewage inputs to estuaries, principally from land-based sources. These inputs will lead to the greater incidence of eutrophication as well as hypoxia and anoxia. During the next 25 years, overfishing is expected to become a more pervasive and significant anthropogenic factor, also capable of mediating global-scale change to estuaries. Chemical contaminants, notably synthetic organic compounds, will remain a serious problem, especially in heavily industrialized areas.

Freshwater diversions appear to be an emerging global problem as the expanding coastal population places greater demands on limited freshwater supplies for agricultural, domestic, and industrial needs. Altered freshwater flows could significantly affect nutrient loads, biotic community structure, and the trophodynamics of estuarine systems. Ecological impacts that will be less threatening, but still damaging, are those caused by introduced species, sea level rise, coastal subsidence, and debris/litter. Although all of these disturbances can alter habitats and contribute to shifts in the composition of estuarine biotic communities, the overall effect will be partial changes to these ecosystem components. Several strategies may mitigate future impacts.

[diariesoftheocean]

The misconception surrounding sharks

Forty years ago this summer, moviegoers met an animal that "lives to kill ... a mindless eating machine ... that will swallow you whole." Those words, from the trailer for the June 1975 release of Jaws, helped establish the erroneous, and sadly, enduring image of sharks as vicious, voracious man-eaters.

In the decades since the release of Jaws, the number of sharks in the world's oceans has fallen dramatically. It is estimated that approximately 100 million sharks are killed every year, a deeply unsustainable number that is pushing some species toward extinction. Silky sharks and hammerhead sharks have been hunted to less than 20 percent of their former population size over much of their range, and oceanic whitetips have declined by over 99 percent in some regions. Many other types of sharks aren't faring much better, and immediate global action is needed to save them.

The precipitous decline in sharks is due mainly to demand for shark fin soup in China, where it is considered a delicacy and a symbol of wealth and success. The demand for fins threatens sharks worldwide, from the Caribbean and Mediterranean Seas to the Indian, Atlantic and Pacific Oceans.

Tens of millions of sharks are either caught intentionally, or are inadvertently caught by fishermen seeking other fish, such as tuna or swordfish. This is referred to as bycatch or accidental catch. In most cases, it is not really accidental at all. It is the result of indiscriminate fishing gear that almost always catches fish that are of no interest to fishermen and, as a result, are frequently thrown back into the ocean, dead or dying. One of the most widespread and destructive of these gears consists of monofilament line that can stretch up to 70 kilometers behind a fishing vessel, baited with thousands of hooks. Seabirds, sea turtles and a host of other species are also hooked as they attempt to take the bait, dragged under the water and drowned.

The widespread killing of sharks must be stopped if these apex predators are to remain in the world's oceans. Their continued presence is important for many reasons, chief of which is the role they play in maintaining the balance of marine ecosystems. Like apex predators everywhere, they weed out the weak and the sick among the populations they prey on, and in so doing, help to ensure an appropriate balance of life in the marine food web.

Sharks grow slowly, reproduce relatively late in life, and have few young, factors that could put them on a fast track to extinction without aggressive conservation measures. Such efforts should cover three fronts: reducing demand for shark products; establishing strong protections to safeguard sharks; and rigorously enforcing the laws that protect sharks.

The good news is that we are starting to see progress in all of these areas. In March 2013, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) listed five species of sharks — oceanic whitetip, porbeagle and three species of hammerheads — that cannot be traded without CITES permits and evidence that the animals were caught sustainably and legally. Pew and other concerned groups fought hard to secure these listings, and a global effort is underway to ensure they are effectively implemented.

Nearly 70 percent of Hong Kong residents surveyed in 2014 have reduced or entirely stopped consuming shark fin soup, according to research conducted by Bloom Association and Hong Kong University. That reflects a trend that has also seen major hotel and restaurant chains in China and other parts of Southeast Asia swear off a dish that has long been featured on wedding menus.

And the Bahamas, the British Virgin Islands, the Cook Islands, the Federated States of Micronesia, French Polynesia, Honduras, the Maldives, the Marshall Islands, New Caledonia and Palau have all agreed to create shark sanctuaries that together encompass nearly 10 million square kilometers of ocean.

Jaws author Peter Benchley, who argued passionately for the protection of sharks for years until his death in 2006, said frequently that he regretted the widespread fear of sharks generated by his book and the movie. In one of his many public laments on the topic, Benchley said, "Sharks don't target human beings, and they certainly don't hold grudges."

[diariesoftheocean]

Mediterranean Sea Biodiversity - part 1

The Mediterranean Sea is a biodiversity hotspot containing between 15,000 and 20,000 marine species, nearly a quarter of which are endemic. The causes of the high Mediterranean biodiversity lie primarily in the turbulent geological history of the basin during the Tertiary and in the dramatic climatic fluctuations of the Quaternary. Both induced a rate of environmental change, and hence species occurrence, which acted as a biodiversity pump. As a result, species with different biogeographic origins and affinities are found in the basin. Although the Mediterranean Sea as a whole constitutes a distinctive province of the Atlantic-Mediterranean biogeographic region, a great variety of climatic and hydrologic situations is found in its fairly isolated sub-basins. Thus, 12 different biogeographic sectors can be recognized: Alboran Sea; Algeria and north Tunisia coasts; Tyrrhenian Sea; Balearic Sea to Sardinia Sea; Gulf of Lions and Ligurian Sea; northern Adriatic Sea; central Adriatic Sea; southern Adriatic Sea; Ionian Sea; Levant Sea; southern Aegean Sea; northern Aegean Sea.

The high biodiversity of the Mediterranean Sea may be explained by historical, paleogeographic, and ecological reasons. Paleogeographic reasons are probably most important, as the whole basin has experienced a turbulent geological history which has led to an enhanced rate of environmental change, and hence species occurrence, with few equals in the world.

The Mediterranean Sea is frequently, although rather imprecisely, considered as the right heir of the ancient Tethys Sea.

The Tethys was a once-extensive, wedge-shaped, eastward-opening equatorial ocean that indented Pangea in the Mesozoic. Towards the end of the Mesozoic, in the Cretaceous, the Tethys came to separate the two supercontinents of Laurasia to the north and Gondwana to the south. The expansion of the Tethys became the Mesogea, a sea stretching between the two supercontinents. After the opening of the Atlantic Ocean, the Mesogea was connecting, through an uninterrupted equatorial belt (the so-called Tethyan seaway), the newly born ocean to the older Indo-Pacific Ocean (the ancestral Panthalassa).

According to geological reconstruction, the ultimate fate of the Tethys has been sealed by plate tectonics. Today’s configuration of the Tethys is the formation of remnant and successor seas, including the Gulf of Mexico, the Caribbean, the Mediterranean, the Red Sea and the intertropical zone of the Indian Ocean. A significant portion of the former Tethys, however, uplifted during the Cenozoic geodynamic evolution marked by the Alpine orogeny, which practically ended in the Oligocene. The formation of the Alps, Carpathians, Dinarides, Taurus and Elburz mountains separated the main body of the Tethys, to the south, from the Paratethys, to the north.

The Paratethys was a large shallow sea that spread over a large area from Central Europe to western Asia. The Black Sea, the Caspian Sea and the Aral Sea are all that is left of that once vast inland sea.

The overall convergence of Africa and Eurasia, which involved several successive local rifting processes and collisions during the Tertiary, led to the shrinkage of the Tethys in the Oligocene. The consequent diminution of its warming influence in the world oceans produced cold water conditions elsewhere. This may have resulted in higher extinction rates outside the Tethys and the Indo-west Pacific than within these regions. At that time, the Tethys was harboring a highly diverse warm-water biota. Throughout most of its geological history, Tethys had been the global center of marine biodiversity - a role assumed today by the area between the Philippines and Indonesia. Can the high biodiversity of the present-day Mediterranean Sea be directly linked to that of its Mesozoic ancestors? The answer is probably no.

Up to the Burdigalian, in the Miocene, the connection between the shrunken Mesogean Tethys, which in a sense could be considered as the first sketch of the Mediterranean, and the Indo-pacific to the east and the Atlantic to the west was maintained. However, the between the Indo-West Pacific and the Caribbean-East Pacific biogeographic regions. The connection that previously existed between the proto-Mediterranean and the Indian Ocean in the area of the Mesopotamian trough ceased when the Isthmus of Suez was raised during the Miocene orogeny.

Marine interconnections only remained in the west, leaving the Atlantic as the only biological reservoir for the adjacent proto-Mediterranean. The marine biota of the Tethys was typically tropical. Coral reefs were present up to the Tortonian. Towards the end of the Miocene, the connection with the Atlantic was also interrupted on several occasions, and the Mediterranean become a virtually isolated sea, with a degree of enclosure of over 99 %. The segregation of the Mediterranean basin from the Atlantic took place because of the closure of the Betic and Rif straits, roughly in the same region as today’s Gibraltar. The negative water balance should have nearly desiccated the Mediterranean, which was probably transformed into a series of large evaporitic lakes during the so-called ‘salinity crisis’ at the end of the Messinian age.

The reconstruction of the series of events that accompanied the Messinian salinity crisis has been the object of many controversies and differing interpretations. Most authors, however, agree that within about six hundred thousand years the Mediterranean, which was secluded from free hydrological exchanges with the world ocean, shifted from anoxic pre-evaporitic to evaporitic hyperhaline, then to hypohaline conditions. After the main phase of massive evaporite precipitation, the ending of the Messinian salinity crisis was characterized by the so-called ‘Lago Mare (= Lake Sea) event’, i.e. the progressive and generalized establishment of brackish to freshwater aquatic environments throughout the Mediterranean, possibly linked to the flow of the brackish waters of Paratethys into the dry basins.

The peculiar hydrological conditions of the isolated Mediterranean during the Messinian salinity crisis should have produced dramatic effects on the biota of ancient Tethyan origin. Again, there is not general consensus about what happened. Some authors believe that the biota was completely annihilated, others consider that at least part of it may have survived through the Neogene. Survival of Tethyan biota should have been possible in fully marine refuges that may have persisted from permanent links with the Atlantic via the Betic portal or in satellite basins within the western Mediterranean, possibly in southern Spain. The existence of seaways between the eastern Mediterranean and some oceans at that time has also been postulated.

Possibly, it is from the remnants of the Tethyan biota that what are today called the Mediterranean paleoendemics should have evolved. Alleged Mediterranean paleoendemics are known in invertebrate groups and have especially been described among macrophytes.

The idea that during the Messinian high salinity crisis all the marine life of the Mediterranean was exterminated is not correct. Marine life, with many documented examples especially in echinoderms and fishes, survived into the Pliocene in near-shore environments. The classical Tethyan relic, a Messinian survivor, is the endemic Mediterranean seagrass Posidonia oceanica, which however did not leave any fossil evidence in the Mediterranean basin prior to the lower Pleistocene.