Drivers of Tropical Marine Diversity

Coral reefs are throbbing centers of life, shot through with riotous color. Innumerable creatures act and react in their sunlit shallows. But why? Why are coral reefs so gloriously, overwhelmingly diverse? What makes reefs the most biodiverse systems on the planet, though they cover less than 1% of its surface?

Today, we know precious little in answer to this question.

Historically, theoretical models of predation and competition were invoked to explain the high diversity of tropical marine systems, but in more recent years the picture has become more complex.



First, a quick definition of terms:

Nekton: Anyone who can swim against a current
Plankton: Anyone who can't

Many reef fish and invertebrates (including corals), hatch from tiny eggs, and exist briefly as planktonic larvae. They float on the surface of the sea in the soup of algae and invertebrates that drifts with the currents across the world's oceans. In this way, reef fish born on one side of the planet may be dispersed to the other, keeping genes mixing over distances that many adult fish couldn't possibly swim.

Thousands upon thousands of larvae are floating in the sea at this very moment. Most of them will die before ever settling on a reef and entering their adult life phase. With such high mortality rates, it seems unlikely that adult fish of any single guild would survive in high enough numbers to compete for the same resources. Hence, in this view, species richness is not dependent on competition, and traditional explanations of high biodiversity are thrown into question.



Dispersal is only one of many major factors that may contribute to reef fish diversity worldwide.

Unpredictable habitat availability has been posited as an alternative explanation for the high diversity of reef communities.

It is necessary to produce many offspring when habitat is limited and its availability is unpredictable, to ensure that at least a few of the large number of larvae attempting to settle will succeed by chance. The relative abundance of any species in a given habitat is therefore a result of chance colonization and extinction, and thus is expected to change over time.

Rather than relying on a single hypothesis to explain the structure of reef fish communities, ecologists and conservationists should look to multiple factors and interactions to explain the staggering diversity observed in these systems. It is important to consider both large- and small-scale processes, because adult reef fishes are generally not highly dispersive, but the pelagic larvae of some species do travel huge distances before settling on distant reefs. Further work is required to determine the subset of processes that determine the biodiversity of specific reefs or geographic areas, but this must occur on a case-by-case basis, implementing understanding of both global, and regional processes.Effective reserve design demands an accurate understanding of major factors contributing to marine biodiversity, making the understanding of reef community assembly a major conservation priority today.

A Crisis of Perspective

In Conservation: Tactics for a Constant Crisis, Michael Soulé briefly outlines seven factors as fundamental causes of environmental degradation, responsible for the increasingly rapid decline of species diversity worldwide. These "seven sources of biotic degradation" include exponential population growth, wealth disparities between developed and developing nations, an emphasis on short-term solutions rather than long-term thinking, anthropocentrism, and the prioritization of economic gain over environmental protection (the heart of problems of cultural transition and of economics).

 I agree that these seven factors do lead to environmental degradation, but would argue that anthropocentrism underpins Soulé's other six sources of degradation. Human- centered thinking is manifest as an emphasis on the success of the individual over the success of the community or health of the environment in The West. This short-sighted mentality has led to problematic population growth, poverty, and environmentally irresponsible economic development worldwide, as developing nations seek to create the same opportunities enjoyed by the citizens of developed societies- the majority of which subscribe to Western values.



Over 20 years after the publication of Soulé's piece, the field of Conservation Biology is still plagued by the problems he outlined in 1991. If anything, anthropocentrism has become more entrenched in the field since the early 90s, with the growing popularity of ecosystem services as a way to quantify the monetary value of conservation action. But approaching the environment as a personal resource is problematic, because the definition of "beneficial" is subjective. What one generation considers worthwhile, another may not. If we protect the environment from this standpoint, we ironically promote the fundamentally problematic thinking got us into this mess in the first place.   

Practice

Late November, and the weather is just turning cold.
Dusk comes early, blurring the edges of crisp, bright days. 

The new year is fast-approaching.
Can't believe how fast. A semester nearly gone.
Have I got my sea legs yet?
Yes and no.

 

These days I ask myself, how can I push past the ceiling of my current understanding? What improves the speed and efficiency of thought?
Practice.

Two Months In

It takes time.

Thoughts move tentatively this afternoon and sentences come in halting bursts. My mind is a fallen leaf, blown to and fro in the fickle breeze.

I am writing in the warm glow of a West Harlem coffee shop. Outside, great herds of dry leaves stampede down the street in gales of autumn wind. They move en masse, leaping and tumbling in the bow waves of passing cars. I imagine the thoughts slipping from my skull, smooth as a zipper, to join the fray. 

Two months in, the rhythms of graduate school have become familiar. It's a fluid dance between obligations: ever-juggling coursework and reading, thesis research and grant writing, exhaustion and drive. I often feel like an archaeologist, gently unearthing knowledge with the painstaking strokes of myriad small efforts.

As the season changes, I change too. Some husk of me peels away: an exoskeleton I've outgrown. Like thoughts and leaves, this too slips into the wind and blows away down the road.  

Reading: J.B MacKinnon's False Idyll, from Orion.

Listening: Royksopp- What else is there?

           Shakey Graves- Business Lunch

   Icky Blossoms- Cycle

Doing: I'm now also writing for State of The Planet. Huzzah! Click here to check out my stuff.

Can't Escape Popular Thought: The Intersection of Science and Government

Science, like all fields, is shaped by culture. Popular ideas may arise in political circles, through the writing of philosophers and academics, or elsewhere, to ultimately permeate many levels of society. The development of community ecology in The U.S.S.R. reflects the influence of social and political norms on the field. The modern trajectory of ecology is equally influenced by the times.

Douglas R. Weiner’s Community Ecology in Stalin’s Russia sheds light on the influence of popular thought (in this case political) on the development of a scientific field in the early 20^th-century Soviet Union. Before 1928, ecology gained momentum and prominence in Russian academia, in part because the country’s Bolshevik leadership supported the development of natural science as a route to technological development and economic progress. However, political upheaval from 1928 to 1932 led to new political views on the role of science in society. Science became subordinate to technology, and questions that had once been the purview of natural science were now answered by Marxist dogma. The politically popular push toward economic development now stood in direct opposition to the ecologists’ goals (namely, preservation of natural community assembly). Political leaders saw opposition as a threat to their absolute authority, and labeled ecologists traitors to the country. Research was curtailed as these scientists were denounced and priorities shifted toward agricultural development. 

Because political leaders determine the role of science in government and often fund a large portion of a country’s research projects, they can determine what questions are worth asking, and sway the popular perception of a field. As evinced by the relatively sudden vilification of Russian ecologists, the perception of a scientific field can change with political upheaval. Science does not exist in a vacuum, and to be successful research must be funded. Whether funding comes from a public or private source, the research must be deemed interesting and worthwhile to receive any kind of monetary support.

 In the US today, that trend is embodied by the National Science Foundation (NSF). From the NSF website: 

The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 "to promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense…" With an annual budget of about $7.0 billion (FY 2012), we are the funding source for approximately 20 percent of all federally supported basic research conducted by America's colleges and universities. (2013). 

 The National Science Foundation is a major source of funding for research in the US, and the work it prioritizes is research that promotes “national welfare”. However, the NSF also decides what “national welfare” means. Changes in the political and social climate can certainly influence the definition of that term. For instance, the current political administration is very interested in understanding anthropogenic influence on climate. As such, the NSF has interest in (and funding for) projects revolving around climate, but far less money for work in museum-based taxonomy. Some researchers would argue that building museum collections is equally important to understanding climate in our efforts to improve national welfare, but the popular trend in political discourse on the environment is climate-related.

On Wildness

Saturday: 

Salamanders are everywhere. They materialize from the undergrowth like so many mushrooms, red, orange, and speckled. I press my knees into the damp earth, and hunch down to watch a tiny amphibian cross a few feet of mossy terrain. A fallen branch is a sizable hurdle when you're only four inches long.
  Deep breath. In, out, in again. The air is clean and cold, rippling into my lungs like a northern river. I am caught in its current, thinking of time and of change on the wind. But here with filthy knees and dry elbows, I remember the child I once was, and feel the heady promise of challenges yet to come.

Tuesday:

School begins. Grad school begins. I'm en route to class on a campus at the heart of New York City, and amidst all the dissonance of urban life, I suddenly feel as I did in the forest. I'm new, with that same openness to the possibility in novelty. Perhaps it's the throngs of new faces or the anticipation of learning that incites this feeling; I'm not sure. But there is something common to the forest and to the city- something independent of the landscape, yet awakened by it.




In his essay, "Wilderness and the Multiple Layers of Environmental Thought", Yrjo Haila deconstructs the division of nature and culture. He argues that "the wild" as something separate from man cannot exist, because man has created the division. We have defined the borders of ourselves and our culture as distinct from the environment, while simultaneously constructing that culture and self-image through resources provided by the environment. Hell, we are the environment.


Seen through this lens, a city is no more "unnatural" than any forest, because a city is a product of human behavior and resource use. Whether humans choose to set aside large tracts of protected land (ie as national parks), or to build metropolises, those places will be under some form of human influence. Even very remote areas that aren't actively managed and have no indigenous population can't be considered "virgin" or "pristine" because they are indirectly affected by pollution, climate change, and anthropogenic modifications to biogeochemical cycling.

As an antidote to this false division of human society and nature at large, Haila presents an alternate definition of wildness, which Bennett [1994] argues is embodied by the work of Henry David Thoreau:   "Wildness is the remainder that always escapes taxonomies of flora and fauna or inventories of one's character or conscience; it is the difference of the woods that remains no matter how many times one walks in them."   Put succinctly, "Wildness is the..foreign dimension of anything."

And given that definition, it makes sense that the same fire could rise in me at the sight of a salamander in cool mountain air, and on a brisk morning in fall, at the start of a new journey in the heart of a very human city.

Extrapolating

Back in 2011, researchers from The University of Chicago and Chicago's Field Museum of Natural History (including Dr. Josh Drew and Dr. Mark Westneat), mounted an expedition to Papua New Guinea (PNG). Their primary goal was to quantify the diversity of fishes in Bootless Bay, a shallow harbor adjacent to the country's capital of Port Moresby. 

Ultimately, their research suggests that 949 fish species are present in the Bootless Bay area. Compared to other sites in PNG, this bay is relatively species-poor. Although limited sampling effort may skew the diversity estimates somewhat, anthropogenic factors (proximity to a major population center, habitat degradation, and exploitation) likely contribute to the low diversity estimates in this area. (See: Drew et al. BMC Ecology 2012, 12:15)

This summer, the majority of Hawkmoth posts have focused on fieldwork. The expedition to Fiji had similar goals to those in PNG. Both trips were intended to quantify reef fish diversity in areas subject to anthropogenic pressures, and both studies are relevant to questions on a much larger geographic scale, concerning broad patterns of diversity across the tropical Indo-Pacific. 

Geographically, Fiji sits on the periperhery of a region known as the Coral Triangle (outlined in the photo above, with Fiji identified to the east). Bounded by Indonesia, The Phillipines, and Papua New Guinea, the Coral Triangle is the heart of earth's marine biodiversity. This relatively small area boasts 50% of the planet's coral reefs (see: Coral Triangle Initiative). 

What we see is a steep drop in biodiversity from areas within the Coral Triangle to those on the periphery. Reefs in Indonesia and New Guinea have many more fish species than those in Fiji. But how did that happen? By quantifying the diversity of fishes in and around the Coral Triangle, we begin to trace the gradient of change in biodiversity here. Ultimately, this will help illuminate the how and why of reef community composition in the most diverse marine systems on earth.

Just Images

Pastels and warmer hues from the Netherlands, Germany, Hungary, France, and the UK.

[Almost] Free Friday

It's worth the trek. Yesterday I made my first foray into the mysterious north, riding the 1 through the upper reaches of Manhattan, across the Broadway Bridge to the end of the line.

I stepped off the metro at Van Cortland Park, onto an open air platform lofted above a tree-lined street. It's just across the river, but this feels nothing like the city. Gone is the amber glow of fluorescent lighting on underground station tiles, and gone is the cloying humidity of humans commuting, breathing and thinking silently, crammed together en masse.

Just outside of the station, free shuttles run to Wave Hill at ten past the hour. This public garden is perfect for a quiet morning walk ($4 admission for students). It exudes a sense of reserved elegance, passed on in the quiet of a sparrow alighting on an elm branch, and in the fickle grace of soft summer rain.

Walking across the lawns, I poked about in all variety of hidden reading nooks (those great last bastions of introversion), tucked here and there in the shrubbery. It's a rare and wonderful feeling to discover that even for a moment, a garden like this might share its secrets with you.

If you head back across the river, The Museum of Modern Art (MoMA), offers free admission on friday nights, starting at 4pm. The line is hellaciously long but moves quickly, and it's worth the wait. The exhibits are crowded, but the scene is friendly (populated mainly by starving student types). That's a $25 savings on admission, ($14 for students with ID), for which I'll gladly brave the crowds.

MoMA was great (and free!), but the highlight of this second Friday in August was a performance by Johanna Warren at The American Folk Art Museum. Admission here is always free (check out the Bill Traylor Exhibition on now), but on Fridays there is also live music and a wine bar (cash only, $5) from 5:30-7:30pm. Add one upstate songstress with a haunting voice and the weekend is effortlessly begun.

 

Happenings

Let the sorting commence! Fieldwork is finished for the summer, but we've only just begun. In Fiji last month, our lab collected 217 fish specimens which we preserved in formaldehyde, wrapped in linen, stuffed into buckets, and shipped back to the USA.

Now that we're back in New York, all 217 specimens have been sorted by species and origin. They've been labeled, preserved in ethanol, and stowed in large glass jars to line the shelves of the ichthyological collections of The American Museum of Natural History. There, they join fishes collected across the globe, in a massive repository of information on the world's biodiversity. These samples are now a physical resource, providing a snapshot of diversity and morphology for current and future biologists interested in the fishes of Fiji. 

Next up, we'll set to work extracting and analyzing DNA from the tissue samples we collected to paint a clearer picture of population-level interactions between Fijian coral reefs. Out of the field, there's still plenty to be done.