海洋國際都市，森林城市：生態(tài)，多樣化和文化

BBC系列紀錄片《地球脈動第二季》（Planet Earth II）第六集名為《城市》，它講述了生存在世界各地城市中心的動物們的生活。我們可以看到人類文明和其他動物文明的諸多碰撞，而這些動物或是面臨致命結(jié)果，或是成功地適應(yīng)城市環(huán)境。雖然通常是其他動物被迫適應(yīng)我們?nèi)祟悩?gòu)建的環(huán)境，但《城市》在結(jié)尾描述了一個振奮人心的愿景：我們可以通過建設(shè)高密度城市，為比城市中現(xiàn)有的更大的物種多樣性提供棲息地，從而實現(xiàn)對環(huán)境的適應(yīng)。

對有著強烈浪漫主義情感的人來說，這種構(gòu)建的生態(tài)系統(tǒng)的愿景可能會令其十分困擾。但我認為文獻和生物科學(xué)都可以為我們提供深刻見解，它們可以幫助我們走出關(guān)于自然的浪漫想法，并探索曾有著深不可測的深度或難以穿越的荒野的海洋都市或森林城市。

秘魯作家塞薩爾·卡爾沃（César Calvo）在其1981年首次出版的小說《InoMoxo的三個搭檔和亞馬孫河的其他巫醫(yī)們》（Las Tres Mitades de Ino Moxo y otros Brujos de la Amazonía）中，描述了故事講述者塞薩爾·索里亞諾（César Soriano）和巫醫(yī)們的一系列邂逅，這些巫醫(yī)都和傳奇的隱士Ino Moxo（即小說的中心人物）有一定的聯(lián)系。這些邂逅是索里亞諾穿越亞馬孫之旅的一部分，并最終帶他見到了Ino Moxo。卡爾沃的這部小說明確地表達了亞馬孫世界觀的方方面面——一種“深奧文化”——它們或能幫助我們從批判思維和現(xiàn)代生物科學(xué)的角度對生態(tài)進行全新的理解。

我想通過對海居藍藻細菌 “原綠球藻”的生態(tài)描述，引入對卡爾沃小說的闡述。海洋生物學(xué)家薩莉·奇澤姆（Sallie Chisholm）是“原綠球藻”研究領(lǐng)域的先驅(qū)。此處的想法是建立一種生態(tài)批判思維，這種思維不考慮浪漫主義和自然文學(xué)的傳統(tǒng)，并重視充分考慮二十一世紀微生物科學(xué)的細節(jié)問題。我的側(cè)重點是微生物，因為我認為我們能得出這樣一個合理的論證，即生態(tài)系統(tǒng)中發(fā)揮作用的、最不可或缺的有機體是微生物。更廣泛地講，所有的多細胞生物都是微生物生態(tài)學(xué)的產(chǎn)物。微生物還為我們提供了方法，以細致地研究構(gòu)成生態(tài)互聯(lián)性之網(wǎng)的有機體間的密切聯(lián)系。

一直以來，“生態(tài)（ecology）”一詞在人文學(xué)科領(lǐng)域的使用都是寬泛而含糊，為擺脫這一局面，我們需要查看其來源的具體的生態(tài)和有機體。就這一點而言，“原綠球藻”十分有用，因為它可被視為“闡述塑造微生物人口和生態(tài)系統(tǒng)之力量的模型系統(tǒng)”。我對塞薩爾·卡爾沃的小說的討論建立在這一觀點的基礎(chǔ)之上，即小說——特別是英美和歐洲傳統(tǒng)之外的那些作品——能夠為我們在復(fù)雜生態(tài)中設(shè)想自己的位置提供新的方法，且這些設(shè)想方法能和對生態(tài)過程的、以科學(xué)為基礎(chǔ)的理解聯(lián)系起來。

卡爾沃小說中的關(guān)鍵場景（就我們這個簡單討論而言）是故事講述者塞薩爾·索里亞諾和唐·哈維爾的邂逅，地點是位于秘魯西亞馬孫地區(qū)普卡爾帕Tariri酒店的酒吧。唐·哈維爾是一位巫醫(yī)，在死藤水的使用上經(jīng)驗豐富。死藤水是亞馬孫地區(qū)用來產(chǎn)生幻覺或作為一種亞馬孫植物醫(yī)學(xué)學(xué)科。在這次交流中，唐·哈維爾告訴索里亞諾：

“地球由從未被披露的美構(gòu)成，或是由被廣泛披露的美構(gòu)成，這點更糟糕。我來舉個例子，你應(yīng)該已經(jīng)看到Tariri酒店墻上的那些畫了。”

這些畫的設(shè)計由希皮博人完成，他們是史前時期諸多亞馬孫民族中的一個，但此時酒店墻上的畫只是復(fù)制，并沒有考慮其重要涵義。隨后，唐·哈維爾向索里亞諾解釋了自己是如何理解希皮博人的設(shè)計的。他說道，這些在我們看來可能僅僅是好看的圖畫，實際上是靈魂的肖像。

“要知道，有一根無形的繩子，你可能才開始看到、學(xué)習(xí)到，且通過普通肉身之眼是看不到的。我已經(jīng)看過了這面畫壁，但實際上我并不是在看這樣一面畫壁。很明顯，它是人的靈魂的模樣！”

索里亞諾回應(yīng)道：

“線型的肖像，”我自言自語道，“它們看起來就像城市地圖。”

“就是這樣！”他的聲音激動了起來，“對的！就是線型的肖像！并不是說它們看起來像城市地圖，而是它們本就是！沒錯，靈魂就是移動的城市！希皮博人的畫就是地圖，只不過是森林城市的地圖，有不可思議的河流橫貫其中，而不是街道，有迂回的曲徑迷宮貫穿其中，而不是嚴格管制的道路，有深谷、陰郁和沼澤做點綴，而不是冰冷的公園、電影院和林蔭大道！城市地圖，不是靈魂的肖像！位置變動了的房屋，就像叢林中的生活，就像阿薩寧卡族人的房屋，他們每年都要遷徙，燒掉自己的小屋和花園，讓一切歸于混沌，然后去到其他的地方，再開始建造庇護之所，播種、撒下生活的種子，隨后下一年又將一切焚毀，再去到別處重生！和我們一經(jīng)誕生即知道自己的未來、且受惰性和慣性束縛的城市不同，它們已掌握了自己的日子將會如何以及在前方等著它們的房屋和街道！我們的城市生來就是死的，就像是小樹的那些枝干，早在成熟前已滿是蠕蟲。”

我正是想將對森林城市的此類愿景——及可在希皮博藝術(shù)品中找到的它的基底結(jié)構(gòu)地圖——和已知的“原綠球藻”信息聯(lián)系在一起。此處，我將從標題為《原綠球藻：集體多樣性的結(jié)構(gòu)與功能》（Prochlorococcus: the structure and function of collective diversity）的文章出發(fā)。我想對二者做一個類比：森林城市之前被隱藏的、但可從唐·哈維爾所述之希皮博藝術(shù)品中顯現(xiàn)的結(jié)構(gòu)，和被視為海洋生態(tài)之地圖的、隱藏的，但通過對“原綠球藻”的了解（其分布、多樣性和與其他有機體的相互作用）可知的微生物多樣性的結(jié)構(gòu)。

薩莉·奇澤姆將“原綠球藻”及其他進行光合作用、并生產(chǎn)出地球50%的大氣氧氣含量的微生物稱為海洋的“隱形森林”。“原綠球藻”是“地球上最小且最豐富的光合作用有機體”。然而，盡管數(shù)量十分可觀，但由于體型微小，直到1985年它們才被發(fā)現(xiàn)。據(jù)估計，該屬內(nèi)的微生物產(chǎn)出了大氣中20%的氧氣。“原綠球藻”固定的碳含量大約相當(dāng)于全球農(nóng)作物的凈生產(chǎn)率。顯然，這一有機體在全球氣體和養(yǎng)分循環(huán)中發(fā)揮著重要作用。

單個的“原綠球藻”細胞不僅個頭微小，還有很小的基因組，有些分離菌只有1700個基因。這是目前已知的所有從日照中獲取能量的有機體中基因組最少的，比人類基因組要少約12倍。但這并不是全部，如果估算已經(jīng)適應(yīng)了不同海洋生態(tài)位的“原綠球藻”的各類菌株上的基因總數(shù)，我們會得到一個數(shù)字，大致為84000個基因。這個泛基因組約是人類基因組的四倍。

文章的副標題，“集體多樣性的結(jié)構(gòu)與功能（the structure and function of collective diversity）”，正是我得出這些數(shù)字的來源，它表明考慮“原綠球藻”的泛基因組（即不同菌株所有基因的總和）是很有道理的，因為這種集體多樣性是有機體在變化的生態(tài)中成功存活的關(guān)鍵。但由于病毒基因可在菌株間移動，以至于薩莉·奇澤姆指出一提到“原綠球藻”，人們可能就會想象海洋中居住著擁有分解的基因信息的生物，那么這樣考慮也是說得通的。

稍后我們再看來看這部分的描述，但首先我想概述下推動“原綠球藻”基因多樣性的一些動力。從最寬泛的水平看，菌株可分為適應(yīng)高光照強度和低光照強度的種類。低光照強度的菌株能在比其他任何光合有機體都深的深度，進行光合作用，在海平面以下約200米的位置。低光照強度的菌株中有更大的基因多樣性。關(guān)于這點，有一個解釋是：受天氣和波浪影響，表層水不斷地被混合，就養(yǎng)分和溫度而言，生成了一個相對比較同質(zhì)化的環(huán)境。但是，越來越深地朝著海底探索時，我們發(fā)現(xiàn)光照、溫度、壓力和養(yǎng)分都有了穩(wěn)定的梯度。正是這些梯度的穩(wěn)定性，使“原綠球藻”菌株的多樣化成為了可能，這些菌株在水體的不同梯度中占據(jù)著具體位置。

此時，我們開始稍稍了解我稱為“原綠球藻”海洋國際都市的概念。深海中的穩(wěn)定梯度是構(gòu)成這一生物的多樣性的城市結(jié)構(gòu)的動脈路徑。追蹤這些路徑，我們就能夠創(chuàng)建這些微生物城市的地圖。

這一結(jié)構(gòu)多樣性中的另一個因素是病毒的角色，它們既可以作為產(chǎn)生新的耐藥菌株的進化壓力，也可以成為菌株間遺傳信息的載體。基因以傳病媒介在菌株間運動是運動中的微生物城市的動力的一部分。在海洋的任意指定深度，我們還在構(gòu)成成型群落的“原綠球藻”細胞中發(fā)現(xiàn)了微觀多樣性。甚至是在通常被認為是單個菌株的克隆體中，也發(fā)現(xiàn)了基因?qū)用娴亩鄻有浴：暧^和微觀層面的多樣性都給“原綠球藻”提供了遺傳信息庫，從而快速適應(yīng)所處環(huán)境的變化。毫無疑問，這對它作為有機體的成功一直是十分重要的。

此處我一直在討論的文章的幾位作者認為，“原綠球藻”可被視為“多種細胞的聯(lián)合”：

“諸多生物群的大合集，每一個都展現(xiàn)了對特定環(huán)境變量的適應(yīng)并代表了反映重大生態(tài)位維度的等位基因（基因的變體形式）的組合配置。”

“原綠球藻”是一個典型群落，能夠幫助我們在實際生態(tài)環(huán)境中為生態(tài)批評建立牢固理論基礎(chǔ)的諸多群落之一。盡管沒有詳細地探索“原綠球藻”和其他有機體（包括助其生長的其他細菌）的關(guān)系，我們希望可以開始欣賞“原綠球藻”海洋國際都市的卓越結(jié)構(gòu)。

通過文獻和生物科學(xué)，從而學(xué)著去感知之前隱形的結(jié)構(gòu)——森林城市或海洋國際都市，這樣可以將我們和構(gòu)成我們的世界的非人類文明帶入到更為親密的倫理關(guān)系。我認為保護、研究和學(xué)著去感知之前隱形的當(dāng)下非人類城市（雖然只是通過生物學(xué)和文獻），每一點看起來都和建造高密度的、可支撐最大可能的生活多樣性的人類城市同等重要，并想要通過這個觀點的提出回到我一開始提到的《地球脈動第二季》第六集上。

參考文獻

Steven J. Biller et. Al. ‘Prochlorococcus: the structure and function of collective diversity’, Nature Reviews Microbiology, volume 13, issue 1, January 2015.

César Calvo, Las Tres Mitades de Ino Moxo y otros Brujos de la Amazonía, Proceso Editores y Editorial Gráfica LABOR,1981.

Sallie Chisholm, Invisible Forest: Microbes of the Sea, MIT TechTV, online video, recorded 15 November 2006, accessed 4 April 2017.

Sallie Chisholm, Carl Zimmer, ‘Harvesting the Sun’, Meet the Scientist, Episode 41, 6 January 2010, accessed 4 April 2017.

Ocean Cosmopolis, Forest City: ecology, diversity, culture

Ben Denham

‘Cities’, episode six of the BBC documentary series Planet Earth II, looks at the lives of animals living in urban centres all over the world. We see a variety of encounters between human and other animal cultures; sometimes with deadly consequences for the other animals and sometimes stories of successful animal adaptation to the urban environment. While it is generally the other animals that are being forced to adapt to our built environments ‘Cities’ ends with a stirring vision of how we might adapt by building high density cities that that are designed to provide habitat for a far greater diversity of species than those that currently live in our cities. 

This vision of a constructed ecosystem may be troubling to those of us with strong Romantic sensibilities but I’d like to argue that both literature and the biological sciences can offer us insights that might help us to move beyond romantic ideas about nature and see an ocean cosmopolis or a forest city where once we saw unfathomable depths or impenetrable wilderness.

In his novel Las Tres Mitades de Ino Moxo y otros Brujos de la Amazonía (The Three Halves of Ino Moxo and other Witch Doctors of the Amazon), first published in 1981, Peruvian author César Calvo describes a series of encounters between his narrator, César Soriano, and witch doctors who all have some association with Ino Moxo, the figure at the centre of the novel. These encounters are part of a journey through the Amazon that leads to César Soriano’s meeting with Ino Moxo. Calvo’s novel articulates aspects of an Amazonian cosmovision — a kind of deep culture — that might help us to come to new understandings of ecology in relation to critical thought and the contemporary biological sciences. 

I want to bring Calvo’s novel into conversation with an ecological account of the ocean dwelling cyanobacteria Prochlorococcus whose study was pioneered by biological oceanographer Sallie Chisholm. The idea here is to model a kind of eco-critical thought that bypasses the Romantic and nature writing traditions and takes seriously the problem of thinking through the details twenty-first century microbial science. I’m focusing on microbes because I think we can make a reasonable argument that the most indispensable organisms in ecosystem functioning are microbial. More broadly all multicellular life is the product of microbial ecologies. Microbes also provide us with the means to study in detail the close associations between organisms that weave the webs of ecological interconnectedness. 

To move beyond a general and vague sense of how the term ecology has been used in the humanities we need to look at specific ecologies and the organisms that produce them. Prochlorococcus is useful in this regard because it can be thought of as a ‘model system for elucidating the forces that shape microbial populations and ecosystems’. My discussion of César Calvo’s novel is premised on the idea that fiction — particularly from beyond the Anglo and European traditions — can give us new ways of imagining our place in complex ecologies, ways of imagining that can be related to science-based understandings of ecological processes. 

The key scene from Calvo’s novel — for the purposes of this brief discussion — is an encounter between the narrator César Soriano and Don Javier, in the bar of the Hotel Tariri, Pucallpa, a city in the western Amazon region of Peru. Don Javier is a witch doctor who is experienced in the use of ayahuasca; a psychedelic brew that is used in the Amazon for both the visionary experiences it provides and as part of the discipline of Amazonian plant medicine. During this encounter Don Javier tells the narrator that: 

This earth is made of beauties that have never been told, or that has been told badly, which is worse. I’ll give you an example; you’ve seen those drawings on the walls of Hotel Tariri.

The design of these drawings was produced by the Shipibo people — one of the many prehispanic Amazonian nations — but here on the walls of the Hotel it has been copied without regard to its significance. Don Javier then explains to César Soriano how he understands the Shipibo designs. He tells Soriano that what might appear to us to be merely pretty pictures are actually portraits of souls. 

There’s an invisible thread, you know, that you might start to see, that you learn, and that you don’t see with the eyes of your material body. I’ve looked at this painted wall and in reality I’m not looking at a painted wall. There, clearly, is the face of a man’s soul! 

Soriano responds:

Linear portraits, I said to myself, they look like maps of cities.

Exactly! his voice excited. That’s right linear portraits! It’s not that they look like maps of cities, that’s what they are! Yes, souls are cities in movement! The Shipibo drawings are maps, but of forest cities, cut through with impossible rivers, not avenues, labyrinths of winding paths, not regimented streets, lovers, ravines, sadness and swamps instead of cold parks, cinemas and boulevards! Maps of cities, rather than portraits of souls! Houses that change place, just like the days of life in the jungle, just like the houses of the Ashaninka who move every year and burn their huts and their gardens and return everything to the tangle, and go somewhere else and start again building their shelter, sowing their seeds, their life, before burning it all again the following year and going elsewhere to be reborn! Not like our cities that are born and already know their future, chained to rust and habit, they already know how their days will be and the houses and streets that await them! Our cities are born dead, they look like those skeletons of young trees, full of worms before they mature.

It is this vision of the forest city — and the maps of its underlying structure that we might find in the Shipibo artwork — that I’d like to relate to what we know about Prochlorococcus. Here I’m working from a review titled ‘Prochlorococcus: the structure and function of collective diversity’. I’d like to draw an analogy between the previously hidden structures of the forest city, that can emerge from the Shipibo artwork that Don Javier describes, and the hidden structures of microbial diversity — what we might think of as maps of ocean ecologies — that emerge through our knowledge of Prochlorococcus, its distribution, diversity, and interactions with other organisms.

Sallie Chisholm has called Prochlorococcus and the other photosynthetic microbes that produce 50% of the planet’s atmospheric oxygen the ‘invisible forests’ of the ocean. Prochlorococcus is ‘the smallest and most abundant photosynthetic organism on Earth’. Despite its abundance and because of its diminutive size it was only discovered in 1985. It is estimated that this genus produces 20% of the oxygen in our atmosphere. The amount of carbon fixed by Prochlorococcus is roughly equivalent to the net global productivity of our agricultural crops. Clearly this organism plays a major role in global gas and nutrient cycles. 

Individual Prochlorococcus cells are both physically small and have small genomes, with some isolates having only 1 700 genes. From what is known this is the smallest genome of all organisms that get their energy from the sunlight. It is about 12 times smaller than the human genome. But this is only part of the story. If we estimate the total number of genes from all the various strains of Prochlorococcus that have adapted to different niches in our oceans we come to a figure of roughly 84 000 genes. This pan-genome is about 4 times the size of the human genome. 

The subtitle of the review that I’m getting these numbers from — ‘the structure and function of collective diversity’ — suggests that it makes sense to think about the Prochlorococcus pan-genome — that is, the sum of all genes across different strains — because this collective diversity is central to the success of the organism in varying ecologies. But it also makes sense to think this way because viruses move can genes between strains in a way that has led Sallie Chisholm to suggest that when it comes to Prochlorococcus we might think of the ocean as being populated by dissolved genetic information. 

We’ll come back to this description in a moment but first I want to outline some of the forces driving genetic diversity in Prochlorococcus. At the broadest level strains are categorised into those that are adapted to high and low light levels. The low light strains can photosynthesise at greater depths than any other photosynthetic organism; down to about 200m below the ocean surface.  There is greater genetic diversity among low light adapted strains. One explanation for this is that surface waters are constantly being mixed by weather and waves leading to a relatively homogenous environment in relation to both nutrients and temperature. However, as we go deeper into the ocean we find stable gradients of light, temperature, pressure, and nutrients. It is the stability of these gradients that allow for the diversification of the Prochlorococcus strains that occupy specific places along these various gradients in the water column. 

Here we start to get a hint of what I’m calling the Prochlorococcus ocean cosmopolis. The stable gradients of the deeper ocean are the arterial paths that make up the cosmopolitan structure of this organism’s diversity. Tracing these paths will allow us to create maps of these microbial cities. 

Another factor in this structure diversity is the role of viruses as both an evolutionary pressure that produces new resistant strains and as carriers of genetic information between strains. This movement of genes between strains on viral vectors is part of the dynamics a microbial city in movement. At any given depth in the ocean we also find microdiversity in the Prochlorococcus cells that make up stable communities. Even among what would generally be considered clones of a single strain of we find diversity at a genetic level. Diversity at both the macro and micro levels gives Prochlorococcus the genetic repertoire to adapt quickly to changes in its environment and has undoubtedly been important to its success as an organism. 

The authors of the review that I’ve been discussing here suggest that Prochlorococcus can be viewed as ‘a(chǎn) federation of diverse cells’:

a large collections of many groups, each of which exhibits different adaptations to specific environmental variables and represents combinatorial arrangements of alleles [variant forms of a gene] that reflect important niche dimensions. 

Prochlorococcus is a model community, one of many that might help us to ground ecocriticism more firmly in actual ecologies. Even without going into the detail of the relationships between Prochlorococcus and other organisms — including the other bacteria that help its growth — we can hopefully start to appreciate the remarkable structure of the Prochlorococcus ocean cosmopolis.

Thinking through literature and the biological sciences to learn to perceive previously invisible structures — a forest city or an ocean cosmopolis — can bring us into more intimate and ethical relationships with the non-human cultures that structure our world. To return to the episode of Planet Earth II that I began with I’d like to end by suggesting that protecting, studying, and learning to perceive the previously invisible non-human cities of the present — though biology and literature — seems every bit as important as building high density human cities that can support the greatest possible diversity of life.

References

Steven J. Biller et. Al. ‘Prochlorococcus: the structure and function of collective diversity’, Nature Reviews Microbiology, volume 13, issue 1, January 2015.

César Calvo, Las Tres Mitades de Ino Moxo y otros Brujos de la Amazonía, Proceso Editores y Editorial Gráfica LABOR, 1981.

Sallie Chisholm, Invisible Forest: Microbes of the Sea, MIT TechTV, online video, recorded 15 November 2006, accessed 4 April 2017. 

Sallie Chisholm, Carl Zimmer, ‘Harvesting the Sun’, Meet the Scientist, Episode 41, 6 January 2010, accessed 4 April 2017.