为什么南加州的潮汐是蓝色的

为什么南加州的潮汐是蓝色的

During the lockdowns, there aren't as many visitors to the beaches in Southern California. But those who venture out at night have been greeted by a bizarre and beautiful sight: the ocean waters emitting a bright blue glow as the waves crashed and the tide came in.

在封锁期间，前往南加州海滩的游客并没有那么多。但是，那些在夜晚冒险外出的人却看到了一幅奇异而美丽的景象:海浪撞击，潮水涌来时，海水发出明亮的蓝光。

In a rare occurrence, a tiny organism called Lingulodinium polyedrum causes the tides to look red during the day and glow blue at night. (Photo: Mike [CC BY-SA 2.0]/Flickr)

The cause of this unusual phenomenon is a tiny organism called Lingulodinium polyedrum. This dinoflagellate (a type of algae) blooms every few years in the waters around San Diego, forming what is known as a red tide.

这种不寻常现象的原因是一种叫做扁舌藻的微生物。这种鞭毛藻(一种藻类)每隔几年就会在圣地亚哥附近的水域繁殖一次，形成所谓的红潮。

While the algae gives the water a soupy red color during the day, nighttime is when the show begins. Every time the algae is jostled — either by the movement of the tides or the slice of a kayak moving through the water — it emits a bright blue bioluminescent glow. The glow is the result of chemicals made inside the algae's body when it is startled. Biologist Rebecca Helm recently described this response on Twitter as “luminous little panic attacks.”

当藻类在白天给水赋予一种浑浊的红色时，夜晚是表演开始的时候。每次海藻被推挤的时候——无论是潮汐的移动还是皮艇在水中移动的碎片——它都会发出明亮的蓝色生物荧光。这种发光是海藻受到惊吓时体内产生的化学物质的结果。生物学家丽贝卡·赫尔姆最近在推特上把这种反应描述为“明亮的小恐慌发作”。

The breathtaking effect appeared earlier this week, and scientists aren't sure how long it will linger, according to the Scripps Institution of Oceanography.

据斯克里普斯海洋学研究所称，这一惊人的效果于本周早些时候出现，科学家们还不确定它会持续多长时间。

The blooms used to appear every three to seven years, according to Scripps, but they've become much more frequent over the past decade.

据斯克里普斯说，过去这种水华每3到7年出现一次，但在过去的10年里，它们变得更加频繁。

While the bioluminescence is stunning to see, people should be cautious about getting in the water due to the bacteria feeding on the algae. (Photo: Bruce Anderson (University of Stellenbosch) / BMC Ecology [CC BY 2.0]/Flickr)

In addition to predicting future red tides, scientists are also asking why certain algae species go through boom periods where they form red tides, while others do not. Carter notes that only about five of the 50 or so species they see on a regular basis in San Diego form these massive blooms. "Why does only a small subset of species have the ability to out-compete all the others and dominate the community for weeks to a month at a time?" she asks.

除了预测未来的赤潮，科学家们还在问，为什么某些藻类会经历繁荣期，从而形成赤潮，而其他藻类则不会。卡特指出，他们在圣地亚哥经常看到的大约50个物种中，只有大约5个形成了这种大规模的藻华。她问道:“为什么只有一小部分物种有能力战胜所有其他物种，一次能在数周到一个月的时间里统治整个群落?”

There are other places you can experience similar phenomena. Heil says she has encountered bioluminescent algae in Moreton Bay, Australia, where it is caused by a dinoflagellate called Noctiluca scintillans. In Maine, a species called Alexandium fundyense causes glowing red tides, although it doesn't occur in the same concentrations as the ones in San Diego and Australia. "It just appears almost like stars twinkling in the sea rather than the water itself glowing," she says. One of the most famous places you can see glowing blooms is Bioluminescent Bay in Puerto Rico, where the glow is reportedly bright enough to read by.

在其他地方你也可以体验到类似的现象。黑尔说，她在澳大利亚的摩顿湾遇到过发光藻类，这种发光藻类是由一种名为夜光藻的鞭毛藻引起的。在缅因州，一种名为“方藻”的物种会引发赤潮，尽管它的浓度不像圣地亚哥和澳大利亚的那么高。她说:“这看起来就像星星在海里闪烁，而不是海水本身在发光。”你能看到发光的花朵的最著名的地方之一是波多黎各的生物发光湾，据报道那里的发光足以阅读。

If you do happen to encounter glowing waters, take a bit of caution. Although most are harmless, some of them can be slightly toxic if ingested. The algae in Moreton Bay, for instance, contain high levels of ammonia. The red tides in San Diego have been linked to increased levels of ear and sinus infections, although that could be more from the bacteria in the water that are feeding on the algae than from the algae itself.

如果你碰巧遇到了发光的水，要小心一点。虽然大多数都是无害的，但有些摄入后会有轻微的毒性。例如，摩顿湾的藻类含有大量的氨。圣地亚哥的赤潮与耳朵和鼻窦感染的增加有关，尽管这可能更多地是由于水中的细菌以藻类为食，而不是藻类本身。

But no matter where you encounter bioluminescent waters, take the time to stop and enjoy them. "They can be spectacular," Heil says.

但是无论你在哪里遇到发光的水，花点时间停下来享受它们。“它们可以很壮观，”黑尔说。