Evidences accumulated over the last few decades reveal a growing human impact on marine ecosystems, but effects on biological communities are still largely unknown.

Human activities such as fisheries, urban development, tourism, and maritime traffic, greatly influence distribution and quantity of marine litter from shores to deeper regions of continental margins, where may enter directly through a wide variety of maritime activities including disposal (e.g. clinker, sewage, chemical products or radioactive materials) and exploitation of natural resources (e.g. lost fishing gears, oil and gas, mining, pipelines). Any material discarded, disposed, or abandoned at the coast or even far inland can potentially become marine debris!

Today, we have evidences that terrestrial human activities are the main source of marine debris worldwide and are responsible for 70-80% of all debris that end up in the ocean dragged by the wind, rain, and tides or transported by rivers.

Anthropogenic litter has been accumulating in marine environments from heavily populated coastlines to remote shorelines in high latitudes, floating on the surface or sunk at the bottom of the oceans. In fact, plastic materials and glass are frequently observed in marine ecosystems along coasts, continental margins and even in the deep abyssal plains.

Accumulation of plastics has harmful consequences for marine animals (seabirds, turtles, mammals, fishes, but also corals and sponges), to which ingestion, strangulation and obstruction of respiratory or digestive systems, led most of the times to permanent damage or dead. 

Since human impact on the deep sea confirms the significant threat to its biodiversity, societal awareness is fundamental to take effective actions for the conservation of vulnerable habitats so that they can continue contributing to healthy and productive oceans.

The post Human footprint along marine ecosystems   appeared first on Exploring our Oceans .

Pelagic zonation

Environmental conditions at mesopelagic depths are very particular showing dim light, cold waters and low oxygen levels, reduced turbulence, increased hydrostatic pressure, high inorganic nutrient concentrations and irregular food supply.

Mesopelagic fishes are well adapted to these conditions: they show bigger and more sensible eyes, dark or silver bodies, and luminous organs called photophores. Bioluminescence is the most common communication mode in the deep pelagic zone, being used in predation, defense (camouflage) and communication (mating, warning the presence of predators, migrations). Many mesopelagic fish species have also the capacity to adjust the intensity or color of the light emitted by their photophores. Bioluminescence may occur by symbiosis with bioluminescent organisms, such as bacteria (less frequently in fishes), or due to the oxidation of light emitting molecules (luciferin).

Most mesopelagic species perform extensive diel vertical migration (DVM) between the surface and 1000 m depth, moving at night into the epipelagic zone, following similar migrations of zooplankton, and returning to greater depths during the day to avoid predators. They also play an important role in biogeochemical cycles, transporting organic matter from the epipelagic zone, to greater depths and fuelling the benthic fish communities.

Families Myctophidae, Gonostomatidae, Stomiidae and Gempylidae are the most diverse and exhibit a global distribution, the first two being the most abundant.

Some features:

– Mesopelagic fishes are the most abundant vertebrates on earth.

– Inhabit the mesopelagic zone of all oceans.

– Bristlemouth fishes (belongs to family Gonostomatidae represented by 8 genera and 32 species) and lanternfishes (Family Myctophidae divided in 38 genera and approx. 250 species.) are the most abundant.

– Gonostomatidae and Myctophidae accounts for over 90% of the trawl catches at pelagic depths

– They exhibit reduced size (2.5-10 cm)

– Perform daily vertical migration between the surface and 1000 m

– Feed on zooplankton

– Some mesopelagic fish species use bioluminescent appendages to attract prey

– Others have large and extensible jaws to capture larger prey

References:

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I am Rui and I am going to talk a little about my PhD project.

I am a second year PhD student at the National Oceanography Centre in Southampton and my main research interests are deep-sea ecology, biological oceanography and taxonomy. My project aims to understand deepwater ecosystems functioning and the effects of human-induced changes along continental slopes. To answer this questions I will 1) analyse aspects of trophic ecology of deep-water fishes, and 2) quantify the impacts of trawling on benthic communities in the Porcupine Seabight and south coast of Portugal through detailed image analysis and historical fishery records.

The study of deepwater fishes trophic ecology is important to identify food sources and feeding relationships. This is used to understand links between species and different ecosystems and is a useful tool assess the true impact of human-induced activities along the seabed. Also, comparing visual records of benthic communities in areas subject to different levels of trawling over time series will allow a quantitative assessment of the impact of fisheries on the abundance and diversity of benthic organisms and ecosystems health.

“But how does he study the trophic ecology of deep-water fishes?” Perhaps this comes to your mind… and yes, this is a good question! I am using a novel approach that will allow me to know more about these deepwater fishes. Analyzing geochemical tracers from fish muscle, called stable isotopes, I will be able know what fishes are feeding, their ecological role and relationships, and their position in trophic foodwebs.

Later I will study the impacts of human activities in the deep sea. Using underwater photography and video, I will be able to directly see and quantify the impacts of trawling on benthic communities, particularly deepwater sponges.

I will also investigate historical fishery records of the crustacean trawl fishery off the Algarve coast (southern Portugal). This multispecies fishery is characterised by a significant by-catch and discarding of numerous species and the available historical data will be compared with the current status of these fishing grounds in order to evaluate impacts of trawling on marine biodiversity.

I hope you find it interesting. Find me @rui_pedro19

Images collected during the JC062 Cruise in the Porcupine Seabight.

The post My Research: Rui Pedro Vieira appeared first on Exploring our Oceans .

“Fearsome-looking creatures that live in the near-dark to pitch-black waters of the deep sea, dragon fish wouldn’t seem to have much need for eyes, let alone the ability to see color. However, some dragon fish have rapidly evolved from blue-light sensitivity to red-light sensitivity, and then back to blue again.

The deep sea is not the sort of environment that would appear to encourage rapid evolution. “It doesn’t change. It is always dark,” said study researcher Christopher Kenaley, a comparative biologist at Harvard University. “There is something else down there that is driving the evolution of the visual system.”

The force driving these changes is likely the bioluminescence produced by the dragon fish themselves as well as by other deep-sea creatures, he said.

Dragon fish, which have outsized jaws and teeth that belie their small size, live between about 650 to 6,600 feet (200 to 2,000 meters) beneath the ocean’s surface. About 95 percent of animals in that region can see blue light, which the creatures also produce through bioluminescence. Deep-sea animals, including dragon fish, glow in order to lure prey, communicate with one another or camouflage themselves against the dim light from the surface. Some dragon fish sport lures known as barbels with glowing fibers that resemble blue fiber-optic lights. [A Glow in the Dark Gallery]

Although blue is the default shade of the deep sea, nine species of dragon fish appear to be able to see and bioluminesce in red.

Blue to red and back

To reconstruct the fishes’ family history, researchers looked at variations in the sequences that code for the light-sensitive pigment rhodopsin as well as three other genes in samples from 23 groups of dragon fish. (Rhodopsin is not unique to dragon fish; also present in humans, this pigment makes it possible for people to see in dim light.) To clarify when in evolutionary history the different groups of fish split, the researchers used the estimated ages of fossil fish. These established a minimum age for the part of the evolutionary tree into which the fossils fit.

Researchers concluded that red vision evolved once in dragon fish, about 15.4 million years ago. Red-seeing species emit far-red light, which falls at the edge of the spectrum visible to humans. To emit this light, the species use organs called photophores typically located in front of the eye. While the red light can’t act as a lure, since most of the animals’ prey can’t see that shade, it does allow the dragon fish to stealthily illuminate their prey. [Creepy Deep Sea Creatures]

One of these red-seeing species, known as the stoplight loose jaw, still has a blue-green photophore it uses to attract prey before lunging at them with its lower jaw.

About 4 million years ago, some of the red-seeing fish went back to blue. This reversion happened in the “bat of an eye in geological time,” Kenaley told Live Science. The analysis the team conducted indicates that two modern groups of blue-seeing dragon fish once had ancestors that relied on red.

“We now understand that visual evolution can be very rapid in a very stabile sensory environment,” he said.

Making their own light

Bioluminescence is likely driving the changes in vision, Kenaley said. These creatures co-opted an enzyme called coelenterazine. Used by vertebrates to neutralize free radicals, coelenterazine emits photons, or particles of light. After being filtered by the photophore and its tissue, the light that emerges is blue. What’s more, blue light travels further into the deep ocean than other wavelengths do, so it makes sense that deep-sea fish would evolve to see that hue.

The dragon fish that emit red bioluminescence seem to have tweaked the process used to produce blue light, and the evolution of this ability to produce red likely drove the evolution of the ability to see it. Meanwhile, those fish that regained the ability to see in blue may have done so in order to effectively find mates or lure blue-seeing prey, Kenaley said.

This study contradicts previous research that suggested the ability to see red light evolved at least twice independently. Meanwhile, other genetic research grouped blue- and red-seeing fish separately and found no evidence that a red-seeing ancestor reverted to blue.”

(text by Wynne Parry)

The post Red-Seeing Fish, Blue-Seeing Fish: Deep-Sea Vision Evolves appeared first on Exploring our Oceans .

Lots of nice words about the ocean for the cloud.

But what about animals? Share with us the first marine animal that come into your mind. From the shore into the abyss, let’s see which one is more popular.

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