I***i
发帖数: 14557 | 1 http://www.foxnews.com/science/2013/01/02/gelatinous-menace-jel
Gelatinous menace? Jellyfish on boom-bust cycle worldwide
Though some reports suggest jellyfish are taking over the world’s oceans,
long-term records of these gelatinous animals fail to show a global increase
in jellyfish blooms likely caused by pollution, warming, coastal
development and other human influences.
While the analysis of a team of researchers who have pulled together records
of jellyfish presence going back to the 19th century don't support a rising
gelatinous menace, the team did find a surprise: roughly 20-year cycles in
the abundanceof jellies.
Part of a recent rise-and-fall cycle may have prompted the perception of a
global swell in jellyfish, according to the international team, whose
researchers are part of the Global Jellyfish Group. They point specifically
to the rising phase that began in 1993 and peaked in 2004.
Blamed for stinging swimmers, clogging fishing nets, overrunning ecosystems
and wreaking other havoc, jellyfish blooms — when these animals appear in
massive numbers — have caught the attention of the media and scientists
alike. A number of research papers have suggested that not only are blooms
increasing on a global scale, but humans are likely responsible, because
humans alter the oceans in ways that favor jellyfish. [See Stunning Photos
of Jellyfish Blooms]
http://www.livescience.com/13921-jellyfish-swarms-amazing-image
However, others have maintained information on jellyfish populations just
isn't sufficient to draw such conclusions.
This most recent study drew upon 37 datasets, each of which included at
least 10 years of records of jellyfish presence in an area.
Even though the records don't evenly represent the ocean — the majority
came from the Northern Hemisphere, particularly in the Atlantic Ocean and
the Mediterranean Sea — they include all available annual measurements,
including datasets used to support work indicating increases in jellyfish,
the authors write in a study published online today (Dec. 31) in the journal
Proceedings of the National Academy of Sciences.
Language has added to the challenge. In common use, the term jellyfish lumps
together organisms that can be quite different from one another. For the
purposes of this study, the researchers included records for true jellies,
the type most familiar to beachgoers; their relatives the hydrozoans; comb
jellies, which use tiny hairs, called cilia, to swim; and another group of
free-swimming invertebrates called salps.
From around 1940 to present, the records show the 20-year rising and falling
cycles. Prior to that, researchers saw signs of oscillations in regions
where data were available; however, this isn't enough information to draw
conclusions about global patterns, said lead researcher Rob Condon, a marine
scientist at Dauphin Island Sea Laboratory in Alabama.
Multidecadal cycles are not uncommon in nature, whether in organisms' growth
patterns and populations, or physical phenomena, such as the oxygen
concentration of the oceans.
While the jellyfish's 20-year cycle most likely has a basis in nature, "
there's also the issue of how humans have potentially impacted the sort of
natural variability that is present in many marine systems," Condon said. "
And I think that is the wider part of the question that can't be answered
yet."
From 1970 onward, a weak trend toward increasing jellyfish showed up.
However, this trend may be an artifact of the 20-year cycles, the authors
write.
Scientists need at least 10 more years of jellyfish records to reach any
solid conclusions about the worldwide trajectory of jellyfish populations,
Condon said, adding that more data from the Southern Hemisphere and the open
ocean are also needed.
The current analysis doesn't rule out the possibility of a global increase,
he told LiveScience, adding that increases are most likely isolated to
certain regions.
One region stood out in their analysis: the Sea of Japan. Here, records
going back to the 1920s of the giant Nomura jellies — which grow up to 6.7
feet in diameter, and have been known to clog fishing nets and power-plant
intakes — showed an increased tendency in recent years toward extremely
high numbers.
Copyright 2012 LiveScience, a TechMediaNetwork company. All rights reserved.
This material may not be published, broadcast, rewritten or redistributed. | a***a
发帖数: 12425 | | e****o
发帖数: 3844 | 3 习惯性的看了图片后有一个问题，这是能吃的海蜇吗
increase
records
rising
in
【在 I***i 的大作中提到】
: http://www.foxnews.com/science/2013/01/02/gelatinous-menace-jel
: Gelatinous menace? Jellyfish on boom-bust cycle worldwide
: Though some reports suggest jellyfish are taking over the world’s oceans,
: long-term records of these gelatinous animals fail to show a global increase
: in jellyfish blooms likely caused by pollution, warming, coastal
: development and other human influences.
: While the analysis of a team of researchers who have pulled together records
: of jellyfish presence going back to the 19th century don't support a rising
: gelatinous menace, the team did find a surprise: roughly 20-year cycles in
: the abundanceof jellies.
| I***i
发帖数: 14557 | 4 我也没读全，看到中间就点那个图片集锦了
【在 a***a 的大作中提到】
: 习惯性地只看了图片和第一自然段，呵呵
| I***i
发帖数: 14557 | 5 刚看了另一个帖子（image gallery）这个是Mastigias jellyfish，别的我啥也不知道
了。
【在 e****o 的大作中提到】
: 习惯性的看了图片后有一个问题，这是能吃的海蜇吗
:
: increase
: records
: rising
: in
| B**o
发帖数: 401 | |
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