為什么南加州的潮汐是藍(lán)色的

為什么南加州的潮汐是藍(lán)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.

在封鎖期間，前往南加州海灘的游客并沒有那么多。但是，那些在夜晚冒險(xiǎn)外出的人卻看到了一幅奇異而美麗的景象:海浪撞擊，潮水涌來時(shí)，海水發(fā)出明亮的藍(lán)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.

這種不尋?，F(xiàn)象的原因是一種叫做扁舌藻的微生物。這種鞭毛藻(一種藻類)每隔幾年就會(huì)在圣地亞哥附近的水域繁殖一次，形成所謂的紅潮。

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.”

當(dāng)藻類在白天給水賦予一種渾濁的紅色時(shí)，夜晚是表演開始的時(shí)候。每次海藻被推擠的時(shí)候——無論是潮汐的移動(dòng)還是皮艇在水中移動(dòng)的碎片——它都會(huì)發(fā)出明亮的藍(lán)色生物熒光。這種發(fā)光是海藻受到驚嚇時(shí)體內(nèi)產(chǎn)生的化學(xué)物質(zhì)的結(jié)果。生物學(xué)家麗貝卡·赫爾姆最近在推特上把這種反應(yīng)描述為“明亮的小恐慌發(fā)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.

據(jù)斯克里普斯海洋學(xué)研究所稱，這一驚人的效果于本周早些時(shí)候出現(xiàn)，科學(xué)家們還不確定它會(huì)持續(xù)多長(zhǎng)時(shí)間。

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

據(jù)斯克里普斯說，過去這種水華每3到7年出現(xiàn)一次，但在過去的10年里，它們變得更加頻繁。

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.

除了預(yù)測(cè)未來的赤潮，科學(xué)家們還在問，為什么某些藻類會(huì)經(jīng)歷繁榮期，從而形成赤潮，而其他藻類則不會(huì)。卡特指出，他們?cè)谑サ貋喐缃?jīng)?？吹降拇蠹s50個(gè)物種中，只有大約5個(gè)形成了這種大規(guī)模的藻華。她問道:“為什么只有一小部分物種有能力戰(zhàn)勝所有其他物種，一次能在數(shù)周到一個(gè)月的時(shí)間里統(tǒng)治整個(gè)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體驗(yàn)到類似的現(xiàn)象。黑爾說，她在澳大利亞的摩頓灣遇到過發(fā)光藻類，這種發(fā)光藻類是由一種名為夜光藻的鞭毛藻引起的。在緬因州，一種名為“方藻”的物種會(huì)引發(fā)赤潮，盡管它的濃度不像圣地亞哥和澳大利亞的那么高。她說:“這看起來就像星星在海里閃爍，而不是海水本身在發(fā)光。”你能看到發(fā)光的花朵的最著名的地方之一是波多黎各的生物發(fā)光灣，據(jù)報(bào)道那里的發(fā)光足以閱讀。

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.

如果你碰巧遇到了發(fā)光的水，要小心一點(diǎn)。雖然大多數(shù)都是無害的，但有些攝入后會(huì)有輕微的毒性。例如，摩頓灣的藻類含有大量的氨。圣地亞哥的赤潮與耳朵和鼻竇感染的增加有關(guān)，盡管這可能更多地是由于水中的細(xì)菌以藻類為食，而不是藻類本身。

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

但是無論你在哪里遇到發(fā)光的水，花點(diǎn)時(shí)間停下來享受它們。“它們可以很壯觀，”黑爾說。