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This story appears in the February 2011 issue of National Geographic magazine.
Most of us will never get to see nature's greatest marvels in person. We won't get a glimpse of a colossal squid's eye, as big as a basketball. The closest we'll get to a narwhal's unicornlike tusk is a photograph. But there is one natural wonder that just about all of us can see, simply by stepping outside: dinosaurs using their feathers to fly.
Birds are so common, even in the most paved-over places on Earth, that it's easy to take for granted both their dinosaur heritage and the ingenious plumage that keeps them aloft. To withstand the force of the oncoming air, a flight feather is shaped asymmetrically, the leading edge thin and stiff, the trailing edge long and flexible. To generate lift, a bird has merely to tilt its wings, adjusting the flow of air below and above them.
Airplane wings exploit some of the same aerodynamic tricks. But a bird wing is vastly more sophisticated than anything composed of sheet metal and rivets. From a central feather shaft extends a series of slender barbs, each sprouting smaller barbules, like branches from a bough, lined with tiny hooks. When these grasp on to the hooklets of neighboring barbules, they create a structural network that's featherlight but remarkably strong. When a bird preens its feathers to clean them, the barbs effortlessly separate, then slip back into place.
The origin of this wonderful mechanism is one of evolution's most durable mysteries. In 1861, just two years after Darwin published Origin of Species, quarry workers in Germany unearthed spectacular fossils of a crow-size bird, dubbed Archaeopteryx, that lived about 150 million years ago. It had feathers and other traits of living birds but also vestiges of a reptilian past, such as teeth in its mouth, claws on its wings, and a long, bony tail. Like fossils of whales with legs, Archaeopteryx seemed to capture a moment in a critical evolutionary metamorphosis. "It is a grand case for me," Darwin confided to a friend.
The case would have been even grander if paleontologists could have found a more ancient creature endowed with more primitive feathers—something they searched for in vain for most of the next century and a half. In the meantime, other scientists sought to illuminate the origin of feathers by examining the scales of modern reptiles, the closest living relatives of birds. Both scales and feathers are flat. So perhaps the scales of the birds' ancestors had stretched out, generation after generation. Later their edges could have frayed and split, turning them into the first true feathers.
It made sense too that this change occurred as an adaptation for flight. Imagine the ancestors of birds as small, scaly, four-legged reptiles living in forest canopies, leaping from tree to tree. If their scales had grown longer, they would have provided more and more lift, which would have allowed the protobirds to glide a little farther, then a little farther still. Only later might their arms have evolved into wings they could push up and down, transforming them from gliders to true powered fliers. In short, the evolution of feathers would have happened along with the evolution of flight.
This feathers-led-to-flight notion began to unravel in the 1970s, when Yale University paleontologist John Ostrom noted striking similarities between the skeletons of birds and terrestrial dinosaurs called theropods, a group that includes marquee monsters like Tyrannosaurus rex and Velociraptor. Clearly, Ostrom argued, birds were the living descendants of theropods. Still, many known theropods had big legs, short arms, and stout, long tails—hardly the anatomy one would expect on a creature leaping from trees. Other paleontologists argued that birds did not evolve from dinosaurs—rather, their similarities derived from a shared common ancestor deeper in the past.
In 1996 Chinese paleontologists delivered startling support for Ostrom's hypothesis. It was the fossil of a small, short-armed 125-million-year-old theropod, Sinosauropteryx, which had one extraordinary feature: a layer of thin, hollow filaments covering its back and tail. At last there was evidence of truly primitive feathers—found on a ground-running theropod. In short, the origin of feathers may have had nothing to do with the origin of flight.
Soon paleontologists were finding hundreds of feathered theropods. With so many fossils to compare, they began piecing together a more detailed history of the feather. First came simple filaments. Later, different lineages of theropods evolved various kinds of feathers, some resembling the fluffy down on birds today, some having symmetrically arranged barbs. Other theropods sported long, stiff ribbons or broad filaments, unlike the feathers on any living birds.
The long, hollow filaments on theropods posed a puzzle. If they were early feathers, how had they evolved from flat scales? Fortunately, there are theropods with threadlike feathers alive today: baby birds. All the feathers on a developing chick begin as bristles rising up from its skin; only later do they split open into more complex shapes. In the bird embryo these bristles erupt from tiny patches of skin cells called placodes. A ring of fast-growing cells on the top of the placode builds a cylindrical wall that becomes a bristle.
Reptiles have placodes too. But in a reptile embryo each placode switches on genes that cause only the skin cells on the back edge of the placode to grow, eventually forming scales. In the late 1990s Richard Prum of Yale University and Alan Brush of the University of Connecticut developed the idea that the transition from scales to feathers might have depended on a simple switch in the wiring of the genetic commands inside placodes, causing their cells to grow vertically through the skin rather than horizontally. In other words, feathers were not merely a variation on a theme: They were using the same genetic instruments to play a whole new kind of music. Once the first filaments had evolved, only minor modifications would have been required to produce increasingly elaborate feathers.
Until recently it was thought that feathers first appeared in an early member of the lineage of theropods that leads to birds. In 2009, however, Chinese scientists announced the discovery of a bristly-backed creature, Tianyulong, on the ornithischian branch of the dinosaur family tree—about as distant a relative of theropods as a dinosaur can be. This raised the astonishing possibility that the ancestor of all dinosaurs had hairlike feathers and that some species lost them later in evolution. The origin of feathers could be pushed back further still if the "fuzz" found on some pterosaurs is confirmed to be feathers, since these flying reptiles share an even older ancestor with dinosaurs.
There's an even more astonishing possibility. The closest living relatives of birds, dinosaurs, and pterosaurs are crocodilians. Although these scaly beasts obviously do not have feathers today, the discovery of the same gene in alligators that is involved in building feathers in birds suggests that perhaps their ancestors did, 250 million years ago, before the lineages diverged. So perhaps the question to ask, say some scientists, is not how birds got their feathers, but how alligators lost theirs.
If feathers did not evolve first for flight, what other advantage could they have provided the creatures that had them? Some paleontologists have argued that feathers could have started out as insulation. Theropods have been found with their forelimbs spread over nests, and they may have been using feathers to shelter their young.
Another hypothesis has gained strength in recent years: that feathers first evolved to be seen. Feathers on birds today come in a huge range of colors and patterns, with iridescent sheens and brilliant streaks and splashes. In some cases their beauty serves to attract the opposite sex. A peacock unfolds his iridescent train, for instance, to attract a peahen. The possibility that theropods evolved feathers for some kind of display got a big boost in 2009, when scientists began to take a closer look at their structure. They discovered microscopic sacs inside the feathers, called melanosomes, that correspond precisely in shape to structures associated with specific colors in the feathers of living birds. The melanosomes are so well preserved that scientists can actually reconstruct the color of dinosaur feathers. Sinosauropteryx's tail, for example, appears to have had reddish and white stripes. Perhaps the males of the species flashed their handsome tails when courting females. Or perhaps both sexes used their stripes the way zebras use theirs—to recognize their own kind or confuse predators.
Whatever the original purpose of feathers, they were probably around for millions of years before a single lineage of dinosaurs began to use them for flight. Paleontologists are now carefully studying the closest theropod relatives of birds for clues to how this transition occurred. One of the most revealing is a recently discovered wonder called Anchiornis, more than 150 million years old. The size of a chicken, it had arm feathers with black-and-white portions, creating the spangled pattern you might see on a prize rooster at a county fair. On its head it wore a gaudy rufous crown. In structure, Anchiornis's plumes were nearly identical to flight feathers, except that they were symmetrical rather than asymmetrical. Without a thin, stiff leading edge, they may have been too weak for flight.
What the plumes lacked in strength, however, they made up for in number. Anchiornis had an embarrassment of feathers. They sprouted from its arms, legs, and even its toes. It's possible that sexual selection drove the evolution of this extravagant plumage, much as it drives the evolution of peacock trains today. And just as their long, heavy trains pose a burden to peacocks, the extravagant feathers of Anchiornis may have been a bit of a drag, literally.
Corwin Sullivan and his colleagues at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing have found a way that Anchiornis could have overcome this problem. In the theropods that were closely related to living birds, a particular wristbone was wedge-shaped, allowing them to bend their hands. Anchiornis's wrist bone was so wedge-shaped that it could fold its arms to its sides, keeping its arm feathers off the ground as it walked. Modern birds use a similar bone in flight, drawing their wings toward their bodies during an upstroke. If Sullivan and his colleagues are right, this crucial flight feature evolved long before birds took wing. It's an example of what evolutionary biologists call exaptation: borrowing an old body part for a new job. It now looks like bird flight was made possible by a whole string of such exaptations stretching across millions of years, long before flight itself arose.
The way in which that final transition occurred continues to inspire lively debate. Some scientists argue that feathered dinosaurs evolved flight from the ground up, flapping their feathered arms as they ran. Others challenge this notion, pointing out that the "leg wings" on Anchiornis and other close relatives of birds would have made for very clumsy running. These researchers are reviving the old idea that protobirds used feathers to help them leap from trees, glide, and finally fly.
Ground up, trees down—why not both? Flight did not evolve in a two-dimensional world, argues Ken Dial, a flight researcher at the University of Montana-Missoula. Dial has shown that in many species a chick flaps its rudimentary wings to gain traction as it runs from predators up steep inclines, like tree trunks and cliffs. But flapping also helps steady the chick's inevitable return to lower terrain. As the young bird matures, such controlled descent gradually gives way to powered flight. Perhaps, says Dial, the path the chick takes in development retraces the one its lineage followed in evolution—winging it, so to speak, until it finally took wing.


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For women, the experience of menopause can be as individualistic, unique and varied as our fingerprints. Some women sail through it without any major bumps, while others grapple with annoying and unpredictable symptoms for as long as a decade. Any woman who has battled hot flashes, loss of libido, weight gain and mood swings will know what I am talking about.
Menopause is a significant phase in any woman's life, and not only because it signals the end of the reproductive period, but also because it comes at a time when most of us have a demanding life to lead and responsibilities to deal with. Therefore, staying fit and active should be a top priority.
There are several supplements and dietary recommendations that are known to ease the symptoms, but a little known secret is the use of essential oils for menopause.
Which essential oils to use for menopause?
- Some oils like Geranium and Clary Sage support the female reproductive system by balancing hormones and regulating menstrual cycles.
- During menopause, the level of estrogens in the body comes down, leading to physiological and psychological changes. Fennel contains natural plant estrogens that can fill in the void so that these changes feel less dramatic.
- Depression is another side effect of menopause. The fresh citrusy scent of Grapefruit lifts away the depression and dullness, while Cypress helps build inner strength during this period of transition.

subset: commoncrawl


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Message Board
John Stanley Message Board
Talk about the novels, new and used books that Stanley has written!
Author Stanley's Book Reviews
World War III
In a Mainland China, a motley band of allies (including Sarge, a young writer, a Greek chef, a dancer, a pleasure girl, a German former Nazi, and a Nissei old-time radio nut)trapped behind enemy lines with a Chinese prisone eventually find themselves in a fort defending against the Chinese hoerdes. Meanwhile, a squad of trained apes from the US is out for revenge...a very creative work combining pathos with parody, done in a variety of literary styles....


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|Researched by
|Thomas Stamp
|Refereed by
On infralittoral mixed muddy substrata communities characterized by the kelp Saccharina latissima and mixed filamentous and foliose red algae can be found. This biotope contains a number of sub-biotopes distinguished by the degree of either wave or tidal exposure. In moderately strong tidal streams in exposed areas Laminaria is sparse and dense stands of red seaweeds are found attached to the boulders and cobbles that make up a large proportion of the sediment (SlatR.CbPb). As the degree of wave and/or tidal exposure decreases there is a change in community structure, with the density of Laminaria and the diversity of red algal species increasing (SlatR.Gv). As the environment becomes more stable a number of brown algal species are able to inhabit this environment and a rich infauna develops (SlatR.Sa). In the most sheltered examples of this biotope a diverse muddy sediment infauna can be found and the 'Trailliella' phase of Bonnemaisonia hamifera may develop (SlatR.Mu).
SS.SMp.KSwSS.SlatR (plus sub-biotopes) and SS.SMp.KSwSS.SlatCho typically occur on a mixture of shallow sediments and rock fractions. The mobility of the sediment and rock fractions allow Saccharina latissima (syn. Laminaria saccharina), Chorda filum and other red and brown seaweeds to grow on small stones and shells. Saccharina latissima and Chorda filum are important canopy forming species within these biotopes. Four sub-biotopes are present within the SS.SMp.KSwSS.SlatR biotope complex, which are largely distinguished by the degree of tidal flow and wave action. As the degree of wave and/or tidal exposure decreases there is a change in community structure, with the density of Saccharina latissima and the diversity of red algal species increasing. A decrease in tidal flow results in increased sediment stability which in turn facilitates mature macro-algae communities.
In undertaking this assessment of sensitivity, account is taken of knowledge of the biology of all characterizing species in the biotope. For this sensitivity assessment Saccharina latissima, Chorda filum are the primary foci of research, however it is recognized that the red seaweed communities of SS.SMp.KSwSS.SlatR also define these biotopes. Examples of important species groups are mentioned where appropriate.
Saccharina latissima (syn. Laminaria saccharina) and Chorda filum are opportunistic seaweeds which have relatively fast growth rates. Saccharina lattisima is a perennial kelp which can reach maturity in 15-20 months ((Sjøtun, 1993) and has a life expectancy of 2-4 years (Parke, 1948). Chorda filum is an annual seaweed, completing its life cycle in a single season (Novaczek et al., 1986). Saccharina lattisima is widely distributed in the north Atlantic from Svalbard to Portugal (Birket et al., 1998; Connor et al., 2004; Bekby & Moy 2011; Moy & Christie 2012). Chorda filum is widely distributed across the northern hemisphere (Algae Base, 2015). In the North Atlantic, Chorda filum is recorded from Svalbard (Fredriksen et al., 2014) to Northern Portugal (Araújo et al, 2009).
Saccharina lattisma and Chorda filum have heteromorphic life strategies (Edwards, 1998). Mature sporophytes broadcast spawn zoospores from reproductive structures known as sori (South & Burrows, 1967; Birket et al., 1998). Zoospores settle onto rock and develop into gametophytes, which following fertilization germinate into juvenile sporophytes. Laminarian zoospores are expected to have a large dispersal range. However, zoospore density and the rate of successful fertilization decreases exponentially with distance from the parental source (Fredriksen et al., 1995). Hence, recruitment can be influenced by the proximity of mature kelp beds producing viable zoospores (Kain, 1979; Fredriksen et al., 1995). Saccharina lattisma recruits appear in late winter early spring beyond which is a period of rapid growth, during which sporophytes can reach a total length of 3 m (Werner & Kraan, 2004). In late summer and autumn growth rates slow and spores are released from autumn to winter (Parke, 1948; Lüning, 1979; Birket et al., 1998). The overall length of the sporophyte may not change during the growing season due to marginal erosion but growth of the blade has been measured at 1.1 cm/day, with a total length addition of ≥2.25 m per year (Birkett et al., 1998). Chorda filum recruits appear from February (South & Burrows, 1967) after which is a period of rapid growth during which sporophytes can reach a length of ≤6 m (South & Burrows, 1967). In culture, Chorda filum can reach reproductive maturity and produce zoospores within 186 days (ca 6 months) of settlement but the time taken to reach maturity may be locally variable (South & Burrows, 1967). In nature, sporophytes growth slows/stops from October and sporophytes may begin to die off (South & Burrows, 1967; Novaczek et al., 1986).
Saccharina lattisma can be quite ephemeral in nature and appear early in algal succession. For example, Leinaas & Christie (1996) removed Strongylocentrotus droebachiensis from "Urchin Barrens" and observed a succession effect. Initially the substratum was colonized by filamentous algae, after a couple of weeks these were out-competed and the habitat dominated by Saccharina latissimi. However, this was subsequently out-competed by Laminaria hyperborea. In the Isle of Man, Kain (1975) cleared sublittoral blocks of Laminaria hyperborea at different times of the year for several years. The first colonizers and succession community differed between blocks and at what time of year the blocks were cleared. Saccharina lattisma was an early colonizer, but within 2 years of clearance, the blocks were dominated by Laminaria hyperborea.
In 2002, a 50.7-83% decline of Saccharina latissima was discovered in the Skaggerak region, South Norway (Moy et al., 2006; Moy & Christie, 2012). Survey results indicated a sustained shift from Saccharina latissima communities to those of ephemeral filamentous algal communities. The reason for the community shift was unknown, but low water movement in wave and tidally sheltered areas combined with the impacts of dense human populations, e.g. increased land run-off, was suggested to be responsible for the dominance of ephemeral turf macro-algae. Multiple stressors such as eutrophication, increasing regional temperature, increased siltation and overfishing may also be acting synergistically to cause the observed habitat shift.
Resilience assessment. Saccharina latissima, Chorda filum have the potential to rapidly recover following disturbance. Saccharina latissima has been shown to be an early colonizer within algal succession, appearing within 2 weeks of clearance, and can reach sexual maturity within 15-20 months. Chorda filum has rapid growth rates, capable of reaching sexual maturity within a year. Resilience has therefore been assessed as 'High'.
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The temperature isotherm of 19-20°C has been reported as limiting Saccharina latissima geographic distribution (Müller et al., 2009). Gametophytes can develop in ≤23°C (Lüning, 1990) however the optimal temperature range for sporophyte growth is 10-15 °C (Bolton & Lüning, 1982). Bolton & Lüning (1982) experimentally observed that sporophyte growth was inhibited by 50-70% at 20 °C and following 7 days at 23 °C all specimens completely disintegrated. In the field Saccharina latissima has shown significant regional variation in its acclimation to temperature changes, for example Gerard & Dubois (1988) observed sporophytes of Saccharina latissima which were regularly exposed to ≥20 °C could tolerate these temperatures, whereas sporophytes from other populations which rarely experience ≥17 °C showed 100% mortality after 3 weeks of exposure to 20 °C. Therefore the response of Saccharina latissima to a change in temperatures is likely to be locally variable.
In experiments, Lüning (1980) observed that Chorda filum could not reproduce at 15-20 °C but found that sporophytes could tolerate ≤26 °C.
Northern to southern Sea Surface Temperature (SST) ranges from 8-16 °C in summer and 6-13 °C in winter in the UK (Beszczynska-Möller & Dye, 2013). The effect of this pressure is likely to be regionally variable.
Sensitivity assessment. Ecotypes of Saccharina lattisma have been shown to have different temperature optimums (Dubois, 1988). Both a 2 & 5 °C increase in temperature when combined with high UK summer temperatures in the south of the UK could cause large scale mortality of Saccharina lattisma and inhibit Chorda filum reproduction. Resistance has been assessed as 'None', Resilience as 'High'. Sensitivity has been assessed as 'Medium'.
|Not sensitive
Saccharina lattissima and Chorda filum are widespread throughout the arctic. Saccharina lattissima has a lower temperature threshold for sporophyte growth at 0°C (Lüning, 1990). Chorda filum sporophytes can also tolerate 0 °C, Novaczek et al., (1986) observed that 99% of newly settled zoospores died at 0 °C but sporophytes transferred from 5°C to 0°C remained healthy and continued to grow for a period of 2 months. Novaczek et al., (1986) therefore demonstrated that sporophytes could tolerate exposure to low (≥0°C) temperatures, but that exposure could have negative effects on larval survival and recruitment processes. Subtidal red algae can survive at -2°C (Lüning, 1990; Kain & Norton, 1990). The distribution and temperature tolerances of these species suggests they likely be unaffected by temperature decreases assessed within this pressure.
Sensitivity assessment. Resistance has been assessed as 'High', resilience as 'High'". Sensitivity has been assessed as 'Not Sensitive'.
Karsten (2007) tested the photosynthetic ability of Saccharina latissima under acute 2 and 5 day exposure to salinity treatments ranging from 5-60 psu. A control experiment was also carried at 34 psu. Saccharina latissima showed high photosynthetic ability at >80% of the control levels between 25-55 psu. However, Birkett et al. (1998) suggested that kelps are stenohaline and therefore long-term increases in salinity may be detrimental.
Chorda filum can be found in rock pools (South & Burrows, 1967). High air temperatures cause surface evaporation of water from rock pools, so that salinity steadily increases. The extent of temperature and salinity change is affected by the frequency and time of day at which tidal inundation occurs. If high tide occurs in early morning and evening the diurnal temperature follows that of the air, whilst high water at midday suddenly returns the temperature to that of the sea (Pyefinch, 1943). It should be noted however that local populations may be acclimated to the prevailing salinity regime and may therefore exhibit different tolerances to other populations subject to different salinity conditions and therefore caution should be used when inferring tolerances. However, it is likely that Chorda filum is tolerant of short-term salinity increases.
Sensitivity assessment. The evidence suggests that Saccharina latissima and Chorda filum can tolerate short-term exposure to hypersaline conditions (≥40‰-MNCR full salinity). An increase in salinity to ≥40‰ may however be above the optima for characterizing species and cause a decline in growth, and possibly loss of red algae and a reduction in species diversity. Resistance has been assessed as 'Medium', resilience as 'High'. The sensitivity of this biotope to an increase in salinity has been assessed as 'Low'.
Karsten (2007) tested the photosynthetic ability of Saccharina latissima under acute 2 and 5 day exposure to salinity treatments ranging from 5-60 psu. A control experiment was also carried at 34 psu. Saccharina latissima showed high photosynthetic ability at >80% of the control levels between 25-55 psu. Hyposaline treatment of 10-20 psu led to a gradual decline of photosynthetic ability. After 2 days at 5 psu Saccharina latissima showed a significant decline in photosynthetic ability at approx. 30% of control. After 5 days at 5 psu Saccharina latissima specimens became bleached and showed signs of severe damage. The experiment was conducted on Saccharina latissima from the Arctic, and the authors suggest that at extremely low water temperatures (1-5°C) macroalgae acclimation to rapid salinity changes could be slower than at temperate latitudes. It is therefore possible that resident Saccharina latissima of the UK maybe be able to acclimate to salinity changes more effectively.
Chorda filum is tolerant of low salinities (Wilce, 1959; Hayren, I940; Norton & South, 1969), and has been recorded at Björnholm, Finland at a salinity as low as 5.15%o (Hayren, I940). Norton & South (1969) observed that Chorda filum could develop sporophytes at ≥5%o under laboratory conditions, however at low salinities the time taken to develop into sporophytes took 65 days at 5%o, or 16 days at 35%o. It was also noted that below 9%o sporophytes did not grow above 2 mm in length.
Sensitivity assessment. A decrease in one MNCR salinity scale from "Full Salinity" (30-40psu) to "Reduced Salinity" (18-30 psu) would inhibit Saccharina lattissima photosynthesis and hence growth. Chorda filum is highly tolerant of low salinity and is unlikely to be affected at the bench mark level. However, a shift to reduced salinity conditions is likely to result in a change in the infauna community and an overall reduction in species diversity. Therefore, resistance has been assessed as 'Medium' resilience as 'High'. Sensitivity of this biotope to a decrease in salinity has been assessed as 'Low'.
|Not sensitive
Peteiro & Freire (2013) measured Saccharina latissima growth from 2 sites, the 1st had maximal water velocities of 0.3 m/sec and the 2nd 0.1 m/sec. At site 1 Saccharina latissima had significantly larger biomass than at site 2 (16 kg/m to 12 kg/m respectively). Peteiro & Freire (2013) suggested that faster water velocities were beneficial to Saccharina latissima growth. However, Gerard & Mann (1979) measured Saccharina latissima productivity at greater water velocities and found Saccharina latissima productivity is reduced in moderately strong tidal streams (≤1 m/sec) when compared to weak tidal streams (<0.5 m/sec).
Chorda filum sporophytes often grow on unstable objects, such as pebbles and shell. Owing to the typically unstable substratum which Chorda filum grows on, whole populations can be moved during storms and deposited in more sheltered locations where development will continue (South & Burrows, 1967). The survival of Chorda filum sporophytes following transport of their attached substrata indicates the species is relatively tolerant to changes in water flow or wave action.
As highlighted by Connor et al., (2004) large increases in tidal flow (>0.5 m/s) are likely to influence biotope structure and smaller changes in tidal flow (e.g. 0.1-0.2m/s) are not likely to have a significant effect on the characterizing species. A change in tidal flow of 0.1-0.2 m/sec in low energy biotopes e.g. SS.SMp.KSwSS.SlatR.Mu, may however remove finer sediment fractions (e.g. mud) and may therefore change the biotope. However, evidence is lacking and a change in tidal velocities is not likely to result in a significant change to the dominant species.
Sensitivity assessment. Resistance has been assessed as 'High', resilience as 'High'. Sensitivity has been assessed as 'Not Sensitive'.
SS.SMp.KSwSS.SlatR and SS.SMp.KSwSS.SlatCho are recorded from 0-10m, while SlatR can extend to 20m (Connor et al., 2004). Therefore the upper limit of the biotopes in the sub-littoral fringe (South & Burrows, 1967; White & Marshall, 2007) could be exposed during some low tides.
An increase in emergence will result in an increased risk of desiccation and mortality of Saccharina latissima and Chorda filum. Removal of macroalgae canopy may also increase desiccation and mortality of the undergrowth red seaweed community (Hawkins & Harkin, 1985). Providing that suitable substrata are present, the biotope is likely to re-establish further down the shore within a similar emergence regime to that which existed previously.
Sensitivity assessment. Resistance has been assessed as 'Medium'. Resilience as 'High'. The sensitivity of this biotope to a change in emergence is considered as 'Low'.
|Not sensitive
Birkett et al., (1998) suggested that Saccharina latissima is rarely present in areas of wave exposure, where it is out-competed by Laminaria hyperborea. Chorda filum sporophytes often grow on unstable objects, such as pebbles and shell. Owing to the typically unstable substratum which Chorda filum grows on, whole populations can be moved during storms and deposited in more sheltered locations where development will continue (South & Burrows, 1967).
A large increase in near-shore wave height is likely to significantly influence biotope structure. As highlighted by Connor et al., (2004) sub-biotopes within SS.SMp.KSwSS.SlatR are largely distinguished by wave exposure
Sensitivity assessment. A large scale increase in local wave height may increase local sediment mobility, potentially increase dislodgment or relocation of the characterizing species (South & Burrows, 1967; Birkett et al., 1998b). However, an increase in nearshore significant wave height of 3-5% is not likely to have a significant effect on biotope structure. Resistance has been assessed as 'High', Resilience as 'High'. Sensitivity has been assessed as 'Not Sensitive' at the benchmark level.
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|Not Assessed (NA)
|Not assessed (NA)
|Not assessed (NA)
This pressure is Not assessed but evidence is presented where available
Bryan (1984) suggested that the general order for heavy metal toxicity in seaweeds is: Organic Hg > inorganic Hg > Cu > Ag > Zn > Cd > Pb. Cole et al., (1999) reported that Hg was very toxic to macrophytes. Similarly, Hopkin & Kain (1978) demonstrated sub-lethal effects of heavy metals on kelp gametophytes and sporophytes, including reduced growth and respiration. Sheppard et al. (1980) noted that increasing levels of heavy metal contamination along the west coast of Britain reduced species number and richness in holdfast fauna, except for suspension feeders which became increasingly dominant. Gastropods may be relatively tolerant of heavy metal pollution (Bryan, 1984). Although macroalgae species may not be killed, except by high levels of contamination, reduced growth rates may impair the ability of the biotope to recover from other environmental disturbances. Thompson & Burrows (1984) observed the growth of Saccharina latissima sporophyte growth was significantly inhibited at 50 µg Cu /l, 1000 µg Zn/l and 50 µg Hg/l. Zoospores were found to be more intolerant and significant reductions in survival rates were observed at 25 µg Cu/l, 1000 µg Zn/l and 5 µg/l.
|Not Assessed (NA)
|Not assessed (NA)
|Not assessed (NA)
This pressure is Not assessed but evidence is presented where available
The mucilaginous slime layer coating of Laminarians may protect them from smothering by oil. Hydrocarbons in solution reduce photosynthesis and may be algicidal. However, Holt et al. (1995) reported that oil spills in the USA and from the 'Torrey Canyon' had little effect on kelps. Similarly, surveys of subtidal communities at a number sites between 1-22.5m below chart datum showed no noticeable impacts of the Sea Empress oil spill and clean up (Rostron & Bunker, 1997) or during experimental release of untreated oil in Baffin Island, Canada (Cross et al., 1987). Laboratory studies of the effects of oil and dispersants on several red algae species (Grandy 1984) concluded that they were all sensitive to oil/ dispersant mixtures, with little differences between adults, sporelings, diploid or haploid life stages.
|Not Assessed (NA)
|Not assessed (NA)
|Not assessed (NA)
This pressure is Not assessed but evidence is presented where available
O'Brian & Dixon (1976) suggested that red algae were the most sensitive group of macrophytes to oil and dispersant contamination (see Smith, 1968). Saccharina latissima has also been found to be sensitive to antifouling compounds. Johansson (2009) exposed samples of Saccharina latissima to several antifouing compounds, observing chlorothalonil, DCOIT, dichlofluanid and tolylfluanid inhibited photosynthesis. Exposure to Chlorothalonil and tolylfluanid, was also found to continue inhibiting oxygen evolution after exposure had finished, and may cause irreversible damage.
Smith (1968) observed that epiphytic and benthic red algae were intolerant of dispersant or oil contamination during the Torrey Canyon oil spill; only the epiphytes Crytopleura ramosa and Spermothamnion repens and some tufts of Jania rubens survived together with Osmundea pinnatifida, Gigartina pistillata and Phyllophora crispa from the sublittoral fringe.
|Not relevant (NR)
|Not relevant (NR)
|No evidence (NEv)
No evidence
|Not Assessed (NA)
|Not assessed (NA)
|Not assessed (NA)
This pressure is Not assessed.
|Not sensitive
Reduced oxygen concentrations can inhibit both photosynthesis and respiration in macroalgae (Kinne, 1977). Despite this, macroalgae are thought to buffer the environmental conditions of low oxygen, thereby acting as a refuge for organisms in oxygen depleted regions especially if the oxygen depletion is short-term (Frieder et al., 2012). Rapid recovery from a state of low oxygen is expected if the environmental conditions are transient. If levels do drop below 4 mg/l negative effects on these organisms can be expected with adverse effects occurring below 2mg/l (Cole et al., 1999).
Sensitivity Assessment. Reduced oxygen levels are likely to inhibit photosynthesis and respiration but not cause a loss of the macroalgae population directly. Resistance has been assessed as 'High', Resilience as 'High'. Sensitivity has been assessed as 'Not sensitive' at the benchmark level.
|Not relevant (NR)
|Not relevant (NR)
|Not sensitive
Conolly & Drew (1985) found Saccharina latissima sporophytes had relatively higher growth rates when in close proximity to a sewage outlet in St Andrews, UK, compared to other sites along the east coast of Scotland. At St Andrews nitrate levels were 20.22µM, which represents an approx. 25% increase compared to other sites (approx. 15.87 µM). Handå et al. (2013) also reported Saccharina latissima sporophytes grew approx. 1% faster per day when in close proximity to Norwegian salmon farms, where elevated ammonium could be readily absorbed by sporophytes. Read et al. (1983) reported after the installation of a new sewage treatment works, which reduced the suspended solid content of liquid effluent by 60% in the Firth of Forth, Saccharina latissima became abundant where previously it had been absent. Bokn et al. (2003) conducted a nutrient loading experiment on intertidal fucoids. Within 3 years of the experiment no significant effect was observed in the communities, however 4-5 years into the experiment a shift occurred from perennials to ephemeral algae. Although Bokn et al. (2003) focussed on fucoids the results could indicate that long-term (>4 years) nutrient loading can result in community shift to ephemeral algae species. Disparities between the findings of the aforementioned studies are likely to be related to the level of organic enrichment.
Johnston & Roberts (2009) conducted a meta-analysis, which reviewed 216 papers to assess how a variety of contaminants (including sewage and nutrient loading) affected 6 marine habitats (including subtidal reefs). A 30-50% reduction in species diversity and richness was identified from all habitats exposed to the contaminant types. Johnston & Roberts (2009) however also highlighted that macroalgal communities are relative tolerant to contamination, but that contaminated communities can have low diversity assemblages which are dominated by opportunistic and fast growing species (Johnston & Roberts, 2009 and references therein).
Sensitivity assessment. Although short-term exposure (<4 years) to nutrient enrichment may not affect seaweeds directly, indirect effects such as turbidity may significantly affect photosynthesis and result in reduced growth and reproduction and increased competition form fast growing but ephemeral species. However, this biotope is considered to be 'Not sensitive' at the pressure benchmark, that assumes compliance with good status as defined by the WFD.
A: Medium
Read et al. (1983) reported after the installation of a new sewage treatment works, which reduced the suspended solid content of liquid effluent by 60% in the Firth of Forth, Saccharina latissima became abundant where previously it had been absent. Bokn et al. (2003) conducted a nutrient loading experiment on intertidal fucoids. Within 3 years of the experiment no significant effect was observed in the communities, however 4-5 years into the experiment a shift occurred from perennials to ephemeral algae. Although Bokn et al. (2003) focussed on fucoids the results could indicate that long-term (>4 years) nutrient loading can result in community shift to ephemeral algae species. Disparities between the findings of the aforementioned studies are likely to be related to the level of organic enrichment.
Johnston & Roberts (2009) conducted a meta-analysis, which reviewed 216 papers to assess how a variety of contaminants (including sewage and nutrient loading) affected 6 marine habitats (including subtidal reefs). A 30-50% reduction in species diversity and richness was identified from all habitats exposed to the contaminant types. Johnston & Roberts (2009) however also highlighted that macroalgal communities are relatively tolerant to contamination, but that contaminated communities can have low diversity assemblages which are dominated by opportunistic and fast growing species (Johnston & Roberts, 2009 and references therein). Organic enrichment may also result in phytoplankton blooms that increase turbidity and therefore may negatively impact photosynthesis.
Sensitivity assessment. Although short-term exposure (<4 years) to organic enrichment may not affect seaweeds directly, indirect effects such as turbidity may significantly affect photosynthesis, and result in reduced growth and reproduction and increased competition form fast growing but ephemeral species Resistance has been assessed as 'Medium', resilience as 'High'. Sensitivity has been assessed as 'Low'.
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|Very Low
All marine habitats and benthic species are considered to have a resistance of 'None' to this pressure and to be unable to recover from a permanent loss of habitat (resilience is 'Very Low'). Sensitivity within the direct spatial footprint of this pressure is therefore 'High'. Although no specific evidence is described confidence in this assessment is 'High', due to the incontrovertible nature of this pressure.
|Very Low
If sediment were replaced with rock or artificial substrata, this would represent a fundamental change to the biotope (Macleod et al., 2014). All the characterizing species within this biotope can grow on rock biotopes (Birkett et al., 1998; Connor et al., 2004), however SS.SMp.KSwSS are by definition sediment biotopes and introduction of rock would change them into a rock based habitat complex, and the biotope would be lost
Sensitivity assessment. Resistance to the pressure is considered 'None', and resilience 'Very low'. Sensitivity has been assessed as 'High'
|Very Low
SS.SMp.KSwSS are sediment based biotopes. Stabilised cobbles, pebbles, gravel and shell fractions provide a substrate for macro-algae to dominate the community (Connor et al., 2004). An increase in the dominance of smaller sediment fractions e.g. sand and/or mud will likely smoother the existing biotope, inhibit successive re-colonisation of macro-algae and/or increase the sediment scour.
Sensitivity assessment. Resistance has been assessed as 'None', resilience as Very low (the pressure is a permanent change), and sensitivity as High.
SS.SMp.KSwSS.SlatR (plus sub-biotopes), SS.SMp.KSwSS.SlatCho can be found on a varied mixture of sediment and rock fractions. Extraction of substratum to 30 cm is likely to remove small sediment fractions (e.g. gravel) and may mobilize the remaining larger rock fractions (e.g. boulders) causing high mortality within the resident community. All characterizing species have rapid growth rates and are likely to recover within 2 years.
Sensitivity assessment. Resistance has been assessed as 'None', Resilience as 'High'. Sensitivity has been assessed as 'Medium'.
Abrasion of the substratum e.g. from bottom or pot fishing gear, cable laying etc. may cause localised mobility of the substrata and mortality of the resident community. The effect would be situation dependent, however, if bottom fishing gear were towed over a site it may mobilise a high proportion of the rock substrata and cause high mortality in the resident community.
Sensitivity assessment. Resistance has been assessed as 'None', Resilience as 'High'. Sensitivity has been assessed as 'Medium'.
Penetration and/or disturbance of the substrate below the surface of the seabed, may cause localised mobility of the substrata and mortality of the resident community.
Sensitivity assessment. Resistance has been assessed as 'None', Resilience as 'High'. Sensitivity has been assessed as 'Medium'.
Suspended Particle Matter (SPM) concentration has a positive linear relationship with sub surface light attenuation (Kd) (Devlin et al., 2008). Light availability and water turbidity are principal factors in determining depth range at which macro-algae can be found (Birkett et al., 1998b). Light penetration influences the maximum depth at which laminarians can grow and it has been reported that laminarians grow at depths at which the light levels are reduced to 1 percent of incident light at the surface. Maximal depth distribution of laminarians therefore varies from 100 m in the Mediterranean to only 6-7m in the silt laden German Bight. In Atlantic European waters, the depth limit is typically 35 m. In very turbid waters the depth at which kelp is found may be reduced, or in some cases excluded completely (e.g. Severn Estuary), because of the alteration in light attenuation by suspended sediment (Lüning, 1990; Birkett et al. 1998b). Laminarians show a decrease of 50% photosynthetic activity when turbidity increases by 0.1/m (light attenuation coefficient =0.1-0.2/m; Staehr & Wernberg, 2009).
Sensitivity Assessment. A decrease in turbidity is likely to support enhanced growth (and possible habitat expansion) and is therefore not considered in this assessment. An increase in water turbidity is likely to primarily affect photosynthesis therefore growth and density of the canopy forming seaweeds. Resistance to this pressure is defined as 'Low' and resilience to this pressure is defined as 'High' at the benchmark level due to the scale of the impact. Hence, this biotope is regarded as having a sensitivity of 'Low'.
|Not sensitive
Smothering by sediment e.g. 5 cm material during a discrete event, is unlikely to damage mature examples of Saccharina latissima and Chorda filum but may provide a physical barrier to zoospore settlement and therefore could negatively impact on recruitment processes (Moy & Christie, 2012). Laboratory studies showed that kelp and gametophytes can survive in darkness for between 6-16 months at 8 °C and would probably survive smothering by a discrete event and once returned to normal conditions gametophytes resumed growth or maturation within 1 month (Dieck, 1993).
SS.SMp.KSwSS biotopes are all recorded in moderately strong tidal streams to negligible (≤1.5 m/sec) (Connor et al., 2004). In tidally exposed biotopes deposited sediment is unlikely to remain for more than a few tidal cycles (due to water flow or wave action). In sheltered biotopes deposited sediment could remain however are unlikely to remain for longer than a year.
Sensitivity assessment. Resistance has been assessed as 'High', resilience as 'High'. Sensitivity has been assessed as 'Not Sensitive'.
Smothering by sediment e.g. 30 cm material during a discrete event, is unlikely to damage mature examples of Saccharina latissima and Chorda filum but may provide a physical barrier to zoospore settlement and therefore could negatively impact on recruitment processes (Moy & Christie, 2012). Laboratory studies showed that kelp and gametophytes can survive in darkness for between 6-16 months at 8°C and would probably survive smothering by a discrete event and once returned to normal conditions gametophytes resumed growth or maturation within 1 month (Dieck, 1993).
SS.SMp.KSwSS biotopes are all recorded in moderately strong tidal streams to negligible (≤1.5 m/sec) (Connor et al., 2004). In tidally exposed biotopes deposited sediment is unlikely to remain for more than a few tidal cycles (due to water flow or wave action). In sheltered biotopes deposited sediment could remain however are unlikely to remain for longer than a year.
Sensitivity assessment. Resistance has been assessed as 'Medium', resilience as 'High'. Sensitivity has been assessed as 'Low'.
|Not Assessed (NA)
|Not assessed (NA)
|Not assessed (NA)
Not assessed. There is no evidence to suggest that litter would affect kelp.
|Not relevant (NR)
|Not relevant (NR)
|No evidence (NEv)
No evidence
|Not relevant (NR)
|Not relevant (NR)
|Not relevant (NR)
Not relevant
There is no evidence to suggest that anthropogenic light sources would affect macro-algae. Shading of the biotope (e.g. by construction of a pontoon, pier etc.) could adversely affect the biotope in areas where the water clarity is also low, and tip the balance to shade tolerant species, resulting in the loss of the biotope directly within the shaded area, or a reduction in seaweed abundance.
Sensitivity assessment. Resistance is probably 'Low', with a 'Medium' resilience and a sensitivity of 'Medium', albeit with 'low' confidence due to the lack of direct evidence.
|Not relevant (NR)
|Not relevant (NR)
|Not relevant (NR)
Not relevant. This pressure is considered applicable to mobile species, e.g. fish and marine mammals rather than seabed habitats. Physical and hydrographic barriers may limit the dispersal of spores. But spore dispersal is not considered under the pressure definition and benchmark.
|Not relevant (NR)
|Not relevant (NR)
|Not relevant (NR)
Not relevant. Collision from grounding vessels is addressed under abrasion above.
|Not relevant (NR)
|Not relevant (NR)
|Not relevant (NR)
Not relevant
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|Not relevant (NR)
|Not relevant (NR)
|No evidence (NEv)
At the time of writing there is no evidence for translocation of Saccharina latissima, Chorda filum over significant geographic distances.
|Very Low
Undaria pinnatifida has received a large amount of research attention as a major Invasive Non Indigenous Species (INIS) which could out-compete native UK kelp habitats (see Farrell & Fletcher, 2006; Thompson & Schiel, 2012, Brodie et al., 2014; Hieser et al., 2014). Undaria pinnatifida was first recorded in the UK, Hamble Estuary, in June 1994 (Fletcher & Manfredi, 1995) and has since spread to a number of British ports. Undaria pinnatifida is an annual species, sporophytes appear in Autumn and grow rapidly throughout winter and spring during which they can reach a length of 1.65m (Birket et al., 1998). Farrell & Fletcher (2006) suggested that native short lived species that occupy similar ecological niches to Undaria pinnatifida, such as Saccharina latissima or Chorda filum, are likely to be worst affected and out-competed by Undaria pinnatifida. Where present an abundance of Undaria pinnatifida has corresponded to a decline in Saccharina lattisima (Farrel & Fletcher, 2006) and Laminaria hyperborea (Hieser et al., 2014).
In New Zealand, Thompson & Schiel (2012) observed that native fucoids could out-compete Undaria pinnatifida and re-dominate the substratum. However, Thompson & Schiel (2012) suggested the fucoid recovery was partially due to an annual Undaria pinnatifida die back, which as noted by Heiser et al., (2014) does not occur in Plymouth sound, UK. Undaria pinnatifida was successfully eradicated on a sunken ship in Clatham Islands, New Zealand, by applying a heat treatment of 70 °C (Wotton et al., 2004) however numerous other eradication attempts have failed, and as noted by Fletcher & Farrell, (1999) once established Undaria pinnatifida resists most attempts of long-term removal. The biotope is unlikely to fully recover until Undaria pinnatifida is fully removed from the habitat, which as stated above is unlikely to occur.
Sensitivity assessment. Resistance to the pressure is considered 'Low', and resilience 'Very low'. The sensitivity of this biotope to introduction of microbial pathogens is assessed as 'High'.
Laminarians may be infected by the microscopic brown alga Streblonema aecidioides. Infected algae show symptoms of Streblonema disease, i.e. alterations of the blade and stipe ranging from dark spots to heavy deformations and completely crippled thalli Infection can reduce growth rates of host algae (Peters & Scaffelke, 1996). The marine fungi Eurychasma spp can also infect early life stages of Laminarians however the effects of infection are unknown (Müller et al., 1999).
Sensitivity assessment. Resistance to the pressure is considered 'Low', and resilience 'High'. The sensitivity of this biotope to introduction of microbial pathogens is assessed as 'Low'.
|Not relevant (NR)
|Not relevant (NR)
|Not relevant (NR)
This pressure has been assessed as 'Not relevant'.
There has been recent commercial interest in Saccharina lattisma as a consumable called "sea vegetables" (Birket et al., 1998). However, Saccharina lattissima sporophytes are typically matured on ropes (Handå et al 2013) and not directly extracted from the seabed, as with Laminaria hyperborea (Christie et al., 1998). No evidence has been found for commercial extraction of Chorda filum.
Low level disturbances (e.g. solitary anchors) are unlikely to cause harm to the biotope as a whole, due to the impact's small footprint. Thus evidence to assess the resistance of SS.SMp.KSwSS.SlatR (plus sub-biotopes), SS.SMp.KSwSS.SlatCho to non-targeted removal is limited. It is assumed that incidental non-targeted catch (e.g. by trawls or dredges) could mobilise sediment, remove large kelp species, overturn boulders and cobbles and bury smaller seaweeds and cause high mortality within the affected area.
Sensitivity assessment. Resistance has been assessed as 'None', Resilience as 'High'. Sensitivity has been assessed as 'Medium'.
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Last Updated: 05/10/2015