本篇文章共分 5 段，從杉葉蕨藻如何出現在地中海沿岸、生長情形、對原生物種的破壞、清除方式以及可能的未來發展，詳細說明外來物種對環境帶來的嚴重影響。

本篇考題英文原文與對應之中文翻譯整理如下。練習作答解題時若有對語意不清楚之處，請仔細查閱對照，以提升閱讀理解能力。

Invading Algae 入侵的海藻

1. 杉葉蕨藻入侵地中海

   Biological invasions by exotic species are an escalating threat to biodiversity around the globe. Invasive species can displace native ones and irrevocably alter ecosystems. Most imported species either die or have limited growth in their new home, but a small percentage of the newcomers are opportunists whose growth is dangerously out of control. The story of how Caulerpa taxifolia became famous as one of these species began in 1989, when Dr. Alexandre Meinesz, a marine biologist at the University of Nice in France, learned that this exotic alga, which is native to the Caribbean and other tropical seas, was thriving in the Mediterranean waters off the coast of Monaco. Upon investigation, Meinesz discovered that a mutant variety of C. taxifolia was dumped into the Mediterranean with other aquarium refuse by the prestigious Oceanographic Institute of Monaco. Eventually, the C. taxifolia was traced back to a stock developed at the Wilhelma Zoological and Botanical Gardens in Stuttgart, Germany. This stock of C. taxifolia had caught the attention of amateur and professional aquarists for its exceptional beauty and hardiness and had been widely distributed in public and private aquaria in the 1980s.

   外來物種的生物入侵對全球的生物多樣性是一個日益嚴重的威脅。入侵物種可以取代本地物種並不可逆轉地改變生態系統。大多數輸入的物種在他們的新家要麼死亡，要麼成長有限，但有一小部分新加入物種是機會主義者，其生長會造成危險的失控。杉葉蕨藻 (Caulerpa taxifolia) 作為此類物種之一而出名的故事始於 1989 年，當時法國尼斯大學的海洋生物學家 Alexandre Meinesz 博士瞭解到，這種原產於加勒比海和其他熱帶海洋的外來藻類在摩納哥海岸的地中海水域蓬勃發展。經過調查，Meinesz 發現一個變異品種的杉葉蕨藻被著名的摩納哥海洋研究所與其他水族箱垃圾一起傾倒在地中海。最終，杉葉蕨藻被追溯到德國斯圖加特的 Wilhelma 動植物園的一個種群。該種群的杉葉蕨藻因其異常的美麗與生長韌性而引起業餘和專業水族愛好者的注意，並在 20 世紀 80 年代廣泛分佈於公共和私人水族館。

2. 突變品種生長力驚人

   Instead of dying in the cold winter waters of the Mediterranean Sea as the tropical variety of C. taxifolia does, the mutant variety can withstand several months at temperatures that range between 10° and 13° C. In addition, the alga grows equally well on a variety of ocean substrates—sand, mud, or rocks—and from near the surface to depths of 50 meters. When temperatures exceed 18°C, the mutant Caulerpa grows at a remarkable rate, capable of elongating by 2 centimeters in a single day and forming a new frond every 2 days. A single square meter of seafloor can be matted with 5,500 leafy fronds. All of this growth is asexual. Unlike the tropical form, the mutated form of C. taxifolia produces only male gametes in the Mediterranean and thus replicates only by fragmentation. Just a small piece can regenerate and colonize an area. In fact, it is believed that fishing nets and boat anchors as well as the ripping action of storms have helped the alga spread to new areas.

   突變品種不會像熱帶品種杉葉蕨藻那樣死在地中海寒冷的冬季海水中，而是可以在 10° 到 13°C 的溫度下忍受幾個月。此外，該藻類在各種海洋底層—沙地、泥土或岩石—以及從近海面到 50 米深處都能同樣地順利生長。當溫度超過 18° C 時，突變體蕨藻以驚人的速度生長，能夠在一天內拉長 2 厘米，每 2 天形成一個新的葉狀體。一平方米的海底可以鋪滿 5500 片此種葉子。所有這些生長都是無性的。與熱帶形式不同，杉葉蕨藻的變異形式在地中海只產生雄性配子，因此只能通過碎片化複製。只要一小塊就可以再生並在一個地區定居。事實上，人們認為漁網和船錨以及暴風雨的撕裂作用協助該藻類傳播到新的地區。

3. 破壞生物多樣性

   With such a rapid rate of growth, the Mediterranean Caulerpa grows quickly over the sea bottom, blanketing all other sea life such as marine angiosperms, native algae, corals, and sea fans. lt cuts off vital essentials such as sunlight for photosynthesis and currents for filter feeding of nutrients. The area becomes a Caulerpa lawn while species diversity is lost. In addition, C. taxifolia is inedible to most marine herbivores because of the presence of toxic compounds, primarily caulerpenyne. With no predator to inhibit its phenomenal growth, the alga had encompassed the Mediterranean coasts of Monaco, France, Italy, Spain, and the Croatian coast on the Adriatic Sea covering 30,000 hectares by 2002. Caulerpa infestations have also been found in southern Australia, in estuaries near Sydney and Adelaide.

   由於生長速度如此之快，地中海蕨藻在海底迅速生長，覆蓋了所有其他海洋生物，如海洋被子植物、本地藻類、珊瑚和海扇。它切斷了重要的必需品，如用於光合作用的陽光和用於過濾營養物的水流。該地區變成了一個蕨藻草坪，但物種的多樣性卻消失了。此外，由於存在有毒的化合物，主要是 caulerpenyne，杉葉蕨藻對大多數海洋食草動物是不可食用的。由於沒有天敵來抑制其驚人的增長，到 2002 年時，該藻類已經覆蓋了摩納哥、法國、意大利、西班牙的地中海沿岸，以及亞得里亞海的克羅埃西亞海岸，面積達 30,000 公頃。在澳大利亞南部，在雪梨和阿德萊德附近的河口也發現了蕨藻的侵擾。

4. 清除不易

   Various methods have been tried to eradicate this deadly invader. Divers have been employed to rip the alga out by hand, but care must be taken because even a small fragment is capable of colonizing new areas. Black plastic tarps have been placed over the alga in an attempt to deprive it of life-giving sunlight. Chemicals such as copper, a conventional algicide, and toxic levels of salt have also been applied to Caulerpa fields. There has been limited success but only if the area of invasion is small.

   各種方法都已經被嘗試過來根除這個致命的入侵者。潛水員被僱用來用手清除海藻，但必須小心，因為即使是一個小碎片也能在新的地區定居。黑色塑料防水布被放置在海藻上，試圖剝奪它維持生命的陽光。化學物質，如銅這種傳統的除藻劑，和有毒的鹽類，也被應用於蕨藻生長地區。目前已經取得了部分的成功，但前提是遭入侵的區域很小。

5. 引入外力令人擔憂

   One hopeful avenue is biological control. In biological control, a disease or predator of the invasive organism is introduced and allowed to destroy it. In the native range of the tropical C. taxiolie, two species of sea slug are immune to its poisons and feed on the alga exclusively. They suck the cytoplasm out of the leaves and incorporate the algal chloroplasts, the part of the plant that contains green photosynthetic pigment, into their skin. The chloroplasts provide camouflage as the snails feed in the Caulerpa fields and, surprisingly, continue to photosynthesize, providing additional nutrition for the slugs. Dr. Meinesz is suggesting the importation of these slugs to the Mediterranean as the only way to eliminate the immense area that Caulerpa now covers. But many experts fear that another exotic importation may lead to more environmental damage.

   一個有希望的途徑是生物控制。在生物控制中，引入入侵生物的疾病或捕食者，並允許其破壞此入侵生物。在熱帶杉葉蕨藻的原生地，有兩種海蛞蝓對它的毒藥有免疫力，並且只吃這種藻類。他們從葉子中吸出細胞質，並將藻類的葉綠體（植物中含有綠色光合作用色素的部分）納入他們的皮膚。當蝸牛在蕨藻地裡進食時，這些葉綠體提供了偽裝，而且令人驚訝的是，它們繼續進行光合作用，為蛞蝓提供額外的營養。Meinesz 博士建議將這些蛞蝓輸入到地中海，作為消除蕨藻目前覆蓋巨大地區的唯一途徑。但許多專家擔心，另一種外來的輸入可能導致更多的環境破壞。